Innershell absorption Spectroscopy of amino acids
Innershell absorption Spectroscopy of amino acids
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DOI：
10.1021/jp013385w
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发表时间：
2002-04-04
影响因子：
2.9
通讯作者：
Hitchcock, AP
中科院分区：
文献类型：
--
作者：
Kaznacheyev, K;Osanna, A;Hitchcock, AP
我们对自然界中常见的所有 20 种氨基酸的 C（碳）K 边缘近边缘 X 射线吸收 (NEXAFS) 光谱进行了全面测量。识别具有相似化学特征的氨基酸光谱的定性趋势，并将光谱特征与广泛的从头计算进行比较。已确定各个单元和替代组的贡献，以使用构建块概念探索其指纹特征。发现了几个这样的单位。 C Is NEXAFS 光谱中给出特别清晰特征的两个是羧基（由于 C 1s-->pi*c-o 转变，最大值为 288.65(5) eV，因此可以通过明显的结构清楚地识别）和芳香族氨基酸中的修饰酚环（产生尖锐的 C 1s-->pi*c=o 结构）。后者的转变位于 285 cV 左右，其形状对于每种芳香族氨基酸而言是特定的。其他结构单元，如 CNH(n) 基团和 CH、CC、CO、CN 对键，也被识别出来，尽管它们的特征在 C K 边缘光谱中不如羧基和芳香族结构明显。这项研究为氨基酸的 NEXAFS 光谱的严格分配提供了基础，并将有助于开发用于蛋白质定量分析的 X 射线吸收光谱。
We present comprehensive measurements of the C (carbon) K edge near-edge X-ray absorption (NEXAFS) spectra of all 20 amino acids commonly occurring in nature. Qualitative trends among the spectra of amino acids with similar chemical character are identified and spectral features are compared with extensive ab initio calculations. The contributions of individual units and substitutional groups have been determined to explore their fingerprinting character using the building block concept. Several such units are found. Two that give particularly clear features in the C Is NEXAFS spectra are the carboxyl group (which can be clearly identified by a pronounced structure due to the C 1s-->pi*c-o transition with maximum at 288.65(5) eV) and modified phenol rings in aromatic amino acids (which give sharp C 1s-->pi*c=o structures). The latter transitions are located around 285 cV, and their shape is specific for each aromatic amino acid. Other building blocks, such as the CNH(n) group and the CH, CC, CO, CN pair bonds, are also identified, although their characteristic features are less pronounced in the C K edge spectra than the carboxylic and aromatic structures. This study provides the basis for rigorous assignment of the NEXAFS spectra of the amino acids, and will be helpful in developing X-ray absorption spectroscopy for quantitative analysis of proteins.