Determination of pore/protein size via electrophoresis and slit sieve model

Abstract

We used electrophoresis for three purposes: (i) estimation of the mean pore size of
polyacrylamide gels via measuring electrophoretic mobility of globular proteins of
known sizes in combination with simple sieve (cylindrical and slit) models; (ii) determination
of the average size of protein molecules (native or denatured) by the use of the
same models; (iii) monitoring the changes in molecular dimensions of proteins in the
course of their denaturation. Both models yield results that are in good agreement with
those found via the more elaborate techniques (considering the principal differences
involved). The approach provides a direct and convenient way of monitoring the variations
in protein sizes during the course of their denaturation in gels having a gradient
of denaturants, and possibly the number of conformational states involved in the process,
a facet that is quite unique and useful. The simpler slit model seems to yield
better results in the latter case and is moreover supported by the recently reported
data on electrophoresis of DNA molecules through the 1 mm slits of a microbrush
matrix made of micropillars arranged in a hexagonal lattice.