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1.
Nat Commun ; 11(1): 3944, 2020 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-32769983

RESUMO

Triacylglycerols (TG) are synthesized at the endoplasmic reticulum (ER) bilayer and packaged into organelles called lipid droplets (LDs). LDs are covered by a single phospholipid monolayer contiguous with the ER bilayer. This connection is used by several monotopic integral membrane proteins, with hydrophobic membrane association domains (HDs), to diffuse between the organelles. However, how proteins partition between ER and LDs is not understood. Here, we employed synthetic model systems and found that HD-containing proteins strongly prefer monolayers and returning to the bilayer is unfavorable. This preference for monolayers is due to a higher affinity of HDs for TG over membrane phospholipids. Protein distribution is regulated by PC/PE ratio via alterations in monolayer packing and HD-TG interaction. Thus, HD-containing proteins appear to non-specifically accumulate to the LD surface. In cells, protein editing mechanisms at the ER membrane would be necessary to prevent unspecific relocation of HD-containing proteins to LDs.


Assuntos
Membrana Celular/metabolismo , Bicamadas Lipídicas/metabolismo , Gotículas Lipídicas/metabolismo , Proteínas de Membrana/metabolismo , Triglicerídeos/metabolismo , Dicroísmo Circular , Retículo Endoplasmático/metabolismo , Proteínas de Membrana/química , Simulação de Dinâmica Molecular , Domínios Proteicos , Transporte Proteico , Triglicerídeos/química
2.
Nat Commun ; 11(1): 4169, 2020 08 20.
Artigo em Inglês | MEDLINE | ID: mdl-32820172

RESUMO

Sensing and responding to temperature is crucial in biology. The TRPV1 ion channel is a well-studied heat-sensing receptor that is also activated by vanilloid compounds, including capsaicin. Despite significant interest, the molecular underpinnings of thermosensing have remained elusive. The TRPV1 S1-S4 membrane domain couples chemical ligand binding to the pore domain during channel gating. Here we show that the S1-S4 domain also significantly contributes to thermosensing and couples to heat-activated gating. Evaluation of the isolated human TRPV1 S1-S4 domain by solution NMR, far-UV CD, and intrinsic fluorescence shows that this domain undergoes a non-denaturing temperature-dependent transition with a high thermosensitivity. Further NMR characterization of the temperature-dependent conformational changes suggests the contribution of the S1-S4 domain to thermosensing shares features with known coupling mechanisms between this domain with ligand and pH activation. Taken together, this study shows that the TRPV1 S1-S4 domain contributes to TRPV1 temperature-dependent activation.


Assuntos
Temperatura Alta , Ativação do Canal Iônico/fisiologia , Canais de Cátion TRPV/metabolismo , Sensação Térmica/fisiologia , Sítios de Ligação/genética , Capsaicina/química , Capsaicina/metabolismo , Dicroísmo Circular , Humanos , Ativação do Canal Iônico/genética , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Ligação Proteica , Domínios Proteicos , Canais de Cátion TRPV/química , Canais de Cátion TRPV/genética , Sensação Térmica/genética
3.
Int J Nanomedicine ; 15: 5083-5095, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32764938

RESUMO

Background: ß-glucans are chiral polysaccharides with well-defined immunological properties and supramolecular wrapping ability of its chiral feature. However, the exploitation of chiral properties of these nanoparticles in drug delivery systems was seldom conducted. Methods: ß-glucan molecules with different chain lengths were extracted from yeast Saccharomyces cerevisiae and thereafter modified. In a conformation transition process, these ß-glucan molecules were then self-assembled with anti-cancer drug doxorubicin into nanoparticles to construct drug delivery systems. The chiral interactions between the drug and carriers were revealed by circular dichroism spectra, ultraviolet and visible spectrum, fourier transform infrared spectroscopy, dynamic light scattering and transmission electron microscope. The immune-potentiation properties of modified ß-glucan nanoparticles were evaluated by analysis of the mRNA expression in RAW264.7 cell model. Further, the antitumor efficacy of the nanoparticles against the human breast cancer were studied in MCF-7 cell model by cellular uptake and cytotoxicity experiments. Results: ß-glucan nanoparticles can activate macrophages to produce immune enhancing cytokines (IL-1ß, IL-6, TNF-α, IFN-γ). A special chirality of the carriers in diameter of 50~160 nm can also associate with higher drug loading ability of 13.9% ~38.2% and pH-sensitive release with a change of pH from 7.4 to 5.0. Cellular uptake and cytotoxicity experiments also prove that the chiral-active ß-glucan nanoparticles can be used in anti-cancer nanomedicine. Conclusion: This work demonstrates that ß-glucans nanoparticles with special chiral feature which leading to strong immunopotentiation ability and high drug loading efficiency can be developed as a novel type of nanomedicine for anti-cancer treatment.


Assuntos
Adjuvantes Imunológicos/administração & dosagem , Antineoplásicos/administração & dosagem , Doxorrubicina/administração & dosagem , Sistemas de Liberação de Medicamentos/métodos , Nanopartículas/administração & dosagem , beta-Glucanas/imunologia , Adjuvantes Imunológicos/química , Animais , Antineoplásicos/imunologia , Dicroísmo Circular , Portadores de Fármacos/química , Humanos , Células MCF-7 , Camundongos , Nanopartículas/química , Células RAW 264.7 , Saccharomyces cerevisiae/química , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier , Estereoisomerismo , beta-Glucanas/química
4.
Int J Nanomedicine ; 15: 5203-5215, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32801686

RESUMO

Introduction: Metformin is an ideal candidate to treat the liver tumor with insulin resistance because of its good performance in the treatment of type 2 diabetes and the advantage in cancer therapy. We aim to develop a delivery system with higher efficiency than free drug. Methods: Metformin-bovine serum albumin (met-BSA) nanoparticles (NPs) were prepared using the anti-solvent precipitation method with a stabilizer of BSA for particle growth. The therapeutic effect of the drug was tested by the insulin-resistant HepG2 cells and C57BL/6J mice at a glucose starvation condition. The interaction mechanism of the drug and the protein during the formation of the NPs was tested using a series of spectroscopy. Results: Metformin and BSA formed nonporous and spherical particles of about 200 nm with proper lognormal distribution and thermostability. The cellular uptake, as well as the anti-liver cancer activities of met-BSA, was enhanced dramatically compared with the free drug. The thermodynamic studies suggested that the weak binding of metformin to BSA was governed by hydrogen bonds and van der Waals forces. Moreover, the results of synchronous, circular dichroism (CD) and three-dimensional fluorescence demonstrated that the BSA skeleton and chromophore microenvironments were changed in the presence of metformin. Conclusion: Therefore, met-BSA has been proved as a simple yet effective therapeutic agent for cancer with insulin resistance, promising for future clinic translations in cancer treatment.


Assuntos
Sistemas de Liberação de Medicamentos/métodos , Resistência à Insulina , Metformina/farmacologia , Nanopartículas/administração & dosagem , Soroalbumina Bovina/farmacologia , Animais , Carcinoma Hepatocelular/tratamento farmacológico , Carcinoma Hepatocelular/patologia , Dicroísmo Circular , Diabetes Mellitus Tipo 2 , Células Hep G2 , Humanos , Ligação de Hidrogênio , Neoplasias Hepáticas/tratamento farmacológico , Neoplasias Hepáticas/patologia , Masculino , Metformina/administração & dosagem , Metformina/química , Camundongos Endogâmicos C57BL , Nanopartículas/química , Soroalbumina Bovina/química , Termodinâmica , Ensaios Antitumorais Modelo de Xenoenxerto
5.
Exp Parasitol ; 216: 107944, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32619431

RESUMO

Evaluation of the murine isotype antibodies is essential in subunit vaccine development because inbred mouse strains with diverse genetic backgrounds respond different to recombinant proteins. In this regard, the main goal of this study was to measuring and comparing the profile of IgG isotype responses in C57BL/6 mice. For this purpose, the extracellular region of plasmodium vivax thrombospondin-related adhesive protein (PvTRAP) gene was expressed in Escherichia coli Rosetta (DE3)-pET23a. Then, the recombinant PvTRAP alone or emulsified with Freund's complete adjuvant were applied for immunization of the C57BL/6 mice. The role of antibodies and cellular immune responses induced by recombinant PvTRAP were evaluated. The results showed the level of anti-rPvTRAP IgG2c was significantly higher than IgG2a in the groups that received rPvTRAP alone (mean OD490 = 0.798 ± 0.12 and 0.39 ± 0.1, respectively) and emulsified with CFA/IFA (mean OD490 = 1.48 ± 0.07 and 0.605 ± 0.13, respectively; P < 0.05, independent sample t-test). Additionally, the immunized mice with rPvTRAP and rPvTRAP + CFA/IFA had an intermediate-avidity IgG2a antibody but high-avidity IgG2c antibody as well as the mean of serum antibody titers results exhibited that in both rPvTRAP and rPvTRAP + CFA/IFA mouse groups, IgG2a end-point titer (1:3200 and 1:25,600, respectively) was noteworthy lower than IgG2c (1:25,600 and 1:102,400, respectively). Moreover, the results revealed the eliciting significant levels of IFN-γ (P < 0.05, independent sample t-test) and no detectable level of IL-4 in the mouse groups received rPvTRAP alone and emulsified with CFA/IFA as compared to the mouse control groups. In general, our results showed that for correctly interpreting of Th1 immune responses in C57BL/6 mouse strain it is critical to measure IgG2c instead of IgG2a along with IFN-γ.


Assuntos
Imunoglobulina G/sangue , Plasmodium vivax/imunologia , Proteínas de Protozoários/imunologia , Vacinas Protozoárias/imunologia , Células Th1/imunologia , Células Th2/imunologia , Animais , Afinidade de Anticorpos , Dicroísmo Circular , Feminino , Imunofluorescência , Imunoglobulina G/classificação , Interferon gama/análise , Interleucina-4/análise , Linfócitos/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Proteínas Recombinantes/imunologia , Vacinas de Subunidades/imunologia , Vacinas Sintéticas/imunologia
6.
PLoS One ; 15(7): e0235925, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32639967

RESUMO

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by speech impairment, intellectual disability, ataxia, and epilepsy. AS is caused by mutations in the maternal copy of UBE3A located on chromosome 15q11-13. UBE3A codes for E6AP (E6 Associated Protein), a prominent member of the HECT (Homologous to E6AP C-Terminus) E3 ubiquitin ligase family. E6AP catalyzes the posttranslational attachment of ubiquitin via its HECT domain onto various intracellular target proteins to regulate DNA repair and cell cycle progression. The HECT domain consists of an N-lobe, required for E2~ubiquitin recruitment, while the C-lobe contains the conserved catalytic cysteine required for ubiquitin transfer. Previous genetic studies of AS patients have identified point mutations in UBE3A that result in amino acid substitutions or premature termination during translation. An AS transversion mutation (codon change from ATA to AAA) within the region of the gene that codes for the catalytic HECT domain of E6AP has been annotated (I827K), but the molecular basis for this loss of function substitution remained elusive. Here, we demonstrate that the I827K substitution destabilizes the 3D fold causing protein aggregation of the C-terminal lobe of E6AP using a combination of spectropolarimetry and nuclear magnetic resonance (NMR) spectroscopy. Our fluorescent ubiquitin activity assays with E6AP-I827K show decreased ubiquitin thiolester formation and ubiquitin discharge. Using 3D models in combination with our biochemical and biophysical results, we rationalize why the I827K disrupts E6AP-dependent ubiquitylation. This work provides new insight into the E6AP mechanism and how its malfunction can be linked to the AS phenotype.


Assuntos
Síndrome de Angelman/genética , Ubiquitina-Proteína Ligases/metabolismo , Síndrome de Angelman/patologia , Biocatálise , Dicroísmo Circular , Humanos , Mutagênese Sítio-Dirigida , Ressonância Magnética Nuclear Biomolecular , Domínios Proteicos , Estabilidade Proteica , Estrutura Secundária de Proteína , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/isolamento & purificação , Ubiquitina/metabolismo , Ubiquitina-Proteína Ligases/química , Ubiquitina-Proteína Ligases/genética , Ubiquitinação
7.
PLoS Negl Trop Dis ; 14(7): e0008471, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32639964

RESUMO

In Brazil, Plasmodium vivax infection accounts for around 80% of malaria cases. This infection has a substantial impact on the productivity of the local population as the course of the disease is usually prolonged and the development of acquired immunity in endemic areas takes several years. The recent emergence of drug-resistant strains has intensified research on alternative control methods such as vaccines. There is currently no effective available vaccine against malaria; however, numerous candidates have been studied in the past several years. One of the leading candidates is apical membrane antigen 1 (AMA1). This protein is involved in the invasion of Apicomplexa parasites into host cells, participating in the formation of a moving junction. Understanding how the genetic diversity of an antigen influences the immune response is highly important for vaccine development. In this study, we analyzed the diversity of AMA1 from Brazilian P. vivax isolates and 19 haplotypes of P. vivax were found. Among those sequences, 33 nonsynonymous PvAMA1 amino acid sites were identified, whereas 20 of these sites were determined to be located in predicted B-cell epitopes. Nonsynonymous mutations were evaluated for their influence on the immune recognition of these antigens. Two distinct haplotypes, 5 and 16, were expressed and evaluated for reactivity in individuals from northern Brazil. Both PvAMA1 variants were reactive. Moreover, the IgG antibody response to these two PvAMA1 variants was analyzed in an exposed but noninfected population from a P. vivax endemic area. Interestingly, over 40% of this population had antibodies recognizing both variants. These results have implications for the design of a vaccine based on a polymorphic antigen.


Assuntos
Antígenos de Protozoários/genética , Malária Vivax/imunologia , Malária Vivax/parasitologia , Proteínas de Membrana/genética , Plasmodium vivax/genética , Proteínas de Protozoários/genética , Dicroísmo Circular , DNA de Protozoário/genética , Epitopos de Linfócito B , Haplótipos , Humanos , Malária Vivax/epidemiologia , Mutação , Plasmodium vivax/imunologia , Conformação Proteica , Proteínas Recombinantes
8.
Artigo em Inglês | MEDLINE | ID: mdl-32515655

RESUMO

To understand the effect of 17α-ethinylestradiol (EE2) on the conformation changes of bovine serum albumin (BSA), the binding mechanisms of EE2 with BSA were investigated by fluorescence spectroscopy, time-resolved fluorescence spectroscopy, synchronous fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, UV-visible spectroscopy, circular dichroism (CD) spectroscopy and molecular docking. The quenching constants, binding constants, the number of binding sites, thermodynamic parameters, binding distance and the secondary structure changes of BSA were determined. The results of fluorescence quenching experiment suggested that the fluorescence quenching of BSA by EE was due to the formation of complex through static quenching, which was also confirmed by time-resolved fluorescence measurements. The thermodynamic parameters indicated that the binding of EE2 to BSA was driven mainly by van der Waals forces and hydrogen bonding. The conformation alterations of BSA upon EE2 binding were studied by UV-vis spectroscopy and CD spectroscopy. The results of site marker competitive experiments and molecular docking showed that the binding sites of EE2 were mainly located within site I in the subdomain IIA of BSA.


Assuntos
Dicroísmo Circular/métodos , Poluentes Ambientais/química , Etinilestradiol/química , Soroalbumina Bovina/química , Espectrometria de Fluorescência/métodos , Espectrofotometria Ultravioleta/métodos , Animais , Sítios de Ligação , Bovinos , Simulação de Acoplamento Molecular , Ligação Proteica , Conformação Proteica , Termodinâmica
9.
Science ; 368(6498): 1426-1427, 2020 06 26.
Artigo em Inglês | MEDLINE | ID: mdl-32587006
10.
Science ; 368(6498): 1465-1468, 2020 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-32587016

RESUMO

DNA and proteins are chiral: Their three-dimensional structures cannot be superimposed with their mirror images. Circular dichroism spectroscopy is widely used to characterize chiral compounds, but data interpretation is difficult in the case of mixtures. We recorded the electronic circular dichroism spectra of DNA helices separated in a mass spectrometer. We studied guanine-rich strands having various secondary structures, electrosprayed them as negative ions, irradiated them with an ultraviolet nanosecond optical parametric oscillator laser, and measured the difference in electron photodetachment efficiency between left and right circularly polarized light. The reconstructed circular dichroism ion spectra resembled those of their solution-phase counterparts, thereby allowing us to assign the DNA helical topology. The ability to measure circular dichroism directly on biomolecular ions expands the capabilities of mass spectrometry for structural analysis.


Assuntos
Dicroísmo Circular/métodos , DNA/química , Guanina/química , Espectrometria de Massas/métodos , Guanina/análise , Conformação de Ácido Nucleico
11.
Nat Commun ; 11(1): 3137, 2020 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-32561731

RESUMO

The close synergy between peptides and nucleic acids in current biology is suggestive of a functional co-evolution between the two polymers. Here we show that cationic proto-peptides (depsipeptides and polyesters), either produced as mixtures from plausibly prebiotic dry-down reactions or synthetically prepared in pure form, can engage in direct interactions with RNA resulting in mutual stabilization. Cationic proto-peptides significantly increase the thermal stability of folded RNA structures. In turn, RNA increases the lifetime of a depsipeptide by >30-fold. Proto-peptides containing the proteinaceous amino acids Lys, Arg, or His adjacent to backbone ester bonds generally promote RNA duplex thermal stability to a greater magnitude than do analogous sequences containing non-proteinaceous residues. Our findings support a model in which tightly-intertwined biological dependencies of RNA and protein reflect a long co-evolutionary history that began with rudimentary, mutually-stabilizing interactions at early stages of polypeptide and nucleic acid co-existence.


Assuntos
Evolução Molecular , Peptídeos/metabolismo , Dobramento de Proteína , Estabilidade de RNA , RNA/metabolismo , Sequência de Aminoácidos , Aminobutiratos/química , Aminobutiratos/metabolismo , Cátions/química , Cátions/metabolismo , Dicroísmo Circular , Hidrólise , Ressonância Magnética Nuclear Biomolecular , Origem da Vida , Ornitina/química , Ornitina/metabolismo , Peptídeos/química , Estabilidade Proteica , RNA/química , beta-Alanina/análogos & derivados , beta-Alanina/química , beta-Alanina/metabolismo
12.
Food Chem ; 329: 127183, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32521427

RESUMO

Combined effects of pH and thermal treatments on black kidney bean lectin (BKBL) were investigated by response surface methodology (RSM). Low-pH (1.0, 2.0, 3.0) incubation decreased hemagglutination activity (HA) and IgE-binding capacity, but the activities would be restored when the lectin was treated by pH shifting to 7.2. Conformational structure analyses indicated that low-pH induced protein unfolding and pH-shifting treatment resulted in a limited structural rearrangement. Mild heating, such as 60 °C for 3 min, slightly increased the HA and IgE-binding activities of pH shifted BKBL, but no obvious effects in the pH 1.0 incubated BKBL. High-temperature and long-time treatment might induce the protein aggregation, further decreased HA and IgE-binding capacities. RSM results showed both IgE-binding capacity and HA were the lowest under the combination of pH 1.0 incubation with 80 °C heating for 15 min or pH shifting from 1.0 to 7.2 with 100 °C heating for 10 min.


Assuntos
Imunoglobulina E/metabolismo , Lectinas/química , Phaseolus/metabolismo , Dicroísmo Circular , Temperatura Alta , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Lectinas/metabolismo , Agregados Proteicos , Conformação Proteica em alfa-Hélice , Estrutura Terciária de Proteína , Espectrometria de Fluorescência
13.
Food Chem ; 330: 127151, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32521395

RESUMO

The research developed a diazo-coupling carbon-dots (CDs) method for determining nitrite and optimized variables of sodium sulfanilate, CDs synthesis, characteristic wavelength, reaction time and temperature. The method can assay 0.025-2.0 mg/L NO2- and has a detection limit of 9.6 µg/L and 95-105% recovery. Subsequently, it was applied in detecting NO2- changes in some Chinese home cooking, the gotten results indicated that if the sautéed vegetables (cabbage, Chinese cabbage, spinach and lettuce) and stir-fry pork, fried peas and pickled vegetable are stored at 4 °C for 72 h, nitrite contents are far lower than the recommended value, but if stored at room temperature for 24 h, the content in pure vegetables and shredded pork with green pepper will exceed the recommended value. Therefore, the staying fresher for the sautéed vegetables at room temperature is 24 h, if stored in a refrigerator at 4 °C, their staying fresher can be extended to 72 h.


Assuntos
Culinária , Nitritos/análise , Verduras/química , Carbono/análise , Dicroísmo Circular , Temperatura Alta
14.
Food Chem ; 331: 127340, 2020 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-32569971

RESUMO

Acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were extracted and purified from the cartilages of skate and sturgeon. Their typical structure and physicochemical properties were evaluated by circular dichroism (CD), X-ray diffraction (XRD), and so on. Results showed that the extracted collagen was likely identified as collagen-II composed of three α-chains (135 kDa), with the typical peptide sequence of Gly-X-Y. It showed the collagen retained the native and intact triple helical structure, and its intensity ratio of the positive and negative absorption peaks (Rpn) was 0.19-0.25. In addition, the extracted collagen exhibited obvious self-assembly behavior with the concentration above 0.3 mg/mL, the adjustment of pH 7.4-7.6 and the NaCl concentration of 120 mmol/L. The critical aggregate mass concentrations of pepsin-soluble collagens from skate and sturgeon were 0.93 and 0.86 g/L, respectively. Therefore, collagens from skate and sturgeon cartilages have potential commercial application.


Assuntos
Cartilagem/química , Colágeno Tipo II/química , Proteínas de Peixes/química , Peixes , Aminoácidos/análise , Animais , Dicroísmo Circular , Colágeno Tipo II/análise , Produtos Pesqueiros , Proteínas de Peixes/análise , Concentração de Íons de Hidrogênio , Monossacarídeos/análise , Concentração Osmolar , Pepsina A/química , Conformação Proteica , Rajidae , Cloreto de Sódio/química , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
15.
Food Chem ; 331: 127374, 2020 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-32593796

RESUMO

Effects of a novel slit divergent ultrasound (SDU) treatment on soybean protein isolate (SPI)-lentinan conjugates via Maillard reaction was investigated. Besides, the stability of emulsions prepared by SPI and SPI-lentinan conjugates (ultrasound and un-ultrasound) as emulsifiers was compared. The results showed that ultrasonic treatment (40 min) markedly increased the degree of grafting (26.48%) by 1.91 times comparing with traditional heating method (2 h, 13.89%). In addition, structural analysis showed that the conjugates obtained by SDU treatment changed the secondary structure and had higher surface hydrophobicity and fluorescence intensity than those obtained by traditional heating method. Apart from this, SDU treatment could significantly improve the functional properties (solubility, foaming, emulsifying capacity, thermal stability, and viscosity) of conjugates. Furthermore, the emulsions prepared by the SPI-lentinan conjugates (ultrasound) as emulsifiers possessed the highest stability against environmental stresses. Taken together, SDU-assisted heating could be an excellent method to improve the functional properties of conjugates.


Assuntos
Emulsões/química , Lentinano/química , Reação de Maillard , Proteínas de Soja/química , Dicroísmo Circular , Emulsificantes/química , Fluorescência , Indústria de Processamento de Alimentos/métodos , Glicosilação , Calefação , Interações Hidrofóbicas e Hidrofílicas , Estabilidade Proteica , Estrutura Secundária de Proteína , Solubilidade , Proteínas de Soja/isolamento & purificação , Ultrassom , Viscosidade , Água/química
16.
Food Chem ; 328: 127152, 2020 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-32474234

RESUMO

Potato trypsin inhibitor (PTI) was obtained from imitated potato wastewater through a sustainable method of sequential acid precipitation, salting out, and ultrafiltration. PTI had a favorable inhibition with the low IC50 of 6.861 ± 0.107 mg/L. To explore stability of PTI against pH and heating treatment, PTI secondary structure was investigated by circular dichroism and inhibition was determined using the BAPNA method. The results indicated that PTI exerted a certain heat resistance and excellent stability over a wide pH range. Also, correlation analysis displayed ß-sheet and ß-turn contents of PTI had a positive correlation with inhibition, whereas α-helix and random coil contents were negatively correlated with inhibition. During in vitro digestion, the limited loss rate of activity (29.28%) and degree of hydrolysis (24.39%) suggested that PTI presented sufficient resistance to gastrointestinal digestion. These findings would extend beneficial hints to convert potato wastewater by-product into the potential anti-obesity ingredient in future.


Assuntos
Sucos de Frutas e Vegetais , Solanum tuberosum/química , Inibidores da Tripsina/química , Inibidores da Tripsina/isolamento & purificação , Dicroísmo Circular , Digestão , Calefação , Concentração de Íons de Hidrogênio , Hidrólise , Dobramento de Proteína , Estrutura Secundária de Proteína , Inibidores da Tripsina/farmacologia
17.
Food Chem ; 328: 127144, 2020 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-32474242

RESUMO

The combined effects of ultrasound (intensity of 15.6 W/cm2 and sonication for 5 min) with potassium alginate (PA) marination (UPA) on tenderizing old chicken breast meat, and possible mechanisms from tissue to protein, were investigated. UPA-treated meat exhibited the lowest moisture loss and shear force (optimized tenderness). The increased fiber space benefited PA invasion to form a heat-induced barrier for harder muscle contraction and avoid moisture withdrawal. Special scale-like structures of dried myofibrillar protein (MP) and the three-dimensional network induced by interactions between PA and MP increased the tenderness. UPA treatment induced stronger electrostatic repulsion between PA molecules and more ß-sheet structures of MP, accompanied by a smallest size. The more easily heat-denatured myosin and looser myofibrils accelerated the temperature rise. More immobilized water restricted to myofibrils and moisture captured in the gel network promoted water retention. UPA treatment could be a promising technology to tenderize old chicken breast meat.


Assuntos
Alginatos/química , Galinhas , Produtos Avícolas , Animais , Dicroísmo Circular , Culinária , Fibras na Dieta/análise , Indústria de Processamento de Alimentos/métodos , Miofibrilas/química , Miofibrilas/ultraestrutura , Miosinas/química , Proteínas de Aves Domésticas/química , Ultrassom , Água/análise
18.
Food Chem ; 329: 126775, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32512387

RESUMO

Fish products are a promising source of collagen; however, these extracts are biochemically unstable. Acid-soluble collagen (ASC) was isolated from the skin of eleven fish species at various physiological temperatures (Tp). Structural features of these samples were analysed in detail using Circular Dichroism (CD) and compared to their biochemical characteristics. Positive correlation (r = 0.74, p < 0.01) between the Tp and ratio of positive peak intensity to negative peak intensity (Rpn) in CD analysis suggested a higher thermal stability of ASC from warm-water fish, owing to a higher content of cyclic imino acids, such as proline and hydroxyproline (Hyp). Conversely, cold-water fish ASCs contain significantly higher levels of acyclic, hydroxyl groups carrying Ser. These results indicated that CD spectrum techniques including Rpn measurement are concise and helpful for direct detection of the triple helix structure of fish collagens, and that this structure is tightly linked to thermostability of this molecule.


Assuntos
Colágeno Tipo I/química , Hidroxiprolina/química , Prolina/química , Serina/química , Animais , Dicroísmo Circular , Peixes , Desnaturação Proteica , Temperatura
19.
Phytochemistry ; 176: 112417, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32473392

RESUMO

Eight undescribed neolignans and an undescribed propanoid dimer were isolated from the leaves of Miliusa sessilis, together with two known compounds, dehydrodieugenol A and dehydrodieugenol B. All structures were elucidated by extensive spectroscopic data analysis and the structure of (7S,8R)-5'-hydroxy-3,4-dimethoxy-4',7-epoxy-8,3'-neolign-8'-en-9-acetate (miliusin A) was further confirmed by X-ray crystallographic analysis. The absolute configurations were determined using circular dichroism (CD) data analysis and the modified Mosher's method. All isolated compounds were evaluated for their cytotoxic activities against four human cancer cell lines (HeLa, HN22, HepG2, and HCT116), including one normal-type cell line (HaCaT) using MTT assay. (7S,8R)-5'-hydroxy-3,4-dimethoxy-4',7-epoxy-8,3'-neolign-8'-en-9-ol (miliusin B) was found to exhibit the most promising cytotoxic effect against Hela cells with the lowest IC50 value of 0.04 µM and the highest selective index of 187.8, highlighting miliusin B as an attractive candidate for cervical cancer drug development.


Assuntos
Annonaceae , Lignanas , Dicroísmo Circular , Células HeLa , Humanos , Estrutura Molecular , Folhas de Planta
20.
Nat Commun ; 11(1): 2319, 2020 05 08.
Artigo em Inglês | MEDLINE | ID: mdl-32385234

RESUMO

Bruton's tyrosine kinase (Btk) is critical for B-cell maturation and activation. Btk loss-of-function mutations cause human X-linked agammaglobulinemia (XLA). In contrast, Btk signaling sustains growth of several B-cell neoplasms which may be treated with tyrosine kinase inhibitors (TKIs). Here, we uncovered the structural mechanism by which certain XLA mutations in the SH2 domain strongly perturb Btk activation. Using a combination of molecular dynamics (MD) simulations and small-angle X-ray scattering (SAXS), we discovered an allosteric interface between the SH2 and kinase domain required for Btk activation and to which multiple XLA mutations map. As allosteric interactions provide unique targeting opportunities, we developed an engineered repebody protein binding to the SH2 domain and able to disrupt the SH2-kinase interaction. The repebody prevents activation of wild-type and TKI-resistant Btk, inhibiting Btk-dependent signaling and proliferation of malignant B-cells. Therefore, the SH2-kinase interface is critical for Btk activation and a targetable site for allosteric inhibition.


Assuntos
Tirosina Quinase da Agamaglobulinemia/metabolismo , Cristalografia por Raios X/métodos , Linfoma/metabolismo , Tirosina Quinase da Agamaglobulinemia/genética , Western Blotting , Sobrevivência Celular/genética , Sobrevivência Celular/fisiologia , Dicroísmo Circular , Citometria de Fluxo , Células HEK293 , Humanos , Immunoblotting , Imunoprecipitação , Linfoma/genética , Simulação de Dinâmica Molecular , Mutagênese Sítio-Dirigida , Mutação/genética
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