Figure 5.

The increased kinetics of L-selectin transient tether dissociation at increased wall shear stress and force on the tether bond. The k_off values at different shear stresses were determined from neutrophil first order dissociation rate constants measured as in Fig. 4. The thick line is the fit of Bell’s equation to all experimental points: k_off = k°_off exp (σF_b/kT), where k°_off is the unstressed k_off, σ is the separation between receptor and ligand that weakens the bond enough to increase k_off by e, k is Boltzmann’s constant, and T is the absolute temperature (29). The thin line is the fit to an Hookean spring model (13, 30): k_off = k°_off exp (f_κF_b/2κkT), where κ is the spring constant for the tether bond and f_κ is the fraction of the bond spring constant devoted to bond dissociation, also known as the fractional spring slippage (30). This fit yields k°_off = 9.7 ± 0.66 sec⁻¹, κ/f_κ = 6.31 ± 0.96 N/m. Data was fit by using the program igor (WaveMetrics, Lake Oswego, OR).