FIG. 1.

Kinetics of retrovirus adsorption. lacZ retrovirus with Polybrene was added either to an empty plate (open circles) or to a plate confluent with NIH 3T3 fibroblasts (solid circles). Adsorption was monitored with an ELISA that measured the amount of p30 remaining in the medium. The diffusion coefficient was calculated by fitting the experimental data to the Valentine and Allison equation (line) by nonlinear regression analysis. The best-fit value, D = 1.74 × 10⁻⁸ cm²/s.