Selective removal of histones from calf-thymus nucleohistone with sodium dodecylsulfate.

Calf-thymus nucleohistone studied by a newly developed ;SDS gradient' centrifugation technique showed that histones dissociate sequentially when treated with increasing concentrations of sodium dodecylsulfate. Histones F2a1 and F2a2 were dissociated first at about 0.03% sodium dodecylsulfate, and F1 was removed lastly by the highest concentration of sodium dodecylsulfate (0.06% or more). A DNA-histone F1 complex, which consisted of DNA and all of the histone F1 and completely lacked other histones, was obtained by sedimenting nucleohistone through 0.05% sodium dodecylsulfate. Results of equilibrium gel filtrations in 0.05% sodium dodecylsulfate revealed that the binding of sodium dodecylsulfate to nucleohistone caused new binding sites to be available for the detergent which presumably was accompanied with dissociation of histones from DNA. This result indicates that no redistribution of histone F1 on DNA should occur in the presence of 0.05% sodium dodecylsulfate.