ELECTRIC FIELD STRENGTH EFFECT ON THE CAPILLARY ELECTROPHORESIS CHARACTERISTICS IN LINEAR POLYACRYLAMIDE

Capillary electrophoresis of DNA fragments(from 80 bp to 584 bp) in replaceable linear polyacrylamide(LPA) solution was investigated using laser induced fluorescence detection.The fluorescence dye was Ethidium Bromide(EB).When the electric field strength was changed from 100 V/cm to 375 V/cm,the variation curves about current,mobility,signal intensity,width at half-height and the resolution were obtained.The nonlinearity parameter of experimental current and electric field strength are 0.999 44 and 0.998 76 with 4%LPA and 6%LPA respectively,which shows good linear relationships.The mobility is varied as a complex function of fragment size and electric field; the electrophoresis mobility depends on the applied electric field strength,the concentration of gel matrix and the size of the fragment.The electric field strength has effect on the signal intensity little,but the gel matrix concentration affects the peak width so it affects the signal intensity.The broadening is less and signal intensity is higher with 4% LPA than that with 6% LPA.It shows 4% LPA is more suitable for separating DNA samples which the fragment size ≤600 bp.The electric field strength affects resolution complicatedly; the resolution cannot be increased if only increasing the electric field strength.In order to increase the resolution,the optimum electric field strengths are 125 V/cm.The analysis above is very useful for experiment.