Helix melting

Williams S, Causgrove T P, Gilmanshin R, Fang KS, Callender R H, Woodruff WH and Dyer R B 1996 Fast events in protein folding helix melting and formation in a small peptide Biochemistry ZS 691-7... 

Thirdly, experiments concerned with the whole process of conformational change and the unzipping process (e.g., [49]) studied the mechanical stability of individual double-stranded DNA molecules. It was foimd that the B-S transition of A-DNA occurred at 65 pN, followed by a second conformational transition during which the DNA double helix melted into two... 

Below 200°C, the heat-induced changes in dry wool structure are confined to the amorphous parts of the protein. Above 200°C two melting endotherms are present, a small one at 215 °C from the melting of a low crosslinked fraction of the helix and a major one at 235°C as a result of the melting of the higher crosslinked fraction of the helix (49). In wool, the most direct evidence for this interpretation of helix melting is provided by x-ray diflFraction patterns at the various temperatures. 

Y. A. Chen and E. W. Prohofsky, Sequence and temperature dependence of the interbase hydrogen-bond breathing modes in B-DNA polymers comparison with low-frequency Raman peaks and their role in helix melting. Biopolymers, 35(6), 573-582 (1995). 

A sample of human DNA is subjected to increasing temperature until the major fraction exhibits optical density changes due to disruption of its helix (melting or denaturation). A smaller fraction is atypical in that it requires a much higher temperature for melting. This smaller, atypical fraction of DNA must contain a higher content of... 

One property of many such transformations is their all or none character. For example, if proteins in solution are slowly heated they often remain in their native states until a certain temperature is reached, when they become denatured rather suddenly. Similarly, if we heat a solution of DNA, and follow the structural changes by spectrophotometry, we find that nothing happens until a temperature of about 80 C is reached then, within a few degrees, the helix melts to a form in which the various long-chain molecules are coiled at random. If we write an equilibrium constant as... 

S. Williams, T. P. Cosgrove, R. Gillmanshin, K. S. Fang, R. H. Callender, W. H. Woodruff, and R. B. Dyer, Fast events in protein folding Helix melting and formation in a small peptide. Biochemistry 35, 691-697 (1996). 

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