SUNY at Albany
June 19-23, 2001
Single DNA Molecule Melting By Mechanical Force
Recently observed phenomenon of B-DNA highly cooperative elongation to about twice its contour length under the action of ~65 pN mechanical force applied to the opposite ends of the torsionally unconstrained molecule is interpreted as a force-induced melting of DNA double helix. Experimental stretching curves for the double and single stranded DNA are used to obtain force dependent contribution to the free energy of melting transition. General theory of the force-induced DNA melting is developed. Traditional questions of the theory of DNA melting, such as DNA sequence heterogeneity, cooperativity including the loop factor, melting kinetics are discussed for DNA melting by force. New data on the dependence of the overstretching force on solution ionic strength, pH, temperature and presence of nucleocapsid protein is quantitatively explained by the new theory. General method for studying stability of a doublehelix by stretching is suggested as an alternative to the conventional thermal melting of DNA. Effects of the force on the DNA polymerase activity are discussed.
I. Rouzina. M. C. Williams, J. R. Wenner, V. A. Bloomfield
Department of Biochemistry. University of Minnesota,