al. 2007). Results show that the intracomplex AZD5363 datasheet condensation reaction in gas phase is associated to a very high free energy barrier due to the loss of metal coordination during the reaction. However, in aqueous solution, the important metal coordination changes observed in gas phase are largely attenuated. Moreover, the synergy between the interaction of glycines with Cu2+ and the presence selleck chemicals of water molecules acting as proton-transfer helpers significantly lower the activation, largely favoring the formation of the peptide bond. TS structure for the peptide bond formation in a) gas phase and b) aqueous
solution. Rimola Rimola, A., Rodriguez-Santiago, L., Ugliengo, P., Sodupe, M. (2007) Is the Peptide Bond Formation Activated by Cu2+ Interactions? Insights from Density Functional Calculations. J. Phys. Chem. B 111(20): 5740–5747. Rode, B. M. and
Suwannachot, Y. (1999) The possible role of Cu (II) for the origin of life. Coord. Chem. Rev. 190–192:1085–1099. Seto, C. and Stone, J. (1999) A. Int. J. Mass. Spectrom., 192:289–302 E-mail: mariona.[email protected].es Experimental Approaches to Fragment Condensation Pasquale Stano1, Macha Gorlero1, Rafal Wieczorek1,2, Salvatore Chessari3, Pier Luigi Luisi1,3 1Biology Dept.—University of RomaTre, Rome, Italy; 2European Centre for Living Technology (ECLT), Venice, Italy; 3Material Dept.— ETH Zurich, Switzerland It has been proposed that long peptides (or polynucleotides) may form by condensation of shorter sequences, i.e., the so-called fragment-condensation approach [Luisi, selleckchem 2006]. This mechanism of growth-and-selection may allow the formation of long and possible catalytic biopolymers even in the absence of direct (and/or directed) polymerization reactions. First, we have experimentally tested this model by combining random peptides (10-mers) into
an array of 20-mers, and then combining 20-mers into 40-mers. After every elongation step, which was carried out chemically by solid-phase synthesis, only soluble products were used for the next step. In this way, it has been possible to obtain one water-soluble Tangeritin peptide (40-mer) by iterative coupling-selection steps. The final sequence was provided of a short polar segment (four amino acids) at its N-terminus, in order to allow further analysis. Spectroscopic studies indicate the occurrence of stable secondary structure, although the peptide shows no omology with known protein sequences [Chessari et al., 2006]. Secondly, we have investigated the formation of peptide bonds by means of Ser-His, a peptide with esterase and protease activity [Li et al., 2000]. By using model compounds, we have demonstrated for the first time that Ser-His succesfully performs reverse-proteolysis by combining two peptide fragments, to give new longer peptides [Gorlero et al., submitted].