6–10 Jul 2026
University of the Western Cape
Africa/Johannesburg timezone
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Modelling Rotational Dynamics in Fluorescence Correlation Spectroscopy under Polarised Excitation

7 Jul 2026, 17:20
1h 20m
Great Hall (University of the Western Cape)

Great Hall

University of the Western Cape

Poster Presentation Track C - Photonics Poster Session 1

Speaker

Matthew Marlor (Stellenbosch University)

Description

Fluorescence correlation spectroscopy (FCS) is a technique in which a focused laser beam excites molecules within a small volume and fluctuations in the emitted fluorescence are analysed to extract information about molecular dynamics. These fluctuations arise from stochastic processes such as diffusion, photophysical transitions, and chemical kinetics, and are quantified through the autocorrelation function. In the case of individual fluorophores under linearly polarised excitation, the absorption probability depends on the angle between the molecular transition dipole and the incident electric field, following a $\cos^2 \theta$ dependence. This project describes the development of an FCS system and uses simulations to investigate the influence of laser polarisation on fluorophores undergoing rotational diffusion. The molecular dynamics are modelled at the single-molecule level, from which ensemble fluorescence fluctuations are constructed and analysed. The simulation is first validated using the mean-squared angular displacement. Polarisation-dependent fluorescence fluctuations are then used to extract rotational diffusion coefficients, which are compared with the known input values.

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Author

Matthew Marlor (Stellenbosch University)

Co-author

Gurthwin Bosman (Stellenbosch University)

Presentation materials

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