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Published on: December 17, 2013
Site-specific conversion of cysteine thiols into thiocyanate creates an IR probe for electric fields in proteins
Aaron T Fafarman1, Lauren J Webb, Jessica I Chuang
1Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA.
Abstract:
The nitrile stretching mode of the thiocyanate moiety is a nearly ideal probe for measuring the local electric field arising from the organized environment of the interior of a protein. Nitriles were introduced into three proteins: ribonuclease S (RNase S), human aldose reductase (hALR2), and the reaction center (RC) of Rhodobacter capsulatus, through a facile synthetic scheme for the transformation of cysteine residues into thiocyanatoalanine. Vibrational Stark effect spectroscopy and Fourier transform infrared spectroscopy on the modified proteins demonstrated that thiocyanate residues are a highly general tool for probing electrostatic fields in proteins.
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