Intramolecular Transfer of Excitation Energy, Complexation with Metal Ions, and Interactions with Liposomes of Cyclo [tryptophyl‐sarcosyl‐sarcosyl‐N^ϵ‐dansyllysyl‐prolyl]

Abstract

SummaryA cyclic pentapeptide containing an energy donor group and an energy acceptor group within the molecule, cyclo [Trp-Sar-Sar-Lys (DNS) Introduction. -To clarify the relationship between structure, conformation, and various functions of peptides, synthetic cyclic peptides have been used as models and their conformations and functions have been studied by spectroscopic methods [ 1-41. For example, information about the mechanism of ionophoric action, was gained by X-ray diffraction, circular dichroism (CD.), and nuclear magnetic resonance (NMR.) spectroscopy [5-131. From our investigations with a series of cyclic octapeptides [ 141, we have found that the conformation is strongly solventdependent. Therefore, to elucidate the mechanism of the action of peptides on membranes, it is necessary to carry out the conformational analyses in lipid membranes. Some studies of peptides in liposomes and micelles have already been carried out by CD. and NMR. spectroscopy [15] [16]. However, in these investigations the probe concentrations employed were very high, possibly producing artefacts due to peptide aggregation and membrane perturbation. On the other hand, fluorescence methods are effective at low probe concentrations, thus avoiding such difficulties. We therefore attempted to synthesize the cyclic pentapeptide cyclo [Trp-Sar-Sar-Lys (Z)-Pro] containing a Trp-residue as a fluorescent probe,-