Modified Quadrupole Ion Trap Mass Spectrometer for Infrared Ion Spectroscopy: Application to Protonated Thiated Uridines
Modified Quadrupole Ion Trap Mass Spectrometer for Infrared Ion Spectroscopy: Application to Protonated Thiated Uridines
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DOI：
10.1007/s13361-018-2047-2
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发表时间：
2018-11-01
影响因子：
3.2
通讯作者：
Rodgers, M. T.
中科院分区：
文献类型：
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作者：
Hamlow, L. A.;Zhu, Y.;Rodgers, M. T.
详细介绍了对保罗型四极离子阱质谱仪的修改，提供了对捕获离子云的光学访问，以及用于耦合到桌面红外光学参量振荡器激光器 (OPO) 的硬件和软件。表征了该仪器上红外多光子解离 (IRMPD) 的关键实验参数。使用该仪器在氢伸缩区域收集的 IRMPD 作用光谱，辅以在 FELIX 设施获取的 IR 指纹区域中的光谱，用于表征 2-硫尿苷 [s(2)Urd+H](+) 和 4-硫尿苷 [s(4)Urd+H](+) 质子化形式的结构。将测量的光谱与在 B3LYP/6-311+G(d,p) 理论水平上计算的预测线性红外光谱进行比较，以确定实验中填充的构象异构体。该比较表明，2-位或4-位的硫杂化使2,4-H互变异构体和4-质子化之间的质子化偏好向相反方向移动，而经典尿苷对2,4-H互变异构体和O4质子化表现出大致相同的偏好。正如在经典尿苷中所发现的，质子化导致构象异构体的混合物表现出C2-内糖和C3-内糖褶皱，并且2-和4-硫代尿苷都填充有反核碱基方向。
Modifications to a Paul-type quadrupole ion trap mass spectrometer providing optical access to the trapped ion cloud as well as hardware and software for coupling to a table-top IR optical parametric oscillator laser (OPO) are detailed. Critical experimental parameters for infrared multiple photon dissociation (IRMPD) on this instrument are characterized. IRMPD action spectra, collected in the hydrogen-stretching region with this instrument, complemented by spectra in the IR fingerprint region acquired at the FELIX facility, are employed to characterize the structures of the protonated forms of 2-thiouridine, [s(2)Urd+H](+), and 4-thiouridine, [s(4)Urd+H](+). The measured spectra are compared with predicted linear IR spectra calculated at the B3LYP/6-311+G(d,p) level of theory to determine the conformers populated in the experiments. This comparison indicates that thiation at the 2- or 4-positions shifts the protonation preference between the 2,4-H tautomer and 4-protonation in opposite directions versus canonical uridine, which displays a roughly equal preference for the 2,4-H tautomer and O4 protonation. As found for canonical uridine, protonation leads to a mixture of conformers exhibiting C2-endo and C3-endo sugar puckering with an anti nucleobase orientation being populated for both 2- and 4-thiated uridine.