merli@libero.it Surface-Enhanced Raman Investigation on the Peptide Formation by Adsorption of Glycine and Diglycine on Silica Maurizio Muniz-Miranda, Natale Neto Department of Chemistry, University
CAL-101 manufacturer of Florence, Via della Lastruccia 3, Sesto Fiorentino, I-50019 ITALY The evolution from simple molecules to complex systems and the origin of life had a determinant step in the peptide formation (Fitz, 2007; Plankensteiner 2005; Bujdak, 2003; Plankensteiner, 2002; Rode, 1999). This occurred in the prebiotic scenario by adsorption of aminoacids on silica, alumina and aluminosilicates, present in prominent amount on the Earth. Clay-catalyzed peptide formation probably involved the condensation reaction of Si-OH groups with the aminoacid carboxyl groups and was favored by hot temperature as well as NaCl at high concentration (Son, 1998, Bujdak, 1997). Many
efforts have been spent to simulate the primitive earth condition that enabled peptide formation, for example, oligopeptides have been obtained from glycine by silica- or alumina-catalyzed dehydration reactions (Rode, 1999; Bujadak, 1999).In the present study the efficiency of silica catalyst is checked by observing the SERS (surface-enhanced Raman scattering) signal of amino acids adsorbed on silver-doped colloidal silica. The SERS technique allows detecting very small amounts of analyte when the reagent is immobilized near metal surfaces constituted by silver, gold I-BET-762 in vitro or copper nanoparticles. Photoreduction of silver ions has been obtained on silica by visible light, resulting in efficient SERS-active colloidal substrates, with performances comparable to those of the usual silver hydrosols
(Muniz-Miranda, 2002). Here, after adsorption of glycine or diglycine on colloidal silica, the irradiation with the 514.5-nm laser line allows the formation of silver clusters and, consequently, the Raman evidence of the adsorbate. Niclosamide Thus, it is possible to detect the peptide formation by observing the SERS spectra of the learn more products deriving from the adsorption of glycine on silica particles. Glycine can be considered one of the most abundant amino acid in the primordial era before the occurring of biosystems, due to its simple structure. It exhibits the strongest reactivity, leading to diglycine and diketopiperazine, the cyclic anhydride of diglicine. Bujdak, J. and Rode, B. M. (1997). Silica, alumina, and clay-catalyzed alanine peptide bond formation. J. Mol. Evol. 45:457–466. Bujdak, J. and Rode, B. M. (1999). Silica, alumina and clay catalyzed peptide bond formation: enhanced efficiency of alumina catalyst. Origins of Life and Evolution of the Biosphere 29:451–461. Bujdak, J. and Rode, B. M. (2003). Peptide Bond Formation on the Surface of Activated Alumina: Peptide Chain Elongation. Catalysis Letters, 91:149–154. Fitz, D., Reiner, H. and Rode, B. M. (2007). Chemical evolution toward the origin of life. Pure Applied Chemistry,79:2101–2117.