Collect. Czech. Chem. Commun. 2011, 76, 207-222
Published online 2011-02-23 09:47:57

Monte Carlo simulation of fluorescence correlation spectroscopy data

Peter Košovana, Filip Uhlíka, Jitka Kuldováa, Miroslav Štěpáneka, Zuzana Limpouchováa, Karel Procházkaa,*, Aleš Bendab, Jana Humpolíčkováb and Martin Hofb

a Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University in Prague, Albertov 6, 12843 Prague 2, Czech Republic
b J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 5, Prague 8, Czech Republic


We employed the Monte Carlo simulation methodology to emulate the diffusion of fluorescently labeled particles and understand the source of differences between values of diffusion coefficients (and consequently hydrodynamic radii) of fluorescently labeled nanoparticles measured by fluorescence correlation spectroscopy (FCS) and dynamic light scattering (DLS). We used the simulation program developed in our laboratory and studied the diffusion of spherical particles of different sizes, which are labeled on their surface. In this study, we focused on two complicating effects: (i) multiple labeling and (ii) rotational diffusion which affect the fluorescence signal from large particles and hinder the analysis of autocorrelation functions according to simple analytical models. We have shown that the fluorescence fluctuations can be well fitted using the analytical model for small point-like particles, but the obtained parameters deviate in some cases significantly from the real ones. It means that the current data treatment yields apparent values of diffusion coefficients and other parameters only and the interpretation of experimental results for systems of particles with sizes comparable to the size of the active illuminated volume requires great care and precaution.

Keywords: Diffusion coefficient; Dynamic light scattering; Fluorescence spectroscopy; Monte Carlo method; Rotational diffusion; Translational diffusion.

References: 19 live references.