A computational study on DNA bases interactions with dinuclear tetraacetato-diaqua-dirhodium(II,II) complex

Quantum mechanical study of transition metal hydrides: Comparison of determined molecular properties with experimental data

This study compares results of four relativistic pseudopotential basis sets, which differ mainly by their size: double-zeta introduced by Hay and Wadt from Los Alamos National Laboratory (LANL2DZ), triple-zeta based on Stuttgart energy-consistent scalar-relativistic pseudopotential (SDD3), its extension with 2fg polarization functions, and combination of Stuttgart pseudopotentials with quintuple-zeta cc-pV5Z base (SDD5). Hydrides of transition metals from Cr to Zn group are chosen as reference molecules. The coupled cluster method (CCSD(T)) is used for evaluation of selected molecular characteristics. Interatomic distances, dissociation energies, vibration modes, and anharmonicity constants are determined and compared with available experimental data. As expected, the accuracy of basis depends mainly on its size. However, only moderate modification of SDD3 basis set significantly improves its accuracy, which becomes comparable to the largest basis set. Nevertheless, the time consumption is significantly lower.

Unexpected Imidazole Coordination to the Dirhodium Center in a Protein Environment: Insights from X-ray Crystallography and Quantum Chemistry

X-ray diffraction data demonstrate that the adduct formed upon the reaction of dirhodium(II,II) tetraacetate with RNase A reacts with imidazole, leading to the formation of an unexpected product with the imidazole that binds the dirhodium center at an equatorial site rather than an axial site. The origin of this result has been dissected using quantum-chemical calculations.

The dirhodium(II,II) tetraacetate/RNase A adduct reacts with imidazole, leading to the formation of an unexpected product with the imidazole that binds the dirhodium center at an equatorial site rather than an axial site. The origin of this result has been dissected using quantum-chemical calculations.

Tuning the Optical Properties of Novel Antitumoral Drugs Based on Cyclometalated Iridium(III) Complexes

Most of the current efforts in drug discovery are devoted to the design of molecules able to mitigate side effects by concentrating the biological action in the targeted tissue. One promising strategy is photodynamic therapy, which is based on the in situ generation of reactive singlet oxygen upon radiation exposure. However, such an approach requires the use of an efficient photosensitizer. This contribution deals with the optical properties of an Ir(III) complex, [Ir(pbz)₂(N^N)] (pbz = 2-phenylbenzimidazole; N^N = methyl 1-butyl-2-pyridyl-benzimidazole-5-carboxylate), which has recently been shown to exhort a strong photoactivity, but still needs further improvements to reach clinical applications. We performed density functional theory calculations at the M06, PBE0, ωB97xD, and CAM-B3LYP levels to predict the impact of introducing electron donor-acceptor groups into the nature of the lowest excited states. The simulations performed demonstrate that the presence of a NH₂ at the pbz ligand and a NO₂ group at the N^N ligand yield a bathochromic shift of absorption spectrum. We report the most sensitive positions to tune the optical signatures of this family of complexes.

Development and applications of two colorimetric and fluorescent indicators for Hg2+ detection

Two rhodamine-active probes RBAI (Rhodamine B-di-Aminobenzene-phenyl Isothiocyanate) and RGAI (Rhodamine 6G-di-Aminobenzene-phenyl Isothiocyanate) were designed, synthesized and characterized. The probes were developed as fluorescent and colorimetric chemodosimeters in ethanol-water solution with a broad pH span (5-10) and high selectivity toward Hg²⁺ but no significant response toward other common competitive cations. The Hg²⁺-promoted ring opening of spirolactam of the rhodamine moiety induced cyclic guanylation of the thiourea moiety, which resulted in the dual chromo- and fluorogenic observation (off-on). Cytotoxicity and bioimaging studies by L929 living cells and living mice indicated that the probes were negligible cytotoxicity, cell permeable and suitable for detecting Hg²⁺ in biological environments. Moreover, the new probes not only displayed excellent abilities for the successful detection of Hg²⁺ in L929 living cells and living mice but also able to detect Hg²⁺ by adsorbing on solid surfaces and quantitative detection of Hg²⁺ in real water samples with good recovery (more than 90%), indicating that they have promising prospect for application for Hg²⁺ sensing in environmental and biological sciences.

Electronic and molecular structure of M-DNA fragments

To study M-DNA molecular structure (such DNA with transition metal ions placed between the nucleic bases is able to conduct the electric current) and its conductivity mechanisms, we carried out ab initio quantum-mechanical calculations of electronic and spatial structures, thermodynamic characteristics of adenine-thymine (АТ) and guanine-cytosine (GC) base pair complexes with Zn(2+) and Ni(2+). To take into account the influence of the alkaline environment, calculations for these complexes were also carried out with hydroxyl and two water molecules. Computations were performed at MP2 level of theory using 6-31+G* basis set. Analogous calculations were carried out for (AC)(TG) stacking dimer of nucleic acid base pairs with two Zn(2+). The calculation of the interaction energy in complexes has shown the preference of locating the metal ion (instead of the imino proton) between bases in M-DNA. The electronic transition energy calculation has revealed the reduction of the first singlet transition energy in АТ and GC complexes with Ni(2+) from 4.5 eV to 0.4 - 0.6 eV. Ni(2+) orbitals take part in the formation of HOMO and LUMO on the complexes investigated. It was shown that charges of metal ions incorporated into complexes with nucleic bases and in dimer decrease significantly.