Search results for "lost"

Evaluation of Changes in Gut Microbiota in Patients with Crohn’s Disease after Anti-Tnfα Treatment: Prospective Multicenter Observational Study

2020

Background: Crohn’s disease is believed to result from the interaction between genetic susceptibility, environmental factors and gut microbiota, leading to an aberrant immune response. The objectives of this study are to evaluate the qualitative and quantitative changes in the microbiota of patients with Crohn’s disease after six months of anti-tumor-necrosis factor (anti-TNFα) (infliximab or adalimumab) treatment and to determine whether these changes lead to the recovery of normal microbiota when compared to a control group of healthy subjects. In addition, we will evaluate the potential role of the Faecalibacterium prausnitzii/Escherichia coli and Faecalibacterium prausnitzii/Clostridium…

Proline-Based Allosteric Inhibitors of Zika and Dengue Virus NS2B/NS3 Proteases

2019

The NS2B/NS3 serine proteases of the Zika and Dengue flaviviruses are attractive targets for the development of antiviral drugs. We report the synthesis and evaluation of a new, proline-based compound class that displays allosteric inhibition of both proteases. The structural features relevant for protease binding and inhibition were determined to establish them as new lead compounds for flaviviral inhibitors. Based on our structure-activity relationship studies, the molecules were further optimized, leading to inhibitors with submicromolar IC50 values and improved lipophilic ligand efficiency. The allosteric binding site in the proteases was probed using mutagenesis and covalent modificati…

SAR of novel benzothiazoles targeting an allosteric pocket of DENV and ZIKV NS2B/NS3 proteases

2021

In recent years, dengue virus (DENV) and Zika virus (ZIKV), both mosquito-borne members of the Flaviviridae family, have emerged as intercontinental health issues since their vectors have spread from their tropical origins to temperate climate zones due to climate change and increasing globalization. DENV and ZIKV are positive-sense, single-stranded RNA viruses, whose genomes consist of three structural (capsid, membrane precursor, envelope) and seven non-structural (NS) proteins, all of which are initially expressed as a single precursor polyprotein. For virus maturation, the polyprotein processing is accomplished by host proteases and the viral NS2B/NS3 protease complex, whose inhibitors …

The molecular heterogeneity of hemocyanin: Structural and functional properties of the 4×6-meric protein of Upogebia pusilla (Crustacea)

2006

The structural properties of the hemocyanin isolated from the Mediterranean mud shrimp, Upogebia pusilla (Decapoda: Thalassinidea), were investigated. Our intent was to make use of the U. pusilla case to perform a structural comparison between crustacean and chelicerate 4×6-meric hemocyanins. The thalassinidean hemocyanin appears similar in size but different in structural organization compared to the chelicerate 4×6-mer. Ultracentrifuge analyses on the purified protein revealed a sedimentation coefficient of 39S, typical of 4×6 hemocyanins. Electron micrographs are in agreement with a model in which four 2×6-meric building blocks are arranged in a tetrahedron-like quaternary structure and …

Subunits composition and allosteric control in Carcinus aestuarii hemocyanin

1998

Carcinus aestuarii hemocyanin (Hc) exists in two aggregation forms at pH 7.5 and 20 mM Ca2+: 24S accounting for 90% of total hemocyanin and 16S accounting for 10%. Removal of metal cations by EDTA at neutral pH causes the complete dissociation of 24S hemocyanin into two different 16S. At pH 9.2, 24S hemocyanin dissociates into a pH stable 16S and a 5S component. The 5S component consists of three monomeric fractions named CaeSS1 (10%), CaeSS2 (50%) and CaeSS3 (40%); the latter fraction consisting of two isoforms. The fractions CaeSS1, CaeSS2 and CaeSS3 have been studied as far as their reassociation properties to form hexamers are concerned. We investigated the oxygen-binding properties of …

Allosteric Models for Multimeric Proteins:  Oxygen-Linked Effector Binding in Hemocyanin

2005

In many crustaceans, changing concentrations of several low molecular weight compounds modulates hemocyanin oxygen binding, resulting in lower or higher oxygen affinities of the pigment. The nonphysiological effector caffeine and the physiological modulator urate, the latter accumulating in the hemolymph of the lobster Homarus vulgaris during hypoxia, increase hemocyanin oxygen affinity and decrease cooperativity of oxygen binding. To derive a model that describes the mechanism of allosteric interaction between hemocyanin and oxygen in the presence of urate or caffeine, studies of oxygen, urate, and caffeine binding to hemocyanin were performed. Exposure of lobster hemocyanin to various pH …

Linked Analysis of Large Cooperative, Allosteric Systems: The Case of the Giant HBL Hemoglobins

2008

Homotropic and heterotropic allosteric interactions are important mechanisms that regulate protein function. These mechanisms depend on the ability of oligomeric protein complexes to adopt different conformations and to transmit conformation-linked signals from one subunit of the complex to the neighboring ones. An important step in understanding the regulation of protein function is to identify and characterize the conformations available to the protein complex. This task becomes increasingly challenging with increasing numbers of interacting binding sites. However, a large number of interacting binding sites allows for high homotropic interactions (cooperativity) and thus represents the m…

Bohr-effect and buffering capacity of hemocyanin from the tarantula E. californicum.

2003

A previous report showed that binding of oxygen to the 24-meric hemocyanin from E. californicum does not correlate linearly with the release of protons as known from hemoglobin. However, this unusual complex phenomenological observation could not be explained at that time. Here, I present a full analysis of the thermodynamic coupling between protons and oxygen for the 24-meric tarantula hemocyanin in Ringer-solution based on the Nested-MWC-model. A strategy is presented which allows to reduce the number of free parameters when fitting the model to the data by including explicitly the equilibrium constants for binding of protons to the different conformations. The results show that the Neste…

Composizione chimica dell'olio essenziale di Ptilostemon greuteri (Compositae)

2009

Phytochemical Studies on Ptilostemon greuteri Raimondo & Domina (Compositae)

2012

Ptilostemon greuteri Raimondo & Domina is described as a new species and its growth is limited to the area of the province of Trapani. Essential oils of aerial parts of P. greuteri were analized by gas chromatography-mass spectrometry (GC-MS). The analysis of acetonic extract of aerial parts led to identification of triterpenes components: α-amyrin, β-amyrin, α-amyrin acetate, β-amyrin acetate, lupeol, lupeol acetate and taraxasterol. CC and preparative TLC of acetonic extracts has yielded lignan lactone and a sesquiterpene lactone that have been isolated previously from other Ptilostemon species.