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

The changes in electromigration time with column temperature for polyglycine peptides were found to be due to temperature-induced viscosity changes of water. A quantitative linear relationship between the logarithm of migration times (log t(m)) and the reciprocal of column temperature (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 activation 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 peptides differing only in size were chosen as model molecules for the test of the mobility model. Systematic correlations between t(m) and the number of glycine amino acids (n) were made. A linear relationship between t(m) and n0.5 was found for polyglycine peptides under different operating modes. It was observed that the extrapolations of the linear relationships between t(m) and n0.5 with different column temperatures 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 diffusion was also obtained for the plot of log m1 versus 1/T at constant voltage. Linear relationships between m0 and m1 were found for these peptides which thus result in the intersection point in the plots of t(m) vs. n0.5