Hydrodynamic and electro-mechanical characterization of microtubules using light scattering*

Eukaryotic cells dynamically regulate the intracellular environment and modify the cytoskeleton filaments' biophysical properties to achieve specific biological functions, including neurological functions, cell division, and cell movement. In this presentation, we introduce a unique approach that combines (non-invasive) dynamic and electrophoresis light-scattering experiments and a statistical mechanics theory for polydisperse biopolymer systems to characterize the impact of the intracellular environment on the microtubules filament’s polydispersity, electric charge, and semi-flexibility in hydrodynamic conditions. A novel polymerization and light scattering measurement protocol produced consistent and reproducible results. Compared to those values obtained from molecular structure filament models, the lower value of the effective charge and the more significant value of the effective hydrodynamic size are due to a compact and stable “skin-like” ionic layer formation between the surrounding fluid and the filament surface. Contrasted with the values usually reported from (invasive) grid-stained samples and electron microscope conditions, the lower value of the bending and average contour filament length parameters values agreed with partial charge neutralization and the significant asymmetric growth rates at the filament ends. These results are essential to advance understanding of the biological functions of cytoskeleton filaments in biological environments.