AbstractThe Raman spectra of aqueous solutions of calf thymus histone complexes H2A:H2B and H3:H4 have been recorded and are compared with those of the individual histones. The results show an increase of α‐helix content on formation of these complexes, at the expense of random‐coil conformation in H2A:H2B and β‐sheet structure in H3:H4. The α‐helix content is estimated to be 40% in H2A:H2B and 35% in the H3:H4 complex. The intensity ratios of the 850/830 cm−1components of the tyrosine doublet in the spectra of both complexes are the averages of the values for the individual histones, suggesting that the environment of these residues is little modified on formation of the complexes. Variations in the intensity of the 1400 cm−1carboxyl band has been observed to be associated with conformational changes, which is consistent with the notion that COO−/NH 3+, NH 2+interactions play a major role in histone