Polymerization Kinetics of Biological Macromolecules on Templates

Abstract

A kinetics of formation of polymers on linear templates is developed which is applicable to the synthesis of biological macromolecules. Two extreme situations are given theoretical treatment. In both, monomer diffuses to the template surface where polymerization may occur if an adjacent site is suitable occupied. In addition the possibility of monomer desorption is included. In one model (``unrestricted'') the reaction is initiated on each template by the polymerization of two monomers and proceeds through the addition of monomer to growing ends or by the coupling of the growing chains. In the second (``restricted'') model the number of growing centers per template is zero or one and growth is achieved through monomer addition solely. In both cases the template is assumed to be of uniform size and either single stranded or, if double stranded, with an unwinding rate that is rapid in comparison with the polymerization processes. The number of template molecules is assumed constant during the synthesis, which disregards the function of new chains as sites for continued synthesis. All degradation mechanisms are omitted from consideration, which may restrict the present theories to low conversion processes. The pronounced differences between the unrestricted and restricted formulations in respect to kinetics and product molecular weight are elaborated and discussed in relation to recent experimental results on DNA synthesis in vitro. Finally, from known replication times in vivo, estimates of the rate parameters in the two models are derived.