FIGURE 1.

Single molecule microscopy of K^d-peptide P1 complexes on L-K^d cells. A, ⁵¹Cr-labeled L-K^d cells were pulsed with the indicated concentrations of PbCS (circles), PbCS(ABA) (squares), peptide P1 (triangles), or peptide P2 (crosses) and incubated with cloned S14 CTL (CTL/target = 3/1). After 4 h, the specific lysis was determined from released ⁵¹Cr. One representative experiment out of three is shown. B, image of K^d-peptide P1 complexes on the lower glass-adhered membrane of two L-K^d cells (contoured by dashed lines) within an illuminated circular region of 20 μm. Single complexes exhibit diffraction-limited spots, like the one encircled. The scale bar is 5 μm. C, single molecule trace displaying typical single-step photobleaching. D-F, typical trajectories of an immobile/confined complex (D), a mobile one (E), and one undergoing a transition from an immobile/confined to a mobile state (F). The pixel size is 225 nm.