FIGURE 6.

Propofol slows modification of L240C and has no effect on N238C and E242C modification. A, shown is an example of a rate experiment at L240C where modification by PCMBS⁻ potentiates the proton-induced current; pH₂₀-induced currents were measured before and after successive applications of 100 μm PCMBS⁻ (top) or 200 μm PCMBS + 100 μm propofol (below) in pH 7.6 buffer. PCMBS⁻ exposure time (s) is indicated on top of the arrows. B, current amplitudes were normalized to maximal potentiation by PCMBS⁻ and plotted against cumulative PCMBS exposure time (s) weighted by concentration of PCMBS⁻ (m) and fit with single exponential functions as described under “Materials and Methods.” B–E, shown are rates of modification of L240C (B and C), N238C (D), and E242C (E) in the absence (○) or presence (■) of 100 μm propofol. B and C, propofol significantly slowed modification of L240C by PCMBS⁻ and MTSEA. D and E, propofol had no effects on modification of N238C and E242C by MMTS or MTSEA, respectively. Data points are the mean ± S.E. from ≥3 experiments. Single exponential fits of the data are shown as dotted (Control) and solid (+Propofol) lines. Second order rate constants are reported in Table 2.