Small angle neutron/x-ray scattering study of microtubules and polycations

Microtubules (MTs) are hollow cylindrical protein nanotubes with 25 nm diameter, composed of α/β-tubulin heterodimers with surface charge density ~ e/nm². They are involved in many cellular functions such as cell division, maintaining cell shape, and intracellular trafficking. There have been studies about higher-order assemblies of MTs (e.g. Hexagonal bundle of MTs, inverted tubulin tubes, etc) in the presence of multivalent cations (e.g. Ca²⁺, spermine, etc). We show our recent findings on the assembly structures of MTs and cationic polymers, which have different structures as the concentration of the polycations changes. Various assemblies are studied both in real and reciprocal spaces using small angle Neutron/X-ray scattering and transmission electron microscopy.