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Theory of the Effects of Concentration and Chain Length on Helix—Coil Equilibria in Two-Stranded Nucleic Acids

1963; American Institute of Physics; Volume: 39; Issue: 10 Linguagem: Inglês

10.1063/1.1734089

1520-9032

Jon Applequist, Vinayak N. Damle,

RNA Interference and Gene Delivery

The formalism for treating a dissociating two-stranded helix is developed from the system partition function. The behavior of finite chains is examined according to the model in which only one helical region is allowed in a molecule, and staggering of the paired strands is not allowed. Numerical results for chain lengths in the range of 1 to 300 residues show that the helix—coil transition curve is markedly broadened and shifted as the chain length decreases, and that a decrease in concentration results in a significant decrease in degree of bonding for chain lengths less than about 100. The ultraviolet absorbance transition curves are calculated from the Rich—Tinoco predictions for stack-length dependence of hypochromicity, and are found to be markedly different from the transition curves in terms of degree of bonding for chain lengths less than about 100.