A Solvatochromic Model Calibrates Nitriles’ Vibrational Frequencies to Electrostatic Fields

Citations Over TimeTop 10% of 2012 papers

Abstract

Electrostatic interactions provide a primary connection between a protein's three-dimensional structure and its function. Infrared probes are useful because vibrational frequencies of certain chemical groups, such as nitriles, are linearly sensitive to local electrostatic field and can serve as a molecular electric field meter. IR spectroscopy has been used to study electrostatic changes or fluctuations in proteins, but measured peak frequencies have not been previously mapped to total electric fields, because of the absence of a field-frequency calibration and the complication of local chemical effects such as H-bonds. We report a solvatochromic model that provides a means to assess the H-bonding status of aromatic nitrile vibrational probes and calibrates their vibrational frequencies to electrostatic field. The analysis involves correlations between the nitrile's IR frequency and its (13)C chemical shift, whose observation is facilitated by a robust method for introducing isotopes into aromatic nitriles. The method is tested on the model protein ribonuclease S (RNase S) containing a labeled p-CN-Phe near the active site. Comparison of the measurements in RNase S against solvatochromic data gives an estimate of the average total electrostatic field at this location. The value determined agrees quantitatively with molecular dynamics simulations, suggesting broader potential for the use of IR probes in the study of protein electrostatics.

Related Papers

• → Solvatochromism of dyes inspired in Effenberger's probe(2020)19 cited
• → Reversal in solvatochromism in some novel styrylpyridinium dyes having a hydrophobic cleft(2007)49 cited
• → Solvatochromism of dyes. Part III. Solvatochromism of merocyanines in some binary mixtures of solvents.SA-SAB-SB, a new model of solvatochromism(1997)12 cited
• → Solvatochromism and piezochromism of pentacyanoferrate(II) complexes in binary aqueous solvent media(1993)7 cited
• → Solvatochromism of dyes. Part III. Solvatochromism of merocyanines in some binary mixtures of solvents.SA–SAB–SB, a new model of solvatochromism(1997)