Quantitative evaluation of the kinetics of lipid probe redistribution between fusing cells

Redistribution of a fluorescent lipid probe in a cell-fusion system was analyzed by solving numerically the time-dependent diffusion equations on two spheres connected by a cylindrical pore. The half-times of the process were calculated for different values of the diffusion coefficient Dp for a lipid probe in the pore. It was shown that the kinetics of the redistribution was relatively insensitive to the length and radius of the pore, whereas Dp significantly affected the redistribution rate constant. Based on the results of the numerical analysis, the minimal lag time between the start of the process and the appearance of experimentally measurable quantities of the probe in the acceptor cell was roughly estimated.