Cation-size dependent conformational locking of glutamic acid by alkali ions: Infrared photodissociation spectroscopy of cryogenic ions
Cation-size dependent conformational locking of glutamic acid by alkali ions: Infrared photodissociation spectroscopy of cryogenic ions
复制标题
碱金属离子对谷氨酸的阳离子尺寸依赖性构象锁定：低温离子的红外光解离光谱
DOI：
10.1021/acs.jpcb.7b12601
复制
发表时间：
2018
期刊：
影响因子：
3.3
通讯作者：
O. Dopfer
中科院分区：
文献类型：
--
作者：
J. Klyne;A. Bouchet;S. Ishiushi;M. Fujii;O. Dopfer
要了解氨基酸及其簇的构象和稳定性，需要了解它们的生化识别。碱离子通常与氨基酸和蛋白质相互作用。本文系统分析了低温金属化谷氨酸离子（GluM+, M = Li-Cs）在异构体特异性指纹图谱和XH拉伸范围（1100-1900,2600-3600 cm-1）下的红外光解（IRPD）光谱，为阳离子大小依赖的构象锁定提供了直接测量方法。GluM+离子由电喷雾电离产生，并在低温四极离子阱中冷却至15 K。在色散校正的B3LYP-D3/aug-cc-pVTZ水平上，密度泛函理论计算支持了IRPD谱的分配。在GluM+的全局最小值中，Glu的柔韧性因形成刚性离子CO··M+··OC金属桥而强烈降低，这与电荷溶剂化相对应。Li-Cs的M+结合能随阳离子大小的增加而单调减小，从m0 = 314到119 kJ/mol。对于Li和Na，只观察到GluM+的全局最小值，而对于K-Cs，在低温下至少存在三个异构体。将冷GluM+离子的IRPD光谱与室温下测得的红外多光子解离光谱进行了比较。此外，我们还阐明了质子化和金属化对谷氨酸结构和构象锁定的不同影响。
Consolidated knowledge of conformation and stability of amino acids and their clusters is required to understand their biochemical recognition. Often, alkali ions interact with amino acids and proteins. Herein, infrared photodissociation (IRPD) spectra of cryogenic metalated glutamic acid ions (GluM+, M = Li–Cs) are systematically analyzed in the isomer-specific fingerprint and XH stretch ranges (1100–1900, 2600–3600 cm–1) to provide a direct measure for cation-size-dependent conformational locking. GluM+ions are generated by electrospray ionization and cooled down to 15 K in a cryogenic quadrupole ion trap. The assignment of the IRPD spectra is supported by density functional theory calculations at the dispersion-corrected B3LYP-D3/aug-cc-pVTZ level. In the global minimum of GluM+, the flexibility of Glu is strongly reduced by the formation of rigid ionic CO···M+···OC metal bridges, corresponding to charge solvation. The M+binding energy decreases monotonically with increasing cation size fromD0= 314 to 119 kJ/mol for Li–Cs. Whereas for Li and Na only the global minimum of GluM+is observed, for K–Cs at least three isomers exist at cryogenic temperature. The IRPD spectra of cold GluM+ions are compared to IR multiple-photon dissociation spectra measured at room temperature. Furthermore, we elucidate the differences of the impact of protonation and metalation on the structure and conformational locking of Glu.