Fluorescence correlation spectroscopy

Quantum mechanics

Cytoplasm

Chemical physics

Nanoparticle

Biology

Materials science

Cytosol

Brownian motion

Anomalous diffusion

Biochemistry

Molecule

Thermal diffusivity

Computer science

Macromolecular crowding

Intracellular

Thermodynamics

Physics

Nanotechnology

Organic chemistry

Membrane

Diffusion

Fluorescence recovery after photobleaching

Enzyme

Macromolecule

Brownian dynamics

Composite material

Innovation diffusion

Chemistry

Viscosity

Knowledge management

Biophysics

Nature Materials

The diffusivity of macromolecules in the cytoplasm of eukaryotic cells varies over orders of magnitude and dictates the kinetics of cellular processes. However, a general description that associates the Brownian or anomalous nature of intracellular diffusion to the architectural and biochemical properties of the cytoplasm has not been achieved. Here we measure the mobility of individual fluorescent nanoparticles in living mammalian cells to obtain a comprehensive analysis of cytoplasmic diffusion. We identify a correlation between tracer size, its biochemical nature and its mobility. Inert particles with size equal or below 50 nm behave as Brownian particles diffusing in a medium of low viscosity with negligible effects of molecular crowding. Increasing the strength of non-specific interactions of the nanoparticles within the cytoplasm gradually reduces their mobility and leads to subdiffusive behaviour. These experimental observations and the transition from Brownian to subdiffusive motion can be captured in a minimal phenomenological model.

Non-specific interactions govern cytosolic diffusion of nanosized objects in mammalian cells