Adsorption of DNA to mica mediated by divalent counterions: a theoretical and experimental study.

摘要: The adsorption of DNA molecules onto a flat mica surface is necessary step to perform atomic force microscopy studies conformation and observe DNA-protein interactions in physiological environment. However, the phenomenon that pulls still not understood. This crucial issue because DNA/surface could affect biological functions. In this paper we develop model can explain mechanism mica. suggests attraction due sharing counterions. correlations between divalent counterions on both negatively charged generate net whereas monovalent are ineffective attraction. binding then dependent fractional densities cations, which compete for neutralizations. addition, be enhanced when has been pretreated by transition metal cations (Ni2+, Zn2+). Mica pretreatment simultaneously enhances reduces repulsive contribution electrical double-layer force. We also end-to-end distance measurement chains study strength. strength appears constant fixed density at low ionic (I < 0.1 M) as predicted model. higher strength, weakened screening effect ions. Then, some equations were derived describe polyelectrolyte surface. electrostatic particularly effective if have nearly same charge density. characteristic success performing single molecule observation AFM. how reversible obtained with