科研之友
微信
新浪微博
Facebook
分享链接
摘要
To evaluate the influence of the peptide bond on the nature of pyrolysis products released from proteinaceous material, 16 dipeptides were subjected to pyrolysis in the presence of TMAH. The pyrolysis products were identified by GC-MS and compared to those obtained from corresponding single amino acids. Most of the main dipeptide pyrolysis products do not correspond to the major products released upon pyrolysis of the constitutive amino acids. Depending on the considered dipeptide, different mechanisms were shown to be responsible for the formation of the major pyrolysis products. An important pathway, due to TMAH, is the direct methylation of the peptide, along with the formation of piperazine-2,5-diones (DKPs) previously observed from single amino acids. Besides these simple compounds, the formation of new cyclic compounds, more complex cyclisation derivatives based on three amino acids and cyclic products related to imidazolidinones, was revealed. Based on their structure, different possible mechanisms of formation are proposed for these cyclic compounds. It must be noted that no general trend, related to structure or polarity of the amino acids constituent of the dipeptides, allows predicting the nature of their pyrolysis products. However it can be noticed that the formation of imidazolidinone is only observed when the dipeptide contains an OH group in an aliphatic side chain. Comparison between symmetric or almost symmetric dipeptides as Met-Leu/Leu-Met or Val-Thr/Thr-Leu shows that complex DKPs are only formed from one of the dipeptide, highlighting the importance of the C- or N-terminal position of the amino acids. In most cases, the side chain from at least one constitutive amino acid is identifiable in these cyclic compounds thus evidencing the contribution of this amino acid. These products can thus be used as markers in addition to the well-known simple DKPs.
- 出版日期2013-11
