Modeling concurrent binding of multiple molecular species in cell adhesion

Cell adhesion provides not only physical linkage but also communication bet ween the cell and its environment. As such, it is important to many cellula r functions. Recently, The probability distribution of forming a low number of specific adhesive bonds in a short-duration contact has been described (Chesla et at., Biophys. J., 1998, 75:1553-1572). This model assumes that b inding occurs between a single receptor species and a single ligand species . However, cell adhesion molecules rarely work alone in physiological setti ngs. To account for these in vivo situations, we extended the previous mode l to include concurrent interactions of multiple receptor-ligand species, i ntroducing the concept of independent binding. Closed-form solutions have b een obtained for cases where competition is absent or can be neglected. In two companion papers (Williams et al., Biophys. J., 2000, 79:1858-1866;2000 , 79:1867-1875), the model developed herein has been applied to analyze two sets of experiments designed such that the validity of the theory was also tested.