Spectrophotometric Determination of the Dissociation Constant of Ribonuclease S'

Spectrophotometric determination of the dissociation constant of ribonuclease S' at low ionic strength and in the absence of substrate yields values for Kd three to four orders of magnitude larger than those determined by using recovery of activity as the criterion for association. These values correspond with calculations from earlier data from another laboratory, and seem reasonable for a peptide-protein interaction involving noncovalent bonds.