Geraldo R. Friedermann

Genome of Herbaspirillum seropedicae Strain SmR1, a Specialized Diazotrophic Endophyte of Tropical Grasses

The molecular mechanisms of plant recognition, colonization, and nutrient exchange between diazotrophic endophytes and plants are scarcely known. Herbaspirillum seropedicae is an endophytic bacterium capable of colonizing intercellular spaces of grasses such as rice and sugar cane. The genome of H. seropedicae strain SmR1 was sequenced and annotated by The Paraná State Genome Programme—GENOPAR. The genome is composed of a circular chromosome of 5,513,887 bp and contains a total of 4,804 genes. The genome sequence revealed that H. seropedicae is a highly versatile microorganism with capacity to metabolize a wide range of carbon and nitrogen sources and with possession of four distinct terminal oxidases. The genome contains a multitude of protein secretion systems, including type I, type II, type III, type V, and type VI secretion systems, and type IV pili, suggesting a high potential to interact with host plants. H. seropedicae is able to synthesize indole acetic acid as reflected by the four IAA biosynthetic pathways present. A gene coding for ACC deaminase, which may be involved in modulating the associated plant ethylene-signaling pathway, is also present. Genes for hemagglutinins/hemolysins/adhesins were found and may play a role in plant cell surface adhesion. These features may endow H. seropedicae with the ability to establish an endophytic life-style in a large number of plant species.

The first hetero-binuclear alkoxide of iron and vanadium: structural and spectroscopic features

Abstract The immediate reaction between [V2(μ-OPri)2(OPri)6] (A) and [Fe2(μ-I)2I2(HOPri)4] (B) in toluene/propan-2-ol gives the novel mixed-metal [FeI2(μ-OPri)2V(OPri)2(HOPri)] (C). Structural, spectroscopic and magnetochemical characterisation are all consistent with a non-oxo vanadium(IV)/high-spin iron(II) formulation; variable-temperature X-band EPR spectra reveal an S=1/2↔S=1 equilibrium involving the vanadium centres in propan-2-ol solution.

2-Mercaptobenzoxazole pentacyanoferrate(II/III) complexes: UV-Visible, Mössbauer, electron paramagnetic resonance, electrochemistry and molecular modeling

2-Mercaptobenzoxazole pentacyanoferrate(II/III) complexes, [FeII/III(CN)5(bzoxs)]3-/2- , were prepared in MeOH/H2O 75:25% solutions and characterized by spectroscopic UV-Vis, Mossbauer, electron paramagnetic resonance (epr) and electrochemical-cyclic voltammetry- techniques. UV-Vis and epr spectra along with the electrochemical behavior suggested the coordination of the multi-functional N,S,O- donor ligand, bzoxs, to iron(III) through the sulfur atom. The crystal field parameters, DqL and Dt, calculated for the iron(II) complex, in addition to the reversible redox process FeIII-bzoxs + e- ® FeII-bzoxs also pointed to coordination via the sulfur atom. The results were compared with the chemical properties of pentacyanoferrate complexes containing other monodentate N-, S- and O-donor ligands. Ab initio calculations revealed the composition of the frontier orbitals of bzoxs and are in agreement with the mode of coordination proposed from the experimental data.

Metil coenzima M redutase (MCR) e o fator 430 (F430)

This review presents studies on methyl coenzyme M reductase, the biological system Factor 430 (F430) and the use of nickel(II) complexes as structural and functional models. The ability of F430 and nickel(II) macrocycle complexes to mediate the reductive dehalogenation of cyclohexyl halogens and the CH3-S bond cleavage of methyl CoM (by sodium borohydride and some intermediate species) proposed for the catalytic cycle of the biological system F430 was reviewed. The importance of the structure of the nickel complexes and the condition of the catalytic reduction reaction are also discussed.

Magneto-V1: um programa para o cálculo de correções diamagnéticas e de momentos magnéticos efetivos

A new computer program has been developed to help the users of force methods for magnetic moment determination. It provides a user-friendly interface for the calculation of corrected magnetic susceptibilities of paramagnetic materials and enables the user to simulate a number of chemical formulations for the sample under study. The program is written in the Perl scripting language and runs on a Unix platform.

Cr3+ Doped Al2O3 Obtained by Non-Hydrolytic Sol-Gel Methodology

This paper reports the synthesis and characterization of Cr-doped alumina by the sol-gel non-hydrolytic methodology. The resulting sample was treated at different temperatures. X-ray diffraction revealed that the ruby phase emerged in the sample treated at 1100 C, which was later confirmed by absorption bands correspondent to Cr ions allowed transitions at A2 → T1, T2, and forbidden at A2 → T1, E, observed by diffuse reflectance UV-Vis. The luminescence spectroscopy showed the intensity band at 694 nm in red region, characterized of the Cr ion. The peaks at 702 and 705 nm correspond to N1 and N2 lines, respectively, which arose from the second and fourth nearest-neighbor exchange-coupled pairs of chromium(III) ion, respectively, ascribed to high chromium(III) concentration. The Cr cluster formation was observed in electron paramagnetic resonance signal as discussed in this work. Nuclear magnetic resonance evidenced that the Al symmetry changed in the samples treated between 900 and 1100 C.

Iron(iii) and titanium(iv) oxoalkoxide chemistry: synthetic, structural, magnetochemical and spectroscopic studies of [Ti3(3-OPri)2(-OPri)3(OPri)6][FeCl4] and [Fe5(5-O)(-OPri)8Cl5]Electronic supplementary information (ESI) available: crystallographic data in Tables 5 and 6, and ORTEP-3 representation of the molecular structure of complex C?. See http://www.rsc.org/suppdata/nj/b4/b403899a/

Two synthetic routes were employed for the preparation of iron(III) haloalkoxides in the presence of titanium(IV). Three crystalline products (A, B and C) were isolated and characterised by chemical and physical techniques including X-ray diffractometry, Mossbauer and EPR spectroscopies and variable-temperature magnetic susceptibility measurements. Products B and C are common to both synthetic routes. Product A is a mononuclear iron(II) complex, trans-[FeCl2(HOPri)4], probably produced by the oxidation of propan-2-ol by FeCl3 in the reaction medium. B is the ionic, mixed-metal [Ti3(μ3-OPri)2(μ-OPri)3(OPri)6][FeCl4], while C is a high-yield oxo-haloalkoxide, [Fe5(μ5-O)(μ-OPri)8Cl5]. Magnetic moment measurements in [2H8]-tetrahydrofuran solution from 323 to 173 K indicate that C contains antiferromagnetically coupled iron(III) centres with intermediate (S = 3/2) spin configuration. C is polymorphic in the solid state, crystallising in the monoclinic or the tetragonal systems as non- and mono-solvate species, respectively. The highly (Lewis) acidic character of iron(III), together with its oxophilic character, probably determined the formation of B and C instead of the targeted mixed-metal [FeIIICl(2 − x){Ti2(OPri)(9 + x)}], x = 0 or 1. The possibility of formation of heteronuclear alkoxides containing both iron(III) and titanium(IV) is re-assessed in the light of the results obtained in this work.