## Abstract 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 calcula
Helix–coil transition in heterogeneous DNA
✍ Scribed by Marshall Fixman
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1975
- Tongue
- English
- Weight
- 875 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Abstract
The broadening of a helix–coil transition due to base pair heterogeneity is calculated on the basis of a cumulant perturbation expansion in the quasi‐grand ensemble. In this ensemble the fictitious, homogeneous chain, to which the perturbation is referred, automatically decreases its correlation length as the heterogeneity increases. This “renormalization” seems to stabilize the perturbation expansion, in view of the good agreement between the present results and the exact theory of a heterogeneous polypeptide helix–coil transition. For the DNA model in which ring entropy is included, the transitions is found to be extremely narrow for an infinite random chain with conventional parameters. A tentative reconciliation of this result with contradictory calculations of some other workers is offered on the basis of end effects, coarse graining, or approximation to the ring entropy. An application of the new method to DNA with a non‐random base pair distribution requires evaluation of the correlation function between molecular states (helix or coil), at different sites of the reference chain. The evaluation is reduced to quadrature, but numerical calculations have been made only for the random chain.
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## Abstract We show that the fine oscillatory structure of the DNA melting curve can be used to determine explicitly the nucleotide composition and the order of certain domains within the DNA. If DNA is specifically fragmented, the order of fragments can be learned directly from a comparison of the
## Abstract Helix–coil transition in very long DNA (containing hundreds of thousands of nucleotides or more) is considered. Certain statistical information about DNA nucleotide sequence is obtained.
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