Diffusion coefficients for rigid macromolecules with irregular shapes that allow rotational-translational coupling.

Area of Science:

• Fluid dynamics
• Physical chemistry
• Macromolecular science

Background:

• Understanding macromolecule movement in viscous fluids is crucial for various scientific fields.
• Low Reynolds number hydrodynamics governs the behavior of small or slow-moving objects like macromolecules.
• Translational and rotational motions are often coupled, but screwlike properties introduce unique complexities.

Purpose of the Study:

• To investigate six-dimensional diffusion and frictional tensors for rigid macromolecules in viscous fluids.
• To analyze the implications of screwlike properties on translational and rotational coupling.
• To develop a framework for calculating diffusion coefficients in complex systems.

Main Methods:

• Analysis of six-dimensional diffusion and frictional tensors.
• Perturbation analysis of the six-dimensional diffusion equation.
• Examination of symmetry conditions affecting diffusion and hydrodynamic centers.

Main Results:

• Screwlike properties can lead to distinct centers of diffusion and hydrodynamic reaction.
• The center of diffusion corresponds to the slowest diffusive movement point.
• Ignoring translational-rotational coupling underestimates the diffusion rate of screwlike particles.

Conclusions:

• A distinct center of diffusion from the hydrodynamic center is possible for screwlike bodies.
• Accurate calculation of diffusion coefficients requires accounting for translational-rotational coupling.
• The presented framework aids in determining diffusion coefficients for complex macromolecular structures.