Decomposition of Vibrational Shifts of Nitriles into Electrostatic and Hydrogen-Bonding Effects

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• 作者：Aaron T. Fafarman ; Paul A. Sigala ; Daniel Herschlag ; Steven G. Boxer
• 刊名：Journal of the American Chemical Society
• 出版年：2010
• 出版时间：September 22, 2010
• 年：2010
• 卷：132
• 期：37
• 页码：12811-12813
• 全文大小：162K
• 年卷期：v.132,no.37(September 22, 2010)
• ISSN：1520-5126

文摘

Infrared (IR) band shifts of isolated vibrational transitions can serve as quantitative and directional probes of local electrostatic fields, due to the vibrational Stark effect. However, departures from the Stark model can arise when the probe participates in specific, chemical interactions, such as direct hydrogen bonding. We present a method to identify and correct for these departures based on comparison of ¹³C NMR chemical shifts and IR frequencies each calibrated in turn by a solvatochromic model. We demonstrate how the tandem use of these experimental observables can be applied to a thiocyanate-modified protein, ketosteroid isomerase, and show, by comparison to structural models, that changes in electrostatic field can be measured within the complex protein environment even in the background of direct hydrogen bonding to the probe.