Gas Phase Bond Formation in Dipeptide Clusters

Protein bonds between amino acids are one of the most important biological linkages that create life. The detection of amino acids in the interstellar environments and in meteorites may lead to the suggestion that amino acids came from outer space and that peptides bonds may have been created in the gas phase. Here we show experimentally the creation of covalent bonds, most likely peptide bonds, between serine dipeptides in the gas phase. More specifically, we show that spraying a solution of Ser-Ser dipeptides results, in addition to dipeptide clusters, in a peak with the same mass as the serine tetrapeptide, which also has the same fragmentation pattern. Moreover, we show that this mass is formed upon collision induced dissociation of clusters containing four serine dipeptides. Thence, if the dipeptide can be generated abiotically the polymerization process may occur spontaneously.