Condensation Of Amino Acids On Hydroxyapatite

The intermolecular amides of amino acids can be driven by hydroxyapatite at relatively low temperature in air. For example, the formation of (Ala)2 from Ala is induced on hydroxyapatite at 110℃with considerably yield; in comparison, condensing agents, high temperatures (>250℃) or high pressures (>25 Mpa) are frequently required to drive the reaction. The similar phenomena are observed in the Gly, Glu and Asp condensations. The experiments demonstrate that hydroxyapatite is an effective inorganic catalytic agent and the activation barrier can be decreased by more than 50%. The promotion effect is originated from the organized adsorption behavior of amino acid monomers on the mineral, which shortens the distance of the intermolecular amino and carboxyl group and extends the contacting time of reaction groups to facilitate the condensation reaction. This work provides a chemical understanding of the primitive condensation of amino acids and the enhancement mechanism of the mineral catalysis. It is important that the hydroxyapatite-assisted amide condition is not rigorous and can be provided readily by earth, which favors the continuance and persistence in chemical evolutions of biomolecules in the geologic age.The thesis consists of three chapters.Chapter 1 It introduces the three main hypothesis of prebiotic formation of primary organics and the supposed roles of minerals in this process. The previous study methods and understandings are also discussed.Chapter 2 It shows our study about the mineral assisted polymerization reaction of amino acids(Alanine, Glycine, Glutamic and aspartic). The results indicate hydroxyapatite can promote the condensation of amino acids.Chapter 3 Molecular simulation study about the catalysis effect of hydroxyapatite on the condensation of amino acids. The promotion effect can be explained by a view of cybernetic chemistry.Chapter 4 Summary and outlook.