DNA-histidine complex formation in isoelectric histidine buffers.

The free solution electrophoretic mobility of two DNA molecules of different molecular masses, 18 base pairs and 2686 base pairs, has been measured in isoelectric histidine buffers with and without added low-molecular-mass electrolytes. Extensive DNA-histidine complex formation is observed in isoelectric histidine buffer, as evidenced by distortion and splitting of the peaks in the electropherograms. Peak distortion and splitting can be decreased or eliminated by adding low-molecular-mass neutral salts to the solution, suggesting that the DNA-histidine complexes are stabilized by electrostatic interactions. The ability of various neutral salts to disrupt the DNA-histidine complexes depends on the molecular mass of the DNA and the concentration and type of added salt.