Biopolym. Cell. 1986; 2(5):240-245.
Structure and Function of Biopolymers
A theoretical study of the B-A transition in superhelical DNA
1Pakhomov D. V., 1Vologodskii A. V.
  1. Institute of Molecular Genetics, Academy of Sciences of the USSR
    Moscow, USSR


The influence of DNA superhelicity on the alcohol-induced B–A transition in the solution is theoretically studied. Simple equations are obtained for the B–A transition point in circular DNA and for the width of transition curve. The theoretical predictions radically depend on the x parameter which characterizes the change in DNA winding angle as a resuit of the B–A transition. The shift of the transition point in circular DNA as compared with linear molecule depends also on the superhelical density. The shift of the transition point cannot exceed some limiting value. The possibilities to determine the K value on the basis of dependence of the B–A transition curve on the superhelical density in circular DNA are discussed.


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