Homochiral oligomerization of L-histidine in the presence of liposome membranes

The astrochemical evolutionary traits of phospholipid membrane homochirality

Compartmentalization is crucial for the evolution of life. Present-day phospholipid membranes exhibit a high level of complexity and species-dependent homochirality, the so-called lipid divide. It is possible that less stable, yet more dynamic systems, promoting out-of-equilibrium environments, facilitated the evolution of life at its early stages. The composition of the preceding primitive membranes and the evolutionary route towards complexity and homochirality remain unexplained. Organics-rich carbonaceous chondrites are evidence of the ample diversity of interstellar chemistry, which may have enriched the prebiotic milieu on early Earth. This Review evaluates the detections of simple amphiphiles - likely ancestors of membrane phospholipids - in extraterrestrial samples and analogues, along with potential pathways to form primitive compartments on primeval Earth. The chiroptical properties of the chiral backbones of phospholipids provide a guide for future investigations into the origins of phospholipid membrane homochirality. We highlight a plausible common pathway towards homochirality of lipids, amino acids, and sugars starting from enantioenriched monomers. Finally, given their high recalcitrance and resistance to degradation, lipids are among the best candidate biomarkers in exobiology.

Possible Roles of Amphiphilic Molecules in the Origin of Biological Homochirality

A review. The question of homochirality is an intriguing problem in the field of chemistry, and is deeply related to the origin of life. Though amphiphiles and their supramolecular assembly have attracted less attention compared to biomacromolecules such as RNA and proteins, the lipid world hypothesis sheds new light on the origin of life. This review describes how amphiphilic molecules are possibly involved in the scenario of homochirality. Some prebiotic conditions relevant to amphiphilic molecules will also be described. It could be said that the chiral properties of amphiphilic molecules have various interesting features such as compositional information, spontaneous formation, the ability to exchange components, fission and fusion, adsorption, and permeation. This review aims to clarify the roles of amphiphiles regarding homochirality, and to determine what kinds of physical properties of amphiphilic molecules could have played a role in the scenario of homochirality.

Vesicles Constructed with Chiral Amphiphilic Oxacalix[2]arene[2]triazine Derivatives for Enantioselective Recognition of Organic Anions

Chiral amphiphilic oxacalix[2]arene[2]triazine derivatives 1-3 bearing l-prolinol moieties were synthesized. The self-assembly behavior of the chiral macrocyclic amphiphiles was investigated. SEM, TEM, and DLS measurements demonstrated that 1 formed stable vesicles (size of ∼90 nm), whereas 2 and 3 formed micelles. As monitored by DLS, vesicles composed of 1 showed selective response to the chiral anions (2S, 3S)-2,3-dihydroxysuccinate (d-tartrate), S-mandelate and S-(+)-camphorsulfonate over their enantiomers. DFT calculations revealed that the enantioselectivity arises from cooperative anion-π interactions and hydrogen bonding between the chiral electron-deficient cavity and the organic anions.

Effect of Boundary Edge in DOPC/DPPC/Cholesterol Liposomes on Acceleration of l-Histidine Preferential Adsorption

In order to investigate the interaction of hydrophilic molecules with liposomal membranes, we employed 1-(4-(trimethylamino)phenyl)-6-phenyl-1,3,5-hexatriene and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(5-dimethylamino-1-naphthalenesulfonyl) as fluorescent probes to monitor the surface regions of the membrane, and the results for various liposomes were plotted in correlation diagrams. According to the formation of a variety of phase states, different tendencies of decreasing surface hydrophobicity were observed in the liposomes that were modified with high concentrations of cholesterol or in the liposomes that were composed of ternary components. These liposomes, with hydrophobic surfaces, also showed preferential adsorption of l-histidine (l-His), and the hydrophobicity of the liposomal membrane at the surface changed during l-His adsorption regardless of the initial liposomal properties. Furthermore, we revealed that accelerated adsorption of l-His and preferential binding was induced in ternary liposomes forming boundaries between two separate phases.