Complexes of histone F1 with DNA in 0.15M NaCl. Circular dichroism and structure of the complexes

Conditions were studied under which aggregated complexes of histone F1 with DNA display a circular dichroic spectrum of nonconservative type characterized by two intense negative maxima at 269 nm and 209 nm. It was found that the intensity of the longwave band depends directly on the content of guanine plus cytosine and inversely on the molecular weight of DNA. The same type of dependence was found for DNA's of eukaryotic and bacterial origin. It appears that the formation of the nonconservative spectrum which can be ascribed to a certain structural form of DNA is caused by orientation of the DNA molecules in the aggregated complex and by specific interactions of the bases of the guanine–cytosine pair. The possible mechanism of formation of nonconservative dichroic spectrum is discussed with respect to special properties of guanine.