Theoretical Investigation of N-Nitrosation Mechanism of Amino Acids Mediated by N2O3

N-nitrosation mechanism of amino acids mediated by N2O3 was investigated at the B3LYP/6-311+G(d,p) level. Proline and tryptophan were selected as nitrosating substrates and their reactions with three different N2O3 isomers, i.e., asym-N2O3, sym-N2O3, and trans-cis N2O3 were studied respectively. The obtained results demonstrate that proline and tryptophan are able to be effectively nitrosated by all three N2O3 isomers, and the nitrosation of proline are somewhat easier than that of tryptophan. Moreover, the N-nitrosation of proline and tryptophan is easier to proceed by two relative unstable isomers sym-N2O3 and trans-cis N2O3 than asym-N2O3. The results obtained in this work will be helpful in better understanding the mechanism of N-nitrosation reactions of amino acids and even the modification of proteins through nitrosation.