Preliminary x-ray studies of the interaction of salmon sperm DNA with spermine

The interaction of spermine with salmon sperm DNA was studied by X-ray diffraction methods. In the fibers of the complex, DNA was in the B-configuration with ten nucleotide pairs per turn (34 Å) of the helix at 92% or higher relative humidity, while, at 75% and lower relative humidity, it was at least partly in the A-configuration, which was not observed in a similar experiment by Suwalsky et al. (1969) with calf thymus DNA. The A to B transition of the complex fibers was reversible.