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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of otolith chemistry in Nassau grouper (Epinephelus striatus) from the Bahamas and Belize using solution-based ICP-MS (1999)
    Springer
    Coral reefs 18 (1999), S. 171-178 
    Details
    ISSN: 1432-0975
    Keywords: Key words Otolith ; Chemistry ; ICP-MS ; Stock discrimination ; Epinephelus striatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract  We examined the utility of otolith minor and trace element chemistry, assayed with inductively coupled plasma mass spectrometry (ICP-MS), as a means of delineating population structure in the Nassau grouper (Epinephelus striatus). We characterized the elemental composition of otoliths collected in 1993 from three locations in Exuma Sound, Bahamas and from Glover Reef, Belize in 1995. A single location in Exuma Sound was sampled in 1994 to test temporal variability in otolith composition. Five elements (Ca, Zn, Sr, Ba and Pb) were routinely detected, at levels significantly above background, by solution-based ICP-MS. Results from analysis of variance of elemental data, expressed as a ratio to Ca, indicated that there were no significant differences among the Exuma locations for any element, but significant variability was found between Glover Reef and the pooled Exuma localities for Zn/Ca, Sr/Ca and Ba/Ca ratios. Significant inter-annual differences at one Exuma Sound location was restricted to Ba/Ca ratios. Discriminant function analysis correctly classified 86% and 95% of the Belize and pooled Exuma sites, respectively. Otoliths from Belize were characterized by low Zn/Ca and high Ba/Ca and Pb/Ca ratios compared to otoliths from fish collected in Exuma Sound. Although differences in Ba levels may be related to upwelling at Glover Reef, more data are needed to definitely link otolith composition with regional differences in water chemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003380050176
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  • 2
    Electronic Resource
    Electronic Resource
    Application of matrix rank analysis to the optical rotatory dispersion of TMV RNA (1967)
    New York : Wiley-Blackwell
    Biopolymers 5 (1967), S. 589-613 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The method of matrix rank analysis has been applied to a large body of experimental data to determine and identify the minimum number of independent spectral components that, were contained within it. The optical rotatory dispersion of TMV RNA was measured in the wavelength region 230-350 mμ, for a wide range of temperatures and ionic strengths. Over the whole range of conditions considered, the observed optical rotatory dispersion spectra were found to be a superposition of two basic spectra only. Evidence is put forward relating these spectra to the single-strand and double-strand helical forms of the molecule. A model is proposed to explain the observed spectral changes in terms of an equilibrium between these two conformations, which leads to a direct calculation of the percentage composition of the double strand at any of the conditions considered. This equilibrium, while simple in general description, appears multi-state and complex in detail. This method of analysis is both powerful and of wide applicability, since it is independent of the source of the data.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1967.360050702
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  • 3
    Electronic Resource
    Electronic Resource
    Conformational analysis of the milk oligosaccharides (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1555-1566 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Possible conformations of lacto-N-tetraose, lacto-N-neotetraose, related disaccharides, and other milk oligosaccharides have been studied by an energy-minimization procedure using empirical potential functions. Lacto-N-tetraose favors a “curved” conformation, while lacto-N-neotetraose favors an approximately “straight” conformation. These two conformations differ mainly in the position of the terminal galactose residue with respect to the rest of the molecule. This difference explains the greater strength of lacto-N-neotetraose compared with lacto-N-tetraose in its ability to inhibit the cross-reaction of blood group P1 fractions with Type XIV pneumococcal antipolysaccharide. Although the favored conformation of lacto-N-tetraose (inactive) agrees with the model proposed by the earlier workers, that for lacto-N-neotetraose (active) differs. The favored conformations for the disaccharides galactose-β(1-4)-N-acetylglucosamine, galactose-β(1-3)-N-acetylglucosamine, and lactose are similar in overall shape, differing only in the nature and orientation of the side groups. This explains their nearly equal inhibitory activity. These theoretical models also explain the increased activity of lacto-N-fucopentaose I over that of lacto-N-tetraose and the relative activities of the substituted lactoses. The present studies suggest that it is the overall shape of the molecule which is important for activity, rather than the terminal β(1-4)-linked galactose residue alone.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190811
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  • 4
    Electronic Resource
    Electronic Resource
    Flexibility of the pyranose ring in α- and β-D-glucosesA part of this paper was presented at the International Symposium on Biomolecular Structure, Function, Conformation and Evolution held at Madras, India, January 4-7, 1978. (1979)
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2993-3004 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energies of α- and β-D-glucopyranoses were computed by varying all the ring bond angles and torsional angles using semiempirical potential functions. Solvent accessibility calculations were also performed to obtain a measure of solvent interaction.The results indicate that the 4C1 (D) chair is the most favored conformation, both by potential energy and solvent accessibility criteria. The 4C1 (D) chair conformation is also found to be somewhat flexible, being able to accommodate variations up to 10° in the ring torsional angles without appreciable change in energy. Observed solid-state conformations of these sugars and their derivatives lie in the minimum-energy region, suggesting that the substituents and crystal field forces play a minor role in influencing the pyranose ring conformation. Theory also predicts the variations in the ring torsional angles, i.e., CCCC 〈 CCCO 〈 CCOC, in agreement with the experimental results. The boat and twist-boat conformations are found to be at least 5 kcal mol-1 higher in energy compared to the 4C1 (D) chair, suggesting that these forms are unlikely to be present in a polysaccharide chain. The 1C4 (D) chair has energy intermediate between that of the 4C1 (D) chair and that of the twist-boat conformation. The calculated energy barrier between 4C1 (D) and 1C4 (D) conformations is high - about 11 kcal mol-1.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1979.360181207
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  • 5
    Electronic Resource
    Electronic Resource
    Oligomeric benzophenones as antioxidants for cellulose triacetate (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 47-52 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Filme aus Cellulosetriacetat wurden mit oligomeren 2-Hydroxy-4-alkoxybenzophenon-Derivaten stabilisiert und thermisch gealtert. Die oxidationshemmende Wirkung der oligomeren Stabilisatoren wurde durch Messung des Gewichtsverlusts, der Änderung von Carbonyl- und Hydroxy-Index sowie der Änderung der Bruchspannung und -dehnung ermittelt. Es wurde festgestellt, daß die Stabilisatorwirkung der oligomeren Benzophenone im allgemeinen besser ist als die der monomeren Vorstufen.
    Notes: Cellulose triacetate films stabilized with oligomeric 2-hydroxybenzophenone derivatives were subjected to oven ageing. The antioxidant efficiency of the oligomeric stabilizers was determined by carrying out measurements of percentage weight loss, change in carbonyl index and hydroxy index, and change in tensile strength and elongation at break. In general, the oligomeric benzophenones show better performance than their monomeric precursors in stabilizing cellulose triacetate.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052260105
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  • 6
    Electronic Resource
    Electronic Resource
    Studies of the conformation of amylose in solutionPaper presented in part before the Division of Carbohydrate Chemistry, 140th Meeting of the American Chemical Society, Chicago, September 1962. This work was supported by a Grant from the Corn Industries Research Foundation. (1963)
    New York : Wiley-Blackwell
    Biopolymers 1 (1963), S. 527-544 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It has been suggested previously that water is a nearly indifferent solvent for amylose on the basis that the exponent a of the Mark-Houwink equation is very nearly 0.50 and the second virial coefficient A2 is extremely small. It is shown that such solutions do not show the expected precipitation on cooling and the temperature coefficient of the intrinsic viscosity is small and negative. It is suggested that water is both an indifferent and a nearly athermal solvent for this polymer. Various lines of evidence suggest the polymer to exist as a very stiff coil in this and in other solvents. Variations in the intrinsic viscosity and radius of gyration in various solvents show the importance of skeletal effects in addition to the usual osmotic effects. Application of the Porod-Kratky wormlike coil model leads to unreasonably short persistence lengths if the contour length is based on a fully extended conformation but large and reasonable values of the order 40-70 A. if it is assumed that the basic conformation is the helical one observed in various amylose complexes in the crystalline state. As was previously known, the specific optical rotation decreases sharply in aqueous solutions above approximately pH 12. Accompanying this change in rotation there is first a decrease, then an increase in intrinsic viscosity. This later behavior is strikingly reminiscent of the known behavior of polyglutamic acid in the pH-dependent transition from helix to coil. It is concluded that the conformation is that of a stiff coil with essentially helical backbone contour in neutral solution, and the decrease in rotation and in intrinsic viscosity at high pH results from a partial breakdown of the helical structure with a concomitant increase in backbone flexibility. The increase in viscosity and radius of gyration in extreme alkaline solution is probably due to a polyelectrolyte expansion of the polymer coil. Some other miscellaneous observations which are in accord with this model are also pointed out.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360010604
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  • 7
    Electronic Resource
    Electronic Resource
    Studies of the conformation of carboxymethyl amylose in aqueous solutionsThis work was supported by a grant from the Corn Industries Research Foundation. (1965)
    New York : Wiley-Blackwell
    Biopolymers 3 (1965), S. 185-193 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In an attempt to clarify certain questions of the configuration of amylose in aqueous solution, carboxymethyl groups were introduced into corn amylose (degree of substitution ca. 0.8) and certain properties of the derivative (CMA) studied. The intrinsic viscosity exhibits a strong increase between pH 2 and 6 but remains constant at higher pH. A pH 6 and above, CMA exhibits typical polyelectrolyte behavior. CMA does not form a complex with iodine at pH 6 or above but does form a violet-colored complex at low pH. The absorption maximum of the CMA complex lies at a somewhat lower wavelength (550 mμ) than that of the complex formed by the parent amylose. The reduced viscosity and specific optical rotation of the CMA-iodine complex remains constant up to a concentration of 1.2 mg. iodine/100 mg. CMA, then both properties decrease with further increases of iodine content. All of the above results and hydrogen ion titration behavior are in agreement with the hypothesis that CMA exists as a coil of short helical segments in acid solution and that these helical segments break down on ionization of the carboxyl groups. The specific optical rotation of CMA increases between pH 2 and 6, remains constant between pH 6 and 12, and decreases above pH 12. This later result shows that the similar decrease in rotation seen in amylose cannot be attributed, at least entirely, to a helix-coil transition. There must be another effect on optical rotation, direct or indirect, of the ionization of hydroxyl groups.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360030206
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  • 8
    Electronic Resource
    Electronic Resource
    Configurational statistics of polysaccharide chains. Part II. CelluloseContribution No. 286 from Centre of advanced study in physics, University of Madras, India. (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 783-790 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The characteristic ratio of unperturbed cellulose chain was computed as a function of the angle τ at, the bridge oxygen atom and the degree of polymerization. Very high values of the order of 40 or more, depending on the angle at the bridge oxygen atom, have been obtained for this ratio, indicating that cellulose chains are highly extended. The average dimensions of cellulose chains are found to be sensitive even for small changes in the angle at the bridge oxygen, and these chains attain the character of a random coil in very high molecular weight range (degree of polymerization greater than 2000). The large differences in the unperturbed dimensions of cellulosic chains observed in different solvents have been attributed to the possible small changes in the angle τ caused by specific solvent, interactions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1970.360090704
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  • 9
    Electronic Resource
    Electronic Resource
    Conformational studies of linear β-D-1,4′-mannan and galactanContribution No. 289 from the Centre of Advanced Study in Physics, University of Madras, Madras, India. (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1239-1247 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nonbonded interaction energy of disaccharides, mannobiose and galactobiose and polysaccharides mannan and galactan have been computed as a function of dihedral angles (φ,ψ). The conformation (40°, -20°) has been preferred for the mannan chain from nonbonded interaction energy considerations. The O5…O3′ type of intramolecular hydrogen bond has been found to be possible in the above conformation. Comparison of the allowed region of mannan with those of cellulose and xylan indicates that the monomer unit, in mannan chain has slightly higher freedom of rotation than that of cellulose and less than that of xylan. As in cellulose and mannan, the freedom of rotation of the monomer units in β-1,4′ galactan is highly restricted. Unlike mannan (which prefers an extended conformation) the β-1,4′ galactan prefers a helical conformation similar to amylose. Just as in amylose the O2…O3′ type hydrogen bond between contiguous residues is also possible in β-1,4′ galactan.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1970.360091004
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  • 10
    Electronic Resource
    Electronic Resource
    Conformational studies of α-glucansContribution No. 345 from the Centre of Advanced Study in Physics, University of Madras, Madras, India. (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 1379-1394 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of the effect of linkage on the possible conformations of di-and polysaccharides of α-D-glucose and also the probable intramolecular hydrogen bonds has been made. The differences in the nature of linkage is shown to effect the energetically preferred conformations; (1 → 2) linkages lead only to righthanded helical conformations, (1 → 3) linkages lead to extended as well as both left and righthanded helical conformations; (1 → 4) linkages lead to both right-and lefthanded wide helical conformations. The possible hydrogen bonds between adjacent residues are also dependent on the nature of the linkage. A comparison of the conformational data of α-D-glucans with those of β-D-glucans has indicated that the favored conformations and hydrogen bonds between contiguous residues in the chain are influenced by the configuration at the anomeric carbon atom in all the three types of polysaccharides. From the energy calculations a probable conformation (φM = -10°, ψM = -30°, φN = -23°, ψN = -19°) has also been proposed for crystalline mycodextran in conformity with x-ray data. This conformation contains two types of hydrogen bonds between contiguous residues one between 0-2 and 0-3 atoms at (1 → 4) linkage and the other between 0-2 and 0-4 atoms at (1 → 3) linkage in the chain. The conformation of maltose unit (-10°,-30°) that is likely to occur in the crystalline mycodextran coincides with the minimum energy conformation of maltose.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360110707
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