title: Oligopeptides with homochiral sequences generated from racemic precursors that spontaneously separate into enantiomorphous two-dimensional crystalline domains on water surface.
abstract: The feasibility of generating oligopeptides with homochiral sequence via lattice-controlled polymerization of racemic mixtures of precursor molecules that undergo spontaneous segregation into two-dimensional (2-D) enantiomorphous domains at the air-aqueous solution interface was analyzed. For model systems, we studied the polymerization reaction within 2-D crystalline domains of mixtures of (R,S)-N(epsilon)-stearoyl-thio-lysine with approximately 10% (R,S)-N(epsilon)-stearoyl-lysine, and (R,S)-N(alpha)-carboxyanhydride of N(epsilon)-stearoyl-lysine. According to in situ grazing incidence X-ray diffraction (GIXD) measurements at the air-water interface, the molecules form 2-D crystallites packing by translation symmetry only. Oligopeptides 4-6 units long were obtained at the air-solution interface after injection of an appropriate catalyst into the subphase. The course of the chemical transformations was monitored by GIXD. The distribution of the diastereoisomeric oligopeptides was determined by matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF MS) mass spectrometry on samples prepared from precursor molecules enantioselectively labeled with deuterium. The experimental relative abundance of oligopeptides with homochiral sequence was found to be larger than that calculated for a theoretical random process, yielding an excess by a factor of 2.5-3.5 for the tetra- to hexapeptides. The present studies may be relevant for probing the role that might have been played by ordered clusters at interfaces for the generation of homochiral oligopeptides under prebiotic conditions.
authors.affiliation: Department of Materials and Interfaces, The Weizmann Institute of Science, 76100-Rehovot, Israel. isabelle.weissbuch@weizmann.ac.il
authors.forename: Isabelle
authors.initials: I
authors.lastname: Weissbuch
authors.forename: Gérard
authors.initials: G
authors.lastname: Bolbach
authors.forename: Helmut
authors.initials: H
authors.lastname: Zepik
authors.forename: Edna
authors.initials: E
authors.lastname: Shavit
authors.forename: Mao
authors.initials: M
authors.lastname: Tang
authors.forename: Joseph
authors.initials: J
authors.lastname: Frey
authors.forename: Torben R
authors.initials: TR
authors.lastname: Jensen
authors.forename: Kristian
authors.initials: K
authors.lastname: Kjaer
authors.forename: Leslie
authors.initials: L
authors.lastname: Leiserowitz
authors.forename: Meir
authors.initials: M
authors.lastname: Lahav
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray; D007202:Indicators and Reagents; D008958:Models, Molecular; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000737:chemistry / Q000302:isolation & purification; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013237:Stereoisomerism; D013499:Surface Properties; D014867:Water
chemical_list: D007202:Indicators and Reagents; D009842:Oligopeptides; D014867:Water