DOI: 10.14704/nq.2008.6.3.188

Quantum Mechanical Control of Artificial Minimal Living Cells

Arvydas Tamulis

Abstract


Artificial minimal living cells and their substructures are quantum mechanically self-assembling due to competition of weak electrostatic forces and weak attraction Van der Waals dispersion forces, and hydrogen bonds originated due to electron correlation interactions among biological and water molecules. The best available method to simulate in minimal cells these weak electrostatic and Van der Waals dispersion forces, and hydrogen bonds is to perform quantum mechanical non-local density functional potential calculations of artificial minimal living cells consisting of around 400 atoms. The cell systems studied are based on peptide nucleic acid and are 3.0 – 4.5 nm in diameter. The electron tunneling and associated light absorption of most intense transitions as calculated by the time dependent density functional theory method (TD DFT) differs from spectroscopic experiments by only 0.3 nm, which are within the value of experiment errors. This agreement implies that the quantum mechanically self-assembled structure of artificial minimal living cells very closely approximate the realistic ones.
Analysis of TD DFT method calculated absorption spectrum and images of electron transfer trajectories in the different excited states allow to separate two different logically controlled functions of molecular device consisting of guaninecytosine-PNA-1,4-dihydroquinoxaline-1,4-bis(N,N-dimethylamino)naphthalene supermolecule and Van der Waals bonded precursor of fatty acid molecule. These two different logically controlled functions of artificial minimal living cells are: 1) initiation of metabolic fatty acid production in five excited states or 2) initiation of gene dehybridization in one excited state. This designed supermolecule works in the artificial minimal cell as molecular electronics classic OR logic function (Boolean logics OR gate).
TD DFT were used to investigate various photoactive systems of artificial minimal cells based on Ru(bipyridine)32+ sensitizer. The electron correlation interactions associated with the weak Van der Waals and hydrogen bonds increase due to the addition of a polar solvent (water or methanol) shells. The addition of precursor fatty acid or cytosine molecules plays a role in the quantum mechanical interaction based self-assembly of the photosynthetic center and the functioning of the photosynthetic processes of the artificial minimal cells. As a result the associated nonlinear quantum interactions compress the overall system resulting in an even smaller gap between the HOMO and LUMO electron energy levels and photoexcited electron tunneling occurs from the sensitizer (covalently bonded 8-oxo-guanine molecule to the [Ru(bpy)2(4-Bu-4'-Me-2,2'-bpy)]2+) to pFA molecule (notation used: Me = methyl; Bu = butyl; bpy = bipyridine). The electron tunneling and associated light absorption for the most intense transitions as calculated by the TD DFT method are within the values of experiment errors.

Keywords


artificial minimal living cells; photoexcited electron tunneling; molecular electronics logical gate

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