Pazos Ileana M, Ghosh Ayanjeet, Tucker Matthew J, Gai Feng
Ultrafast Optical Processes Laboratory, Department of Chemistry, University of Pennsylvania, 231 S. 34th Street, Philadelphia, PA 19104 (USA).
Angew Chem Int Ed Engl. 2014 Jun 10;53(24):6080-4. doi: 10.1002/anie.201402011. Epub 2014 Apr 30.
The ability to quantify the local electrostatic environment of proteins and protein/peptide assemblies is key to gaining a microscopic understanding of many biological interactions and processes. Herein, we show that the ester carbonyl stretching vibration of two non-natural amino acids, L-aspartic acid 4-methyl ester and L-glutamic acid 5-methyl ester, is a convenient and sensitive probe in this regard, since its frequency correlates linearly with the local electrostatic field for both hydrogen-bonding and non-hydrogen-bonding environments. We expect that the resultant frequency-electric-field map will find use in various applications. Furthermore, we show that, when situated in a non-hydrogen-bonding environment, this probe can also be used to measure the local dielectric constant (ε). For example, its application to amyloid fibrils formed by Aβ(16-22) revealed that the interior of such β-sheet assemblies has an ε value of approximately 5.6.
量化蛋白质以及蛋白质/肽组装体的局部静电环境的能力，是从微观层面理解许多生物相互作用和过程的关键。在此，我们表明，两种非天然氨基酸（L-天冬氨酸4-甲酯和L-谷氨酸5-甲酯）的酯羰基伸缩振动在这方面是一种便捷且灵敏的探针，因为其频率在氢键和非氢键环境中均与局部静电场呈线性相关。我们预计所得的频率-电场图将在各种应用中得到应用。此外，我们还表明，当处于非氢键环境中时，该探针还可用于测量局部介电常数（ε）。例如，将其应用于由Aβ(16 - 22)形成的淀粉样纤维时发现，此类β-折叠组装体的内部ε值约为5.6。
