Gel electrophoresis of reacting macromolecules. Rate-limited self-association

Prompted by experimental sodium dodecyl sulfate-gradient polyacrylamide gel electrophoresis (PAGE) patterns of an oligomerizing 73-residue peptide, PAGE and gradient PAGE patterns were simulated numerically for two rate-limited, reversible self-associating systems, viz., monomer-dimer and monomer-dimer-tetramer interactions. A wide range of values for rate constants and other relevant parameters was examined. The cardinal result for interactions with half-times comparable to the time of electrophoresis is that the number of peaks in the pattern can exceed the number of interacting species. Since peaks of intermediate migration velocities are composed of interconverting monomer and oligomers, molecular weights corresponding to individual species cannot be assigned to them.