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1.
Gels ; 8(3)2022 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-35323299

RESUMO

The removal of arsenate ions from aqueous solutions at near-neutral pH was carried out using chitosan-magnetite (ChM) hydrogel beads in batch systems. Equilibrium isotherms and kinetic studies are reported. Obtained equilibrium and kinetic data were fitted to mathematical models, estimating model parameters by non-linear regression analysis. Langmuir model was found to best fit equilibrium data; a maximum adsorption capacity of 66.9 mg As/g was estimated at pH 7.0. Pseudo-first order kinetic model was observed to best fit kinetic data. The pH of the solution was observed to increase with increasing contact time, which is attributed to protonation of amine groups present in the hydrogel. Protonation of functional groups in the ChM sorbent yields a higher number of active sites for arsenate removal, being as this a process that can't be overlooked in future applications of ChM hydrogel for the removal or arsenate ions. Chitosan-magnetite and ChM-arsenate interactions were determined by XPS. Arsenate removal using fixed-bed column packed with ChM was carried out, reporting a non-ideal behavior attributed to pH increase of the effluent caused by proton transfer to ChM hydrogels.

2.
Diabetes ; 67(6): 1128-1139, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29563152

RESUMO

Adrenaline is a powerful stimulus of glucagon secretion. It acts by activation of ß-adrenergic receptors, but the downstream mechanisms have only been partially elucidated. Here, we have examined the effects of adrenaline in mouse and human α-cells by a combination of electrophysiology, imaging of Ca2+ and PKA activity, and hormone release measurements. We found that stimulation of glucagon secretion correlated with a PKA- and EPAC2-dependent (inhibited by PKI and ESI-05, respectively) elevation of [Ca2+]i in α-cells, which occurred without stimulation of electrical activity and persisted in the absence of extracellular Ca2+ but was sensitive to ryanodine, bafilomycin, and thapsigargin. Adrenaline also increased [Ca2+]i in α-cells in human islets. Genetic or pharmacological inhibition of the Tpc2 channel (that mediates Ca2+ release from acidic intracellular stores) abolished the stimulatory effect of adrenaline on glucagon secretion and reduced the elevation of [Ca2+]i Furthermore, in Tpc2-deficient islets, ryanodine exerted no additive inhibitory effect. These data suggest that ß-adrenergic stimulation of glucagon secretion is controlled by a hierarchy of [Ca2+]i signaling in the α-cell that is initiated by cAMP-induced Tpc2-dependent Ca2+ release from the acidic stores and further amplified by Ca2+-induced Ca2+ release from the sarco/endoplasmic reticulum.


Assuntos
Canais de Cálcio/metabolismo , Sinalização do Cálcio , Epinefrina/metabolismo , Células Secretoras de Glucagon/metabolismo , Glucagon/metabolismo , Regulação para Cima , Neurônios Adrenérgicos/citologia , Neurônios Adrenérgicos/efeitos dos fármacos , Neurônios Adrenérgicos/metabolismo , Animais , Animais não Endogâmicos , Canais de Cálcio/química , Canais de Cálcio/genética , Sinalização do Cálcio/efeitos dos fármacos , Proteínas Quinases Dependentes de AMP Cíclico/antagonistas & inibidores , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Retículo Endoplasmático/efeitos dos fármacos , Retículo Endoplasmático/enzimologia , Retículo Endoplasmático/metabolismo , Inibidores Enzimáticos/farmacologia , Células Secretoras de Glucagon/citologia , Células Secretoras de Glucagon/efeitos dos fármacos , Fatores de Troca do Nucleotídeo Guanina/antagonistas & inibidores , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Humanos , Moduladores de Transporte de Membrana/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Pâncreas/efeitos dos fármacos , Pâncreas/inervação , Pâncreas/metabolismo , Técnicas de Patch-Clamp , Retículo Sarcoplasmático/efeitos dos fármacos , Retículo Sarcoplasmático/enzimologia , Retículo Sarcoplasmático/metabolismo , Técnicas de Cultura de Tecidos , Regulação para Cima/efeitos dos fármacos
4.
Biochim Biophys Acta ; 1798(3): 327-37, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19631190

RESUMO

We have identified a membrane-active region in the HCV NS4B protein by studying membrane rupture induced by a NS4B-derived peptide library on model membranes. This segment corresponds to one of two previously predicted amphipathic helix and define it as a new membrane association domain. We report the binding and interaction with model membranes of a peptide patterned after this segment, peptide NS4B(H2), and show that NS4B(H2) strongly partitions into phospholipid membranes, interacts with them, and is located in a shallow position in the membrane. Furthermore, changes in the primary sequence cause the disruption of the hydrophobicity along the structure and prevent the resulting peptide from interacting with the membrane. Our results suggest that the region where the NS4B(H2) is located might have an essential role in the membrane replication and/or assembly of the viral particle through the modulation of the replication complex. Our findings therefore identify an important region in the HCV NS4B protein which might be implicated in the HCV life cycle and possibly in the formation of the membranous web.


Assuntos
Hepacivirus/metabolismo , Membranas Artificiais , Proteínas não Estruturais Virais/química , Proteínas não Estruturais Virais/metabolismo , Sequência de Aminoácidos , Anisotropia , Varredura Diferencial de Calorimetria , Fluoresceínas/metabolismo , Fluorescência , Interações Hidrofóbicas e Hidrofílicas , Cinética , Dados de Sequência Molecular , Peptídeos/química , Ligação Proteica , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Alinhamento de Sequência , Soluções , Espectrofotometria Infravermelho , Triptofano/metabolismo
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