MQAE

MQAE functions as a non-ratiometric chloride ion (Cl⁻) quenching fluorescent sensor that is employed to measure intracellular Cl⁻ concentration ([Cl⁻]_i), with the maximum wavelength excitation/emission(350/460nm)^[1]. MQAE is suitable for surface fluorescence microscopy, confocal microscopy, two-photon microscopy, flow cytometry and other biochemical analysis experiments^[1-2].The fluorescence intensity diminishes when MQAE concentration decreases and increases when MQAE concentration increases regardless of any changes in [Cl⁻]_i^[2]. The intracellular distribution of MQAE is not uniform and is not affected by changes in cell volume caused by osmotic stress^[3]. MQAE can bind to unknown subcellular structures, and these bound MQAE appear to enable the measurement of [Cl⁻]_i in airway-ciliated cells even in the presence of changes in cell volume^[1,4]. MQAE can be used to create a fluorescent probe for the detection of mitochondrial chloride ions^[5]. The fluorescence of MQAE-based probe is pH-insensitive in the physiological pH range and is quenched by chloride ions, with a Stern-Volmer quenching constant of 201M^-1 at pH 7.0^[5].

References:
[1] Ikeuchi Y, Kogiso H, Hosogi S, et al. Measurement of [Cl⁻]_i unaffected by the cell volume change using MQAE-based two-photon microscopy in airway ciliary cells of mice[J]. The journal of physiological sciences, 2018, 68: 191-199.
[2] Andersson C, Roomans G M. Determination of chloride efflux by X‐ray microanalysis versus MQAE‐fluorescence[J]. Microscopy research and technique, 2002, 59(6): 531-535.
[3] Koncz C, Daugirdas J T. Use of MQAE for measurement of intracellular [Cl⁻] in cultured aortic smooth muscle cells[J]. American Journal of Physiology-Heart and Circulatory Physiology, 1994, 267(6): H2114-H2123.
[4] Miyazaki H, Shiozaki A, Niisato N, et al. Physiological significance of hypotonicity-induced regulatory volume decrease: reduction in intracellular Cl⁻ concentration acting as an intracellular signaling[J]. American Journal of Physiology-Renal Physiology, 2007, 292(5): F1411-F1417.
[5] Park S H, Shin I, Kim Y H, et al. Mitochondrial Cl^–-selective fluorescent probe for biological applications[J]. Analytical Chemistry, 2020, 92(18): 12116-12119.

MQAE是一种非比例氯离子（Cl⁻）猝灭荧光传感物，最大激发光/发射光波长为350/460nm，用于测量细胞内Cl⁻浓度（[Cl⁻]_i）^[1]。MQAE适用于表面荧光显微镜、共聚焦显微镜、双光子显微镜以及流式细胞术等生化分析实验^[1-2]。无论[Cl⁻]_i变化如何，当MQAE浓度降低时，荧光强度减弱；当MQAE浓度增加时，荧光强度增强^[2]。MQAE在细胞内的分布不均匀，不受渗透压引起的细胞体积变化的影响^[3]。MQAE可与未知的亚细胞结构结合，而且这些结合的MQAE似乎可以在细胞体积发生变化的情况下测定气道纤毛细胞中的[Cl⁻]_i ^[1,4]。MQAE可用于构建检测线粒体氯离子的荧光探针^[5]。基于MQAE构建的探针的荧光在生理pH范围内对pH不敏感，被氯离子猝灭，在pH 7.0时Stern-Volmer猝灭常数为201M^-1[5]。