SELECTIVITY OF THE SEPARATION OF DNA FRAGMENTS BY CAPILLARY ZONE ELECTROPHORESIS IN LOW-MELTING-POINT AGAROSE SOL

The properties of solutions of low-melting-point agarose for the separ ation of DNA fragments were investigated as a function of temperature and applied voltage. Giddings et al.'s definition of the selectivity o f the separation according to molecular size, S = \(d ln u)/(d In p)\, where u is the electrophoretic mobility and p the number of base pair s, was adopted as a suitable phenomenological description of the capab ility of the system to separate DNA fragments. It was found that the s electivity of separation in 1% agarose has its maximum at about 600 ba se pairs, decreases with increasing applied voltage and is a complex f unction of temperature. No decrease in selectivity was observed even a t temperatures above the melting point. The high selectivity of agaros e at these temperatures is probably evidence for the positive effect o f conformational entropy of DNA molecules. A development of an apparat us for thermostating the capillary within the range 10-70-degrees-C th at allowed the measurements to be performed is reported.