Sizing the pore of the volume-sensitive anion channel by differential polymer partitioning

Partitioning of ethylene glycol and its polymeric forms into the pore of the volume-sensitive outwardly rectifying (VSOR) anion channel was studied to assess the pore size. Polyethylene glycol (PEG) PEG 200–300 (Rh=0.27−−0.53 nm) effectively suppressed the single-channel currents, whereas PEG 400–4000 (Rh=0.62−−1.91 nm) had little or no effect. Since all the molecules tested effectively decreased electric conductivity of the bulk solution, the observed differential effects between PEG 200–300 and PEG 400–4000 on the VSOR single-channel current are due to their limited partitioning into the channel lumen. The cut-off radius of the VSOR channel pore was assessed to be 0.63 nm.