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Helix–coil transition in heterogeneous chains. II. DNA model
Author(s) -
Eichinger B. K.,
Fixman M.
Publication year - 1970
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1970.360090206
Subject(s) - chemistry , cooperativity , crystallography , dna , base pair , helix (gastropod) , molecule , thermodynamics , random coil , nucleotide , melting curve analysis , physics , circular dichroism , organic chemistry , ecology , biochemistry , polymerase chain reaction , snail , gene , biology
Melting curves are calculated for infinitely long DNA‐like random copolymers composed of AT and GC pairs of nucleotides. The entropy of random coil rings formed on melting is explicitly included through use of the Jacobson‐Stockmayer ring‐weighting factors. Transition curves are calculated for values of the cooperativity parameter σ in the range 10 −2 ⩽ σ ⩽ 10 −4 . Ninety percent of the melting occurs in ca. 0.2°C for σ ⩽ 10 −3 regardless of the mole fraction of GC. We conclude that observed breadths of thermal denaturation curves for native DNAs result from a superposition of essentially all‐or‐none melting of various regions of the molecule. It is argued that refined approximations to the ring‐weighting factors are probably not important when compared with the effects produced by long‐range base sequence correlations which are known to occur in native DNA.