New York University Abu Dhabi, Saadiyat Island, P.O. Box 129188, Abu Dhabi, United Arab Emirates.
ACS Chem Neurosci. 2022 Dec 21;13(24):3578-3596. doi: 10.1021/acschemneuro.2c00492. Epub 2022 Dec 9.
Precise photochemical control, using two-photon excitation (2PE), of the timing and location of activation of glutamate is useful for studying the molecular and cellular physiology of the brain. Antenna-based light harvesting strategies represent a general method to increase the sensitivity to 2PE of otherwise insensitive photoremovable protecting groups (PPGs). This was applied to the most commonly used form of "caged" glutamate, MNI-Glu. Computational investigation showed that a four- or six-carbon linker attached between the 4-position of thioxanthone (THX) and the 4-position of the 5-methyl derivative of MNI-Glu (MMNI-Glu) would position the antenna and PPG close to one another to enable Dexter energy transfer. Nine THX-MMNI-Glu conjugates were prepared and their photochemical properties determined. Installation of the THX antenna resulted in a red shift of the absorption (λ = 385-405 nm) along with increased quantum yield compared to the parent compound MNI-Glu (λ = 347 nm). The THX-MMNI-Glu conjugate with a four-carbon linker and attachment to the 4-position of THX underwent photolysis via 1PE at 405 and 430 nm and via 2PE at 770 and 860 nm, yielding glutamate. The two-photon uncaging action cross section (δ) was 0.11 and 0.29 GM at 770 and 860, respectively, which was greater than for MNI-Glu (0.06 and 0.072 GM at 720 and 770 nm, respectively). The THX sensitizer harvested the light via 2PE and transferred its resulting triplet energy to MMNI-Glu. Release of glutamate through 2PE at 860 nm from the compound (100 μM) activated iGluSnFR, a genetically encoded, fluorescent glutamate sensor, on the surface of cells in culture, portending its usefulness in studies of neurophysiology in acute brain slice.
利用双光子激发（2PE）精确控制谷氨酸的激活时间和位置对于研究大脑的分子和细胞生理学非常有用。基于天线的光捕获策略代表了一种通用方法，可以提高对原本不敏感的光解保护基团（PPG）的 2PE 灵敏度。这一策略应用于最常用的“笼型”谷氨酸形式，即 MNI-Glu。计算研究表明，将噻吨酮（THX）的 4-位和 MNI-Glu 的 5-甲基衍生物（MMNI-Glu）的 4-位之间连接一个四或六个碳原子的连接子，将天线和 PPG 彼此靠近，以实现 Dexter 能量转移。制备了 9 种 THX-MMNI-Glu 缀合物，并测定了它们的光化学性质。安装 THX 天线会导致吸收红移（λ=385-405nm），与母体化合物 MNI-Glu（λ=347nm）相比，量子产率也有所提高。具有四碳连接子且连接到 THX 的 4-位的 THX-MMNI-Glu 缀合物可通过 1PE 在 405nm 和 430nm 以及 2PE 在 770nm 和 860nm 下发生光解，生成谷氨酸。双光子解笼作用截面（δ）分别为 0.11 和 0.29 GM，在 770nm 和 860nm 下，大于 MNI-Glu（分别为 0.06 和 0.072 GM，在 720nm 和 770nm 下）。THX 敏化剂通过 2PE 吸收光，并将其产生的三重态能量转移到 MMNI-Glu。在细胞表面培养的细胞中，通过 860nm 处的 2PE 从化合物（100μM）释放谷氨酸激活了 iGluSnFR，这是一种遗传编码的、荧光谷氨酸传感器，预示着其在急性脑切片神经生理学研究中的应用前景。
