Ester carbonyl vibration as a sensitive probe of protein local electric field.
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.
Ultrafast Optical Processes Laboratory, Department of Chemistry, University of Pennsylvania, 231 S. 34th Street, Philadelphia, PA 19104 (USA).
Ileana M
IM
Pazos
Ayanjeet
A
Ghosh
Matthew J
MJ
Tucker
Feng
F
Gai
D004952:Esters / Q000737:chemistry*; D006860:Hydrogen Bonding; D055672:Static Electricity; D014732:Vibration
D004952:Esters
IR spectroscopy; carbonyl groups; hydrogen bonds; protein electrostatics; vibrational probes