Local Analysis of Heterogeneous Intracellular Transport: Slow and Fast Moving Endosomes.

Area of Science:

• Cell Biology
• Biophysics
• Statistical Mechanics

Background:

• Endosome trajectories in living cells exhibit complex, heterogeneous motion.
• This anomalous diffusion arises from factors like viscoelasticity, caging, aggregation, and active transport.
• Observed trajectories show diverse behaviors, including persistent/anti-persistent motion and localized confinement.

Purpose of the Study:

• To analyze and model the heterogeneous motion of endosomes within eukaryotic cells.
• To differentiate and characterize the dynamics of slow (subdiffusive) and fast (superdiffusive) endosomes.
• To determine an appropriate statistical model for describing endosome trajectories.

Main Methods:

• Splitting the ensemble of endosome trajectories into distinct slow and fast moving groups.
• Analysis of mean squared displacements and velocity auto-correlation functions.
• Application of local analysis to determine anomalous exponents and diffusion coefficients.

Main Results:

• The splitting method effectively separated endosome trajectories based on motion characteristics.
• Both slow and fast endosome populations displayed a spectrum of local anomalous exponents and diffusion coefficients.
• Local anomalous exponents followed exponential distributions, while generalized diffusion coefficients followed power-law distributions.

Conclusions:

• Heterogeneous fractional Brownian motion is a suitable model for describing both fast and slow endosome dynamics.
• This model captures the observed complexity and heterogeneity in intracellular endosome transport.
• The findings contribute to a deeper understanding of single-particle tracking analysis in biological systems.