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. Author manuscript; available in PMC: 2019 Oct 31.
Published in final edited form as: J Am Chem Soc. 2018 Oct 16;140(43):14224–14234. doi: 10.1021/jacs.8b08153

Figure 2.

Figure 2.

(a) Single-channel I-V curves of γ-HL at different pH in asymmetrical KCl solutions (3 M vs 1 M KCl, cis vs trans) for measurement of ion selectivity of the protein channel. Note in acid conditions (pH 4–6), the protein exhibits voltage-induced gating at positive potentials (indicated by ~0 current at > 70 mV). The sudden drop in current at pH 4 to 6 is due to voltage gating of the channel. Potential difference between the two Ag/AgCl reference electrodes has been accounted for. (b) Expanded view of the I-V curves near 0 pA. (c) I-t traces showing the open-channel current at −50 mV from pH 4 to 8 in 1 M KCl, 20 mM HOAc/KOAc or PB, at 20.0 °C. I-t traces were sampled at 50 kHz and filtered at 10 kHz using a low-pass Bessel filter. (d) All-point histograms of the open-channel current during the 2 s period (100,000 data points) at each pH as shown in (c).