Quantum chemical investigation of the titanium oxide-deoxyribonucleic acid interface.

摘要

Results from quantum mechanical calculations provide evidence of an energy based mechanism for detection of double-stranded DNA via photoinduced electron transfer in complexes containing TiO2 nanoparticles, trinucleotides and a dopamine methylacrylate modified thymine linker. Information about linker effects on electron transfer were examined in calculations of ionization energies of thymine functionalized at the C5 position with the truncated linker groups, methylacrylate (-CH=CHCO2CH3) and methylacrylamide (-CH=CHCONHCH 3). Results indicate that the addition of the carboxyl group to thymine and further modification with an amino group lowers the ionization potential. This result points out that bridging structures can be used to tune electron transfer in complexes employing thymine linkage through dopamine (DA).; Calculations of the binding energies and excitation energies of TiO 2-DA complexes provide evidence that covalent bidentate adsorption of dopamine on undercoordinated sites containing a Ti=O double bond is more stable than monodentate or molecular adsorption on the (101) anatase surface. Charge transfer associated with the lowest energy transition in the bidentate complexes involves promotion of an electron from the highest occupied molecular orbital on dopamine to low-lying unoccupied d orbitals on Ti atoms.; Calculations of the oxidation potentials of single- and double-stranded trinucleotides and bidentate TiO2-DA complexes indicate that the initial photoinduced charge separation with hole formation on dopamine leading to long-range charge separation with the hole residing in remote guanine bases is energetically allowed in double-stranded DNA but forbidden in single-stranded DNA.