Unimolecular reactivity upon collision of uracil-Ca2+ complexes in the gas phase: Comparison with uracil-M+ (M = H, alkali metals) and uracil-M2+ (M = Cu, Pb) systems

作者：Trujillo Cristina; Lamsabhi Al Mokhtar; Mo Otilia; Yanez Manuel; Salpin Jean Yves^*

来源：International Journal of Mass Spectrometry, 2011, 306(1): 27-36.

DOI：10.1016/j.ijms.2011.05.018

• Nanoelectrospray/mass spectrometry
• DFT calculations
• Unimolecular reactivity upon collision
• Calcium
• Uracil
• Potential energy surfaces

The stability against collisional dissociation of [uracil-Ca](2+) complexes has been investigated by combining nanoelectrospray ionization/mass spectrometry techniques and B3LYP/6-311++G(3df,2p)//B3LYP/6-31+G(d,p) density functional theory (DFT) calculations. The reactivity upon collision seems to be dominated by Coulomb explosion processes, since the most intense peaks in the MS/MS spectra correspond to singly-charged species (CaOH+ and [C-4,H-3,N-2,O](+)). Nevertheless, additional peaks corresponding to the loss of neutral species, namely [H,N,C,O] and H2O have been also detected. A systematic study of the CID spectra obtained with different labeled species, namely, 2-C-13-uracil, 3-N-15-uracil and 2-C-13-1,3-N-15(2)-uracil, concludes unambiguously that the loss of [H,N,C,O] involves exclusively atoms C2 and N3. Suitable mechanisms for these fragmentation processes are proposed through a theoretical survey of the corresponding potential energy surface. A comparison between these results and those reported for two other metal dications, namely Cu2+ and Pb2+,as well as for protonated uracil and uracil-M+ (M = Li, Na, K) complexes denotes the existence of significant differences and interesting similarities, among the various systems.

• 出版日期2011-9-1