Studies on self association of proteins. Self assocition of alpha-chymotrypsin at its isoelectric point in buffer solutions of ionic strength 0.1.

The self-association of a-chymotrypsin at its
isoelectric point has been studied in two buffer solutions of
p (ionic strength) = 0.1: phosphate buffer (pH 6.9) and
Tris buffer (pH 8.3). The weight-average molecular weight
(by the Archibald method) and sedimentation coefficient
were determined as a function of protein concentration. The
molecular weights measured were the same in both the buffers. In sedimentation velocity experiments unimodal
peaks were obtained at all the protein concentrations. The
molecular weight data could be fitted to a nonideal indefinite
self-association equilibrium or a hexamerization equilibrium
with all the intermediate species coexisting. The
sedimentation data could be fitted to an octamerization
equilibrium.