State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Hi-tech Zone, Dalian 116024, PR China.
J Am Chem Soc. 2011 May 4;133(17):6626-35. doi: 10.1021/ja1104014. Epub 2011 Apr 8.
Intracellular viscosity strongly influences transportation of mass and signal, interactions between the biomacromolecules, and diffusion of reactive metabolites in live cells. Fluorescent molecular rotors are recently developed reagents used to determine the viscosity in solutions or biological fluid. Due to the complexity of live cells, it is important to carry out the viscosity determinations in multimode for high reliability and accuracy. The first molecular rotor (RY3) capable of dual mode fluorescence imaging (ratiometry imaging and fluorescence lifetime imaging) of intracellular viscosity is reported. RY3 is a pentamethine cyanine dye substituted at the central (meso-) position with an aldehyde group (CHO). In nonviscous media, rotation of the CHO group gives rise to internal conversion by a nonradiative process. The restraining of rotation in viscous or low-temperature media results in strong fluorescence (6-fold increase) and lengthens the fluorescence lifetime (from 200 to 1450 ps). The specially designed molecular sensor has two absorption maxima (λ(abs) 400 and 613 nm in ethanol) and two emission maxima (in blue, λ(em) 456 nm and red, 650 nm in ethanol). However it is only the red emission which is markedly sensitive to viscosity or temperature changes, providing a ratiometric response (12-fold) as well as a large pseudo-Stokes shift (250 nm). A mechanism is proposed, based on quantum chemical calculations and (1)H NMR spectra at low-temperature. Inside cells the viscosity changes, showing some regional differences, can be clearly observed by both ratiometry imaging and fluorescence lifetime imaging (FLIM). Although living cells are complex the correlation observed between the two imaging procedures offers the possibility of previously unavailable reliability and accuracy when determining intracellular viscosity.
细胞内的黏度强烈影响着物质和信号的传输、生物大分子之间的相互作用以及活性代谢物在活细胞中的扩散。荧光分子转子是最近开发的用于测定溶液或生物流体黏度的试剂。由于活细胞的复杂性，为了获得高可靠性和准确性，进行多模式黏度测定非常重要。本文报道了第一个能够进行细胞内黏度的双模荧光成像（比率成像和荧光寿命成像）的分子转子（RY3）。RY3 是一种五甲川菁染料，在中央（中位）位置用醛基（CHO）取代。在非粘性介质中，CHO 基团的旋转通过非辐射过程引起内转换。在粘性或低温介质中旋转受到限制会导致强烈的荧光（增加 6 倍）和荧光寿命延长（从 200 到 1450 ps）。该专门设计的分子传感器具有两个吸收最大值（λ（abs）在乙醇中为 400 和 613nm）和两个发射最大值（在蓝色，λ（em）在乙醇中为 456nm 和红色，650nm）。然而，只有红色发射对黏度或温度变化具有明显的敏感性，提供了比率响应（12 倍）和大的赝斯托克斯位移（250nm）。基于量子化学计算和低温下的（1）H NMR 光谱，提出了一种机制。在细胞内，黏度变化显示出一些区域差异，可以通过比率成像和荧光寿命成像（FLIM）清楚地观察到。尽管活细胞很复杂，但在两种成像过程之间观察到的相关性为确定细胞内黏度提供了以前无法获得的可靠性和准确性。
