(A) Fluorescence dequenching as a function of inhibitor concentration. (B) Single-particle dwell-time distribution at pH 5.5 in the presence of 1 μM inhibitor. (C and D) Inhibition of DV2 VLP fusion by Alexa-555/3-110-22. (C) Fluorescence dequenching as a function of inhibitor concentration. Percent dequenching calculated with 100% as DiD dequenching with no added inhibitor and 0% as dequenching with no pH drop. Error bars are SEM, n = 3. (D). Single-particle binding intensity for Alexa-555/3-110-22 in the presence of varying molar ratios of underivatized 3-110-22 (none, 1:1, 1:10). Error bars: SEM; n = 373, 370, 382 for the three sets of measurements, respectively.