PEPTIDE STABILITY IN SOLIDS AND SOLUTIONS

A discussion of the factors influencing peptide stability illustrates the challenges of formulation and shelf-life prediction which face bio technologists. The activation energies of peptide degradation vary wit h pH and moisture content. Peptide degradation rates are influenced by both buffer type and concentration. Lyophilization results in an incr ease in buffer concentration which also enhances peptide degradation i n low-moisture solids. Small peptides have degradation rates that depe nd upon water activity rather than upon mobility limitations associate d with the state of the system. The pH-rate profiles for peptide degra dation in solution and solids are quite different. Dehydration and par tial rehydration change the pH of reduced-moisture solids, which chang e both the rates and mechanisms of degradation. The properties of the peptide and the system as well as potential interactions between the t wo need to be identified to maximize peptide stability. In addition, s olution data cannot be used to predict the shelf Life of reduced-moist ure solids.