Unusual Spectroscopic and Electric Field Sensitivity of Chromophores with Short Hydrogen Bonds: GFP and PYP as Model Systems,The Journal of Physical Chemistry B

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Unusual Spectroscopic and Electric Field Sensitivity of Chromophores with Short Hydrogen Bonds: GFP and PYP as Model Systems
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-10-19 , DOI: 10.1021/acs.jpcb.0c07730
Chi-Yun Lin ₁ , Steven G Boxer ₁

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Short hydrogen bonds, with heavy-atom distances less than 2.7 Å, are believed to exhibit proton delocalization, and their possible role in catalysis has been widely debated. While spectroscopic and/or structural methods are usually employed to study the degree of proton delocalization, ambiguities still arise, and no direct information on the corresponding potential energy surface is obtained. Here, we apply an external electric field to perturb the short hydrogen bond(s) within a collection of green fluorescent protein S65T/H148D variants and photoactive yellow protein mutants, where the chromophore participates in the short hydrogen bond(s) and serves as an optical probe of the proton position. As the proton is charged, its position may shift in response to the external electric field, and the chromophore’s electronic absorption can thus reflect the ease of proton transfer. The results suggest that low-barrier hydrogen bonds (LBHBs) are not present within these proteins even when proton affinities between donor and acceptor are closely matched. Exploiting the chromophores as precalibrated electrostatic probes, the covalency of short hydrogen bonds as a nonelectrostatic component is also revealed. A theoretical framework is developed to address a possible contribution of unusually large polarizabilities of short hydrogen bonds due to proton delocalization, but no clear evidence for this phenomenon is found in accordance with the absence of LBHBs.

中文翻译：

具有短氢键的发色团的异常光谱和电场敏感性：GFP 和 PYP 作为模型系统

重原子距离小于 2.7 Å 的短氢键被认为表现出质子离域，它们在催化中的可能作用已被广泛争论。虽然通常采用光谱和/或结构方法来研究质子离域程度，但仍然存在歧义，并且无法获得相应势能表面的直接信息。在这里，我们应用外部电场来扰乱绿色荧光蛋白 S65T/H148D 变体和光敏黄色蛋白突变体集合中的短氢键，其中发色团参与短氢键并作为质子位置的光学探针。当质子带电时，它的位置可能会响应外部电场而发生变化，发色团的电子吸收因此可以反映质子转移的难易程度。结果表明，即使供体和受体之间的质子亲和力密切匹配，这些蛋白质中也不存在低屏障氢键 (LBHB)。利用发色团作为预校准的静电探针，还揭示了作为非静电成分的短氢键的共价性。开发了一个理论框架来解决由于质子离域引起的短氢键异常大极化率的可能贡献，但由于没有 LBHB，没有发现这种现象的明确证据。结果表明，即使供体和受体之间的质子亲和力密切匹配，这些蛋白质中也不存在低屏障氢键 (LBHB)。利用发色团作为预校准的静电探针，还揭示了作为非静电成分的短氢键的共价性。开发了一个理论框架来解决由于质子离域引起的短氢键异常大极化率的可能贡献，但由于没有 LBHB，没有发现这种现象的明确证据。结果表明，即使供体和受体之间的质子亲和力密切匹配，这些蛋白质中也不存在低屏障氢键 (LBHB)。利用发色团作为预校准的静电探针，还揭示了作为非静电成分的短氢键的共价性。开发了一个理论框架来解决由于质子离域引起的短氢键异常大极化率的可能贡献，但由于没有 LBHB，没有发现这种现象的明确证据。

更新日期：2020-10-30

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