Anomalous Diffusion in Inverted Variable-Lengthscale Fluorescence Correlation Spectroscopy

Biophys J. 2019 Mar 5;116(5):791-806. doi: 10.1016/j.bpj.2019.01.024. Epub 2019 Jan 30.


Using fluorescence correlation spectroscopy (FCS) to distinguish between different types of diffusion processes is often a perilous undertaking because the analysis of the resulting autocorrelation data is model dependant. Two recently introduced strategies, however, can help move toward a model-independent interpretation of FCS experiments: 1) the obtention of correlation data at different length scales and 2) their inversion to retrieve the mean-squared displacement associated with the process under study. We use computer simulations to examine the signature of several biologically relevant diffusion processes (simple diffusion, continuous-time random walk, caged diffusion, obstructed diffusion, two-state diffusion, and diffusing diffusivity) in variable-length-scale FCS. We show that, when used in concert, length-scale variation and data inversion permit us to identify non-Gaussian processes and, regardless of Gaussianity, to retrieve their mean-squared displacement over several orders of magnitude in time. This makes unbiased discrimination between different classes of diffusion models possible.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Diffusion*
  • Models, Theoretical
  • Spectrometry, Fluorescence*