Table 1.

Model parameters

Parameter	Definition	Value	Reference
R	Leukocyte radius, μm	3.75	43
nL	No. of P-selectin glycoprotein ligand-1 molecules per cell	15,000	33
nR	P-selectin (receptor) site density, receptors/μm2	15 or 150	47
Lb0	Equilibrium bond length, μm	0.1	18
kf0	Unstressed on rate, s−1	1	31
kf0	Unstressed off rate, s−1	1	31
σb	Bond spring constant, dyn/cm	1	12
σts	Transition state spring constant, dyn/cm	0.99	12
σm	Microvillus spring constant, pN/μm	43	39
σm′	Effective viscosity of tether, pN·s·μm−1	11	39
Eh	Membrane stiffness, dyn/cm	1.2 or 3.0
γ	Shear rate, s−1	10–800
μ	Fluid viscosity, cP	0.8
ρ	Fluid density, g/ml	1
T	Temperature, K	310
xβ	Reactive compliance, Å	0.3	5
Lm0	Equilibrium length of microvillus, μm	0.35	39
nm	No. of microvilli per cell	252	9
Fm0	Threshold microvillus force, pN	45	5
k1rup	Failure rate along the low impedance pathway, s−1	12	16
k2rup	Failure rate along the high impedance pathway, s−1	1	6
ΔE21	Difference in energy between the two bound states, kBT	5 kBT	16
f12	Span of force for which the switch between the two states occurs, pN	6	16

k_B, Boltzmann constant.