Analog Retinal Redshifts Visible Absorption of QuasAr Transmembrane Voltage Sensors into Near‐infrared
Analog Retinal Redshifts Visible Absorption of QuasAr Transmembrane Voltage Sensors into Near‐infrared
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DOI：
10.1111/php.13169
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发表时间：
2019-11
影响因子：
3.3
通讯作者：
Gaoxiang Mei;N. Mamaeva;S. Ganapathy;Peng Wang;W. J. DeGrip;K. Rothschild
中科院分区：
文献类型：
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作者：
Gaoxiang Mei;N. Mamaeva;S. Ganapathy;Peng Wang;W. J. DeGrip;K. Rothschild
基于视蛋白的跨膜电压传感器（OTVS）是神经科学中越来越重要的工具，使复杂脑回路中的神经功能能够在活的、有行为的动物中进行探索。然而，由于生物组织对可见光的强吸收和散射，当前一代OTVS的荧光激发所需的可见波长将脑中的光遗传学成像限制在仅几mm的深度。我们报告说，用含有甲氨基修饰的二甲基苯基环的视网膜类似物MMAR取代广泛使用的QuasAr 1/2 OTVS的天然A1视网膜发色团，导致吸收和荧光发射带的最大值分别红移超过100 nm，接近700 nm和840 nm。FT-拉曼光谱显示，在pH 7下，具有A1和MMAR发色团的QuasAr 1主要具有全反式质子化的席夫碱构型，其中MMAR发色团表现出与BR光循环的O-中间体类似的多烯单键/双键系统的增加的扭转。相比之下，QuasAr 2的A1和MMAR发色团部分以13-cis PSB构型存在。这些结果表明，含有MMAR发色团的QuasArs是用作NIR-OTVS的有吸引力的候选者，特别是对于诸如脑深部成像的应用。
Opsin‐based transmembrane voltage sensors (OTVSs) are increasingly important tools for neuroscience enabling neural function in complex brain circuits to be explored in live, behaving animals. However, the visible wavelengths required for fluorescence excitation of the current generation of OTVSs limit optogenetic imaging in the brain to depths of only a few mm due to the strong absorption and scattering of visible light by biological tissues. We report that substitution of the native A1 retinal chromophore of the widely used QuasAr1/2 OTVSs with the retinal analog MMAR containing a methylamino‐modified dimethylphenyl ring results in over a 100‐nm redshift of the maxima of the absorption and fluorescence emission bands to near 700 and 840 nm, respectively. FT‐Raman spectroscopy reveals that at pH 7 QuasAr1 with both the A1 and MMAR chromophores possess predominantly an all‐trans protonated Schiff base configuration with the MMAR chromophore exhibiting increased torsion of the polyene single‐/double‐bond system similar to the O‐intermediate of the BR photocycle. In contrast, the A1 and the MMAR chromophores of QuasAr2 exist partially in a 13‐cis PSB configuration. These results demonstrate that QuasArs containing the MMAR chromophore are attractive candidates for use as NIR‐OTVSs, especially for applications such as deep brain imaging.