title: The role of carbohydrates at the origin of homochirality in biosystems.
abstract: Pasteur has demonstrated that the chiral components in a racemic mixture can separate in homochiral crystals. But with a strong chiral discrimination the chiral components in a concentrated mixture can also phase separate into homochiral fluid domains, and the isomerization kinetics can then perform a symmetry breaking into one thermodynamical stable homochiral system. Glyceraldehyde has a sufficient chiral discrimination to perform such a symmetry breaking. The requirement of a high concentration of the chiral reactant(s) in an aqueous solution in order to perform and maintain homochirality; the appearance of phosphorylation of almost all carbohydrates in the central machinery of life; the basic ideas that the biochemistry and the glycolysis and gluconeogenesis contain the trace of the biochemical evolution, all point in the direction of that homochirality was obtained just after- or at a phosphorylation of the very first products of the formose reaction, at high concentrations of the reactants in phosphate rich compartments in submarine hydrothermal vents. A racemic solution of D,L-glyceraldehyde-3-phosphate could be the template for obtaining homochiral D-glyceraldehyde-3-phosphate(aq) as well as L-amino acids.
authors.affiliation: DNRF centre "Glass and Time", IMFUFA, Department of Sciences, Roskilde University, Postbox 260, 4000, Roskilde, Denmark, st@ruc.dk.
authors.forename: Søren
authors.initials: S
authors.lastname: Toxvaerd
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D002241:Carbohydrates / Q000737:chemistry*; D019418:Evolution, Chemical; D007700:Kinetics; D000069497:Origin of Life; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D002241:Carbohydrates; C010963:formose sugars