Unexpected electron spin density on the axial methionine ligand in CuA suggests its involvement in electron pathways.

The CuA center is a paradigm for the study of long-range biological electron transfer. This metal center is an essential cofactor for terminal oxidases like cytochrome c oxidase, the enzymatic complex responsible for cellular respiration in eukaryotes and in most bacteria. CuA acts as an electron hub by transferring electrons from reduced cytochrome c to the catalytic site of the enzyme where dioxygen reduction takes place. Different electron transfer pathways have been proposed involving a weak axial methionine ligand residue, conserved in all CuA sites. This hypothesis has been challenged by theoretical calculations indicating the lack of electron spin density in this ligand. Here we report an NMR study with selectively labeled methionine in a native CuA. NMR spectroscopy discloses the presence of net electron spin density in the methionine axial ligand in the two alternative ground states of this metal center. Similar spin delocalization observed on two second sphere mutants further supports this evidence. These data provide a novel view of the electronic structure of CuA centers and support previously neglected electron transfer pathways.

Simulation of mesogenic diruthenium tetracarboxylates: Development of a force field for coordination polymers of the MMX type.

A classical molecular mechanics force field, able to simulate coordination polymers (CP) based on ruthenium carboxylates (Ru2 (O2CReq )4 Lax) (eq = equatorial group containing aliphatic chains, Lax = axial ligand), has been developed. New parameters extracted from experimental data and quantum calculations on short aliphatic chains model systems were included in the generalized AMBER force field. The proposed parametrization was evaluated using model systems with known structure, containing either short or long aliphatic chains; experimental results were reproduced satisfactorily. This modified force field, although in a preliminary stage, could then be applied to long chain liquid crystalline compounds. The resulting atomistic simulations allowed assessing the relative influence of the factors determining the CP conformation, determinant for the physical properties of these materials.

Effect of the protonation degree of a self-assembled monolayer on the immobilization dynamics of a [NiFe] hydrogenase.

Understanding the interaction and immobilization of [NiFe] hydrogenases on functionalized surfaces is important in the field of biotechnology and, in particular, for the development of biofuel cells. In this study, we investigated the adsorption behavior of the standard [NiFe] hydrogenase of Desulfovibrio gigas on amino-terminated alkanethiol self-assembled monolayers (SAMs) with different levels of protonation. Classical all-atom molecular dynamics (MD) simulations revealed a strong correlation between the adsorption behavior and the level of ionization of the chemically modified electrode surface. While the hydrogenase undergoes a weak but stable initial adsorption process on SAMs with a low degree of protonation, a stronger immobilization is observable on highly ionized SAMs, affecting protein reorientation and conformation. These results were validated by complementary surface-enhanced infrared absorption (SEIRA) measurements on the comparable [NiFe] standard hydrogenases from Desulfovibrio vulgaris Miyazaki F and allowed in this way for a detailed insight into the adsorption mechanism at the atomic level.

Electronic Delocalization in Coordination Polymers Based on Bimetallic Carboxylates.

Computational methods (DFT at the B3LYP, PBE0 and m06 levels, MO fragments decomposition, and the broken symmetry approach) have been used to evaluate the influence of the bridging ligand (BL) on the extent of electron delocalization in coordination polymers based on diruthenium tetracarboxylates. The efficiency of three different nitrogenated axial ligands, namely pyrazine (pz), phenazine (phz), and tetrazine (tz), to mediate electron coupling between Ru2(II,II) or Ru2(II,III) centers has been estimated through four different parameters: calculated Ru-N distances, HOMO-LUMO gaps, HOMO and LUMO compositions, and magnetic coupling constants J. All these parameters pointed toward a coordination polymer based on Ru2(II,II) centers axially linked by tetrazine being the best candidate for exhibiting electron delocalization through the Ru2-BL framework. Such a compound has been synthesized and characterized; its vis-NIR spectrum exhibited the predicted features, mainly an intense low-energy MLCT band, assigned to the expected Ru2(II,II) → tz process associated with electron delocalization.

Theoretical and experimental studies of diruthenium tetracarboxylates structure, spectroscopy, and electrochemistry.

Quantum mechanical calculations at the density functional theory (DFT) level have been performed on diruthenium tetracarboxylates of different levels of molecular complexity: from unsolvated monomers to oligomers. The agreement between the calculated and experimental molecular structures and vibrational modes of the simple [Ru2(micro-O2CCH3)4]0/+ and [Ru2(micro-O2CCH3)4(H2O)2]0/+ systems made us confident in our calculation methodology. Therefore, it has been applied to the analysis of two different kinds of properties of these compounds: the trends in the UV/vis spectroscopy and electrochemistry along the [Ru2(micro-O2CCH3)4X2]- (X=Cl-, Br-, I-) series, and the crystalline polymorphism related to the polymeric strand conformation in extended Ru2(micro-O2CR)4Cl compounds. For the [Ru2(micro-O2CCH3)4X2]- series, we report new spectroscopic and electrochemical results and interpret the trends on the basis of time dependent DFT-polarized continuum model calculations, local charge and spin analysis, and X donor properties. As far as the polymeric conformation is concerned, it has been previously suggested that the Ru-Cl-Ru angle results from a compromise between packing, orbital overlap, and microsegregation. Our calculations on [Ru2(micro-O2CCH3)4Cl]2Cl- and [Ru2(micro-O2CCH3)4Cl]3Cl- oligomers provide insights on the influence of the first two factors on the strand conformation and allows a suggestion on what is the equatorial aliphatic chain's influence on this issue.

Mortalidade e o tempo de internação em uma unidade de terapia intensiva cirúrgica / Mortality and length of stay in a surgical intensive care unit

JUSTIFICATIVA E OBJETIVOS: Em cuidados intensivos os resultados podem ser relacionados aos índices de mortalidade ou morbidade. Quando avaliada de forma isolada, a mortalidade é uma medida insuficiente do resultado na Unidade de Terapia Intensiva (UTI); o tempo de internação pode ser uma medida indireta do resultado relacionado com a morbidade. O objetivo do presente estudo foi avaliar a incidência e os fatores preditivos para mortalidade e tempo de internação dos pacientes admitidos numa UTI cirúrgica. MÉTODO: Participaram deste estudo prospectivo, realizado, entre abril e julho de 2004, todos os 185 pacientes submetidos a procedimentos programados ou de emergência, admitidos numa UTI cirúrgica. Foram registrados os seguintes parâmetros: idade, sexo, altura e peso, temperatura central estado físico segundo a ASA, tipo de intervenção cirúrgica, porte cirúrgico, técnica anestésica, quantidade e qualidade de fluídos administrados durante a anestesia, monitorização da temperatura ou de técnica de aquecimento corporal peri-operatório, duração da anestesia, tempo de permanência na UTI e no hospital e escore SAPS II. RESULTADOS: O tempo médio de internação na UTI foi de 4,09 ± 10,23 dias. Fatores de risco significativos para permanências mais prolongadas na UTI foram o valor do escore SAPS II, estado físico ASA, quantidade administrada, durante a intervenção cirúrgica, de colóides, unidades de plasma fresco e unidades de concentrados de hemáceas. Quatorze pacientes (7,60 por cento) morreram durante a internação na UTI e 29 (15,70 por cento) morreram durante a internação hospitalar. Fatores de risco independentes de mortalidade com diferença estatística significativa foram intervenções cirúrgicas de emergência, de grande porte, escores altos SAPS II, permanência prolongada na UTI e no hospital. Fatores protetores com diferença estatística significativa para risco de morte hospitalar foram baixo peso corporal e baixo índice de massa corporal (IMC). CONCLUSÕES: As internações prolongadas em UTI são mais freqüentes nos pacientes mais graves à admissão e estão associadas às maiores mortalidades hospitalares. A mortalidade hospitalar é também mais freqüente em pacientes submetidos a intervenções cirúrgicas de emergência ou de grande porte.

[Mortality and length of stay in a surgical intensive care unit.]. / Mortalidade e o tempo de internação em uma unidade de terapia intensiva cirúrgica.

BACKGROUND AND OBJECTIVES: Outcome in intensive care can be categorized as mortality related or morbidity related. Mortality is an insufficient measure of ICU outcome when measured alone and length of stay may be seen as an indirect measure of morbidity related outcome. The aim of the present study was to estimate the incidence and predictive factors for intrahospitalar outcome measured by mortality and LOS in patients admitted to a surgical ICU. METHODS: In this prospective study all 185 patients, who underwent scheduled or emergency surgery admitted to a surgical ICU in a large tertiary university medical center performed during April and July 2004, were eligible to the study. The following variables were recorded: age, sex, body weight and height, core temperature (Tc), ASA physical status, emergency or scheduled surgery, magnitude of surgical procedure, anesthesia technique, amount of fluids during anesthesia, use of temperature monitoring and warming techniques, duration of the anesthesia, length of stay in ICU and in the hospital and SAPS II score. RESULTS: The mean length of stay in the ICU was 4.09 +/- 10.23 days. Significant risk factors for staying longer in ICU were SAPS II, ASA physical status, amount of colloids, fresh frozen plasma units and packed erythrocytes units used during surgery. Fourteen (7.60%) patients died in ICU and 29 (15.70%) died during their hospitalization. Statistically significant independent risk factors for mortality were emergency surgery, major surgery, high SAPS II scores, longer stay in ICU and in the hospital. Statistically significant protective factors against the probability of dying in the hospital were low body weight and low BMI. CONCLUSIONS: In conclusion, prolonged ICU stay is more frequent in more severely ill patients at admission and it is associated with higher hospital mortality. Hospital mortality is also more frequent in patients submitted to emergent and major surgery.

A pyrazine bis-adduct of a binuclear rhodium(II) carboxylate containing 3,4,5-triethoxybenzoate as the equatorial ligand.

The title compound, tetrakis(mu-3,4,5-triethoxybenzoato-kappa(2)O:O')bis[(pyrazine-kappa N)rhodium(II)](Rh[bond]Rh), [Rh(2)(C(13)H(17)O(5))(4)(C(4)H(4)N(2))(2)], crystallizes on an inversion centre in the triclinic space group P1. The equatorial carboxylate ligands bridge the two Rh(II) atoms, giving a binuclear lantern-like structure. The pyrazine molecules occupy the two axial coordination sites. The phenyl rings are tilted by ca 10 degrees with respect to the attached carboxylate groups. The pyrazine planes have a torsion angle of ca 19 degrees around the Rh-N bond with respect to the plane of the nearer carboxylate group and are not coplanar with the Rh[bond]Rh bond.