The cytoskeleton, a dynamic and intricate network of protein filaments, is found within the cytoplasm of all cells, from bacteria and archaea to complex eukaryotes. This essential cellular component …

Scientists have identified tubulin structures in primitive Asgard archea that may have been the precursor of our own cellular skeletons.

Self-organized criticality can occur in cellular systems, but its origins remain unclear. Now it is shown that cytoskeletal criticality is influenced by the F-actin architecture and myosin active stre...

Understanding of the dynamics inherent to biological matter is crucial for illuminating the physical mechanisms underlying cellular processes. In this study, we employ bright-field differential dynamic microscopy (DDM) to investigate density fluctuations inherent in a cell-free model of eukaryotic cytoplasm. Our measurements reveal subdiffusive fractional Brownian motion and non-Gaussian displacement distributions, highlighting cytoplasmic heterogeneity. We introduce an empirical model that combines fractional Brownian motion with an inverse Gaussian distribution of diffusivities to describe the observed non-Gaussianity. Validated through Monte Carlo simulations, this model allows us to estimate the fractional diffusivity and exponent effectively. By altering macromolecular composition, the addition of energy, and assembly of a cytoskeleton, we identify three independent mechanisms that result in similar fractional exponents yet distinct diffusivities. We find that energy addition leads to non-stationary dynamics, in contrast to the stationary behavior observed under passive conditions. Presence of microtubules introduces a secondary dynamical timescale, which we describe using a two-state fractional Brownian motion model to differentiate between cytosolic and microtubule network associated contributions. Our findings demonstrate the effectiveness of DDM as a label-free tool for quantifying viscoelastic and heterogeneous properties of the cytoplasm and provide insights into how physical and biochemical factors, including cytoskeletal organization, govern subcellular dynamics. ### Competing Interest Statement The authors have declared no competing interest.

President Trump’s immigration crackdown ensnared Kseniia Petrova, a scientist who fled Russia after protesting its invasion of Ukraine. She fears arrest if she is deported there.

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