pKa Determination of a Histidine Residue in a Short Peptide Using Raman Spectroscopy
pKa Determination of a Histidine Residue in a Short Peptide Using Raman Spectroscopy
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DOI：
10.3390/molecules24030405
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发表时间：
2019-02-01
期刊：
影响因子：
4.6
通讯作者：
Akerfeldt, Karin S.
中科院分区：
文献类型：
--
作者：
Pogostin, Brett H.;Malmendal, Anders;Akerfeldt, Karin S.
确定关键官能团的pKa对于理解生物蛋白质和基于肽的生物材料的pH依赖性行为至关重要。传统上，H-1 NMR光谱已用于测定氨基酸的pKa;然而，对于较大的分子和聚集系统，这种方法实际上是不可能的。先前的研究得出结论，拉曼中的C-D伸缩是用于确定组氨酸残基的pKa的有用替代方案。在这项研究中，我们报告的拉曼应用的C2-D探针组氨酸的咪唑侧链，以确定在一个短的肽序列组氨酸的pKa。通过差示拉曼光谱法发现三肽的pKa为6.82，并且该值通过相同肽的H-1 NMR光谱法独立地确认。还将C2-D探针与组氨酸质子化状态的其他拉曼报告物进行了比较，并确定其比其他质子化依赖性信号更灵敏和可靠。C2-D拉曼探针扩展了化学家的工具箱，可用于直接询问含组氨酸的肽和蛋白质系统的pKa。
Determining the pKa of key functional groups is critical to understanding the pH-dependent behavior of biological proteins and peptide-based biomaterials. Traditionally, H-1 NMR spectroscopy has been used to determine the pKa of amino acids; however, for larger molecules and aggregating systems, this method can be practically impossible. Previous studies concluded that the C-D stretches in Raman are a useful alternative for determining the pKa of histidine residues. In this study, we report on the Raman application of the C2-D probe on histidine's imidazole side chain to determining the pKa of histidine in a short peptide sequence. The pKa of the tripeptide was found via difference Raman spectroscopy to be 6.82, and this value was independently confirmed via H-1 NMR spectroscopy on the same peptide. The C2-D probe was also compared to other Raman reporters of the protonation state of histidine and was determined to be more sensitive and reliable than other protonation-dependent signals. The C2-D Raman probe expands the tool box available to chemists interested in directly interrogating the pKa's of histidine-containing peptide and protein systems.