Figure 5. Individual tethers in whole cell measurements were supported by multiple α₄β₁/VCAM-1 complexes.

(A) Comparison of AFM force measurements acquired with extensive (whole cell measurement) and minimal (single molecule measurement) cell-substrate contact. L ^S is the length of tethers supported by a single α₄β₁/VCAM-1 complex as detected in single molecule measurements. In whole cell adhesion measurement shown, the cell detachment process involved the formation and breakage of at least 5 membrane tethers, labeled r ₁ through r ₅. Each tether is suppoted by multiple α₄β₁/VCAM-1 complexes. The lower and upper limits (L _l and L _u), and the average length (L ^C) of fourth tether (r ₄) are shown. (B) Comparison of average tether lengths from whole cell measurements (L ^C) and tether lengths from single molecule measurements (L ^S). (C) Estimates of the number of α₄β₁/VCAM-1 complexes in a tether generated during the whole cell measurements. Black and red plots provide the range for the number of α₄β₁/VCAM-1 complexes in a single tether for untreated and MCP-1 stimulated cells, respectively. The superscripts unt and MCP associated with N (number of complexes) and L (tether length) designate untreated and MCP-1-stimulated cells, respectively.