Critical Electrolyte Concentration of Chicken Erythrocyte Chromatin

This study examined whether chicken erythrocyte chromatin, whose great physicochemical stability is promoted by histone H5, has a critical electrolyte concentration (CEC) value comparable to that of other chromatin types with special condensed packing states but devoid of H5. The affinity for toluidine blue molecules under Mg2+ competitive binding action was thus investigated. The CEC value was found to be 0.12M, which is close to that of heterochromatin from mouse liver cells and to sperm chromatin with histone H1 variants. Acetic ethanol fixative was found to affect the CEC, possibly by influencing the chromatin packing state and DNA phosphate availability through dissociation of proteins from the DNA. The phenomenon of programmed cell death was considered to contribute to high CEC values by inducing special states of chromatin condensation.