UNSPECIFIED. (2000) Amine induced Z-DNA in poly(dG-dC)center dot poly(dG-dC): Circular dichroism and gel electrophoresis study. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 2 (23). pp. 5469-5478. ISSN 1463-9076

Abstract

Spermine and [Co(NH3)(6)](3+) are known to induce the B -->Z transition in poly(dG-dC). poly(dG-dC) DNA. In this paper gel electrophoresis shift assays using the long DNA poly(dG-dC). poly(dG-dC) are developed to complement circular dichroism (CD) measurements of the conformation of the DNA in the presence of amines including spermine, spermidine, [Co(NH3)(6)](3+), (+)- [Co(en)(3)](3+) and (-)-[Co(en)(3)](3+) (en: ethylenediamine). CD is used to monitor the average conformation of the DNA and the gels show when there is a population of a given type of DNA in the solution. Spermidine is found to induce the transition at very low ionic strength, in contrast to literature wisdom. The cobalt amine-induced Z-DNA melts, with a broad transition, at a lower temperature than B-DNA. The electrophoresis data shows the presence of a DNA more flexible than B-DNA at low amine concentrations. This is ascribed to the existence of B/Z junctions. At higher amine concentrations, a DNA (Z-DNA) that is stiffer than B-DNA is observed. The Z-DNA induced by spermine is stiffer (runs more slowly on the gels) than that induced by the other amines. The spermine-DNA interaction is found to be very cooperative, whereas that of the cobalt amines is uncooperative. The kinetics of the B -->Z transition with spermine at room temperature is very slow, whereas the cobalt amines induce it within seconds.

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