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Updated: Apr 28, 2026

Time-Resolved Fluorescence Anisotropy from Single Molecules for Characterizing Local Flexibility in Biomolecules
Published on: April 25, 2025
Anisotropic dissymmetry factor, g: theoretical investigation on single molecule chiroptical spectroscopy
Masamitsu Wakabayashi1, Satoshi Yokojima, Tuyoshi Fukaminato
1Department of Biomolecular Engineering, Tokyo Institute of Technology , 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501, Japan.
Abstract:
A formula for an anisotropic dissymmetry factor g evaluating the chiroptical response of orientationally fixed molecules is derived. Incorporating zeroth- and first-order multipole expansion terms, it is applied to bridged triarylamine helicene molecules to examine the experimental results of single-molecule chiroptical spectroscopy. The ground- and excited-state wave functions and a series of transition moments required for the evaluation of the anisotropic g value are calculated using time-dependent density functional theory (TDDFT). The probability histograms obtained for simulated g values, uniformly sampled in regard to the direction of light propagation toward the fixed molecule, show that even for a given diastereomer, the dissymmetry factors have positive and negative values and can deviate from their averages to a considerable extent when the angle between the electric dipole transition moment and the propagation vector of the incident light is near 0 or 180°.
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