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1.
Chemosphere ; 239: 124763, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31526989

RESUMO

Nonredox metal ions have been widely recognized to be important in a wide range of biological and chemical oxidations as Lewis acids (LA). However, the role of LA in peroxymonosulfate (PMS) activation for wastewater treatment has not been considered until now. This study shows that oxidizing power of PMS can be promoted after binding nonredox metal ions such as Ca2+ as LA, leading to the easier reduction of the oxidant to radicals and substantial enhancement of dye degradation by employing manganese oxides OMS-2 as model catalysts. Increased with Lewis acidity of the metal ion, the rate of PMS decomposition enhanced linearly, while the dye degradation rate first increased and then declined due to the formation of a larger amount of dioxygen. The interactions between Ca2+ and PMS were further investigated by Raman, cyclic voltammetry and XPS; and the detailed mechanism of PMS activation was proposed. The performance of Ca2++OMS-2/PMS system under different conditions was also studied. The findings indicate the importance of LA in PMS activation reaction and their role must be considered in other transition metal oxides/PMS systems. It will be also helpful to design new and highly active catalysts for the reactions.


Assuntos
Ácidos de Lewis/química , Compostos de Manganês/química , Óxidos/química , Peróxidos/química , Poluentes Químicos da Água/química , Cálcio/química , Catálise , Corantes/química , Oxidantes/química , Oxirredução , Soluções , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química
2.
Food Chem ; 306: 125578, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31622835

RESUMO

Oleosomes are storage vehicles of TAGs in plant seeds. They are protected with a phospholipid-protein monolayer and extracted with alkaline aqueous media; however, pH adjustment intensifies the extraction process. Therefore, the aim of this work was to investigate the extraction mechanism of rapeseed oleosomes at pH 7 and at the presence of monovalent and divalent cations (Na+, K+, Mg2+, and Ca+2). The oleosome yield at pH 9.5 was 64 wt%, while the yield at pH 7 with H2O was just 43 wt.%. The presence of cations at pH 7, significantly enhanced the yield, with K+ giving the highest yield (64 wt.%). The cations affected the oleosome interface and their interactions. The presence of monovalent cations resulted in aggregation and minor coalescence, while divalent cations resulted in extensive coalescence. These results help to understand the interactions of oleosomes in their native matrix and design simple extraction processes at neutral conditions.


Assuntos
Brassica/química , Cálcio/química , Magnésio/química , Extratos Vegetais/química , Potássio/química , Sódio/química , Cátions Bivalentes/química , Cátions Monovalentes/química , Concentração de Íons de Hidrogênio , Gotículas Lipídicas , Sementes/química , Água
3.
J Environ Sci (China) ; 86: 65-77, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31787191

RESUMO

This study revealed the relationship between the presence of calcium impurities and ammoniacal nitrogen concentration upon crystallization of struvite. The research hypothesis was that the presence of both calcium and high concentrations of ammoniacal nitrogen (328-1000 mg/L) in waste activated sludge may influence the struvite quality and acid stability. Hence, we studied the impact of Ca:Mg ratio upon morphology, particle size, purity and dissolution of struvite, in the presence of varying levels of excess ammoniacal nitrogen. X-ray diffraction revealed that up to 31.4% amorphous material was made which was assigned to hydroxyapatite. Increasing the ammoniacal nitrogen concentration and elevation of the Mg:Ca ratio maximized the presence of struvite. Struvite particle size was also increased by ammoniacal nitrogen as was twinning of the crystals. Tests with dilute solutions of organic acid revealed the sensitivity of struvite dissolution to the physical characteristics of the struvite. Smaller particles (21.2 µm) dissolved at higher rates than larger particles (35.86 µm). However, struvite dissolved rapidly as the pH was further reduced irrespective of the physical characteristics. Therefore, addition of struvite to low pH soils was not viewed as beneficial in terms of controlled nutrient release. Overall, this study revealed that waste activated sludge effluent with high ammoniacal nitrogen was prospective for synthesis of high quality struvite material.


Assuntos
Cálcio/química , Magnésio/química , Nitrogênio/química , Estruvita/química , Eliminação de Resíduos Líquidos/métodos
4.
J Chem Theory Comput ; 15(12): 6992-7003, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31714772

RESUMO

Di/triphosphates perform a multitude of essential tasks, being important components of many vital organic cofactors such as adenosine/guanosine di/triphosphate (ADP/GDP, ATP/GTP), flavin adenine dinucleotide, and nicotinamide adenine dinucleotide and its phosphate derivative. They are generally bound to cations inside cells, in particular Mg2+ in the case of ATP/GTP. Yet how their metal-binding modes depend on the number, charge, and solvent exposure of the polyphosphate group and how Mg2+and Ca2+ dications that coexist in cellular fluids compete for di/triphosphates in biological systems remain elusive. Using density functional theory calculations combined with a polarizable continuum model, we have determined the relative free energies and stabilities of the different binding modes of di- and triphosphate groups to Mg2+ and Ca2+. We show that the thermodynamic outcome of the competition between Mg2+ and Ca2+ for cellular di/triphosphates depends mainly on the oligomericity/charge and metal-binding mode of the phosphate ligand as well as the solvent exposure of the binding site. Increasing the charge and thus denticity of the phosphate ligand from bi- to tridentate in a buried binding pocket enhances the affinity of the host system for the stronger charge acceptor, Mg2+. The cellular di/triphosphates's intrinsic properties and the protein matrix allowing them to bind a dication bi/tridentately, along with the higher cytosolic concentration of Mg2+ compared to Ca2+, enables Mg2+ to outcompete Ca2+ in binding to these highly charged anions. This suggests an explanation for why nature has chosen Mg2+ but not Ca2+ to perform most of the essential tasks associated with biological triphosphates.


Assuntos
Difosfato de Adenosina/química , Trifosfato de Adenosina/química , Cálcio , Guanosina Difosfato/química , Guanosina Trifosfato/química , Magnésio/química , Sítios de Ligação , Cálcio/química , Bases de Dados de Proteínas , Teoria da Densidade Funcional , Termodinâmica
5.
Adv Exp Med Biol ; 1206: 151-166, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31776984

RESUMO

Controlled by a strict mechanism, intracellular calcium (Ca(2+)) is closely related to various cellular activities, including the regulation of autophagy. Researchers believed that under normal or stress state, Ca(2+) has a positive or negative regulation effect on autophagy, the mechanisms of which are different. This bidirectional role of Ca(2+), promotive or suppressing in the regulation of autophagy under different conditions remains controversial, so as the potential mechanisms. Several studies reported that Ca(2+) promotes autophagy through plenty of ways, like inositol 1,4,5-trisphosphate receptor (IP3R) and beclin1 pathway, calmodulin-dependent kinase kinase beta (CaMKKß)-AMPK-mTOR pathway, mitochondrial energy metabolism-related Ca(2+) uptake, lysosome's regulation of Ca(2+) signal, and so on. Others thought Ca(2+) may inhibit autophagy through IP3R and beclin1-Bcl-2 complex and the AMPK-mTOR pathway, either. It seems to be still a long way to thoroughly understand the truth of Ca(2+) and autophagy.


Assuntos
Autofagia , Cálcio , Animais , Autofagia/fisiologia , Cálcio/química , Íons/química , Transdução de Sinais
6.
Environ Monit Assess ; 191(12): 754, 2019 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-31734742

RESUMO

In peri-urban areas, the use of wastewater for crop production is a common practice due to water scarcity. Moreover, in the recent years, large quantity of wastewater generation and discharge as industrial effluent in water resources is another issue for reduction of water quality. The leather industries are significantly contributing chromium (Cr) in effluent, whereas, other industries may have salt and cationic load in their discharges are mixed up. Therefore, it is mandatory to study the interactive effect of different effluent constituents on crop plants. In this connection, a pot culture experiment was conducted at the ICAR-Indian Institute of Soil Science, Bhopal to compute the effect of application of calcium (Ca) and sodium (Na) ions on Cr uptake by spinach crop in Vertisol of central India. Three levels of Cr (0, 50, 100 mg kg-1), calcium (0, 2, 4 mM), and sodium (0, 40, 80 mM) were applied in combinations. The spinach variety All Green was used as a test crop and harvested at full maturity. Results showed that application of Ca and Na reduced the Cr uptake in spinach crop. The reduction of Cr uptake was more in the root than shoot. Applied calcium acted as an essential plant nutrient and enhanced the crop biomass. Sole applications of Na adversely affected the crop biomass and Cr uptake in both root and shoot of spinach. In conclusion, application of Ca fertilizers reduced the Cr toxicity in spinach and could be used as a strategy for the safe utilization of tannery industrial effluents for crop production.


Assuntos
Cálcio/química , Cromo/metabolismo , Produção Agrícola/métodos , Sódio/química , Poluentes do Solo/análise , Spinacia oleracea/química , Biomassa , Monitoramento Ambiental , Fertilizantes/análise , Índia , Raízes de Plantas/química , Águas Residuárias/química
7.
J Agric Food Chem ; 67(44): 12283-12292, 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31610118

RESUMO

In this study, the binding mechanism, morphological, and conformational analysis of the complex of a sea cucumber ovum derived octapeptide (EDLAALEK) with Ca2+ as well as its calcium delivery behavior via the gastrointestinal (GI) tract were investigated. The Ca2+ specifically bound to two carboxyl oxygen atoms of C-terminal Glu and Asp on the EDLAALEK peptide at a stoichiometric ratio of 1:1. Calcium coordination induced the self-assembly of the EDLAALEK peptide, resulting in the formation of a nanocomposite with a crystal structure. Furthermore, the formed nanocomposite went through dissociation and self-assembly during in vitro GI digestion, accompanied by the release and rechelation of Ca2+, which was related to changes in their secondary structure. Nevertheless, the GI digests of the EDLAALEK-calcium complex could significantly enhance Ca2+ absorption across Caco-2 cell monolayers. The findings suggest that the sea cucumber ovum derived peptide has the potential as an efficient nanocarrier to transport calcium through the GI system.


Assuntos
Cálcio/química , Nanoestruturas/química , Óvulo/química , Peptídeos/química , Pepinos-do-Mar/química , Animais , Transporte Biológico , Células CACO-2 , Cálcio/metabolismo , Trato Gastrointestinal/metabolismo , Humanos
8.
Anal Bioanal Chem ; 411(28): 7419-7430, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31494687

RESUMO

Substance P (SP) is one of the most studied peptide hormones and knowing the relationship between its structure and function may have important therapeutic applications in the treatment of a variety of stress-related illnesses. In order to obtain a deeper insight into its folding, the effects of different factors, such as pH changes, the presence of Ca2+ ions, and the substitution of the Met-NH2 moiety in the SP structure, was studied by Raman and infrared spectroscopies. SP has a pH-dependent structure. Under acidic-neutral conditions, SP possesses a prevalent ß-sheet structure although also other secondary structure elements are present. By increasing pH, a higher orderliness in the SP secondary structure is induced, as well as the formation of strongly bound intermolecular ß-strands with a parallel alignment, which favour the self-assembly of SP in ß-aggregates. The substitution of the Met-NH2 moiety with the acidic functional group in the SP sequence, giving rise to a not biologically active SP analogue, results in a more disordered folding, where the predominant contribution comes from a random coil. Conversely, the presence of Ca2+ ions affects slightly but sensitively the folding of the polypeptide chain, by favouring the α-helical content and a different alignment of ß-strands; these are structural elements, which may favour the SP biological activity. In addition, the capability of SERS spectroscopy to detect SP in its biologically active form was also tested by using different metal nanoparticles. Thanks to the use of silver NPs prepared by reduction of silver nitrate with hydroxylamine hydrochloride, SP can be detected at very low peptide concentration (~ 90 nM). However, the SERS spectra cannot be obtained under alkaline conditions since both the formation of SP aggregates and the lack of ion pairs do not allow a strong enough interaction of SP with silver NPs. Graphical abstract.


Assuntos
Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Substância P/química , Vibração , Cálcio/química , Conformação Proteica , Análise Espectral Raman/métodos
9.
Nat Commun ; 10(1): 3956, 2019 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-31477691

RESUMO

Membranes in cells have defined distributions of lipids in each leaflet, controlled by lipid scramblases and flip/floppases. However, for some intracellular membranes such as the endoplasmic reticulum (ER) the scramblases have not been identified. Members of the TMEM16 family have either lipid scramblase or chloride channel activity. Although TMEM16K is widely distributed and associated with the neurological disorder autosomal recessive spinocerebellar ataxia type 10 (SCAR10), its location in cells, function and structure are largely uncharacterised. Here we show that TMEM16K is an ER-resident lipid scramblase with a requirement for short chain lipids and calcium for robust activity. Crystal structures of TMEM16K show a scramblase fold, with an open lipid transporting groove. Additional cryo-EM structures reveal extensive conformational changes from the cytoplasmic to the ER side of the membrane, giving a state with a closed lipid permeation pathway. Molecular dynamics simulations showed that the open-groove conformation is necessary for scramblase activity.


Assuntos
Anoctaminas/metabolismo , Retículo Endoplasmático/metabolismo , Lipídeos/química , Proteínas de Transferência de Fosfolipídeos/metabolismo , Sequência de Aminoácidos , Animais , Anoctaminas/química , Anoctaminas/genética , Células COS , Cálcio/química , Linhagem Celular Tumoral , Cristalografia por Raios X , Células HEK293 , Humanos , Simulação de Dinâmica Molecular , Proteínas de Transferência de Fosfolipídeos/química , Proteínas de Transferência de Fosfolipídeos/genética , Homologia de Sequência de Aminoácidos , Células Sf9 , Spodoptera
10.
Phys Chem Chem Phys ; 21(36): 19795-19804, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31482888

RESUMO

Allostery plays important roles in the regulation of many biological processes, such as signal transduction and transcriptional regulation. Although great advances have been achieved in understanding the allosteric mechanism through experimental and theoretical investigations, the details of the allosteric process are still not clear. Here, using the N-terminal domain of calmodulin (nCaM) as the model protein, we reported the atomic level characterization of the allosteric process induced by Ca2+ binding through extensive and unbiased molecular dynamics simulations. In two trajectories, it was found that Ca2+ first binds to EF-hand 2 and then induces the conformational transformation of nCaM from the Apo to Holo state assisted by second Ca2+ binding to EF-hand 1 completely. The binding order was consistent with a recent experimental result. The simulations also indicated that the two EF-hands changed conformations synergistically and the EF-hand 2 showed an earlier and more gradual conformational transition. Meanwhile, the allosteric process of nCaM triggered by Ca2+ binding might be completed within hundreds of nanoseconds in a two-state-like manner. This was validated by biased simulations, in which the Ca2+ ions were restrained near the binding sites. This work provides the molecular details of the conformational transition of nCaM triggered by Ca2+ binding.


Assuntos
Cálcio/química , Calmodulina/química , Íons/química , Simulação de Acoplamento Molecular , Domínios Proteicos , Ligação Proteica , Conformação Proteica
11.
Phys Chem Chem Phys ; 21(39): 21991-21995, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31552962

RESUMO

The sarcoplasmic reticulum Ca2+-ATPase (SERCA) is a widely studied member of the large family of phosphorylation(P)-type ATPase membrane transporters. Ligands and nucleotide binding naturally modulate the conformational space of P-type ATPases through allosteric inter-domain communications. Whereas many inhibitory ATPase ligands act by directly blocking substrate uptake or release, SERCA is a target for thapsigargin (TG), a plant-derived natural product that allosterically inhibits the transport cycle. While thapsigargin's inhibitory effects on SERCA have been widely studied experimentally, the molecular mechanisms underlying these remain incompletely understood. Here, we apply modelling and molecular simulations to probe the effects of TG binding to the major functional states along SERCA's reaction cycle. Our results provide insight into the atomic-level details of the conformational changes induced by TG binding to SERCA, and suggest mechanisms for its effect. Since other P-type ATPases share closely related reaction cycles, our data suggests that similar modulators might exist for these.


Assuntos
Inibidores Enzimáticos/química , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/antagonistas & inibidores , Tapsigargina/química , Sítio Alostérico , Transporte Biológico , Cálcio/química , Cátions Bivalentes/química , Simulação de Dinâmica Molecular , Ligação Proteica , Conformação Proteica , Transdução de Sinais
12.
Water Sci Technol ; 80(1): 117-125, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31461428

RESUMO

In this study the removal of phosphates from solution by Donnan dialysis and by adsorption onto calcium alginate beads were studied separately and then together. This hybrid process was conducted in order to benefit from each process, and it is an original and new combination. First, the Donnan dialysis process was performed with different parameters: the type of counter-ion, the concentration of the counter-ion, the initial phosphate concentration, the pH of the solution and the choice of anion-exchange membranes. Donnan dialysis achieved 68% and 12.5% phosphorus removal with AMX and AFN membranes respectively. Then a preliminary study into the adsorption of phosphate onto calcium alginate beads was carried out. A full factor design was applied in order to determine the effect of the main parameters and their mutual interactions for the adsorption process. The removal of phosphate onto calcium alginate beads reached 82.5%. Finally, coupling Donnan dialysis with adsorption onto calcium alginate beads for the removal of phosphate reached 89.5% with the AMX membrane. This hybrid process can be considered to be a solution for improving the contact time and for enhancing the removal of phosphate by 10% compared to adsorption onto calcium alginate.


Assuntos
Alginatos , Fosfatos/química , Purificação da Água/métodos , Adsorção , Cálcio/química , Diálise , Ácido Glucurônico , Ácidos Hexurônicos , Concentração de Íons de Hidrogênio , Fosfatos/análise
13.
Int J Mol Sci ; 20(17)2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31461891

RESUMO

Matrix metaloproteinase-2 (MMP-2) is an extracellular Zn2+ protease specific to type I and IV collagens. Its expression is associated with several inflammatory, degenerative, and malignant diseases. Conformational properties, domain movements, and interactions between MMP-2 and its associated metal ions were characterized using a 1.0 µs molecular dynamics simulation. Dihedral principle component analysis revealed ten families of conformations with the greatest degree of variability occurring in the link region connecting the catalytic and hemopexin domains. Dynamic cross-correlation analysis indicated domain movements corresponding to the opening and closing of the hemopexin domain in relation to the fibronectin and catalytic domains facilitated by the link region. Interaction energies were calculated using the molecular mechanics Poisson Boltzman surface area-interaction entropy (MMPBSA-IE) analysis method and revealed strong binding energies for the catalytic Zn2+ ion 1, Ca2+ ion 1, and Ca2+ ion 3 with significant conformational stability at the binding sites of Zn2+ ion 1 and Ca2+ ion 1. Ca2+ ion 2 diffuses freely away from its crystallographically defined binding site. Zn2+ ion 2 plays a minor role in conformational stability of the catalytic domain while Ca2+ ion 3 is strongly attracted to the highly electronegative sidechains of the Asp residues around the central ß-sheet core of the hemopexin domain; however, the interacting residue sidechain carboxyl groups are outside of Ca2+ ion 3's coordination sphere.


Assuntos
Metaloproteinase 2 da Matriz/química , Simulação de Dinâmica Molecular , Sítios de Ligação , Cálcio/química , Cálcio/metabolismo , Humanos , Metaloproteinase 2 da Matriz/metabolismo , Simulação de Acoplamento Molecular , Ligação Proteica , Zinco/química , Zinco/metabolismo
14.
J Dairy Res ; 86(3): 374-376, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31439054

RESUMO

In this Research Communication we present a study of the effect of Ca-binding salts on the recovery of milk fat globule membrane (MFGM) from buttermilk. Sodium phosphate buffer was used for the purpose of MFGM recovery from buttermilk for the first time and we showed that 0.1 M buffer at pH 7.2 was the most effective for the recovery of MFGM. The fact of high efficacy of sodium phosphate buffer in recovery of MFGM from buttermilk allowed us to suggest that MFGM in buttermilk is present in association with casein through Ca- bridges formed between phospholipids of MFGM and phosphate groups of casein, primarily with k-casein as the peripheral protein of casein micelles.


Assuntos
Leitelho/análise , Cálcio/química , Glicolipídeos/isolamento & purificação , Glicoproteínas/isolamento & purificação , Fosfatos , Animais , Tampões (Química) , Caseínas/química , Suplementos Nutricionais/análise , Manipulação de Alimentos/métodos , Fosfatos/química , Fosfolipídeos/química
15.
Int J Mol Sci ; 20(15)2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31374825

RESUMO

Because Mg-Ca-Zn alloys are biodegradable and obviate secondary implant removal, they are especially beneficial for pediatric patients. We examined the degradation performance of Mg-Ca-Zn alloys depending on the surface modification and investigated the in vivo effects on the growth plate in a skeletally immature rabbit model. Either plasma electrolyte oxidation (PEO)-coated (n = 18) or non-coated (n = 18) Mg-Ca-Zn alloy was inserted at the distal femoral physis. We measured the degradation performance and femoral segment lengths using micro-CT. In addition, we analyzed the histomorphometric and histopathologic characteristics of the growth plate. Although there were no acute, chronic inflammatory reactions in either group, they differed significantly in the tissue reactions to their degradation performance and physeal responses. Compared to non-coated alloys, PEO-coated alloys degraded significantly slowly with diminished hydrogen gas formation. Depending on the degradation rate, large bone bridge formation and premature physeal arrest occurred primarily in the non-coated group, whereas only a small-sized bone bridge formed in the PEO-coated group. This difference ultimately led to significant shortening of the femoral segment in the non-coated group. This study suggests that optimal degradation could be achieved with PEO-coated Mg-Ca-Zn alloys, making them promising and safe biodegradable materials with no growth plate damage.


Assuntos
Implantes Absorvíveis , Ligas/química , Cálcio/química , Lâmina de Crescimento/fisiologia , Magnésio/química , Zinco/química , Animais , Pinos Ortopédicos , Materiais Revestidos Biocompatíveis/química , Eletrólitos/química , Lâmina de Crescimento/ultraestrutura , Teste de Materiais , Oxirredução , Coelhos , Propriedades de Superfície
16.
Biochim Biophys Acta Bioenerg ; 1860(10): 148059, 2019 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-31394097

RESUMO

Based on characterization by X-ray absorption spectroscopy, it has been proposed that the Mn4CaO5 cluster in the crystal structure of the water-oxidizing enzyme, photosystem II (PSII), may represent an over-reduced form arising from reduction by the X-ray beam. Using a quantum mechanical/molecular mechanical approach, and assuming that all of the µ-oxo bridges are deprotonated in S1, we analyzed the reduction process of the Mn4CaO5 cluster. In the crystal structure, the O atom (O5), which is linked with three Mn atoms and one Ca atom, has no H-bond. When reduced to S-2, unexpectedly, a water molecule at Ca2+ (W3) reoriented itself, formed a H-bond with O5, and released a proton to O5, resulting in formation of OH- at both W3 and O5. Once generated, the OH- group at O5 was stable, because the W3…O5 H-bond had already disappeared. A weak binding of H2O at Ca2+ led W3 to reorient and serve as a proton donor to O5 upon over-reduction.


Assuntos
Cianobactérias/química , Modelos Moleculares , Complexo de Proteína do Fotossistema II/química , Cálcio/química , Ligações de Hidrogênio , Manganês/química , Oxigênio/química , Prótons , Água/química
17.
Biophys Chem ; 254: 106246, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31426023

RESUMO

The inhibitory effect of the flavonoid naringenin on plant and human Two-Pore Channels (TPCs) was assessed by means of electrophysiological measurements. By acting on human TPC2, naringenin, was able to dampen intracellular calcium responses to VEGF in cultured human endothelial cells and to impair angiogenic activity in VEGF-containing matrigel plugs implanted in mice. Molecular docking predicts selective binding sites for naringenin in the TPC structure, thus suggesting a specific interaction between the flavonoid and the channel.


Assuntos
Canais de Cálcio/química , Flavanonas/química , Plantas/metabolismo , Animais , Sítios de Ligação , Cálcio/química , Cálcio/metabolismo , Canais de Cálcio/metabolismo , Colágeno/química , Combinação de Medicamentos , Células Endoteliais/citologia , Células Endoteliais/metabolismo , Flavanonas/metabolismo , Humanos , Laminina/química , Camundongos , Simulação de Acoplamento Molecular , Técnicas de Patch-Clamp , Proteínas de Plantas/antagonistas & inibidores , Proteínas de Plantas/metabolismo , Proteoglicanas/química
18.
Int J Mol Sci ; 20(16)2019 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-31426343

RESUMO

Four kinds of Ca-montmorillonite with different layer charge density were used to study the effect of charge density on their hydration properties by molecular dynamics simulation and experiments. The research results of Z-density distribution of water molecules, Hw (hydrogen in water molecules), and Ca in the interlayer of montmorillonite show that the hydration properties of montmorillonite are closely related to its layer charge density. If the charge density is low, the water molecules in the interlayers are mainly concentrated on the sides of the central axis about -1.3 Å and 1.5 Å. As the charge density increases from 0.38semi-cell to 0.69semi-cell, the water molecules are distributed -2.5 Å and 2.4 Å away from the siloxane surface (Si-O), the concentration of water molecules near the central axis decreases, and at the same time, Ca2+ appears to gradually shift from the vicinity of the central axis to the Si-O surface on both sides in the montmorillonite layer. The simulation results of the radial distribution function (RDF) of the Ca-Hw, Ca-Ow (oxygen in water molecules), and Ca-Ot (the oxygen in the tetrahedron) show that the Ca2+ and Ow are more tightly packed together than that of Hw; with the increase of the charge density, due to the fact that the negative charge sites on the Si-O surface increase, under the action of electrostatic attraction, some of the Ca2+ are pulled towards the Si-O surface, which is more obvious when the layer charge density of the montmorillonite is higher. The results of the RDF of the Ot-Hw show that with the increase of charge density, the number of hydrogen bonds formed by Ot and Hw in the interlayers increase, and under the action of hydrogen bonding force, the water molecules near the central axis are pulled towards the two sides of Si-O surface. As a result, the arrangement of water molecules is more compact, and the structure is obvious. Correspondingly, the self-diffusion coefficient shows that the higher the layer charge density, the lower the self-diffusion coefficient of water molecules in interlayers is and the worse the hydration performance of montmorillonite. The experimental results of the experiments fit well with the above simulation results.


Assuntos
Bentonita/química , Água/química , Adsorção , Cálcio/química , Cátions Bivalentes/química , Ligações de Hidrogênio , Simulação de Dinâmica Molecular , Siloxanas/química , Propriedades de Superfície
19.
Carbohydr Polym ; 223: 115062, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31426967

RESUMO

Nata de coco was chemically modified to afford the bacterial cellulose hydrogels carrying terminal alkynes. The resultant hydrogels were then converted into hydrogels carrying lactosides or those carrying α-2,3-sialyllactosides by the Cu+-catalyzed alkyne-azide cyclization. The stable homo association of the hydrogels carrying lactosides was observed in an aqueous solution containing Ca2+, thereby demonstrating the Ca2+-mediated lactoside-lactoside interactions. Ca2+ also stabilized the hetero associations among the hydrogels carrying lactosides and those carrying α-2,3-sialyllactosides, thereby also demonstrating the Ca2+-induced interactions between the lactosides and the α-2,3-sialyllactosides. The sizes of these hydrogels were of the order of ca. 5 mm, and their associations could thus be readily monitored with the naked eye.


Assuntos
Celulose/química , Hidrogéis/química , Oligossacarídeos/química , Polissacarídeos Bacterianos/química , Alquinos/química , Azidas/química , Cálcio/química , Cocos/química , Cocos/microbiologia , Hidrogéis/síntese química , Magnésio/química , Lectinas de Plantas/química , Ricinus/química , Sódio/química
20.
Phys Chem Chem Phys ; 21(38): 21213-21222, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31418759

RESUMO

Trivalent actinides and their lanthanide homologues are being scrutinized for their potential health risk when ingested as a result of a range of industrial activities such as mining. Importantly, these ions are known to exhibit high affinity towards calmodulin (CaM). In case of their inadvertent uptake, the holoproteins that are occupied by these cations may block signal transduction pathways or increase the concentration of these ions in intact cells, which could lead to accumulation in human organs. Accordingly, this investigation employed spectroscopy, computational chemistry, calorimetry, and biochemistry to study the results of metal ion substitution on the protein structure, enzymatic activity and chemo- and cytotoxicity of An3+/Ln3+ ions. As will be demonstrated herein, our data confirm the higher affinity of Cm3+ and Eu3+ compared to Ca2+ to all 4 binding sites of CaM, with one site differing from the remaining three. This higher-affinity site will complex Eu3+ in an exothermic fashion; in contrast, ion binding to the three lower-affinity EF-hands was found to be endothermic. The overall endothermic binding process is ascribed to the loss of the hydration shells of the trivalent ions upon protein binding. These findings are supported by extensive quantum chemical calculations of full holo-CaM, which were performed at the MP2 level using the fragment molecular orbital method. The exceptional binding site (EF-hand 3) features fewer negatively charged residues compared to the other EF-hands, thereby allowing Eu3+ and Cm3+ to carry one or two additional waters compared to Ca2+-CaM, while also causing the structure of Cm3+/Eu3+-CaM to become slightly disordered. Moreover, the enzymatic activity decreases somewhat in comparison to Ca2+-CaM. By utilizing a combination of techniques, we were able to generate a comprehensive picture of the CaM-actinide/lanthanide system from the molecular level to its functional impact. Such knowledge could also be applied to other metal-binding proteins.


Assuntos
Calmodulina/química , Calmodulina/metabolismo , Cúrio/química , Európio/química , Sítios de Ligação , Cálcio/química , Cátions , Simulação de Dinâmica Molecular , Conformação Proteica , Água
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