Thermodynamics of DNA: heat capacity changes on duplex unfolding.

ABSTRACT: The heat capacity change, ?Cp, accompanying the folding/unfolding of macromolecules reflects their changing state of hydration. Thermal denaturation of the DNA duplex is characterized by an increase in ?Cp but of much lower magnitude than observed for proteins. To understand this difference, the changes in solvent accessible surface area (?ASA) have been determined for unfolding the B-form DNA duplex into disordered single strands. These showed that the polar component represents?~?55% of the total increase in ASA, in contrast to globular proteins of similar molecular weight for which the polar component is only about 1/3rd of the total. As the exposure of polar surface results in a decrease of ?Cp, this explains the much reduced heat capacity increase observed for DNA and emphasizes the enhanced role of polar interactions in maintaining duplex structure. Appreciation of a non-zero ?Cp for DNA has important consequences for the calculation of duplex melting temperatures (Tm). A modified approach to Tm prediction is required and comparison is made of current methods with an alternative protocol.

SUBMITTER: Dragan A 

PROVIDER: S-EPMC6853854 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature