Resistance of chromatin superstructure to tryptic digestion modulated by conjugated polyacrylamide

Soluble polyacrylamide conjugates have been used to modulate tryptic digestion of chromatin. Digestion of histones H1/H5 and H3 are mutually dependent and relatively independent of that of the core histones which are not significantly digested until 50-60% of H3 is degraded. H1/H5 and H3 are most exposed, H3 behaves as a "non-core' histone, its destruction appears to be the critical factor in the collapse of the chromatin superstructure during tryptic digestions. The digestion kinetics are explained by proposing that the initial sites of attack are in cavities much larger than the diameter of trypsin (4-5 nm). Procedures for the preparation of soluble polyacrylamide and its conjugation to trypsin are described.