Effect of phosphatidylcholine vesicle size on chirality induction and chiral discrimination

Abstract

The effect of the size of phosphatidylcholine (PC) vesicles on the induction of chirality and chiral discrimination was examined. Three kinds of vesicles formed with l-dimyristoyl, l-dipalmitoyl, or egg yolk PCs induced circular dichroisms (CDs) with the sign and intensity of the Cotton effect different from those of monomeric PCs. The CD intensity of the vesicles increased with a decrease in the vesicle size. Furthermore, the helicity of heterohelicene derivatives in a rapid equilibrium between right-handed (P) and left-handed (M) enantiomers was biased toward the M enantiomer side in l-PC vesicles, implying chiral discrimination by the vesicles. The extent of the bias toward the M enantiomer increased with an increase in vesicle size. Both the chirality induction and chiral discrimination were enhanced in a low-fluidity gel phase in comparison with those in a high-fluidity liquid-crystalline phase for every kind of vesicle of every size examined.

Bis-pyrene probes of foldamer conformation in solution and in phospholipid bilayers

“…Reports by Nakagawa and co-workers indicate that phospholipid chirality can influence the conformational equilibria of embedded molecules; helicenes that rapidly interconvert between M and P helical conformations were found to deracemize in phospholipid bilayers. 33 , 34 Although there are no reports of the deracemization of achiral peptides in phospholipid bilayers, micelles composed of N -dodecylproline were used to induce a h.e . of at least 33% in an achiral 3 10 -helical Aib octamer.…”

A Synthetic Mirror Image of Kalata B1 Reveals that Cyclotide Activity Is Independent of a Protein Receptor

“…The chirality of membrane phospholipids is normally considered weak, but the results here show that it can still modulate activity. Natural phospholipids create a chiral environment, [36,37] and chiral discrimination has been demonstrated for some molecules. [37–39] All phospholipids have a chiral center in their glycerol skeleton immediately adjacent to the hydrophobic acyl chains; this suggests that kalata B1 inserts near to, or in, the hydrophobic region of lipid bilayers.…”

“…Natural phospholipids create a chiral environment, [36,37] and chiral discrimination has been demonstrated for some molecules. [37–39] All phospholipids have a chiral center in their glycerol skeleton immediately adjacent to the hydrophobic acyl chains; this suggests that kalata B1 inserts near to, or in, the hydrophobic region of lipid bilayers. Hence, we suggest that the activity of kalata B1 does not require enantiomeric specificity for a protein receptor but depends on the affinity for lipid membranes, and is governed by specific interactions with PE headgroups and by hydrophobic interactions that are privileged for the native peptide compared with the D isomer.…”

The posssible role of enantiodiscrimination in bilirubin toxicity

“…20 Liposomes of DMPC, that, among the phosphocholines we have investigated, feature the optimal packing of saturated chains, showed the best recognition capabilities, moreover at physiological pH the sites of binding of bilirubin within DMPC liposomes were shown to protect the pigment from bleaching. This finding supports the hypothesis, reported previously, 21 of a site of association of monoanionic bilirubin in the hydrophobic region of the aggregates.…”