TWO NEW PHOTOAFFINITY POLYAMINES APPEAR TO ALTER THE HELICAL TWIST OF DNA IN NUCLEOSOME CORE PARTICLES

Two new photoaffinity derivatives of polyamines have been synthesized by the reaction of spermine or spermidine with methyl 4-azidobenzimidate. The new compounds were purified chromatographically and characterized by several methods including proton magnetic resonance spectroscopy. The spermine derivative is N 1 -ABA-spermine [(azidobenzamidine) spermine], and the spermidine derivative is a mixture of N 1 - and N 8 -ABA-spermidine. ABA-spermine stabilizes nucleosome core particles in thermal denaturation experiments, with similar but not identical effects when compared with the parent polyamine, spermine. In circular dichroism experiments, ABA-spermine was capable of producing a B→Z transition in poly(dG-m 5 dC) at a concentration of 30μM, compared with 5μM required to produce the same effect with spermine