Book of Abstracts: Albany 2003
June 17-21 2003
Topics in the Polyelectrolyte Theory of DNA
Over the last few years, counterion condensation theory has been extended in various directions that impact on the polyelectrolyte properties of DNA. Some of our conclusions follow:
The 14 arginine contacts that comprise the fundamental binding motif of DNA in the nucleosome core particle are all that are needed to stabilize the bending of DNA on the superhelical ramp provided by the histone octamer. For clarity, we note that more is certainly involved in the sequence-dependent positioning of nucleosome DNA, but the 5 % phosphate charge neutralization by the arginines is enough to stabilize the overall superhelical bending.
Asymmetric counterion fluctuations can bend free DNA and may make a significant contribution to the collection of thermal fluctuations that determine the DNA persistence length.
Loose clusters of DNA can form in solution due to an effective attraction mediated by condensed counterions. The counterions need not be multivalent. In fact, the counterion-mediated attraction in question becomes weaker if multivalent counterions are substituted for monovalent ones. This property of DNA is shared by other polyelectrolyte assemblies. A body of experimental evidence is available to support the existence of clustering of like-charged polyelectrolytes in the presence of ordinary monovalent cations.