Spectroscopic Studies of Five Purified Histones from Calf Thymus

Calf thymus histones have been fractionated by column chromatographic procedures with carboxymethyl cellulose and Sephadex. Characterization of some of the fractions was performed by acrylamide gel electrophoresis, amino acid composition, peptide mapping, and sedimentation. Five of the fractions obtained were shown to be essentially homogeneous. Ultraviolet absorption spectra, optical rotatory dispersion, and circular dichroism of five histones have been determined. These histones exhibit spectra through which it is thus possible to differentiate them. The rotatory dispersion results indicate that the different conformational behavior of these five histones depends on environmental conditions such as salt concentration and organic solvent concentration. A slightly lysine-rich histone fraction was found to contain a minute amount of nonprotein components, which appears to be tightly bound oligonucleotide. X-ray diffraction patterns and infrared spectra exhibited by this fraction are also presented.