Distribution of ions around DNA, probed by energy transfer

摘要: Abstract Measurements of the effect DNA on rates bimolecular energy transfer between ions provide a direct indication how cations cluster in regions near and anions are repelled from same regions. Energy luminescent lanthanide (in "rapid-diffusion" limit) probes collision frequencies that dependent equilibrium spatial distributions ions. The addition 1 mM (phosphate) to 2 salt solution increases overall frequency monovalent by factor 6 +/- 1.5; it divalent-monovalent cation 29 3; decreases divalent cation-monovalent anion 0.24 0.03. Comparisons made with changes predicted several different theoretical descriptions ion distributions. closest agreement experimental results for at is obtained static accessibility-modified discrete charge calculation, based detailed molecular model B-DNA. At high concentration (10 mM), best numerical solutions Poisson-Boltzmann equation "soft-rod" DNA. calculations "hard-rod" greatly overestimate effects frequencies, as does calculation counterion-condensation theory.