Ab Initio Molecular Dynamics Study of the Effect of an Mg~(2+) Cation in the Triplet and Singlet States on the Properties of Tubulin

摘要

The effect of an Mg~(2+) cation on the properties of tubulin was studied by quantum-chemical methods (the DFT-B3LYP QM/MM method with the basis set 6-31G** + ab initio molecular dynamics (MD)). Hydration of GTP (guanosine triphosphate)-tubulin determines the band structure of the protein, which involves the band filled with electrons and the conduction band. The binding of Mg~(2+) to GTP incorporated in tubulin leads to "impairing" of electrons in the occupied band (formation of the triplet (T) state) followed by their transfer to the conduction band, in which spin flip takes place (formation of the singlet (S) state). The transfer of tubulin to the T state gives impetus to a change in the state of the protein on a picosecond time scale. The dynamics of the process is manifested in the oscillating transition of tubulin from the T to the S state and back due to continuous adjustment of its nuclear and electronic configurations (ab initio MD calculations). The barrier between the T and S states does not exceed 0.60 kcal/mol. The overcoming of the barrier can be treated as electron transfer through the Fermi surface, which separates the occupied band and the conduction band.