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  • 1
    Publikationsdatum: 2022-03-17
    Beschreibung: Coccolithophores were collected at 21 stations during summer 2016, from coastal and offshore areas of the Central Mediterranean Sea, to describe the ecology of the coccolithophore community integrating information on their abundance, environmental parameters (salinity, temperature, dissolved oxygen, and fluorescence) and oceanographic data. Emiliania huxleyi dominated the assemblage from surface to intermediate layers, while Florisphaera profunda was more abundant in the deep photic zone. Principal Component Analysis revealed that the distribution of coccolithophore taxa was influenced by environmental parameters: K-strategist taxa were related to warm surface waters, whereas lower photic zone taxa were influenced by the development of a Deep Chlorophyll Maximum and high salinity values, well below the thermocline. These results confirmed that a vertical species zonation, as a typical feature of low-middle latitude, characterizes the Central Mediterranean during summer. The distribution of F. profunda once again confirmed its use as a proxy of Deep Chlorophyll Maximum development and paleoproductivity estimates. Gephyrocapsa spp. (=total Gephyrocapsa), and in particular G. oceanica, were more abundant along the Atlantic Water pathway. Finally, the high concentration value of Helicosphaera carteri, recorded in the Ligurian Sea at an offshore station, suggested an expansion of the opportunist nature of this taxon from coastal environments to the offshore areas characterized by high turbidity and high productivity.
    Beschreibung: Published
    Beschreibung: 101995
    Beschreibung: 4A. Oceanografia e clima
    Beschreibung: JCR Journal
    Schlagwort(e): Living coccolithophores ; Helicosphaera carteri ; Oceanography ; Ecology ; Central Mediterranean Sea ; coccolithophore ecology and oceanography
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2022-10-31
    Beschreibung: Dataset: Share Your Thoughts
    Beschreibung: Oceanographic data, when well-documented and stewarded toward preservation, have the potential to accelerate new science and facilitate our understanding of complex natural systems. The Biological and Chemical Oceanography Data Management Office (BCO-DMO) is funded by the NSF to document and manage marine biological, chemical, physical, and biogeochemical data, ensuring their discovery and access, and facilitating their reuse. The task of curating and providing access to research data is a collaborative process, with associated actors and critical activities occurring throughout the data’s life cycle. BCO-DMO supports all phases of the data life cycle and works closely with investigators to ensure open access of well-documented project data and information. Supporting this curation process is a flexible cyberinfrastructure that provides the means for data submission, discovery, and access; ultimately enabling reuse. Based upon community feedback, this infrastructure is undergoing evaluation and improvement to better meet oceanographic research needs. This poster will introduce the repository and describe some of the strategic enhancements coming to BCO-DMO, and presents an opportunity for you to provide feedback on enhancements yet to come. We invite you to think about your own research workflow of searching and accessing new data for research, and to provide your feedback through the poster’s interactive sections. Your input can help BCO-DMO improve its service to the research community. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/825238
    Beschreibung: NSF Division of Ocean Sciences (NSF OCE) OCE-1924618
    Schlagwort(e): Data management. stakeholder needs ; Oceanography ; BCO-DMO ; Repository ; Community building
    Repository-Name: Woods Hole Open Access Server
    Materialart: Dataset
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
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    Cambridge University Press
    Publikationsdatum: 2022-10-26
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McNichol, A., Key, R., & Guilderson, T. Global ocean radiocarbon programs. Radiocarbon, (2022): 1–13, https://doi.org/10.1017/rdc.2022.17.
    Beschreibung: The importance of studying the radiocarbon content of dissolved inorganic carbon (DI14C) in the oceans has been recognized for decades. Starting with the GEOSECS program in the 1970s, 14C sampling has been a part of most global survey programs. Early results were used to study air-sea gas exchange while the more recent results are critical for helping calibrate ocean general circulation models used to study the effects of climate change. Here we summarize the major programs and discuss some of the important insights the results are starting to provide.
    Beschreibung: Authors received funding from the National Science Foundation OCE-85865400 (APM) and a Woods Hole Oceanographic Technical Staff Award (APM).
    Schlagwort(e): Dissolved inorganic carbon ; Ocean models ; Oceanography ; Radiocarbon
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2022-10-20
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Castorani, M. C. N., Bell, T. W., Walter, J. A., Reuman, D. C., Cavanaugh, K. C., & Sheppard, L. W. Disturbance and nutrients synchronise kelp forests across scales through interacting Moran effects. Ecology Letters, 25(8), (2022): 1854-1868, https://doi.org/10.1111/ele.14066.
    Beschreibung: Spatial synchrony is a ubiquitous and important feature of population dynamics, but many aspects of this phenomenon are not well understood. In particular, it is largely unknown how multiple environmental drivers interact to determine synchrony via Moran effects, and how these impacts vary across spatial and temporal scales. Using new wavelet statistical techniques, we characterised synchrony in populations of giant kelp Macrocystis pyrifera, a widely distributed marine foundation species, and related synchrony to variation in oceanographic conditions across 33 years (1987–2019) and 〉900 km of coastline in California, USA. We discovered that disturbance (storm-driven waves) and resources (seawater nutrients)—underpinned by climatic variability—act individually and interactively to produce synchrony in giant kelp across geography and timescales. Our findings demonstrate that understanding and predicting synchrony, and thus the regional stability of populations, relies on resolving the synergistic and antagonistic Moran effects of multiple environmental drivers acting on different timescales.
    Beschreibung: This study was funded by the U.S. National Science Foundation (NSF) through linked NSF-OCE awards 2023555, 2023523, 2140335, and 2023474 to M.C.N.C., K.C.C., T.W.B., and D.C.R., respectively. The research was initiated during a synthesis working group at the Long Term Ecological Research Network Office and National Center for Ecological Analysis and Synthesis funded under NSF-DEB award 1545288. D.C.R. and L.W.S. were also partly supported by NSF award 1714195, the McDonnell Foundation, and the California Department of Fish and Wildlife Delta Science Program. This project used data developed through the Santa Barbara Coastal Long Term Ecological Research project, funded through NSF-OCE award 1831937.
    Schlagwort(e): Coherence ; Disturbance ; Moran effect ; Nitrate ; North Pacific Gyre Oscillation ; Oceanography ; Population dynamics ; Remote sensing ; Spatial synchrony ; Wavelet transforms
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Publikationsdatum: 2022-10-11
    Beschreibung: The gap in our understanding of Earth is largely because resources have been more readily allocated to exploring the surface of other planets, as well as the fact that mapping beneath water is a complex business, especially at great depths. Water absorbs, reflects and refracts light to such an extent that it is difficult to “see” through it with visual media for more than a few dozen metres. Huge swathes of the oceans, especially those far removed from coastal and national areas, are still inadequately mapped. Environments such as those beneath the polar ice shelves and pack ice-covered oceans are as unfamiliar to us today as the deep ocean was for pioneering ocean-floor mappers over a hundred years ago. But today, with the advent of satellite mapping, multibeam sonar and other advances in remote sensing, we have access to an increasingly broad suite of technologies which make it possible to map the world’s seafloor in more detail than ever.
    Beschreibung: OPENASFA INPUT
    Beschreibung: Published
    Beschreibung: Not Known
    Schlagwort(e): Bathymetry ; Ocean Floor ; Oceanography ; Human impact
    Repository-Name: AquaDocs
    Materialart: Journal Contribution
    Format: pp.65-69
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Publikationsdatum: 2022-09-28
    Beschreibung: This event entitled “Verso la Generazione Oceano” (Towards the Generation Ocean) was the first initiative organized in Italy to present the United Nations Decade of Ocean Science for Sustainable Development (hereinafter the “Decade”). It was held on 22 October 2020 in Milan, Italy. Its goal was to illustrate to the Italian stakeholders the objectives and the plans of the Decade in order to pave the way for the creation of the Generation Ocean campaign (#versolagenerazioneoceano) that will be developed in Italy in 2021. Moreover, this event was organized with the aim to work with different stakeholders and sectors of the society in start developing ideas to be implemented during the UN Decade of Ocean Science for Sustainable Development (2021–2031). This event was planned to take place in May 2020 and the preparatory work started in January 2020. However, due to the Covid-19 outbreak, it was postponed and rescheduled as a digital event to 22 October 2020. Nutrition, oxygen, energy, work, health: everything that allows us to live is linked to the ocean. To promote greater knowledge, conservation and sustainable use of the ocean and its resources, the United Nations declared 2021-2030 "Decade of Ocean Science for Sustainable Development". The Decade aims to mobilise the scientific community, policymakers, business and civil society around a collaborative research and technological innovation programme. It will enable the coordination of research programmes, observation systems, capacity building, maritime spatial planning, and marine risk reduction, to improve the management of ocean and coastal zone resources. The Decade of Ocean Sciences should accelerate the implementation of Sustainable Development Goal 14 for the conservation and sustainable use of the ocean, seas and marine resources. The goal is also to create together “the ocean we need, for the future we want”. With this in mind, the UNESCO Regional Bureau for Science and Culture in Europe and the Intergovernmental Oceanographic Commission of UNESCO (IOC-UNESCO) represented by its Executive Secretary, Dr Vladimir Ryabinin, organised a popular event "Towards the Generation Ocean" to present in Italy the Decade of Ocean Science. In collaboration with various partners, the event aims to initiate a movement that gives voice to the importance of having a resilient ocean, a productive ocean and a healthy ocean. The event focussed on three great challenges: "climate change, food safety and human health". From the No’hma theatre in Milan, “Towards the Generation Ocean” gathered virtually from 9 a.m. to 1 p.m., researchers, professionals, sustainable entrepreneurs, and also chefs, musicians, journalists and experts from various sectors of society. The time to act is now and we must act together! was the message. The event was an initiative dedicated to the role of marine scientific research as an essential tool to ensure the health of the planet and the announcement of a new era represented by the "Generation Ocean". It strived to spread greater awareness of the importance of the ocean and to promote innovative solutions to the challenges we will face in the coming years. At the end of the morning, the event hosted the award ceremony of Oceanthon, the digital hackathon aimed at students, researchers, developers, experts in communication, economics, marketing and design, participating in the design of innovative ideas for the conservation of the ocean. The highlight of the mobilisation event was the presentation of the Oceanthon Prize by Davide Villa, CMO and Board Member of E.ON Italia to the winning “River Cleaner” project by Blue Eco Line startup. The initiative mobilized institutions, companies, non-profit organizations, media and popular people with great interest in the objectives of the Decade. All of them are called to become the promoters of specific initiatives and helper of the IOC as coordinator of the Decade in raising awareness, and facilitating stakeholders’ commitments for the Decade. See related web article: https://en.unesco.org/news/towards-generation-ocean-united-create-ocean-we-need-future-we-want .
    Beschreibung: OPENASFA INPUT For bibliographic purposes this document should be cited as follows: UNESCO-IOC. 2020. Italian Digital Mobilization Event for the United Nations Decade of Ocean Science for Sustainable Development: “Towards the Generation Ocean”, 22 October 2020, Milan, Italy. Paris, UNESCO, (Workshop Reports, 292).
    Beschreibung: Published
    Beschreibung: Not Known
    Schlagwort(e): Oceanography ; Environmental Conservation ; Sustainable Development ; Ocean Decade ; Nutrition ; Oxygen ; Energy ; Work ; Health ; Sustainable use of the ocean and its resources ; Capacity Building ; Coastal zone resources
    Repository-Name: AquaDocs
    Materialart: Report
    Format: 29pp.
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
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    UNESCO | Paris, France
    Publikationsdatum: 2022-09-30
    Beschreibung: In 2017, the UN General Assembly declared the UN Decade of Ocean Science for Sustainable Development (2021-2030). It has entrusted IOC-UNESCO with the design and delivery of the Decade to ensure that ocean science is indeed underpinning sustainable ocean management and the 2030 Sustainable Development Agenda more broadly. Fulfilling its mandate as trustee of the Ocean Decade, as well as delivering on a growing list of additional roles, in an oceanographic space that is both expanding and increasingly crowded, establishes an important opportunity but also an overarching challenge for IOC-UNESCO. In the context of the upcoming UN Decade of the Ocean, the IOC-UNESCO agreed with the Internal Oversight Service (IOS) on the merit of conducting an evaluation of its strategic positioning within the UN system and the broader landscape of ocean-related actors and programmes, taking into account relevant enabling policy frameworks to which the work of the Commission responds.
    Beschreibung: OPENASFA INPUT Published by UNESCO's Internal Oversight Service.
    Beschreibung: Published
    Beschreibung: Not Known
    Schlagwort(e): Evaluation ; International Oceanographic Commission of UNESCO ; Oceanography ; Scientific programmes
    Repository-Name: AquaDocs
    Materialart: Report
    Format: 2pp.
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  • 8
    Publikationsdatum: 2022-10-04
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sandin, S. A., Alcantar, E., Clark, R., de Leon, R., Dilrosun, F., Edwards, C. B., Estep, A. J., Eynaud, Y., French, B. J., Fox, M. D., Grenda, D., Hamilton, S. L., Kramp, H., Marhaver, K. L., Miller, S. D., Roach, T. N. F., Seferina, G., Silveira, C. B., Smith, J. E., Zgliczynski, B. J., & Vermeij, M. J. A. Benthic assemblages are more predictable than fish assemblages at an island scale. Coral Reefs, 41, (2022.): 1031–1043, https://doi.org/10.1007/s00338-022-02272-5.
    Beschreibung: Decades of research have revealed relationships between the abundance of coral reef taxa and local conditions, especially at small scales. However, a rigorous test of covariation requires a robust dataset collected across wide environmental or experimental gradients. Here, we surveyed spatial variability in the densities of major coral reef functional groups at 122 sites along a 70 km expanse of the leeward, forereef habitat of Curaçao in the southern Caribbean. These data were used to test the degree to which spatial variability in community composition could be predicted based on assumed functional relationships and site-specific anthropogenic, physical, and ecological conditions. In general, models revealed less power to describe the spatial variability of fish biomass than cover of reef builders (R2 of best-fit models: 0.25 [fish] and 0.64 [reef builders]). The variability in total benthic cover of reef builders was best described by physical (wave exposure and reef relief) and ecological (turf algal height and coral recruit density) predictors. No metric of anthropogenic pressure was related to spatial variation in reef builder cover. In contrast, total fish biomass showed a consistent (albeit weak) association with anthropogenic predictors (fishing and diving pressure). As is typical of most environmental gradients, the spatial patterns of both fish biomass density and reef builder cover were spatially autocorrelated. Residuals from the best-fit model for fish biomass retained a signature of spatial autocorrelation while the best-fit model for reef builder cover removed spatial autocorrelation, thus reinforcing our finding that environmental predictors were better able to describe the spatial variability of reef builders than that of fish biomass. As we seek to understand spatial variability of coral reef communities at the scale of most management units (i.e., at kilometer- to island-scales), distinct and scale-dependent perspectives will be needed when considering different functional groups.
    Beschreibung: This research and the larger efforts of Blue Halo Curacao were supported by funding from the Waitt Institute and with permissions from the Government of Curacao, Ministry of Health, Environment, and Nature. Field logistics were further supported by the Waitt Institute vessel crew, CARMABI Foundation, The Dive Shop Curacao, and Dive Charter Curacao.
    Schlagwort(e): Community ecology ; Oceanography ; Anthropogenic impacts ; Spatial variation ; Spatial autocorrelation
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
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    Woods Hole Oceanographic Institution
    Publikationsdatum: 2022-08-26
    Beschreibung: A 41-page memoir of Bigelow's life, beginning with his childhood in Massachusetts and following his many research and other trips around the world. The volume ends with an anecdote from 1963. Stories are told in a conversational, friendly style and include names of family, friends, and colleagues, as well as locations and some experiments that were conducted.
    Schlagwort(e): Autobiographies--20th Century ; Oceanography
    Repository-Name: Woods Hole Open Access Server
    Materialart: Text
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  • 10
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    Woods Hole Oceanographic Institution
    Publikationsdatum: 2022-08-29
    Beschreibung: A speech by Henry Bryant Bigelow during a Noon Luncheon at Woods Hole Oceanographic Institution. Recording includes an introduction by Adam Smith and comments by Columbus Iselin, Alfred Redfield, and Dr. H. Graham of the U. S. Fish and Wildlife Service
    Schlagwort(e): Oceanography ; Speeches ; Bigelow, Henry Bryant, 1879-1967 ; Iselin, Columbus O'Donnell, 1904-1971 ; Redfield, A. C. (Alfred Clarence), 1890-1983 ; U. S. Fish and Wildlife Service
    Repository-Name: Woods Hole Open Access Server
    Materialart: Recording, oral
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  • 11
    Publikationsdatum: 2022-08-19
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Zitterbart, D., Bocconcelli, A., Ochs, M., & Bonnel, J. TOSSIT: a low-cost, hand deployable, rope-less and acoustically silent mooring for underwater passive acoustic monitoring. HardwareX, 11, (2022): e00304, https://doi.org/10.1016/j.ohx.2022.e00304.
    Beschreibung: Passive Acoustic Monitoring (PAM) has been used to study the ocean for decades across several fields to answer biological, geological and meteorological questions such as marine mammal presence, measures of anthropogenic noise in the ocean, and monitoring and prediction of underwater earthquakes and tsunamis. While in previous decades the high cost of acoustic instruments limited its use, miniaturization and microprocessor advances dramatically reduced the cost for passive acoustic monitoring instruments making PAM available for a broad scientific community. Such low-cost devices are often deployed by divers or on mooring lines with a surface buoy, which limit their use to diving depth and coastal regions. Here, we present a low-cost, low self-noise and hand-deployable PAM mooring design, called TOSSIT. It can be used in water as deep as 500 m, and can be deployed and recovered by hand by a single operator (more comfortably with two) in a small boat. The TOSSIT modular mooring system consists of a light and strong non-metallic frame that can fit a variety of sensors including PAM instruments, acoustic releases, additional power packages, environmental parameter sensors. The TOSSIT’s design is rope-less, which removes any risk of entanglement and keeps the self-noise very low.
    Beschreibung: The development of the TOSSIT mooring was supported by a Woods Hole Oceanographic institution Innovative Technology Award (Award number 25226). TOSSIT deployment in Argentina was supported by a Woods Hole Oceanographic Institution Mary Sears visitor award (Award number 24700) and TOSSIT deployments during SBCEX were funded by the Office of Naval Research Task Force Ocean (ONR TFO, Award number: N000141912627). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
    Schlagwort(e): Ocean ambient noise ; Mooring systems ; Soundscape ; Underwater sound ; Bioacoustics ; Oceanography ; Acoustical Oceanography
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 12
    Publikationsdatum: 2022-06-17
    Beschreibung: Sea wave monitoring is key in many applications in oceanography such as the validation of weather and wave models. Conventional in situ solutions are based on moored buoys whose measurements are often recognized as a standard. However, being exposed to a harsh environment, they are not reliable, need frequent maintenance, and the datasets feature many gaps. To overcome the previous limitations, we propose a system including a buoy, a micro-seismic measuring station, and a machine learning algorithm. The working principle is based on measuring the micro-seismic signals generated by the sea waves. Thus, the machine learning algorithm will be trained to reconstruct the missing buoy data from the micro-seismic data. As the micro-seismic station can be installed indoor, it assures high reliability while the machine learning algorithm provides accurate reconstruction of the missing buoy data. In this work, we present the methods to process the data, develop and train the machine learning algorithm, and assess the reconstruction accuracy. As a case of study, we used experimental data collected in 2014 from the Northern Tyrrhenian Sea demonstrating that the data reconstruction can be done both for significant wave height and wave period. The proposed approach was inspired from Data Science, whose methods were the foundation for the new solutions presented in this work. For example, estimating the period of the sea waves, often not discussed in previous works, was relatively simple with machine learning. In conclusion, the experimental results demonstrated that the new system can overcome the reliability issues of the buoy keeping the same accuracy.
    Beschreibung: Assist in Gravitation and Instrumentation srl Istituto Nazionale di Geofisica e Vulcanologia
    Beschreibung: Published
    Beschreibung: 798167
    Beschreibung: 4A. Oceanografia e clima
    Beschreibung: JCR Journal
    Schlagwort(e): sea swell ; machine learning ; ocean waves ; micro-seismic data ; sea state ; sea wave period ; buoy ; Marine Science ; Oceanography
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 13
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    Scientific Committee on Oceanic Research | Newark, Delaware, USA
    Publikationsdatum: 2022-09-17
    Beschreibung: This proceeding summarizes the discussions during the 2021 SCOR Annual Meeting held virtually between the 26-28 of October of 2021. Following a decision from the SCOR Executive, this proceeding also provides the links for all the background information for the meeting, including the proposals for new working groups, the reports from current SCOR working groups, projects, capacity development activities, and the reports of affiliated and partner organizations all of which were traditionally included in the SCOR Annual meeting background book until 2019. All of these can also be accessed online through the SCOR website at: https://scor-int.org/events/scor-annual-meeting-2021/. The SCOR 2021 Annual Meeting was attended by more than 200 participants from 56 countries representing all continents. Forty Nominated members from 24 SCOR National Committees and the three affiliated bodies to the Executive Committee (IABO, IAPSO, IAMAS) attended the meeting. All SCOR Working Groups, research, infrastructural, and affiliated projects, along with the affiliated and partner organizations reported on their activities. Some of the main highlights of the SCOR 2021 Annual Meeting include: (1) the approval of three new Working Groups (WGs), (2) to secure NSF funding to continue to support working group and project activities, and (3) the endorsement of SCOR working group and project activities by the UN Decade of Ocean Science for Sustainable Development. The three new WGs proposals approved were: (1) Coupling of ocean-ice-atmosphere processes: from sea-Ice biogeochemistry to aerosols and Clouds (CIce2Clouds), co-chaired by Nadja Steiner (Canada) and Megan Willis (USA), (2) CoNCENSUS: Advancing standardisation of COastal and Nearshore demersal fish visual CENSUS techniques, co-chaired by Anthony Bernard (South Africa) and Rick D. Stuart-Smith (Australia), and (3) Mixotrophy in the Oceans – Novel Experimental designs and Tools for a new trophic paradigm (MixONET), co-chaired by Aditee Mitra (UK) and George McManus (USA). SCOR continued to support capacity development activities by extending support to the visiting scholars approved for travel in 2020 and approving four new scholars to travel in 2021 or until travel is possible again. SCOR has continued to approve funding applications from conference organizers to support travel for scientists from developing countries to attend these conferences when they are rescheduled. These commitments will be honored by SCOR when travel is reinitiated. The 2022 SCOR meeting is scheduled for the first week of October 2022 in Busan, Korea, hosted by the Korean Institute of Science and Technology (KIOST), and will follow the PICES meeting which will take place in the same location the week before. The 2023 SCOR meeting is scheduled to take place in Guayaquil, Ecuador, hosted by the Instituto Oceanográfico y Antártico de la Armada del Ecuador (INOCAR) between September-October. Narrated presentations reporting on SCOR project and working group activities and progress in 2021 can also be found in the SCOR YouTube channel. https://www.youtube.com/channel/UCv-dZLizFYDOC2UTweiWj0Q/videos
    Beschreibung: Published
    Beschreibung: Non Refereed
    Schlagwort(e): Marine sciences ; Oceanography
    Repository-Name: AquaDocs
    Materialart: Book/Monograph/Conference Proceedings
    Format: 62pp.
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  • 14
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    IOC of UNESCO | Paris, France
    Publikationsdatum: 2022-09-21
    Beschreibung: World Oceans Day is celebrated every year on 8 June to acknowledge the importance of the oceans in the global environment. This international day observed by the United Nations serves as an occasion to raise awareness on the protection of the oceans and on the sustainable use of its resources, as well as to discuss ways to further develop and share scientific knowledge on ocean related issues. This year, the Intergovernmental Oceanographic Commission of UNESCO, together with the Ocean and Climate Platform, dedicates this special day to the key role played by the ocean in maintaining a healthy environment. Held under the theme “Healthy Ocean, Healthy Planet”, World Oceans Day 2016 gives special focus on the prevention of plastic pollution.
    Beschreibung: Norwegian Ministry of Foreign Affairs
    Beschreibung: OpenASFA INPUT
    Beschreibung: Published
    Beschreibung: Non Refereed
    Schlagwort(e): World Oceans Day ; Oceanography ; Oceans ; Climate Change ; Environmental Conservation ; Member States ; Ocean Sustainability ; Paris Agreement ; Ocean Acidification ; Ocean Science communication
    Repository-Name: AquaDocs
    Materialart: Report
    Format: 19pp.
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  • 15
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    UNESCO-IOC | Paris, France
    Publikationsdatum: 2022-09-21
    Beschreibung: Capacity building is an essential tenet of IOC’s mission: It enables all Member States to participate in and benefit from ocean research and services that are vital to sustainable development and human welfare on the planet. This Strategy’s vision identifies capacity development as the primary catalyst through which IOC will achieve its four high level objectives in the current 2014–2021 IOC Medium-Term Strategy. Over the past 55 years Member States have derived numerous benefits from IOC’s capacity development from the first International Indian Ocean Expedition to the revitalisation of African marine science coordination and establishment of the global tsunami warning network including the monitoring/forecasting networks that save lives (see addendum, section III). Reinforced partnerships between IOC and its Member States, other UN agencies, donors, and the scientific community have been the cornerstone of this success. During this period, the transformation of ocean science capabilities, accelerating threats to ocean health and ecosystem services, and the growing challenge of sustainable development require the IOC and its Member States to accelerate the pace of IOC capacity development. Resource constraints, both staff and funding, limit IOC’s ability to mobilise the necessary partnerships to address Member State science and services that will enhance human welfare and sustainable economic development. In 2014, the UN General Assembly adopted the Oceans and the law of the sea Reso lution   (A/RES/69/245) which reiterated the essential need for cooperation, including through capacity building and transfer of marine technology, “to ensure that States, especially developing countries, in particular the least developed countries and small island developing States, as well as coastal African States, are able both to implement the Convention1 and to benefit from the sustainable development of the oceans and seas, as well as to participate fully in global and regional forums and processes dealing with oceans and law of the sea issues.” 2015 will mark the establishment of the Post-2015 Development Agenda, which is expected to be integrated as Sustainable Development Goals (SDGs). IOC has a unique international niche in ocean science, services and capacity development: (a) fostering international cooperation for sustained observations of the oceans; (b) generating oceanographic data and information products and services and interaction between research, operational, user communities and decision-makers in order to derive maximum societal benefit from new knowledge to achieve IOC’s High Level Objectives. The IOC will mainstream its natural and social science approach to capacity development in its Member States and, in particular, in Priority Africa, SIDS and Gender Equality. This strategic framework provides six outputs and numerous activities that are elaborated in detail below. These outputs call for investing in people and the institutions of which they are a part, enhancing access to scientific tools and methodologies, reinforcing IOC’s capabilities to provide services to Member States, enhancing the communication between scientific and policy makers communities, expanding ocean literacy in civil society and mobilising resources to accomplish these goals. While this framework provides general guidance on elements of an implementation plan yet to be developed, elevating IOC’s impact to the scale required is contingent on: • Reinforcing and valuing IOC staff at global and regional levels and, where necessary, participating national ocean scientific and governance institutions; • Integrating IOC global and regional mechanisms to rapidly expand Member State participation in IOC programmes: - Empowering IOC regional sub-commissions and other subsidiary bodies o engage with Member States, expanding collaboration and capacity development (including transfer of marine technology) on their coastal and marine affairs priorities - Strengthening global science programmes to increase scientific engagement with Member State coastal and marine priorities; • Recommitting to partnerships through the IOC with its Member States, UN organizations and other agencies, scientific community and civil society; • Mobilizing resources, e.g., personnel, funds, knowledge, and observing networks, to deliver the capacity development on which science, services and human communities depend; and • Continued attention to “enabling institutional conditions” as identified in discussions on “The Future of IOC”. The conclusions identify elements of a draft work plan including conducting needs assessments to establish CD work plans, mobilizing associated resources and enhanced communication and collaboration.
    Beschreibung: OPENASFA INPUT
    Beschreibung: Published
    Beschreibung: Refereed
    Schlagwort(e): Oceanography ; Capacity Development ; Scientific cooperation ; Member States ; Economic development ; UN Convention on the Law of the Sea ; Sustainable Development Goals ; Gender Equality ; Ocean Health
    Repository-Name: AquaDocs
    Materialart: Report
    Format: 64pp.
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  • 16
    Publikationsdatum: 2022-12-06
    Beschreibung: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 48(17), (2021): e2021GL094128, https://doi.org/10.1029/2021GL094128.
    Beschreibung: Ocean warming is causing declines of coral reefs globally, raising critical questions about the potential for corals to adapt. In the central equatorial Pacific, reefs persisting through recurrent El Niño heatwaves hold important clues. Using an 18-year record of coral cover spanning three major bleaching events, we show that the impact of thermal stress on coral mortality within the Phoenix Islands Protected Area (PIPA) has lessened over time. Disproportionate survival of extreme thermal stress during the 2009–2010 and 2015–2016 heatwaves, relative to that in 2002–2003, suggests that selective mortality through successive heatwaves may help shape coral community responses to future warming. Identifying and facilitating the conditions under which coral survival and recovery can keep pace with rates of warming are essential first steps toward successful stewardship of coral reefs under 21st century climate change.
    Beschreibung: Support was provided by the US National Science Foundation (NSF) 1737311 to A. L. Cohen; The Atlantic Donor Advised Fund to A. L. Cohen; a Woods Hole Oceanographic Institution post-doctoral scholarship to M. D. Fox; the Robertson Foundation, The Prince Albert Foundation, the New England Aquarium, and the Akiko Shiraki Dynner Fund.
    Schlagwort(e): Coral reefs ; Thermal stress ; ENSO ; Adaptation ; Oceanography ; Central Pacific
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 17
    Publikationsdatum: 2022-11-04
    Beschreibung: Recalling IOC-Resolution XXX-3 and in accordance with 207 EX/Dec.5.II.A, this report provides a summary of a recently completed evaluation, namely: Internal Oversight Service (IOS) Evaluation of the Strategic positioning of the Intergovernmental Oceanographic Commission (IOC-UNESCO).
    Beschreibung: Item 9 of the provisional agenda of the Executive Board of UNESCO (212 EX/9). OPENASFA INPUT
    Beschreibung: Published
    Beschreibung: Non Refereed
    Schlagwort(e): International Oceanographic Commission of UNESCO ; Strategic position ; IOC-UNESCO ; Evaluation ; Scientific programmes ; Oceanography
    Repository-Name: AquaDocs
    Materialart: Report
    Format: 9pp.
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  • 18
    Publikationsdatum: 2022-11-04
    Beschreibung: The Intergovernmental Oceanographic Commission (IOC-UNESCO) has functional autonomy within UNESCO. It is the only UN body specializing exclusively in ocean science, ocean observation, ocean data and information exchange and dedicated ocean services such as Tsunami Early Warning Systems. In 2019, UNESCO’s Intergovernmental Oceanographic Commission was tasked to lead the UN Decade of the Ocean. This opportunity, combined with a fast-evolving ecosystem of international actors in an expanding and increasingly crowded ocean policy and marine science space, prompted IOC-UNESCO to request an evaluation of IOC-UNESCO with a focus on its strategic positioning within the UN system and the broader landscape of ocean-related actors and programmes to meet the high demand for sound ocean science in an oceanographic space. The evaluation found that IOC-UNESCO is a valued partner for Member States as well as other international and national actors, and indispensable for strengthening capacities and providing the data and technical information on ocean science policy that serves as a basis for national level data. IOC-UNESCO has been most successful in providing contributions to UN Frameworks and Conventions (e.g. UNFCCC, Sendai and CBD), in acting as a neutral platform to discuss the increasingly relevant issue of ocean health and climate change, in bringing Member States together and fostering exchanges between governments and scientists, as well as in providing to the extended oceanographic community access to data, information and science. However, strategic advocacy at the national level, engagement at the regional level, and resourcing and visibility of gender equality and women’s empowerment in the ocean space within and outside IOC-UNESCO are among the areas where further improvements are required. The establishment of the Decade of Ocean Science for Sustainable Development is the most important strategic institutional achievement of IOC-UNESCO in recent years. It is an important opportunity, but the absence of a clearly defined results framework and inadequate resources could jeopardize its success. Furthermore, it still needs to be determined how to best exploit IOC-UNESCO’s data and knowledge base and how UNESCO can best support the Decade, among other through intersectoral work.
    Beschreibung: OPENASFA INPUT
    Beschreibung: Published
    Beschreibung: Refereed
    Schlagwort(e): Evaluation ; Oceanography ; International Oceanographic Commission of UNESCO ; Scientific programmes
    Repository-Name: AquaDocs
    Materialart: Report
    Format: 61pp.
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  • 19
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    Louisiana Universities Marine Consortium | Chauvin, LA
    In:  http://aquaticcommons.org/id/eprint/15916 | 30 | 2015-03-30 17:03:43 | 15916 | Louisiana Universities Marine Consortium (LUMCON)
    Publikationsdatum: 2022-04-20
    Beschreibung: The Nutrient Enhanced Coastal Ocean Productivity (NECOP) Program is a component of NOAA's Coastal Ocean Program. The central hypothesis of this research is: Anthropogenic nutrient inputs have enhanced coastal ocean productivity with subsequent impacts on coastal ocean water quality, living resource yields, and the global marine carbon cycle. The initial study area for this program is the Mississippi/Atchafalaya River Outflow and adjacent Louisiana shelf region.
    Schlagwort(e): Oceanography
    Repository-Name: AquaDocs
    Materialart: monograph
    Format: application/pdf
    Format: application/pdf
    Format: 85
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  • 20
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    South Pacific Applied Geoscience Commission | Suva, Fiji
    In:  http://aquaticcommons.org/id/eprint/25859 | 20823 | 2018-10-11 09:32:49 | 25859 | South Pacific Applied Geoscience Commission
    Publikationsdatum: 2022-09-13
    Beschreibung: Seabed mapping was completed using a Reson 8101 multibeam system to delineate the seabed morphology in the vicinity of the wreck USS Mississinewa located in water depths of around 40 m in Ulithi Atoll. A second area was mapped in Ulithi Atoll along the NE eastern margin of the lagoon from Masu to Asor island. Results of this mapping did not delineate any extraordinary feature other than the existing morphology of the seabed. The most interesting feature seen were elliptical-shaped mounds which may imply bi-directional bottom currents of similar magnitudes. The mapping of Yap harbour was also completed. These results have been presented in map form as contours and as soundings. The results of the mapping for Yap and Ulithi are available in GIS format. Digital side-scan imagery for all surveyed lines for both Ulithi and Yap harbour were collected and is presently only archived for processing should this facility become available. Conclusions are: The dataset for Ulithi lagoon provides excellent baseline information for long-term assessment of the impacts of the wrecks on the environment. Detailed maps and visualisation of seabed wrecks provides an opportunity for tourism e.g. a potential dive sites. The completion of the multibeam survey of Yap harbour and approaches provides for excellent baseline data for future infrastructure development. Recommendations are: Updating of the existing topographic map for Yap to account for expanding infrastructure in Colonia harbour should be completed. The use of IKONOS imagery in GIS provides an immediate solution for new and up-to-date maps for development planning.
    Schlagwort(e): Oceanography
    Repository-Name: AquaDocs
    Materialart: monograph
    Format: application/pdf
    Format: application/pdf
    Format: 27pp.
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  • 21
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    In:  aqdchief@seafdec.org.ph | http://aquaticcommons.org/id/eprint/18703 | 17342 | 2015-11-15 16:07:14 | 18703 | Southeast Asian Fisheries Development Center, Aquaculture Department
    Publikationsdatum: 2022-08-02
    Beschreibung: Results indicated that a female having eggs with an average diameter of 〈 0.7 mm did not respond well to the hormone injections.
    Schlagwort(e): Aquaculture ; Biology ; Induced breeding ; Fish culture ; Chanos chanos
    Repository-Name: AquaDocs
    Materialart: article
    Format: application/pdf
    Format: application/pdf
    Format: 1-3
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  • 22
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    Training Department, Southeast Asian Fisheries Development Center | Samut Prakan, Thailand
    In:  http://aquaticcommons.org/id/eprint/26320 | 23782 | 2019-03-27 07:10:12 | 26320 | Southeast Asian Fisheries Development Center, Training Department
    Publikationsdatum: 2022-08-02
    Beschreibung: Our study provides new information on the physical characteristics of watermass in the South China Sea. We analyzed the temperature, salinity and density profiles to determine the effect of the NE monsoon on the variability of the physical properties of watermass, in the Gulf of Thailand and the east coast of Peninsular Malaysia. CTD data were obtained from both the M.V. SEAFDEC cruises conducted before (September 1995) and after (April 1996) the northeast (NE) monsoon season. We concluded that the NE monsoon caused the variability of the physical properties of watermasses, in the study area, slightly. We observed the movement of the thermocline, halocline and pycnocline layers from deeper depth to shallower depth, before and after the NE monsoon season, respectively. This movement indicates the possible occurrence of downwelling and upwelling processes in the region.
    Schlagwort(e): Oceanography ; Water masses ; CTD observations ; Physical oceanography ; Monsoons ; South China Sea ; Gulf of Thailand ; Malaysia
    Repository-Name: AquaDocs
    Materialart: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 1-5
    Format: 5
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  • 23
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    Training Department, Southeast Asian Fisheries Development Center | Samut Prakan, Thailand
    In:  http://aquaticcommons.org/id/eprint/26323 | 23782 | 2019-03-28 08:22:52 | 26323 | Southeast Asian Fisheries Development Center, Training Department
    Publikationsdatum: 2022-08-02
    Beschreibung: Two batches of eighty sediment samples were cut from the first centimeter of sediment cores collected during September 1995, representing the pre-monsoon period, and April 1996, representing the post-monsoon period, at the same location. The samples were collected within the waters of the Gulf of Thailand and the eastern board of Peninsular Malaysia. The sediment samples were analyzed for their sedimentological characteristics using the techniques of sieving and laser diffraction. In general the sediments of the Gulf of Thailand are finer, better sorted, more peaked than that of the Malaysian waters. Skewness of sediments from Thailand waters was more positively skewed than the Malaysian sediments for the pre-monsoon period but tended to be more negatively skewed for the post-monsoon period. It is also interesting to note that in general, the sediments collected during the post-monsoon period are finer, better sorted, more positively skewed and less peaked than the sediments collected during the pre-monsoon period. This is true for both the sediments collected from the Gulf of Thailand and the Malaysian waters. Near-shore sediments were also found to be the coarsest, followed by the off-shore sediments.
    Schlagwort(e): Oceanography ; Sediment sampling ; Sedimentology ; Sediment analysis ; South China Sea ; Gulf of Thailand ; Malaysia
    Repository-Name: AquaDocs
    Materialart: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 34-53
    Format: 20
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  • 24
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    Training Department, Southeast Asian Fisheries Development Center | Samut Prakan, Thailand
    In:  http://aquaticcommons.org/id/eprint/26404 | 23782 | 2019-04-11 06:46:38 | 26404 | Southeast Asian Fisheries Development Center, Training Department
    Publikationsdatum: 2022-08-02
    Beschreibung: Water samples off Sabah, Sarawak and Brunei Darussalam were collected during July–August 1996 and May 1997 and analyzed for dissolved and particulate cadmium, copper, iron, lead and nickel. Dissolved metals were coprecipitated with cobalt-APDC while particulate metals were digested with aqua regia and hydrofluoric acid. The concentrations of metals were measured using graphite furnace atomic absorption spectrophotometer. Concentrations of cadmium, copper, lead and nickel were in the same concentration ranges of unpolluted coastal water elsewhere except for some high concentrations of cadmium at some stations offshore. Iron concentrations were much higher than other regions, and the concentrations were about twenty times those found in the Gulf of Thailand and east coast of Malay Peninsula. High concentrations of these five metals in the offshore area in the July-August sampling possibly came from the Indonesian water flowing northward due to the influence of the wind from the south.
    Schlagwort(e): Oceanography ; Pollution monitoring ; Industrial wastes ; Marine pollution ; Heavy metals ; Coastal waters ; Trace metals ; South China Sea ; Malaysia ; Sarawak ; Sabah ; Brunei Darussalam
    Repository-Name: AquaDocs
    Materialart: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 129-145
    Format: 17
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  • 25
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    Training Department, Southeast Asian Fisheries Development Center | Samut Prakan, Thailand
    In:  http://aquaticcommons.org/id/eprint/26411 | 23782 | 2019-04-10 07:46:55 | 26411 | Southeast Asian Fisheries Development Center, Training Department
    Publikationsdatum: 2022-08-02
    Beschreibung: Collaborative cruises in the South China Sea around the coast of Sarawak, Brunei and Sabah were conducted in the pre-monsoon (October, 1996) and the post-monsoon (June, 1997) periods on board MV SEAFDEC. The microplankton from 79 sampling stations consisted of more than 200 taxa consisting predominantly of blue green algae (3 species), diatoms (〉 90 species), dinoflagellates (〉 70 species) and microzooplankton (〉 20 groups). Among the microplankton collected, three species of blue green (Trichodesmium erythraeum, T. thiebautii, Richelia sp.) and numerous diatom species were dominant. The dominant diatom species comprised of Chaetoceros diversum, C. peruvianum, C. laciniosus, Thalassionema frauenfeldii, Bacteriastrum comosun, Coscinodiscus sp. and Rhizosolenia alata; while those of dinoflagellates consisted of Ceratium fusus, C. arcuatum, C. teres, Protoperidinium sp., Protoceratium sp., Ceratocorys sp. and Alexandrium sp. The genera Chaetoceros, Rhizosolenia, Bacteriastrum and Ceratium were found to contain a wide range of species. The total microplankton densities ranged from 0.74 x 106 to 7.94 x 106 individuals / m3 and from 0.16 x 106 to 1.25 x 106 individuals / m3 during the premonsoon and postmonsoon periods respectively. The presence of the dinoflagellate species of Ceratium, Protoperidinium and Alexandrium were detected in considerable amounts at coastal and intermediate middle waters of the South China Sea. Blooms of Rhizosolenia alata and Trichodesmium sp. occurred during the premonsoon period. The microzooplankton consisted of more than 20 species dominated by copepod nauplii (〉 50% of total microzooplankton count), radiolerians, foraminiferas and protozoans; most of the zooplankton species were dominant in nearshore and intermediate middle waters of the South China Sea.
    Schlagwort(e): Oceanography ; Dominant species ; Species diversity ; Zooplankton ; Biological sampling ; South China Sea ; Malaysia ; Sarawak ; Sabah ; Brunei Darussalam ; Trichodesmium ; Bacillariophyta ; Trichodesmium thiebautii ; Richelia
    Repository-Name: AquaDocs
    Materialart: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 197-223
    Format: 27
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  • 26
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    Training Department, Southeast Asian Fisheries Development Center | Samut Prakan, Thailand
    In:  http://aquaticcommons.org/id/eprint/26325 | 23782 | 2019-03-28 08:20:36 | 26325 | Southeast Asian Fisheries Development Center, Training Department
    Publikationsdatum: 2022-08-02
    Beschreibung: The trace metal distribution in the surface sediments of the Gulf of Thailand and the South China Sea were studied. Samples were obtained from two cruises of the MV SEAFDEC Total metal content were measured in the 63mm fraction of dried sediment. For the first cruise (Pre-Northeast monsoon) results, metal concentration ranges were between 0.41- 0.19mgg-1Cd, 10-36mgg-1Cu, 7.02-27.8mgg-1Pb, 15.3-352mgg-1Zn, 20.5-122mgg-1 Cr, 209-720mgg-1Mn, 0.79-5.96%Al and 0.71-2.82%Fe. Similar results were obtained for the second cruise (Post-Northeast monsoon) results, with metal concentrations in the range of 0.10-0.94 mgg-1Cd, 10.3-61.4 mgg-1Cu, 5.24-78.2 mgg-1Pb, 18.1-98 mgg-1Zn, 21.1-101 mgg-1Cr, 117-797 mgg-1Mn, 1.89-7.22 %Al and 0.70-2.38 %Fe. The concentrations of Al, Cr, Cu and Mn were significantly higher in the Gulf of Thailand in the pre-monsoon while concentrations of Fe, Cd and Zn were similar for both areas. For the postmonsoon Al, Cu and Mn concentrations were higher in Gulf sediments. Differences in metal concentrations were noted between the pre- and the post monsoon samples. Fe, Cr and Mn concentrations were generally higher in the pre-monsoon period for both areas but the distribution of Pb was higher in the post-monsoon while Zn and Cu distribution differed between the Gulf and the South China Sea areas. However normalisation of the metal data to aluminium content of the sediment showed generally uniform concentration of the metals studied over most of the area studied. Some enrichment by Cu in sediments from two sampling stations in the upper Gulf of Thailand is indicated by Cu:Al ratios exceeding normal crustal abundances of these metals. However low Cu:Al ratios in sediments from some areas of the South China Sea may indicate depletion of Cu in the sediments.
    Schlagwort(e): Oceanography ; Trace metals ; Sediment analysis ; Monsoons ; South China Sea ; Gulf of Thailand ; Malaysia
    Repository-Name: AquaDocs
    Materialart: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 73-85
    Format: 13
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  • 27
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    Training Department, Southeast Asian Fisheries Development Center | Samut Prakan, Thailand
    In:  http://aquaticcommons.org/id/eprint/26328 | 23782 | 2019-03-28 08:52:39 | 26328 | Southeast Asian Fisheries Development Center, Training Department
    Publikationsdatum: 2022-08-02
    Beschreibung: Petroleum hydrocarbon in water samples and sediments collected during the Pre-Southwest Monsoon Cruise in the Gulf of Thailand and Eastern Peninsular Malaysia in April-May 1996 point out that land-based and sea-based sources were both important. High concentration (〉 0.5 mg/l) found in coastal water of the northern part and western part near Songkhla-Pattani could be derived from land-based sources. Elevated concentration of petroleum hydrocarbons in seawater and residuals in sediments of the central area of the Gulf could be originated from offshore activities. However physical oceanography of the Gulf could also play very important roles in redistribution, dispersion and accumulation of petroleum hydrocarbon in the water.
    Schlagwort(e): Oceanography ; Pollution ; Pollution monitoring ; Marine pollution ; Sediment analysis ; Petroleum hydrocarbonsSouth China Sea ; Gulf of Thailand ; Malaysia
    Repository-Name: AquaDocs
    Materialart: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 105-110
    Format: 6
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  • 28
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    Training Department, Southeast Asian Fisheries Development Center | Samut Prakan, Thailand
    In:  http://aquaticcommons.org/id/eprint/26401 | 23782 | 2019-04-10 08:38:29 | 26401 | Southeast Asian Fisheries Development Center, Training Department
    Publikationsdatum: 2022-08-02
    Beschreibung: Dissolved carbonate species in seawater are determined from pH and total alkalinity. The data clearly pointed out the significance of Rajang River as a source of organic matters that were subsequently decomposed and cause CO2 gas to evade from nearshore water in its vicinity into the atmosphere while most offshore surface water was the sink of atmospheric CO2. The total alkalinity profiles indicated dissolution of carbonate minerals, believed to be high magnesian calcite, below 500 m, which reinforce CO2 storing capacity of these waters.
    Schlagwort(e): Oceanography ; Dissolved inorganic carbon ; Carbonates ; Chemical oceanography ; Carbon dioxide ; South China Sea ; Malaysia ; Sarawak ; Sabah
    Repository-Name: AquaDocs
    Materialart: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 62-94
    Format: 33
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  • 29
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    Training Department, Southeast Asian Fisheries Development Center | Samut Prakan, Thailand
    In:  http://aquaticcommons.org/id/eprint/26407 | 23782 | 2019-04-11 07:04:56 | 26407 | Southeast Asian Fisheries Development Center, Training Department
    Publikationsdatum: 2022-08-02
    Beschreibung: Primary production in the South China Sea, off Sabah, Sarawak and Brunei Darussalam was determined from in situ fluorescence, light intensity and the uptake of radioactive carbon incubation on the MV.SEAFDEC cruise in July-August, 1996. Depth integrated primary production varies between 0.13–0.88 gC/m2/day in the coastal zone and 0.23–0.89 gC/m2/day in the open sea. The magnitude was high along the north off Brunei Darussalam and Sabah and gradually decreased with depth. The elevated daily primary production was generally found at the sea surface mixed layer and subpycnocline chlorophyll maximum. The decreasing virtual light intensity was tending to restrict the vertical distribution in daily primary production with accompanied by the chlorophyll-a concentration.
    Schlagwort(e): Oceanography ; Chlorophylls ; Light intensity ; Fluorescence ; Primary production ; South China Sea ; Malaysia ; Sarawak ; Sabah ; Brunei Darussalam
    Repository-Name: AquaDocs
    Materialart: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 165-176
    Format: 12
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  • 30
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    Woods Hole Oceanographic Institution
    Publikationsdatum: 2022-10-21
    Beschreibung: Presented at Sea Education Association, Woods Hole, MA, February 26, 2020
    Beschreibung: Ocean 101, engaging classes to help SEA students understand the frontiers of ocean climate science. This particular class focuses on data management in oceanography. Covered topics are the importance of open data, the data life cycle and F.A.I.R. Principles. The interactive part consists of creating the content for a data management plan and applying general data management practices.
    Schlagwort(e): Oceanography ; Data management practices ; Open data ; Teaching ; Outreach
    Repository-Name: Woods Hole Open Access Server
    Materialart: Presentation
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Pure and applied geophysics 117 (1979), S. 943-957 
    ISSN: 1420-9136
    Schlagwort(e): Oceanography ; Dish pan experiments ; Dynamics of oceans ; Laboratory modellings of ocean currents
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The Loop Current of the Gulf of Mexico is simulated in the laboratory. A circular tank is filled with water and is placed off-center on a rotating table and the flow field is generated by injecting and withdrawing water at two openings on the wall. The free surface becomes parabolic due to balance of gravitational and centrifugal forces, simulating the latitudinal change of the Coriolis parameter (β-effect) in the ocean. The flow characteristics depend on the influx and the rate of rotation and can be classified according to non-dimensional parameters (Rossby, Ekman and Froude numbers denoted byR 0,E andF, respectively). When the influx is small and the rotation rate is large (smallR 0,E andF) the flow will be almost linear, and the fluid flows along the side-wall boundary layer under constraint of the β-effect. For a very large influx (largeR 0 andE) inertial forces become very large compared to the Coriolis force and the flow behaves like a potential flow. The flow studied had characteristics between these two extreme cases and hasR 0 andF similar to the Gulf circulation, though similarity inE is ambiguous. Photographs of the flow indicate that the inflow penetrates further into the interior when the rotation rate is increased while the influx is kept constant. The numerical analysis of the non-linear vorticity equation confirms this for the parameters corresponding to the experiment. In addition, the photographs reveal eddies embedded on both sides of the main stream, particularly near the inflow region. These eddies are intensified and become uniform in size as the influx increases. It is pointed out that such eddies were actually observed near the Loop Current north of the Yucatan Straits.
    Materialart: Digitale Medien
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  • 32
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 35-45 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Dielectric measurements have been carried out on partially hydrated collagen in the frequency ranges 100 kHz-5 MHz, 100 MHz-1 GHz, and 8-23 GHz. In the low-frequency range, a dispersion was observed around 100 kHz which results from inhomogeneous conductivity of the samples. A dielectric relaxation was observed aroud 0.3 GHz using time-domain-spectroscopy techniques. This relaxation can be considered to originate from mobile side chains. Microwave measurements indicate that the water relaxation may extend into the 10-GHz region. An apparent discrepancy between the main water relaxation time and the average rotational correlation time of water as measured by nmr line widths was resolved by the assumption that a fraction of the water molecules is bound to the collagen with residence times on the order of 10-6 sec, whereas the remainder of the water is only weakly bound and exhibits rotational rates on the order of 10-10 sec.
    Zusätzliches Material: 5 Ill.
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  • 33
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 83-100 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A model for the time dependence of DNA conformational state probabilities is formulated in the form of first-order differential equations. This model is applied to investigate the renaturation and denaturation rates for T2 and T7 DNA as reported in the series of experiments by Record and Zimm. Qualitative agreement is found in denaturation and for series of renaturation experiments with the same initial condition. However, partial agreement with series of renaturation experiments having the same final condition is obtained only by including an initial bimolecular step with properly matched pairs of strands. Comparison of all experiments with the calculated rates yields 5 × 104 min-1 as the step rate for melting a single base pair.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 34
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The conventionally protected oligopeptides of the two homologous series Boc-(L-Ile)n-OMe and Boc-(D-aIle)n-OMe (n = 2-6) were synthesized in a standard stepwise fashion and their uv and CD spectra in 2,2,2-trifluoroethanol, and solid-state ir spectra were investigated. In addition, two oligomeric products derived from the NCAs of L-isoleucine and of D-allo-isoleucine and having a DP of 20 and 12, respectively, were studied in the solid state by x-ray and ir. No substantial differences between the properties of the diastereomeric oligomers in the solid state were noticed, a β-structure being very likely at least for the Boc-protected hexapeptides and the higher oligomers. In contrast, differences were observed between the spectroscopic properties of the diastereomeric oligopeptides, and especially of the hexapeptides, in trifluoroethanol solution. The different properties of the hexapeptides in solution were related to the existence, in the case of Boc-(L-Ile)6-OMe, of soluble molecular aggregates in which the peptide chains assume the β-conformation. These results provide an additional example of the influence of the configuration of asymmetric carbon atoms of the side chains on the conformational properties of peptide molecules in solution.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 35
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 285-297 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The 1H-nmr chemical shifts and the spin-spin coupling constants of the common amino acid residues were measured in solutions of the linear tetrapeptides H-Gly-Gly-X-L-Ala-OH in D2O and H2O, the influence of X on the nmr parameters of the neighboring residues Gly 2 and Ala 4 was investigated. The titration parameters for the side chains of Asp, Glu, Lys, Tyr, and His were determined. The pKa values obtained in D2O, with the use of pH-meter readings with a combination glass electrode uncorrected for istope effects, were 0.06 pH units higher in the acidic range and 0.10 pH units higher in the basic range than the corresponding pKa values in H2O. This suggests that the present data are suitable “random-coil” 1H-nmr parameters for conformational studies of polypeptide chains in D2O and H2O solutions.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 36
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 299-311 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This paper shows that backbone amide proton titration shifts in polypeptide chains are a very sensitive manifestation of intramolecular hydrogen bonding between carboxylate groups and backbone amide protons. The population of specific hydrogen-bonded structures in the ensemble of species that constitutes the conformation of a flexible nonglobular linear peptide can be determined from the extent of the titration shifts. As an illustration, an investigation of the molecular conformation of the linear peptide H-Gly-Gly-L-Glu-L-Ala-OH is described. The proposed use of amide proton titration shifts for investigating polypeptide conformation is based on 360-MHz 1H-nmr studies of selected linear oligopeptides in H2O solutions. It was found that only a very limited number of amide protons in a polypeptide chain show sizable intrinsic intration shifts arising from through-bond interactions with ionizable groups. These are the amide proton of the C-terminal amino acid residue, the amide protons of Asp and the residues following Asp, and possibly the amide proton of the residue next to the N-terminus. Since the intrinsic titration shifts are upfield, the downfield titration shifts arising from conformation-dependent through-space interactions, in particular hydrogen bonding between the amide protons and carboxylate groups, can readily be identified.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 37
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 359-372 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We present a method that can reduce conformational energy calculations for an arbitrary peptide consisting of n residues (n-peptide) to the complexity of a computation for (Gly)n. This reduction, and the concomitant savings in computer time, is accomplished by replacing all side chains, as well as the backbone CαHα and CαH2α groups, by “interaction centers.” The backbone CONH group is left intact in order to preserve its directional character. The interaction centers “see” each other, and the atoms of the CONH group via Boltzmann and space-averaged effective center-center and center-atom potentials, respectively. This averaged-interaction method is tested on the repeat tetra-, penta-, and hexapeptides of elastin, Val-Pro-Gly-Gly (VPGG), Val-Pro-Gly-Val-Gly (VPGVP), and Ala-Pro-Gly-Val-Gly-Val (APGVGV), using the stereoalphabet strategy for the energy calculations. The excellent qualitative and quantitative agreement we obtain with both full atom-atom calculations and extensive nmr data, coupled with the order-of-magnitude reduction in computer time, augurs well for the potential usefulness of the method.
    Zusätzliches Material: 5 Ill.
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  • 38
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 393-409 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Linear response theory in the decorrelation or random-phase approximation is used to calculate the absorption and CD spectra of model helical polymers, including single-stranded polyadenylic acid. The method, which makes use of infinite polymer selection rules for the linear response tensor, has the advantages that (1) only a few three-dimensional matrices need be inverted; (2) spectral band shapes of the polymer arise naturally from those of the monomer, as well as from the geometry-dependent interactions in the helix; and (3) the spectral dependence on geometrical factors of the helix is made transparent. It is found that the structure of the polymer CD spectrum depends critically on monomer bandshape. An asymmetric CD spectrum, similar to some experimental spectra, arises from either a Gaussian or a composite monomer band. Single-stranded polyadenylic acid spectra are sensitive to helix geometry in the region 200-240 nm, in reasonable agreement with experimental spectra. This sensitivity arises from the 207-nm monomer transition, and the results suggest that this region of the spectrum should be more fully exploited as a tool for helix geometry studies.
    Zusätzliches Material: 12 Ill.
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  • 39
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: C24H34N2O9, orthorhombic, P212121; a = 39.432 (10), b = 14.061 (5), c = 4.850 (2) Å, M = 494 a.m.u., Z = 4, Dm = 1.22 g cm-3, Dx = 1.22 g cm-3, R = 0.13 for 1205 observed reflections after refinement with isotropic thermal factors. The urethane and amide bonds are in the trans configuration, as well as all the ester groups. The ϕ and ψ angles of the L-glutamyl residues fall in the β-structure region of the Ramachandran's plot; the molecule is rather flat with the amide plane almost parallel to the c axis along which two hydrogen bonds hold the molecules together to form long rows in a “parallel pleated-sheet” fashion.
    Zusätzliches Material: 2 Ill.
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  • 40
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The far-ir absorption spectrum of lysozyme was measured at room and liquid-nitrogen temperatures. Dried layers of single crystals of tetragonal lysozyme chloride with a diameter of 100-300 μm were grown on a silicon plate. Such single-crystalline samples were considered to have the following advantages in obtaining far-ir spectra: (1) surface scattering is reduced, (2) the protein molecules are closely packed, and (3) air-drying of the crystals reduces the number of water molecules without considerably changing the original configuration. The spectrum obtained consisted of a strong background absorption and a number of absorption peaks that were not clearly observed with the sample in the form of lyophilized powder. The peaks were ascribed to various delocalized vibrations of the main and side chains in the molecule. The peaks were also compared with the positions of Raman lines. The uniform background was assigned to the water molecules remaining in the crystals.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 41
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 553-569 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The duplex-to-strand transition of the self-complementary sequence dG-dC-dG-dC has been probed at the exchangeable and nonexchangeable protons and backbone phosphates by high-resolution nmr spectroscopy. The Watson-Crick imino and amino hydrogen-bonded protons, as well as the exposed amino protons, could be followed through the duplex-to-strand transition and provide information on base-pair stability at the tetranucleotide duplex level. The magnitudes of the experimental upfield nonexchangeable base-proton chemical shifts on duplex formation are consistent with calculations based on base-pair overlap geometries of the B-DNA type. The variation of the 31P chemical shifts in dG-dC-dG-dC with temperature appear to monitor changes in the ω,ω′ rotation angles about the O—P bonds in the postmelting transition temperature region. The complex formed between the antitumor anthracycline antibiotic daunomycin and the dG-dC-dG-dC duplex was probed at the nucleic acid and the antibiotic resonances as a function of temperature. The experimental complexation shifts of the observable daunomycin resonances have put constraints on possible overlap geometries between the intercalating anthracycline ring and adjacent base pairs.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 42
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Conformational analyses of cyclic tetrapeptides consisting of alternating cis and trans peptide units have been made using contact criteria and energy calculations. This study has been restricted to those structures having a symmetry element in the backbone ring, such as a twofold axis (d) or a center of inversion (i). There are five main results. (1) There are two distinct types of conformations, which are stereochemically favorable corresponding to each of twofold and inversion-symmetrical structures, designated as d1, d2 (for twofold symmetrical) and i1, i2 (for inversion-symmetrical). Among these, the i1 type has the lowest energy when glycyl residues occur at all four α-carbon atoms. (2) With the glycyl residue at all four α-carbon atoms, methyl substitution at the cis peptide nitrogen atoms is possible in all the four types, whereas the substitution at trans peptide nitrogen atoms is possible only for the i1 type. Thus only in the i1 type can all the nitrogen atoms be methylated simultaneously. The conformation of the molecule in the crystal structure of cyclotetrasarcosyl belongs to the i1 type. (3) When alanyl residues occur at all four α-carbon atoms, the possible symmetrical type is dependent on the enantiomorphic form and the actual sequence of the alanyl residues. (4) The methyl substitution at peptide nitrogen atoms for cyclic tetrapeptides having alanyl residues causes more stereochemical restriction in the allowed conformations than with glycyl residues. (5) The prolyl residue can be incorporated favorably at the cis-trans junction of both d and i types of structures. The results of the present study are compared with the data on cyclic tetrapeptides available from the crystal structure and nmr studies. The results show an overall agreement both regarding the type of symmetry and the conformational parameters.
    Zusätzliches Material: 4 Ill.
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  • 43
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Based on equilibrium binding studies, as well as on kinetic investigations, two types of interactions of Cu2+ ions with native DNA at low ionic strength could be characterized, namely, a nondenaturing and a denaturing complex formation. During a fast nondenaturing complex formation at low relative ligand concentrations and at low temperatures, different binding sites at the DNA bases become occupied by the metal ions. This type of interaction includes chelate formation of Cu2+ ions with atoms N(7) of purine bases and the oxygens of the corresponding phosphate groups, chelation between atoms N(7) and O of C(6) of the guanine bases, as well as the formation of specific intestrand crosslink complexes at adjacent G°C pairs of the sequence dGpC. CD spectra of the resulting nondenatured complex (DNA-Cu2+)nat may be interpreted in terms of a conformational change of DNA from the B-form to a C-like form on ligand binding. A slow cooperative denaturing complex formation occurs at increased copper concentrations and/or at increased temperatures. The uv absorption and CD spectra of the resulting complex, (DNA-Cu2+)denat, indicate DNA denaturation during this type of interaction. Such a conclusion is confirmed by microcalorimetric measurements, which show that the reaction consumes nearly the same amount of heat as acid denaturation of DNA.From these and the kinetic results, the following mechanism for the denaturing action of the ligands is suggested: binding of Cu2+ ions to atoms N(3) of the cytosine bases takes place when the cytosines come to the outside of the double helix as a result of statistical fluctuations. After the completion of the binding process, the bases cannot return to their initial positions, and thus local denaturation at the G·C pairs is brought about. The probability of the necessary fluctuations occurring is increased by chelation of Cu2+ ions between atoms N(7) and O of C(6) of the guanine bases during nondenaturing complex formation, which loosens one of the hydrogen bonds within the G·C pairs, as well as by raising the temperature. The implications of the new binding model, which comprises both the sequence-specific interstand crosslinks and the described mechanism of denaturing complex formation, are discussed and some predictions are made. The model is also used to explain the different renaturation properties of the denatured complexes of Cu2+, Cd2+, and Zn2+ ions with DNA.In temperature-jump experiments with the nondenatured complex (DNA-Cu2+)nat, a specific kinetic effect is observed, namely, the appearance of a lag in the response to the perturbation. The resulting sigmoidal shape of the kinetic curves is considered to be a consequence of the necessity of disrupting a certain number of the crosslinks existing in the nondenatured complex before the local unwinding of the binding regions (a main step of denaturing complex formation) may proceed.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
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  • 44
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 931-938 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new analysis has been made on studies of the influence of imino acid content on the changes of collagen thermal stability (tm). It is shown that, for the interstitial vertebrate collagens, there is a strict regularity in the changes of tm depending on hydroxyproline content. No correlation is observed between tm and proline content. Also, no correlation between tm and hydroxyproline content is observed for invertebrate and basement membrane collagens. On the basis of the reported data, the dependence of tm on hydroxyproline content is considered to be not a correlation between tm and the total content of hydroxyproline, but only as the correlation between tm and the content of hydroxyproline occurring at the third position in the sequence (Gly-R2-R3)n. The results agree with the idea that the influence exerted by proline and hydroxyproline on the stabilization of the triple helix of collagen is different.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 45
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The conformation and conformational transitions of poly(His-Ala-Glu) have been investigated by ir, nmr, and CD measurements. The results obtained - as well as the results of our previous investigations by potentiometric titration and hydrodynamic techniques [Goren et al., Biopolymers (1977) 16, 1541-1555] - indicate that when dissolved in water, the co-polymer assumes a disordered conformation. On changing the pH of the solution, the states of ionization of the side-chain imidazole and carboxyl groups change in the same manner as in low-molecular-weight model compounds. Concomitantly, the overall shape of the macromolecule is altered, while the conformation of the polypeptide backbone changes from one disordered state to another but never assumes a regular form. In water/methanol and water/trifluoroethanol mixtures, transitions from a disordered state to the α-helix conformation were observed on increasing the alcohol content of the system. The conformational transitions followed pathways which differ from one another according to the experimental conditions employed. Conformational landmarks (intermediates) have been identified along these pathways.
    Zusätzliches Material: 8 Ill.
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  • 46
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 1023-1026 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 47
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 1821-1828 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The decrease in the limiting viscosity number [η] with temperature T for hyaluronic acid in nonalkaline solution and chondroitin 4-sulfate in neutral and alkaline solutions may be expressed in terms of the temperature coefficient of the Kratky-Porod persistence length a: d ln a/dT = -0.0040 (±0.0005). The result, while numerically somewhat smaller, resembles qualitatively that of cellulose derivatives. As in the latter case, standard conformational calculations underestimate the coefficient, which may be due to neglect of random occurrence of local conformational features of higher energy. In alkaline solution, large decreases in [η] of hyaluronic acid are accompanied by a positive temperature coefficient of [η]. This temperature effect is interpreted as an endothermal shift from the alkaline, low [η] form of the polymer to the neutral, high [η] form with increasing temperature.
    Zusätzliches Material: 2 Ill.
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  • 48
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 1809-1820 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have considered whether or not the tertiary structure of a biomolecule is the same in a crystal (or an oriented film) as it is in solution. A methodology has been developed for comparing polarized absorption spectra obtained from a solid-state sample with those obtained from an oriented solute to further resolve this question. An electric dichroism instrument built in our laboratory was used to measure the solution dichroism signal which, along with the ordinary solution uv absorption spectra, yields polarized absorption spectra in the directions parallel and perpendicular to the applied electric field. These were then compared to polarized absorption data from oriented films of nucleic acids to determine whether the two sets of data could be rotated into coincidence. This rotation was accomplished using a computer program based on a nonlinear programming method. Four nucleic acids were studied and the film and solution data for three of these were found to be equivalent, requiring rotation through an angle of 3°-20°, depending on film humidity, to bring them into coincidence. For the fourth sample we were unable, perhaps because of signal-to-noise ratio limitations, to find a correlation. Flow dichroism and electric dichroism data were also found to be quite similar. Thus it is clear that the induced dipole moment is along the helical axis and that the physical, hydrodynamical, and electrical axes of the nucleic acid molecules are equivalent.
    Zusätzliches Material: 4 Ill.
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  • 49
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effect of enzyme-inhibitor complex formation on the hydration properties of the macromolecular moiety was investigated on the model system of α-chymotrypsin and its Ser-195 tosyl derivative. The primary (A-shell) hydration of the native and modified enzyme was compared by sorption measurements. The secondary (B-shell) hydration water was investigated by differential scanning calorimetry. Tosylation is known to induce pronounced conformational changes in the chymotrypsin molecule. These structural modifications have the following effects on the hydration of the native enzyme.The water binding capacity of the protein surface is significantly increased, as shown by both the calorimetric and the sorption results. The amount of unfreezable water of primary hydration is increased by 50 mol H2O/mol chymotrypsin.The heats (ΔH) and entropies (ΔS) of the interaction of water with chymotrypsin are strongly reduced in the modified enzyme. This effect is interpretable by a reduction of the H bonding potential of the protein surface. Parallel to this decrease in δH, the heats of fusion of the secondary hydration water (Qfus) are significantly increased by tosylation (Qfus = 256.2 ± 7.8 and 294.2 ± 4.8 J g-1 H2O for the native and the tosylated enzyme, respectively). This increase in Qfus reflects an increase in the extent of H bonding in the B-shell hydration sphere.These changes in the hydration of the native enzyme, associated with the reaction: native chymotrypsin → tosylchymotrypsin, are interpreted by cooperative phase transitions of water molecules in the primary and secondary hydration water. One of these transitions was found to exhibit a significant, linear enthalpy-entropy compensation effect. The compensation temperature \documentclass{article}\pagestyle{empty}\begin{document}$ \hat{\beta} $\end{document} is 290.7 ± 2.8°K. This \documentclass{article}\pagestyle{empty}\begin{document}$ \hat{\beta} $\end{document} value agrees well with compensation temperatures reported in the literature for a series of biochemical reactions in aqueous solution (250-320° K). This agreement in \documentclass{article}\pagestyle{empty}\begin{document}$ \hat{\beta} $\end{document} may point to a common source of both compensation phenomena.
    Zusätzliches Material: 6 Ill.
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  • 50
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 1829-1830 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 51
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 1831-1833 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 52
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 53
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 1835-1848 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The conformations of melanostatin have been studied experimentally using CD spectroscopy and via calculations. In aqueous solution and 2,2,2-trifluoroethanol (TFE) there is no evidence that monomers of the tripeptide exist in an ordered (β-bend) structure. In water and TFE solutions (3-6 × 10-4M) the neutral molecules aggregate very slowly, taking about 3 days to attain equilibrium at room temperature. At equivalent concentrations in TFE, although not in water, the cationic molecules also slowly aggregate, although to a lesser extent. Calculations using rotational isomeric state theory give the most probable unperturbed end-to-end distance of the molecule at 9.3 ± 0.1 Å and indicate that a vast majority of the molecules exist in some extended conformation, end-to-end distance ≥6 Å. Only 0.4% of the molecules are calculated to have O…H separations compatible with a β-bend structure. An intramolecular hydrogen bond must have an energy at least 2 kcal/mol lower than that of an intermolecular hydrogen bond to solvent if a β-bend is to be experimentally observable.
    Zusätzliches Material: 9 Ill.
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  • 54
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2105-2113 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Nps-[Glu(OBzl)]6-NHEt has been prepared by coupling Nps-[Glu(OBzl)]2-OH with HCl,H-[Glu(OBzl)]4-NHEt by means of dicyclohexylcarbodiimide. The ir spectra of its nujol mull show that the hexapeptide has the β-structure of antiparallel chains. When it is dissolved in dioxane or ethylene dichloride, the hexapeptide consists of a mixture of the β-form and the solvated σ-form, but the β-form can exist only above a certain critical concentration. The critical concentration is about 0.4g dl-1 in dioxane and 0.08g dl-1 in ethylene dichloride, and the content of β-form increases with increasing concentration above it. The CD of the dioxane and ethylene dichloride solutions shows concentration dependence in visible and uv regions.
    Zusätzliches Material: 7 Ill.
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  • 55
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2115-2126 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Light scattering from the solutions of Nps-[Glu(OBzl)]6-NHEt in dioxane or ethylene dichloride has been measured at different concentrations, and a critical concentration of intermolecular association is found to exist, which is equal to the critical concentration of β-form formation. The Debye plot of light scattering leads to the molecular weight of aggregates at the critical concentration, which corresponds to an aggregation number 15 in dioxane and 53 in ethylene dichloride. In the latter solvent the aggregates further associate into a larger aggregate consisting of 330 molecules when the concentration is increased beyond the critical concentration. The content of β-form, which is a measure of number of hydrogen bonds, is derived from the ir data previously obtained. The results on the modes of intermolecular association and hydrogen bonding lead to possible structures of aggregates formed by both hydrogen bonds and other nonbonding side-chain interactions.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 56
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Low shear viscosities have been determined for a 1 mg/ml poly(L-lysine) solution as a function of added salt concentration in the region of the previously reported ordinary-extraordinary phase transition. The measured viscosities indicate that the polyions are far from completely extended at the transition. Estimates of the longest internal relaxation time for an equivalent free-draining Rouse-Zimm chain give τ ≃ 10-5 sec, similar to that of the rapid, angle-independent component previously observed in the dynamic light-scattering correlation function at the transition. An unusual peak and valley are observed in the curve of [η]0 versus [NaBr] in the transition region. Possible interpretations of these features, and their bearing on the nature of the extraordinary phase, are discussed.
    Zusätzliches Material: 1 Ill.
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  • 57
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2145-2166 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The crystal structure of the valinomycin analog, cyclo-[(-D-Val-Hyi-Val-D-Hyi-)3-] (meso-valinomycin, C60H102N6O18) has been determined by direct x-ray diffraction procedures. The crystals are triclinic, space group P1, number of molecules per unit cell Z = 1, and cell parameters a = 11.831, b = 13.815, c = 14.889 Å, α = 109.54°, β = 116.10°, γ = 98.89°. The atomic coordinates for the C,N,O atoms were refined in the anisotropic thermal motion approximation and for the H atoms in the isotropic approximation to R = 0.07.The structure is centrosymmetric and has a threefold axis of pseudosymmetry. The depsipeptide chain is in the form of a bracelet stabilized by six identical intramolecular 4 → 1 hydrogen bonds between the amide C=O and NH groups. The ester carbonyls are oriented towards the symmetry axis, their O atoms forming an ellipsoidal molecular cavity. The isopropyl side chains are located on the molecular periphery. The structure found differs considerably from the conformation of the crystalline naturally occurring antibiotic, valinomycin, but completely resembles that of valinomycin and meso-valinomycin in nonpolar solvents. In the crystal, meso-valinomycin molecules form stacks. The molecular cavities situated in the stacks one above the other along the pseudo-C3 axis form a continuous channel, the internal surface of which is lined by O atoms. The possible conformations of depsipeptides of the valinomycin series and their mode of action in membranes are discussed in the light of the data obtained.
    Zusätzliches Material: 11 Ill.
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  • 58
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2353-2356 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Large molecular weight bacteriophage G DNA, about five times larger than T2 DNA, was used to test Zimm's theory [(1974) Biophys. Chem. 1, 279-291] for the effect of rotor speed on the sedimentation of large linear monodisperse DNA. Sedimentation profiles from neutral sucrose gradinets at low and high rotor speeds show G DNA sedimenting from 1.8 to 0.7 times as fast as T2 DNA. Experimental measurements indicate that the sedimentation coefficient of G DNA decreases with increasing rotor speed about as fast as predicted by theory.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 59
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have examined the NH stretching frequencies of N-acetyl-N′-methyl-L-alanineamide (blocked Ala), N-acetyl-N′-methylglycineamide (block Gly), and N-acetyl-N′-methyl-L-leucineamide (blocked Leu) in chloroform using irspectroscopy. Their spectrum of blocked Leu in carbon tetrachloride was also obtained. A major absorption band at 3450 cm-1 is attributed to the unperturbed NH stretching frequency. Another major band at 3437 cm-1 (for Ala) or 3432 cm-1 (for Leu) is attributed to conformations in which the NH stretching frequency is perturbed by the spatial proximity of the Cβ atom. An absorption band between 3300 and 3370 cm-1, which has in the past been assigned to the intramolecular hydrogen-bonded NH in the C7eq conformation, was found to be concentration dependent and could not be observed below 5 × 10-4M in chloroform; thus we find no evidence for a strongly hydrogen-bonded NH in the C7eq conformation in chloroform. An absorption band at 3416 cm-1 was observed in chloroform solutions of blocked Gly, and a similar absorption appeared as a shoulder on the 3437- and 3432-cm-1 bands of blocked Ala and blocked Leu, respectively, in the same solvent. These bands, occurring near 3416 cm-1, may be assigned to extended (C5) conformations [Avignon et al., Biopolymers 8, 69 (1969)]. In CCl4 the spectrum of blocked Leu remained concentration dependent below 2.8 × 10-4M, with the 3300-3370-cm-1 band progressively weakening and shifting to higher frequencies on dilution from higher concentrations. Analysis of the spectra indicates that there is considerable flexibility in the blocked single residues, in agreement with the results of conformational energy calculations.
    Zusätzliches Material: 5 Ill.
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  • 60
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2523-2535 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Type I collagen fibrillogenesis in vitro has been studied by laser light scattering, and the results indicate that initiation of aggregation involves at least two steps. Step I of aggregation involves no change in the intensity of scattered light at an angle of 90° and is accompanied by a decrease in the diffusion coefficient. Step II is characterized by an increased intensity of scattered light and decreased diffusion coefficients. Theoretical calculations using the Stokes-Einstein equation for the translational diffusion coefficient and the Perrin equation for the frictional coefficient of a prolate ellipsoid indicate that the step I aggregates are 4D staggered linear dimers and trimers 570 and 845 nm long, whereas step II aggregates are greater than 950 nm in length. These dimensions are similar to those previously reported based on physicochemical measurements and electron microscopy. It is proposed that the rate and extent of fibrillogenesis in vitro is controlled by the concentration of the linear aggregates and that the effects of temperature and collagen concentration on fibrillogenesis previously observed are qualitatively explained in terms of their effects on the concentration of these aggregates.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 61
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2537-2547 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The method hitherto used for estimating the electrostatic term in empirical intramolecular calculations of stable conformations of biologically important molecules and macromolecules and intermolecular calculations of molecular associations or packing energy in molecular crystals had been analyzed. It has been shown that the contribution of atomic hybridization moments is omitted in the calculation of electrostatic interactions from net atomic charges localized on nuclei which have been determined by standard quantum-chemical methods. This contribution plays an important part in determining electrostatic interactions, mainly in molecules containing atoms with lone pairs. Simultaneously, a modified method for calculating the electrostatic term comprising the interaction of the lone pairs, which are represented by atomic hybridization moments, has been proposed. The relationship between the atomic hybridization moment and the bond angle has been expressed for some typical configurations occurring in biologically important molecules. Finally, this new approach is illustrated by results of the conformational analysis of some model compounds for biomolecules and compared with the approach used so far for the estimation of the electrostatic interaction in empirical methods of calculation of the intra- and intermolecular energy.
    Zusätzliches Material: 3 Ill.
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  • 62
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2549-2567 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Intensity fluctuations of laser light scattered from filamentous viruses Pf1 [length L (Å) × diameter d (Å) = 20,000 × 90], M13 (9000 × 90), potato virus X (5150 × 130), and tobacco mosaic virus (3000 × 180) in sucrose density gradients were measured with a photon correlation spectrometer over a range of scattering angles from 15° to 120°. The experimental data can be approximated by two exponential decays, “slow” and “fast.” The slow decay rate constant ts-1 corresponds to the translational diffusion D of the virus, i.e., ts-1 = K2D, where K is the magnitude of the scattering vector. The amplitude of the slow component, i.e., translational diffusion, remains greater than that of the fast component, even at high KL. The fast decay rate constant tf-1 is also proportional to K2 for viruses such as Pf1, M13, and even potato virus X. In the companion paper, we shall attribute the amplitude enhancement of the translational diffusion to the coupling of its anisotropy to the rotational diffusion modes. In order to explain the excessive decay rates in the fast component, we need to consider the bending mode of rodlike viruses, especially in the longer viruses such as M13 and Pf1, in addition to the usually expected rotational diffusion modes.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 63
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2569-2588 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have compared four theoretical effects of rodlike macromolecules with the fast components, i.e., components other than translational diffusion, of our experimental data, which are presented as amplitude autocorrelation functions of electric field scattered from dilute solutions of monodisperse rodlike viruses with lengths from 3300 Å for tobacco mosaic virus to 20,000 Å for Pf1. The four effects are (1) the optic anisotropy treated by Aragón and Pecora, (2) coupled translational-rotational diffusion due to anisotropy in translational mobility recently reformulated by Gierke, (3) anisotropic rotational diffusion with respect to the direction of translational displacement first discussed by Berne and Pecora, and (4) the bending mode of a rod by Fujime and Maruyama. We show that both the first and second effects are required to explain the enhancement of amplitude of the translational diffusion at the expense of fast components. The experimental decay rates of the fast component exceed that of the rotational diffusions. In order to explain the excessive decay rate in the fast component, we need to include a minute amount (∼1%) of bending mode of rodlike viruses, especially in longer viruses such as M13 and Pf1.
    Zusätzliches Material: 1 Ill.
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  • 64
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2607-2623 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The previous report that poly(L-glutamic acid) exhibits doubled resonances in the helix-coil transition region by either proton or carbon-13 nmr resolves the question of whether or not this behavior is limited to uncharged polypeptides in organic solvents, as had been previously thought. In the present work, we show that the underlying principle causing this anomalous double-peak behavior is due to molecular-weight polydispersity of the sample. The molecular-weight range in which this phenomenon is observed is largely dependent on the values of σ, the nucleation or cooperativity factor. The principles developed are shown to encompass all classes of polypeptides in a very natural way and to explain the key experimental data in the literature.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 65
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2589-2606 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Empirical conformational energy calculations with the use of ECEPP energy functions have been carried out for linear dipeptides H-X-L-Pro-OH, with X = Gly, L-Ala, D-Ala, L-Leu, D-Leu, L-Phe, and D-Phe, in different states of protonation of the end groups. The results of these calculations are compared with the previously reported experimental equilibrium populations for the cis and trans isomers of the X-Pro bond in the different species. For all the protonation states of the seven dipeptides, the calculated nonbonded interactions and the conformational entropy term lead to a preference of the trans forms over the cis isomers by at least 1 kcal/mol. The electrostatic interactions stabilize the cis conformations in all species except the cationic forms of the D,L-peptides, and it could further be shown that only the carbonyl group of X and the two end groups contribute significantly to the total electrostatic energy. One of the principal results of the experimental studies, i.e., the occurrence of 5-15% cis-proline in all the peptides with an uncharged C-terminus, was corroborated by our investigation of the cationic species. A detailed assessment of the electrostatic contribution to the total energy of the different conformations of H-Gly-L-Pro-OH indicates that the standard ECEPP parameters tend to overestimate the electrostatic interactions in aqueous solutions of the X-Pro dipeptides.
    Zusätzliches Material: 6 Ill.
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  • 66
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 67
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2625-2643 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The secondary structure of the lac repressor protein proposed by Chou et al. has been modified to include the recent revisions in sequence. In addition to the Chou and Fasman method, five other methods were used; they include those of (1) Lim, (2) Ptitsyn and Finkelstein, (3) Burgess et al., (4) Bunting et al., and (5) Wu and Kabat. Any two individual methods gave results differing sharply from one another. Three or more methods were in agreement for 91, 39, and 126 residues in helix, in β, and in combined coil plus turn conformations, respectively; there were such agreements for a total of 256 of the 360 residues. Agreements in the amino-terminal third of the molecule were found for 68% of the residues, whereas in the remainder of the molecule only 53% of the residues showed such agreements. Only two helix-breaking and two β-breaking tripeptides were inconsistent with the composite predictions by three or more methods. The large number of disagreements among the results for different methods indicates that only very limited information is provided by each method and that the basis on which they operate is not clear. There is no a priori reason for a composite prediction to be more reliable than any individual prediction, and such a procedure does not permit the determination of an unambiguous secondary structure. Since these methods were applied to lac repressor before any three-dimensional crystallographic structure was known, the methods may ultimately be evaluated should such a structure become available.
    Zusätzliches Material: 1 Ill.
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  • 68
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2645-2657 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The conformational changes and binding behavior of tetranactin on complexation with sodium, potassium, rubidium, cesium, and ammonium ions were investigated by the measurements of proton magnetic resonance, ir, and Raman spectra. It has been clearly shown that alkali cations coordinate to the oxygen atoms of both the carbonyl group and the tetra-hydrofuran ring, but the ammonium ion coordinates only to the oxygen atom of the tetrahydrofuran. Among the alkali cations the potassium ion most strongly coordinates to the tetrahydrofuran oxygen atoms. The complexation with larger cations induces an expansion of the cavity of the macrocyclic ring of tetranactin and smaller cations contract the cavity. The evidence is revealed by the coupling constants of the methylene protons and the frequency separation between the carbonyl stretching vibrations of the ir- and Raman-active modes. The conformations of the cation complexes in the solid are maintained in solution but that of the cation free form is not.
    Zusätzliches Material: 11 Ill.
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  • 69
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Intercalation-site geometries are generated for a tetramer duplex extracted from B-DNA. Glycosidic angles and puckers of the deoxyribose sugar groups bonded to base pairs BP1 and BP4, namely, those at either end of the tetramer duplex, are assumed to be those of B-DNA to insure continuity. All possible geometrical conformations for combinations of C(2′)-endo, C(3′)-endo, C(2′)-exo, and C(3′)-exo sugar puckers are determined for the tetranucleotide backbone. Those with minimum energy are selected as candidates for intercalation sites. Calculations reveal two pairs of physically meaningful families of intercalation sites which occur in two distinct regions, I and II, of helical angles which orient BP2 relative to BP3 and with the helical axis disjointed between these base pairs. For each site I and II within BP2 and BP3, there are two distinct backbone conformations, A and B, connecting BP3 to BP4 or BP1 to BP2 which do not disrupt backbone conformations connecting BP2 to BP3. Hence two pairs, IA and IB, and IIA and IIB, of intercalation sites exist in which the sugar puckers along the backbone of the tetramer alternate from C(2′)-endo to C(3′)-endo on the backbone (5′p3′) connecting BP2 to BP3. The glycosidic angles of the C(3′)-endo sugar χ3γ are, coincidentally, 80° ± 2° for both conformations γ = A and B connecting BP3 to BP4 along the phosphate backbone (5′p3′). Consistent with the theoretical results, the experimental unwinding angles can be grouped into two categories with absolute values of 18° and 26°. The theoretical unwinding angles for sites IA and IB of 16° and for sites IIA and IIB of 20° occur for a displacement of -0.8 Å in the helical axes of BP2 and BP3 and for a 100% G·C composition, with a decrease depending on the amount of A·T base pairs present. Ratios of theoretical unwinding angles of sites I and II, which range from 0.75 to 0.84 for the two principal sites, compare well with the experimental value of 0.71. The theoretical results, in agreement with experimental observation, provide a new interpretation of the nature and conformation of the possible binding sites. Conformations obtained from these studies of intercalation sites in a tetramer duplex are used to rationalize the well-known neighbor-exclusion principle. The possibility of violation of this principle is demonstrated by the existence of two families of physically meaningful conformations. Conformations of unconstrained dimer duplexes are also obtained, one of which corresponds to the experimental crystal structure of ethidium-dinucleoside complexes, but these cannot be joined to the B-DNA structure. Backbone conformations of the tetramer duplex can be constructed until the base-pair separation reaches 8.25 Å, which may limit the molecules that can intercalate.
    Zusätzliches Material: 12 Ill.
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  • 70
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2769-2782 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: As a continuation of previous papers [Biopolymers (1976) 15, 879; (1978) 17, 1508], the low-frequency dielectric relaxation of DNA solutions was studied with a four-electrode cell and the simultaneous two-frequency measurement. Below a critical concentration, the dielectric relaxation time agrees with the rotational relaxation time estimated from the reduced viscosity and is almost independent of DNA concentration Cp, and the dielectric increment is proportional to Cp. The critical concentration is approximately 0.02% of DNA for molecular weight Mr 2 × 106 and 0.2% for Mr 4.5 × 105 in 1 mM NaCl. Dielectric relaxations are compared for samples before and after deproteinization, and the protein contamination is found to have a minor effect on the dipole moment of DNA. The effect of a mixed solvent of water and ethanol on the dielectric relaxation of DNA is well interpreted in terms of changes in viscosity and the dielectric constant of the solvent, assuming that the relaxation arises from rotation of the molecule with a quasi-permanent dipole due to counterion fluctuation.
    Zusätzliches Material: 12 Ill.
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  • 71
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 72
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2911-2911 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 73
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Conformational energies of α- and β-D-glucopyranoses were computed by varying all the ring bond angles and torsional angles using semiempirical potential functions. Solvent accessibility calculations were also performed to obtain a measure of solvent interaction.The results indicate that the 4C1 (D) chair is the most favored conformation, both by potential energy and solvent accessibility criteria. The 4C1 (D) chair conformation is also found to be somewhat flexible, being able to accommodate variations up to 10° in the ring torsional angles without appreciable change in energy. Observed solid-state conformations of these sugars and their derivatives lie in the minimum-energy region, suggesting that the substituents and crystal field forces play a minor role in influencing the pyranose ring conformation. Theory also predicts the variations in the ring torsional angles, i.e., CCCC 〈 CCCO 〈 CCOC, in agreement with the experimental results. The boat and twist-boat conformations are found to be at least 5 kcal mol-1 higher in energy compared to the 4C1 (D) chair, suggesting that these forms are unlikely to be present in a polysaccharide chain. The 1C4 (D) chair has energy intermediate between that of the 4C1 (D) chair and that of the twist-boat conformation. The calculated energy barrier between 4C1 (D) and 1C4 (D) conformations is high - about 11 kcal mol-1.
    Zusätzliches Material: 7 Ill.
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  • 74
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 3043-3065 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Earlier determinations of density gradient proportionality constants β0, density distributions ρ(r), and the effect of pressure on density gradients in the analytical ultracentrifuge have been of limited precision and usefulness in the study of proteins and polypeptides. Reasons for these difficulties are that numerous intermediate relationships were required in the calculations, and the density ranges studied were generally above 1.2 g/ml. Relations are derived in the present paper to directly compute β0(ρ) values and β0′(ρ) values from the original data without any intermediate expansions or approximations. Data are presented for CsCl, CsBr, and Cs2SO4 and compared with literature values. Density distributions are computed for all three salts under a wide variety of experimental conditions of density, column length, and angular velocity. These values of ρ(r) and re are obtained by a numerical iterative technique. Values obtained by this new method are compared with values obtained using closed-form expressions. The effects of pressure on the composition density gradient for the three salts given above are calculated and found to be significant for Cs2SO4 solutions.
    Zusätzliches Material: 5 Ill.
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  • 75
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 3077-3087 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We present evidence for structures of two ordered forms of polyxanthylic acid based on ir spectroscopy, pH titrations, and thermal transitions. Over the pH range ∼6-9.5, the structure is a four-stranded helix with alkali metal ions specifically complexed in the central channel. These internal counterions stabilize the structure by complexing with carbonyl oxygens and by partial screening of electrostatic repulsion caused by ionization of the xanthine residues in this pH range. Below pH 5, the structure is quite different and much more stable. Our data are consistent with a six-stranded helix in which both carbonyl oxygens and both NH protons are hydrogen bonded.
    Zusätzliches Material: 4 Ill.
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  • 76
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An ir-absorption and Raman-scattering study, in the solid state, has been carried out on monodispersed, N- and C-protected homooligopeptides (number of residues, n, from 2 to 7) of L-valine, L-isoleucine, and L-phenylalanine. The amide I, II, III, V, and vNH regions have been examined. Some deuterated (ND) samples have been examined to complete the assignments. L-Phenylalanine dipeptide displays spectral characteristics compatible with the parallel β-structure; L-isoleucine and L-valine dipeptides are probably in a distorted structure. A mixture of parallel and antiparallel extended chains cannot be excluded for the peptides with n = 3. In the amide I region the spectra of peptides with n ≥ 4 show the existence of the β-conformation. The problem of chain orientation within the pleated-sheet structure is discussed on the basis of a recent theoretical treatment of vibrational interactions of the amide I mode.
    Zusätzliches Material: 6 Ill.
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  • 77
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The stepwise synthesis and conformational studies of the N-terminal helical partial sequence of the membrane-modifying polypeptide antibiotic alamethicin are described. The polyoxyethylen esters of the fragments N-t-Boc-L-Pro-Aib-Ala-Gln-Aib-Val-Aib-Gly-OH and N-Ac-Aib-L-Pro-Aib-Ala-Aib-Ala-Gln-Aib-Val-Aib-Gly-OH are synthesized using polyoxyethylene (molecular mass 10,000) as solubilizing support. CD spectra of each intermediate in ethanol show α-helix formation of the N-protected peptide polymers beginning with the nonapeptide and of the N-protonated sequences beginning with the decapeptide. Compared to the helix of alamethicin, temperature- and solvent-dependent CD measurements indicate analogous conformational behavior. The results suggest that in lipophilic media the alamethicin helix can extend the full length of the partial sequence between the two proline residues and that aqueous media favor an increase of random-coil conformation.For model studies of the particular lipid interaction of alamethicin, the stepwise synthesis of peptides with the alternating (Aib-L-Ala)n sequence (n = 1-7) was carried out on a polyoxyethylene support (molecular mass 6000). CD and ORD studies in ethanol showed a change from the random coil to a right-handed α-helix with increasing peptide length. This change is observed for the N-protected peptides at a chain length of 8 residues and for the N-protonated peptides at a length of 9 residues. The comparison of the CD data of free and polyoxyethylene-bound peptides revealed that the solubilizing polymeric support cannot induce conformational changes. The intensities of the CD bands of t-Boc-(Aib-L-Ala)n-OPOE (n ≥ 6) are higher than those of alamethicin, and these model peptides show similar temperature and solvent inducible changes of their helix contents.
    Zusätzliches Material: 8 Ill.
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  • 78
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 79
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 539-552 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The three-dimensional structure of putrescine diphosphate has been solved by x-ray diffraction analysis. The structure reveals the detailed interaction between the amino groups of putrescine and the phosphate residues in which hydrogen bonding and electrostatic forces play a predominant role. The structure serves as a useful model for understanding the interaction of amines with nucleic acids both in a sequence-specific and non-sequence-specific fashion. In particular, a model is proposed for the interaction of the E-amino group of lysine with regions of DNA containing adenine-thymine sequences.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 80
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 609-623 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A general model for the large-scale, time-independent structure of duplex DNA is developed based on elastic considerations. The general conditions of elastic equilibrium are given. These equations are solved for the equilibrium shape of stressed duplex DNA, based on the assumption that the double helix behaves mechanically as a symmetric, linearly elastic rod. It is shown that, in general, two orders of superhelicity will arise at equilibrium. Several possible applications of this approach to the supercoiling of closed circular DNA are described.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 81
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 663-680 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Temperature-dependent conformational transitions of deoxyoligonucleotides have been monitored by measuring 31P chemical shifts, spin-lattice relaxation times (T1), and 31P-{H} nuclear Overhauser enhancements (NOEs). The measured NOE ranged from 30 to 80%, compared to the theoretical maximum of 124% for a dipolar relaxation mediated by rapid isotropic rotation. The observed 3′-5′ phosphate diester 31P T1 showed a similar temperature dependence over the range 2-75°C for both double- and single-stranded oligonucleotides, and for dinucleotides. The results show that dipole-dipole interactions dominate the internucleotide phosphate relaxation rate in oligonucleotides. The same is true of terminal phosphate groups at low temperature; but at higher temperature another process, possibly due to contamination by paramagnetic ions, becomes dominant. The rotational correlation time τR calculated from the dipole-dipole relaxation rate of the internucleotide phosphate in d(pA)2 at 16°C is τR = 5.0 × 10-10 sec, implying a Stokes radius for isotropic rotation of 7.6 Å. The T1 and NOE values for the double-helical octanucleotide d(pA)3pGpC(pT)3 are consistent with dominance of dipole-dipole relaxation and isotropic rotation of a sphere of radius 14 Å, a reasonable dimension for the double helix. Activation energies for the rotation of dinucleotides range from 4 to 6 kcal/mol, close to the value of 4 kcal/mol expected for isotropic rotation. In order to test the possible effect of internal motion of correlation time τG on the results, we considered a model in which the nucleotide chain rotates about the P-O bonds. Comparison of the calculation with our experimental results shows that internal motion with τG ≅ 10-9 sec, as found from other studies to be present for large nucleic acids, would not influence out T1 and NOE values enough to be distinguished from isotropic rotation. However, we can conclude that τG cannot be as fast as 10-10 sec, even for dinucleotides.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 82
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 739-742 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 83
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 757-763 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Measurements have been made of the high-resolution nmr spectra of the polyamino acids poly[N5-(2-hydroxyethyl)-L-glutamine] and poly[N5-(4-hydroxybutyl)-L-glutamine] in mixed deuterium oxide and water solvent at varying pressures from 1.03 to 3163.7 kg/cm2. The results are compared with previously reported results for the polymer poly[N5-(3-hydroxypropyl)-L-glutamine] under similar conditions. The significance of the behaviour of the polymers is considered in terms of the effect of the presence of hydrophobic residues in their side chains.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 84
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 765-788 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Exact solutions are obtained for the time dependence of the extent of irreversible binding of ligands that cover more than one lattice site to a homogeneous one-dimensional lattice. The binding may be cooperative or noncooperative and the lattice either finite or infinite. Although the form of the solution is most convenient when the ligand concentration is buffered, exact numerical or approximate analytical solutions, including upper and lower bounds, can be derived for the case of variable ligand concentration as well. The physical reason behind the relative simplicity of the kinetics of irreversible as opposed to reversible binding in such systems is discussed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 85
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 887-898 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The preparation of lamellar single crystals of mannan[poly((1 → 4)-β-D-mannose)] is described. Electron diffractograms clearly identify the perpendicular orientation of the chain axis with respect to the lamellar surface. Since the degree of polymerization is 40 or less, no conclusion is made as to chain folding. The unit cell corresponds to the mannan I structure derived from x-ray fiber data on oriented algal mannan. The baseplane dimensions found were a = 7.22 Å and b = 8.92 Å, and the systematic absences observed confirm the proposed P212121 group. It was found that cellulose microfibrils from Valonia ventricosa and bacterial cellulose could serve as extended chain nuclei for inducing oriented crystallization of mannan on cellulose. This produces a shish-kebab type of morphology.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 86
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 939-957 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A general approach to the problem of molecular conformation is advanced. We describe a formalism that permits experimental and theoretical information to be incorporated into a set of upper and lower bounds on intramolecular distances. Structures (conformations) meeting these bounds can be readily generated and compared with each other. To illustrate the use of the method, we have employed a simple “firehose” model for protein folding to predict the long-range hydrophobic interactions in a small protein: pancreatic trypsin inhibitor. Models of this type lead to the proper hairpin turns and a reasonable set of long-range contacts for this protein. Application of the distance geometry method then yields backbone conformations with errors of 4-8 Å compared to the native structure. We discuss both the merits and shortcomings of the firehose model and the relation between distance geometry and energy minimization techniques.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 87
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 1009-1019 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: CD spectra of calf thymus, C. perfringens, E. coli, and M. luteus DNA have been measured in the vacuum-uv region to about 168 nm for the A-, B-, and C-forms. The positive band at about 187 nm and the negative band at about 170 nm found for each type and form of DNA are sensitive to the source of the DNA and the base-base interactions of the double-stranded helix. The A-form spectra confirm that these bands are indeed sensitive to secondary structure. In the near-uv, the CD of B-form DNA is well analyzed as a linear combination of 27% A-form and 78% C-form. However, an analysis of the extended spectrum demonstrates that the near-uv analysis is not correct. The extended analysis shows that the base-base interactions are similar for B- and C-forms in solution, which implies that these two forms have nearly the same number of base pairs per turn. Various types of CD difference spectra are also discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 88
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The 1H-nmr spectra of co-oligopeptides of tryptophan and glycine with structure H-Gly-Trp-(Gly)n-Trp-Gly-OH (n = 0-2) and those of several di- and tripeptides have been recorded at 360 MHz with CD3OD solutions containing 0.1N NaOD. The assignment of resonance signals was generally possible by comparing the spectra of structurally related peptides with each other. In order to solve the remaining ambiguities in the assignment, H-(αL,βS)(α,β-d2)Trp-OH, H-Trp-(αL,βS)(α,β-d2)Trp-OH, and H-Trp-(δ1,ε2,ζ2,ζ3,η2-d5)Trp-OH have been prepared and their spectra compared with those of the undeuterated compounds. The distribution of rotamers around the χ1 and (in two cases) χ2 torsion angles of the side chains has been obtained from the vicinal coupling constants 3JHαHβ and from the long-range coupling constants 4JHβHδ1. These data and an analysis of the chemical shifts of the Gly-Cα protons suggest that the orientation of the aromatic side chain is influenced by the following order of decreasing interaction with the functional groups at N- and C-side: -NH2 〉 -NHCO- 〉 -CONH-〉 -COO-. This rule does not hold for the second Trp residue of di- and tripeptides containing the -Trp-Trp- sequence, which has tentatively been attributed to steric effects.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 89
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 1709-1725 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The number of constraint turns is defined as the number of bound unwinding ligands converted in turns necessary to relax the energy stored in a supercoiled DNA. It is equal to the sum of the twist and of the writhing and is interpreted geometrically. The twist is shown to be related to the derivative of the energy of superhelix formation with respect to the constraint turns. This leads to a semiempirical evaluation of the variation of the conformational energy with the writhing and of the writhing number. The bending contribution to the conformational energy is estimated independently using first-order elasticity. The variation of the twist and of the writhing with the constraint is, in this model, catastrophic. In particular, the writhing number jumps between intervals of allowed values.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 90
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Measurements of translational diffusion coefficients by quasielastic laser light scattering, sedimentation coefficients, and intrinsic viscosities at zero shear of proteoglycan subunit fraction A1-D1-D1 isolated from bovine nasal septa are reported. Molecular weights and hydrodynamic dimensions are compared with those expected on the basis of structural models previously proposed. Comparison of the concentration dependence of the diffusion coefficient in the presence of NaCl and GdnHCl leads to the conclusion that significant self-association behaviour of subunit occurs in the absence of GdnHCl. In the absence of added salt, anomalous nonlinear concentration dependence of Dt estimated from wide-angle light-scattering experiments is observed. In addition, Dt apparently becomes angle dependent. These results are interpreted in terms of the perturbation of normal translational diffusion of the monomer by strong repulsive intermolecular interactions due to the combined effects of long-range electrostatic forces and macromolecular congestion at higher concentrations. By carrying out experiments at small scattering angles, it is possible to determine Dt0 for proteoglycan subunit in the absence of supporting electrolyte. Titration of a dilute solution of subunit with hyaluronic acid results in a sigmoidal behaviour of the Stokes radius, indicating the formation of complexes of higher molecular weight results from the noncovalent association of proteoglycan subunits with hyaluronate. Observation of Dt appears to provide a useful method for studying the proteoglycan subunit-hyaluronate interactions.
    Zusätzliches Material: 14 Ill.
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  • 91
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Evidence is presented which shows that hemoglobin S in sickle cells has a tendency to aggregate even in the oxygenated state. The basis for that conclusion is derived from 13C-nmr rotating-frame spin-lattice relaxation studies in the presence of an off-resonance radiofrequency field in which the carbonyl resonances of hemoglobins in erythrocytes are examined. The experiments indicate that the rotational correlation time of hemoglobin S in oxygenated sickle cells at 38°C is 130 nsec compared to a value of 95 nsec for hemoglobin A in normal erythrocytes at the same temperature and the same mean cell hemoglobin content.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 92
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Fluorescence, CD, absorption, and 1H-nmr studies are reported for complexes of 7-amino-actinomycin D with deoxydinucleotides, deoxytetranucleotides, and poly(dG-dC)· poly(dG-dC). The optical spectra for the 7-amino-actinomycin D complex with pdG-dC, pdG-dC-dG-dC and pdC-dG-dC-dG are similar in shape to the 7-amino-actinomycin D complex with either DNA or poly(dG-dC). The changes in the 1H chemical shifts of the 7-amino-actinomycin D and the pdG-dC resonances that accompany complex formation show that 7-amino-actinomycin D forms a minature intercalated complex with two pdG-dC molecules. The magnitudes of the induced chemical shifts for the 7-amino-actinomycin D complex formation with pdG-dC are similar to, but slightly different from, the induced chemical shifts which are obtained when actinomycin D forms a minature intercalated complex with two pdG-dC molecules. The pdN-dG dinucleotides (N = C, A, or T) form stacked complexes with 7-amino-actinomycin D. The presence of the 7-amino-group results in a larger dimerization constant (in aqueous solution) for 7-amino-actinomycin D [KD(6°C) = 4.4 × 103M-1], as compared to actinomycin D [KD(6°C) = 1.7 × 103M-1]; the chemical shifts which accompany dimer formation indicate that the chromophores stack in an inverted manner. Intercalation of 7-amino-actinomycin D into minature double helices, as well as into calf thymus DNA, poly(dG-dC)·poly(dG-dC), and poly(dA-dC)·poly(dG-dT), results in an enhancement of the relative fluorescence intensity and a shift in both the absorbance and corrected emission spectra.
    Zusätzliches Material: 5 Ill.
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  • 93
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Theoretical calculations of the heteronuclear vicinal coupling constant 3J(13C′NCαH) in peptides have been carried out using the Dirac vector model. The results showed an angular dependence for this coupling constant, which can be expressed in the form 3J(13C′NCαH) = A cos2 θ + B cos θ + C, where A, B, and C are constants and θ is related to the torsional angle φ of the peptide backbone. The results of the present calculations are in very good agreement with those obtained using finite perturbation theory at the INDO level of approximation.
    Zusätzliches Material: 2 Ill.
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  • 94
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effect of charged side chains on the ionization and fluorescence of the Tyr4 phenolic group in angiotensin (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe) was investigated. Several synthetic peptides related to angiotensin were titrated spectrophotometrically and quantum yields of tyrosine fluorescence were also determined. The electrostatic interactions were interpreted according to the Kirkwood-Tanford theory, and the results were related to a recently proposed model [J. L. De Coen and E. Ralston (1977) Biopolymers 16, 1929] for angiotensin conformation in solution. The titration and fluorescence results are in good agreement with the folded conformations of this model, with the exception that the data indicate a weaker interaction between the histidine side chain and the C-terminal carboxyl groups than that proposed in the model.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 95
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Transient electric birefringence of poly(L-α,γ-diaminobutyric acid hydrochloride) in methanol/water mixtures has been measured over a wide range of field strengths and solvent compositions and at different polymer concentrations and temperatures. The molar ellipticity at 222 nm and the specific Kerr constant underwent an abrupt change between 75 and 80 vol % methanol at 25°C, accompanied by a solvent-induced helix-coil transition. Anomalous birefringence transients were observed between 78 and 80 vol% methanol above threshold field strengths. The double logarithmic plots of the steady-state specific birefringence versus the square of field strength for different solvent compositions and polymer concentrations could be superimposed by shifting them horizontally along the abscissa and vertically along the ordinate except for the range where anomalous transients were observed. The threshold field strength could be estimated from the point at which a downward deviation occurred. It increased with increasing polymer concentration and with increasing methanol content on the verge of the transition region. The results were interpreted as indicating that a conformational change from the charged helix to the charged coil is induced by high fields in this system, as in the case of poly(L-lysine hydrobromide) in methanol/water mixtures.
    Zusätzliches Material: 7 Ill.
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  • 96
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2037-2050 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Many ligands, including basic polypeptides, histones, and other proteins bind nonspecifically to DNA in such a way as to render unavailable for further binding several contiguous sites (generally bases or base pairs). An accurate description of the kinetics of such large ligand binding requires a more complex theoretical analysis than does the study of the binding of small ligands to DNA. An exact analytical solution of the problem does not appear feasible. Instead, a Monte Carlo approach is developed which provides an essentially exact numerical solution by simulating the binding experiment using a model one-dimensional lattice to represent the DNA molecule. For the limiting cases of totally irreversible binding and of instantaneous redistribution of bound ligands along the lattice, relatively simple equations can be written and solved for the binding kinetics. These solutions and their realms of applicability are discussed in some detail.
    Zusätzliches Material: 3 Ill.
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  • 97
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The DNA helix-coil transition has been studied in the presence of high concentrations of manganese ions (about 10-3M), which corresponds to the conditions close to equal stability of the A+T and G+C pairs, at the ionic strengths of 10-1, 10-2, and 1.6 × 10-3M Na+. With the Mn2+ ion effect, the transition range is significantly reduced to not more than 0.2°C at 1.2 × 10-3M Mn2+ and 1.6 × 10-3M Na+. The melting curves display a sharp kink at the end of the helix-coil transition, which is interpreted as an indication of the second-order phase transition. It is shown that the melting curves obtained can be approximated by a simple analytical expression 1 - θ = exp[-a(tc - t)], where θ is the DNA helix fraction, tc is the phase transition temperature, and a is an empirical parameter characterizing the breadth of the melting range and responsible for the magnitude of a jump of the helicity derivative with respect to the temperature at the phase transition point.
    Zusätzliches Material: 3 Ill.
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  • 98
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2267-2277 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Pinacyanol in the presence of an excess of poly(L-glutamic acid) [polymer/dye ratio (P/D) 〉 10] exhibits different absorption spectra in the visible region when bound to the slightly charged polypeptide in the α-helical conformation or to the nearly completely dissociated polypeptide in the coillike conformation. These spectra reveal aggregation of the dye bound to the macromolecular chain in both conformations, although in the coillike one different kinds of aggregates may be present. Dye binding is accompanied by the appearance of CD bands in the visible region which are also different for the α-helical and the coillike conformations. The aggregates formed in the presence of the latter change slowly in time and seem to induce some conformational changes in the polypeptide chain. Furthermore, they have been found to be, at least partially, stable with respect to a subsequent reversal to the α-helical conformation. All results could be qualitatively interpreted assuming that in the coillike conformation, ordered regions exist along the chain as proposed by Krimm and Tiffany.
    Zusätzliches Material: 5 Ill.
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  • 99
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2289-2301 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The CD of GDH-NADH complexes was measured in order to reexamine the binding of coenzyme to GDH. The existence of two distinct Cotton effects associated with two separate NADH binding sites/subunit was confirmed with native, polymerizing and crosslinked, unpolymerizing enzyme. CD titration of the high-affinity NADH sites revealed significant dependence of the optical activity of the bound coenzyme on the state of protein association. Molar ellipticity of bound NADH decreased with the increasing degree of polymerization of GDH. It is suggested that the high-affinity NADH sites are loacted at or near the association interface. Binding of NADH to the low-affinity sites, in the presence of GTP, leads to an inversion of the CD spectrum of GDH-NADH complexes. This inversion is not related to the polymerization of GDH. However, for proper analysis of the CD of NADH bound to the low-affinity sites, a correction for the effect of polymerization on the optical activity of NADH bound to the high-affinity sites is required.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2315-2322 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We present a theoretical model which describes a cooperative helix-coil liquid-crystal phase transition. We show that this model predicts a first-order phase transition where certain types of chainlike macromolecules in solution make a transition from a nearly coiled to a nearly rigid conformation accompanied by a simultaneous development of long-range nematic-type liquid crystalline orientational order. From this model, the phase boundaries between nematic and isotropic phases are obtained as functions of concentration of macromolecules and of other physical parameters.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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