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Orientation of the peptide formation of N-phosphoryl amino acids in solution

The peptide formation of N-phosphoryl amino acids with amino acids proceeds in aqueous solution without any coupling reagents. After being separated in sephadex gel column, the phosphoryl dipeptides were analyzed by the electrospray ionization tandem mass spectrometry (ESIMS/ MS). The result demonstrates that phosphoryl dipeptides were detected in all the reaction systems. It is found that the formation of N-phosphoryl dipeptides is oriented: the N-terminal amino acid residues of the N-phosphoryl dipeptides are from N-phosphoryl amino acids, and the peptide elongation happened at the C-terminal. Only a-dipeptide, no β-dipeptide, is formed in the N-phosphoryl dipeptides, showing that a-carboxylic group is activated selectively by N-phosphorylation. Theoretical calculation shows that the peptide formation of N-phosphoryl amino acids might happen through a penta-coordinate carboxylic-phosphoric intermediate in solution. These results might give some clues to the study on the origin of proteins and protein biosynthesis.