Microscale electrostatics in mitosis

Abstract

Primitive cells had to divide using very few biological mechanisms. This work proposes physicochemical mechanisms, based upon microscale electrostatics, which explain and unify four basic events during mitosis: (1) assembly of the asters, (2) motion of the asters to poles, (3) poleward motion of chromosomes (anaphase A), and (4) cell elongation (anaphase B). In the cytoplasmic medium that exists in biological cells, electrostatic fields are subject to strong attenuation by ionic screening, and therefore decrease rapidly over a distance equal to several Debye lengths. However, the presence of microtubules within cells changes the situation completely. Microtubule dimer subunits are electric dipolar structures, and can act as intermediaries which extend the reach of the electrostatic interaction over cellular distances. Experimental studies have shown that intracellular pH rises to a peak at mitosis, and decreases through cytokinesis. This result, in conjunction with the electric dipole nature of microtubule subunits, is sufficient to explain the dynamics of the above motions, including their timing and sequencing. The physicochemical mechanisms utilized by primitive eukaryotic cells could provide important clues regarding our understanding of cell division in modern eukaryotic cells.