Molecular Mechanism of Viscosity Sensitivity in BODIPY Rotors and Application to Motion-Based Fluorescent Sensors

• Published in: ACS sensors Vol. 5; no. 3; pp. 731 - 739
• Main Authors: Liu, Xiao, Chi, Weijie, Qiao, Qinglong, Kokate, Siddhant V, Cabrera, Eduardo Peña, Xu, Zhaochao, Liu, Xiaogang, Chang, Young-Tae
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 27.03.2020
• Subjects: Boron Compounds - chemistry; Fluorescent Dyes - chemistry; Molecular Probes; Motion; Viscosity; molecular rotor; viscosity; BODIPY; fluorescence; computation; motion-induced change in emission
• ISSN: 2379-3694; 2379-3694
• DOI: 10.1021/acssensors.9b01951

Viscosity in the intracellular microenvironment shows a significant difference in various organelles and is closely related to cellular processes. Such microviscosity in live cells is often mapped and quantified with fluorescent molecular rotors. To enable the rational design of viscosity-sensitive molecular rotors, it is critical to understand their working mechanisms. Herein, we systematically synthesized and investigated two sets of BODIPY-based molecular rotors to study the relationship between intramolecular motions and viscosity sensitivity. Through experimental and computational studies, two conformations (i.e., the planar and butterfly conformations) are found to commonly exist in BODIPY rotors. We demonstrate that the transformation energy barrier from the planar conformation to the butterfly conformation is strongly affected by the molecular structures of BODIPY rotors and plays a critical role in viscosity sensitivity. These findings enable rational structure modifications of BODIPY molecular rotors for highly effective protein detection and recognition.