Ester Carbonyl Vibration as a Sensitive Probe of Protein Local Electric Field |
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Authors: | Ileana M Pazos Dr Ayanjeet Ghosh Prof?Dr Matthew J Tucker Prof?Dr Feng Gai |
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Institution: | 1. Ultrafast Optical Processes Laboratory, Department of Chemistry, University of Pennsylvania, 231 S. 34th Street, Philadelphia, PA 19104 (USA);2. Current address: Department of Chemistry, University of Wisconsin‐Madison, 1101 University Avenue, Madison, WI 53706 (USA);3. Department of Chemistry, University of Nevada, 1664 N. Virginia Street, Reno, NV 89557 (USA) |
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Abstract: | 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 Aβ16–22 revealed that the interior of such β‐sheet assemblies has an ε value of approximately 5.6. |
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Keywords: | carbonyl groups hydrogen bonds IR spectroscopy protein electrostatics vibrational probes |
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