KINFIT-II - A NONLINEAR LEAST-SQUARES PROGRAM FOR ANALYSIS OF KINETICBINDING DATA

We describe a versatile computer program for least-squares fitting of ligand/receptor association and dissociation curves from several exper iments simultaneously. The program is designed to handle any number of classes of binding sites reacting with a single ligand that may have two forms: labeled and unlabeled. For a single class of binding sites, the exact, analytical solution is used to generate the computed curve s. For more than one class of sites, the computed curves are generated through numerical solution of a set of ordinary differential equation s. The parameters determined with this procedure are the on- and off-r ate constants and the concentrations of each binding site class. An ex tensive selection of experimental designs can be processed. The times of observation may be freely chosen, although that choice will affect the quality of the results. Starting with a sample material (e.g., cel ls, membranes, macromolecules), one can preincubate (to equilibrium) w ith any combination of labeled and unlabeled ligand. One can then pert urb the system by adding any combination of labeled and cold ligand or simply diluting the sample; such an experiment can be continued throu gh several perturbations. A variety of such runs may be combined for a nalysis as a single data set.