Fluorescence study of the effects of histone tyrosyl residues of DNA

The fluorescence spectra of histone-DNA complexes at pH 7.0 were studied. These species showed fluorescence spectra broader than the characteristic histone spectrum, with the appearance of peaks at higher wavelengths. It is shown that the emission at higher wavelengths arises from the bases of DNA (specially from the A-T bases), when their hydrogen bonds are weakened or broken. These results corroborate those of other authors and it is postulated that tyrosine residues in histone form hydrogen bonds with DNA and/or stack with the bases of the nucleic acid.