Fig. 3
From: A synthetic metabolic network for physicochemical homeostasis
Generation of ATP and pH changes. The internal composition of the vesicles at the start of the experiment is given in Fig. 2a (enzymes) and Table 2 (ions, metabolites) and the preparation of vesicles is given in protocol A1, unless specified otherwise. a Schematic representation of PercevalHR; modification of cartoon in ref. 32. b Effect of FCCP on the fluorescence readout of PercevalHR (protocol A1); the ratio of the fluorescence peaks at 500 nm and 430 nm is shown. In the absence of FCCP, the fluorescence readout declines 30 min after addition of 10 mM arginine (at t = 0) due to changes in the internal pH (addition of FCCP after 2 h increases the signal, indicated by the black arrow). The fluorescence signal is constant for several hours in the presence of 10 µM FCCP (n = 2). c External pH change (protocol B5) of arginine-metabolizing vesicles in outside medium with 10 mM KPi pH 7.0 plus 355 mM KCl. The ATP production was started by adding 5 mM arginine at t = 0. d Schematic representation of the pH effects caused by ammonia and carbon dioxide diffusion. e Internal pH change (protocol B4) of arginine-metabolizing vesicles with either 50 mM (blue trace) or 15 mM KPi plus 40 mM KCl, pH 7.0 on the inside (protocol A2; black trace). Five millimolar arginine was added at t = 0 (n = 2)
