Symmetry-based classification of forces driving chromatin dynamics.

Area of Science:

• Biophysics
• Cell Biology
• Polymer Physics

Background:

• Chromatin, the cell's DNA polymer, is immersed in nucleoplasmic fluid.
• Cellular processes generate active forces, leading to non-equilibrium conditions affecting chromatin organization and dynamics.
• The physical principles governing these active phenomena remain largely unexplored.

Purpose of the Study:

• To investigate the impact of different active force types on chromatin and nucleoplasm dynamics.
• To expand a two-fluid model by incorporating three distinct force dipole configurations.
• To understand emergent physical phenomena in active, non-equilibrium biological systems.

Main Methods:

• Development and analysis of a two-fluid model for chromatin and nucleoplasm.
• Inclusion of three distinct force dipole models representing cellular activity.
• Mathematical modeling to analyze fluid flows and emergent properties.

Main Results:

• A specific force dipole type, pushing chromatin and solvent in opposite directions, generates the most significant flows across various scales.
• Viscosity and inter-fluid friction lead to emergent screening length scales in active flows.
• The model predicts that distinct activity types and strengths influence hydrodynamic fluctuations.

Conclusions:

• Active forces are crucial drivers of chromatin and nucleoplasm organization and dynamics.
• The type and configuration of active forces significantly impact fluidic behavior within the nucleus.
• Analysis of hydrodynamic fluctuation power spectra can reveal details about nuclear active processes.