The reconstitution of histone H3H4 tetramer from acid extracted histones in the absence of urea

Simple mixing of acid purified histones H3 and H4 in equimolar quantities at low ionic strength near pH 7 does not yield the tetramer but rather a high Mr aggregate. Dialysis of acid extracted total or core histones into 2 M NaCl 150 mM phosphate (pH 7.4) followed by fractionation of the histone complexes at lower ionic strength (150 mM NaCl) results in an H3-H4 tetramer of a structure identical to that derived from salt-extracted histones. Dialysis of acid extracted total or core histones directly into the lower ionic strength buffer with subsequent fractionation, results in H3-H4 tetramer of closely similar structure.