Actual concentration of soluble SDF-1α in the bottom chamber of a standard Transwell assay.

Transwells were coated with Fn at 5 μg/mL and washed, and the indicated concentrations of ¹²⁵I–SDF-1α were added to the bottom. After 1 hour, aliquots from the bottom chambers were counted in a γ counter and were compared to the known specific activity to determine the actual soluble SDF-1α concentration. The right-hand Y-axis represents the percentage input remaining soluble. Values represent mean of 3 trials ±1 SD.