Peptide precipitation driven synthesis

N Y 0 Precipitation-driven synthesis of peptides in organic solvent. 

N Y Eutectic melting A Precipitation-driven synthesis of peptides in aqueous phase. Two solid substrates form a liquid phase by eutectic melting. 

Precipitation-driven reactions show some very favorable advantages when compared to other low-water systems for enzymatic synthesis of peptides [55, 56]. 

The solid-to-solid approach clearly combines the good rates observed in aqueous solution, with the high yields typical of biocatalysis in organic solvents. Many successful examples of precipitation-driven reactions for the synthesis of peptides have been published in recent years (Table 12.3). 

Table 12.4 Precipitation-driven biocatalysis for the synthesis of peptides, catalyzed by proteases, in the presence of organic solvents.

Prebiotic peptides, peptides formed before the origin of life. Most likely, amino acids were already present on primitive Earth. They are supposed to have been produced in the primitive atmosphere, in hydrothermal vents, or to have been imported in meterorites. a-Amino acids can undergo peptide formation by activation with carbon monoxide under hot aqueous conditions in the presence of freshly co-precipitated colloidal (Fe,Ni)S. Peptides may have been formed via —>-N-carboxy anhydrides. A replicative synthesis involving aminoacyl-RNA intermediates has also been suggested. The question of whether a peptide/protein world preceded the RNA-driven template synthesis, or whether RNA and proteins should not be viewed as eti-ologically discrete entities in the origin of life, is still under debate [V. Borsenberger et al., Chem. Biodivers. 2004, 1, 203 C. Huber et al., Science 2003, 301, 938 A. Brack, Chem. Biodivers. 2007, 4, 665]. 

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