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  • 1
    Publication Date: 1978-04-01
    Print ISSN: 0005-2795
    Electronic ISSN: 1879-2952
    Topics: Biology
    Published by Elsevier
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  • 2
  • 3
    Publication Date: 1975-07-01
    Print ISSN: 0005-2795
    Electronic ISSN: 1879-2952
    Topics: Biology
    Published by Elsevier
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  • 4
    Publication Date: 1981-10-01
    Print ISSN: 0005-2760
    Electronic ISSN: 1879-145X
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Published by Elsevier
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 20 (1971), S. 193-202 
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Struktur von Bis(äthylendiamin)nickel(II)-tetracyanopalladat(II), Ni(NH2CH2CH2NH2)2Pd(CN)4, wurde mit Hilfe von Weissenbergaufnahmen ermittelt. Die Substanz kristallisiert mit zwei Formeleinheiten in der monoklinen Raumgruppe P21/n mit den Zelldimensionen a=7,174(10), b=10,740(15), c=10,135(15) Å, β=115,0(5)°. Die gemessene und die berechnete Dichte betragen beide 1,83 g/cm3. Die, Verfeinerung unter Berücksichtigung anisotroper Temperaturfaktoren führte zu einem. R-Wert von 10,2%. Unendlich lange-Pd-C-N-Ni-N-C-Ketten sind parallel derc-Achse angeordnet. In Übereinstimmung mit den Spektren im sichtbaren und infraroten Bereich handelt es sich um einen polynuklearen Komplex, indem die trans-Cyanidgruppen von Pd(CN) 4 2− als ambidente Liganden zu einer oktaedrischen [NiN6]-Koordinationseinheit führen. Die trans-Ni(NH2CH2CH2NH2)2(NC)2-Gruppe weist eine asymmetrische “gauche” (δλ)- Konformation auf. Mittlere Atomabstände betragen: Pd-C=1,96 Å. C≡N=1,15 Å, Ni-N=2,08 Å.
    Abstract: Résumé La structure du tétracyanopalladate (II) de bis (éthylènediamine) nickel (II) a été déterminée à partir de données tri-dimensionnelles aux rayons X, avec des photographies de Weissenberg. Le composé cristallise avec deux molécules dans le groupe spatial monoclinique P21/n avec les param ètres a=7.174 (10), b=10.740 (15), c=10.135 (15) Å, β=115.0 (5)°. La densité mesurée et calculée est 1,83 g/cm3. L'amélioration anisotrope donne un facteurR final de 10,2%. La structure se présente comme des chaînes infinies -Pd-C-N-Ni-N-C, parallèles à l'axec. Deux atomes d'azote trans du groupe carré Pd(CN) 4 2− sont liés à Ni, conduisant ainsi à un composé polycyclique avec un groupe [NiN6] octaédrique, ce qui est en accord avec le spectre visible et infra-rouge. Le groupe trans-Ni (NH2CH2CH2NH2)2(NC)2 a une conformation assymétrique ≪gauche≫ (δλ). Les distances moyennes sont Pd-C: 1,96 Å, C≡N:1,15 Å, Ni-N: 2,08 Å.
    Notes: Abstract The structure of bis(ethylenediamine)nickel(II)tetracyanopalladate(II), Ni(NH2CH2CH2NH2)2Pd(CN)4, has been determined from three-dimensional X-ray data, using Weissenberg photographs. The compound crystallizes with two molecules in the monoclinic space group P21/n with a=7.174(10), b=10.740(15), c=10.135(15) Å, β=115.0(5)°. The measured and the calculated density is 1.83 g/cm3. Anisotropic refinement gave a finalR factor of 10.2%. The structure consists of infinite chains, -Pd-C-N-Ni-N-C-, parallel to thec-axis. Two trans-nitrogen atoms of the square Pd(CN) 4 2− are linked to Ni, leading thus to a polynuclear compound with an octahedral [NiN6] group in agreement with visible and infrared spectra. The trans-Ni(NH2CH2CH2NH2)2(NC)2-group has an asymmetric “gauche” (δλ)-conformation. Average distances are: Pd-C: 1.96 Å, C≡N: 1.15 Å, Ni-N: 2.08 Å.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 419-429 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermodynamic functions of biopolymer hydration were investigated by multitemperature vapor pressure studies. Desorption measurements were performed that allowed determination of reversible isotherms in the hydration range of 0.1 to 0.3-0.5 g H2O/g dry polymer. These isotherms are accessible to thermodynamic interpretation and are relevant to the interaction of water with biopolymers in their solution conformation. The results obtained on a series of different biopolymers (lysozyme, α-chymotrypsin, apo-lactoferrin, and desoxyribonucleic acid), show the following common features of interest: (1) The differential excess enthalpies (ΔHe) and entropies (ΔSe) are negative, and exhibit pronounced anomalies in a well-defined low-humidity range (approx. 0.1 g H2O/g dry polymer). These initial extrema are interpretable by structural changes, induced in the native biopolymer structures by water removal below a critical degree of hydration. (2) The ΔHe and ΔSe terms exhibit statistically significant linear enthalpy-entropy compensation effects in all biopolymer-water systems investigated. The compensation temperatures \documentclass{article}\pagestyle{empty}\begin{document}$ \hat \beta = \overline {\Delta H} ^e /\overline {\Delta S} ^e $\end{document} are approximately identical for all biopolymers, ranging from 360 to 500 K. The compensation effects are attributable to phase transitions of water molecules between the bulk liquid and the inner-sphere hydration shell of native biopolymers. (3) The negative excess free energies (ΔGe) decrease monotonically with increasing water content and are close to zero at 0.3 to 0.5 g H2O/g polymer. This result indicates that only transitions between the bulk liquid and the inner-sphere hydration shell are associated with significant net free energy effects. The outer-sphere hydration water is thermodynamically comparable to bulk water. The importance of the proportionality factor \documentclass{article}\pagestyle{empty}\begin{document}$ \hat \beta $\end{document} in the control of the free energy term is discussed.
    Additional Material: 2 Ill.
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  • 7
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The primary hydration process of native biopolymers is analyzed in a brief review of the literature, pertaining to various aspects of biopolymer-water systems. Based on this analysis, a hydration model is proposed that implies that the solution conformation of native biopolymers is stable at and above a critical degree of hydration (hp′ = 0.06-0.1 g H2O/g polymer). This water content corresponds to the fraction of strongly bound water, and amounts to ∼20% of the primary hydration sphere. In order to test this model, detailed sorption-desorption scanning experiments were performed on a globular protein (α-chymotrypsin). The results obtained are consistent with the proposed hydration model. They show that under certain experimental conditions, sorption isotherms can be obtained that do not exhibit hysteresis. These data represent equilibrium conditions and are thus accessible to thermodynamic treatment. Valid thermodynamic functions, pertinent to the interaction of water with biopolymers in their solution state, can be obtained from these sorption experiments.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1465-1471 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Infrared spectra of myoglobin, ribonuclease, lysozyme, α-chymotrypsin, α-lactalbumin, and β-lactoglobulin A were obtained in deuterium oxide solution in units of absorbance versus wavenumber from 1340 to 1750 cm-1. The spectra were resolved into Gaussian components by means of an iterative computer program. Resolved characteristic absorption peaks for the two infrared active amide I′ components of antiparallel chain-pleated sheets (β-structure) were obtained. The characteristic amide I′ peaks of α-helical regions and apparently unordered regions overlap in D2O solution. Absorptivity values for the resolved β-structure peak around 1630 cm-1 were estimated on the basis of the known structure of ribonuclease, lysozyme, and β-chymotrypsin. The β-structure content of β-lactoglobulin was estimated to be ca. 48% of α-lactalbumin ca. 18%, and of αs-casein close to zero. The results are in general agreement with conclusions drawn from circular dichroism and optical rotatory dispersion studies.
    Additional Material: 2 Ill.
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  • 9
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of enzyme-inhibitor complex formation on the hydration properties of the macromolecular moiety was investigated on the model system of α-chymotrypsin and its Ser-195 tosyl derivative. The primary (A-shell) hydration of the native and modified enzyme was compared by sorption measurements. The secondary (B-shell) hydration water was investigated by differential scanning calorimetry. Tosylation is known to induce pronounced conformational changes in the chymotrypsin molecule. These structural modifications have the following effects on the hydration of the native enzyme.The water binding capacity of the protein surface is significantly increased, as shown by both the calorimetric and the sorption results. The amount of unfreezable water of primary hydration is increased by 50 mol H2O/mol chymotrypsin.The heats (ΔH) and entropies (ΔS) of the interaction of water with chymotrypsin are strongly reduced in the modified enzyme. This effect is interpretable by a reduction of the H bonding potential of the protein surface. Parallel to this decrease in δH, the heats of fusion of the secondary hydration water (Qfus) are significantly increased by tosylation (Qfus = 256.2 ± 7.8 and 294.2 ± 4.8 J g-1 H2O for the native and the tosylated enzyme, respectively). This increase in Qfus reflects an increase in the extent of H bonding in the B-shell hydration sphere.These changes in the hydration of the native enzyme, associated with the reaction: native chymotrypsin → tosylchymotrypsin, are interpreted by cooperative phase transitions of water molecules in the primary and secondary hydration water. One of these transitions was found to exhibit a significant, linear enthalpy-entropy compensation effect. The compensation temperature \documentclass{article}\pagestyle{empty}\begin{document}$ \hat{\beta} $\end{document} is 290.7 ± 2.8°K. This \documentclass{article}\pagestyle{empty}\begin{document}$ \hat{\beta} $\end{document} value agrees well with compensation temperatures reported in the literature for a series of biochemical reactions in aqueous solution (250-320° K). This agreement in \documentclass{article}\pagestyle{empty}\begin{document}$ \hat{\beta} $\end{document} may point to a common source of both compensation phenomena.
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