The functional role of the structure of the dioxo-isobacteriochlorin in the catalytic site of cytochrome cd for the reduction of nitrite.

Cytochrome cd is a key enzyme in bacterial denitrification and catalyzes one-electron reduction of nitrite (NO) to nitric oxide (NO) at the heme d center under anaerobic conditions. The heme d has a unique dioxo-isobacteriochlorin structure and is present only in cytochrome cd. To reveal the functional role of the unique heme d in the catalytic nitrite reduction, we studied effect of the porphyrin macrocycle on each reaction step of the catalytic cycle of cytochrome cd using synthetic model complexes.

Communication: Explicitly correlated four-component relativistic second-order Møller-Plesset perturbation theory.

We propose explicitly correlated Ansatz for four-component relativistic methods within the framework of the no-pair approximation. Kinetically balanced geminal basis is derived to satisfy the cusp conditions in the non-relativistic limit based on the Lévy-Leblend-like equation. Relativistic variants of strong-orthogonality projection operator (Ansätze 2α and 2β) suitable for practical calculations are introduced by exploiting the orthogonal complement of the large-component basis.

Effect of the axial ligand on the reactivity of the oxoiron(IV) porphyrin π-cation radical complex: higher stabilization of the product state relative to the reactant state.

The proximal heme axial ligand plays an important role in tuning the reactivity of oxoiron(IV) porphyrin π-cation radical species (compound I) in enzymatic and catalytic oxygenation reactions. To reveal the essence of the axial ligand effect on the reactivity, we investigated it from a thermodynamic viewpoint. Compound I model complexes, (TMP(+•))Fe(IV)O(L) (where TMP is 5,10,15,20-tetramesitylporphyrin and TMP(+•) is its π-cation radical), can be provided with altered reactivity by changing the identity of the axial ligand, but the reactivity is not correlated with spectroscopic data (ν(Fe═O), redox potential, and so on) of (TMP(+•))Fe(IV)O(L).

Versatile supramolecular gelators that can harden water, organic solvents and ionic liquids.

We developed novel supramolecular gelators with simple molecular structures that could harden a broad range of solvents: aqueous solutions of a wide pH range, organic solvents, edible oil, biodiesel, and ionic liquids at gelation concentrations of 0.1-2 wt %. The supramolecular gelators were composed of a long hydrophobic tail, amino acids and gluconic acid, which were prepared by liquid-phase synthesis.

Evaluation of electron population terms for 4p, 3p, and (2p): how do HOMO and LUMO shrink or expand depending on nuclear charges?

Electron population terms are evaluated for N=Se, S, and O. Calculations are performed on HOMO and LUMO constructed by pure atomic 4p(Se), 3p(S), and 2p(O) orbitals, employing the 6-311+G(3d) and/or 6-311(++)G(3df,3pd) basis sets at the HF, MP2, and DFT (B3 LYP) levels. Se(4+), Se(2+), Se(0), and Se(2-) with the O(h) symmetry are called G(A: Se) and HSe(+), H(2)Se, and HSe(-) with the C(infinityh) or C(2v) symmetry are named G(B: Se), here [G(A+B: Se) in all].

Basis set limits of the second order Moller-Plesset correlation energies of water, methane, acetylene, ethylene, and benzene.

We report second order Moller-Plesset (MP2) and MP2-F12 total energies on He, Ne, Ar, H(2)O, CH(4), C(2)H(2), C(2)H(4), and C(6)H(6), using the correlation consistent basis sets, aug-cc-pVXZ (X=D-7). Basis set extrapolation techniques are applied to the MP2 and MP2-F12/B methods. The performance of the methods is tested in the calculations of the atoms, He, Ne, and Ar.

The extension of the fragment molecular orbital method with the many-particle Green's function.

By using the many-particle Green's function (GF) the extension of the fragment molecular orbital (FMO) method by Kitaura et al. [Chem. Phys.

Simple minimum principle to derive a quantum-mechanical/molecular-mechanical method.

We propose a minimum principle to derive a QM/MM (quantum-mechanical/molecular-mechanical) method from the first principle. We approximate the Hamiltonian of a spectator substituent as the structure-dependent effective Hamiltonian in a least-squares sense. This effective Hamiltonian is expanded with the orthogonal operator set called the normal-ordered product.