Thermodynamic description of oligonucleotide self-association in DNA concatamer structures

Abstract

A scheme of equilibrium formation of concatamers by two different oligonucleotides has been considered. It is shown that in the general case, the dependence of the concentration of oligonucleotide components on temperature cannot be found in analytical form. Therefore, it is impossible to find the thermodynamic parameters of concatamer formation (ΔH ⁰, ΔS ⁰) and melting temperatures by analyzing the profiles of thermal denaturation of oligonucleotide complexes. An algorithm for numerical solution of implicit dependences has been developed. A number of approaches are considered that simplify the analysis of heat denaturation curves for concatamer complexes. It is shown that the dependence of the efficiency of concatamerization on temperature can be described analytically when duplex fragments have close stability and there is no cooperativity at the oligonucleotide junction. In this case, the dependence of melting temperature on thermodynamic parameters and oligonucleotide concentration has the same form as in the case of the duplex structure formed by a pair of non-self-complementary oligonucleotides. The ability of various model approaches to describe the experimental curves of concatamer heat denaturation is evaluated. For concatamer structures used as signal amplifiers in DNA hybridization analysis, a function is introduced that shows the relative contribution of a concatamer of given length to the magnitude of signal amplification. The dependence of the maximum of this function on the concentration of oligonucleotides, the thermodynamic characteristics of their complexes, and temperature has been determined. It is shown by the gel retardation assay that the function of the length distribution of concatamers qualitatively correlates with the experimental dependences.