Studies on nucleic acid reassociation kinetics: retarded rate of hybridization of RNA with excess DNA.

The rate of reaction of excess double-stranded bacteriophage phiX174 and plasmid RSF2124 DNA drivers with enzymatically synthesized asymmetric RNA tracers was measured. Other reactions were carried out with excess Escherichia coli DNA and E. coli RNA labeled in vivo. RNA and DNA fragment lengths were held approximately equal. For each case it was shown that in DNA excess the rate constant for RNA-DNA hybridization is 3- to 4.5-fold lower than that of the renaturation rate constant for the driver DNA. This retardation was also observed in pseudo-first-order hybridization reactions driven by excess strand-separated RSF2124 DNA. It was concluded that the rate constant for RNA-DNA by hybridization depends partially on which species is in excess.