On the kinetics of helix formation between complementary ribohomopolymers and deoxyribohomopolymers.

Abstract

AbstractThe rate of double helix formation by single‐stranded poly A plus poly dT, poly dA plus poly U, poly dA plus dT, poly G plus poly dC, poly dG plus poly C, and poly dG plus poly dC have been investigated and compared to rates of ribohomopolymer helix formation rates. After correction for molecular weight, comparisons of rate data at 30°C below the melting temperature of the double helix show that: Rates of helix formation by all combinations of guanine plus cytosine homopolymers are the same. The rate of helix formation for poly dA plus poly dT is three times faster than the rate for poly A plus poly U. Rates of formation of DNA‐RNA hybrid molecules are intermediate between these two rates, but closer to the poly dA plus poly dT rate. The effect of temperature on the rate of helix formation is interpreted in terms of a steady‐state model for helix propagation. The results are consistent with a mechanism in which the formation of the second base pair is the rate‐determining step.