Infrared photodissociation spectroscopy of electrosprayed ions in a Fourier transform mass spectrometer
Infrared photodissociation spectroscopy of electrosprayed ions in a Fourier transform mass spectrometer
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DOI：
10.1021/ja040136n
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发表时间：
2005-03-23
影响因子：
15
通讯作者：
McLafferty, FW
中科院分区：
文献类型：
--
作者：
Oh, HB;Lin, C;McLafferty, FW
以前的红外光解离光谱(IRPD)的气相方法需要样品的挥发性。相反，我们的方法使用电喷雾电离将更大的非挥发性分子引入傅立叶变换质谱仪，在那里扩展(>；15 S)离子存储使使用OPO激光在3050-3800厘米(-1)范围内进行高灵敏度光谱测量成为可能。22个气态质子结合氨基酸络合物的光谱一般与溶液中O-H和N-H官能团的H-伸缩频率相关联。对于GIY(2)H(+)和N-酰化Asp(2)H(+)二聚体的理论结构预测，IRPD光谱明显区分预测的最低能量构象。与溶液相反，甘氨酸两性离子在气相中的稳定性低于中性，但在气态GIyLysH(+)二聚体中甘氨酸是明显的两性离子。对于较大的Lys(2)H(+)晚餐来说，理论水平是不够的，因为所有低能预测的结构都有游离的羧基O-H基团，与红外光谱相反。IRPD似乎是一种很有前途的新技术，可以提供广泛的生物分子和其他气体离子的独特信息，特别是涉及O-H和N-H基团的非共价键。
Previous gas-phase methods for infrared photodissociation spectroscopy (IRPD) require sample volatility. Our method instead uses electrospray ionization to introduce even large nonvolatile molecules into a Fourier transform mass spectrometer, where extended (> 15 s) ion storage makes possible high sensitivity spectral measurements with an OPO laser over a range of 3050-3800 cm(-1). The spectra of 22 gaseous proton-bound amino acid complexes are generally correlated with the H-stretching frequencies established for O-H and N-H functional groups in solution. For theoretical structure predictions of the GIY(2)H(+) and N-acylated Asp(2)H(+) dimers, IRPD spectra clearly differentiate between the predicted lowest energy conformers. In contrast to solution, in the gas phase the glycine zwitterion is similar to 20 kcal/mol less stable than the neutral; however, glycine is clearly zwitterionic in the gaseous GIyLysH(+) dimer. The level of theory is inadequate for the larger Lys(2)H(+) dinner, as all low energy predicted structures have free carboxyl O-H groups, in contrast to the IR spectrum. IRPD appears to be a promising new technique for providing unique information on a broad range of biomolecular and other gaseous ions, especially on noncovalent bonding involving O-H and N-H groups.