Why do proteins use selenocysteine instead of cysteine?

Selenocysteine is present in a variety of proteins and catalyzes the oxidation of thiols to disulfides and the reduction of disulfides to thiols. Here, we compare the kinetic and thermodynamic properties of cysteine with its selenium-containing analogon, selenocysteine. Reactions of simple selenols at pH 7 are up to four orders of magnitude faster than their sulfur analogs, depending on reaction type. In redox-related proteins, the use of selenium instead of sulfur can be used to tune electrode, or redox, potentials. Selenocysteine could also have a protective effect in proteins because its one-electron oxidized product, the selanyl radical, is not oxidizing enough to modify or destroy proteins, whereas the cysteine-thiyl radical can do this very rapidl

Acute Tension Pneumothorax Following Cardiac Herniation after Pneumonectomy

A tension pneumothorax is one of the main causes of cardiac arrest in the initial postoperative period after thoracic surgery. Tension pneumothorax and cardiac herniation must be taken into account in hemodynamically unstable patients after pneumonectomy. We report an unusual case of successful treatment of acute tension pneumothorax following cardiac herniation and intrathoracic bleeding after pneumonectomy

The impact of vegetation on fractionation of rare earth elements(REE) during water–rock interaction

Previous studies on waters of a streamlet in the Vosges mountains (eastern France) have shown that Sr and rare earth elements (REE) principally originate from apatite dissolution during weathering. However, stream water REE patterns normalized to apatite are still depleted in light REE (LREE, La–Sm) pointing to the presence of an additional LREE depleting process. Speciation calculations indicate that complexation cannot explain this additional LREE depletion. In contrast, vegetation samples are strongly enriched in LREE compared to water and their Sr and Nd isotopic compositions are comparable with those of apatite and waters. Thus, the preferential LREE uptake by the plants at the root–water–soil (apatite) interface might lead to an additional LREE depletion of the waters in the forested catchment. Mass balance calculations indicate that the yearly LREE uptake by vegetation is comparable with the LREE export by the streamlet and, therefore, might be an important factor controlling the LREE depletion in river waters

Demographic responses to the manipulation of adult females in corn mouse populations

Variation in population abundance is a consequence of changes in demographic parameters such as survival and recruitment. These demographic parameters can be affected by intraspecifi c competition, thus adults may play an important role influencing the survival and/or reproduction of juvenile individuals in many species of small mammals. We present an analysis of Calomys musculinus populations using capturemark- recapture models in order to evaluate the effect of female removal on their demography. The study was carried out in four enclosures during two different periods: a reference period and a treatment period, with the removal of adult females. Reference period was analyzed to describe population demography without manipulations. In treatment period, two control enclosures maintained both parents remained with their offspring whereas other two enclosures had their adult females removed. Seven monthly trapping sessions were carried out (spring to autumn). We estimated apparent survival, recruitment, population growth rates and recapture probabilities. Models considered these parameters constrained to vary as a function of time, enclosure, sex and/or treatment. During the reference period survival and recruitment showed sex and time effects, survival was higher in females and decreased towards June; recruitment showed a peak in February with a higher number of recruited males; population growth rates peaked in February and decreased towards June. During the treatment period survival showed time effect whereas recruitment showed time and treatment effects. Survival was higher at the beginning of the breeding period and decreased afterwards, and recruitment was higher in control enclosures; population growth rates showed a similar pattern than in reference period. There were not differences in growth rates and abundances between control and experimental enclosures. Under our experimental and methodological conditions, the results would indicate that the absence of females in experimental enclosures was not enough to cause a clear impact on final population size.Fil: Gomez, Maria Daniel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; ArgentinaFil: Steinmann, Andrea Rosa. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina. Universidad Nacional de Río Cuarto; ArgentinaFil: Priotto, Jose Waldemar. Universidad Nacional de Río Cuarto; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentin

Demographic responses to the manipulation of adult females in corn mouse populations

Variation in population abundance is a consequence of changes in demographic parameters such as survival and recruitment. These demographic parameters can be affected by intraspecifi c competition, thus adults may play an important role influencing the survival and/or reproduction of juvenile individuals in many species of small mammals. We present an analysis of Calomys musculinus populations using capturemark- recapture models in order to evaluate the effect of female removal on their demography. The study was carried out in four enclosures during two different periods: a reference period and a treatment period, with the removal of adult females. Reference period was analyzed to describe population demography without manipulations. In treatment period, two control enclosures maintained both parents remained with their offspring whereas other two enclosures had their adult females removed. Seven monthly trapping sessions were carried out (spring to autumn). We estimated apparent survival, recruitment, population growth rates and recapture probabilities. Models considered these parameters constrained to vary as a function of time, enclosure, sex and/or treatment. During the reference period survival and recruitment showed sex and time effects, survival was higher in females and decreased towards June; recruitment showed a peak in February with a higher number of recruited males; population growth rates peaked in February and decreased towards June. During the treatment period survival showed time effect whereas recruitment showed time and treatment effects. Survival was higher at the beginning of the breeding period and decreased afterwards, and recruitment was higher in control enclosures; population growth rates showed a similar pattern than in reference period. There were not differences in growth rates and abundances between control and experimental enclosures. Under our experimental and methodological conditions, the results would indicate that the absence of females in experimental enclosures was not enough to cause a clear impact on final population size.Fil: Gomez, Maria Daniel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; ArgentinaFil: Steinmann, Andrea Rosa. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina. Universidad Nacional de Río Cuarto; ArgentinaFil: Priotto, Jose Waldemar. Universidad Nacional de Río Cuarto; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentin

On mesh coarsening procedures for the virtual element method

In the context of adaptive remeshing, the virtual element method provides significant advantages over the finite element method. The attractive features of the virtual element method, such as the permission of arbitrary element geometries, and the seamless permission of 'hanging' nodes, have inspired many works concerning error estimation and adaptivity. However, these works have primarily focused on adaptive refinement techniques with little attention paid to adaptive coarsening (i.e. de-refinement) techniques that are required for the development of fully adaptive remeshing procedures. In this work novel indicators are proposed for the identification of patches/clusters of elements to be coarsened, along with a novel procedure to perform the coarsening. The indicators are computed over prospective patches of elements rather than on individual elements to identify the most suitable combinations of elements to coarsen. The coarsening procedure is robust and suitable for meshes of structured and unstructured/Voronoi elements. Numerical results demonstrate the high degree of efficacy of the proposed coarsening procedures and sensible mesh evolution during the coarsening process. It is demonstrated that critical mesh geometries, such as non-convex corners and holes, are preserved during coarsening, and that meshes remain fine in regions of interest to engineers, such as near singularities

Reduction of protein radicals by GSH and ascorbate: potential biological significance

The oxidation of proteins and other macromolecules by radical species under conditions of oxidative stress can be modulated by antioxidant compounds. Decreased levels of the antioxidants glutathione and ascorbate have been documented in oxidative stress-related diseases. A radical generated on the surface of a protein can: (1) be immediately and fully repaired by direct reaction with an antioxidant; (2) react with dioxygen to form the corresponding peroxyl radical; or (3) undergo intramolecular long range electron transfer to relocate the free electron to another amino acid residue. In pulse radiolysis studies, in vitro production of the initial radical on a protein is conveniently made at a tryptophan residue, and electron transfer often leads ultimately to residence of the unpaired electron on a tyrosine residue. We review here the kinetics data for reactions of the antioxidants glutathione, selenocysteine, and ascorbate with tryptophanyl and tyrosyl radicals as free amino acids in model compounds and proteins. Glutathione repairs a tryptophanyl radical in lysozyme with a rate constant of (1.05±0.05)×105M-1s-1, while ascorbate repairs tryptophanyl and tyrosyl radicals ca. 3 orders of magnitude faster. The in vitro reaction of glutathione with these radicals is too slow to prevent formation of peroxyl radicals, which become reduced by glutathione to hydroperoxides; the resulting glutathione thiyl radical is capable of further radical generation by hydrogen abstraction. Although physiologically not significant, selenoglutathione reduces tyrosyl radicals as fast as ascorbate. The reaction of protein radicals formed on insulin, β-lactoglobulin, pepsin, chymotrypsin and bovine serum albumin with ascorbate is relatively rapid, competes with the reaction with dioxygen, and the relatively innocuous ascorbyl radical is formed. On the basis of these kinetics data, we suggest that reductive repair of protein radicals may contribute to the well-documented depletion of ascorbate in living organisms subjected to oxidative stres