Stability of Helical Nucleic Acids
One intensive application of the statistical mechanics of order-disorder transitions has been to the formation or denaturation of helical structure in nucleic acids. The existence of extremely long double-stranded helices in DNA and certain species of RNA leads to a natural replacement of the base-pairs by sites on a one-dimensional lattice capable of interacting with neighboring sites, reducing the statistical mechanical problem to a class related to the one-dimensional Ising model (1). Given a reasonable physical description of the helix nucleation and zippering processes then, it has proven possible to estimate the energetics of helix formation by comparing predicted theoretical transition profiles with experimentally measured curves (2, 3, 4). The denaturation of high molecular weight synthetic or natural helices can be monitored, for example, by the increase in absorbance of a solution of the molecules upon raising the temperature. Typically, abrupt cooperative transitions are observed, which are only slowly or partially reversible in the case of natural DNA’s but fully so in the case of synthetic species (Fig. 1).
KeywordsSugar Entropy Urea Enthalpy Polypeptide
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