S-亚硝基-N-乙酰基-D,L-青霉胺二肽分子中S—NO键断裂能的测定

Determination of S—NO Bond Dissociation Energies of S-Nitroso-N-acetyl-D,L-penicillamine Dipeptides

利用滴定量热技术并结合适当的热力学循环测定了乙腈溶液中7个S-亚硝基-N-乙酰基-D，L-青霉胺二肽化合物中S—NO键的异裂能和均裂能，其能量范围分别为234．5～246．2kJ／mol和101．6～122．1kJ/mol. 结果表明，所研究的亚硝基硫醇化合物更容易通过S—NO键的均裂释放NO自由基（NO）．通过热力学循环对7个亚硝基硫醇化合物自由基负离子中S—NO键的异裂能和均裂能进行估算，能量范围分别为19．2～35．5kJ／mol和～4．2～22．6kJ／mol，表明这些自由基负离子在室温下不稳定，容易通过S—NO键的异裂释放出NO^-．

S-Nitrosodipeptides are generally believed to be good NO donors, and many NO-related biological functions have been directly associated with S-nitrosodipeptides, especially in the processes of NO-storage, transport and delivery. In this work, the heterolytic and homolytic S--NO bond dissociation energies of seven S-nitrosodipeptides were evaluated via titration calorimetry and relative thermodynamic cycles. The energetic scales of the heterolytic and homolytic S--NO bond dissociation energies of these RSNOs covered the ranges 234.5-246. 2 and 101.6-122. 1 kJ/mol, respectively, which indicated that the studied S-nitrosodipeptides were much easier to release a NO radical（ NO ） rather than a NO cation （ NO ^＋ ）. The estimation of the heter- olytic and homolytic （S--NO） ^- bond dissociation energies of the S-nitrosodipeptides radical anions gave the energetic ranges of 19.2-35.5 and 4.2-22. 6 kJ/mol for＇the（S-NO） ^-. bond homolysis and heterolysis, respectively, which meant that S-nitrosodipeptides radical anions were unstable at room temperature and favored to releasing a NO anion （NO^-） by heterolysis cleavage.