Transfer of Sulfur from IscS to IscU during Fe/S Cluster Assembly

The cysteine desulfurase enzymes NifS and IscS provide sulfur for the biosynthesis of Fe/S proteins. NifU and IscU have been proposed to serve as template or scaffold proteins in the initial Fe/S cluster assembly events, but the mechanism of sulfur transfer from NifS or IscS to NifU or IscU has not been elucidated. We have employed [35S]cysteine radiotracer studies to monitor sulfur transfer between IscS and IscU from Escherichia coli and have used direct binding measurements to investigate interactions between the proteins. IscS catalyzed transfer of 35S from [35S]cysteine to IscU in the absence of additional thiol reagents, suggesting that transfer can occur directly and without involvement of an intermediate carrier. Surface plasmon resonance studies and isothermal titration calorimetry measurements further revealed that IscU binds to IscS with high affinity (Kd ~2 µM) in support of a direct transfer mechanism. Transfer was inhibited by treatment of IscU with iodoacetamide, and 35S was released by reducing reagents, suggesting that transfer of persulfide sulfur occurs to cysteinyl groups of IscU. A deletion mutant of IscS lacking C-terminal residues 376-413 (IscSDelta 376-413) displayed cysteine desulfurase activity similar to the full-length protein but exhibited lower binding affinity for IscU, decreased ability to transfer 35S to IscU, and reduced activity in assays of Fe/S cluster assembly on IscU. The findings with IscSDelta 376-413 provide additional support for a mechanism of sulfur transfer involving a direct interaction between IscS and IscU and suggest that the C-terminal region of IscS may be important for binding IscU

Efecto de la adición de biovídrio e hidroxiapatita en ácido poli-L-láctico sobre la adsorción superficial de fosfatos

The interaction between hydroxyapatite (HAP),the bioglass and polylactic acid (PLA), which weresynthesized by aqueous precipitation methods(PAH), sol-gel (bioglass) and polycondensation(PLA) was evaluated; These precursors wereevaluated by FTIR, DRX, DSC, and then weremixed (PLA –Bioglass and PLA-hydroxyapatite),for the biomineralization effect analysis, todetermine which one of this mixtures of materialspresent a better response to the osteointegration inpresence of Human Body Fluids. The mixtures withdifferent percentages of polymeric and ceramicswere submerged in SBF (Simulated Body Fluid) byperiods of seven, fourteen and twenty-one days.The tests of biomineralization were carried out insolution SBF by using electrochemical Impedancespectroscopy technique (EIS). A comparisonbetween the polarization resistances of the differentsamples, obtained in different days of immersionin SBF was obtained; the best condition favorablewas for fourteen days of immersion in SBF forthe two mixtures studied; where the PLA/HAPsample showed the highest polarization resistanceand hence, better effect to the biomineralization.The morphology of the mixtures was evaluated byusing the analysis by SEM-EDS.En este trabajo se evaluó la interacción entrela hidroxiapatita (HAP), el biovidrio y el acidopoliláctico (PLA), los cuales fueron sintetizadospor métodos de precipitación acuosa (HAP),sol-gel (Biovidrio) y Policondensación (PLA);estos precursores fueron evaluados por FTIR,DRX, DSC, mezclándose posteriormente (PLAbiovidrioy PLA-hidroxiapatita) para su análisis debiomineralización a nivel de laboratorio, con el finde determinar cuál de estas mezclas de materialespresentó una mejor respuesta a la oseointegraciónen presencia de fluidos del cuerpo humano. Lasmezclas con diferentes porcentajes de polímeroy cerámico fueron sumergidas en SBF (solucióncorporal simulada) por periodos de siete, catorce yveintiún días. Las pruebas de biomineralización hansido realizadas en fluido corporal simulado (SBF) yevaluadas por medio de la técnica de espectroscopiade impedancia electroquímica (EIE). Se establecióuna comparación entre las resistencias a lapolarización de las distintas muestras obtenidas adiferentes días de inmersión en SBF, donde se logróla mejor condición favorable a los catorce días deinmersión en SBF para las dos mezclas estudiadas,siendo la mezcla PLA/HAP la de mayor resistenciaa la polarización, y por tanto la de mejor efecto deBiomineralización. La morfología de las mezclas seevaluó a partir de análisis de SEM-EDS

Averting biodiversity collapse in tropical forest protected areas

The rapid disruption of tropical forests probably imperils global biodiversity more than any other contemporary phenomenon¹⁻³. With deforestation advancing quickly, protected areas are increasingly becoming final refuges for threatened species and natural ecosystem processes. However, many protected areas in the tropics are themselves vulnerable to human encroachment and other environmental stresses⁴⁻⁹. As pressures mount, it is vital to know whether existing reserves can sustain their biodiversity. A critical constraint in addressing this question has been that data describing a broad array of biodiversity groups have been unavailable for a sufficiently large and representative sample of reserves. Here we present a uniquely comprehensive data set on changes over the past 20 to 30 years in 31 functional groups of species and 21 potential drivers of environmental change, for 60 protected areas stratified across the world’s major tropical regions. Our analysis reveals great variation in reserve ‘health’: about half of all reserves have been effective or performed passably, but the rest are experiencing an erosion of biodiversity that is often alarmingly widespread taxonomically and functionally. Habitat disruption, hunting and forest-product exploitation were the strongest predictors of declining reserve health. Crucially, environmental changes immediately outside reserves seemed nearly as important as those inside in determining their ecological fate, with changes inside reserves strongly mirroring those occurring around them. These findings suggest that tropical protected areas are often intimately linked ecologically to their surrounding habitats, and that a failure to stem broad-scale loss and degradation of such habitats could sharply increase the likelihood of serious biodiversity declines.Keywords: Ecology, Environmental scienc

Self-Assembled Small-Molecule Microarrays for Protease Screening and Profiling

Small-molecule microarrays are attractive for chemical biology as they permit the analysis of hundreds to thousands of interactions in a highly miniaturized format. Methods to prepare small-molecule microarrays from combinatorial libraries by a self-assembly process based on the sequence-specific hybridization of peptide nucleic acid (PNA) encoded libraries to oligonucleotide arrays are presented. A systematic study of the dynamic range for multiple detection agents, including direct fluorescence of attached fluorescein and cyanine-3 dyes, antibody-mediated fluorescence amplification, and biotin–gold nanoparticle detection, demonstrated that individual PNA-encoded probes can be detected to concentrations of 10 pm on the oligonucleotide microarrays. Furthermore, a new method for parallel processing of biological samples by using gel-based separation of probes is presented. The methods presented in this report are exemplified through profiling two closely related cysteine proteases, cathepsin K and cathepsin F, across a 625-member PNA-encoded tetrapeptide acrylate library. A series of the specific cathepsin K and F inhibitors identified from the library were kinetically characterized and shown to correlate with the observed microarray profile, thus validating the described methods. Importantly, it was shown that this method could be used to obtain orthogonal inhibitors that displayed greater than tenfold selectivity for these closely related cathepsins

Efecto de la adición de biovídrio e hidroxiapatita en ácido poli-L-láctico sobre la adsorción superficial de fosfatos

The interaction between hydroxyapatite (HAP),the bioglass and polylactic acid (PLA), which weresynthesized by aqueous precipitation methods(PAH), sol-gel (bioglass) and polycondensation(PLA) was evaluated; These precursors wereevaluated by FTIR, DRX, DSC, and then weremixed (PLA –Bioglass and PLA-hydroxyapatite),for the biomineralization effect analysis, todetermine which one of this mixtures of materialspresent a better response to the osteointegration inpresence of Human Body Fluids. The mixtures withdifferent percentages of polymeric and ceramicswere submerged in SBF (Simulated Body Fluid) byperiods of seven, fourteen and twenty-one days.The tests of biomineralization were carried out insolution SBF by using electrochemical Impedancespectroscopy technique (EIS). A comparisonbetween the polarization resistances of the differentsamples, obtained in different days of immersionin SBF was obtained; the best condition favorablewas for fourteen days of immersion in SBF forthe two mixtures studied; where the PLA/HAPsample showed the highest polarization resistanceand hence, better effect to the biomineralization.The morphology of the mixtures was evaluated byusing the analysis by SEM-EDS.En este trabajo se evaluó la interacción entrela hidroxiapatita (HAP), el biovidrio y el acidopoliláctico (PLA), los cuales fueron sintetizadospor métodos de precipitación acuosa (HAP),sol-gel (Biovidrio) y Policondensación (PLA);estos precursores fueron evaluados por FTIR,DRX, DSC, mezclándose posteriormente (PLAbiovidrioy PLA-hidroxiapatita) para su análisis debiomineralización a nivel de laboratorio, con el finde determinar cuál de estas mezclas de materialespresentó una mejor respuesta a la oseointegraciónen presencia de fluidos del cuerpo humano. Lasmezclas con diferentes porcentajes de polímeroy cerámico fueron sumergidas en SBF (solucióncorporal simulada) por periodos de siete, catorce yveintiún días. Las pruebas de biomineralización hansido realizadas en fluido corporal simulado (SBF) yevaluadas por medio de la técnica de espectroscopiade impedancia electroquímica (EIE). Se establecióuna comparación entre las resistencias a lapolarización de las distintas muestras obtenidas adiferentes días de inmersión en SBF, donde se logróla mejor condición favorable a los catorce días deinmersión en SBF para las dos mezclas estudiadas,siendo la mezcla PLA/HAP la de mayor resistenciaa la polarización, y por tanto la de mejor efecto deBiomineralización. La morfología de las mezclas seevaluó a partir de análisis de SEM-EDS

Efecto de la adición de biovídrio e hidroxiapatita en ácido poli-L-láctico sobre la adsorción superficial de fosfatos

The interaction between hydroxyapatite (HAP),the bioglass and polylactic acid (PLA), which weresynthesized by aqueous precipitation methods(PAH), sol-gel (bioglass) and polycondensation(PLA) was evaluated; These precursors wereevaluated by FTIR, DRX, DSC, and then weremixed (PLA –Bioglass and PLA-hydroxyapatite),for the biomineralization effect analysis, todetermine which one of this mixtures of materialspresent a better response to the osteointegration inpresence of Human Body Fluids. The mixtures withdifferent percentages of polymeric and ceramicswere submerged in SBF (Simulated Body Fluid) byperiods of seven, fourteen and twenty-one days.The tests of biomineralization were carried out insolution SBF by using electrochemical Impedancespectroscopy technique (EIS). A comparisonbetween the polarization resistances of the differentsamples, obtained in different days of immersionin SBF was obtained; the best condition favorablewas for fourteen days of immersion in SBF forthe two mixtures studied; where the PLA/HAPsample showed the highest polarization resistanceand hence, better effect to the biomineralization.The morphology of the mixtures was evaluated byusing the analysis by SEM-EDS.En este trabajo se evaluó la interacción entrela hidroxiapatita (HAP), el biovidrio y el acidopoliláctico (PLA), los cuales fueron sintetizadospor métodos de precipitación acuosa (HAP),sol-gel (Biovidrio) y Policondensación (PLA);estos precursores fueron evaluados por FTIR,DRX, DSC, mezclándose posteriormente (PLAbiovidrioy PLA-hidroxiapatita) para su análisis debiomineralización a nivel de laboratorio, con el finde determinar cuál de estas mezclas de materialespresentó una mejor respuesta a la oseointegraciónen presencia de fluidos del cuerpo humano. Lasmezclas con diferentes porcentajes de polímeroy cerámico fueron sumergidas en SBF (solucióncorporal simulada) por periodos de siete, catorce yveintiún días. Las pruebas de biomineralización hansido realizadas en fluido corporal simulado (SBF) yevaluadas por medio de la técnica de espectroscopiade impedancia electroquímica (EIE). Se establecióuna comparación entre las resistencias a lapolarización de las distintas muestras obtenidas adiferentes días de inmersión en SBF, donde se logróla mejor condición favorable a los catorce días deinmersión en SBF para las dos mezclas estudiadas,siendo la mezcla PLA/HAP la de mayor resistenciaa la polarización, y por tanto la de mejor efecto deBiomineralización. La morfología de las mezclas seevaluó a partir de análisis de SEM-EDS

Ablation of brainstem C1 neurons improves cardiac function in volume overload heart failure

Activation of the sympathetic nervous system is a hallmark of heart failure (HF) and is positively correlated with disease progression. Catecholaminergic (C1) neurons located in the rostral ventrolateral medulla (RVLM) are known to modulate sympathetic outflow and are hyperactivated in volume overload HF. However, there is no conclusive evidence showing a contribution of RVLM-C1 neurons to the development of cardiac dysfunction in the setting of HF. Therefore, the aim of this study was to determine the role of RVLM-C1 neurons in cardiac autonomic control and deterioration of cardiac function in HF rats. A surgical arteriovenous shunt was created in adult male Sprague-Dawley rats to induce HF. RVLM-C1 neurons were selectively ablated using cell-specific immunotoxin (dopamine-β hydroxylase saporin [DβH-SAP]) and measures of cardiac autonomic tone, function, and arrhythmia incidence were evaluated. Cardiac autonomic imbalance, arrhythmogenesis and cardiac dysfunctio

Enhanced proteolytic clearance of plasma Aβ by peripherally administered neprilysin does not result in reduced levels of brain Aβ in mice.

Accumulation of β-amyloid (Aβ) in the brain is believed to contribute to the pathology of Alzheimer's Disease (AD). Aβ levels are controlled by the production of Aβ from amyloid precursor protein, degradation by proteases, and peripheral clearance. In this study we sought to determine whether enhancing clearance of plasma Aβ with a peripherally administered Aβ-degrading protease would reduce brain Aβ levels through a peripheral sink. Neprilysin (NEP) is a zinc-dependent metalloprotease that is one of the key Aβ-degrading enzymes in the brain. We developed a NEP fusion protein with in vitro degradation of Aβ and a 10 day plasma half-life in mouse. Intravenous administration of NEP to wild-type and APP23 transgenic mice resulted in dose-dependent clearance of plasma Aβ. However, this did not correspond to reduced levels of soluble brain Aβ with treatment up to 5 weeks in WT mice or formic acid-extractable brain Aβ with 3 month treatment in aged APP23. In contrast, intracranial injection of NEP resulted in an acute decrease in soluble brain Aβ. We found no change in amyloid precursor protein gene expression in mice treated with intravenous NEP, suggesting that the lack of effects in the brain following this route of administration was not caused by compensatory upregulation of Aβ production. Taken together, these results suggest a lack of a robust peripheral Aβ efflux sink through which brain amyloid burdens can be therapeutically reduced