Anomalous subdiffusion is a measure for cytoplasmic crowding in living cells.

• Macromolecular crowding dramatically affects cellular processes such as protein folding and assembly, regulation of metabolic pathways, and condensation of DNA. Despite increased attention, we still lack a definition for how crowded a heterogeneous environment is at the molecular scale and how this manifests in basic physical phenomena like diffusion. Here, we show by means of fluorescence correlation spectroscopy and computer simulations that crowding manifests itself through the emergence of anomalous subdiffusion of cytoplasmic macromolecules. In other words, the mean square displacement of a protein will grow less than linear in time and the degree of this anomality depends on the size and conformation of the traced particle and on the total protein concentration of the solution. We therefore propose that the anomality of the diffusion can be used as a quantifiable measure for the crowdedness of the cytoplasm at the molecular scale.

Nyckelord

Computer Simulation

Cytoplasm

chemistry

metabolism

Dextrans

chemistry

metabolism

Diffusion

Hela Cells

Humans

Macromolecular Substances

Models

Biological

Models

Chemical

Particle Size

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