ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry and Bio21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Victoria, Australia.
J Phys Chem A. 2011 May 5;115(17):4179-85. doi: 10.1021/jp200921w. Epub 2011 Apr 7.
Electrospray ionization and tandem mass spectrometry experiments have been used to study the fragmentation and electron-ion interactions of doubly charged zwitterionic clusters, M(15) + 2H (where M = Glycine Betaine (GB), (CH(3))(3)N(+)CH(2)CO(2)(-), and Dimethylsulfonioacetate (DMSA), (CH(3))(2)S(+)CH(2)CO(2)(-)) which are close to the stability limit, i.e., the Coulomb repulsion of the charge within the cluster competes with attractive forces. The intercluster chemistry was studied using collision-induced dissociation (CID) and electron-induced dissociation (EID) in which the energy of the electrons has been varied from >0 to 30 eV. Experimental results suggest that the zwitterionic binding energy in the clusters follow the order GB > DMSA, which is consistent with theoretical calculations that highlight that the lower dipole moment of DMSA leads to a binding energy of DMSA that is 0.86 times smaller than that for GB. Multiply protonated clusters of both GB and DMSA dissociate through Coulomb explosion, which is in competition with neutral evaporation for DMSA. Electronic excitation of the cluster under EID conditions at higher electron energies >12 eV can lead to new intercluster reactions associated with bond cleavages where differences between the sulfur and nitrogen betaines are minor.
电喷雾电离和串联质谱实验已被用于研究双重带电两性离子簇M(15) + 2H（其中 M = 甘氨酸甜菜碱（GB）、（CH(3))(3)N(+)CH(2)CO(2)(-)和二甲亚砜乙酸盐（DMSA）、(CH(3))(2)S(+)CH(2)CO(2)(-)）的碎裂和电子-离子相互作用，这些簇接近稳定性极限，即簇内电荷的库仑斥力与吸引力竞争。使用碰撞诱导解离（CID）和电子诱导解离（EID）研究了团簇间化学，其中电子的能量从>0 到 30 eV 不等。实验结果表明，簇中的两性离子结合能遵循 GB > DMSA 的顺序，这与理论计算一致，理论计算强调 DMSA 的较低偶极矩导致 DMSA 的结合能比 GB 小 0.86 倍。GB 和 DMSA 的多重质子化簇通过库仑爆炸解离，这与 DMSA 的中性蒸发竞争。在 EID 条件下，簇在较高电子能量（>12 eV）下的电子激发可能导致与键裂解相关的新的团簇间反应，其中硫代甜菜碱和氮代甜菜碱之间的差异较小。
