Concentrations of phenylalanine and tyrosine in plasma and brain of rats treated with phenylalanine loads.

one or more adenosine triphosphatase units in discrete assemblies (Ernster et al., 1973). If proved, this finding would present a very serious challenge to the classical chemiosmotic view, which is necessarily based on a generalized rather than a specific association of the oxidation and phosphorylation processes. In contrast, the presence of assemblies is in no way damaging to the p-zone interpretation. The zones of electrostatic potential could exist as a series of discontinuous ‘patches’ on the membrane surface, as shown in Fig. 2. The mosaic structure of membranes would suggest that this is more likely than the continuous ‘strip’ p-zone shown earlier (Archbold et ul., 1975c, Fig. 1). These ‘patches’ would reflect, topographically, the fixed-charge pattern of the membrane which, in turn, would be related to the sites of proton release from individual transport chains. If this view is correct we shall be dealing with electron-transport-chain-Apkadenosine triphosphatase assemblies of greater complexity than the assemblies already proposed.