Formation of a stable cyano-bridged dinuclear iron cluster following oxidation of the superoxide reductases from Treponema pallidum and Desulfovibrio vulgaris with K(3)Fe(CN)(6)

Superoxide reductases catalyze the monovalent reduction of superoxide anion to hydrogen peroxide. Spectroscopic evidence for the formation of a dinuclear cyano-bridged adduct after K(3)Fe(CN)(6) oxidation of the superoxide reductases neelaredoxin from Treponema pallidum and desulfoferrodoxin from Desulfovibrio vulgaris was reported. Oxidation with K(3)Fe(CN)(6) reveals a band in the near-IR with lambda(max) at 1020 nm, coupled with an increase of the iron content by almost 2-fold. Fourier transform infrared spectroscopy provided additional evidence with CN-stretching vibrations at 2095, 2025-2030, and 2047 cm(-)(1), assigned to a ferrocyanide adduct of the enzyme. Interestingly, the low-temperature electronic paramagnetic resonance (EPR) spectra of oxidized TpNlr reveal at least three different species indicating structural heterogeneity in the coordination environment of the active site Fe ion. Given the likely 6-coordinate geometry of the active site Fe(3+) ion in the ferrocyanide adduct, we propose that the rhombic EPR species can serve as a model of a hexacoordinate form of the active site.     

Spin-other-orbit interaction in highly excited configurations with p and g electrons in outer shells

The matrix of the operator of the spin-other-orbit interaction energy is constructed for npn’g and np ⁵ n’g configurations. The matrix elements of this operator are calculated in the single-configuration approximation with wave functions in the LSJM representation and in the representation of uncoupled angular momenta using the known general formulas. The spin-other-orbit interaction is represented by three direct and three exchange radial Marvin spin interaction integrals.     

4-(4-Acethylphenyl)-3-hydroxycoumarin in the Synthesis of Nitrogen-containing Heterocycles with a Neoflavonoid Moiety

Russian Journal of Organic Chemistry - 4-(4-Acetylphenyl)-3-hydroxy-2H-chromen-2-one has been prepared by the reaction of (4-acetylbenzene)diazonium chloride with 3-hydroxy-2H-chromen-2-one under...     

Static dielectric constants and molecular dipole distributions of liquid water and ice-Ih investigated by the PAW-PBE exchange-correlation functional

The static dielectric constants, ε(s), of ice-Ih and liquid water were calculated using density functional theory with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional and the projector-augmented-wave (PAW) approach. Proton disordered ice configurations and uncorrelated liquid configurations were sampled with the electrostatic switching method using force fields specially designed to facilitate the ab initio free energy perturbation calculations. Our results indicate that PAW-PBE underestimates the ε(s) of both ice-Ih and liquid water but predicts the ratio of ice and water ε(s) in good agreement with experimental measurements. PAW-PBE gives average water dipole moments of 2.50 D in ice-Ih and 2.48 D in the liquid. Our results show that the fixed-charge water models developed by adaptive force matching can reproduce the PAW-PBE dipole moments with an error of approximately 5%. The ice and liquid models created in this work have polarizabilities of 1.32 ?(3) and 1.30 ?(3), respectively, along the HOH bisector direction.     

Synthesis and Electronic Transitions of the Dye Based on 1-{2-[4-(3-Hydroxy-2-oxo-2H-chromen-4-yl)phenyl]-2-oxoethyl}-4-methylpyridinium Bromide

Russian Journal of General Chemistry - 4-[4-(2-Bromoacetyl)phenyl]-3-hydroxy-2H-chromen-2-one reacted with pyridine and 4-methylpyridine to give the corresponding quaternary pyridinium salts. The...     

Rate of convergence bound for approximating sequences in minimization problems for functionals

A general approximation scheme for minimization of functionals in a Banach space is considered. Inequalities are proved which supply bounds on the rate of convergence of the approximate solutions to the exact solution. These bounds are applied to an optimal control problem for an abstract operator equation in a Hilbert space with control in the right-hand side.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 59, pp. 117–121, 1986.     

Two-point fermion correlation functions at finite density

The general form of two-point fermion correlation functions at finite density is examined. Examples of particular interest are correlation functions of nucleonic interpolating fields, used in QCD sum-rule studies, and nucleon propagators in hadronic field theories. The constraints of Lorentz covariance, parity, and time-reversal on the form of the correlators are derived by focusing on spectral functions. Discrepancies with other treatments in the literature are discussed.     

Correlation between isoniazid resistance and superoxide reactivity in mycobacterium tuberculosis KatG

Isoniazid is an antituberculosis prodrug that requires activation by the catalase-peroxidase (KatG) of Mycobacterium tuberculosis. The activated species, presumed to be an isonicotinoyl radical, couples to NADH forming an isoniazid-NADH adduct that ultimately confers antitubercular activity. We have compared the catalytic properties of three KatGs associated with isoniazid resistance (resistance mutation KatGs, (RM)KatGs: R104L, H108Q, S315T) to wild-type enzyme and two additional lab mutations (wild-type phenotype KatGs, (WTP)KatGs: WT KatG, Y229F, R418L). Neither catalase nor peroxidase activities, nor the presence/absence of the Met-Tyr-Trp cross-link (as probed by LC/MS on tryptic digests of the protein), exhibited any correlation with isoniazid resistance. The yields of isoniazid-NADH adduct formed were determined to be 1-5, 4-12, and 20-70-fold greater for the (WTP)KatGs than the (RM)KatGs for the compound I, II, and III pathways, respectively, strongly suggesting a role for oxyferrous KatG (supported by superoxide consumption measurements) that correlates with drug resistance. Stopped-flow UV-visible spectroscopic studies revealed that all KatGs were capable of forming both compound II and III intermediates. Rates of compound II decay were accelerated 4-12-fold in the presence of isoniazid (vs absence) for the (WTP)KatGs but were unaffected by the drug for the (RM)KatGs. A mechanism for isoniazid resistance which accounts for the observed reactivity for each of the compound I, II, and III intermediates is proposed and suggests that the compound III pathway may be the primary factor in determining overall isoniazid resistance by specific KatG mutants, with secondary contributions arising from the compound I and II pathways.