Biomedical subjects

Vera Müller

Publications and source records attributed to Vera Müller.

3 recordsLinked to original sources

PubMed2006

DFT models for copper(II) bispidine complexes: structures, stabilities, isomerism, spin distribution, and spectroscopy.

Various DFT and ab initio methods, including B3LYP, HF, SORCI, and LF-density functional theory (DFT), are used to compute the structures, relative stabilities, spin density distributions, and spectroscopic properties (electronic and EPR) of the two possible isomers of the copper(II) complexes with derivatives of a rigid tetradentate bispidine ligand with two pyridine and two tertiary amine donors, and a chloride ion. The description of the bonding (covalency of the copper-ligand interactions) and the distribution of the unpaired electron strongly depend on the DFT functional used, specifically on the nonlocal DF correlation and the HF exchange. Various methods may be used to optimize the DFT method. Unfortunately, it appears that there is no general method for the accurate computation of copper(II) complexes, and the choice of method depends on the type of ligands and the structural type of the chromophore. Also, it appears that the choice of method strongly depends on the problem to be solved. LF-DFT and spectroscopically oriented CI methods (SORCI), provided a large enough reference space is chosen, yield accurate spectroscopic parameters; EDA may lead to a good understanding of relative stabilities; accurate spin density distributions are obtained by modification of the nuclear charge on copper; solvation models are needed for the accurate prediction of isomer distributions.

Journal Article↗

PubMed2004

Interpretation of the temperature-dependent color of blue copper protein mutants.

The electronic absorption spectrum of the mutant of the blue copper protein amicyanin with a pseudoazurin loop (AmiPse) shows a remarkable temperature dependence. The absorption band at approximately 460 nm increases at low temperature while the transition at approximately 600 nm is not much affected by a variation of the temperature. An approximate density functional theory (DFT) study of the active site model [Cu(II)(imidazole)(2)(SCH(3))(S(CH(3))(2))](+) (protein backbone and solvation neglected) leads to two local minimum structures (axial and rhomb) which both have a geometry close to that typical for blue copper proteins. One (rhomb) has two structurally different histidine donors, and this geometry is also found in most experimental type 1 structures. The two forms axial and rhomb are distortional isomers and are energetically almost degenerate. The temperature dependence of the spectrum of AmiPse is interpreted with a temperature-dependent change of the relative population of the two local minimum structures with slightly different energy. The 460 nm transition is believed to be due to preferential population of the structure rhomb; this is in agreement with the published assignment of the high energy transition, based on thorough spectroscopic and computational studies. Consequences of a perturbation of the "gas phase" structures axial and rhomb by the protein and solvation are also discussed on the basis of published, experimentally observed structures and spectroscopic data.

Azurin↗

PubMed2002

Structural variation in transition-metal bispidine compounds.

The experimentally determined molecular structures of 40 transition metal complexes with the tetradentate bispyridine-substituted bispidone ligand, 2,4-bis(2-pyridine)-3,7-diazabicyclo[3.3.1]nonane-9-one [M(bisp)XYZ]n+; M = CrIII, MnII, FeII, CoII, CuII, CuI, ZnII; X, Y, Z = mono- or bidentate co-ligands; penta-, hexa- or heptacoordinate complexes) are characterized in detail, supported by force-field and DFT calculations. While the bispidine ligand is very rigid (N3...N7 distance = 2.933 +/- 0.025 A), it tolerates a large range of metal-donor bond lengths (2.07 A < sigma(M-N)/4 < 2.35 A). Of particular interest is the ratio of the bond lengths between the metal center and the two tertiary amine donors (0.84 A < M-N3/M-N7 < 1.05 A) and the fact that, in terms of this ratio there seem to be two clusters with M-N3 < M-N7 and M-N3 > or = M-N7. Calculations indicate that the two structural types are close to degenerate, and the structural form therefore depends on the metal ion, the number and type of co-ligands, as well as structural variations of the bispidine ligand backbone. Tuning of the structures is of importance since the structurally differing complexes have very different stabilities and reactivities.

Journal Article↗