Chiroptical rhythmicity, Part 2: Evidence for signal transduction by stereoselective ion pair formation at the...

The initiation mechanism of chiroptical rhythmicity, a novel chiroptical phenomenon (Ghebremariam and Matile preceding contribution), was investigated by exploring the functionality of five structural analogs of the inducing L-His ligand. Disappearnace of chiroptical rhythmicity with L-His methyl esters as well as with D-His implied that stereoselective ion pair formation between carboxylate anion of L-His bound at the membrane/water interface and ammonium cations of phosphatidylcholine is essential for signal transduction to the hydrophobic core of the membrane. It was further shown that "H" aggregation of the asymmetric septi(p-phenylene) chromophore induced by multivalent L-His (i.e., poly-L-His) exceeds the extent required for chiroptical rhythmicity by far and ultimately results in the formation of achiral herringbone lattices.