Several parameters are likely to play key roles in governing the thermodynamics and kinetics of the FGF2 membrane translocation process. The faster kinetics observed in living cells ), compared to in vitro reconstitution experiments using purified components , can be attributed to fundamental differences between the two experimental systems. Notably, the absence of auxiliary components in synthetic vesicles such as the Na,K ATPase and Tec kinase. In addition, as a surrogate for the authentic GPI-anchored heparan sulfate proteoglycan GPC1, soluble heparin molecules containing FGF2 binding sites have been used in in vitro experiments. All of these factors may have an impact, slowing down the kinetics and efficiency of FGF2 membrane translocation observed in vitro compared to living cells.