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Updated: Oct 19, 2025

Examining the Conformational Dynamics of Membrane Proteins in situ with Site-directed Fluorescence Labeling
Published on: May 29, 2011
Exploring the relationship between the "ON-OFF" mechanism of fluorescent probes and intramolecular charge transfer
Hongbin Zhan1, Hengwei Zhang1, Yi Wang1
1School of Biological Engineering, Dalian Polytechnic University, Dalian 116034, PR China.
Abstract:
In this study, the excited state charge distribution characteristics and fluorescence mechanism of HClO detection probes HN-ClO (weak fluorescence) and HN-ClO-F (strong fluorescence) probes were investigated based on density functional theory (DFT) and time-dependent density functional theory (TDDFT). The results of electrostatic potential (ESP) map and hole-electron analysis show that the HN-ClO and HN-ClO-F probes have obvious charge separation characteristics in the excited state. The excited state energy decomposition and Merz-Kollman charge analysis demonstrate the existence of distinct planar intramolecular charge transfer (PICT) features in HN-ClO and HN-ClO-F. Due to the strong charge coupling caused by the planar structure, the fluorescence of HN-ClO-F could occur. Furthermore, the weak fluorescence of HN-ClO is caused by inter-system crossing (ISC) between S1 and T1 state. Our result proves that the ICT process could exist in HN-ClO-F, but the PICT process does not cause fluorescence quenching, which have provided an excellent supplement to the mechanism of fluorescent probes. The conclusion is consistent with the fluorescence phenomenon observed in the experiment.
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