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Premelting thermal fluctuational base pair opening probability of poly(dA) · poly(dT) as predicted by the modified self-consistent phonon theory (1991)

Chen, Y. Z. ; Feng, Y. ; Prohofsky, W.

New York : Wiley-Blackwell

Biopolymers 31 (1991), S. 139-148

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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 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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Premelting thermal fluctuational interbase hydrogen-bond disrupted states of a B-DNA guanine-cytosine base pair: Significance for amino and imino proton exchange (1991)

Chen, Y. Z. ; Zhuang, W. ; Prohofsky, E. W.

New York : Wiley-Blackwell

Biopolymers 31 (1991), S. 1273-1281

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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: 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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Concentration dependence of surface diffusion and zeolitic diffusion (1991)

Chen, Y. D. ; Yang, R. T.

Hoboken, NJ : Wiley-Blackwell

AIChE Journal 37 (1991), S. 1579-1582

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ISSN: 0001-1541

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology

Additional Material: 3 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/aic.690371015

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Nylon 4/PVA blend membrane for dialysis (1991)

Lai, J. Y. ; Chen, Y. C. ; Hsu, K. Y.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 43 (1991), S. 1795-1804

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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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