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Excited-State Proton-Transfer-Induced Trapping Enhances the Fluorescence Emission of a Locked GFP Chromophore
Journal of Chemical Theory and Computation ( IF 5.7 ) Pub Date : 2016-01-15 00:00:00 , DOI: 10.1021/acs.jctc.5b00894 Xiang-Yang Liu 1 , Xue-Ping Chang 1 , Shu-Hua Xia 1 , Ganglong Cui 1 , Walter Thiel 2
Journal of Chemical Theory and Computation ( IF 5.7 ) Pub Date : 2016-01-15 00:00:00 , DOI: 10.1021/acs.jctc.5b00894 Xiang-Yang Liu 1 , Xue-Ping Chang 1 , Shu-Hua Xia 1 , Ganglong Cui 1 , Walter Thiel 2
Affiliation
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The chemical locking of the central single bond in core chromophores of green fluorescent proteins (GFPs) influences their excited-state behavior in a distinct manner. Experimentally, it significantly enhances the fluorescence quantum yield of GFP chromophores with an ortho-hydroxyl group, while it has almost no effect on the photophysics of GFP chromophores with a para-hydroxyl group. To unravel the underlying physical reasons for this different behavior, we report static electronic structure calculations and nonadiabatic dynamics simulations on excited-state intramolecular proton transfer, cis–trans isomerization, and excited-state deactivation in a locked ortho-substituted GFP model chromophore (o-LHBI). On the basis of our previous and present results, we find that the S1 keto species is responsible for the fluorescence emission of the unlocked o-HBI and the locked o-LHBI species. Chemical locking does not change the parts of the S1 and S0 potential energy surfaces relevant to enol–keto tautomerization; hence, in both chromophores, there is an ultrafast excited-state intramolecular proton transfer that takes only 35 fs on average. However, the locking effectively hinders the S1 keto species from approaching the keto S1/S0 conical intersections so that most of trajectories are trapped in the S1 keto region for the entire 2 ps simulation time. Therefore, the fluorescence quantum yield of o-LHBI is enhanced compared with that of unlocked o-HBI, in which the S1 excited-state decay is efficient and ultrafast. In the case of the para-substituted GFP model chromophores p-HBI and p-LHBI, chemical locking hardly affects their efficient excited-state deactivation via cis–trans isomerization; thus, the fluorescence quantum yields in these chromophores remain very low. The insights gained from the present work may help to guide the design of new GFP chromophores with improved fluorescence emission and brightness.
中文翻译：
激发态质子转移诱捕增强了锁定的GFP发色团的荧光发射。
绿色荧光蛋白（GFP）核心发色团中中心单键的化学锁定以独特的方式影响其激发态行为。实验上，它显着提高了具有邻羟基基团的GFP发色团的荧光量子产率，而对具有对羟基基团的GFP发色团的光物理几乎没有影响。为了揭示这种不同行为的潜在物理原因，我们报告了在锁定的邻位取代的GFP模型发色团中，静态电子结构计算和激发态分子内质子转移，顺反异构化和激发态失活的非绝热动力学模拟（o -LHBI）。根据我们之前和现在的结果，我们发现S 1酮类负责未锁定的o-HBI和锁定的o-LHBI物种的荧光发射。化学锁定不会改变与烯醇-酮互变异构相关的S 1和S 0势能表面的部分；因此，在这两个生色团中，均存在平均仅需35 fs的超快激发态分子内质子转移。但是，锁定有效地阻止了S 1酮类分子接近酮S 1 / S 0圆锥形相交点，因此大多数轨迹都被困在S 1中整个2 ps仿真时间内的酮区。因此，与未锁定的o-HBI相比，o-LHBI的荧光量子产率得到了提高，其中S 1激发态衰减是有效且超快的。在对位取代的GFP模型发色团p-HBI和p-LHBI的情况下，化学锁定几乎不影响它们通过顺式-反式异构化的有效激发态失活。因此，这些生色团的荧光量子产率仍然很低。从目前的工作中获得的见解可能有助于指导具有改进的荧光发射和亮度的新型GFP发色团的设计。
更新日期：2016-01-15
中文翻译：
激发态质子转移诱捕增强了锁定的GFP发色团的荧光发射。
绿色荧光蛋白（GFP）核心发色团中中心单键的化学锁定以独特的方式影响其激发态行为。实验上，它显着提高了具有邻羟基基团的GFP发色团的荧光量子产率，而对具有对羟基基团的GFP发色团的光物理几乎没有影响。为了揭示这种不同行为的潜在物理原因，我们报告了在锁定的邻位取代的GFP模型发色团中，静态电子结构计算和激发态分子内质子转移，顺反异构化和激发态失活的非绝热动力学模拟（o -LHBI）。根据我们之前和现在的结果，我们发现S 1酮类负责未锁定的o-HBI和锁定的o-LHBI物种的荧光发射。化学锁定不会改变与烯醇-酮互变异构相关的S 1和S 0势能表面的部分；因此，在这两个生色团中，均存在平均仅需35 fs的超快激发态分子内质子转移。但是，锁定有效地阻止了S 1酮类分子接近酮S 1 / S 0圆锥形相交点，因此大多数轨迹都被困在S 1中整个2 ps仿真时间内的酮区。因此，与未锁定的o-HBI相比，o-LHBI的荧光量子产率得到了提高，其中S 1激发态衰减是有效且超快的。在对位取代的GFP模型发色团p-HBI和p-LHBI的情况下，化学锁定几乎不影响它们通过顺式-反式异构化的有效激发态失活。因此，这些生色团的荧光量子产率仍然很低。从目前的工作中获得的见解可能有助于指导具有改进的荧光发射和亮度的新型GFP发色团的设计。
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