Studying O2 pathways in [NiFe]- and [NiFeSe]-hydrogenases

Hydrogenases are efficient biocatalysts for H2 production and oxidation with various potential biotechnological applications.[NiFe]-class hydrogenases are highly active in both production and oxidation processes—albeit primarily biased to the latter—but suffer from being sensitive to O2.[NiFeSe] hydrogenases are a subclass of [NiFe] hydrogenases with, usually, an increased insensitivity to aerobic environments. In this study we aim to understand the structural causes of the low sensitivity of a [NiFeSe]-hydrogenase, when compared with a [NiFe] class enzyme, by studying the diffusion of O2. To unravel the differences between the two enzymes, we used computational methods comprising Molecular Dynamics simulations with explicit O2 and Implicit Ligand Sampling methodologies. With the latter, we were able to map the free energy landscapes for O2 permeation in both enzymes. We derived pathways from these energy landscapes and selected the kinetically more relevant ones with reactive flux analysis using transition path theory. These studies evidence the existence of quite different pathways in both enzymes and predict a lower permeation efficiency for O2 in the case of the [NiFeSe]-hydrogenase when compared with the [NiFe] enzyme. These differences can explain the experimentally observed lower inhibition by O2 on [NiFeSe]-hydrogenases, when compared with [NiFe]-hydrogenases. A comprehensive map of the residues lining the most important O2 pathways in both enzymes is also presented.publishersversionpublishe

Thermodynamics of the incommensurate state in Rb_2WO_4: on the Lifshitz point in A`A``BX_4 compounds

We consider the evolution of the phase transition from the parent hexagonal phase $P6_{3}/mmc$ to the orthorhombic phase $Pmcn$ that occurs in several compounds of $A'A''BX_{4}$ family as a function of the hcp lattice parameter $c/a$. For compounds of $K_{2}SO_{4}$ type with $c/a$ larger than the threshold value 1.26 the direct first-order transition $Pmcn-P6_{3}/mmc$ is characterized by the large entropy jump $Rln2$. For compounds $Rb_{2}WO_{4}$, $K_{2}MoO_{4}$, $K_{2}WO_{4}$ with $c/a<1.26$ this transition occurs via an intermediate incommensurate $(Inc)$ phase. DSC measurements were performed in $Rb_{2}WO_{4}$ to characterize the thermodynamics of the $Pmcn-Inc-P6_{3}/mmc$ transitions. It was found that both transitions are again of the first order with entropy jumps $0.2Rln2 and$0.3Rln2$. Therefore, at$c/a ~ 1.26$the$A'A''BX_{4}$compounds reveal an unusual Lifshitz point where three first order transition lines meet. We propose the coupling of crystal elasticity with$BX_{4}$ tetrahedra orientation as a possible source of the transitions discontinuity.Comment: 13 pages,1 Postscript figure. Submitted as Brief Report to Phys. Rev. B, this paper reports a new work in Theory and Experiment, directed to Structural Phase Transition

Physiological and thermographic response to heat stress in zebu cattle

AbstractThe objective of this study was to evaluate the heat tolerance of five zebu breeds using physical, physiological and hematological traits as well as thermographic responses. Forty cows of the Gir, Girolando, Nelore, Sindhi and Indubrasil breeds (eight cows each), approximately three years of age, were evaluated. Body weight, withers and hump heights as well as thoracic circumference were recorded. The density and length of the hair was obtained by collecting one square centimeter in the rump region and skin color using the CIELAB system. Rectal temperature, heart and respiratory rates were evaluated during the morning at 4:30h, and in the afternoon, at 14:30h, with six repetitions. Blood samples were collected for hematological evaluation. The surface temperature was obtained using an infrared camera FLIR® T400. Two images were taken from each animal, one laterally of the whole body and the other of the head region. Air temperature, wind speed, relative humidity were obtained from a mobile weather station. The statistics analysis included an analyzes of variance, principal factors, as well as cluster, discriminant and canonical analyzes, logistic regression and calculation of odds ratio. There were significant differences in the rectal temperature, heart and respiratory rates between breeds. Gir and Indubrasil breeds had the highest rectal temperatures. Breed was significant for surface temperatures and showed that physical and physiological factors affected breeds in different ways. Eye and brain surface temperatures were the most affected by environmental parameters. Also, environmental parameters affected packed cell volume and red cell number. Odds ratio test showed that the Gir breed was three times more likely to have higher rectal temperature compared with Sindhi as confirmed by the logistic regression. When the black globe temperature approached 35°C, the probability of the Gir animals having rectal temperatures above normal was approximately 70%. Gir was the breed least adapted to climate conditions of the experiment while the Sindhi and Girolando breeds showed the best physiological response to thermal stress

Cosmological equations and Thermodynamics on Apparent Horizon in Thick Braneworld

We derive the generalized Friedmann equation governing the cosmological evolution inside the thick brane model in the presence of two curvature correction terms: a four-dimensional scalar curvature from induced gravity on the brane, and a five-dimensional Gauss-Bonnet curvature term. We find two effective four-dimensional reductions of the Friedmann equation in some limits and demonstrate that they can be rewritten as the first law of thermodynamics on the apparent horizon of thick braneworld.Comment: 25 pages, no figure, a definition corrected, several references added, more motivation and discussio

Dirofilaria immitis parasite infection in cats: first case reported in the Legal Amazon region, Brazil - case report

ABSTRACT A case of infection with Dirofilaria immitis in a cat is reported here with clinical signs of apathy, anorexia, dyspnea, polypnea, slight dehydration and pale mucus membranes. The radiographic examination showed cardiomegaly, lobar arteries dilation of the cranial lobes and tortuosity, enlargement of the caudal lobar arteries. In the right lobe of the lung parenchyma, interstitial pulmonary opacification tending to alveolar opacification was seen. The clinical signs, the movements, and the morphology of the microfilariae in the direct examination of fresh blood, peripheral blood smear and Knott’s modified test supported the diagnosis. We alert to the need for clinicians to consider feline heartworm diseases as a differential diagnosis in endemic areas when cats show respiratory signs

Search for the Rare Decay KL --> pi0 ee

The KTeV/E799 experiment at Fermilab has searched for the rare kaon decay KL--> pi0ee. This mode is expected to have a significant CP violating component. The measurement of its branching ratio could support the Standard Model or could indicate the existence of new physics. This letter reports new results from the 1999-2000 data set. One event is observed with an expected background at 0.99 +/- 0.35 events. We set a limit on the branching ratio of 3.5 x 10^(-10) at the 90% confidence level. Combining the results with the dataset taken in 1997 yields the final KTeV result: BR(KL --> pi0 ee) < 2.8 x 10^(-10) at 90% CL.Comment: 4 pages, three figure

Lycopene-rich extract from red guava ( Psidium guajava L.) displays cytotoxic effect against human breast adenocarcinoma cell line MCF-7 via an apoptotic-like pathway

This study investigated a lycopene-rich extract from red guava (LEG) for its chemical composition using spectrophotometry, mass spectrometry, attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), and computational studies. The cytotoxic activity of LEG and the underlying mechanism was studied in human breast adenocarcinoma cells (MCF-7), murine fibroblast cells (NIH-3T3), BALB/c murine peritoneal macrophages, and sheep blood erythrocytes by evaluating the cell viability with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method and flow cytometry. Spectrophotometry analysis showed that LEG contained 20% of lycopene per extract dry weight. Experimental and theoretical ATR-FTIR suggests the presence of lycopene, whereas MS/MS spectra obtained after fragmentation of the molecular ion [M]+• of 536.4364 show fragment ions at m/z 269.2259, 375.3034, 444.3788, and 467.3658, corroborating the presence of lycopene mostly related to all-trans configuration. Treatment with LEG (1600 to 6.25μg/mL) for 24 and 72h significantly affected the viability of MCF-7 cells (mean half maximal inhibitory concentration [IC50]=29.85 and 5.964μg/mL, respectively) but not NIH-3T3 cells (IC50=1579 and 911.5μg/mL, respectively). Furthermore LEG at concentrations from 800 to 6.25μg/mL presented low cytotoxicity against BALB/c peritoneal macrophages (IC50≥800μg/mL) and no hemolytic activity. LEG (400 and 800μg/mL) caused reduction in the cell proliferation and induced cell cycle arrest, DNA fragmentation, modifications in the mitochondrial membrane potential, and morphologic changes related to granularity and size in MCF-7 cells; however, it failed to cause any significant damage to the cell membrane or display necrosis or traditional apoptosis. In conclusion, LEG was able to induce cytostatic and cytotoxic effects on breast cancer cells probably via induction of an apoptotic-like pathway.The authors acknowledge the computational time provided by CENAPAD/SP on the project proj697. Alexandra Plácido is gratefully to FCT by her grant SFRH/BD/97995/2013, financed by POPH–QREN–Tipologia 4.1–Formação Avançada, subsidized by Fundo Social Europeu and Ministério da Ciência, Tecnologia e Ensino Superior. The work at REQUIMTE/LAQV received financial support from the European Union (FEDER funds through COMPETE) and National Funds (FCT) through project UID/QUI/50006/2013. Adriany das G. N. Amorim is grateful to CAPES by for the doctoral fellowship process no. 99999.004236/2014-09 in Federal University of Piauí (UFPI). Eder A. Barbosa is grateful to PNPD/CAPES for its post-doctoral fellowship.info:eu-repo/semantics/publishedVersio