Fig. 6. H₂O₂ concentration-dependent horse cyt c-catalysed ABTS oxidation reaction parameters in the presence of DOPC/DOPE/CL LUVs containing different CL% or DOPG LUVs (circles, solid line) and in the absence of LUVs (squares, broken lines). (A, C, and E) Plots of observed reaction rate k_obs against H₂O₂ concentration and (B, D, and F) plots of inverse of reaction rate against inverse of H₂O₂ concentration: (A and B) in the presence of DOPG LUVs (lipid, 0.5 mM) at bulk pH 6.8 and in the absence of LUVs at pH 5.3 (purple); (C and D) in the presence of DOPC/DOPE/TOCL LUVs (DOPC : DOPE = 2 : 1, TOCL = 10% (blue), 25% (red) and 50% (green) of total lipids; TOCL = 0.25 mM) at bulk pH 6.8 and in the absence of LUVs at pH 4.3 (blue), 3.9 (red), and 3.6 (green); (E and F) in the presence of DOPC/DOPE/TMCL LUVs (DOPC : DOPE = 2 : 1, TMCL = 10% (blue), 25% (red) and 50% (green) of total lipid; TMCL = 0.25 mM) at bulk pH 6.8 and in the absence of LUVs at pH 4.3 (blue), 3.9 (red), and 3.6 (green). The plots in the absence of LUVs at pH 6.8 are represented in black for comparison in (A–F). The initial reaction rate was obtained by spectrophotometric measurement of ABTS oxidation. The oxidation rate of ABTS in (A, C, and E) agrees with the equation for a bimolecular reaction: k_obs = k₁[cyt c][H₂O₂] = k_obs[cyt c] (k_obs = k₁[H₂O₂]). Reaction conditions: cyt c concentration, 5 μM; H₂O₂ concentration, 0–4 mM; ABTS concentration, 40 μM; 25 °C.