Excited States of Fluorescent Proteins, mKO and DsRed: Chromophore-Protein Electrostatic Interaction Behind the Color Variations
Excited States of Fluorescent Proteins, mKO and DsRed: Chromophore-Protein Electrostatic Interaction Behind the Color Variations
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DOI：
10.1021/jp9099573
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发表时间：
2010-03-04
影响因子：
3.3
通讯作者：
Shiro, Yoshitsugu
中科院分区：
文献类型：
--
作者：
Hasegawa, Jun-ya;Ise, Takehiko;Shiro, Yoshitsugu
采用QM/MM和SAC-CI方法研究了绿色荧光蛋白（GFP）、单体Kusabira orange （mKO）和Discosoma red （DsRed）的发光状态。通过比较蛋白腔中绿色、橙色和红色发射态的电子结构以及它们之间的静电和量子力学相互作用，阐明了决定发射颜色的基本机制。我们发现mKO和DsRed的橙色和红色发射分别是π骨架扩展（红移）和蛋白质静电势（蓝移）两种效应相互抵消的结果。pi骨架的延伸增强了跃迁的分子内电荷转移特性，使荧光能量对蛋白质的静电势更加敏感。基于这一机制，我们预测了氨基酸突变可能导致DsRed发射能量红移。一个新的单氨基酸突变，通过计算检验，将DsRed发射能量从2.14（579色调）降低到1.95 eV (636 nm)，接近近红外荧光。
The emitting states of green fluorescent protein (GFP), monomeric Kusabira orange (mKO), and Discosoma red (DsRed) were studied using QM/MM and SAC-CI methods. By comparing the electronic structures among the green-, orange-, and red-emitting states as well as their electrostatic and quantum mechanical interactions within the protein cavity, the basic mechanisms for determining emission colors have been clarified. We found that the orange and red emissions of mKO and DsRed, respectively, result from cancellation between two effects, the pi skeleton extension (red shift) and protein electrostatic potential (blue shift). The extension of the pi skeleton enhances the intramolecular charge-transfer character of the transition, which makes the fluorescence energy more sensitive to the protein's electrostatic potential. On the basis of this mechanism, we predicted amino acid mutations that Could red shift the emission energy of DsRed. A novel single amino acid mutation, which was examined computationally, reduced the DsRed emission energy from 2.14 (579 tint) to 1.95 eV (636 nm), which is approaching near-infrared fluorescence.