## Abstract The approximations in the equation relating the viscosity of partially helical molecules to the cooperativity of the helix–random coil transition are investigated. Of the several approximations considered, only the neglect of long‐range intramolecular interactions in the random coil lea
On the form of the partition function for the helix–coil transition of random copolymers
✍ Scribed by D. M. Crothers
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1966
- Tongue
- English
- Weight
- 492 KB
- Volume
- 4
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
The purpose of this paper is to examine and contrast several formulations of the partition function for the helix-coil transition of random-sequence nucleic acids. In the exact approach, the sequence of bases in a given molecule is fixed, but this leads to expressions which are difficult to evaluate. Another approach is to make a summation over all possible sequenoes, each weighted by the probability of its occurrence, thereby in effect allowing all sequences to a given molecule. The error in this approach is that it does not guarantee that the average base sequence is random. This difficulty can, in principle, be overcome by applying successively increasing constraints on the system to ensure that all moments of the distribution are equal to the random-sequence values. It is shown for the particular case of short molecules which melt only from the ends that the convergence of this method to the true solution is poor. The major conclusion is that composition fluctuations which cover a sizeable region of the molecule must be included in an accurate description of the melting transition.
📜 SIMILAR VOLUMES
The absorption spectrum of the aqueous solution of acridine orange (A0)-poly-(D-glutamic acid) (PDGA) complex a t pH 4.5 (helix form) did not show any wavelength shift, but at pH 7.5 (coil form) changed to the absorption curve of the helix form by compression up to 4500 atm. The ionization degree of
## Abstract It is concluded on the basis of comparison of polyelectrolyte theory with published data that the mean phosphate spacing __b__ along the contour axis of an unfolded polynucleotide single strand is in the range 3–4 Å (polyelectrolyte parameter ξ ≈ 2), regardless of temperature, base comp