FIG. 1.

Schematic of the instrument used to measure the micromechanics and kinetics properties of single molecular bonds between an infectious HIV-1 virion and individual cell receptors on a live host cell. (A) Schematic of the detection components of the MFP and the flexible cantilever placed just above a host cell. (B) Pseudovirus particles are cross-linked to a triangular cantilever, which is delicately brought into contact with a cell displaying either major receptor CD4, coreceptor CCR5 (or CXCR4), or both on its surface. (C) Typical force deflection traces recorded during the retraction of the cantilever. Ruptures of virion-cell bonds are marked by arrows. (D) Probability of formation of bonds between a virion and a host cell. The distribution displays Poisson characteristics (see text). (Inset graph) Probability of formation of bonds when only force deflection traces displaying at least one bond adhesion are analyzed. The time of contact between cell and virion was ∼1 μs.