CORRELATIONS BETWEEN BIOLOGICAL-ACTIVITY AND THE NUMBER OF FUNCTIONAL-GROUPS CHEMICALLY MODIFIED

In interpreting the data obtained by chemical modification of biologically active macromolecules, e.g. enzymes, it has been a common practice to plot the remaining activity against the number of residues modified. An extrapolation of the initial, nearly linear portion of the curve generated to the axis giving numbers of residues often has been presumed to specify the actual number of critical groups modified. That this is usually not the case can be shown if one considers treatment of a typical macromolecule containing a number of a given kind of modifiable residues among which some, including those that are essential for activity, react at one rate, and the remainder react at a different rate. The behavior and character of the plots obtained have been analyzed and are presented with numerical and experimental examples to illustrate those features that should be considered. © 1979.