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  • Polymer and Materials Science  (25,897)
  • SPACE SCIENCES  (6,789)
  • AERODYNAMICS  (3,347)
  • Adaptation
  • 2005-2009  (3)
  • 1980-1984  (17,230)
  • 1970-1974  (18,829)
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  • 1
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    Advances in Applied Self-organizing Systems (2008)
    London : Springer
    Details
    Keywords: Adaptation ; Artificial Life ; Bio-inspired Computing ; Bio-inspired Robotics ; Collective Behaviour ; Complex Systems ; Decentralized Management ; Distrbuted Management ; Distributed Computing ; Emergence ; Evolutinary Algorithms ; Immune Networks ; Information Transfer ; Multi-agent Systems ; Pattern Formation ; Self-assembly ; Self-organization ; Self-organizing Computation
    Description / Table of Contents: The main challenge faced by designers of self-organizing systems is how to validate and control non-deterministic dynamics. Over-engineering the system may completely suppress self-organization with an outside influence, eliminating emergent patterns and decreasing robustness, adaptability and scalability. Whilst leaving too much non-determinism in the system’s behaviour may make its verification and validation almost impossible. This book presents the state-of-the-practice in successfully engineered self-organizing systems, and examines ways to balance design and self organization in the context of applications. As demonstrated throughout, finding this balance helps to deal with diverse practical challenges. The book begins with the more established fields of traffic management and structural health monitoring, building up towards robotic teams, solving challenging tasks deployed in tough environments. The second half of the book follows with a deeper look into the micro-level, and considers local interactions between agents. These interactions lead towards self-modifying digital circuitry and self-managing grids, self-organizing data visualization and intrusion detection in computer networks, immunocomputing and nature-inspired computation, and eventually to artificial life. The case studies described illustrate the richness of the topic and provide guidance to its intricate areas. Many algorithms proposed and discussed in this volume are biologically inspired and readers will also gain an insight into cellular automata, genetic algorithms, artificial immune systems, snake-like locomotion, ant foraging, birds flocking and mutualistic biological ecosystems, amongst others. Demonstrating the practical relevance and applicability of self-organization, this book will be of interest to advanced students and researchers in a wide range of fields.
    Pages: Online-Ressource (XI, 375 Seiten)
    ISBN: 9781846289828
    URL: http://www.springerlink.com/content/978-1-84628-981-1/
    Language: English
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    E-BOOK
  • 2
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    Thermal adaptation of soil microbial respiration to elevated temperature (2009)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Blackwell for personal use, not for redistribution. The definitive version was published in Ecology Letters 11 (2008): 1316-1327, doi:10.1111/j.1461-0248.2008.01251.x.
    Description: In the short-term heterotrophic soil respiration is strongly and positively related to temperature. In the long-term its response to temperature is uncertain. One reason for this is because in field experiments increases in respiration due to warming are relatively short-lived. The explanations proposed for this ephemeral response include depletion of fast-cycling, soil carbon pools and thermal adaptation of microbial respiration. Using a 〉15 year soil warming experiment in a mid-latitude forest, we show that the apparent ‘acclimation’ of soil respiration at the ecosystem scale results from combined effects of reductions in soil carbon pools and microbial biomass, and thermal adaptation of microbial respiration. Mass specific respiration rates were lower when seasonal temperatures were higher, suggesting that rate reductions under experimental warming likely occurred through temperature-induced changes in the microbial community. Our results imply that stimulatory effects of global temperature rise on soil respiration rates may be lower than currently predicted.
    Description: This research was supported by the Office of Science (BER), U.S. Department of Energy and the Andrew W. Mellon Foundation.
    Keywords: Acclimation ; Adaptation ; Soil respiration ; Thermal biology ; Temperature ; Carbon cycling ; Climate change ; Climate warming ; Microbial community ; CO2
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 3
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    Design and function of superfast muscles : new insights into the physiology of skeletal muscle (2005)
    Annual Reviews
    Details
    Publication Date: 2022-05-25
    Description: First published online as a Review in Advance on October 24, 2005. (Some corrections may occur before final publication online and in print)
    Description: Author Posting. © Annual Reviews, 2005. This article is posted here by permission of Annual Reviews for personal use, not for redistribution. The definitive version was published in Annual Review of Physiology 68 (2006): 22.1-22.29, doi:10.1146/annurev.physiol.68.040104.105418.
    Description: Superfast muscles of vertebrates power sound production. The fastest, the swimbladder muscle of toadfish, generates mechanical power at frequencies in excess of 200 Hz. To operate at these frequencies, the speed of relaxation has had to increase approximately 50-fold. This increase is accomplished by modifications of three kinetic traits: (a) a fast calcium transient due to extremely high concentration of sarcoplasmic reticulum (SR)-Ca2+ pumps and parvalbumin, (b) fast off-rate of Ca2+ from troponin C due to an alteration in troponin, and (c) fast cross-bridge detachment rate constant (g, 50 times faster than that in rabbit fast-twitch muscle) due to an alteration in myosin. Although these three modifications permit swimbladder muscle to generate mechanical work at high frequencies (where locomotor muscles cannot), it comes with a cost: The high g causes a large reduction in attached force-generating cross-bridges, making the swimbladder incapable of powering low-frequency locomotory movements. Hence the locomotory and sound-producing muscles have mutually exclusive designs.
    Description: This work was made possible by support from NIH grants AR38404 and AR46125 as well as the University of Pennsylvania Research Foundation.
    Keywords: Parvalbumin ; Ca2+ release ; Ca2+ uptake ; Cross-bridges ; Adaptation ; Sound production ; Whitman Center
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
    Electronic Resource
    Electronic Resource
    Can strains give adequate information for adaptive bone remodeling? (1984)
    Springer
    Calcified tissue international 36 (1984), S. S118 
    Details
    ISSN: 1432-0827
    Keywords: Bone ; Strain ; Remodeling ; Adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary For bone to remodel adaptively, the cells responsible should follow some algorithm. Nine different loading situations and structures are discussed. It seems that either algorithm must be extremely complex, or cells in different structures must follow different algorithms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406144
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  • 5
    Electronic Resource
    Electronic Resource
    The correlation of the receptor potential with the light induced transient increase in intracellular calcium-concentration measured by absorption change of arsenazo III injected into Limulus ventral nerve photoreceptor cell (1980)
    Springer
    European biophysics journal 6 (1980), S. 191-208 
    Details
    ISSN: 1432-1017
    Keywords: Receptor potential ; Intracellular and extracellular calcium concentration ; Intensity dependence ; Adaptation ; Sensitivity control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The light-induced membrane voltage response (receptor potential, ReP) and the absorption change of the intracellularly injected calcium indicator arsenazo III (arsenazo response) were recorded simultaneously in Limulus ventral nerve photoreceptor cells. A double pulse technique was applied for stimulation. After pressure injection of the indicator into the cell absorption changes were measured at 646 nm to obtain a measure of the changes of the intracellular calcium ion concentration. 1. The size of the arsenazo response increases with increasing intensity of the light stimulus. The intensity dependence of the size of the arsenazo response δAmax shows almost no correlate with the peak amplitude of the ReP, but correlates rather well with the time integral of the ReP. 2. Decreasing light adaptation (caused by prolongation of the repetition time of the pulse pairs) leads to an increase in size of the arsenazo response. Also here δAmax correlates better with the time integral of the ReP than with its peak amplitude. 3. Lowering the calcium concentration in the superfusate (from 10 mmol/l to ca. 40 Μmol/l) causes after ca. 10 min a drastical diminution of the arsenazo response to values below the noise level, and a less marked reduction in size of the ReP. The falling phase of the ReP is slower. After return to normal calcium concentration the arsenazo response recovers partly in ca. 50 min, while the ReP recovers faster. The results show two opposite correlations between ReP and arsenazo response: Increase in size and duration of the ReP causes a greater transient increase of the intracellular calcium ion concentration. This in turn tends to reduce and shorten the ReP. Which effect dominates obviously depends on the conditions of the experiment: when the calcium concentration in the superfusate is reduced to ca. 40 Μmol/l a slow decrease of the ReP is accompanied by a small increase of the intracellular calcium ion concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00537293
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  • 6
    Electronic Resource
    Electronic Resource
    Adaptation properties of the ERG in the grasshopper, Romalea microptera (1981)
    Springer
    European biophysics journal 7 (1981), S. 205-208 
    Details
    ISSN: 1432-1017
    Keywords: Grasshopper ; Electroretinogram ; Adaptation ; Spectral sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The grasshopper ERG displays a rapid recovery of responsivity following the onset of a background light. Although observed earlier in skate and frog, this phenomenon has not previously been seen in an invertebrate. Furthermore, a period of hyperresponsivity exists in early dark adaptation and resembles that found in skate and frog. Thus, recovery in the light and hyperresponsivity in the dark seem to be corollaries of each other. Finally, spectral sensitivity of the ERG is determined and two peaks are found: one at 510 nm and the other at 360 nm. The former appears to be a rhodopsin-mediated sensitivity but the latter does not and they are not clearly separated by chromatic adaptation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00539180
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  • 7
    Electronic Resource
    Electronic Resource
    The contribution of pigment transitions to sensitivity changes in the barnacle photoreceptor and the correlation with the prolonged depolarizing afterpotential (1982)
    Springer
    European biophysics journal 8 (1982), S. 161-172 
    Details
    ISSN: 1432-1017
    Keywords: Photoreceptor ; Visual pigment ; Adaptation ; Facilitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract A conditioning light can cause a decrease (adaptation) or an increase (facilitation) in the sensitivity of barnacle photoreceptors, as measured by the amplitude of the late receptor potential (LRP). We show that a net transfer of visual pigment from the rhodopsin (R) to the metarhodopsin (M) state induces a large facilitation whereas the reverse transfer results in a much smaller facilitation or even an adaptation. These effects were not due to the response to the conditioning light but to the pigment reactions. When the conditioning light did not alter the pigment population (i.e., M → M, R → R) it was followed by an intermediate degree of facilitation. These conclusions are correct for cells which have relatively low sensitivity. In sensitive cells, all pigment transitions produce adaptation. LRP facilitation and the prolonged depolarizing afterpotential (PDA) show several common characteristics with respect to pigment transitions: 1.Their magnitude increases with the amount of pigment transferred from R to M. 2. Both are depressed by the M → R transition. 3. Their production is impeded by the M → R transition. 4. The PDA itself is facilitated by the R → M transition and this facilitation decays with a time course comparable to that of LRP facilitation. These results suggest that there may be an underlying process common to LRP facilitation and PDA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00535457
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  • 8
    Electronic Resource
    Electronic Resource
    Sensitivity changes of photoreceptor cells of Hirudo medicinalis caused by changes in extracellular calcium concentration (1982)
    Springer
    European biophysics journal 8 (1982), S. 173-187 
    Details
    ISSN: 1432-1017
    Keywords: Leech photoreceptors ; Extracellular calcium ; Excitation ; Adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Extracellular recordings from the vacoule of photoreceptor cells of Hirudo medicinalis L. were performed using microelectrodes. The cells were adapted by white light flashes given at constant intervals (20 s). Response height versus relative intensity curves obtained from the same cell in physiological saline (PS) and in bathing solutions of either a) lowered calcium contents (2 ΜM/1 or less) or b) raised calcium contents (15 mM/1) were compared. The cells' adaptation state in PS was operationally defined by the ratio Q=h A /h S where h A is the response height evoked by the adapting flashes, and h S is the corresponding saturation response height. Sensitivity changes were measured by the half saturation intensity shift. Lowering extracellular calcium resulted in: 1. The response height increased and the shape of the response became more rounded and prolonged. 2. The total resistance between the vacuole and outside decreased from 8.2±1.4 MΩ (n=6) in PS to 4.6±0.4 MΩ (n=5). The resistance was independent of the cells' adaptation state. 3. A change of the cells' sensitivity occured either in direction to light adaptation or in direction to dark adaptation. It depended functionally on the ratio Q: a) if Q was less or equal to about 0.6 the cells' sensitivity increased. b) if Q was greater than 0.6 the cells' sensitivity diminished. Raising extracellular calcium decreased the sensitivity of all cells tested independent of their adaptation states in PS. The results can be interpreted under the assumptions that 1. the sensitivity of leech photoreceptor cells is inversely proportional to the intracellular free calcium concentration and Z. intracellular calcium can interact with extracellular calcium in relatively dark adapted cells whereas in relatively light adapted cells the raise of intracellular free calcium is mainly effected by a release from intracellular stores. It is assumed that a Q value of about 0.6 separates relatively light adapted cells from relatively dark adapted cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00535458
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  • 9
    Electronic Resource
    Electronic Resource
    Thermoadaptation of enzymes in thermophilic and mesophilic cultures of Bacillus stearothermophilus and Bacillus caldotenax (1974)
    Springer
    Archives of microbiology 98 (1974), S. 275-287 
    Details
    ISSN: 1432-072X
    Keywords: Thermophilic bacteria ; B. stearothermophilus ; B. caldotenax ; Thermophilic (Thermostable) Enzymes ; Adaptation ; Thermoadaptation of Enzymes ; Thermoadaptation of Bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. Bacillus stearothermophilus was adapted to 37° C (mesophilic culture) and to 55° C (thermophilic culture) by cultivation via an intermediate temperature of 46° C. In the crude extract of the thermophilic bacterial cells the glucokinase, glucose-6-phosphate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase and isocitrate dehydrogenase are more thermostable than the corresponding enzymes in the crude extract of mesophilic cells. At the intermediate temperature of 46° C both types are probably formed. 2. 37° C-precultures of Bacillus caldotenax were further cultivated (in different samples) at 5° C intervals between 30° C and 70° C. It was shown that in 70° C-cells of the above mentioned enzymes more thermostable forms and in 37° C-cells more thermolabile forms are present. Furthermore, as demonstrated in the case of glucose-6-phosphate isomerase and isocitrate dehydrogenase, cells cultured in the temperature range between 30–50° C produced thermolabile enzyme variants (M-type), while cultures between 60–70° C produced thermostable variants (Th-type). At cultivation temperatures above 50° C a pronounced lag-period expressing the metabolic changes was found. In the lag-period, mesophilic enzymes are no longer present as early as 20 min after increasing the temperature (70° C), and synthesis of thermostable enzymes starts about 1 h before the beginning of growth. 3. Similar results were obtained with Bacillus caldotenax precultivated at 70° C and cultivated between 30° C and 70° C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425289
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  • 10
    Electronic Resource
    Electronic Resource
    Growth of bacteria at 100°C and beyond (1981)
    Springer
    Archives of microbiology 129 (1981), S. 127-128 
    Details
    ISSN: 1432-072X
    Keywords: Continuous culture ; Adaptation ; Simulation of hot springs ; Boiling point ; Caldoactive bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bacillus caldolyticus, a caldoactive bacterium originating from a hot spring at Yellowstone Park, was grown in a defined medium, whose composition resembled that of the pool water. Using a chemostat culture, which simulated the natural conditions, the organism could be adapted to grow at 100°C at a reasonable rate. Under increased pressure growth occurred also at 105° C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00455347
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  • 11
    Electronic Resource
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    Properties of enzymes from bacteria grown in the 70–100°C range (1981)
    Springer
    Archives of microbiology 130 (1981), S. 159-164 
    Details
    ISSN: 1432-072X
    Keywords: Adaptation ; Boiling point ; Caldoactive enzymes ; Stabilization ; Thermostability ; Thermal characteristics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In chemostat cultures of Bacillus caldolyticus, adaptation in a single step from 70–100°C was followed under aerobic and oxygen-limited conditions and was found to proceed more smoothly under the latter circumstances. Variations of the medium (e.g. yeast extract or silicate concentrations) showed that growth at 100°C is in all respects similar to that of cultures at moderate temperatures. Enzyme preparations derived from cultures at 5°C intervals between 70 and 100°C were used to determine the temperature range. For all nine enzymes tested, the optimum temperature was found to be 67°C; the latter was independent of the growth temperature. Differences were found, however, with respect to the maximum temperature of individual enzymes, and three groups, with maxima between 70 and 80°C, 80 and 90°C and 90 and 100°C can be distinguished. Again, there was no correlation with the growth temperature. Stability experiments also revealed that enzymes from the same organism can have different thermal properties: Some were found to be quite thermolabile (e.g. the pyruvate kinase), while others (e.g. hexokinase and glutamate-pyruvate transaminase) exhibited a high thermostability. These properties were not related to the growth temperature within the 70–100°C range, too. Six of the enzymes tested could be stabilized by their respective substrates, but the degree of protection varied for individual enzymes. Three enzymes (acetate kinase, glutamate dehydrogenase and myokinase) could not be stabilized by their substrates. Comparative experiments with the hexokinase suggested, that the thermal integrity of the enzymes is better protected within the cell as compared to the stability of the enzyme preparations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00411071
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  • 12
    Electronic Resource
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    Effects of sodium chloride on the plasma membrane of halotolerant Dunaliella primolecta: an electron spin resonance study (1982)
    Springer
    Archives of microbiology 131 (1982), S. 184-190 
    Details
    ISSN: 1432-072X
    Keywords: Dunaliella primolecta ; Malotolerant ; Adaptation ; Plasma membrane ; ESR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Electron spin resonance spectroscopy was used to monitor the in vivo microviscosity of the plasma membrane and lipid extracts of the salt tolerant alga, Dunaliella primolecta. The fluidity of the plasma membrane decreased as the algae were adapted to and suspended in higher sodium chloride concentrations [2–24% (w/v)]. Both biochemical modification and a physical interaction between Na+ and lipids were implicated. When the microviscosity of the plasma membrane and that of lipid extracts were determined as a function of temperature, two or three lipid phase transformations were observed. There were always transformations at 9–14° C and 39–43° C. These were interpreted as the onset and completion of the lipid phase transition of at least a major lipid component of the membrane, possibly the entire membrane. These transformation temperatures were independent of the salt concentration to which the algae were adapted or suspended. This suggests that D. primolecta exists with some of its membrane in the solid-fluid mixed lipid state. With a NaCl concentration of 8% (w/v) or greater in the growth medium, a third transformation occurred around 20–22° C. It was the result of a lipid-lipid interaction and was not related to adaptation.
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    URL: http://dx.doi.org/10.1007/BF00405876
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  • 13
    Electronic Resource
    Electronic Resource
    Photosensory transduction in the flagellated alga, Euglena gracilis (1983)
    Springer
    Archives of microbiology 134 (1983), S. 204-207 
    Details
    ISSN: 1432-072X
    Keywords: Photosensory ; Cations ; pH ; Flagellated ; Algae ; Adaptation ; Euglena gracilis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Euglena were cultured under 3 W m-2 constant white light. In culture medium, cells show immediate and long lasting step-down photophobic responses and photoaccumulation behavior to blue light if dim red light-adapted for 30 min. However, if cells are suspended in buffered, saltcontaining solutions (adaptation buffers), strong step-down photobehavior and photoaccumulation responses are not observed for several hours. These behaviors gradually increase in strength to reach a maximum after 6–12 h; after which a stable response is maintained. The relative rates of appearance and the relative strengths of the responses are influenced by the concentrations of Ca2+ and K+, but not H+ or Na+ ions, in the adaptation buffers. Expression of the stepdown photobehavior thus requires that the cells adapt to the chemical environment in which they are suspended.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00407758
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  • 14
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    Ultra-violet mutagenesis of Synechocystis sp. 6701: mutations in chromatic adaptation and phycobilisome assembly (1984)
    Springer
    Archives of microbiology 138 (1984), S. 237-243 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Synechocystis 6701 ; Phycobilisomes ; Ultra-violet ; Mutagenesis ; Assembly ; Chromatic ; Adaptation ; Rods ; Cores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mutations affecting pigmentation of the cyanobacterium Synechocystis sp. 6701 were induced with ultraviolet light. Two mutants with phycobilisome structural changes were selected for structural studies. One mutant, UV08, was defective in chromatic adaptation and incorporated phycoerythrin into phycobilisomes in white or red light at a level typical of growth in green light. The other mutant, UV16, was defective in phycobilisome assembly: little phycocyanin was made and none was attached to the phycobilisome cores. The cores were completely free of any rod substructures and contained the major core peptides plus the 27,000 Mr linker peptide that attaches rods to the core. Micrographs of the core particles established their structural details. Phycoerythrin in UV 16 was assembled into rod structures that were not associated with core material or phycocyanin. The 30,500 Mr and 31,500 Mr linker peptides were present in the phycoerythrin rods with the 30,500 Mr protein as the major component. Phycobilisome assembly in vivo is discussed in light of this unusual mutant.
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    URL: http://dx.doi.org/10.1007/BF00402128
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  • 15
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    Theoretical considerations on growth kinetics and physiological adaptation of nutrient-limited phytoplankton (1984)
    Springer
    Archives of microbiology 140 (1984), S. 96-100 
    Details
    ISSN: 1432-072X
    Keywords: Physiology ; Adaptation ; Growth ; Droop ; Monod
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In many experimental ecological studies on phytoplankton species the growth response of an organism to the prevailing environmental conditions have been studied. Curves relating specific growth rate (μ) to the external nutrient concentration (S) have been constructed to compare nutrient-limited growth of different species under steady state conditions. Microorganisms adapt their physiology to a certain limitation in order to optimize growth. Therefore the shape of the μ/S curve is closely related to the way a micoorganism adapts its physiology. To see how physiological adaptation and growth rate are interconnected to each other, both can be related to the internal concentration of the growth-limiting nutrient. How the growth rate is related to the internal nutrient concentration is presented in a mathematical equation. Many phytoplankton species during growth under different nutrient limitations show a linear relationship between μ and the reciprocal value of the internal nutrient content (= Yield). This was originally observed by Droop. The model presented here gives a theoretical explanation of this phenomenon.
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    URL: http://dx.doi.org/10.1007/BF00409779
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  • 16
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    Genotype X environment interaction for bunch yield and its components in the oil palm (Elaeis guineensis, Jacq.) (1983)
    Springer
    Theoretical and applied genetics 64 (1983), S. 133-136 
    Details
    ISSN: 1432-2242
    Keywords: Stability ; Adaptation ; Fitness trait ; Bunch yield ; Oil palm ; Elaeis guineensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary There were significant differences between hybrids for number of bunches (NB), mean bunch weight (MBW) and fresh fruit bunch yield (FFB). For the hybrid population as a whole, significant hybrid X year (environment) effects were also observed for the two yield components and for yield per se. The linear component of the hybrid X year effect was also significant. There were highly significant and positive correlations between FFB, NB and MBW hybrid means and the regression co-efficients of the hybrid means on the environmental index. There were no significant associations between these means and mean square deviations from regression (s2d) for these traits.
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    URL: http://dx.doi.org/10.1007/BF00272720
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  • 17
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    Genotype x environment interaction in dairy cattle and its role in breeding programmes (1983)
    Springer
    Theoretical and applied genetics 66 (1983), S. 93-99 
    Details
    ISSN: 1432-2242
    Keywords: Lactation ; Milk yield ; Herd production ; Adaptation ; Dairy cattle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Eighty thousand, one hundred and eleven records of the Israeli dairy herdbook for the period of 1973–1977 were studied and examined to determine the existence of Genotype x Environment Interaction (GxE) as affecting milk yield in kg per day between calvings. Various quantitative measures of environment were used while the genotypes were evaluated as the average performance of each sire's daughters in a whole range of environments. When the environment was evaluated as level of production, the relative importance of the interaction was found to be very low. Furthermore, the linear dependence on the interaction of the individual sires with the environments was found to be inconsistent with time, meaning that no justification was found for using specific adaptation patterns of genotypes to these environments. When lactation number and given time periods were used as environments, significant interactions were found between genotypes and environments. Results of the analyses of Genotype x Lactation interaction imply that the interaction values, to a certain degree, confused the differences between the sires when based on first lactation records. We therefore conclude that the need exists to expand the basis of sire evaluation, including the addition of data on successive lactation periods beyond the first one. We maintain that the genetic characteristic for this phenomenon is the “lactations development” of a sire, i.e., the performance of its daughters during the different lactations. The “maturing rhythm” of a sire may be regarded as a dynamic expression of the genetic makeup controlling lactation development. Furthermore, the prospect of selecting sires of bulls for early or late maturing could provide a new tool for the dairy cattle breeder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265180
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  • 18
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    Analysis of the rye chromosome constitution and the amount of telomeric heterochromatin in the widely and narrowly adapted hexaploid triticales (1981)
    Springer
    Theoretical and applied genetics 60 (1981), S. 145-149 
    Details
    ISSN: 1432-2242
    Keywords: Triticale ; Rye ; Hexaploids ; Adaptation ; Chromosomal substitutions ; Modified chromosomes ; Telomeric heterochromatin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Investigations were made on the rye chromosome constitution and on the presence of telomeric heterochromatin in rye chromosomes of the 26 most widely and 24 most narrowly adapted triticale strains. Among widely adapted lines, 22 (85%) had a complete rye genome and four triticales only had chromosomal R-D genome substitutions. Twenty-three (96%) of the 24 most narrowly adapted triticales had substitutions between the chromosomes of the R and D genomes. The most widely adapted triticales accumulated fewer modified rye chromosomes in comparison to narrowly adapted lines. They had from one to three rye chromosomes with heterochromatic deletions: 46% of widely adapted lines had two modified rye chromosomes; 34% had three modified rye chromosomes, and 19% had a single modified rye chromosome. In widely adapted strains, the 1R, 4R, 5R and 6R modified chromosomes were observed; they were present in 80%, 73%, 50% and 11% of the cases, respectively. The most narrowly adapted triticales had from two to four modified rye chromosomes: 58% of the strains had three modified rye chromosomes; 29% had four modified rye chromosomes and 12% had two modified rye chromosomes. The modified 4R and 5R chromosomes were present in all of these lines. The 1R (modified), 6R (modified) and 7R (modified) were found in 83%, 25% and 16%, respectively, of the narrowly adapted strains. Results support the previous observations (Pilch 1980b) that a wide adaptation of hexaploid triticales is associated with the presence of the full potential of rye genome, and that it is independent of the amount of telomeric heterochromatin possessed by rye chromosomes.
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    URL: http://dx.doi.org/10.1007/BF00264517
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    Effects of nickel on the rates of endocytosis, motility, and proliferation inTetrahymena and determinations on the cell content of the metal (1983)
    Springer
    Protoplasma 118 (1983), S. 140-147 
    Details
    ISSN: 1615-6102
    Keywords: Nickel ; Endocytosis ; Motility ; Proliferation ; Cellular nickel content ; Adaptation ; Tetrahymena pyriformis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary At concentrations above 1 mM, nickel has a dose-dependent effect on the rate of food vacuole formation in cells in the growth medium, proteose peptone (PP); total inhibition of endocytosis occurs within 10 minutes in 6mM nickel. However, only a 10 times lower concentration of nickel is tolerated by starved cells in an inorganic salt medium, a difference which may be ascribed to the high binding property of nickel to organic material. In the PP medium, nickel affects cell motility by increasing the rate of movement at a concentration of 1 mM, and by causing immobilization after 30 minutes in 6mM nickel; a spontaneous, partial recovery of cell motility is seen after 3 hours in 6 mM nickel. The effects of nickel on endocytosis and cell motility are reversible after removal of nickel. Cell proliferation continues at a reduced rate in 1 mM nickel, while only 1 1/2 cell doublings are achieved in 3 mM nickel during a 72-hour exposure, and no proliferation occurs in 6mM nickel, where an increasing cell mortality is observed after 12 hours. The cell content of nickel relates initially to the external concentration of the metal; however, cells in 1 mM nickel are capable of maintaining a constant content of the metal, whereas in 3 mM, the rate of accumulation is reduced after 3 hours, and cells in 6mM nickel accumulate the metal at a constant rate. All nickel-treated cells contain small refractive granules, previously proposed as representing an ion-regulating system, and the apparent adaption ofTetrahymena to the effects of nickel may be ascribed to such a regulation of the intracellular concentration of the metal.
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    URL: http://dx.doi.org/10.1007/BF01293071
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    Adaptational changes of plastids in the leaves ofLigustrum ovalifolium Hassk. var.aureum at different light intensities (1984)
    Springer
    Protoplasma 122 (1984), S. 132-137 
    Details
    ISSN: 1615-6102
    Keywords: Adaptation ; Light intensity ; Ligustrum ; Plastids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The capacity of adaptation and the range of adjustment to different light conditions in fully expanded mutant leaves were studied on an aurea variety of privet (Ligustrum ovalifolium Hassk. var.aureum). Whenever the light conditions are altered leaves respond immediately. Although adaptational changes in leaf thickness are not possible, the change in colour, as well as changes in pigment concentrations take place within several days. With increasing light intensity there is a marked decline in chlorophyll concentration and the carotenoid yield becomes much higher. Under low light conditions the chlorophyll content is high, while the carotenoid concentration drops significantly. The mutant chloroplasts from green leaves always have a well developed thylakoid system. The only difference between young green leaves (DG1) and older regreened ones (DG2) is in the number of thylakoids per granum (grana in older leaves consist of more thylakoids), while the stacking degree of thylakoids remains about the same (74 and 77% respectively). Depending on the previous light conditions fine structure of plastids in yellow leaves differs considerably. Young yellow leaves (Y0) contain plastids with longitudinal arrays of dilated thylakoids and prothylakoid bodies occasionally. Plastids from primarily green leaves which turned yellow afterwards in strong sunlight (Y1) are characterized by thylakoids densely packed into cup-shaped stacks, or large vesicles originating from dilated thylakoids. The stacking degree of thylakoids in sun exposed yellow leaves (determined only in Y0 leaves) is extremely low and reaches only 29%.
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    URL: http://dx.doi.org/10.1007/BF01279446
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    Differentiation in habitat response in taxodium distichum, taxodium mucronatum, platanus occidentalis, and liquidambar styraciflua from the United States and Mexico (1974)
    Springer
    Plant ecology 29 (1974), S. 1-10 
    Details
    ISSN: 1573-5052
    Keywords: Adaptation ; Habitat response ; Illinois ; Mexico ; Phenology ; Photoperiod ; Stipules ; Temperature ; Texas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Habitat specialization in populations of three broadly distributed trees includes adaptive differentiation to day length and temperature. Low sensitivity to environmental cues is the adaptive strategy of the southernmost populations (from northeastern Mexico). Early cessation of growth and sensitivity to the environment is adaptive for the northernmost populations (southern Illinois). Intermediate responses characterize trees of Texas. In a comparison under four photoperiod-temperature conditions, the Mexico plants were adapted to the longest growing season. Under out-of-doors conditions in central Texas, these trees from Mexico continue to demonstrate adaptive strategies different from those of Texas or Illinois trees. Stipule production and leaf area inPlatanus showed modifications correlated with latitude. Northernmost trees had the smallest leaves and did not produce stipules under 12-h day lengths and 24–15 °C temperatures. The Mexico trees had stipules under each of the four experimental conditions. The results suggest that populations of deciduous trees in a given climate are selected toward convergence in some responses to that climate. As a result, populations of the three trees resemble each other in behavior in a given ecosystem.
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    URL: http://dx.doi.org/10.1007/BF02390890
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    Phenological spread in plants: A result of adaptations to environmental stochasticity? (1980)
    Springer
    Plant ecology 43 (1980), S. 83-86 
    Details
    ISSN: 1573-5052
    Keywords: Adaptation ; Colonization ; Environmental stochasticity ; Phenology ; Weather variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Plant species co-inhabiting a given geographical region often have distinetly different times of flowering. It is shown that such phenological spread, duc to short-term stochastic variation in weather variables, relaxes competition for empty sites to be colonized by diaspores. For sufficiently large spreads stable coexistence becomes possible. The applicability of the proposed hypothesis to the observed instances of phenological spread is discussed and shown to extend beyond that of other current theories.
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    URL: http://dx.doi.org/10.1007/BF00121020
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    Patterns of trait variation in the diploid wheats (Triticum, Aegilops) and the tetraploid speciesTriticum diccocoides (1983)
    Springer
    Plant systematics and evolution 143 (1983), S. 257-275 
    Details
    ISSN: 1615-6110
    Keywords: Angiosperms ; Poaceae ; Aegilops ; Triticum ; T. diccocoides ; wheat ; Adaptation ; trait variation ; factor analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eighteen earliness and morphological traits were examined in from 2 to 14 lines each of 10 diploid members of the wheat complex,Triticum-Aegilops, and 15 lines of the tetraploid speciesTriticum diccocoides. In general, earliness traits have the greatest relative between line vs. within line variation of all the traits examined. Within species, earliness traits are the principle set of characters around which evolve between line trait differences, one of the most important oich is leaf dimensions. At the genus level, earliness traits are independent of leaf dimensions and plant height characters. Thus, the pattern of evolution at the genus level is different from that exhibited in each of the species. Biological and evolutionary implications of these findings are discussed.
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    URL: http://dx.doi.org/10.1007/BF00986608
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    Nitrate production in the rhizosphere of Plantago species (1981)
    Springer
    Plant and soil 61 (1981), S. 43-52 
    Details
    ISSN: 1573-5036
    Keywords: Adaptation ; Allelopathy ; Ecophysiology ; Grassland ; Plantago ; Nitrate production ; Nitrate reductase ; Nitrate uptake ; Nitrification ; Nitrifying bacteria ; Rhizosphere ; Root environment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The production of nitrate in an old established dune grassland soil and its uptake by plants was studied by comparing amounts of mineral nitrogen and numbers of nitrifying bacteria in the rhizosphere on the one hand, and on the other accumulated nitrate and levels of nitrate reductase (NaR) of individual plants of three Plantago species,i. e., P. major, P. lanceolata andP. coronopus. For these three Plantago species andP. media basal levels of NaR in the absence of nitrate were determined in plants grown in culture solutions. The basal NaR levels ofP. major andP. media (species occurring on nutrient-rich soils) were significantly higher than those ofP. lanceolata andP. coronopus (species found on nutrient-poor soils). NaR activity increased in the presence of nitrate and was suppressed by ammonium. From the numbers of nitrifying bacteria in the rhizosphere and NaR activity in the leaves it was concluded that nitrate was produced in the root environments of the three Plantago species and that the compound was taken up by the plants. NaR activities and numbers of nitrifying bacteria were higher for individuals ofP. major than for those ofP. lanceolata andP. coronopus. No correlation was found between the ammonium levels and the numbers of nitrifying bacteria in the soil, and no indications of inhibition of nitrifying bacteria in the rhizosphere were obtained. For individuals ofP. lanceolata a correlation was found between the numbers of nitrifying bacteria in the soil and NaR activity in the leaves. The results are discussed in relation to the ecological habitats of the three species.
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    URL: http://dx.doi.org/10.1007/BF02277361
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    Obtention d'un mutant deRhizobium meliloti adapté aux cultures de luzerne en terres acides (1981)
    Springer
    Plant and soil 60 (1981), S. 99-110 
    Details
    ISSN: 1573-5036
    Keywords: Adaptation ; Luzerne ; Mutant ; Rhizobium meliloti ; Terres acides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Resume Un mutant acido-tolérant deR. meliloti a été isolé. Le caractère de résistance en milieu acide n'a pas été obtenu par adaptation sur des milieux de plus en plus acides mais par mutagenèses successives provoquées par la N-méthyl-N'nitroso-N-nitrosoguanidine (NTG) et sélection sur milieu acide de façon à rendre stable le caractère acido-tolérant. Ce mutant acide présente la propriété de se développer plus lentement que la souche sauvage sur milieu pauvre. Ceci ne l'empêche pas de présenter sensiblement la même efficience que cette dernière à pH voisin de la neutralité en milieu synthétique. L'étude comparative de l'efficience de la souche parentale et de la souche mutée sur la luzerne cultivée en terre acide est rendue difficile du fait de la présence de nitrates qui réduit la nodulation et inhibe l'action de la nitrogénase: par épuisement, en effectuant une culture dense de luzerne sur cette terre, il est possible de mettre en évidence ensuite l'activité symbiotique importante à pH 5,9 du mutant par rapport à la souche sauvage.
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    Water relations, ethylene production, and morphological adaptation ofFraxinus pennsylvanica seedlings to flooding (1984)
    Springer
    Plant and soil 77 (1984), S. 183-192 
    Details
    ISSN: 1573-5036
    Keywords: Adaptation ; Adventitious roots ; Ethylene ; Flooding ; Fraxinus pennsylvanica ; Lenticels ; Turgidity ; Water potential ; Water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Fraxinus pennsylvanica Marsh. seedlings that were 150 days old adapted well to flooding of soil with stagnant water for 28 days. Early stomatal closure, followed by reopening as well as hypertrophy of lenticels and formation of adventitious roots on submerged portions of stems appeared to be important adaptations for flood tolerance. Leaf water potential (ψ1) was consistently higher in flooded than in unflooded seedlings, indicating higher leaf turgidity in the former. This was the result of (1) early reduction in transpiration associated with stomatal closure, and (2) subsequently increased absorption of water by the newly-formed adventitious roots as stomata reopened and transpiration increased. Waterlogging of soil was followed by large increases in ethylene content of stems, both below and above the level of submersion. Formation of hypertrophied lenticels and adventitious roots on flooded plants was correlated with increased ethylene production. However, the involvement of various compounds other than ethylene in inducing morphological changes in flooded plants is also emphasized.
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    Physiological, morphological, and growth responses ofPlatanus occidentalis seedlings to flooding (1982)
    Springer
    Plant and soil 66 (1982), S. 243-255 
    Details
    ISSN: 1573-5036
    Keywords: Adaptation ; Adventitious roots ; Ethylene ; Flooding ; Growth of seedlings ; Lenticels ; Platanus occidentalis ; Stomatal aperture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Flooding ofPlatanus occidentalis L. seedlings for up to 40 days induced several changes including early stomatal closure, greatly accelerated ethylene production by stems, formation of hypertrophied lenticels and adventitious roots on submerged portions of stems, and marked growth inhibition. Poor adaptation ofPlatanus occidentalis seedlings to soil inundation was shown in stomatal closure during the entire flooding period, inhibition of root elongation and branching, and death of roots. Some adaptation to flooding was indicated by (1) production of hypertrophied lenticels which may assist in exchange of dissolved gases in flood water and in release of toxic compounds, and (2) production of adventitious roots on stems which may increase absorption of water. These adaptations appeared to be associated with greatly stimulated ethylene production in stems of flooded plants. The greater reduction of root growth over shoot growth in flooded seedlings will result in decreased drought tolerance after the flood waters recede. The generally low tolerance to flooding of seedlings of species that are widely rated as highly flood tolerant is emphasized.
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    Early ontogeny of white sucker,Catostomus commersoni, with steps of saltatory development (1980)
    Springer
    Environmental biology of fishes 5 (1980), S. 191-224 
    Details
    ISSN: 1573-5133
    Keywords: Adaptation ; Benzidine stain ; Catostomid ; Discontinuity theory ; Ecomorphology ; Embryology ; Fish ; Haemoglobin stain ; Hatching ; Peroxidase ; Thresholds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Frequent and detailed observations of arbitrary stages revealed a saltatory pattern of development in the early ontogeny of fluvial spawning white sucker. Considered as adaptations for respiration were: i) expansion of the surface area of the yolk through a change in yolk shape, ii) the presence of carotenoid pigment in the yolk, iii) a large caudal vein sinus, iv) coverage of the yolk surface with capillaries of bilaterally paired vitelline plexi, and v) a large pair of vitelline veins. The ability to swim developed slowly and well after hatching. Young suckers would therefore spend most of the eleutheroembryonic phase in the interstices of the rock substrate of the spawning ground. The change from a benthic to pelagic mode of existence occurred with swimbladder inflation and before the start of exogenous feeding.
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    Morphological and structural studies of poly(gly-gly-ala) (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1049-1057 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ultrastructural morphology and x-ray and electron diffraction of poly (Gly-Gly-Ala) have been studied. The polymer has two forms; the first, form I possesses a super-folded cross-β structure, long fibers of which show some twisting and intertwining. Form II precipitates in a less distinct fibrous form from aqueous solution. The x-ray diffraction and oriented electron diffraction data suggest that form II is a polyglycine II helix situated in a monoclinic cell with dimensions a = 8.86 Å, b = 22.0 Å, c = 9.42 Å, and β = 90°. Combined with the morphological evidence it appears likely that form II is also in an antiparallel superfolded array.
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    Supporting evidence for an extended helical conformation in Poly(L-glutamic acid) (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1099-1101 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360100615
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    A statistical mechanical theory of unfolding of globular proteins induced by preferential binding of solvent components in water-organic solvent systems (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1081-1098 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A statistical mechanical model was developed for use in connection with the problem of preferential binding of solvent components to proteins and of conformational transition in water-organic solvent systems. The model is a statistical one for the conformational transition of globular proteins induced by the adsorption of solutes in the solution, considered as a nearest-neighbor problem in statistical mechanics. Although a few illustrative examples are given, the actual interpretations of the experimental data using this theory are reserved for a later paper.
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    The effects of aqueous neutral-salt solutions on the melting temperatures of deoxyribonuclcic acids (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1103-1103 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.360100616
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    Representation of a protein molecule as a tree and application to modular computer programs which calculate and modify atomic coordinates (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1121-1138 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concept and representation of a logical tree as defined in computer science is applied to obtain a suitable representation of protein molecules in computer programs which handle or calculate atomic coordinates of protein molecules. On the basis of this analysis and of the analysis of the calculation and modification of the structure of a protein from bond lengths, bond angles, and dihedral angles, which is reproduced in an appendix, program modules which accomplish the various required computations are described. Three such modules are given in Iverson notation; in fact, it is hoped that this article will serve as a reasonably complete basis for the preparation of machine programs by moderately proficient programmers.
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    Optical properties of the polyglycine II helix (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1207-1212 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dichroism spectrum obtained from a dilute aqueous solution of poly (ala-gly-gly) resembles that described for charged polypeptides such as the salt form of poly glutamic acid. A similar spectrum is found for films cast from aqueous solution where x-ray studies reported elsewhere have indicated a poly-glycinc II conformation. Evidence is presented for a heat induced poly-glycine II to unordered state transition similar to that described for collagen. The interpretation of this, the first observation of the optical properties of a poly-amino acid in the poly glycine II conformation, is further rationalized on the basis of spectra obtained from a number of polypeptides whose conformation approaches that of a 31 helix.
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    Quenching of the emission of tryptophan, tyrosine, and serum albumins by cupric ion (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1229-1242 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of cupric ion on the emission of tryptophan, tyrosine, and serum albumins is studied by emission spectroscopy and lifetime measurements. It is found that whenever cupric ion is bound to tryptophan or tyrosine, their emissions are quenched completely. The quenching may be due to an electron transfer mechanism. The fluorescence of complexes of cupric ions with serum albumins is partially quenched; this is because energy is transferred from tryptophan to the complexed cupric ions by a dipolar energy transfer mechanism. It is deduced from the present study that the tryptophan in the human serum albumin molecule is between 11 and 16 Å from the nearest eupric ion binding sites (assumed to be at the surface of the protein) and that one of the tryptophan in the bovine serum albumin molecule is very close to the cupric ion binding sites and the other is near the center of the bovine serum albumin molecule. It is also found that the deuterium solvent effect on serum albumin fluorescence is very small, and that the quenching of bovine serum albumin fluorescence at the N-F transition is the result of quenching of the fluorescence of both tryptophans. The phosphorescence lifetime apparatus, capable of measuring decay times of signals with intensities changing over a few orders of magnitude, and the ratio spectrofluorometer, both of which were constructed in this laboratory, are also described.
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    Volume and sound velocity changes associated with coil-β transition of poly (S-carboxymethyl L-cysteine) in aqueous solution (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1253-1260 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The measurements were made for the volume and the sound velocity changes (ΔV and ΔU) on titrating the sodium salt of poly (S-carboxymethyl L-cysteine) with dilute HCl. For the reaction, —COO- + H+ → —COOH, ΔV per mole of H+ bound was + 12. 7 ml and +11. 4 ml in salt-free and 0. 2 M NaCl solutions, respectively. Corresponding ΔU was about -13 cm/sec in salt-free polymer solution where 11.5 mM carboxylate ion reacts with equimolar hydrogen ion. ΔV associated with the coil-to-β transition was found to be +2. 35 ml in H2O and +1. 90 ml in 0. 2 M NaCl per mole of amino acid residue, respectively. These values are larger than those obtained for the coil-to-helix transition of poly (L-glutamic acid). ΔU for the transition was about -30 cm/sec in salt-free solution of polymer concentration 0.0115 mole/liter. Possible sources of ΔV and ΔU for reaction; coil → β, are (1) the formation of void volume and (2) the changes in the extent of solvation in amide linkage and in side chain.
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    Energy transfer between tryptophans and aromatic ligands in apomyoglobin (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1317-1329 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding of three aromatic molecules to apomyoglobin has been investigated. In each case equilibrium dialysis studies and tryptophan fluorescence quenching studies indicate that a one to one complex has been formed. The fluorescence quenching studies further suggest that the binding of the aromatic molecules is at the heme site with possible involvement of the arginine CD3. Xenon, which is known to quench the fluorescence of aromatic hydrocarbons, is found to be bound to apomyoglobin-aromatic molecule complexes and quenches the emission of the aromatic molecule in the complexes. Oxygen quenches pyrene fluorescence in water solution but does not quench the pyrene fluorescence from the apomyoglobin-pyrene complex. This is explained by a slower rate of diffusion of oxygen to pyrene in the apomyoglobin-pyrene complex.
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    Pressure independence of the rotor speed-induced aggregation of DNA (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1365-1369 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rotor speed-dependent aggregation of T4 DNA in the analytical ultracentrifuge is studied in the presence of high pressure generated by compressed nitrogen gas in the cell. The extents of aggregation at various speeds are found to be practically the same in the presence and absence of pressure.
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    Time dependent model for hemoglobin and allosteric enzymes. II. (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1331-1349 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The time-dependent theory developed in Part I is specialized to treat tetrameric hemoglobin, and the results of the theory for dimeric-and tetrameric hemoglobin are compared with data on the kinetics of the reactions of hemoglobin with carbon monoxide and oxygen at various salt concentrations for the case of large concentration of ligand relative to that of hemoglobin. The fit of the theoretical results to the data suggests that hemoglobin at a 2 M salt concentration is predominantly dimeric and that the tetramer should be taken as the functional unit to explain the kinetics of the reactions of normal hemoglobin. A relationship is established between the time-dependent theory arid Adair's Intermediate Compound Hypothesis (I.C.H.) for hemoglobin, as brought to its present state by Gibson and Roughton. A generalization (G.I.C.H.) of the I.C.H. is presented and is shown to be equivalent to the time-dependent theory in the limit of infinite ligand concentration. The I.C.H. is shown to be an excellent approximation to the centralized theory (G.I.C.H.) in this limit.
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    Optical activity of dye-apohemoglobin complexes (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1421-1425 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Announcement (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1427-1428 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Comparaison entre oligoribonucleotides et oligodesoxyribonucleotides. I. Formation des doubles helices (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1429-1454 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ability of oligodesoxyribonucleotides of various chain lengths to form complexes has been compared with that of oligoribonucleotides. Four series of oligonucleotidcs were prepared and investigated, i.e., dCn at acid pH versus rCn, dAn and dTn versus. rAn and rUn at neutral pH. The results indicate that in dilute solution, the formation of complexes is greatly facilitated in the case of desoxyoligomers and occurs for shorter oligomere than in the corresponding ribooligomers. The spectrophotometric titration of deoxyribooligo C indicates the appearance of two pK values in the 4-5 pH region characteristic of the double-stranded form, which occurs for much shorter dCn than rCn. The circular dichroism (CD.) spectra of deoxycytidylies in dilute solution starting from the trimer are conservative, characteristic of the double-stranded helical form of poly C at acid pH. In contrast, the CD spectra of a series of corresponding ribo Cn, under identical conditions is of nonconservative character similar to that of the single-stranded form of poly C at neutral pH, but differs in the band position. This spectrum is called intermediate. Only at higher concentrations of oligonucleotidcs (i.e., 10-3Minstead of 10-4M) does the circular dichroism spectrum of longer ribocytidylics assume conservative character. Thermal denaturation of deoxycytidylces at acid pH are strongly dependent on chain length and concentration, its one would expect for a cooperative helix-coil transition. The circular dichroism spectra measured at different temperatures shows one isosbestic point. In dilute solution, the standard-state enthalpy change found was 5-6 kcal/mole for higher oligomers (dC7). These properties are all in agreement with a structural transition from the d-Cn double-stranded form to a coil for n 〉 3. Studies of dAn and dTn in solutions of high ionic strength at low temperature indicate that complex formation occurs already at the level of trimer and for high oligomers. Under identical conditions a complex between rAn and rUn is detected only for oligomers longer than the hexamer. The nature of the “intermediate” form of oligoribo C at acid pH and low temperature was investigated by sedimentation and circular dichroism. A model of rCn is proposed of linear molecules which are partially double-stranded and partially single-stranded, which probably are slowly rearranged by “slippage” into a regular-double-stranded helical form.
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    Physicochemical studies of oligodextran. I. Molecular weight dependence of intrinsic viscosity, partial specific compressibility and hydrated water (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1513-1524 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The number average molecular weight, Mn, of low molecular weight dextran was determined through endgroup analysis, and the intrinsic, viscosities of these materials in aqueous solution were determined at 25°C. The ultrasonic velocities in their aqueous solutions were also measured at 25 and 45°C. As concerns the molecular weight dependence of the intrinsic viscosity, partial specific compressibility of solute and the hound water around the solute, the following results were obtained. (1) log [η]-log Mn and [η]/Mn0.5 - Mn0.5 plots were in accord with the Mark-Houwink and Stockmayer-Fix-man equations respectively for Mn 〉 2, 000, but these plots deviated from the equations for Mn 〈 2, 000. (2)The partial specific compressibility, β1°, of dextran is expressed by following equation for Mn 〈 2,000: β1° = 10-12 × (13.6 log Mn - 51.7) (cm2/dyne). In contrast, it, becomes the constant value, -- 7.3 × 10-12 cm2/dyne, for Mn 〉 2,000. (3) The amount of bound water of dextran calculated from the sound velocity measurement lakes constant value of 0.17 ml g for Mn 〉 2, 000, but the amount of hydration increase with decreasing molecular weight for Mn 〈 2,000. From these results, a dextran molecule in aqueous solution is expected to change its conformation from random coiling to uncoiling stretched form at the molecular weight of around 2, 000 or about 12 glucose units.
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    Rotatory properties of molecules containing two peptide groups: experimental and theoretical results (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1559-1581 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optical rotation studies were performed on five compounds containing two peptide groups. Four of the molecules were confined to restricted regions of conformational space by the presence of closed rings. Solvent and temperature were varied, and theoretical calculations were done for each compound covering the appropriate conformational space. The interpretation which results is qualitatively successful over the conformational regions covered by the compounds. Quantitative correlation between theory and experiment will require compounds of high rigidity.
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    Conformational energy calculations on alginic acid. II. Conformational statistics of the copolymers (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1617-1623 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energy maps have been calculated for α-D-mannuronic acid (1-4) α-L-guluronic acid and for α-L-guluronic acid (1-4) β-D-mannuronic acid. These have been used, together with maps previously calculated for the homomonomeric dimers, to estimate the characteristic ratios and Kuhn lengths of the alternating copolymer and of a stochastic copolymer similar in composition to that extracted from L. digitata.The results show that the alternating copolymer is less extended than either homopolymer. Kuhn lengths calculated for the stochastic copolymer agree well with experimental results on high ionic strength solutions of alginate isolated from L digitata.
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    Conformation of poly-S-carboxyethyl-L-cysteine in aqueous solutions (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1635-1648 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly-S-carboxyethyl-L-cysteine, a higher side-chain homolog of poly-S-carboxymethyl-L-cysteine, has been prepared from poly-S-carbobenzoxyethyl-L-cysteine with hydrogen bromide in chloroform or acetic acid. The polymer is found to be in the β-conformation of an antiparallel arrangement of polypeptide chains in solid films, both in acid and salt forms, when examined by infrared spectra. Aqueous solutions of t he polymer have been investigated by measurements of rotatory dispersion and circular dichroism as well as by infrared spectra in D2O. These properties show sharp changes around pH 5.5, as the pH of solution is varied. At higher ionization the polymer is randomly coiled, but at lower ionization it is in the β-conformation. Dependence of the rotatory properties upon polymer concentration as well as on ionic strength has been observed even at the lowest degree of ionization attained, and this has been attributed to the formation of intermolecular β-conformation in solutions. The β-structure is characterized by a negative circular dichroic band at 223 mμ and a positive dichroic band at a wavelength lower than 200 mμ, and furt her by a negative bo value, -140°. The pH-induced coil-β transition of the polymer is compared with that of poly-S-carboxymethl-L-cysteine.
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    Calorimetry of rat tail tendon collagen before and after denaturation: the heat of fusion of its absorbed water (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1681-1699 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The specific heat, of rat tail tendon at various water contents was measured as a function of temperature. The resulting graphs showed peaks arising from the melting, near 50°C, of helical material in the collagen, and from the melting of absorbed water in the range -40°C to 0°C. The heat of melting of helical material was 11.7 cal per gram of dry tendon. Determination of the heat and temperature of fusion of the absorbed water allowed resolution of the water into four states in the case of tendon before denaturation, and three states after denaturation. The four states are (1) water not freezable on cooling to - 70°C, (2) freezable water with-both heat and temperature of fusion different from the values for ordinary water, (3) freezable water with the heat of fusion of ordinary water, but a different temperature of fusion, and (4) water not distinguished from ordinary water. The fourth state was absent in denatured tendon. The results are discussed in terms of increasing size of clusters of absorbed water molecules.
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    Masthead (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.360101001
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    Induced optical activity of acridine orange bound to poly-S-carboxymethyl-L-cysteine (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1743-1757 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The absorption and rotatory properties of acridine orange-poly-S-carboxymethyl-L-cysteine system in water and in 0.2 M NaCl have been measured at different pH and polymer-to-dye mixing ratios. The absorption spectra indicate that the dyes are bound to the polymer in dimeric or highly aggregated forms. At neutral pH where the polymer is randomly coiled, no optical activity is induced on the absorption bands of bound acridine orange. At acid pH where the polymer has the β-conformation, a pair of positive and negative circular dichroic bands occur at each of the absorption bands, centered around 458 and 261 mμ. The signs of those bands are opposite to those found for α-helical poly-L-glutamic acid. A model for the binding of dye to the β-form polymer is presented, in which dimeric dyes are attached to ionized carboxyl groups and slack one another to form linear arrays on both sides of an extended polypeptide chain. The observed circular dichroism spectra can be explained by the Tinoco's exciton mechanism, based on this model. Low molecular weight poly-S-carboxymethyl-L-cysteine induces quite a different circular dichroism on bound acridine orange.
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    The circular dichroism in the ultraviolet of aminoacridines and ethidium bromide bound to DNA (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1853-1863 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dicrosim (CD) spectra of complexes of DNA with ethidiun bromnide, profiavine, 9-aminoacridine and 4-etliyl-9-amino-acridine have been determined between 220 and 450 nm, the range lieing extended to 600 nm for ethidiufm bromide. The variation of the magnitude of the visible and near - ultraviolet CD spectra of ethidium bromide - DNA complexes with the amount of ligand bound (r) suggests a common binding position with profiavine. On the other hand, 4-ethyl-9-aminoacndine complexed to DNA shows CD spectra not distinguishable from those of 9-aminnoacnidmc in both the visible and ultraviolet. The interpretation of these results with respect to the stereochemistry of the DNA-ligand complexes is discussed.
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    Density-gradient sedimentation equilibrium of DNA and the effective density gradient of several salts (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1901-1924 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The various treatments of sedimentation equilibrium are compared on a theoretical and an experimental basis. Particular attention is paid to the polyelectrolyte nature of the problem and the choice of a neutral component. The effective density gradients of several cesium salts for DNA are measured. Two previous theories for the effective density gradient are shown to be equivalent, and the experimental values are interpreted with respect to these theories. It is clear t hat sedimentation equilibrium in a density gradient may be used for the determination of unambiguous molecular weights.
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    Theory of friction-limited DNA unwinding (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1949-1972 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The theory of friction-limited DNA unwinding is developed explicitly for moderate tind large perturbations. This extension of the earlier theory of the relaxation kinetics is necessary because of the complex nature of the rate limitation for small perturbations. The assumption of the theory that is violated under relaxation conditions is that base pairing reactions occurring at a constant local degree of twist of the strands are fast compared to the net unwinding of the molecule. However, these reactions that are slow for small perturbations have a large activation energy, and become faster than friction-limited un winding for large enough temperature jumps and sufficiently large DXA molecules. Thus only the rate for moderate and large perturbations is clearly limited by frictional resistance to turning the molecule in solution. The model used is a diffusional unwinding of the two strands, driven by the accompanying decrease in free energy. For large perturbations a numerical solution of the diffusion equation is required, since the diffusion coefficient is not constant. Two new parameters must be introduced into the equilibrium statistical theory to describe friction-limited unwinding kinetics. These are the force constant b, for winding up coil regions and the frictional coefficient per base pair βcfor rotating coil regions in solution. We find by fitting the theory to experiment that b = 1.8 × 10-13 ergs/ rad2- and βc = 3.5 × 10-21 erg see/base pair, both for DNA melted in alkali at 0.4.M Na + and ∼30 °C. The latter value is in agreement with predictions based on the viscosity of single stranded DNA in alkali. The quoted value of bcan be interpreted to mean that the number of conformational states of a nucleolide is reduced by an average factor of 1.55 when it is wound around another strand to the degree of twist in a double helix, but without forming a base pair.
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    Cooperative nonenzymic base recognition II.For an introduction compare paper I of this series Eigen & Pörschke (1970). thermodynamics of the helix-coil transition of oligoadenylic + oligouridylic acids (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1989-2013 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The properties of oligonucleotide helices of adeuylic- and uridylic acid oligomers have been investigated by measurements of hypo-and hyperchromieity. High ionic strengths favor the formation of triple helices. Thus, the double helix-coil transition can be studied (without interference by triple helices) only at low ionic-strength. A “phase diagram” is given representing the Tm-values of the various transitions at different ionic strengths for the system A(pA)17 + U(pU)17. Oligonucleolides of chain lengths 〈8 always form both double and triple helices at the nucleotide concentrations required for base pairing. For this reason the double helix-coil transition without coupling of the triple helix equilibrium can only be measured for chain lengths higher than 7. Melting curves corresponding to this transition have been determined for chain lengths 8, 9, 10, 11, 14 and 18 at different concentrations. An increase in nucleotide concentration leads to an increase in melting temperature. The shorter the chain length the lower the Tm-value and the broader the helix-coil transition. The experimental transition curves have been analysed according to a staggering zipper model with consideration of the stacking of the adeuylic acid single strands and the electrostatic repulsion of tlip phosphate charges on opposite strands. The temperature dependence of the nucleation parameter has been accounted for by a slacking factor x. The stacking factor expresses the magnitude of the stacking enthalpy. By curve fitting xwas computed to be 0.7, corresponding to a stacking enthalpy of about S kcal/mole. The model described allows the reproduction of the experimental transition curves with relatively high accuracy. In an appendix the thermodynamic parameters of the stacking equilibrium of poly A and of the helix-coil equilibria of poly A + poly U at neutral pH are calculated (ΔHA = -7.9 kcal/mole for the poly A stacking and ΔH12 = -10.9 kcal/mole for the formation of the double helix from the randomly coiled single strands). A formula for the configurational entropy of polymers derived by Flory on the basis of a liquid lattice model is adapted to calculate the stacking entropies of adenylic oligomers.
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    Theory of interaction of polymer and small molecules which can aggregate in solution (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2049-2049 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.360101020
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    Concentration dependence in three-component systems in sedimentation equilibrium in buoyant density gradients (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2071-2077 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The data on the band widths and band shapes of several DNA's at various concentrations in sedimentation equilibrium in a CsCl density gradient have recently become available. In the present report, these literature data are treated in the following manner: (1) based on a theory of isotope-substitution, calculations are made of the molecular weights at infinite dilution, and (2) to explain the concentration dependence of band widths and band shapes, a theory of charge and hydration is put forth, and it is shown that by retaining the terms involving the charge of the macromolecules, it is possible to account for most of the concentration dependence.
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    Specificity in the genetic code: the role of nucleotide base-amino acid interaction (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2083-2094 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism of the unique and specific association of a given amino acid to its t-RNA is investigated by theoretical methods. Several possible schemes are proposed to explain specificity. The physical forces which act within these mechanisms are illustrated by the computer simulation of probable interactions between glycine and nucleotide bases and base pairs. It is demonstrated that glycine has direct and selective affinities for the nucleotide bases and that these interactions are principally determined by the polar groups. Energies have been calculated for the interaction of glycine with several base pairs. From these, the possibility that specificity arises through direct complexing of an amino acid with its anticodon is evaluated.
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    Statistical thermodynamics of nucleic acid melting transitions with coupled binding equilibria (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2147-2160 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Equations are developed to describe the shift in the temperature of the helix-coil transition when small molecules bind to nucleic acids. Included are high polymers, oligonucleotides, and oligomer-polymer interactions. The equations prescribe simple ways of plotting experimental data to evaluate transition and binding parameters.
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    Thermodynamic parameters of helix-coil transition in polypeptide chains. II. Poly-L-lysine (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2181-2197 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The helix-coil transitions for poly-L-lysine (PL) were investigated by the methods of spectropolarimetry, viscometry and potentiometric titration in 0.2M NaCl at different temperatures as well as in 0.2MNaBr, 1MKCl, and in mixtures of 0.2MNaCl or NaBr with methanol at room temperature. The enthalpy and entropy differences between the helical and coillike states of uncharged PL molecules in 0.2.M NaCl were determined from the potentiometric titration curves. The cooperativity parameters σ for PL in different solvents were determined by two methods (from the sharpness of the transition and from the dependence of the intrinsic viscosity on the helical content in the transition region). In 0.2MNaCl σ has a value of (2.3 ± 0.5) × 10-4 and does not depend on temperature, i.e., the cooperativity of the helix-coil transition, as for PGA, is mainly of an entropy origin (the initiating of the helical region is accompanied by the entropy decrease ΔSi = -12 eu/mole of helical regions). A comparison of the obtained results for PGA and PL with the molecular theories of the helix-coil transitions shows that the role of dipole-dipole interactions of nonneighboring peptide groups is greatly overestimated in these theories, leading to a considerable enthalpy contribution to the free energy of initiating helical regions which is not observed in the experiment.
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    Polarization of fluorescence of an oriented solution of rodlike particles bearing a fluorescent label (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2029-2037 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The variation of the polarized components of fluorescence of a rodlike particle bearing a fluorescent label upon partial orientation is calculated for some special geometry of the dye macromolecules complexes. Explicit expressions are given for the case where the energy of the molecule in the field depends only on one angle θ, showing that the result is a function of both 〈sin2θ〉 and 〈sin4θ〉. For the case of orientation in an electric field through an anisotropic induced moment, the expressions allow the calculation of this anisotropy of polarizability. The method is applied to the measurement of the polarizability of rodlike fragments of DNA labeled by intercalated molecules of Acridine Orange.
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    URL: http://dx.doi.org/10.1002/bip.360101018
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    Molecular motion in poly(β-benzyl-L-aspartate) (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2039-2048 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As the temperature of solid poly(β-benzyl-L-aspartate) (PBLA), (CO.NH.CH.-CH2COOCH2C6H5)n, in the α-helieal form is raised from -150 °C, tlie line width and second moment of the proton magnetic resonance (PMR) signal decrease in stages until the conformational transition to the ω-helix occurs at about 90 °C. A similar temperature dependence of the PMR parameters is observed as the transformed polymer is cooled. Below -100°C (where the lattice is presumed to be rigid), the measured second moments are 9.5 Oe2 and 10.7 Oe2 for the α and ω forms, respectively. Second moments, calculated from the Van Vleck formula for the rigid lattice and also estimated for possible motional cases in which the polymer is taken to be in the ω form, are compared with the PMH data. By combination with the results of X-ray diffraction and infrared spectroscopic measurements, a tentative explanation can be made of the types of motion occurring in PBLA.
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    Potentiometric titration of poly-L-lysine: the coil-to-β transition (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2133-2145 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have performed potentiometric titrations of poly-L-lysine. From these data we have calculated the free energy and enthalpy changes for the folding of the random coil to the α-helix in 10% ethanol (-120 and -120 cal/mole) and from the random coil to the β-structure in water (-140 and 870 cal/mole) and in 10% ethanol (-180 and 980 cal mole). Comparison of these values with each other and with values for the coil → α- helix transition in water (-78 and -880 cal/mole) led to the following conclusions. The stabilization by ethanol of ethanol of the α-helix with respect to the coil is that predicted from the known free energy of transfer of the peptide group from water to 10% ethanol. Similar data to explain the enthalpy difference are not available. The thermodynamic functions for the transition from α-helix to β-structure, obtained by subtracting those for the coil → α-helix and coil → β-structure transitions, are explained from a consideration of the structural differences: non bonded interactions of the polypeptide backbone are less favorable in the β-structure than in the α-helix, causing an increase in the energy, while hydrophobic contacts between side chains raise the entropy of the β-structure as compared with the α-helix, so that the free energy difference between the two structures is small, but enthalpy and entropy differences are large. The observation of only small differences in the free energy and enthalpy changes for the transition from coil β-structure upon going from water to 10% ethanol is expected by considering both the free energy of transfer of the peptide group (as for the α-helix) and the free energy and enthalpy of transfer of the apolar part of the side chain involved in hydrophobic bond formation.
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    Temperature dependence of the aminoacylation of tRNA by bacillus stearothermophilus aminoacyl-tRNA synthetases (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2209-2221 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Valine specific transfer RNA (tRNAVal) was isolated from Bacillus stearothermophilus and Escherichia coli by chromatography on benzoylated DEAE-cellulose (BD-cellulose). Likewise isoleucine specific transfer RNA (tRNAIle) was isolated from B. stearothermophilus and from Mycoplasma sp. Kid. The thermal denaturation profiles (melting curves) of the two tRNAVal species in the presence of Mg+ + were nearly identical. However, the Tm for the Kid tRNAIle was about 10°C lower than that for the B. stearothermophilus tRNAIle. A nuclease and tRNA-free aminoacyl-tRNA synthetase (AA-tRNA synthetase) preparation from B. stearothermophilus was able to function efficiently at temperatures up to 80°C in the aminoacylation of all four tRNA species. Determination of the amino acid-acceptor activity of each tRNA species as a function of temperature of the aminoacylation reaction showed in each case a strong correlation between the loss of acceptor activity and the thermal denaturation profile of the tRNA. Evidence is presented that the loss in acceptor activity is most likely due to a change in structure of the tRNA as opposed to denaturation of the enzyme. These results further support the idea that correct secondary and/or tertiary structure must be maintained for tRNA to be active as a substrate for the AA-tRNA synthetase.
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    β-Carbonylamides in peptide chemistry. I. Optical rotatory properties of N-acetoacetyl amino acids (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2275-2281 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Cotton effects of N-acetoacetyl amino acids and derivatives were examined by a circular dichroism technique. A correlation has been established between the sign of the Cotton effect and the absolute configuration of the asymmetric center. The L derivatives show, in dioxane, negative circular dichroism curves, whereas the D antipodes present positive curves. The effect of solvent and pH and influence of alkylation at the amide nitrogen are also discussed.
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    Eleclrooptical study of the electric polarizability of rodlike fragments of DNA (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2345-2358 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The anisotropy of electrical polarizability of rodlike fragments of DNA has been studied by a number of electro-optical methods: Kerr effect (combined with flow birefringence), light scattering, diehroism, and fluorescence in an electric field. The most sensitive technique (Kerr effect) has been used to study the variation of the polarizability with the nature and concentration of counteroins. DNA fragments constitute a truly rigid polyelectrolyte of known structure. The value obtained can then be quantitatively compared to the predictions of those of the theories of the longitudinal polarizability of rigid polyelectrolytes which are based on true molecular parameters. The comparison emphasizes the role of the counterion-counterion repulsion. Oosawa's theory seems to represent the best approach but fails to explain the differences observed between monovalent and divalent ions.
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    Masthead (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.360101201
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    Ionic polysaccharides. IV. Free-rotation dimensions for disaccharide polymers. Comparison with experiment for hyaluronic acid (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 811-824 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The root-mean-square end-to-end distance has been calculated for a model allowing free rotation about glycoside bonds for the general case of polysaccharides having a disaccharide repeating unit. Numerical estimates are given for several naturally occurring structures based on an idealized pyranose unit in the C1 chair conformation. Extrapolation procedures which make use of the intrinsic viscosity [η] in good solvents to obtain unperturbed dimensions do not represent, data for hyaluronic acid very well, especially at low molecular weights. However, order-of-magnitude estimates suggest that this polymer behaves similarly to other polysaccharides, and probably has stiffer local structure than typical non-ionic synthetic polymers. A double logarithmic plot of the product of [η] and M̄w, the weight-average molecular weight, against the degree of polymerization in the range for M̄w of 104 to 2 × 104 permits a straight-line fit of available data for all the glycosaminoglycans, including heparin and the chondroitin sulfates, as well as sodium carboxymethyl cellulose. This result suggests similarity of short-chain hydrodynamic behavior of these polymers.
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    The 4th Jerusalem symposium (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 875-875 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1970.360090711
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    Masthead (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Diffusional boundary spreading in the ultracentrifuge (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 865-874 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A common approximation for deriving solutions to the Lamm equation is to neglect diffusion. This paper presents a singular perturbation technique that allows one to estimate the band spreading due to nonzero diffusion coefficient. We illustrate the general mathematical technique by its application to sedimentation when pressure effects are important. Comparison of the approximate solution with accurate numerical solutions shows that the relative errors are of the order of 1% both for concentration and concentration gradient for parameters of chemical interest.
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    Role of pH in charging of glycogen (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 891-896 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Glycogen acquires a negative charge in both alkaline and acidic solutions and can move in an electrical field, its mobility being related to the degree of alkalinity or acidity. There is a slight increase in relative viscosity at both ends of the pH spectrum. These effects and the changes in nuclear magnetic resonance as a function of pH are interpreted.
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    Studies on the viscosity of solutions of bovine liver glutamate dehydrogenase and on related hydrodynamic models; effect of toluene on enzyme association (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 877-889 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The viscosity of bovine liver glutamate dehydrogenase solutions was studied at 10 and 20° C in 0.2.M sodium phosphate buffer at pH 7, in the concentration range 0.1-8 mg/ml. A method for the study of the viscosity of very dilute solutions of associating enzymes is described. It was found that the reduced specific viscosity ηsp/c of glutamate dehydrogenase continuously increases with increasing enzyme concentration, from about 4 ml/g at the lowest concentrations to about 16 ml/g at 8 mg/ml. In the presence of 10-3M GTP and 10-3M NADH the viscosity increase is much smaller and the results can be extrapolated to zero enzyme concentration to yield an intrinsic viscosity [η] = 3.2. The values of ηsp/c in phosphate buffer alone apparently extrapolate to the same value of [η], or to a value close to it. We also observe that, in the presence of toluene ηsp/c increases very much more with enzyme concentration: ηsp/c already equals 16 ml/g at a concentration of 0.75 mg/ml. These observations are in good agreement with the hypothesis that the active oligomer of glutamate dehydrogenase (MW = 312,000) associates with increasing enzyme concentration to form linear rodlike polymers of indefinite length. This association is strongly diminished by the addition of 10-3M GTP, 10-3M NADH. Toluene, on the other hand, promotes reversible association to linear polymers of very high molecular weight. The transverse and axial rotary frictional coefficients of macroscopic bodies, similar to a physical model for the structure of glutamate dehydrogenase recently advanced, were determined. Assuming that the viscosity of the model is equal to that of an ellipsoid of rotation with identical frictional coefficients, we calculate [η] = 3.26 ml/g according to Kuhn and 3.20 ml/g according to Simha, for the glutamate dehydrogenase oligomer, in good agreement with the result derived from the study of enzyme solutions.
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    Surface chemistry of poly(β-beiizyl L-aspartate) (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 911-922 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular monolaycrs of poly(β-benzyl L-aspartate) spread at. an air-water interface have been studied. The results obtained both by direct observations on the monlayer and from examination of collapsed films with polarized infrared spectroscopy and electron diffraction are consistent with the presence of right handed α-helices in the mono-layer when the molecular weight is high. When 1% (v/v) isopropanol is present in the subphase the right-handed helix prevails, provided that the monolayer is first spread on water. Monolayers of low molecular weight polymer appear to form the crossed-β structure. Orientated collapsed films of high molecular weight polymer can be converted to the left-handed α-helical and to the ω-conformation, and the mechanisms are discussed. The surface chemistry of this polymer is compared with that of related polymers and a consistent pattern of behavior emerges.
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    Magnetic circular dichroism study on synthetic polynucleotides, bacteriophage structure, and DNA's (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2537-2553 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The MCD (magnetic circular dichroism) spectra of Ap, ApA, ApApA, poly A, Up, UpU, poly U and double-stranded poly A:U alternating copoly A-U and alternating deoxyribopoly A-T were measured with a Cary 61 spectropolarimeter fitted with a Varian superconducting magnet at a field strength of 50 Kgauss. The MCD spectra of T2 and T5 DNA at various stages of heal denaturation were measured as a function of hyperchromicity of the sample. MCD spectra of the intact and degraded T2 and T5 phages were used to study the degree of alteration of the DNA inside the phages versus the DNA in vitro. The results for the adenine polymers show that the main MCD bands, B2u(271 nm), B1u(252 nm), and E1u(212 nm), show a decrease in specific magnitude as the length of the polymer is increased, reflecting the degree of stacking of the polymer. In contrast, the uridine series of polymers shows little change of the MCD bands, indicating that there is little interaction between the bases regardless of the length of the polymers. The MCD spectra of poly A:U, alternating poly r(A-U): (A-U), and alternating poly d(A-T):(A-T) show significant differences among themselves in the magnitude of the B2u band and when compared with the sum of the spectrum for the poly A plus poly U. This may indicate the selective effect of hydrogen bonding on the B2u band. Alternatively, the difference may be due to the absence of an n → π* transition in the double-stranded polymer. Measurements of denatured T2 and To DNA's show increases in all MCD bands. The T2 DNA internally packed in phage shows an increase of the B2u and E1ubands, the B2u remaining unchanged. The internal T5 DNA shows an increase of the B1u band only. Thus, the internal DNA structure is altered in a manner quite different from a simple denaturation caused by hydrogen bond breaking. Furthermore, different MCD bands indicate that different modes of DNA packing exist for T2 and T5 phages.
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    An infrared study on the conformation of poly-L-proline in concentrated aqueous salt solutions (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2591-2596 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The infrared absorption of poly-L-proline in concentrated aqueous salt solutions was measured in the fundamental region. Of primary interest were the carbonyl absorption of the peptide linkage and the methylene C-H bending absorption of the pyrrolidine ring. These spectral regions each show an additional component in the concentrated salt solutions. Using the position of the absorptions of poly-L-proline I (cis) and II (trans) as models, we conclude that both cis-trans linkages are present in the peptide in salt solutions. Increasing the temperature shifts the equilibrium slightly in favor of cis.
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    Persistence length of DNA from hydrodynamic measurements (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2619-2621 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Ultrasonic studies in relation to the helix-coil transition in aqueous solutions of poly-L-lysine (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2635-2638 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360101226
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    A statistical mechanical theory of unfolding of globular proteins induced by preferential binding of solvent components in water-organic solvents systems (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 2649-2649 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.360101230
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    Spatial configurations of polynucleotide chains. I. Steric interactions in polyribonucleotides: A virtual bond modelFrom the thesis submitted by Wilma K. Olson in fulfillment of the requirements for the degree of Doctor of Philosophy, Stanford University, 1971. (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 1-23 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: A simplified scheme for treating the spatial configurations of polynucleotide chains is developed using the rotational isomeric state approximation and statistical methods applicable to linear systems of interacting subunits. As a consequence of geometric constraints imposed by the skeletal structure and of the severity of certain steric interactions, it is possible to represent the repeat unit comprising six skeletal bonds by two virtual bonds of fixed length. The configuration of the polynucleotide chain as a whole may be conveniently described by an alternating succession of these two virtual bonds. Moreover, analysis of steric interactions suggests that bond rotations governing the mutual orientation of a given pair of successive virtual bonds should be sensibly independent of the rotations affecting the mutual orientation of other pairs. The statistical mechanical treatment of configuration-dependent properties is much simplified in consequence of this mutual independence. Mean-square dimensions calculated by giving equal weights to all sterically allowed conformations are much smaller than values determined by Felsenfeld and co-workers. The calculated dimensions are markedly increased, however, by placing certain arbitrary restrictions on the rotations about selected pairs of skeletal bonds. It is thus demonstrated that steric interactions alone are insufficient to account for the spatial characteristics of polynucleotide chains. The dimensions are also found to be sensitive to the conformation of the ribose ring of each nucleotide unit, but, insofar as the influences of steric interactions are concerned, the dimensions do not depend on the heterocyclic base attached to the ribose ring.
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    Isoenzymes of tetrameric proteins (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 119-126 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A theory is presented concerning the possible arrangements of protomers in tetrameric molecules. Isoenzymes may exist even in the case of homotetramers if the asymmetry of the identical protomers is detectable. The number of tetrahedral isoenzymes that can be isolated depends on the nature of the intersubunit bonds and on the level of the asymmetry of the protomers. Five isoenzymes can be distinguished only if two different types of protomers form tetrahedral tetramers and the asymmetry of protomers is not detectable with the method used. If the two types of protomers can bind each other by any pairs of binding sets and the asymmetry of both protomer types reaches the level of detection with the method used, we obtain 117 isoenzymes: 15 individual ones, and 51 stereoisomeric pairs.
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    Graphical approach to non-ideal cases of self-associating protein systems (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 197-214 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Our previous paper described graphical procedures for evaluating the mode of association in ideal discrete and indefinite cases. This paper concerns the application of such procedures in cases where the non-ideality term BM1 must be considered. Bovine liver L-glutamate dehydrogenase and lysozyme are used as model systems. Several graphical procedures for dealing with cases of 1 - m, 1 - m - n, or indefinite association are developed. The procedure is based on the evaluation of the weight-fraction monomer with-out prior calculation of BM1, using graphical analysis to evaluate the non-ideality term.
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    Fibrillar aggregates of poly-γ-benzyl-L-glutamate (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 271-278 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 6 Ill.
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    Characterization of acid-denatured DNA by low-angle light scattering (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1017-1028 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Low-angle light scattering results reported previously demonstrated that measurements on high molecular weight native DNA must be made at angles below 30° in order to obtain correct molecular weights. Earlier light-scattering data obtained on denaturated DNA at angles above 30° showed no change in molecular weight upon denaturation, even though other techniques clearly showed that strand separation occurred. This paper reports low-angle measurements on solutions of calf thymus and T7 DNA denatured under acidic conditions. The results demonstrate that a halving of molecular weight consistent with strand separation is detected by light scattering only when low-angle data are used to obtain correct molecular weights for native material. As expected from theoretical considerations, the scattering from denatured DNA is a linear function of sin2(θ/2), where θ is the angle of observation. This result shows that anticipated experimental artifacts have no significant effect on the low-angle measurements and demonstrates that the curvature in the scattering envelope observed for native DNA below 30° is an inherent property of the native molecule.
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    Kinetics for the transition between cis- and trans-helices in poly-L-prolineA preliminary report of this work was presented at the 156th National Meeting of the American Chemical Society, Atlantic City, New Jersey, September 1968. (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1001-1016 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics for the cis-trans isomerization of long-chain poly-L-proline has been studied as a function of pressure, temperature, and solvent composition in the acetic acid + n-propanol solvent system. Our complete kinetic curves were fitted by Monte Carlo techniques, and rate constants for nucleation, growth, and termination were estimated. It was found that for the formation of a cis-helix, high pressure, low temperature, and increased acetic acid content of the solvent, lowered the rate of nucleation relative to growth. The inverse seems to be t rue for the formation of a trans-helix. Molecular models suggest that this behavior of the kinetic constants can be due to the exposure of peptide units to solvent in the transition state for trans nucleation, and the burying of peptide units in the transition state for cis nucleation. It is further suggested from our analysis of complete kinetic curves that at least one of the assumptions usually made in the analysis of relaxation kinetics is invalid for poly-L-proline.
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    X-Ray diffraction of ethylenediamine-amylose complex (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1039-1047 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solutions of amylose in ethylenediamine yield a crystalline film complex upon evaporation of solvent. The x-ray analysis indicates the presence of a tetragonal-shaped cell with a symmetry approximating that of space group P212121. The amylose sixfold helix has a diameter of 13.3 Å and a translation period of 8.0Å. Chemical and physical analyses support a complexing ratio of one ethylenediamine molecule to every two glucose units. The structure is nearly identical to any amylose-dimethyl sulfoxide complex previously examined. The square mode of packing arrangement appears to result from complexation between amylose chains. Such complexing indicates a much greater degree of amylose interaction than is observed in amylose complex structures having a hexagonal close-packing arrangement.
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    Potentiometric titration of poly-S-carboxymethyl-L-cysteine in aqueous NaCl solution (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1049-1058 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: pH titration measurements of poly- S-carboxymethyl-L-cysteine were undertaken in the aqueous Nacl solution in relation to the β form-random coil transition. The titration curves show a marked molecular weight dependence because of the shortened chain length of materials. Comparison of the optical rotatory dispersion parameter a0 with the titration curve reveals that the titration curve apparently reflects a β structure-random coil transition. The β form of this polymer is assumed to be an intramolecular β form, rather than a β structure stabilized by an intermolecular hydrogen bond, at least in the polymer concentration range considered here. The standard free energy change per amino acid residue for the transition from un-ionized random coil to un-ionized β form is estimated to be about -750 cal/mole residue in the range of 0.005-0.2M NaCl concentration.
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    Oligonucleotide interactions. III. Circular dichroism studies of the conformation of deoxyoligonucleolides (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1059-1077 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dichroism (CD) spectra of the four usual deoxymononucleosides, all sixteen deoxydinucleotides, and a number of trinucleotides have been measured. The dimer spectra are quite different from the sum of the spectra of their constituent monomers. This indicates the presence of base-stacked conformations analogous to those found for ribonucleoside diphosphates. The CD spectra of several deoxytrinucleotide diphosphates and single-strand f 1 DNA can be calculated fairly well by using a semi-empirical nearest-neighbor approach. There is little or no effect of terminal phosphate or of salt concentration on the optical properties of most deoxy oligomers. The possibility of simultaneous analysis of mixtures of deoxypurine or deoxypyrimidine sequence isomers has been examined. This seems to be a viable approach for the analysis of purine runs but cannot promise much success for pyrimidine runs.
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    Oligonucleotide interactions. IV. Conformational differences between deoxy- and ribodinucleoside phosphates (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1079-1103 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dichroism spectra of all 16 ribodinudeoside phosphates containing the bases adenine, uracil, cytosine, and guanine have been measured at room temperature and neutral pH. These results are compared with the circular dichroism spectra of the corresponding deoxy compounds. From the optical properties it is clear that the geometry of the base-stacked conformation of ribo compounds must differ substantially from that of deoxy compounds. Because of this, it is not possible to draw firm conclusions about the relative extent of stacking in most ribo and deoxy compounds. The optical rotatory dispersion of about a dozen deoxy and ribodinucleoside phosphates has been studied as a function of temperature. These results confirmed the conclusions drawn earlier from measurements at a single temperature. Several dinucleoside phosphates containing a 2′ → 5′ phosphodiester bond have also been examined. These compounds have a substantial degree of base stacking at room temperature. The geometry of the stacked conformation is different from that of either the normal ribo dimer or the deoxy dimer. The role of the 2′-hydroxyl group in stabilizing base stacked geometries has been examined by studies on C-2′-O-methyl-pC. This compound has optical properties almost identical to those of CpC. This suggests that the effect of the 2′ hydroxyl is felt indirectly through its perturbation of the geometry of the sugar ring rather than directly by hydrogen bonding. It is not possible at present to identify precise conformational differences among deoxy-, ribo-and 2′ → 5′ ribodinucleoside phosphates.
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    Aggregation of poly-L-proline II (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1119-1124 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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    Lysine oligopeptides. Preparation by ion-exchange chromatographyOn leave from the Department of Biophysics, The Weizmann Institute of Science, Rehovot, Israel. (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 607-621 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of L-lysine peptides (Lysn, n = 2-14) from polyL-lysine is described. Fractionation by ion-exchange column chromatography of poly-L-lysine hydrolysates on a preparative scale resulted in 0.2-1.0 g quantities of individual members of the poly-L-lysine series. The peptides isolated proved to be analytically pure and the optical configuration was fully retained, as demonstrated by complete enzymic digestion. Peptides higher than n = 14 were also prepared. They consisted of oligolysine groups of narrow and accurately determined size distribution. Potentiometric titrations were used both to characterize the products and to demonstrate the characteristic dependence of the dissociation constants on size of the peptide.
    Additional Material: 11 Ill.
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    Independence of length and temperature effects on the rate of helix formation between complementary ribopolymers (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 549-561 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate of double helix formation by single stranded Poly A plus Poly U, Poly I plus Poly C, Poly G plus Poly C, and T2 DNA has been investigated as a function of both the length of the reacting strands and temperature. The length dependence of the rate is found to be independent of temperature. All of the reactions studied show a rate approximately proportional to the square root of the length of the shorter of the complementary strands. At or about 30°C below the melting temperature the ribopolymers react with about the same rate. This rate is four to five times slower than DNA renaturation rates. The effect of temperature on ribopolymer reaction rates is interpreted in terms of a steady-state model for helix propagation.
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    Evidence for stereospecific collision complexes of cyclo(tri-L-prolyl) with benzene (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 653-659 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: NMR spectra of cyclo(tri-L-prolyl), c-(P)3, show large shifts of the Hα resonance on adding C6D6 to a solution of c-(P)3 in CD2Cl2. CPK models and observed coupling constants indicate a rigid c-(P)3 conformation, independent of solvent composition, suggesting that these shifts result from formation of stereospecific C6D6-c-(P)3 collision complexes in which the c-(P)3 Hα lie near the face of the aromatic ring. The temperature dependence of the Hα shifts and the solvent dependent shifts observed on adding toluene-d8 or nitrobenzene-d5 to the c-(P)3 solution suggest that preferred C6D6-c-(P)3 orientations result from attractive interactions between the electron-rich aromatic ring and the electropositive Hα's and/or δ+ nitrogen atoms in the peptide backbone. Reports of such interactions in increasingly diverse peptide model systems suggest that they may play a role in stabilizing protein structures.
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    Thermal denaturation of nucleohistones - effects of formaldehyde reaction (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 835-847 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal denaturation of native or partially dehistonized nucleohistones shows two melting bands at 66 and 81° in 2.5 × 10-4 M EDTA, pH 8.0. These correspond to the melting of DNA segments bound by the less basic and the more basic half-molecules of histones, respectively. These two melting bands combine into a broad melting band from around 70 to 85° when these nucleohistones are pre-treated with formaldehyde. A formaldehyde reaction which fixes histones on DNA by covalent bonds account for the effect. Formaldehyde fixation also increases the melting temperature of some free DNA segments from around 42 to around 55°. This is interpreted as a result of closed or rigid boundaries between free DNA and formaldehyde-reacted histone-bound DNA segments. MgCl2 dissociates histones from DNA more effectively and leaves longer free DNA segments than does NaCl. Thermal denaturation of a formaldehyde-reacted nucleoprotein thus provides an effective tool for comparing the relative size of free DNA regions on nucleoproteins. The effect of reversible binding of ligands on helix-coil transition of DNA is descussed and found not adequate for thermal denaturation of nucleohistones.
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    Linear relaxation analysis of the mechanochemical transformation of collagen fibers (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 899-912 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The isometric tensile stress generation observed when collagen fibers are immersed in aqueous solutions of lithium bromide ranging in molar concentration up to 7 was studied at 23°C. The reverse process, namely, isometric stress relaxation of the fiber occurring by subsequent immersion in distilled water, was also studied. We find that the data in the region of LiBr concentration up to about 2.5 moles/liter are adequately represented by a superposition integral \documentclass{article}\pagestyle{empty}\begin{document}$$ \sigma (t) = \int_{ - \infty }^\infty {K(t - \tau )} \frac{{dc(\tau )}}{{d\tau }}\,d\tau $$\end{document} where σ(t) is the time-dependent stress generated by the collagen fiber held at fixed length, c(t) is the history of LiBr molar concentration, and K(t) is the isometric contractility function, expressed as stress per unit salt concentration. We conclude that, within a limited range of salt concentration, a collagen fiber in a LiBr bath behaves as if it were a linear, time-invariant system defined mechanochemically by a single function K(t) which depends on the structural characteristics of the fiber while being independent of salt concentration. An analysis is presented of isometric mechanochemical data obtained under conditions of equilibrium by other workers who studied the behavior of collagen fibers in aqueous solutions either of urea, LiBr, or KCNS. The analysis shows that these independent (equilibrium) data confirm the linarity of the relation between isometric contractile stress and salt concentration on which our superposition integral representation is based. We also find that the asymptotic (infinite-time) value of the isometric stress is linearly related to the chemical potential of the salt as well, in agreement with the equilibrium thermodynamic treatment of mechanochemical processes by Katchalsky and Oplatka.
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    Thermodynamic analysis of thermal transitions in globular proteins. I. Calorimetric study of ribotrypsinogen, ribonuclease, and myoglobin (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 935-935 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1972.360110415
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    On the application of polyelectrolyte “limiting laws” to the helix-coil transition of DNA. I. Excess univalent cations (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 937-949 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general theory of polyelectrolyte solutions is here used to calculate the differences in Gibbs free energy, enthalpy, and entropy between the coil and helix forms of DNA at any temperature and salt concentration. The salt has univalent cations and is assumed present in excess over the base concentration. The results are restricted to sufficiently dilute solutions. It is shown that the salt concentrations effect is entirely entropic in origin. When applied to the melting temperature, the calculations yield a relation between the enthalpy difference at the melting temperature and the slope of the plot of melting temperature vs. the logarithm of the salt concentration. In accord with observation, both the Gibbs free energy difference at any fixed temperature and the melting temperature are predicted to be linear functions of the log of the salt concentration.However, the theory is not in quantitative agreement with enthalpy data. Data on various colligative and transport properties of both helix and coil forms are reviewed in the text and in Appendix B, and good agreement is found with theory for both forms. No attempt is made to explain why the theory is quantitative for these properties but not for heat measurements.Finally, in Appendix A, an approximate calculation is made of the free energy contributions due to ionic effects not associated with the salt concentration.
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    The conformation fo poly-L-alanine in hexafluoroisopropanol (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 1001-1020 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-molecular-weight poly-L-alanine dissolved in hexafluoroisopropanol exhibits infrared, ultraviolet, circular dichroism, and optical rotatory dispersion spectra which are unique and unlike any other previously reported polypeptide spectra. Strong evidence that a helical conformation is present is shown by the high degree of hypochromism in the 187mμ absorption peak and by the positions of the amide infrared bands. The CD and ORD spectra are also similar to those of α-helical polypeptides, though important qualitative and qualitative differences are observed. To explain the novel spectra, which are not mixtures of the spectra of previously reported polypeptide conformations, a new α-helix-like conformation is proposed. The postulated conformation (a doubly hydrogen-bonded helix) is a distorted α-helix in which the peptide carbonyl groups point slightly out from the helix axis and are hydrogen bonded simul taneously both to the NH of the fourth peptide residue to the carboxyl terminal side (as in the classical α-helix), as well as to a solvent molecule's hydroxyl hydrogen.
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    PPP calculations of the circular dichroism spectra of some dinucleoside phosphates (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 1091-1102 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Circular dichriosm (CD) spectra have been calculated for serveral dinucleoside phosphates using a variant of the Pariser-Parr-Pople π-electron molecular orbital method. This method does not require the prior knowledge of the experimental absorption spectra of transition moments of the bases forming the dinucleoside phosphates. Calculated spectra were obtained in good agreement with experimental spectra for four dinucleoside phosphates, ApA, UpU, GpA, and UpA, and reasonable agreement was obtained for ApG and ApU. The effect of changing conformation on the CD spectrum was studied for ApA, UpU, UpA, and ApU; the spectra of UpU, UpA, and ApU were sensitive to small change in conformation, whereas ApA was insensitive over the range of conformation studied. Further studies await detailed knowledge of the structure of dinucleoside phosphates in solution.
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    The influence of single-strand breaks on the kinetics of denaturation of DNA (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1349-1360 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of single-strand breaks on the kinetics of the relaxation of DNA in a solution of low ionic strength has been investigated by a temperature jump method. The relaxation of DNA after a jump of 0.7 °C in the melting region has been monitored by measuring the extinction at 260 nm. For essentially monodisperse T4 DNA (M = 130 × 106) two distinct relaxation times have been observed, that depend markedly on the initial extent of denaturation 1 - θ. The larger relaxation time decreases from 450 sec to about 300 sec, the smaller one from 55 see to 30 when 1 - θ increases from 0.03 to about 0.8. The dependence of these relaxation times on the average number of single-strand breaks per molecule (p) appears to be very small up to p = 100. However, the relative contribution of the slow process decreases sharply when p increases from 0.6 to 30 and remains nearly constant for larger p. The observations are discussed in the light recent theories of the kinetics of denaturation.
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    Electro-optic scattering studies on deoxyribonucleic acid (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1361-1372 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurements have been made of the intensity of light scattered from aqueous solutions of calf thymus DNA with and without the application of electric fields. For fields approaching 150 V/cm and frequencies below 2.5 KHz, changes (ΔI) of up to 10% in the residual scattered intensity were observed. In agreement with previous dielectric and electric birefringence measurements, a low frequency dispersion of ΔI was observed, from which a rotary diffusion constant (D) of 1200 s-1 was determined. Interpreting the electric field data in terms of the classical dipolar orientation theory led to values of 2.4 × 10-25 cm (7.4 × 10-14 esu) and 4.3 × 10-25 cm (13 × 10-14 esu) for the permanent dipole moment and the anisotropy of the electric polarisabilities respectively. Furthermore the permanent dipole moment was along the major molecular axis and the particles orientated in the field as rigid entities. The zero field data indicated a molecular shape which was not rodlike but corresponded to the Kratky-Porod “stiffness” parameter of x = 24 for the wormlike coil model. Although curved, the molecules appeared to orientate in low-intensity electric fields as rigid, but not rodlike molecules. The implications of this on recent discrepancies in D determined by two or more dynamic relaxation methods is briefly discussed.
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    Buoyant density and solvation of magnesium DNA (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1391-1402 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The buoyant density of T-4 DNA was determined by equilibrium sedimentation in a density gradient, of mixed solutions of cesium and magnesium chlorides and bromides. The preferential hydration was calculated from these data, allowing appropriately for the exchange equilibrium of DNA with Cs+ and Mg++ ions. The charge and intrinsic solvation of the counterions were found to have no appreciable effect on the hydration of the DNA, the extent of solvation depending only on the thermodynamic, activity of the water. Various reasonable hypotheses are discussed to account for these results.
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