In-gel fluorescence analysis of the time-course of metabolic labeling of COS-7 cells with probes C15AlkOH (2, A), C15AlkOP (5, B), C15AlkOPP (2, C), and C15AlkMPP (4, D) incubated for 6, 12, 24, or 36 h. Probes are added at 10 μM final concentrations for the times indicated in the presence or absence of 10 μM of lovastatin pre-treated for 6 h.