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  • Polymer and Materials Science  (10)
  • Column liquid chromatography
  • 1990-1994  (11)
  • 1
    Electronic Resource
    Electronic Resource
    Premelting thermal fluctuational base pair opening probability of poly(dA) · poly(dT) as predicted by the modified self-consistent phonon theory (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 139-148 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We employ a mean field, modified, self-consistent phonon theory to evaluate the single base-pair opening rate and the probability of a base pair in the amino proton exchangeable state for the homopolymer poly(dA) · poly(dT) at temperatures below the helix-coil transition region. Our calculated premelting single base-pair opening probabilities are in general agreement with several available experimental estimates from imino proton exchange and formaldehyde-induced DNA melting measurements. These calculated opening probabilities, however, are in disagreement with the prediction of the helix-coil transition theory. Possible reasons for the differences are discussed, especially the possible different definition of a meaningful open state in the premelting region. The premelting open state of the modified self-consistent phonon approximation theory seems to be appropriate to describe a solvent-accessible open configuration that is sufficient to facilitate important chemical reactions such as imino proton exchange and formaldehyde reaction with the bases. This can be compared with the completely unstacked open state of the helix-coil transition theory originally defined in the helix-coil transition region. We propose that the amino proton exchangeable state is different from the open state associated with melting and only involves the breaking of the amino interbase H bond. The agreement between the calculated and experimentally estimated probability of a base pair in the amino proton exchangeable state seems to support this hypothesis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310202
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  • 2
    Electronic Resource
    Electronic Resource
    Hybrid Monte Carlo simulations theory and initial comparison with molecular dynamics (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1307-1315 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A formal partially dynamical approach to ergodic sampling, hybrid Monte Carlo, has been adapted for the first time from its proven application in quantum chromodynamics to realistic molecular systems. A series of simulations of pancreatic trypsin inhibitor were run using temperature-rescaled molecular dynamics and hybrid Monte Carlo. It was found that simulations run using hybrid Monte Carlo equilibrated an order of magnitude faster than those run using temperature-rescaled molecular dynamics. Certain aspects of improved performance obtained using hybrid Monte Carlo are probably due to the increased efficiency with which this algorithm explores phase space. To discuss this we introduce the notion of “trajectory stiffness”. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330815
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  • 3
    Electronic Resource
    Electronic Resource
    Premelting thermal fluctuational interbase hydrogen-bond disrupted states of a B-DNA guanine-cytosine base pair: Significance for amino and imino proton exchange (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 1273-1281 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modified self-consistent phonon theory when applied to the DNA double helix indicates the existence of fairly long-lived states in which single interbase H bonds are disrupted. One can then postulate a number of situations in which particular disrupted H bonds can enhance particular proton exchange. In this paper we postulate a number of such partially open states for a B-conformation GC base pair and calculate the probability of each of these states for a B-conformation poly(dG) · poly(dC). We compare these probabilities to those probabilities needed to explain various observed proton exchange rates. We propose that, for a GC base pair in B conformation, there are two amino proton exchangeable states - a cytosine amino proton exchangeable state and a guanine amino proton exchangeable state; both require the disruption of only the corresponding inter base H bond. The imino proton exchange, however, requires the disruption of all three inter base H bonds and this defines a third open state. Our calculated probabilities for a GC base pair in these three states are in fair agreement with available experimental estimates from measurements of amino and imino proton exchange.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360311105
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular shape recognition capability of liquid-crystal bonded phases in reversed-phase high performance liquid chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 295-303 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Liquid crystal phases ; Molecular shape recognition ; Polycyclic aromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic retention behaviour of two liquidcrystal bonded phases have been evaluated using polycyclic aromatic hydrocarbons (PAHs) as the probe samples in reversed-phase high performance liquid chromatography (RP-HPLC). The results clearly indicate that these phases have better planarity and shape recognition capabilities than commercially-avaialble polymeric octadecylsilica (ODS) phases whose strong planarity and shape selectivities were found earlier. It can also be concluded from the chromatographic observations that the shape recognition capability of these phases is dependent on both mobile phase composition and column temperature, but that the effect of mobile phase and temperature on the shape selectivity work independently. The retention behaviour can be explained by changes in the phase structure with changes of eluent composition and temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269771
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  • 5
    Electronic Resource
    Electronic Resource
    Differences in melting behavior between homopolymers and copolymers of DNA: Role of nonbonded forces for GC and the role of the hydration spine and premelting transition for AT (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 797-812 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Melting measurements of the mono-base-pair DNA polymers showed that the melting temperature Tm of the B-DNA homopolymer poly (dA ) · poly (dT) is higher than that of the copolymer poly [d(A-T)]. On the other hand, the Tmof the B-DNA homopolymer poly (dG) · poly (dC) is lower than that of the copolymer poly [d (G-C)]. From a structural point of view, the cross-strand base-stacking interaction in a DNA homopolymer is weaker than that in a DNA copolymer with the same base pair. One would then expect that all the DNA homopolymers are less stable than the copolymer with the same base pair. We find that the inversion of the melting order seen in the AT mono-base-pair DNA polymers is caused by the enhanced thermal stability of poly (dA) · poly (dT) from a well-defined spine of hydration attached to its minor groove. In this paper we employ the modified self-consistent phonon theory to calculate base-pair opening probabilities of four B-DNA polymers: poly(dA)-poly(dT), poly(dG) · poly(dC), poly[d(A-T)], and poly[d(G-C)] at temperatures from room temperature through the melting regions. Our calculations show that the spine of hydration can give the inverted melting order of the AT polymers as compared to the GC polymers in fair agreement with experimental measurements. Our calculated hydration spine disruption behavior in poly(dA) · poly(dT) at premelting temperatures is also in agreement with experimentally observed premelting transitions in poly (dA) · poly (dT). The work is in a sense a test of the validity of our models of nonbonded interactions and spine of hydration interactions. We find we have to develop the concept of a strained bond to fit observations in poly (dA) · poly(dT). The strained-bond concept also explains the otherwise anomalous stability of the hydration chain. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330508
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  • 6
    Electronic Resource
    Electronic Resource
    A cooperative self-consistent microscopic theory of thermally induced melting of a repeat sequence DNA polymer (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 351-362 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We attempt to extend the modified self-consistent phonon theory to describe thermal fluctuational base-pair opening of repeat sequence DNA polymers in the helix-coil transition region as well as in the premelting region. A microscopic base-pair open state is introduced and the effect of this open state is taken into account self-consistently in a mean field system that models the DNA polymer. Our analysis indicates the structure of this open state changes with temperature in such a manner that on average a base pair opens and unstacks with its neighbors more completely as temperature increases. We apply this theory to a homopolymer - poly(dG) · poly(dC) to evaluate the base-pair opening probability in a temperature range from 273 to 366.5 K. At 366.5 K the system undergoes cooperative melting. Our calculated base-pair opening probabilities are in general agreement with several experimental estimates at room temperature. The calculated probabilities show typical melting curve behavior at temperatures close to the observed melting temperature. The cooperative modified self-consistent phonon approximation approach becomes a viable microscopic theory of melting. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330304
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  • 7
    Electronic Resource
    Electronic Resource
    Salt-Dependent stability of poly(dG) · poly(dC) with potential of mean force coulomb interactions (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 1123-1127 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360320819
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  • 8
    Electronic Resource
    Electronic Resource
    Langmuir-Blodgett films of polymethacrylates with side chains containing functionalized aromatic schiff's bases (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 165-173 
    Details
    ISSN: 0887-6266
    Keywords: Langmuir-Blodgett film formation by polymethacrylates with nonlinear optical side chains ; polymethacrylate films by Langmuir-Blodgett technique, configuration of nonlinear optical substituents in ; orientation of nonlinear optical moieties in Langmuir-Blodgett films of substituted polymethacrylates ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Langmuir-Blodgett (LB) film formation has been investigated for polymers in which non-linear optical (NLO) moieties are attached to the side chain of a polymethacrylate (PMA) backbone. Polymer monolayers were successfully transferred onto hydrophilic glass substrates using a moving-wall type LB trough. The LB films were characterized by pressure-area isotherms, polarized ultraviolet visible spectra, ellipsometry, and second harmonic generation measurements. The characterization shows that NLO moieties in the side chain are inclined at a shallow angle to the plane of the substrate. The second-order nonlinear optical coefficient and molecular hyperpolarizability were also calculated. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090310205
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of hexane treatment on the permeation of silicone-coated polyethersulfone membranesIssued as NRCC No. 31483. (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 2169-2176 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The polyethersulfone membranes were cast from casting solutions including poly(vinyl pyrrolidone) additive. The membranes were further dried, silicone-coated, and used for the permeation study with hydrogen and nitrogen gases. It has been found that solvent hexane which was included in the silicone rubber solution for surface coating increased the pore size on the membranes surface when poly(vinyl pyrrolidone) was present in the membrane. The above effect counteracted the pore size decrease by silicone coating, and, as a result, an H2/N2 permeability ratio of only 8.9 was achieved as compared with 28, which was obtained when the base polyethersulfone membrane was prepared from a casting solution without poly(vinyl pyrrolidone) additive.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410921
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  • 10
    Electronic Resource
    Electronic Resource
    Nylon 4/PVA blend membrane for dialysis (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1795-1804 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: To improve the hydrophilicity and enhance the transport flux of nylon 4 membrane for dialysis, this study attempts to utilize blending nylon 4 with poly(vinyl alcohol) (PVA). The instability of PVA in water can be obtained more easily than by other methods, such as chemical, γ-ray irradiated crosslinking, or high-temperature treatment used by previous researchers. The effects of maturation time of the casting solution, nylon 4/PVA ratios, and casting solvent compositions on esterification of PVA, salt permeability, water content, partition coefficient, diffusivity, and mechanical strength of membrances are studied. The membrane, prepared by casting solution of nylon 4/PVA = 9/1 wt % formic acid with 24-h maturation time, possesses permeabilities of NaCl and urea, 33.14 and 19.67 × 10-5 cm2/min, respectively.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070431003
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