INFLUENCE OF COLUMN TEMPERATURE AND PHYSICOCHEMICAL PROPERTIES ON THEELECTROPHORETIC BEHAVIOR OF POLYGLYCINE PEPTIDES IN FREE-SOLUTION CAPILLARY ELECTROPHORESIS

The changes in electromigration time with column temperature for polyg lycine peptides were found to be due to temperature-induced viscosity changes of water. A quantitative linear relationship between the logar ithm of migration times (log t(m)) and the reciprocal of column temper ature (1/T) was derived under a constant electric field strength. The slope of the plot of log t(m) vs. 1/T was directly related to the acti vation energy of diffusion (AED). It was also found that the effect of column temperature on migration times is much more significant under constant-voltage than under constant-current operation. Polyglycine pe ptides differing only in size were chosen as model molecules for the t est of the mobility model. Systematic correlations between t(m) and th e number of glycine amino acids (n) were made. A linear relationship b etween t(m) and n0.5 was found for polyglycine peptides under differen t operating modes. It was observed that the extrapolations of the line ar relationships between t(m) and n0.5 with different column temperatu res at constant voltage or with different applied currents at constant temperature cross each other at the same point. The parameters m0 and m1 in the equation t(m) = m0 + m1n0.5 were correlated with the column temperature and the operating current. The activation energy of diffu sion was also obtained for the plot of log m1 versus 1/T at constant v oltage. Linear relationships between m0 and m1 were found for these pe ptides which thus result in the intersection point in the plots of t(m ) vs. n0.5.