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. 2020 Aug 26;53(9):1802–1810. doi: 10.1021/acs.accounts.0c00212

Figure 2.

Figure 2

Ion condensation around nucleic acid and counterion release upon protein–nucleic acid association. (A) Impact of ion condensation on ionic diffusion. Blue and red spheres represent cations and anions, respectively. The apparent diffusion coefficient, Dapp, for cations is given by a population average of the diffusion coefficients Df for the free ions and Db for the bound ions within the ion atmosphere. The Dapp data for NH4+ ions measured at various concentrations of a 15-bp DNA duplex are shown.50 The diffusion coefficients Df and Db can be determined from Dapp data at various concentrations of the nucleic acid. (B) NMR diffusion data showing the direct evidence of counterion release upon the Antp homeodomain–DNA association. Adapted from Pletka et al.50 with permission from Wiley-VCH.