Biomedical subjects

Ming-Ju Huang

Publications and source records attributed to Ming-Ju Huang.

6 recordsLinked to original sources

PubMed2006

DFT/TDDFT study of lanthanide(III) mono- and bisporphyrin complexes.

The electronic structure, molecular structure, and electronic spectra of lanthanide(III) mono- and bisporphyrin complexes are investigated using a DFT/TDDFT method. These complexes include YbP(acac), YbP(2), [YbP(2)](+), YbHP(2), and [YbP(2)](-) (where P = porphine and acac = acetylacetonate). To shed some light on the origin of the out-of-plane displacement of Yb in YbP(acac), unligated model systems, namely, planar D(4h) and distorted C(4nu) YbP, were calculated. For comparison, the calculations were also extended to include the C and [Ce(IV)P(2) ](+) systems. Even without an axial ligand, the lanthanide atom lies considerably above the porphyrin plane; the distortion of the YbP molecular structure from a planar D(4h) to the nonplanar C(4nu) symmetry leads to a considerable energy lowering. The axial ligand makes the metal out-of-plane displacement even larger, and it also changes the redox properties of the lanthanide monoporphyrin. The ground-state configurations of YbP(2) and YbHP(2) were determined by considering several possible low-lying states. YbP(2) is confirmed to be a single-hole radical. The special redox properties of the bisporphyrin complexes can well be accounted for by the calculated ionization potentials and electron affinities. The TDDFT results provide a clear description of the UV-vis and near-IR absorption spectra of the various lanthanide porphyrins.

Cerium↗

PubMed2006

Assessment of the performance of density-functional methods for calculations on iron porphyrins and related compounds.

The behaviors of a large number of GGA, meta-GGA, and hybrid-GGA density functionals in describing the spin-state energetics of iron porphyrins and related compounds have been investigated. There is a large variation in performance between the various functionals for the calculations of the high-spin state relative energies. Most GGA and meta-GGA functionals are biased toward lower-spin states and so fail to give the correct ground state for the high-spin systems, for which the meta-GGA functionals show more or less improvement over the GGA ones. The GGA functionals that use the OPTX correction for exchange show remarkably high performance for calculating the high-spin state energetics, but their results for the intermediate-spin states are somewhat questionable. A heavily parameterized GGA functional, HCTH/407, provides results which are in qualitative agreement with the experimental findings for the iron porphyrins [FeP, FeP(Cl), FeP(THF)2], but its relative energies for the high-spin states are probably somewhat too low. The high-spin state relative energies are then even more underestimated by the corresponding meta-GGA functional tau-HCTH. For the hybrid-GGA functionals, the Hartree-Fock (HF)-type (or exact) exchange contribution strongly stabilizes the high-spin states, and so the performance of such functionals is largely dependent upon the amount of the HF exchange admixture in them. The B3LYP, B97, B97-1, and tau-HCTH-hyb functionals are able to provide a satisfactory description of the energetics of all the systems considered.

Iron↗

PubMed2005

Effects of peripheral substituents and axial ligands on the electronic structure and properties of cobalt porphyrins.

The effects of peripheral substituents and axial ligands (L) on the electronic structure and properties of cobalt tetraphenylporphyrin (CoTPP) have been studied using DFT methods. Various density functionals were tested, and the ground state of each system was determined by considering several possible low-lying states. The ground states of the fully fluorinated CoTPPF28(L)2 complexes with L = THF, Py, and Im were identified to be high-spin (4E(g)) by the meta-GGA functional tau-HCTH, which contains the kinetic energy density tau, in agreement with experimental measurements. All the pure GGA functionals, including the recently developed mPBE, OPBE, and HCTH/407, show more or less overestimation of the relative energies of the high-spin states. The energy gap between the 2A(1g) and 4E(g) states is insignificant (approximately 0.1 eV) and varies in the order L = Py < L = THF < L = Im. The results and their trend are consistent with 19F NMR studies which show partial population of the 4E(g) state in CoTPPF28(THF)2 and CoTPPF28(Py)2 and a complete conversion to the high-spin state in CoTPPF28(1-MeIm)2. Upon coordination by two very strong field axial CO ligands, CoTPPF28(CO)2 becomes low-spin, as in unligated CoTPPF(x). The influence of the peripheral substituents and axial ligands on the ionization potentials, electron affinities, and CoTPPF(x)-(L)2 binding strength was also investigated in detail.

Algorithms↗

PubMed2005

Fe(II) in different macrocycles: electronic structures and properties.

A theoretical comparative study of complexes of porphyrin (P), porphyrazine (Pz), phthalocyanine (Pc), porphycene (Pn), dibenzoporphycene (DBPn), and hemiporphyrazine (HPz) with iron (Fe) has been carried out using a density functional theory (DFT) method. The difference in the core size and shape of the macrocycle has a substantial effect on the electronic structure and properties of the overall system. The ground states of FeP and FePc were identified to be the 3A2g [(d(xy))2(d(z)2)2(d(pi))2] state, followed by 3E(g) [(d(xy))2(d(z)2)1(d(pi))3]. For FePz, however, the 3E(g)-3A2g energy gap of 0.02 eV may be too small to distinguish between the ground and excited states. When the symmetry of the macrocycle is reduced from D4h to D2h, the degeneracy of the d(pi) (d(xz), d(yz)) orbitals is removed, and the ground state becomes 3B2g [(d(xy))2(d(z)2)1(d(yz))2(d(xz))1] or 3B3g [...(d(yz))1(d(xz))2] for FePn, FeDBPn, and FeHPz. The calculations also show how the change of the macrocycle can influence the axial ligand coordination of pyridine (Py) and CO to the Fe(II) complexes. Finally, the electronic structures of the mono- and dipositive and -negative ions for all the unligated and ligated iron macrocycles were elucidated, which is important for understanding the redox properties of these compounds. The differences in the observed electrochemical (oxidation and reduction) properties between metal porphycenes (MPn) and metal porphyrins (MP) can be accounted for by the calculated results (orbital energy level diagrams, ionization potentials, and electron affinities).

Iron↗

PubMed2005

DFT study of unligated and ligated manganese(II) porphyrins and phthalocyanines.

A theoretical study of the electronic structure, bonding, and properties of unligated and ligated manganese(II) porphyrins and phthalocyanines has been carried out "in detail" using a density functional theory (DFT) method. While manganese tetraphenylporphine (MnTPP) in the crystal is high spin (S = 5/2) with the Mn(II) atom out of the porphyrin plane, the present calculations find that the free manganese porphine (MnP) molecule has no obvious tendency to distort from planarity even in the high-spin state. The ground state of the planar structure is found to be intermediate spin (S = 3/2). Manganese phthalocyanine (MnPc) is calculated to have a 4E(g) ground state, in agreement with the more recent magnetic circular dichroism (MCD) and UV-vis measurements of the molecule in an argon matrix but different from the early magnetic measurements of solid MnPc. The effect of the crystal structure on the electronic state of MnPc is examined by the calculations of a model system. For the six-coordinate adducts with two pyridine (py) ligands, the strong-field axial ligands raise the energy of the Mn d(z2)-orbital, thereby making the Mn(II) ion low spin (S = 1/2). The recent assignment of MnPc(py)2 as an intermediate-spin state proves to be incorrect. Some issues involved in the reduced products have also been clarified. Five-coordinate MnP(py) and MnPc(py) complexes are high spin and intermediate spin, respectively.

Electron Spin Resonance Spectroscopy↗

PubMed2005

Application of quantitative structure activity relationship (QSAR) models to predict ozone toxicity in the lung.

The sequence of events leading to ozone-induced airway inflammation is not well known. To elucidate the molecular and cellular events underlying ozone toxicity in the lung, we hypothesized that lipid ozonation products (LOPs) generated by the reaction of ozone with unsaturated fatty acids in the epithelial lining fluid and cell membranes play a key role in mediating ozone-induced airway inflammation. To test our hypothesis, we ozonized 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) and generated LOPs. Confluent human bronchial epithelial cells were exposed to the derivatives of ozonized POPC-9-oxononanoyl, 9-hydroxy-9-hydroperoxynonanoyl, and 8-(5-octyl-1,2,4-trioxolan-3-yl-)octanoyl-at a concentration of 10 muM, and the activity of phospholipases A2 (PLA2), C (PLC), and D (PLD) was measured (1, 0.5, and 1 h, respectively). Quantitative structure-activity relationship (QSAR) models were utilized to predict the biological activity of LOPs in airway epithelial cells. The QSAR results showed a strong correlation between experimental and computed activity (r = 0.97, 0.98, 0.99, for PLA2, PLC, and PLD, respectively). The results indicate that QSAR models can be utilized to predict the biological activity of the various ozone-derived LOP species in the lung.

Cell Line↗