Book of Abstracts: Albany 2003
June 17-21 2003
Electrostatic Shielding of DNA in Tris and Diethylmalonate Buffers, with and without Added Salt
The free solution mobility of a 20-bp double-stranded DNA oligomer has been measured in diethylmalonate (DM) and Tris acetate buffer solutions, with and without added NaCl or TrisCl, using capillary electrophoresis. The free solution mobility of DNA decreases linearly with the logarithm of ionic strength when the ionic strength is increased by increasing the buffer concentration. The mobility also decreases linearly with the logarithm of ionic strength when Na+ ions are added to NaDM buffer or Tris+ ions are added to TrisDM buffer. Non-linear effects are observed when the counterion in the added salt differs from the counterion in the buffer. The dependence of the mobility on ionic strength in all buffer and buffer/salt solutions can be predicted within 20%, using no adjustable parameters, by the Manning theory of electrophoresis. The results suggest that the electrostatic shielding effects are determined not only by the concentrations of the various ions in the solution, but also by their equivalent conductivities (or transference numbers).
Nancy C. Stellwagen*
Department of Biochemistry