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Updated: Jul 14, 2026

Time-Resolved Fluorescence Anisotropy from Single Molecules for Characterizing Local Flexibility in Biomolecules
Published on: April 25, 2025
Two-photon excited fluorescence and molecular reorientations in liquid solutions
Linus Ryderfors1, Emad Mukhtar, Lennart B-A Johansson
1Department of Photochemistry and Molecular Science, Uppsala University, 751 20-Uppsala, Sweden.
Abstract:
Theoretical expressions are derived that relate the two-photon excited fluorescence depolarisation experiments to the molecular symmetry and the rotational motions of fluorescent molecules. Diffusive rotational motions in liquid solvents are considered, as well as the influence of fast unresolved motions (e.g. librations). The results obtained are compared with one-photon excited fluorescence depolarisation experiments. The derived theoretical expressions can be applied for detailed analyses of the molecular rotation in solvent. Several of the results are useful for determining and assigning the components of two-photon absorption tensors.
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