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  • Polymer and Materials Science  (2,626)
  • 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous
  • 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
  • 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
  • Wiley-Blackwell  (2,633)
  • American Geophysical Union  (16)
  • Istituto Nazionale di Geofisica e Vulcanologia  (3)
  • Springer  (3)
  • Agu  (2)
  • Elsevier B.V.  (2)
  • COPERNICUS GESELLSCHAFT MBH, BAHNHOFSALLEE 1E, GOTTINGEN, 37081, GERMANY
  • Springer Berlin Heidelberg
  • 2010-2014  (34)
  • 1995-1999
  • 1975-1979  (2,626)
  • 1950-1954
  • 2013  (13)
  • 2010  (21)
  • 1976  (2,626)
Collection
Keywords
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Years
  • 2010-2014  (34)
  • 1995-1999
  • 1975-1979  (2,626)
  • 1950-1954
Year
  • 1
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    Towards an automatic monitoring system of infrasonic events at Mt. Etna: strategies for source location and modelling (2010)
    Springer
    Details
    Publication Date: 2020-11-16
    Description: Active volcanoes characterized by open conduit conditions generate sonic and infrasonic signals, whose investigation provides useful information for both monitoring purposes and studying the dynamics of explosive processes. In this work, we discuss the automatic procedures implemented for a real-time application to the data acquired by a permanent network of five infrasound stations running at Mt. Etna volcano. The infrasound signals at Mt. Etna consist in amplitude transients, called infrasound events. The adopted procedure uses a multi-algorithm approach for event detection, counting, characterization and location. It is designed for an efficient and accurate processing of infrasound records provided by single-site and array stations. Moreover, the source mechanism of these events can be investigated off-line or in near real-time by using three different models: i) Strombolian bubble; ii) resonating conduit and iii) Helmholtz resonator. The infrasound waveforms allow us to choose the most suitable model, to get quantitative information about the source and to follow the time evolution of the source parameters.
    Description: Published
    Description: 1215–1231
    Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio
    Description: JCR Journal
    Description: open
    Keywords: infrasound ; monitoring system ; Mt. Etna ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 2
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    Synchronization between tides and sustained oscillations of the hydrothermal system of Campi Flegrei (Italy) (2013)
    American Geophysical Union
    Details
    Publication Date: 2020-12-15
    Description: Long continuous seismic data recorded at five broadband seismic stations during 2006 at Campi Flegrei caldera have been analyzed. Introducing a coarse-grained method, we evaluate the time evolution of amplitude and polarization of the seismic noise in the frequency band common to long-period events. The series are modulated on tidal time scales: the root-mean square is basically dominated by solar contribution, while the azimuth of the polarization vector shows lunar diurnal and semidiurnal constituents. In addition, we find that in the frequency band common to long-period events the azimuths are polarized toward a specific area, suggesting that these persistent oscillations can be induced by the activity of the shallow geothermal reservoir.
    Description: Published
    Description: 2628–2637
    Description: JCR Journal
    Description: restricted
    Keywords: sustained hydrothermal tremor ; Campi Flegrei Caldera ; polarization analysis ; tidal modulation ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Geological and geophysical investigation of Kamil crater, Egypt (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2020-12-21
    Description: We detail the Kamil crater (Egypt) structure and refine the impact scenario, based on the geological and geophysical data collected during our first expedition in February 2010. Kamil Crater is a model for terrestrial small-scale hypervelocity impact craters. It is an exceptionally well-preserved, simple crater with a diameter of 45 m, depth of 10 m, and rayed pattern of bright ejecta. It occurs in a simple geological context: flat, rocky desert surface, and target rocks comprising subhorizontally layered sandstones. The high depth-to-diameter ratio of the transient crater, its concave, yet asymmetric, bottom, and the fact that Kamil Crater is not part of a crater field confirm that it formed by the impact of a single iron mass (or a tight cluster of fragments) that fragmented upon hypervelocity impact with the ground. The circular crater shape and asymmetries in ejecta and shrapnel distributions coherently indicate a direction of incidence from the NW and an impact angle of approximately 30 to 45 . Newly identified asymmetries, including the off-center bottom of the transient crater floor downrange, maximum overturning of target rocks along the impact direction, and lower crater rim elevation downrange, may be diagnostic of oblique impacts in well-preserved craters. Geomagnetic data reveal no buried individual impactor masses 〉100 kg and suggest that the total mass of the buried shrapnel 〉100 g is approximately 1050–1700 kg. Based on this mass value plus that of shrapnel 〉10 g identified earlier on the surface during systematic search, the new estimate of the minimum projectile mass is approximately 5 t.
    Description: Published
    Description: 1842–1868
    Description: 3.8. Geofisica per l'ambiente
    Description: JCR Journal
    Description: restricted
    Keywords: Impact craters ; geophysical survey ; iron meteorite ; impact scenario ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous ; 04. Solid Earth::04.02. Exploration geophysics::04.02.07. Instruments and techniques ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    Kinematics and Source Zone Properties of the 2004 Sumatra-Andaman Earthquake and Tsunami: Nonlinear Joint Inversion of Tide-Gage, Satellite Altimetry and GPS data (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We (re)analyzed the source of the 26 December 2004 Sumatra-Andaman earthquake and tsunami through a nonlinear joint inversion of an in-homogeneous dataset made up of tide-gages, satellite altimetry, and far-field GPS recordings. The purpose is two-fold: (1) the retrieval of the main kinematics rupture parameters (slip, rake, rupture velocity); (2) the inference of the rigidity of the source zone. We independently estimate the slip from tsunami data and the seismic moment from geodetic data, so to derive the rigidity. Our results confirm that the source of the 2004 Sumatra-Andaman earthquake has a complex geometry, constituted by three main slip patches, with slip peaking at ~30 meters in the Southern part of the source. The rake direction rotates counter-clockwise at North, according to the direction of convergence along the trench. The rupture velocity is higher in the deeper than in the shallower part of the source, consistently with the expected increase of rigidity with depth. It is also lower in the Northern part, consistently with known variations of the incoming plate properties and shear velocity. Our model features a rigidity (20-30 GPa), that is lower than PREM average for the seismogenic volume [Dziewonski and Anderson, 1981]. The source rigidity is one of the factors controlling the tsunamigenesis: for a given seismic moment, the lower the rigidity, the higher the induced seafloor displacement. The general consistence between our source model and previous studies supports the effectiveness of our approach to the joint inversion of geodetic and tsunami data for the rigidity estimation.
    Description: In press
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: open
    Keywords: Source process ; Sumatra ; Tsunami ; joint inversion ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    On the transient behavior of frictional melt during seismic slip (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: In a recent work on the problem of sliding surfaces under the presence of frictional melt (applying in particular to earthquake fault dynamics), we derived from first principles an expression for the steady state friction compatible with experimental observations. Building on the expressions of heat and mass balance obtained in the above study for this particular case of Stefan problem (phase transition with a migrating boundary) we propose here an extension providing the full time-dependent solution (including the weakening transient after pervasive melting has started, the effect of eventual steps in velocity and the final decelerating phase). A system of coupled equations is derived and solved numerically. The resulting transient friction and wear evolution yield a satisfactory fit (1) with experiments performed under variable sliding velocities (0.9-2 m/s) and different normal stresses (0.5-20 MPa) for various rock types and (2) with estimates of slip weakening obtained from observations on ancient seismogenic faults that host pseudotachylite (solidified melt). The model allows to extrapolate the experimentally observed frictional behavior to large normal stresses representative of the seismogenic Earth crust (up to 200 MPa), high slip rates (up to 9 m/s) and cases where melt extrusion is negligible. Though weakening distance and peak stress vary widely, the net breakdown energy appears to be essentially independent of either slip velocity and normal stress. In addition, the response to earthquake-like slip can be simulated, showing a rapid friction recovery when slip rate drops. We discuss the properties of energy dissipation, transient duration, velocity weakening, restrengthening in the decelerating final slip phase and the implications for earthquake source dynamics.
    Description: S.N. and G.D.T. were supported by a European Research Council Starting Grant Project (acronym USEMS) and by a Progetti di Eccellenza Fondazione Cassa di Risparmio di Padova e Rovigo. We are grateful to Nick Beeler (and to an anonymous referee) for their constructive reviews and their help to improve the clarity of the manuscript.
    Description: Published
    Description: B10301
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: open
    Keywords: Friction ; Melt ; Earthquake dynamics ; fault mechanics ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Energy radiation from intermediate to large magnitude earthquakes: implications for dynamic fault weakening (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The amount of energy radiated from an earthquake can be measured using recent methods based on earthquake coda signals and spectral ratios. Such methods are not altered by either site or directivity effects, with the advantage of a greatly improved accuracy. Several studies of earthquake sequences based on the above measurements showed evidence of a breakdown in self-similarity in the moment to energy relation. Radiated energy can be also used as a gauge to estimate the average dynamic stress drop on the fault. Here we compute the dynamic stress drop, infer the co-seismic friction and estimate the co-seismic heating resulting from the frictional work during events from different main shock-aftershock earthquake sequences. We relate the dynamic friction to the maximum temperature rise estimated on the faults for each earthquake. Our results are strongly indicative that a thermally triggered dynamic frictional weakening is present, responsible for the breakdown in self-similarity. These observations from seismic data are compatible with recent laboratory evidence of thermal weakening in rock friction under seismic slip-rates, associated to various physical processes such as melting, decarbonation or dehydration.
    Description: Kevin Mayeda was supported under Weston Geophysical subcontract No. GC19762NGD and AFRL contract No. FA8718-06-C-0024. Work by L. Malagnini was performed under the auspices of the Dipartimento della Protezione Civile, under contract S3 – INGV-DPC (2007-2009), project: “Valutazione rapida dei parametri e degli effetti dei forti terremoti in Italia e nel Mediterraneo”.
    Description: Published
    Description: B06319
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: open
    Keywords: earthquake radiation ; coda ; friction ; self-similarity ; dynamic weakening ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Evolution of an active lava flow field using a multitemporal LIDAR acquisition (2010)
    American Geophysical Union
    Details
    Publication Date: 2012-02-03
    Description: Application of light detection and ranging (LIDAR) technology in volcanology has 7 developed rapidly over the past few years, being extremely useful for the generation 8 of high‐spatial‐resolution digital elevation models and for mapping eruption products. 9 However, LIDAR can also be used to yield detailed information about the dynamics of 10 lava movement, emplacement processes occuring across an active lava flow field, and the 11 volumes involved. Here we present the results of a multitemporal airborne LIDAR survey 12 flown to acquire data for an active flow field separated by time intervals ranging from 13 15 min to 25 h. Overflights were carried out over 2 d during the 2006 eruption of Mt. Etna, 14 Italy, coincident with lava emission from three ephemeral vent zones to feed lava flow in 15 six channels. In total 53 LIDAR images were collected, allowing us to track the volumetric 16 evolution of the entire flow field with temporal resolutions as low as ∼15 min and at a 17 spatial resolution of 〈1 m. This, together with accurate correction for systematic errors, 18 finely tuned DEM‐to‐DEM coregistration and an accurate residual error assessment, 19 permitted the quantification of the volumetric changes occuring across the flow field. We 20 record a characteristic flow emplacement mode, whereby flow front advance and channel 21 construction is fed by a series of volume pulses from the master vent. Volume pulses 22 have a characteristic morphology represented by a wave that moves down the channel 23 modifying existing channel‐levee constructs across the proximal‐medial zone and building 24 new ones in the distal zone. Our high‐resolution multitemporal LIDAR‐derived DEMs 25 allow calculation of the time‐averaged discharge rates associated with such a pulsed flow 26 emplacement regime, with errors under 1% for daily averaged values.
    Description: This work was partially funded by the Italian 930 Dipartimento della Protezione Civile in the frame of the 2007–2009 Agree- 931 ment with Istituto Nazionale di Geofisica e Vulcanologia–INGV. A.F. 932 benefited from the MIUR‐FIRB project “Piattaforma di ricerca multi‐disci- 933 plinare su terremoti e vulcani (AIRPLANE)” n. RBPR05B2ZJ. S.T. 934 benefited from the project FIRB “Sviluppo di nuove tecnologie per la prote- 935 zione e difesa del territorio dai rischi naturali (FUMO)” funded by the Italian 936 Ministero dell’Istruzione, dell’Università e della Ricerca.
    Description: Published
    Description: B11203
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 1.10. TTC - Telerilevamento
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: LIDAR ; lava flow ; Etna ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Insights into fluid circulation across the Pernicana Fault (Mt. Etna, Italy) and implications for flank instability (2010)
    Elsevier B.V.
    Details
    Publication Date: 2017-04-04
    Description: We conducted geophysical–geochemical measurements on a ∼2 kmN–S profile cutting across the Pernicana Fault, one of the most active tectonic features on the NE flank of Mt. Etna. The profile passes from the unstable E flank of the volcano (to the south) to the stable N flank and significant fluctuations in electrical resistivity, self-potential, and soil gas emissions (CO2, Rn and Th) are found. The detailed multidisciplinary analysis reveals a complex interplay between the structural setting, uprising hydrothermal fluids, meteoric fluids percolating downwards, ground permeability, and surface topography. In particular, the recovered fluid circulation model highlights that the southern sector is heavily fractured and faulted, allowing the formation of convective hydrothermal cells. Although the existence of a hydrothermal system in a volcanic area does not surprise, these results have great implications in terms of flank dynamics at Mt. Etna. Indeed, the hydrothermal activity, interacting with the Pernicana Fault activity, could enhance the flank instability. Our approach should be further extended along the full extent of the boundary between the stable and unstable sectors of Etna for a better evaluation of the geohazard in this active tectonic area.
    Description: This work was partly financed by the DPC-INGV FLANK and LAVA Projects.
    Description: Published
    Description: 137–142
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi
    Description: JCR Journal
    Description: reserved
    Keywords: Pernicana Fault ; fluid circulation ; structural geology ; Etna ; magnetic ; electrical methods ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous ; 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration ; 04. Solid Earth::04.02. Exploration geophysics::04.02.04. Magnetic and electrical methods ; 04. Solid Earth::04.02. Exploration geophysics::04.02.05. Downhole, radioactivity, remote sensing, and other methods ; 04. Solid Earth::04.02. Exploration geophysics::04.02.07. Instruments and techniques ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones ; 04. Solid Earth::04.04. Geology::04.04.07. Rock geochemistry ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism ; 04. Solid Earth::04.08. Volcanology::04.08.04. Thermodynamics ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Predicting the impact of lava flows at Mount Etna, Italy (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Forecasting the time, nature, and impact of future eruptions is difficult at volcanoes such as Mount Etna, in Italy, where eruptions occur from the summit and on the flanks, affecting areas distant from each other. Nonetheless, the identification and quantification of areas at risk from new eruptions are fundamental for mitigating potential human casualties and material damage. Here, we present new results from the application of a methodology to define flexible high‐resolution lava invasion susceptibility maps based on a reliable computational model for simulating lava flows at Etna and on a validation procedure for assessing the correctness of susceptibility mapping in the study area. Furthermore, specific scenarios can be extracted at any time from the simulation database, for land use and civil defense planning in the long term, to quantify, in real time, the impact of an imminent eruption, and to assess the efficiency of protective measures.
    Description: This work was sponsored by the Italian Ministry for Education, University and Research, FIRB project RBAU01RMZ4 “Lava flow simulations by Cellular Automata,” and by the National Civil Defense Department and INGV (National Institute of Geophysics and Volcanology), project V3_6/09 “V3_6 – Etna.”
    Description: Published
    Description: B04203
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: 4.4. Scenari e mitigazione del rischio ambientale
    Description: JCR Journal
    Description: reserved
    Keywords: lava flows ; volcanic hazard ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.03. Geomorphology ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.01. Computational geophysics::05.01.02. Cellular automata, fuzzy logic, genetic alghoritms, neural networks ; 05. General::05.01. Computational geophysics::05.01.05. Algorithms and implementation ; 05. General::05.02. Data dissemination::05.02.99. General or miscellaneous ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions ; 05. General::05.08. Risk::05.08.99. General or miscellaneous ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    Patterns in the recent 2007–2008 activity of Mount Etna volcano investigated by integrated geophysical and geochemical observations (2010)
    American Geophysical Union
    Details
    Publication Date: 2012-02-03
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union
    Description: Seismic, deformation, and volcanic gas observations offer independent and complementary information on the activity state and dynamics of quiescent and eruptive volcanoes and thus all contribute to volcanic risk assessment. In spite of their wide use, there have been only a few efforts to systematically integrate and compare the results of these different monitoring techniques. Here we combine seismic (volcanic tremor and long‐period seismicity), deformation (GPS), and geochemical (volcanic gas plume CO2/SO2 ratios) measurements in an attempt to interpret trends in the recent (2007–2008) activity of Etna volcano. We show that each eruptive episode occurring at the Southeast Crater (SEC) was preceded by a cyclic phase of increase‐decrease of plume CO2/SO2 ratios and by inflation of the volcano’s summit captured by the GPS network. These observations are interpreted as reflecting the persistent supply of CO2‐rich gas bubbles (and eventually more primitive magmas) to a shallow (depth of 1–2.8 km asl) magma storage zone below the volcano’s central craters (CCs). Overpressuring of the resident magma stored in the upper CCs’ conduit triggers further magma ascent and finally eruption at SEC, a process which we capture as an abrupt increase in tremor amplitude, an upward (〉2800 m asl) and eastward migration of the source location of seismic tremor, and a rapid contraction of the volcano’s summit. Resumption of volcanic activity at SEC was also systematically anticipated by declining plume CO2/SO2 ratios, consistent with magma degassing being diverted from the central conduit area (toward SEC).
    Description: Published
    Description: Q09008
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: 1.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: volcano monitoring ; Mt. Etna volcano ; geochemistry and geophysics ; volcanic tremor ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 11
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    Response of Mount Etna to dynamic stresses from distant earthquakes (2010)
    American Geophysical Union
    Details
    Publication Date: 2012-02-03
    Description: Influences of distant earthquakes on volcanic systems by dynamic stress transfer are well documented. We analyzed seismic signals and volcanic activity at Mount Etna during two periods, January 2006 and May 2008, that clearly showed variations coincident with distant earthquakes. In the first period, characterized by mild volcano activity, the effect of the dynamic stress transfer, caused by an earthquake in Greece (M = 6.8), was twofold: (1) banded tremor activity changed its features and almost disappeared; (2) a swarm of volcano‐tectonic (VT) earthquakes took place. The changes of the banded tremor were likely due to variations in rock permeability, caused by fluid flows driven by dynamic strain. The VT earthquake swarm probably developed as a secondary process, promoted by the dynamically triggered activation of magmatic fluids. The second period, May 2008, showed an intense explosive activity. During this interval, the dynamic stress transfer, associated with the arrival of the seismic waves of the Sichuan earthquake (M = 7.9), affected the character of the seismo‐volcanic signals and on the following day triggered an eruption. In particular, we observed changes in volcanic tremor and increases of both occurrence rate and energy of long period events. In this case, we suggest that dynamic stress transfer caused nucleation of new bubbles in volatile‐rich magma bodies with consequent buildup of pressure, highlighted by the increase of long period activity, followed by the occurrence of an eruption. We conclude that stresses from distant earthquakes are capable of modifying the state of the volcano.
    Description: Published
    Description: B12304
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Mt. Etna volcano ; dynamic stress transfer ; triggered eruption ; triggered seismicity ; volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 12
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    Anatomy of an unstable volcano from InSAR: Multiple processes affecting flank instability at Mt. Etna, 1994–2008 (2010)
    American Geophysical Union
    Details
    Publication Date: 2012-02-03
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: Volcano deformation may occur under different conditions. To understand how a volcano deforms, as well as relations with magmatic activity, we studied Mt. Etna in detail using interferometric synthetic aperture radar (InSAR) data from 1994 to 2008. From 1994 to 2000, the volcano inflated with a linear behavior. The inflation was accompanied by eastward and westward slip on the eastern and western flanks, respectively. The portions proximal to the summit showed higher inflation rates, whereas the distal portions showed several sectors bounded by faults, in some cases behaving as rigid blocks. From 2000 to 2003, the deformation became nonlinear, especially on the proximal eastern and western flanks, showing marked eastward and westward displacements, respectively. This behavior resulted from the deformation induced by the emplacement of feeder dikes during the 2001 and 2002–2003 eruptions. From 2003 to 2008, the deformation approached linearity again, even though the overall pattern continued to be influenced by the emplacement of the dikes from 2001 to 2002. The eastward velocity on the eastern flank showed a marked asymmetry between the faster sectors to the north and those (largely inactive) to the south. In addition, from 1994 to 2008 part of the volcano base (south, west, and north lower slopes) experienced a consistent trend of uplift on the order of ∼0.5 cm/yr. This study reveals that the flanks of Etna have undergone a complex instability resulting from three main processes. In the long term (103–104 years), the load of the volcano is responsible for the development of a peripheral bulge. In the intermediate term (≤101 years, observed from 1994 to 2000), inflation due to the accumulation of magma induces a moderate and linear uplift and outward slip of the flanks. In the short term (≤1 year, observed from 2001 to 2002), the emplacement of feeder dikes along the NE and south rifts results in a nonlinear, focused, and asymmetric deformation on the eastern and western flanks. Deformation due to flank instability is widespread at Mt. Etna, regardless of volcanic activity, and remains by far the predominant type of deformation on the volcano.
    Description: ESA provided the SAR data (Cat‐1 no. 4532 and GEO Supersite initiative). The DEM was obtained from the SRTM archive, while the ERS‐1/2 orbits are courtesy of the TU‐Delft, The Netherlands. This work was partially funded by INGV and the Italian DPC (DPCINGV project V4 “Flank”), the Italian DPC (under special agreement with IREA‐CNR), and the Italian Space Agency under contract “sistema rischio vulcanico (SRV).” The authors thank Francesco Casu, Paolo Berardino, and Riccardo Lanari for their support and Geoff Wadge and Michael Poland for their helpful and constructive review of the manuscript.
    Description: Published
    Description: B10405
    Description: 1.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 1.10. TTC - Telerilevamento
    Description: 3.2. Tettonica attiva
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: Flank instability ; InSAR ; volcanoes ; Etna ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous ; 04. Solid Earth::04.03. Geodesy::04.03.99. General or miscellaneous ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions ; 05. General::05.04. Instrumentation and techniques of general interest::05.04.99. General or miscellaneous ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
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  • 13
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    Focal mechanisms for sub‐crustal earthquakes in the Gulf of Cadiz from a dense OBS deployment (2010)
    American Geophysical Union
    Details
    Publication Date: 2012-02-03
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: An eleven‐month deployment of 25 ocean bottom seismometers provides an unprecedented opportunity to study low‐magnitude local earthquakes in the complex transpressive plate boundary setting of the Gulf of Cadiz, known for the 1755 Lisbon earthquake and tsunami. 36 relocated earthquakes (ML 2.2 to 4.8) concentrate at 40– 60 km depth, near the base of the seismogenic layer in ∼140 Ma old oceanic mantle lithosphere, and roughly align along two perpendicular, NNE‐SSW and WNWESE striking structures. First motion focal mechanisms indicate compressive stress for the cluster close to the northern Horseshoe fault termination which trends perpendicular to plate convergence. Focal mechanisms for the second cluster near the southern termination of the Horseshoe fault indicate a strike‐slip regime, providing evidence for present‐day activity of a dextral shear zone proposed to represent the Eurasia‐Africa plate contact. We hypothesize that regional tectonics is characterized by slip partitioning.
    Description: Published
    Description: L18309
    Description: 3.1. Fisica dei terremoti
    Description: 3.2. Tettonica attiva
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: oceanic lithospheric mantle ; focal mechanisms ; stress tensor inversion ; Gulf of Cadiz ; ocean bottom seismometer ; 1755 Lisbon earthquake ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress
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  • 14
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    Predicting the impact of lava flows at Mount Etna (Italy) (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Forecasting the time, nature and impact of future eruptions is difficult at volcanoes such as Mount Etna, in Italy, where eruptions occur from the summit and on the flanks, affecting areas distant from each other. Nonetheless, the identification and quantification of areas at risk from new eruptions is fundamental for mitigating potential human casualties and material damage. Here, we present new results from the application of a methodology to define flexible high-resolution lava invasion susceptibility maps based on a reliable computational model for simulating lava flows at Etna and on a validation procedure for assessing the correctness of susceptibility mapping in the study area. Furthermore, specific scenarios can be extracted at any time from the simulation database, for land-use and civil defence planning in the long-term, to quantify, in real-time, the impact of an imminent eruption, and to assess the efficiency of protective measures.
    Description: This work was sponsored by the Italian Ministry for Education, University and Research, FIRB project n° RBAU01RMZ4 “Lava flow simulations by Cellular Automata”, and by the National Civil Defence Department and INGV (National Institute of Geophysics and Volcanology), project V3_6/09 “V3_6 – Etna”.
    Description: In press
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: 4.4. Scenari e mitigazione del rischio ambientale
    Description: JCR Journal
    Description: open
    Keywords: lava flows ; Etna ; hazard evaluation ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.02. Cellular automata, fuzzy logic, genetic alghoritms, neural networks ; 05. General::05.02. Data dissemination::05.02.99. General or miscellaneous ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions ; 05. General::05.08. Risk::05.08.99. General or miscellaneous ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
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  • 15
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    Rupture history of the 2009 L’Aquila (Italy) earthquake from non-linear joint inversion of strong motion and GPS data (2010)
    Agu
    Details
    Publication Date: 2017-04-04
    Description: We image the rupture history of the 2009 L’Aquila (Central Italy) earthquake using a nonlinear joint inversion of strong motion and GPS data. This earthquake ruptured a normal fault striking along the Apennines axis and dipping to the SW. The inferred slip distribution is heterogeneous and characterized by a small, shallow slip patch located up-dip from the hypocenter (9.5 km depth) and a large, deeper patch located southeastward. The rupture velocity is larger in the up-dip than in the along-strike direction. This difference can be partially accounted by the crustal structure, which is characterized by a high velocity layer above the hypocenter and a lower velocity below. The latter velocity seems to have affected the along strike propagation since the largest slip patch is located at depths between 9 and 14 km. The imaged slip distribution correlates well with the on-fault aftershock pattern as well as with mapped surface breakages.
    Description: Published
    Description: L19304
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: 2009 L'Aquila earthquake ; kinematic inversion ; joint inversion ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 16
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    Dike emplacement and flank instability at Mount Etna: Constraints from a poro-elastic-model of flank collapse (2010)
    Elsevier B.V.
    Details
    Publication Date: 2017-04-04
    Description: Many volcanic edifices are subject to flank failure, usually produced by a combination of events, rather than any single process. From a dynamic point of view, the cause of collapse can be divided into factors that contribute to an increase in shear stress, and factors that contribute to the reduction in the friction coefficient μ of a potential basal failure plane. We study the potential for flank failure at Mount Etna considering a schematic section of the eastern flank, approximated by a wedge-like block. For such geometry, we perform a (steady state) limit equilibrium analysis: the resolution of the forces parallel to the possible basal failure plane allows us to determine the total force acting on the potentially unstable wedge. An estimate of the relative strength of these forces suggests that, in first approximation, the stability is controlled primarily by the balance between block weight, lithostatic load and magmatic forces. Any other force (sea load, hydrostatic uplift, and the uplift due to mechanical and thermal pore-fluid pressure) may be considered of second order. To study the model sensitivity, we let the inferred slope α of the basal surface failure vary between −10° and 10°, and consider three possible scenarios: no magma loading, magmastatic load, and magmastatic load with magma overpressure. We use error propagation to include in our analysis the uncertainties in the estimates of the mechanics and geometrical parameters controlling the block equilibrium. When there is no magma loading, the ratio between destabilizing and stabilizing forces is usually smaller than the coefficient of friction of the basal failure plane. In the absence of an initiating mechanism, and with the nominal values of the coefficient of friction μ=0.7±0.1 proposed, the representative wedge will remain stable or continue to move at constant speed. In presence of magmastatic forces, the influence of the lateral restraint decreases. If we consider the magmastatic load only, the block will remain stable (or continue to move at constant speed), unless the transient mechanical and thermal pressurization significantly decrease the friction coefficient, increasing the instability of the flank wedge for αN5° (seaward dipping decollement). When the magma overpressure contribution is included in the equilibrium analysis, the ratio between destabilizing and stabilizing forces is of the same order or larger than the coefficient of friction of the basal failure plane, and the block will become unstable (or accelerate), especially in the case of the reduction in friction coefficient. Finally, our work suggests that the major challenge in studying flank instability at Mount Etna is not the lack of an appropriate physical model, but the limited knowledge of the mechanical and geometrical parameters describing the block equilibrium.
    Description: This work was funded by Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the Italian Dipartimento per la Protezione Civile (DPC) (DPC-INGV project V4 “Flank”).
    Description: In press
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.2. Tettonica attiva
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: Etna ; dike intrusion ; flank instability ; poro-elasticity ; analytical modelling ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous
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  • 17
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    The first Long Period earthquake detected in the background seismicity at Mt. Vesuvius (2013)
    Istituto Nazionale di Geofisica e Vulcanologia
    Details
    Publication Date: 2017-04-04
    Description: The typical earthquakes occurring at Mt. Vesuvius are Volcano-Tectonic. On July 20, 2003, an unusual earthquake with low and narrow frequency content was detected. The seismograms presented an emergent onset and a nearly monochromatic spectrum at all stations of the Osservatorio Vesuviano(Istituto Nazionale di Geofisica e Vulcanologia) seismic network. The event was located at about 4 km b.s.l. close to the crater axis and an equivalent duration magnitude of 0.6 was estimated. The nature of this event was investigated by comparing its features with those of two typical Volcano-Tectonic earthquakes occurred inside the same source volume. We compared the spectral content calculating the spectrograms and the coda patterns using the Hilbert Transform. A Seismic Moment Tensor inversion was performed on the low frequency earthquake. The focal mechanisms for the two Volcano-Tectonic earthquakes were estimated with a classical technique and resulted compatible with the stress field acting on the volcano. Taking into account the clear differences with the typical Volcano-Tectonic events as well as the peculiarities retrieved from our analyses (monochromatic, low frequency spectral content, and sustained coda) and also some geochemical observations, we classify the unusual low frequency seismic event detected at Mt. Vesuvius as Long Period earthquake and propose that its origin could be linked to a pressure drop in the deep hydrothermal system.
    Description: Published
    Description: S0440
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: open
    Keywords: Volcano monitoring ; Volcanic event classification ; Long Period earthquake ; Signal analysis ; Hydrothermal system ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 18
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    Insights into magma and f luid transfer at Mount Etna by a multiparametric approach: A model of the events leading to the 2011 eruptive cycle (2013)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Since the second half of the 1990s, the eruptive activity of Mount Etna has provided evidence that both explosive and effusive eruptions display periodic variations in discharge and eruption style. In this work, a multiparametric approach, consisting of comparing volcanological, geophysical, and geochemical data, was applied to explore the volcano's dynamics during 2009–2011. In particular, temporal and/or spatial variations of seismicity (volcano-tectonic earthquakes, volcanic tremor, and long-period and very long period events), ground deformation (GPS and tiltmeter data), and geochemistry (SO2 flux, CO2 flux, CO2/SO2 ratio) were studied to understand the volcanic activity, as well as to investigate magma movement in both deep and shallow portions of the plumbing system, feeding the 2011 eruptive period. After the volcano deflation, accompanying the onset of the 2008–2009 eruption, a new recharging phase began in August 2008. This new volcanic cycle evolved from an initial recharge phase of the intermediate-shallower plumbing system and inflation, followed by (i) accelerated displacement in the volcano's eastern flank since April 2009 and (ii) renewal of summit volcanic activity during the second half of 2010, culminating in 2011 in a cyclic eruptive behavior with 18 lava fountains from New Southeast Crater (NSEC). Furthermore, supported by the geochemical data, the inversion of ground deformation GPS data and the locations of the tremor sources are used here to constrain both the area and the depth range of magma degassing, allowing reconstructing the intermediate and shallow storage zones feeding the 2011 cyclic fountaining NSEC activity.
    Description: Published
    Description: 3519–3539
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: restricted
    Keywords: Mt Etna ; seismology ; ground deformation ; geochemistry ; volcanology ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 19
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    Towards an Automatic Monitoring System of Infrasonic Events at Mt. Etna: Strategies for Source Location and Modeling (2010)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Active volcanoes characterized by open conduit conditions generate sonic and infrasonic signals, whose investigation provides useful information for both monitoring purposes and studying the dynamics of explosive processes. In this work, we discuss the automatic procedures implemented for a real-time application to the data acquired by a permanent network of five infrasound stations running at Mt. Etna volcano. The infrasound signals at Mt. Etna consist in amplitude transients, called infrasound events. The adopted procedure uses a multi-algorithm approach for event detection, counting, characterization and location. It is designed for an efficient and accurate processing of infrasound records provided by single-site and array stations. Moreover, the source mechanism of these events can be investigated off-line or in near real-time by using three different models: (1) Strombolian bubble; (2) resonating conduit and (3) Helmholtz resonator. The infrasound waveforms allow us to choose the most suitable model, to get quantitative information about the source and to follow the time evolution of the source parameters.
    Description: Published
    Description: 1215–1231
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Infrasound ; monitoring system ; Mt. Etna volcano ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
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  • 20
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    New insights into banded tremor from the 2008–2009 Mount Etna eruption (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We investigated the banded tremor activity occurring at Mt. Etna volcano between August-October 2008 during the 2008-2009 eruption. The banded tremor occurred in episodes lasting 25-30 minutes with intervals in between the episodes of about 25 minutes. Seismic signal analyses showed that the banded tremor was characterised by spectral contents, wavefields and source locations that differed from the “ordinary” volcanic tremor. The infrasound recordings exhibited an intermittent infrasonic tremor alternating with the banded tremor episodes. Finally, nonlinear analyses suggested that banded tremor system can be considered chaotic, implying: i) sensitive dependence on initial conditions, suggesting not only that a banded tremor system requires particular conditions to generate, but also that slight variations of these conditions are able to greatly change the features of the banded tremor or even to stop it; ii) long-term unpredictability, that is, the impossibility to forecast the long-term evolution of the banded tremor. On the basis of all these results and analogies with geyser models, we suggest a model of banded tremor that invokes alternating recharge-discharge phases. Banded tremor is due to “perturbations” in shallow aquifers, such as fluid movement and bubble growth or collapse due to hydrothermal boiling, triggered by the heat and hot fluid transfer from the underlying magma bodies. This heat-fluid transfer also causes an increasing pressure in the aquifer leading to fluid-discharge. During this process the seismic radiation decreases and, if the fluid-discharge is well coupled with the atmosphere, acoustic signals are generated.
    Description: Published
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Banded tremor ; Mt. Etna volcano ; volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 21
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    Spatial distribution of intrinsic and scattering seismic attenuation in active volcanic islands – II: Deception Island images (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: In this work, we present regional maps of the inverse intrinsic quality factor (Qi −1), the inverse scattering quality factor (Qs −1) and total inverse quality factor (Qt −1) for the volcanic environment of Deception Island (Antarctica). Our attenuation study is based on diffusion approximation, which permits us to obtain the attenuation coefficients for every single couple source-receiver separately. The data set used in this research is derived from an active seismic experiment using more than 5200 offshore shots (air guns) recorded at 32 onshore seismic stations and four ocean bottom seismometers. To arrive at a regional distribution of these values, we used a new mapping technique based on a Gaussian space probability function. This approach led us to create ‘2-D probabilistic maps’ of values of intrinsic and scattering seismic attenuation. The 2-D tomographic images confirm the existence of a high attenuation body below an inner bay of Deception Island. This structure, previously observed in 2-D and 3-D velocity tomography of the region, is associated with a massive magma reservoir. Magnetotelluric studies reach a similar interpretation of this strong anomaly. Additionally, we observed areas with lower attenuation effects that bear correlation with consolidated structures described in other studies and associated with the crystalline basement of the area. Our calculations of the transport mean-free path and absorption length for intrinsic attenuation gave respective values of ≈950 m and 5 km, which are lower than the values obtained in tectonic regions or volcanic areas such as Tenerife Island. However, as observed in other volcanic regions, our results indicate that scattering effects dominate strongly over the intrinsic attenuation.
    Description: This work has been partially supported by the Spanish project Ephestos, CGL2011–29499-C02–01, by the EU project EC-FP7 MEDiterranean SUpersite Volcanoes (MED-SUV), by the Basque Government researcher training program BFI09.277 and by the Regional project ‘Grupo de Investigaci´on en Geof´ısica y Sismolog´ıa de la Junta de Andaluc´ıa, RNM104.’ Edoardo del Pezzo was partly supported by DPC-INGV projects UNREST SPEED and V2 (Precursori).
    Description: Published
    Description: 1957-1969
    Description: 3.1. Fisica dei terremoti
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: restricted
    Keywords: Seismic attenuation; ; Seismic tomography ; Volcano seismology ; Wave scattering and diffraction ; Wave propagation ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
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  • 22
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    New kinematic constraints of the western Doruneh fault, north-eastern Iran, from interseismic deformation analysis (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: We used the SBAS DInSAR analysis technique to estimate the interseismic deformation along the western part of the Doruneh fault system (DFS), northeastern Iran. We processed 90 ENVISAT images from four different frames from ascending and descending orbits. Three of the ground velocity maps show a significant interseismic signal. Using a simple dislocation approach we model 2-D velocity profiles concerning three InSAR data set relative to the western part of the DFS, obtaining a good fit to the observations. The resulting model indicates that a slip rate of ∼5mmyr−1 accumulates on the fault below 10 km depth, and that in its western sector the Doruneh fault is not purely strike-slip (left-lateral) as in its central part, but shows a significant thrust component. Based on published geological observations, and assuming that all interseismic deformation is recovered with a single event, we can estimate a characteristic recurrence interval between 630 and 1400 yr.
    Description: Published
    Description: 622-628
    Description: 1.10. TTC - Telerilevamento
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: Image processing; Satellite geodesy; Seismic cycle; Radar interferometry; Seismicity and tectonics; Continental tectonics: strike-slip and transform. ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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  • 23
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    Magnitude scale for LP events: a quantification scheme for volcanic quakes (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The peculiar source characteristics of long-period seismic events (time persistency of the source, low-frequency peaks in the source spectrum, absence of high-frequency radiation) prevent the formation of a definite high-frequency coda in the seismograms. In contrast, this is well formed in volcano–tectonic quakes. For this reason, the widely used duration magnitude scale that is based on the proportionality between the energy and the coda duration cannot be used for long-period estimation. In observatory practice, the long-period magnitude is sometimes estimated using the same duration magnitude scale, leading to confusing results. In this report, we show a new method to estimate the magnitude of long-period events that generally occur for volcanoes, with some application examples from data for Mt Etna (Italy), Colima Volcano (Mexico) and Campi Flegrei (Italy).
    Description: Published
    Description: 911-919
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake source observations; ; Volcano monitoring ; Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 24
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    A unified 3D velocity model for the Neapolitan volcanic areas (2013)
    Istituto Nazionale di Geofisica e Vulcanologia
    Details
    Publication Date: 2017-04-04
    Description: One of the main issues in seismic monitoring of active volcanic areas is the accurate location of earthquake hypocenters. Volcano-tectonic seismicity is often characterized by small magnitude swarms, recorded by few seismic stations with a high picking uncertainty. Sometimes events lacks clear S-wave arrivals, due to the nature of some volcanic sources. All these features, together with the complex crustal structure of volcanoes, makes the earthquake location problem critical in such areas. One of the most important effort for improving the quality of hypocenter location is the use of realistic 3D velocity models. In the last 10 years, several scientific papers proposed 2D and 3D velocity models for Mt. Vesuvius, Campi Flegrei and the Gulf of Naples. They comes from both active seismic data (VESUVIO 94, TOMOVES 96, MAREVES 97 and SERAPIS 2001 experiments) and from local earthquake tomography. In this report we propose a global unified velocity model spanning from Ischia island to Appennine Mts. that allows us to locate earthquakes in the Neapolitan volcanic areas and in the Gulf of Naples. This model comes from a weighted averaging of 5 tomographic velocity models and a background regional model. Most of the model provides only P-wave velocities, only 2 models, obtained through local earthquake tomography at Mt. Vesuvius and Campi Flegrei also gives a S-wave velocity estimate. We show the difference between this new model and the previous 1D models adopted for routine locations at INGV-Osservatorio Vesuviano. We also relocate some events, using non-linear techniques showing differences in hypocenter position from previous locations and the improvement in final traveltime residuals and location uncertainties.
    Description: Published
    Description: 375-390
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: open
    Keywords: Volcano-tectonic seismicity ; 3D velocity model ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 25
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    Vent temperature trends at the Vulcano Fossa fumarole field: the role of permeability (2013)
    Springer Berlin Heidelberg
    Details
    Publication Date: 2017-04-04
    Description: Between 1994 and 2010, we completed 16 thermal surveys of Vulcano’s Fossa fumarole field (Aeolian Islands, Italy). In each survey, between 400 and 1,200 vent temperatures were collected using a thermal infrared thermometer from distances of ∼1 m. The results show a general decrease in average vent temperature during 1994–2003, with the average for the entire field falling from ∼220°C in 1994 to ∼150°C by 2003. However, between 2004 and 2010, we witnessed heating, with the average increasing to ∼190°C by 2010. Alongside these annual-scale field-wide trends, we record a spatial re-organisation of the fumarole field, characterised by shut down of vent zones towards the crater floor, matched by rejuvenation of zones located towards the crater rim. Heating may be expected to be associated with deflation because increased amounts of vaporisation will remove volume from the hydrothermal system Gambino and Guglielmino (J Geophys Res 113: B07402, 2008). However, over the 2004–2010 heating period, no ground deformation was observed. Instead, the number of seismic events increased from a typical rate of 37 events per month during 1994–2000 to 195 events per month during 2004–2010. As part of this increase, we noticed a much greater number of high-frequency events associated with rock fracturing. We thus suggest that the heating event of 2004–2010 was the result of changed permeability conditions, rather than change in the heat supply from the deeper magmatic source. Within this scenario, cooling causes shut down of lower sectors and re-establishment of pathways located towards the crater rim, causing fracturing, increased seismicity and heat flow in these regions. This is consistent with the zone of rejuvenation (which lies towards and at the rim) being the most favourable location for fracturing given the stress field of the Fossa cone Schöpa et al. (J Volcanol Geotherm Res 203:133–145, 2011); it is also the most established zone, having been active at least since the early twentieth century. Our data show the value of deploying multi-disciplinary geophysical campaigns at degassing (fumarolic) hydrothermal systems. This allows more complete and constrained understanding of the true heat loss dynamics of the system. In the case study presented here, it allows us to distinguish true heating from apparent heating phases. While the former are triggered from the bottom-up, i.e. they are driven by increases in heat supply from the magmatic source, the latter are triggered from the top-down, i.e. by changing permeability conditions in the uppermost portion of the system to allow more efficient heat flow over zones predisposed to fracturing.
    Description: Published
    Description: 1293-1311
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: 1.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: restricted
    Keywords: Fumaroles ; Vulcano ; Vent temperature ; Seismicity ; Ground Deformation ; Permeability ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 26
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    Are the source models of the M7.1 1908 Messina Straits earthquake reliable? Insights from a novel inversion and a sensitivity analysis of levelling data (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: For decades, many authors have attempted to define the location, geometry and kinematics of the causative fault for the 1908 December 28, M 7.1 earthquake that struck the Messina Straits between Sicily and Calabria (southern Italy). The coseismic displacement caused a predominant downwarping of the Straits and small land uplift away from it, which were documented by levelling surveys performed 1 yr before and immediately after the earthquake. Most of the source models based on inversion of levelling data suggested that the earthquake was caused by a low angle, east-dipping blind normal fault, whose upper projection intersects the Earth surface on the Sicilian (west) side of the Messina Straits.An alternative interpretation holds that the causative fault is one of the high-angle, west-dipping faults located in southern Calabria, on the eastern side of the Straits, and may in large part coincide with the mapped Armo Fault. Here, we critically review the levelling data with the aim of defining both their usefulness and limits in modelling the seismogenic fault. We demonstrate that the levelling data alone are not capable of discriminating between the two oppositely dipping fault models, and thus their role as a keystone for modellers is untenable. However, new morphotectonic and geodetic data indicate that the Armo Fault has very recent activity and is accumulating strain. The surface observations, together with appraisal ofmacroseismic intensity distribution, available seismic tomography and marine geophysical evidence, lends credit to the hypothesis that the Armo and possibly the S. Eufemia faults are part of a major crustal structure that slipped during the 1908 earthquake.
    Description: Published
    Description: 1025-1041
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake source ; Messina Straits ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
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  • 27
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    Preliminary analysis of surface temperature anomalies that preceded the two major Emilia 2012 earthquakes (Italy) (2013)
    Istituto Nazionale di Geofisica e Vulcanologia
    Details
    Publication Date: 2017-04-04
    Description: In the 1980's, from an analysis of satellite images, Russian scientists reported on a short-term thermal infrared radiation enhancement that occurred before some medium-to-large earthquakes in central Asia [Gorny et al. 1988]. Since then, many researchers have been studying earthquake thermal anomalies with satellite remote sensing data [Qiang et al. 1991, Tronin 1996, Tramutoli et al. 2001, Ouzounov and Freund 2004, Saraf and Choudhury 2004, Aliano et al. 2008, Blackett et al. 2011]. Recently, abnormal surface latent heat flux [Dey and Singh 2003, Cervone et al. 2005, Qin et al. 2009, Qin et al. 2011, Qin et al. 2012], outgoing long-wave radiation [Ouzounov et al. 2007] and microwave radiation [Takashi and Tadashi 2010] have also been shown to precede earthquakes. To investigate the possible physical mechanisms of such satellite thermal anomalies, some studies conducted a series of detecting experiments on rock loaded to fracturing [Wu et al. 2000, Freund 2002, Wu et al. 2002, Wu et al. 2006a, Wu et al. 2006b, Freund et al. 2007], and some hypotheses have been proposed. These have included: leaking of pore-gas, and hence the resulting greenhouse effect [Qiang et al. 1995]; activating and recombining of p-holes during rock deformation [Freund 2002]; release of latent heat due to near-surface air ionization [Pulinets et al. 2006], and stress-induced thermal effects due to friction and fluids [Wu and Liu 2009]. According to the Istituto Nazionale di Geofisica e Vulcanologia (INGV; National Institute of Geophysics and Volcanology), two major earthquakes with almost the same large magnitudes struck northern Italy, on the Po Plain in the Emilia Region. The first hit on May 20, 2012, at 02:03 UTC, with ML 5.9 (44.89 °N, 11.23 °E; 6 km in depth), and the second on May 29, 2012, at 07:00 UTC, with ML 5.8 (44.85 °N, 11.09 °E; 10 km in depth). These caused a total of 27 deaths and widespread damage. In this study, the long-term temperature data from both satellite and ground (with greater emphasis on the satellite data) have been used to determine whether there were thermal anomalies associated with this Emilia 2012 seismic sequence. In particular, the next section will be dedicated to describing both the data and the method of analysis. In Section 3, we provide the more significant results, which we discuss in Section 4, together with the main conclusions. We acknowledge that this work cannot be exhaustive, as it will require more data and analyses. However, although further studies will be welcome, we are confident that we have done the best with the data at our disposal.
    Description: Published
    Description: 823-828
    Description: 1.10. TTC - Telerilevamento
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: open
    Keywords: earthquake event ; numerical method ; surface temperature ; Emilia-Romagna, Italy ; Emilia ; 04. Solid Earth::04.02. Exploration geophysics::04.02.05. Downhole, radioactivity, remote sensing, and other methods ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
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  • 28
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    Spatial distribution of intrinsic and scattering seismic attenuation in active volcanic islands – I: model and the case of Tenerife Island (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The complex volcanic system of Tenerife Island is known to have a highly heterogeneous character, as recently confirmed by velocity tomography.We present new information derived from intrinsic quality factor inverse maps (Qi −1), scattering quality factor inverse maps (Qs −1) and total quality factor inverse maps (Qt −1) obtained for the same region. The data set used in this work is the result of the analysis of an active seismic experiment carried out, using offshore shots (air guns) recorded at over 85 onshore seismic stations. The estimates of the attenuation parameters are based on the assumption that the seismogram energy envelopes are determined by seismic energy diffusion processes occurring inside the island. Diffusion model parameters, proportional to Qi −1 and to Qs −1, are estimated from the inversion of the energy envelopes for any source–receiver couple. They are then weighted with a new graphical approach based on a Gaussian space probability function, which allowed us to create ‘2-D probabilistic maps’ representing the space distribution of the attenuation parameters. The 2-D images obtained reveal the existence of a zone in the centre of the island characterized by the lowest attenuation effects. This effect is interpreted as highly rigid and cooled rocks. This low-attenuation region is bordered by zones of high attenuation, associated with the recent historical volcanic activity. We calculate the transport mean free path obtaining a value of around 4 km for the frequency range 6–12 Hz. This result is two orders of magnitude smaller than values calculated for the crust of the Earth. An absorption length between 10 and 14 km is associated with the average intrinsic attenuation parameter. These values, while small in the context of tectonic regions, are greater than those obtained in volcanic regions such as Vesuvius or Merapi. Such differences may be explained by the magnitude of the region of study, over three times larger than the aforementioned study areas. This also implies deeper sampling of the crust, which is evidenced by a change in the values of seismic attenuation. One important observation is that scattering attenuation dominates over the intrinsic effects, Qi being at least twice the value of Qs.
    Description: This work has been partially supported by the Spanish project Ephestos, CGL2011-29499-C02-01, by the EU project EC-FP7 MEDiterranean SUpersite Volcanoes (MED-SUV), by the Basque Government researcher training program BFI09.277 and by the Regional project ‘Grupo de Investigaci´on en Geof´ısica y Sismolog´ıa de la Junta de Andaluc´ıa, RNM104’. EdP has been partly supported by DPC-INGV projects UNREST SPEED and V2 (Precursori).
    Description: Published
    Description: 1942-1956
    Description: 3.1. Fisica dei terremoti
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Seismic attenuation ; ; Seismic tomography; ; Volcano seismology ; Wave propagation. ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
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  • 29
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    Seismic attenuation imaging of Campi Flegrei: Evidence of gas reservoirs, hydrothermal basins, and feeding systems (2010)
    Agu
    Details
    Publication Date: 2019-03-05
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: Passive high‐resolution attenuation tomography is used here to image the geological structure in the first upper 4 km of the shallow crust beneath the Campi Flegrei caldera, southern Italy. The inverse Q was estimated for each source‐receiver path using the coda‐normalization method (S‐waves) and the slope decay method (P‐waves and S‐waves). Inversion was performed using a multi‐resolution method, which ensures a minimum cell‐size resolution of 500 m. The study of the resolution matrix as well as the synthetic tests guarantee an optimal reproduction of the input anomalies in the center of the caldera, between 0 and 3.5 km in depth. High attenuation vertical structures are connected at the surface with the main volcanological features (e.g., the Solfatara and Mofete fumarole fields), and depict vertical Q contrast imaging important geological structures, such as the La Starza fault. These high attenuation volumes extend between the surface and a depth of about 3 km, where a hard rock layer is imaged by the sharp contrast of the quality factors. The retrieved image of the Campi Flegrei has been jointly interpreted taking into account evidence from seismological, geological, volcanological and geochemical investigations. This analysis has allowed an unprecedented view of the feeding systems in this area, and in particular it recognizes the vertically extending, high attenuation structures that correspond to gas or fluid reservoirs beneath Pozzuoli‐Solfatara, Solfatara, Mofete‐Mt. Nuovo and Agnano. This high‐attenuation system is possibly connected with the magma sill revealed at about 7 km in depth by passive travel‐time tomography.
    Description: Published
    Description: B09312
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Campi Flegrei ; gas ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods
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  • 30
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    Time-space variation of volcano-seismic events at La Fossa (Vulcano, Aeolian Islands, Italy): new insights into seismic sources in a hydrothermal system (2010)
    Springer
    Details
    Publication Date: 2020-02-24
    Description: We investigated the relationship between volcano-seismic events, recorded at La Fossa crater of Vulcano (Aeolian Islands, Italy) during 2004-2006, and the dynamics of the hydrothermal system. During the period of study, three episodes of increasing numbers of volcano-seismic events took place at the same time as geothermal and geochemical anomalies were observed. These geothermal and geochemical anomalies have been interpreted as resulting from an increasing deep magmatic component of the hydrothermal fluids. Three classes of seismic events (long period, high frequency and monochromatic events), characterised by different spectral content and various similarity of the waveforms, have been recognised. These events, clustered mainly below La Fossa crater area at depths of 0.5–1.1 km b.s.l., were space-distributed according to the classes. Based on their features, we can infer that such events at Vulcano are related to two different source mechanisms: (1) fracturing processes of rocks and (2) resonance of cracks (or conduits) filled with hydrothermal fluid. In the light of these source mechanisms, the increase in the number of events, at the same time as geochemical and geothermal anomalies were observed, was interpreted as the result of an increasing magmatic component of the hydrothermal fluids, implying an increase of their flux. Indeed, such variation caused an increase of both the pore pressure within the rocks of the volcanic system and the amount of ascending fluids. Increased pore pressures gave rise to fracturing processes, while the increased fluid flux favoured resonance and vibration processes in cracks and conduits. Finally, a gradual temporal variation of the waveform of the hybrid events (one of the subclasses of long period events) was observed, likely caused by heating and drying of the hydrothermal system.
    Description: Published
    Description: 803-816
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Volcano seismology ; Vulcano Island ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 31
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    Short‐term and long‐term tremor migration patterns of the Cascadia 2004 tremor and slow slip episode using small aperture seismic arrays (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: Tectonic tremor has been recorded at many subduction zones, including the Nankai, Cascadia, Mexican, and Alaskan subduction zones. This study, the first to use small aperture seismic arrays to track tremor, deployed three small aperture seismic arrays along the Cascadia subduction zone during a tremor and slow slip episode in July 2004. The tremor was active during virtually all (up to 99%) minutes of the analyzed tremor episode using 5 min sample windows. Individual wave phases were tracked across the arrays and used to derive slowness vectors. These were compared with slowness vectors computed from a standard layered Earth model to derive tremor locations. Locations were stable within a volume roughly 250 km2 in epicenter and 20 km in depth for hours to days before moving to a new volume. The migration between volumes was not smooth, and the movement of the sources within the volume followed no specific pattern. Overall migration speeds along the strike of the subduction zone were between 5 and 15 km/d; smaller scale migration speeds between volumes reached speeds up to 2 km/min. Uncertainties in the best locations were 5 km in epicenter and 10 km in depth. For this data set and processing methodology, tremor does not locate predominately on the primary subduction interface. Our favored model for the generation of tectonic tremor signals is that the tremor is triggered by stress and fluid pressure changes caused by slow slip and is composed, at least in part, of low‐frequency earthquakes broadly distributed in location
    Description: Published
    Description: B00A24
    Description: 3.2. Tettonica attiva
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: tremor migration ; Cascadia 2004 ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics
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  • 32
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    Distribution of volcanic earthquake recurrence intervals (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We analyze the distribution of volcanic earthquake recurrence intervals in the Vesuvio, Campi Flegrei, and Hawaii regions and compare it with tectonic recurrence rates in California. We find that the distribution behavior is similar for volcanic and tectonic seismic events. In both cases, the recurrence interval distributions collapse onto the same master curve if time is rescaled by the average occurrence rate. This implies that both phenomena have the same temporal organization, and it is possible to adopt for volcanic areas that the same occurrence models used for tectonic regions.
    Description: Published
    Description: B10309
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: volcanic earthquake ; recurrence intervals ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
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  • 33
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    Detachment depth revealed by rollover deformation: An integrated approach at Mount Etna (2010)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Flank instability is common at volcanoes, even though the subsurface structures, including the depth to a detachment fault, remain poorly constrained. Here, we use a multidisciplinary approach, applicable to most volcanoes, to evaluate the detachment depth of the unstable NE flank of Mt. Etna. InSAR observations of Mount Etna during 1995–2008 show a trapdoor subsidence of the upper NE flank, with a maximum deformation against the NE Rift. The trapdoor tilt was highest in magnitude in 2002–2004, contemporaneous with the maximum rates of eastward slip along the east flank. We explain this deformation as due to a general eastward displacement of the flank, activating a rotational detachment and forming a rollover anticline, the head of which is against the NE Rift. Established 2D rollover construction models, constrained by morphological and structural data, suggest that the east‐dipping detachment below the upper NE flank lies at around 4 km below the surface. This depth is consistent with seismicity that clusters above 2–3 km below sea level. Therefore, the episodically unstable NE flank lies above an east‐dipping rotational detachment confined by the NE Rift and Pernicana Fault. Our approach, which combines short‐term (InSAR) and long‐term (geological) observations, constrains the 3D geometry and kinematics of part of the unstable flank of Etna and may be applicable and effective to understand the deeper structure of volcanoes undergoing flank instability or unrest.
    Description: This work was partially funded by INGV and the DPC‐INGV project “Flank”, and partially by the ASI (SRV project).
    Description: Published
    Description: L16304
    Description: 1.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 1.10. TTC - Telerilevamento
    Description: 3.2. Tettonica attiva
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: reserved
    Keywords: flank instability ; fault ; InSAR ; Etna ; rollover ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous ; 04. Solid Earth::04.03. Geodesy::04.03.99. General or miscellaneous ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
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  • 34
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    Anomalous far-field geodetic signature related to the 2009 L’Aquila (central Italy) earthquake (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2022-05-24
    Description: The broad availability of geodetic measurements for the Mw 6.3 April 6th 2009 L’Aquila earthquake allowed an unprecedented description of the co- and post-seismic ground deformations, leading to the definition of the Paganica fault geometry and kinematics. Through DInSAR, we found, in a wide area of 20 kilometres on the Paganica hangingwall, a further displacement up to 7 cm, which might have occurred in the earthquake proximity. In this study, we explore the possibility of the co-, post- and pre-seismic alternative scenarios. Although our data are not sufficient to undoubtedly prove that this signal occurred before the main event, this seems to be the most likely hypothesis based on tectonics constraints and image acquisition times. The nature of this deformation remains unclear, but we speculate that deep fluids played a role. These results can drive ad hoc requirements for future space-based missions and design of the GPS network.
    Description: Published
    Description: 343–351
    Description: 1.10. TTC - Telerilevamento
    Description: JCR Journal
    Description: restricted
    Keywords: InSAR ; L'Aquila earthquake ; GPS ; Anomalous signature ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 35
    Electronic Resource
    Electronic Resource
    Stability of steady states in nucleic acid poly[d(A-T)] synthesis and the stirred flow reactor (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1-14 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The template directed synthesis of poly[d(A-T)] from the nucleoside triphosphates in the presence of DNA polymerase I is carried out continuously in a stirred flow reactor for the first time. The initial objective is to test the kinetic stability of the established steady states at various flow rates. Graphical analysis predicts instable steady states for certain high flow rates. As a consequence of instabilities multiple steady states and steady-state hysteresis may occur. Steady-state hysteresis has now been found experimentally. For a different enzyme fraction of low exonuclease activity we found the steady-state absorbance at 260 nm to be almost invariant with flow rate at high enzyme concentrations even if the flow rate was increased by a large factor. We call this phenomenon kinetic buffering. Relaxation of a large flow perturbation approaches the steady state in a sigmoidal fashion. Concentration oscillations at 260 nm occurred in one experiment using an enzyme fraction of low exonuclease activity after perturbing the steady state by monomer (dATP). Advantages of the stirred flow reactor method over serial transfer are discussed.
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    Circular dichroism of corticotropin, fragment 1-24, and model compounds. An assessment of the contributions of the peptide chromophore and aromatic residues (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 43-59 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The far-ultraviolet circular dichroic spectrum of the 39-residue peptide hormone porcine corticotropin and the biologically active fragment corticotropin 1-24 is negative from 250 nm to 195 nm in water, but in 6M guanidinium chloride a positive band appears at about 225 nm. The temperature and guanidinium chloride dependence of this spectral transition indicates the absence of any stable ordered secondary structure in corticotropin and the spectrum is seen to be in only partial agreement with results using the model peptide chromophore, Ala-Ala-Ala. Using oligopeptides containing aromatic amino acid residues sandwiched between glycyl residues, it is shown that the shape and intensity of the corticotropin 225 nm positive band which appears in 6M guanidinium chloride is in agreement with the far-ultraviolet transitions of the aromatic chromophores in the hormone. Curve resolution of the near-ultraviolet circular dichroic spectrum of corticotropin and comparison of the rotational strengths of the phenylalanyl and tyrosyl bands reveals no evidence for increased rotational freedom in 6M guanidinium hydrochloride. Spectral changes are observed, however, in the transitions arising from the single tryptophan. This study suggests that corticotropin in aqueous solution may serve as a better model for the circular dichroic spectrum of the aperiodic regions in globular proteins than either synthetic homopolypeptides or reference proteins for which spectral and X-ray diffraction data are available.
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    Polynucleotide circular dichroism calculations: Use of an all-order classical coupled oscillator polarizability theory (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 131-152 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An all-order classical coupled oscillator theory in which monomer band shapes are explicity taken into account is applied to the calculations of polynucleotide circular dichroism. Calculations are shown for ApA and oligoadenylic acid of varying chain lengths, in both RNA and B-DNA geometry, and the advantages of this theory are assessed. By introducing an effective dielectric constant, good agreement with measured spectra is obtained. Variations in monomer parameters are tested in an attempt to eliminate remaining discrepancies between calculated and measured spectra.
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    Raman studies of bovine serum albumin (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 203-218 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The Raman Spectra of bovine serum albumin have been obtained in the solute state, in alkaline and acidic solutions, and in the gel. The reversible denaturations of bovine serum albumin solutions by heat, acid's, and alkali were studied and a new mechanism for heat denaturation has been proposed based on a continuous unfolding of the α-helices.
    Additional Material: 10 Ill.
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    Low-frequency Raman spectra of lysozyme (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 219-225 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: New techniques in laser Raman spectroscopy are used to obtain spectra of aqueous solutions of lysozylme for frequency shifts as small as 5 cm-1. In addition, Raman measurements are made on two crystalline forms of hen egg white lysozyme. The spectra obtained from the solution and from the crystal are found to be similar for frequencies above 100 cm-1. However, a low-frequency band at 25 cm-1 observed in crystalline lysozyme is not found in the solution, indicating that this band cannot be attributed to an internal molecular vibration.
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    Thickness and density of protein films by optical mixing spectroscopy (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 257-263 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The adsorption of protein films on polystyrene latex spheres was studied by optical mixing spectroscopy. With this technique, we show that both the hydrodynamic thickness of protein films and their optical density can be measured. Thus, we found that films of the glycoproteins isolated from the human erythrocyte membrane were four times as thick as films of either human serum albumin or bovine serum albumin for about the same surface coverage. This result suggests an end-on orientation for the adsorbed glycoprotein molecules, which is consistent with the model proposed by others for the orientation of these molecules at the surface of the red blood cell itself.
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    Preferential solvent binding and change in conformation of bovine serum albumin in 2-chloroethanol-water mixed solvents (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 293-299 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Solvent binding to bovine serum albumin in 2-chloroethanol-water mixed solvents of different composition, measured previously by Inoue and Timasheff (Biopolymers (1972) 11, 737-43) is applied to a hydrodynamic study of the solvated protein.From sedimentation and diffusion data, the apparent molecular weight of the solvated protein particle can be calculated, provided an average partial specific volume, computed from the composition of the particle, is introduced in Svedberg's equation. The unsolvated molecular weight of the protein can than be calculated by subtraction of the bound solvent. Further data on the hydrodynamic particle (f/fmin and axial ratio of the equivalent ellipsoid) are readily calculated from these experiments, and reinforce the supposition that 2-chloroethanol is a strong helix-inducing solvent.
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    Masthead (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976) 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Cooperative ligand binding by ferrihemoglobin: An experimental artifact? (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 403-414 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have carried out a detailed study of ligand binding of ferrihemoglobins under various conditions. Our results show that n varies with time and that this variation is paralleled by changes in the spectrum of methemoglobin. This suggests some form of structural perturbation. The time-dependent value of n is discussed in terms of the observed spectral changes accompanying prolonged equilibration.
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    1H Nuclear magnetic resonance studies of histidine-containing di- and tripeptides. Estimation of the effects of charged groups on the pKa value of the imidazole ring (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 393-401 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nmr titration curves of chemical shifts versus pH were observed for the protons of various histidine-containing di- and tripeptides. With these results, the macroscopic pKa values and the chemical shifts intrinsic to each ionic species were determined by a computer curve-fitting based on a simple acid dissociation sequence. The pKa value of the imidazole ring in N-acetyl-L-histidine methylamide was assumed to represent the intrinsic (or unperturbed) pKa of the imidazole rings of histidine having peptide linkages at both the CO and NH sides. The pKa values of the imidazole rings observed for most di- and tripeptides were reasonably reproduced by simple calculations using the intrinsic value and the perturbations due to the CO2- and NH3+ groups located at various positions. Some other factors affecting the pKa value of the imidazole ring are also discussed.
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    Masthead (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976) 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1976.360150201
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    Interpretation of hypochromic and hyperchromic intensity changes in the Raman spectra of polypeptides and polynucleotides undergoing transition (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 241-255 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hyperchromic and hypochromic changes in the intensity of the amide-I and amide-III lines of polypeptides and certain ring vibrations of the bases of polynucleotides are shown to be related to similar changes in the lower energy uv absorption bands. The selection rules strictly limit the pairs of excited electronic states that can contribute to the elements of the polarizability matrix. An energy-dependent term in this equation weights the contribution of the pairs of electronic transitions in favor of those involving the lower energy transitions. For both polypeptides and polynucleotides, there is a large hypochromic inensity change in the first π → π* exciton band upon the coil-to-helix transition. Through the selection rules, certain conformationally sensitive Raman lines are shown to derive their intensity predominantly from this band and hence also display hypochromism. Again, through an application of the selection rules, certain Raman lines can be demonstrated to depend predominantly for their intensity upon the n → π* transition, and consequently have the opposite hyperchromic intensity change upon the same conformational transition.
    Additional Material: 7 Ill.
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    Length and dipole moment of TMV by laser signal-averaging transient electric birefringence (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 301-315 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transient electric birefringence experiments have been performed on well-characterized highly monodisperse samples of tobacco mosaic virus (TMV). Experiments and calculations are presented that show that the sensitivity and accuracy of the traditional transient electric birefringence technique can be enhanced by several orders of magnitude through the use of a low-powered laser and crystal polarizing optics, signal averaging, and digital data processing. Measurements of the field-free decay of the birefringence yield for the rotational diffusion coefficient, DR = 318 ± 3 sec-1. The length of the rodlike virion, calculated from the Broersma equation with this value of DR and a rod diameter of 15 nm, is 292.5 ± 1.0 nm. Measurements of the growth of the birefringence when an electric field is applied across the sample yield μ2/kT(α∥ - α⊥) = 0.47 ± 0.07, where μ is the permanent dipole moment (assumed parallel to the symmetry axis of the virus) and α∥ - α⊥ is the electrical polarizability anistropy of the virus. Using the value of α∥ - α⊥ measured by O'Konski et al., we then obtain μ = 2.5 × 10-14 esu cm.
    Additional Material: 6 Ill.
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    High-resolution nmr study of yeast tRNACUALeu and the native and denatured conformers of yeast tRNAUUGLeuSubmitted by BFR in partial fulfillment of the requirements for the Ph.D. degree in chemistry at the University of California, Riverside. (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 325-336 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The high-resolution nmr spectrum of baker's yeast tRNACUALeu, a recently sequenced non-denaturable tRNA, has been compared with the spectra of the native and denatured conformers of the closely related species tRNAUUGLeu. Because of the presence of many common base pairs in the different tRNA's, it is possible to assign most of the low-field resonances to specific secondary-structure base pairs. A comparison of the observed positions of the various resonances with those predicted by a semiempirical ring-current shift theory shows a root-mean-square deviation of 0.14, 0.11, and 0.12 ppm for tRNAUUGLeu (native), and tRNAUUGLeu (denatured), respectively. These results support the ring-current shift theory currently used to interpret the low-field nmr spectra of the tRNA molecules. Differences between the predicted and observed positions of some resonances provide new evidence for higher order effects such as shifts from second nearest neighbors, anomalous shifts exerted by G·U base pairs, and tertiary-structure effects. A model that was previously proposed for the denatured conformer of tRNAUUGLeu is also supported.
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    Masthead (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976) 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1976.360150301
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    On the application of polyelectrolyte limiting laws to the helix-coil transition of DNA. IV. Dependence of helix stability on the concentration of divalent metal ions (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 457-468 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The molecular theory of the previous paper in this series is extended to determine the effect of divalent metal ions on helix stability relative to coil at fixed ionic strength and nucleotide phosphate concentration. Specification of the state of condensed counterions, as well as their concentration, is essential for the solution of this problem, and it is assumed that they translate freely within a thin cylindrical shell close to the polynucleotide. As a function of divalent counterion concentration mB2+ the relative stability of the helix is highly nonlinear. Although the overall trend is that the helix stability increases with addition of divalent metal ion, there is a narrow concentration range for which it decreases slightly. The behavior of the relative stability as a function of mB2+ is determined by the translational degrees of freedom of the counterions, both univalent and divalent, both condensed and uncondensed. Detailed comparison of the theory with data is not given here, but it is pointed out that the calculated values of the relative stability are consistent with the order of magnitude of the observed effect Mg2+ on the melting temperature.
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    An X-ray study of poly(L-prolyl-L-α-phenylglycyl-L-proline) (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 503-506 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: X-ray diffraction studies have been made on the polytripeptide poly(L-prolyl-L-α-phenylglycyl-L-proline). Its structure has been found to be helical, with a poly(L-proline) II conformation, packed in an orthorhombic lattice, space group P21212, with a = 14.3 Å, b = 13.5 Å, and c = 9.4 Å.
    Additional Material: 1 Ill.
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    Effect of saturation of the ion atmosphere polarization on the orientation factor of the electric birefringence of rodlike polyelectrolytes (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 583-587 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1976.360150313
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    Measurement of circular dichroism using a thin cell (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 591-594 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
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    Masthead (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Molecular forces in ribosomes and polynucleotide complexes (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 649-653 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The stability constant of the complex of tRNA with 50S subunits of ribosomes was compared in ordinary and heavy water. A considerable effect (about fourfold) was observed, showing the importance of hydrogen bonds in this interaction. In addition, the isotope effect of complementary polynucleotide interaction was measured for two examples. In the case of the binary complex of heptainosinic acid oligomers with poly(C) in the presence of 10-3 M MgCl2, the transfer from ordinary to heavy water gave an increase of the stability constant of about 5%. But in the case of a ternary complex of hexaadenylic acid with poly(U) under the same conditions, the stability constant in D2O increased threefold. The isotope effect depends strongly on magnesium ion concentration and is possibly due to some specific mechanism of magnesium ion complexing involving water molecules.
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    The effect of binding on the melting temperature of biopolymers (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 999-1000 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Calculations of the conformation of mono-, di-, and regular polynucleotides (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1009-1013 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    Calculation of the molecular parameters of the α-helix-coil and β-structure-coil transitions (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1061-1080 
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    Notes: Monte-Carlo calculations of geometric and thermodynamic characteristics of the α-helix and the β-structure of polypeptides have been carried out. To describe a hydrogen bond both the Lippincott-Schroeder and Morse potentials were used. The internal rotation angles ϕ and ψ in the α-helix have been shown to fluctuate in the range of ±7°. The distribution functions on angles ϕ and ψ and on hydrogen bond lengths and angles in the α-helix have been computed and compared with those in myoglobin and lysozyme. Thermodynamic characteristics of the α-helix calculated in different approximations with the two forms of the hydrogen bond potentials have also been compared. The data obtained are close to the experimental values for polypeptides in neutral solution.Some geometric and thermodynamic characteristics of the regular parallel and antiparallel and irregular antiparallel β-structure have been found. In the β-structure the internal rotation angles vary within the interval ±15-20°. An increase in the cross and longitudinal dimensions of the β-structure only slightly influence both the geometric and thermodynamic characteristics.
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    Co-oligopeptides of aromatic amino acids and glycine with a variable distance between the aromatic residues. III. Co-oligopeptides of L-phenylalanine, L-tryptophan, and glycine: Synthesis and ultraviolet absorption properties (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1103-1117 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: The preparation of the co-oligopeptides of the series H-Gly-Phe-(Gly)n-Trp-Gly-OH (n = 0, 1, 2) and of other free peptides of glycine, L-tryptophan, and L-phenylalanine is reported. The syntheses have been carried out by conventional methods, using N-hydroxysuccinimide esters for the coupling steps. The ultraviolet absorption properties of the free peptides have been investigated in water. No hypo- or hyperchromicity was found for the aromatic chromophores, with the exception of H-Gly-Phe-Trp-OH, which shows a small but significant hypochromicity. The contribution of the peptide bond to the molar absorptivity in the far ultraviolet has been separated from that of the side chain plus the —COO- group by plotting the measured molar absorptivity ∊ of the farthest accessible uv maximum as a function of the number of peptide bonds (nA). The peptide bond contribution proved to be independent of nA in the range nA = 1-5, thus ruling out the onset of helical conformations in the longer chain peptides.
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    Spatial electron distribution and population analysis of amides, carboxylic acid, and peptides, and their relation to empirical potential functions (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1167-1200 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The properties of the electron distribution in amides, peptides, and carboxylic acids, obtained from ab-initio molecular orbital calculations using both minimal and extended basis sets have been studied. These properties are discussed in terms of some of the common assumptions made in empirical conformational calculations of biomolecules. In particular, population analyses of 15 compounds in these families were carried out with both the minimal and extended basis sets, and compared with results of CNDO/2 calculations. It is suggested that population analysis is a useful tool for recognizing patterns of charge distributions, and investigating the transferability of parameters of different functional groups. However, its use for providing partial charges for conformational analysis is a questionable procedure.A more detailed analysis of the charge distribution was carried out by calculating the spatial electron distribution in the four compounds, N-methylacetamide, acetic acid, diketopiperazine, and N-acetyl-N′-methylalanine. Both total electron-density maps and differencedensity maps are presented. The properties of the overall shape of the molecule and the atoms in the molecule, are discussed in terms of the former along with three-dimensional shape plots of the total density. The distortion accompanying molecular formation, resulting in such features as the lone pair orbital and “bonding deensities” is discussed in terms of the difference maps. Semiquantitative estimates of the bonding and orbital densities resulting from the integration of the densities are also presented. Finally, one of the novel features of the study is the presentation of three-dimensional surfaces of constant difference densities from which the shapes of the orbitals and bonding densities emerge.
    Additional Material: 18 Ill.
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    Conformational properties of the sequential polyproline analogs poly(Pro-Aze-Pro) and poly(Aze-Pro-Aze) (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1233-1242 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lack of the positive band at around 226 nm in the CD spectra of poly(prolyl-azetidine-2-carbonyl-proline) in trifluoroethanol and of poly(azetidine-2-carbonyl-prolyl-azetidine-2-carboxylic) acid in F3EtOH and water, the hyperchromism of the absorption maximum at about 202 nm, and the extremely small intensity of the Cβ-Pro, Cγ-Pro, and Cβ-Aze signals for the cis peptide bonds in the 13C nmr spectrum of poly(Pro-Aze-Pro) in F3EtOH indicate that both polyproline analogs exist as disordered chains in this solvent, the trans peptide group being maintained. The disordering of the chains is attributed to an increase in the accessible range of ψ due to the reduced dimensions of the square ring of L-azetidine-2-carboxylic acid residue relative to the pyrrolidine ring of proline and to strong interactions of the haloalcohol with the peptide groups of the chains.
    Additional Material: 7 Ill.
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    Rapid characterization of protein molecular weights and hydrodynamic structures by quasielastic laser-light scattering (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1283-1299 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two methods for the characterization of protein molecular weights from their diffusion coefficients are discussed. These measurements can be made quickly and reliably at low concentrations using quasielastic light-scattering techniques. First, an empirical calibration of the diffusion coefficient at infinite dilution of denatured random coils against molecular weight is reported. The second method combines the measurement of D0 with the intrinsic viscosity [η]. This D0-[η] relationship proves to be very insensitive to polymers structure or solvent type. The data indicate that the ratio of the hydrodynamic radius measured by viscosity to the hydrodynamic radius measured by diffusion is about 15% smaller than that predicted by theoretical models. The nature of the molecular-weight average obtained for polydisperse systems is defined for a Schulz distribution. These hydrodynamic methods have also been used to demonstrate the presence of chain branching in the glycoprotein ovomucoid. In addition, a method is proposed by which the effective segment length and an excluded volume parameter for random coils may be evaluated for diffusion measurements.
    Additional Material: 7 Ill.
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    Conformations of protected oligo(γ-methyl-L-glutamates) at the air-water interface (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1425-1430 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1976.360150714
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    The role of alcohols in the polymerization of NCA's by alkaline alkoxides. Dualism of the polymerization mechanism (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1431-1435 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1976.360150715
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    Evidence for long-range interactions in DNA. Analysis of melting curves of block polymers d(C15A15)·d(T15G15), d(C20A15)·d(T15G20), and d(C20A10)·d(T10G20) (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1461-1479 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of one DNA region on the stability of an adjoining region (telestability) was examined. Melting curves of three block DNA's, d(C15A15)·d(T15G15), d(C20A15)·d(T15G20), and d(C20A10)·d(T10G20) were analyzed in terms of the nearest neighbor Ising model. Comparisons of predicted and experimental curves were made in 0.01 M and 0.1 M sodium ion solutions. The nearest neighbor formalism was also employed to analyze block DNA transition in the presence of actinomycin, a G·C specific molecule. The results show that nearest neighbor base-pair interaction cannot predict the melting curves of the block DNA's. Adjustments in theoretical parameters to account for phosphate repulsion assuming a B conformation throughout the DNA's do not alter this conclusion. Changes in the theoretical parameters, which provide good overall agreement, are consistent with a substantial stabilization of the A·T region nearest the G·C block. The melting temperature T A·T for the average A·T pari in d(C20A10)·d(T10G20), with 10 A·T pairs, appears to be 4°C greater than TA·T for d(C15A15)·d(T15G15) and d(C20A15)·d(T15G20), both with 15 A·T pairs. Actinomycin bound to the G·C end effectively stabilizes the A·T end by 9°C. These results indicate a long-range contribution to the interactions governing DNA stability. A possible mechanism for these interactions will be discussed.
    Additional Material: 6 Ill.
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    Effect of concentration on the aggregation of poly(γ-benzyl-L-glutamate) in dioxane: Critical concentration and maximum length for linear head to tail aggregates (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1543-1554 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dielectric relaxation studies in the frequency range 100 Hz to 2 MHz of poly(γ-benzyl-L-glutamate) in dioxane have been carried out over a range of concentration 10-4-10-2g/g. The structure of aggregates is analyzed in terms of dipole moment and relaxation time. A critical concentration (≃ 10-3 g/g for the studied molecular weights) has been determined below which the aggregates are found to have linear head to tail type structure. Above the critical concentration a different structure of aggregates is apparent which could not be fully analyzed by these measurements alone. Possible forms of aggregation above the critical concentration are discussed. Formation of long range order which would lead to nematic liquid crystalline phase at higher concentrations has been discussed as one of the possible explanations for the observed behavior above the critical concentration.Maximum length of linear head to tail type aggregates for poly(γ-benzyl-L-glutamate) in dioxane as determined from these results correspond to an α-helix of molecular weight 210,000. A slight difference in the purity of dioxane has been shown to have an influence on the reproducibility of the state of aggregation as well as on the rate of disaggregation on dilution.
    Additional Material: 7 Ill.
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    Racemization in the synthesis of sequential polypeptides using N-hydroxysuccinimide esters (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1585-1590 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemization in the synthesis of peptide intermediates and their polymers was investigated, using L-amino acid oxidase. The formation of N-hydroxysuccinimide esters from N-protected peptide acids yielded optically pure products in contrast to p-nitrophenyl and pentachlorophenyl active esters. The racemization in the polymerization step was found to be base sensitive. Partially racemized polymer can result from optically homogeneous monomer. Thus, the optical integrity of active monomer species carries no guarantee for that of the polymer.
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    N-methylleucine gramicidin-S and (di-N-methylleucine) gramicidin-S conformations with cisL-Orn-L-N-MeLeu peptide bonds (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1623-1635 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformations containing all trans peptide bonds have previously been proposed for N-methylleucine gramicidin-S and (di-N-methylleucine) gramicidin-S based on an evaluation of proton nuclear magnetic resonance parameters in a series of solvents. These gramicidin-S derivatives exhibit full biological activity despite the fact that the proposed solution conformations differ in backbone topology and relative orientation of the Phe and Orn side chains compared to gramicidin-S. The present authors discuss conformations for N-methylleucine gramicidin-S and (di-N-methylleucine) gramicidin-S which incorporate cis peptide bonds at L-Orn-L-N-MeLeu, where the gramicidin-S backbone is essentially retained, and the relative orientation of the Pro, Orn, Val, and Phe side chains correspond to those observed for gramicidin-S. A novel hydrogen-bond arrangement involving one carbonyl group interacting with two peptide protons (1 ←4 and 1 ←5 types) is proposed to stabilize the backbone conformation in the gramicidin-S derivatives. A recent report on the cyclic heptapeptide antibiotic, Ilamycin B1, shows the presence of cis peptide bonds at N-CH3 amino acids, as well as the novel hydrogen-bond arrangement presented above.
    Additional Material: 6 Ill.
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    Conversion of fibrinogen to fibrin. The correlation between clotting kinetics and morphology of fibrin polymerized in different solvent media (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1979-1990 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The morphology of fibrin strongly depends on solvent medium, as shown by clotting experiments carried out in the presence of different salts. The clots were characterized by electron microscopy and spectrophotometric methods; the kinetics of gelation were determined.In the presence of electrolytes which strongly delay clotting, the strands are thin and few branching points are observed; opposite morphological changes are induced by salts which act as accelerating agents. On the basis of this correlation, and of previous data on the structure of fibrin, a kinetic model of the self-assembly process is outlined. It accounts well for the observed solvent effects on the morphology of the network.An important result emerging from our experiments is that the fibers undergo branching prior to gelation. Branching points arise from the defective growth of the fibers; a simple explanation of the occurrence of branching may be obtained by our self-assembly model.
    Additional Material: 5 Ill.
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    The X-Pro peptide bond as an nmr probe for conformational studies of flexible linear peptides (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2025-2041 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The equilibrium between the cis and trans forms of X-Pro peptide bonds can readily be measured in the 13C nmr spectra. In the present paper we investigate how observation of this equilibrium could be used as an nmr probe for conformational studies of flexible polypeptide chains. The experiments include studies by 13C nmr of a series of linear oligopeptides containing different X-L-Pro peptide bonds, with X = Gly, L-Ala, L-Leu, L-Phe, D-Ala, D-Leu, and D-Phe. Overall the study confirms that X-Pro peptide bonds can generally be useful as 13C nmr probes reporting the formation of nonrandom conformation in flexible polypeptide chains. It was found that the cis-trans equilibrium of X-Pro is greatly affected by the side chain of X and the configuration of the α-carbon atom of X. On the basis of these observations some general rules are suggested for a practical applications of the X-Pro nmr probes in conformational studies of polypeptide chains.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1976.360151012
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    Conformational studies in aqueous solution on random copolymers of L-glutamic acid and ortho-nitrobenzyl-L-glutamate. Circular dichroism and potentiometric titration studies (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2101-2119 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Random copolymers of L-glutamic acid and ortho-nitrobenzyl-L-glutamate were synthesized with different percentages of nitrobenzyl-L-glutamate, from 3 to 22%. These copolymers were studied by circular dichroism (CD) and potentiometric titrations in aqueous solutions in order to determine the variation of the stability of the secondary structure when the concentration of nitrobenzylglutamate varies in the copolymer. We observed that the stability increases with the concentration of glutamate. Such a stabilization could be due to either side-chain interactions or interactions between the aromatic side chain with the backbone. An intermolecular aggregation was observed when the percentage of nitrobenzylglutamate was sufficently important, but such an aggregation may be avoided if a dioxane/water mixture is used as a solvent.
    Additional Material: 9 Ill.
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    Kinetics of γ-benzyl-L-glutamate NCA's polymerizations and molecular-weight distributions on corresponding polymers (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2185-2199 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of γ-benzyl-L-glutamate NCA's polymerizations in dioxane as solvent are discussed. The partial orders respective to [A], the NCA concentration and [I0], the initial initiator concentration are given; the rate constants are deduced and a mechanism is proposed to justify a rate of polymerization Vp = k[A][I0]2.The dependence of the rate constants on the conformation of the growing chains is demonstrated; the acceleration is attributed to the ordered structures favorable to hydrogen bonding. The kinetics of aging have also been examined and discussed; it is shown that they cannot modify the kinetics of polymerization.The DPn were obtained on the same samples before and after debenzylation; it is proved that at any concentration, DPn ≃ [A0]/[I0].The molecular-weight distributions were obtained by chromatography and a polydispersity lower than 1.3 was deduced for each sample. The trimodal distribution, appearing as soon as [A0]/[I0] is larger than 3, is attributed to the existence of the three structures σ, β, and α. The weight fraction of each of the structures was correlated to the kinetics of polymerization.
    Additional Material: 10 Ill.
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    Electron diffraction of Valonia cellulose. A quantitative interpretation (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1903-1915 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of native cellulose (Valonia) has been analyzed by electron diffraction. Possible models for the structure were refined by rigid-body least squares methods, which incorporated parameters defining the preferred orientation of the fibrils around their long axes in the cell wall lamellae. The structure was found to consist of an array of chains having the same sense (i.e., parallel), with packing parameters similar to those recently determined by X-ray diffraction. The eight-chain unit cell could be approximated adequately by a two-chain monoclinic unit cell with dimensions a = 8.18 Å, b = 7.84 Å, c = 10.38 Å (fiber axis), and γ = 97.04°; the space group is P21.
    Additional Material: 4 Ill.
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    Relative stability of the α-helix of deuterated poly(γ-benzyl-L-glutamate) (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1939-1950 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coil-to-helix transition temperatures of hydrogen bearing and deuterated poly(γ-benzyl-L-glutamate) in 1,3-dichlorotetrafluoroacetone/H2O and/D2O mixtures, respectively, have been determined. Together with previously obtained data for the conformational transition of this polypeptide in normal and deuterated dichloroacetic acid, these results have been used in an analysis of the effect of deuterium substitution on the intrinsic stability of the α-helical form of poly(γ-benzyl-L-glutamate). The findings, consistent for both solvent systems, showed that the deuterated polypeptide is some 5% more stable than the normal protonated poly(γ-benzyl-L-glutamate), while the polypeptide-active solvent interaction enthalpy is also slightly increased by deuterium substitution in the respective molecules. A consideration of available data for poly(β-benzyl-L-aspartate) reveals an anomaly with respect to the present analysis.
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    Electric field-induced conformational change of poly(L-lysine) studied by transient electric birefringence (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1669-1676 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transient electric birefringence measurements on poly(L-lysine hydrobromide) in methanol-water mixtures have been carried out at various solvent compositions in the vicinity of the helix-coil transition region (from 87 to 98 vol % methanol). Anomalous birefringence transients were observed between 90 and 95 vol % methanol above a threshold field strength. A distinct difference between the responses to weak and strong electric fields was noticed over a narrow range of the solvent composition. The effects of polymer concentration and temperature on the field-strength dependence of the birefringence were studied at a solvent composition of 90 vol % methanol where the anomalous transients appeared most clearly. The double logarithmic plots of the steady-state specific birefringence versus the square of field strength for different concentrations and temperatures could be superimposed by shifting them horizontally along the abscissa. The threshold field strength which was determined from the shift factor decreased with decreasing concentration. The results provide further evidence that strong electric fields can cause a helix-coil transition in this system under favorable conditions.
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    Studies of peptide conformation: Backbone folding of tetrapeptide derivatives in methanol and water (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1701-1715 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Derivatives of tetrapeptide sequences considered likely to form β-turns were investigated by the study of their proton magnetic resonances in methanol and in water. Differential broadening of N - H resonances by an added nitroxyl was used to indicate the presence of the sequestered N - H proton expected in β-turn conformations. Transfer of magnetic saturation from solvent water protons to N - H protons was also examined. The evidence is consistent with significant contributions by β-turn-like backbones to the conformational averages in methanol of the sequences Gly-L-Pro-D-Val-Gly, D(or L)-Val-L-Pro-Gly-Gly, and Gly-L-Pro-L-Asn-Gly, but not the sequence Gly-D-Ala-L-Val-Gly. It is suggested that a Type I turn, Likely in Gly-L-Pro-L-Asn-Gly derivatives, is characterized by sequestered N - H protons of both the third and fourth residues. For all of the peptide derivatives, save possibly Ac-L-Val-L-Pro-Gly-Gly-NHNH2, contributions from folded structures in water are not detectable by line-broadening experiments. However, the transfer of saturation experiments may be interpreted as indicating some degree of chain folding in water.
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    The spatial distribution of moving macromolecules undergoing isomerization (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1717-1739 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper we use probabilistic arguments to derive and discuss the spatial distribution of molecules which are undergoing electrophoresis or centrifugation while at the same time they are switching back and forth between two configurational states. An exact solution is obtained for arbitrary values of the diffusion coefficients of the two isomerizing states. The traditional analytic method of solving this problem, namely, by use of “master equations,” is not completely satisfactory because one can find only the Fourier transform of the solution rather than the solution itself. Our treatment yields the answer one would get if it were feasible to perform the inversion of the Fourier transform.
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    Synthesis of sequential oligopeptides and polypeptide having the sequence of L-alanyl-L-leucylglycine (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1815-1824 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of sequential oligopeptides having simple nonpolar side chains, Nps-(L-Ala-L-Leu-Gly)n- OEt has been prepared by a stepwise fragment-condensation method using Nps-L-alanyl-L-leucylglycine N-hydroxysuccinimide ester, which was prepared by the Nps-N-carboxy α-amino-acid-anhydride method. The success of the synthesis of the peptide having a high-molecular weight, such as octadecapeptide, results from the highest solubility of the tripeptide unit, L-alanyl-L-leucylglycine. The sequential polypeptide having the same tripeptide sequence was also prepared by polycondensation of the tripeptide N-hydroxy-succinimide ester.
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    Comparison of different theoretical descriptions of helix-coil transitions in DNA (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1841-1844 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1976.360150917
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    Time-dependent Hartree calcuations of nucleic acid hypochromism (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1873-1875 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/bip.1976.360150923
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    Cooperative disordering of single-stranded polynucleotides through copper crosslinking (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1879-1902 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal transitions of single-stranded polynucleotides are noncooperative. In contrast, Cu(II) cooperatively disorders the single-stranded helical structures of poly(A) and poly(C), as demonstrated by ORD and UV spectral changes as a function of the Cu2+ activity, and by a dramatic chain-length dependence of the spectral changes. Equilibrium dialysis binding studies indicate that the cooperative disordering is paralleled by a somewhat less cooperative binding process.The difference between the thermal- and Cu(II)-induced transition is explained by the following mechanism. (1) Cu(II) initially binds in a noncooperative fashion to phosphate. (2) The Cu(II) so bound forms a second bond to a nonadjacent base site on the same polymer strand or another strand. These intramolecular and intermolecular crosslinks to the bases are responsible for the disordering. (3) The initial crosslinks formed provide nuclei for the cooperative formation of additional crosslinks, producing cooperative spectral changes paralleled by cooperative binding.A comparison of the spectral and binding transitions indicates that there is appreciable noncooperative binding of copper to phosphate, which produces no spectral changes in the presence of added electrolyte. This comparison also indicates that each copper crosslink disorders several bases. The formation of intermolecular crosslinks is demonstrated by a polymer concentration dependence of the disordering. The formation of intramolecular crosslinks can be deduced from the fact that the “cooperative unit” required to explain the differences between the hexamer, which does not readily form intramolecular crosslinks, and the polymer is considerably larger than the cooperative unit determined from the polymer results.The poly(A) disordering transition is less symmetrical than that of poly(C), particularly at low polymer concentrations. These results, together with other phenomena, are explained by a greater flexibility of poly(A), which favors the formation of small intramolecular loops.
    Additional Material: 9 Ill.
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    Influence of ribose 2′-O-methylation on GpC conformation by classical potential energy calculations (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1951-1964 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Potential energy calculations were employed to examine the effect of ribose 2′-O-methylation on the conformation of GpC. Minimum energy conformations and allowed conformational regions were calculated for 2′MeGpC and Gp2′MeC. The two lowest energy conformations of 2′MeGpC and Gp2′MeC are similar to those of GpC itself. The helical RNA conformation (sugar pucker-C(3′)-endo, ω′ and ω,g-g-, bases-anti) is the global minimum, and a helix-reversing conformation with ω′, ω in the vicinity of 20°, 80° is next in energy. However, subtle differences between the three molecules are noted. When the substitution is on the 5′ ribose (Gp2′MeC), the energy of the helical conformation is less than that of GpC, due to favorable interactions of the added methyl group. When the substitution is at the 3′ ribose (2′MeGpC) these stabilizing interactions are outweighed by steric restrictions, and the helical conformation is of higher energy than for GpC. Furthermore, the statistical weight of the 2′MeGpC g- g- helical region is substantially less than the corresponding weight for Gp2′MeC. In addition, 2′MeGpC′s methoxy group is conformationally restricted to a narrow range centered at 76°. This group has a broadly allowed region between 50 and 175° in Gp2′MeC. These differences occur because the appended methyl group in 2′MeGpC is located in the interior of the helix cylinder, as it would be in polynucleotide, while it hangs unimpeded in Gp2′MeC. These findings suggest that 2′-O-methylation has both stabilizing and destabilizing influences on the helical conformation of RNA. For 2′MeGpC the destabilizing steric hindrance imposed by the nature of the guanine base dominates.
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    Nmr studies of the molecular conformations in the linear oligopeptides H-(L-Ala)n-L-Pro-OH (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2043-2057 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular conformations of the linear oligopeptides H-(L-Ala)n-L-Pro-OH, with n = 1,2 and 3, have been investigated. 13C nmr observation of the equilibrium between the cis and trans forms of the Ala-Pro peptide bond indicated the occurrence of nonrandom conformations in solutions of these flexible peptides. The formation of the nonrandom species containing the cis form of the Ala-Pro bond was found to depend on the deprotonation of the carboxylic acid group of proline, the solvent, and the ionic strength in aqueous solution. The influence of intramolecular hydrogen bonding on the relative conformational energies of the species containing the cis and trans Ala-Pro peptide bond was studied by comparison of the peptides H-(Ala)n-Pro-OH with analogous molecules where hydrogen bond formation was excluded by the covalent structure. In earlier work a hydrogen bond between the protonated terminal carboxylic acid group and the carbonyl oxygen of the penultimate amino acid residue had been suggested to stabilize conformations including trans proline. For the systems described here this hypothesis can be ruled out, since the cis:trans ratio is identical for molecules with methyl ester protected and free protonated terminal carboxylic acid groups of proline. Direct evidence for hydrogen bond formation between the deprotonated terminal carboxylic acid group and the amide proton of the penultimate amino acid residue in the molecular species containing cis proline was obtained from 1H nmr studies. However, the cis:trans ratio of the Ala-Pro bond was not affected by N-methylation of the penultimate amino acid residue, which prevents formation of this hydrogen bond. Overall the experimental observations lead to the conclusion that the relative energies of the peptide conformations including cis or trans proline are mainly determined by intramolecular electrostatic interactions, whereas in the molecules considered, intramolecular hydrogen bonding is a consequence of specific peptide backbone conformations rather than a cause for the occurrence of energetically favored species. Independent support for this conclusion was obtained from model consideration which indicated that electrostatic interactions between the terminal carboxylic acid group and the carbonyl oxygen of the penultimate amino acid residue could indeed account for the observed relative conformational energies of the species containing cis and trans proline, respectively.
    Additional Material: 4 Ill.
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    Masthead (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1976.360151101
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    Packing analysis of carbohydrates and polysaccharides. IV. A new method for detailed crystal structure refinement of polysaccharides and its application to V-amyloseThe work described in this paper was presented at the “Makromolekulares Kolloquium Freiburg”, in Freiburg, West Germany, March 1975. (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2121-2136 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for predicting and solving crystal structures of linear homopolysaccharides. The method is based on the refinement of the structure with respect to either stereochemical constraints or x-ray diffraction intensities. In the refinement process, all conformational and packing features of the molecule, such as bond lengths, bond angles, conformational angles, nonbonded contacts, hydrogen bonds, etc., can be allowed to vary until the structure reaches both a conformation and crystalline packing that are in minimum disagreement with the stereochemical restraints and the diffraction data. In this fashion, both packing and conformational features of the structure can be simultaneously refined, and not separately as has been the custom in the past. The refinement procedure is based on a method of constrained optimization which possesses improved characteristics of reaching a solution and avoiding false minima, in comparison with least squares methods. The procedure is, in addition, capable of easily finding molecules of solvent of crystallization. The method was applied to further refining the previously solved crystal structure of V-amylose. The results indicated that contrary to the previously found six-fold molecular symmetry in the P212121 space group, the V-amylose molecule exhibits only two-fold symmetry with the asymmetric unit consisting of three glucose residues in one-half turn of the helix. The three residues are nonequivalent principally due to unequal rotational positions of the hydroxymethyl groups. The crystal structure of V-amylose predicted from stereochemical refinement was identical in all details with that obtained from refining against X-ray data. The excellent agreement with the diffraction data was indicated by the crystallographic disagreement index R = 0.25.
    Additional Material: 4 Ill.
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    Conformational features of 2′-O-methyl-adenosylyl-adenosine (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2167-2184 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to obtain information about the conformational features of a 2′-O-methylated polyribonucleotide at the nearest neighbor level, a detailed nuclear magnetic resonance study of AmpA was undertaken. AmpA was isolated from alkali hydrolysates of yeast RNA, and proton spectra were recorded at 100 MHz in the Fourier transform mode in D2O solutions, 0.01 M, pH 5.4 and 1.5 at 25°C. 31P spectra were recorded at 40.48 MHz. Complete, accurate sets of nmr parameters derived for each nucleotidyl unit by simulation iteration methods.The nmr data were translated into conformational parameters for all the bonds using procedures developed in earlier studies from these laboratories. It is shown that AmpA exists in aqueous solution with a flexible molecular framework, which shows preferences for certain orientations. The ribose rings exist as a 2E ⇄ 3E equilibrium with the  - pA ribose showing a bias for the 3E pucker. The C(4′) - C(5′) bonds of both nucleotidyl units show significant preference (75-80%) to exist in gg conformation. The dominant conformer (80%) about C(5′) - O(5′) of the 5′-nucleotidyl unit is g′g′. Even though an unambiguous determination of the orientation of the 3′-phosphate group cannot be made, tentative evidence shows that it preferentially occupies g+ domains [O(3′) - P trans to C(3′) - C(2′)] in which the H(3′)  - C(3′) - O(3′) - P(3′) dihedral angle is about 31°. There is reasonable evidence that the 2′-O-methyl preferentially occupies the domain in which the O(2′) - CH3 bond is trans to C(2′) - C(1′).Lowering of pH to 1.5, which results in protonation of both the adenine moieties, causes destacking of AmpA. Such destacking is accompanied by small, but real, perturbations in the conformations about most of the bonds in the backbone.A detailed comparison of the solution conformations of ApA and AmpA clearly shows that 2′-O-methylation strongly influences the conformational preference about the C(3′) - O(3′) bond of the 3′-nucleotidyl unit, in addition to inducing small changes in the overall ribophosphate backbone conformational equilibria. The effect of 2′-O-methylation is such that the C(3′) - O(3′) is forced to occupy preferentially the g+ domain rather than the normally preferred g- domain [O(3′) - P trans to C(3′) - C(4′)] in ApA. The data on ApA and AmpA further reveal that the extent of stacking interaction is less in AmpA compared to ApA.It is suggested that stacked species of AmpA exist as right-handed stacks where the magnitude of ω and ω′ about O(5′) - P and P - O(3′) is about 290°. The reason for the lesser degree of stacking in AmpA compared to ApA is intramolecular interaction between 2′-O-methyl and the flexible O(3′) - P - O(5′) bridge, the interaction causing some perturbation in the magnitudes of ω/ω′, causing destacking. The destacking will lead to an increase in χCN by a few degrees, causing an increase in 2E populations; the latter in turn will shift the 3′ phosphate group from g- to g+ domains. In short, a coupled series of conformational events is envisioned at the onset of destacking, made feasible by the interaction between the 2′-O-methyl group and the swivel O(3′) - P - O(5′) bridge.
    Additional Material: 5 Ill.
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    Interaction of sodium decyl sulfate with poly(L-ornithine) and poly(L-lysine) in aqueous solution (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2263-2275 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding isotherms of sodium decyl sulfate to poly(L-ornithine), poly(D,L-ornithine), and poly(L-lysine) at neutral pH were determined potentiometrically. The nature of a highly cooperative binding in all three cases suggests a micelle-like clustering of the surfactant ions onto the polypeptide side groups. The hydrophobic interaction between the nonpolar groups overshadows the coulombic interaction between the charged groups. The titration curves can be interpreted well by the Zimm-Bragg theory. The average cluster size of bound surfactant ions is sufficiently large to promote the β-structure of (L-Lys)n even at a very low binding ratio of surfactant to polypeptide residue, whereas the onset of the helical structure for (L-Orn)n begins after about 7 surfactant ions are bound to two turns of the helix. The CD results are consistent with this explanation.
    Additional Material: 8 Ill.
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    Extrapolation of light-scattering data to determine the molecular weight of T7 DNACommunication presented at the XVII Meeting of the Spanish Society of Physics and Chemistry, Alicante, October 1975 (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2287-2290 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    Synthesis of a cross-linked polypentapeptide of tropoelastin (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2337-2351 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of a cross-linked polypentapeptide (an insoluble product) by means of a cross-linking reaction between a lysine-containing (1%) polypentapeptide and a glutamic acid-containing (2%) polypentapeptide is described, following description of the synthesis and polymerization of the corresponding pentapeptide p-nitrophenyl esters. The pentapeptide p-nitrophenylesters - H-Val1-Pro2-Gly3-Val4-Gly5-ONp, H-Val1-Pro2-Gly3-Lys4(ε-Z)-Gly5-ONp, and H-Val1-Pro2-Gly3-Glu4-Gly5-ONp - prior to polymerizing and the polypentapeptides prior to cross-linking were analyzed by proton and carbon-13 magnetic resonance. The cross-linking reaction was achieved in the coacervate state by intermolecular primary amide bond formation. The coupling reagent was a water-soluble carbodiimide (1-cyclohexyl-3-(2-N-methylmorpholinoethyl)-carbodiimide-p-toluenesulfonate).
    Additional Material: 3 Ill.
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    The application of polyelectrolyte limiting laws to the helix-coil transition of DNA. VI. The numerical value of the axial phosphate spacing for the coil form (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2385-2390 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is concluded on the basis of comparison of polyelectrolyte theory with published data that the mean phosphate spacing b along the contour axis of an unfolded polynucleotide single strand is in the range 3-4 Å (polyelectrolyte parameter ξ ≈ 2), regardless of temperature, base composition, or extent of stacking. This result is consistent with the low-angle X-ray scattering measurements of Gulik, Inoue, and Luzzati on poly(C). No conclusion may be drawn from this value of b concerning the structure of the chain skeleton or the spatial arrangement of the bases other than that the chain is far from an all-trans local conformation (for which b would be about 6-7 Å, the length of a nucleotide unit). The structural implications, or lack thereof, are discussed in detail in the following paper.
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    Study of thermal denaturation of lysozyme and other globular proteins by light-scattering spectroscopy (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2421-2437 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The technique of intensity correlation light-scattering spectroscopy has been used to accurately determine the extent of physical swelling of lysozyme, ribonuclease, and chymotrypsinogen produced by thermal denaturation. The change in hydrodynamic radius is deduced from direct measurements of the diffusion coefficient, carried out in the temperature range 20° to 70°C at various values of pH in the range 1.0 to 3.0 at ionic strengths of from 0.01 M to 0.2 M. An average radius increase of 18% is observed for lysozyme and ribonuclease, with an estimate of 26% for chymotrypsinogen. Analysis of the pH dependence of the transition temperature leads to the conclusion that the lysozyme charge increases by approximately +2e during unfolding. We have applied this value of the charge increase along with the 18% average radius increase to estimate the electrostatic contribution to the free-energy change for denaturation of lysozyme. The results are consistent with the experimental observation that the transition temperature is nearly independent of ionic strength.
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    Vibrational analysis of peptides, polypeptides, and proteins. II. β-Poly(L-alanine) and β-poly(L-alanylglycine) (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2465-2483 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The normal vibration frequencies of poly(L-alanine) and poly(L-alanylglycine) in the antiparallel chain-pleated sheet structure have been calculated, using the force field for polyglycine I from the previous paper (Biopolymers 15, 2439-2464) plus additional force constants for the methyl group. The agreement with observed ir and Raman bands is very good. This substantiates the excellent transferability of the force field, since polyglycine I was shown to have a rippled-sheet structure. The amide I and amide II mode splittings are very well accounted for by transition dipole coupling, showing that subtle structural differences are sensitively manifested through this mechanism.
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    Conformational energy calculations of enzyme-substrate complexes of lysozyme. I. Energy minimization of monosaccharide and oligosaccharide inhibitors and substrates of lysozyme (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2485-2521 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energy calculations were performed on monosaccharide and oligosaccharide inhibitors and substrates of lysozyme to examine the preferred conformations of these molecules. A grid-search method was used to locate all of the low-energy conformational regions for N-acetyl-β-D-glycosamine (NAG), and energy minimization was then carried out in each of these regions. Three stable positions for the N-acetyl group have ben located, in two of which the plane of the amide unit is normal to the mean plane of the pyranosyl ring. Nine local energy minima were located for the  - CH2OH group. The positions of the two vicinal cis  - OH groups are determined predominantly by interactions with either the  - CH2OH or the N-acetyl group. The most stable conformations of β-N-acetylmuramic acid (NAM) were determined from the study of the low-energy conformations of NAG. In the two stable orientations for the D-lactic acid side chain, the O - C - C′ plane (C′ being the carbon atom of the terminal carboxyl group) was found to be normal to the mean plane of the pyranosyl ring. The low-energy positions for the COOH group of NAM are determined mainly by interactions with neighboring groups.The conformational preferences of the α-anomers of NAG and NAM were also explored. The calculated conformation of the N-acetyl group for α-NAG was quite close to that determined by X-ray analysis. Two of the three lowest energy conformations of α-NAM are similar to the corresponding conformations of the β-anomer. A third low-energy structure, which has a hydrogen bond from the NH of the N-acetyl group to the C=O of the lactic acid group, corresponds very closely to the X-ray structure of this molecule.The preferred conformations of the disaccharides NAG-NAG, NAM-NAG and NAG-NAM were also investigated. Two preferred orientations of the reducing pyranosyl ring relative to the nonreducing ring were found for all of these disaccharides, both of which are close to the extended conformation. In one of these conformations, a hydrogen bond can form between the OH group attached to C3 of the reducing sugar and the ring oxygen of the preceding residue. Each conformation can be stabilized further by a hydrogen bond between the CH2OH (donor) of residue i + 1 and the C=O of residue i (acceptor). The interactions that determine conformations for all oligosaccharides containing both NAG and NAM are shown to be exclusively intraresidue and nearest neighbor interactions, so that it is possible to predict all stable conformations of oligosaccharides containing NAG and NAM in any sequence.
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    An electrostatic model for collagen fibrils. The interaction of reconstituted collagen with Ca++, Na+, and Cl- (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1439-1460 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A model for the electrostatic properties of hydrated collagen fibrils, based on the concept of a “penetrable” protein, has been evaluated through studies of collagen fibrils that had been chemically modified to change their electrostatic properties,. A value of 0.28 ± 0.07 ml/g was found for the intrafibrillar space sterically inaccessible to a molecule that had an equivalent spherical radius of 4.5 Å.The net intrinsic charge on reconstituted collagen is +14 mol/mol under physiological conditions, but decreases, at constant pH, with ionic strength. A value of 7.1 for the pK of the histidine and α-amino groups in reconstituted collagen was obtained through the application of the electrostatic model to this effect.The values obtained for calcium binding parameters for collagen fibrils, under solution conditions in which the nonspecific electrostatic properties of collagen fibrils were eliminated (3-5 M tetramethyl ammonium chloride), were in agreement with values obtained in 0.16 M NaCl solutions calculated through the use of the electrostatic theory. These are 0.73 ± 0.23 and 56.2 ± 12.3 sites per molecule with intrinsic association constants of 1101 ± 386 and 21.4 ± 5.2 M-1, respectively.The model also predicts that an average 4-mV potential difference exists between the reconstituted collagen fibrils and physiological solutions, and that collagen fibrils under such conditions have piezoelectriclike properties.The pattern of interaction of ions with collagen fibrils is such that an allosteric mechanism for the catalytic step in the mineralization of collagen is a possibility.
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    Vibrational spectrum of the unordered polypeptide chain: A Raman study of feather keratin (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1513-1528 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Raman spectra of native and solubilized feather keratin have been obtained, and the amide I and amide III regions have been analyzed by band resolution techniques. The amide I region of the native form indicates that at least 64% of the protein has an antiparallel chain pleated sheet structure, the remainder being unordered. For the solubilized keratin all of the protein is in an unordered state. The amide III region is not as easily analyzed into component contributions. Normal vibration analyses on N-acetyl-L-alanine-N-methylamide support the conclusion that the amide III region is not as satisfactory as the amide I region in characterizing unordered structures. Even in the latter case caution must be used, since the observed amide I band is an average over the conformational distribution in the particular unordered system.
    Additional Material: 11 Ill.
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    The optical birefringence of DNA solutions induced by oscillatory electric and hydrodynamic fields (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1555-1572 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optical birefringence induced in DNA solutions by both oscillating hydrodynamic fields (flow birefringence) and oscillating electric fields (Kerr effect) is measured over a wide frequency range. The observed frequency response of the birefrigence is compared with theories for rigid ellipsoidal particles and for Gaussian chains. DNA at 6 × 105 molecular weight is found to exhibit rigid particle hydrodynamic behavior, while DNA at 5 × 106 molecular weight behaves like a flexible chain. Characterization of the hydrodynamic relaxation spectra for the DNA's by oscillatory flow birefringence allows precise comparison between theory and the experimental Kerr effect response. The dielectric model for DNA contains both permanent and dispersionless induced dipole moments. The dielectric behavior of DNA has the character of a permanent dipole but with anomalous low-frequency dispersion in the Kerr effect. The existing theories do not adequately describe this dispersion. A fluctuation dipole mechanism with relaxation times comparable to those associated with the hydrodynamic motion could possibly demonstrate the observed polar behavior.
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    The effects of isolated N-methylated residues on the conformational characteristics of polypeptides (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1615-1622 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energies have been estimated for the tripeptide fragments L-Ala-N-methyl-L-Ala-L-Ala, L-Ala-L-Ala-N-methyl-L-Ala, L-Ala-Sar-L-Ala, and L-Ala-Gly-N-methyl-L-Ala. The peptide bonds connecting L-Ala and Gly with N-methyl-L-Ala and L-Ala with Sar were permitted to adopt the planar cis as well as the usual trans conformation. Contour maps of the conformational energies of the central residue in these tripeptide fragments are presented and compared to the conformational energy maps previously calculated for unmethylated L-Ala and Gly surrounded by residues which are also unmethylated. In generl it is observed that L-Ala and Gly residues that are either N-methylated in their conformational freedom relative to the same residues in an unmethylated polypeptide chain.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150814
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  • 98
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    Circular dichroism and structure of the complex of acridine orange with poly(L-glutamic acid) (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1655-1667 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Circular dichroism and absorption spectra have been measured on solutions of acridine orange and poly(L-glutamic acid) mixed at two molar ratios of carboxyl group-to-dye, P/D 25 and 0.8, and at different pH's. Characteristic circular dichroism is induced at the absorption bands of acridine orange when the P/D is 25 and the solution is acidic. Another type of circular dichroism is manifest at neutral and alkaline pH when P/D is 0.8. For the induction of the former type of circular dichroism, a helical array of acridine-orange dimers bound to the α-helix is postulated, in which the dye molecular planes are almost perpendicular to the helical axis. Assuming the helical geometry and optical parameters, combined with the observed magnitude of transition electric moment, the rotatory strength of the complex is calculated to the zeroth order approximation, and the observed circular dichroism spectra have been reproduced.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150903
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  • 99
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    Electronic Resource
    Nmr studies of aqueous solutions of tetra and branched peptides. I. Sequence determination of amino-acid residues and the assignment of peptide hydrogen signals (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1643-1653 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sequential determination of glycyl residues (and in several cases different amino-acid residues) in tetra and branched peptides using the nmr technique is reported. The method is based on changes in the nmr spectra of (1) the peptide hydrogens of the different residues and (2) the methylene groups of the glycyl residues, as a result of increasing the rate of the base-catalyzed exchange reaction of the peptide hydrogens. Hence, the spectral changes are pH dependent. However, the exact pH dependence is a function of the location of the residue in the peptide molecule. Thus, it is possible to determine the sequence of the amino-acid residues by studying the changes in the spectra with pH.For peptide molecules of known sequences, the above method can be used for unequivocal assignment of the peptide hydrogen signals.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150902
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  • 100
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    Electronic Resource
    Induced circular dichroism of acridine orange bound to double-stranded RNA and transfer RNA (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1693-1699 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The induced circular dichroism (CD) in the visible region of acridine orange bound to the double-stranded RNA from cytoplasmic polyhedrosis virus and to yeast tRNA has been measured as a function of RNA phosphate-to-dye ratio (P/D), under the conditions of 0.01 M Na+ at pH 7.0. The shape of the CD spectrum of acridine orange bound to the double-stranded RNA was quite different from the spectrum of the dye bound to DNA. The CD spectral features of acridine orange bound to the double-stranded regions in tRNA closely resembled those of the double-stranded RNA-dye complex, suggesting that the dyes bind similarly to the two RNA's. It was further found that the CD spectrum of the tRNA-dye complex at sufficiently high P/D ratios, which is assignable to monomeric, intercalated dye to the base-paired parts in tRNA, is also distinct from the corresponding spectrum of the DNA-dye complex.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150907
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