Chiroptical rhythmicity, part 3: implications on the activity of the functional cell-surface receptor model

The effect of ligand-induced rhythmical structural changes of the artificia l receptor 1 on its capacity to mediate ion transport across lipid bilayer membranes was studied. The changes of the intravesicular pH of egg yolk pho sphatidylcholine-small unilamellar vesicles (EYPC-SUVs) after application o f a transmembrane proton gradient were measured by double-channel fluoresce nce kinetics in the presence of 1 at various concentrations of the extraves icular ligand L-His. Comparison with negative control experiments using D-H is indicated that increasing concentrations of L-His affect the activity of 1 in a presumably rhythmical manner. Compared to the extent of structural rhythmicity, the functional rhythmicity of 1 appeared, however, less signif icant. The need for refined assay systems to fully delineate the importance of rhythmical activity of 1 with respect to biological rhythmicity is brie fly discussed. (C) 2000 Elsevier Science B.V. All rights reserved.