Nanochemistry and biotechnology

Cholinergic excitation of the gastrointestinal tract smooth muscles due to the action of nanostructured TiO2, and its molecular docking to the extracellular parts of muscarinic acetylcholine receptors M2 and M3 types
Naumenko A.M.1, Tsymbalyuk O.V.1, Voiteshenko I.S.1, Davydovska T.L.1 
1 Department of Molecular Biotechnology and Bioinformatics, Institute of High Technologies, Taras Shevchenko National University of Kyiv, 64/13, Volodymyrska Street, City of Kyiv, Ukraine, 01601. 
E-mail: ganna.naumenko@gmail.com

Using tenzometric method in isometric mode it was shown that ТіО2 suspensions with nanoparticles, sized (4-8) and (1-3) nm, change the spontaneous contraction cycles’ structure for stomach smooth muscles of rats’ antrum with the decrease in their total efficiency. There was also a change in the kinetic parameters of high potassium contractions and the contractions, induced by acetylcholine – the mediator of muscarinic acetylcholine M2 type receptors, with the impairment of the coordinating processes of contractions and relaxations velocities, which are more expressed in the first case at the effect of ТіО2 (1-3) nm, and in the second one – (4-8) nm. 
The molecular docking of ТіО2 to the extracellular part of the muscarinic acetylcholine M2 type receptor demonstrated the possibility of forming the bonds with some amino acids of the site of its allosteric modulator, which affects the affinity of this receptor to orthosteric ligands. The TiO2 binding site does not compete for the binding sites of this type acetylcholine receptor neurotransmitter by its amino acid composition. Molecular docking of TiO2 to the muscarinic acetylcholine M3 type receptor showed that there are common amino acids residues for both the nanoparticle and acetylcholine with which bonds are formed in the orthosteric binding site.