Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA,
J Am Soc Mass Spectrom. 2012 Apr;23(4):621-31. doi: 10.1007/s13361-011-0224-7. Epub 2011 Aug 18.
We present a full computational description of the fragmentation reactions of protonated diglycine (H(+)GG). Relaxed potential energy surface scans performed at B3LYP/6-31 G(d) or B3LYP/6-311 + G(d,p) levels are used to map the reaction coordinate surfaces and identify the transition states (TSs) and intermediate reaction species for seven reactions observed experimentally in the succeeding companion paper. All structures are optimized at the B3LYP/6-311 + G(d,p) level, with single point energies of the key optimized structures calculated at B3LYP and MP2(full) levels using a 6-311 + G(2 d,2p) basis set. These theoretical structures and energies are compared with extensive calculations in the literature. Although the pathways elucidated here are generally in agreement with those previously outlined, new details and, for some reactions, lower energy transition states are located. Further, the mechanism for the combined loss of carbon monoxide and ammonia is explored for the first time.
我们提出了质子化二肽（H(+)GG）的碎裂反应的全计算描述。在 B3LYP/6-31G(d)或 B3LYP/6-311 + G(d,p)水平上进行的松弛势能面扫描用于绘制反应坐标表面，并确定在后续的伴随论文中实验观察到的七种反应的过渡态（TS）和中间反应物种。所有结构均在 B3LYP/6-311 + G(d,p)水平上进行优化，使用 6-311 + G(2d,2p)基组在 B3LYP 和 MP2（全）水平上计算关键优化结构的单点能。这些理论结构和能量与文献中的广泛计算进行了比较。尽管这里阐明的途径通常与以前概述的途径一致，但发现了新的细节，并且对于一些反应，找到了能量更低的过渡态。此外，首次探索了一氧化碳和氨联合损失的机制。
