Band width measurement in automated gel electrophoresis apparatus: DNA dispersion in a discontinuous system and in a single buffer.

Recent commercial introduction of automated gel electrophoresis apparatus allows for band width measurements during electrophoresis and therefore promises to open up the exploitation of band width and shape for the physical characterization of charged macromolecules in the same manner in which to date quantitative gel electrophoresis had exploited electrophoretic mobility at multiple gel concentrations. The measurements demonstrate decreased band width and therefore increased resolving power for a discontinuous buffer system compared to Tris-borate EDTA buffer. The dispersion coefficients (D' = (sigma 2-sigma 2o)/t) of homogeneous DNA components appear to decrease with gel concentration when either the field strength or the DNA length is small, and increase with gel concentration when these are large. This contrasting response of D' to increasing gel concentration is presumably due to DNA stretching, which increases in proportion to DNA length and field strength, and to the progressive orientation of agarose with increasing field strength.