Figure 3.

Cold-arrested fusion pores were closed by peptides that block 6HB formation but not by other inhibitors of fusion. The time at which the temperature was dropped to 4°C to block pore growth is marked by downward arrows in each panel. The fluorescence intensities of target cells (HeLaT4⁺, solid lines) were used to calculate pore permeability from Eq. (2) (⋄). Once pore growth was blocked at 4°C, inhibitory agents were added (indicated by ▵), allowed to bind for ∼5 min, and the temperature was then raised back to 37°C (upward arrows). The inhibitors were (A) 47 nM C34 peptide, (B) 4 μM N36 peptide, (C) 0.4 μg/ml T22 peptide, and (D) 0.2 mg/ml LPC.