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1.
Nat Commun ; 11(1): 5068, 2020 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033251

RESUMO

The mineralized collagen fibril is the basic building block of bone, and is commonly pictured as a parallel array of ultrathin carbonated hydroxyapatite (HAp) platelets distributed throughout the collagen. This orientation is often attributed to an epitaxial relationship between the HAp and collagen molecules inside 2D voids within the fibril. Although recent studies have questioned this model, the structural relationship between the collagen matrix and HAp, and the mechanisms by which collagen directs mineralization remain unclear. Here, we use XRD to reveal that the voids in the collagen are in fact cylindrical pores with diameters of ~2 nm, while electron microscopy shows that the HAp crystals in bone are only uniaxially oriented with respect to the collagen. From in vitro mineralization studies with HAp, CaCO3 and γ-FeOOH we conclude that confinement within these pores, together with the anisotropic growth of HAp, dictates the orientation of HAp crystals within the collagen fibril.


Assuntos
Colágeno/química , Minerais/química , Orientação Espacial , Osso e Ossos/química , Criança , Colágeno/ultraestrutura , Cristalização , Durapatita/química , Elétrons , Feminino , Humanos , Modelos Moleculares , Tomografia , Difração de Raios X
2.
Yakugaku Zasshi ; 140(9): 1165-1173, 2020.
Artigo em Japonês | MEDLINE | ID: mdl-32879248

RESUMO

Relationship between water molecules and parent and hydroxypropylated cyclodextrins (denoted as CD and HP-CD) was assessed in this paper. The trends in ad-desorption isotherms of CD for water molecule were quite different compared to those of HP-CD. Ad-desorption isotherms of CD showed the hysteresis under our experimental conditions. The molar ratio of hydration (R-value) using α-CD, ß-CD, γ-CD, HP-α-CD, HP-ß-CD, and HP-γ-CD was 7.1, 11.4, 13.5, 12.5, 14.0, and 16.7, respectively. These results indicated that the adsorption capability of water molecule of HP-CD was greater than that of CD. Additionally, the changes in characteristics of CD and HP-CD at different water activity conditions were demonstrated. X-ray diffraction patterns were significantly different between CD and HP-CD. The crystal structure of HP-α-CD, HP-ß-CD, and HP-γ-CD showed amorphous at different water activity conditions. Finally, sorption entropy and heat of sorption of water molecules were calculated in this experiment. In summary, these results provide useful information for understanding the relationship between water molecules and parent and hydroxypropylated cyclodextrins.


Assuntos
Glicosídeo Hidrolases/química , Água/química , 2-Hidroxipropil-beta-Ciclodextrina/química , Adsorção , Cristalização , Relação Estrutura-Atividade
3.
Am J Chin Med ; 48(6): 1455-1473, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32933312

RESUMO

Uric acid nephropathy (UAN) is caused by excessive uric acid, which results in the damage of renal tissue via urate crystals deposition in the kidneys. The roots and rhizomes of Salvia miltiorrhiza Bunge (S. miltiorrhiza) have been clinically used in many prescriptions to treat uric acid-induced renal damage. This study investigates the uricosuric and nephroprotective effects of the ethyl acetate extract of S. miltiorrhiza (EASM) and tanshinone IIA (a major component of S. miltiorrhiza, Tan-IIA) on UAN and explores the underlying molecular mechanism. Both EASM and Tan-IIA significantly decreased serum uric acid (SUA), serum creatinine (SCR), urine uric acid (UUA), and increased urine creatinine (UCR), and blood urea nitrogen (BUN) levels in experimental UAN mice. In adenine and potassium oxonate-induced mice, EASM and Tan-IIA treatment alleviated renal dysfunction and downregulated the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). Moreover, EASM treatment significantly prevented excessive reactive oxygen species (ROS) production in uric acid-induced HK-2 cells and suppressed the expression of nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4). EASM also suppressed ROS-activated mitogen-activated protein kinases (MAPKs) in vivo and in vitro. These results suggest that both EASM and Tan-IIA demonstrated inhibitory effects on UAN through relieving NOX4-mediated oxidative stress and suppressing MAPK pathways activation.


Assuntos
Abietanos/farmacologia , Abietanos/uso terapêutico , Cálculos Renais/tratamento farmacológico , Cálculos Renais/metabolismo , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Fitoterapia , Extratos Vegetais/farmacologia , Extratos Vegetais/uso terapêutico , Salvia miltiorrhiza/química , Ácido Úrico/metabolismo , Abietanos/isolamento & purificação , Animais , Células Cultivadas , Cristalização , Modelos Animais de Doenças , Humanos , Interações Hidrofóbicas e Hidrofílicas , Cálculos Renais/etiologia , Camundongos , Camundongos Endogâmicos , Extratos Vegetais/isolamento & purificação
4.
Proc Natl Acad Sci U S A ; 117(33): 19720-19730, 2020 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-32732435

RESUMO

The synthesis of quinolinic acid from tryptophan is a critical step in the de novo biosynthesis of nicotinamide adenine dinucleotide (NAD+) in mammals. Herein, the nonheme iron-based 3-hydroxyanthranilate-3,4-dioxygenase responsible for quinolinic acid production was studied by performing time-resolved in crystallo reactions monitored by UV-vis microspectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and X-ray crystallography. Seven catalytic intermediates were kinetically and structurally resolved in the crystalline state, and each accompanies protein conformational changes at the active site. Among them, a monooxygenated, seven-membered lactone intermediate as a monodentate ligand of the iron center at 1.59-Å resolution was captured, which presumably corresponds to a substrate-based radical species observed by EPR using a slurry of small-sized single crystals. Other structural snapshots determined at around 2.0-Å resolution include monodentate and subsequently bidentate coordinated substrate, superoxo, alkylperoxo, and two metal-bound enol tautomers of the unstable dioxygenase product. These results reveal a detailed stepwise O-atom transfer dioxygenase mechanism along with potential isomerization activity that fine-tunes product profiling and affects the production of quinolinic acid at a junction of the metabolic pathway.


Assuntos
3-Hidroxiantranilato 3,4-Dioxigenase/química , Proteínas de Bactérias/química , Cupriavidus/enzimologia , 3-Hidroxiantranilato 3,4-Dioxigenase/genética , 3-Hidroxiantranilato 3,4-Dioxigenase/metabolismo , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Domínio Catalítico , Cristalização , Cristalografia por Raios X , Cupriavidus/química , Cupriavidus/genética , Cinética , Lactonas/química , Lactonas/metabolismo , Modelos Moleculares , Especificidade por Substrato
5.
J Chromatogr A ; 1626: 461354, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797834

RESUMO

The Al-doped mesoporous crystalline material-41 (Al-MCM-41) composite was prepared and applied as fiber coating material of headspace solid-phase microextraction (HS-SPME) for extraction of polycyclic aromatic hydrocarbons (PAHs) from human urine. Five PAHs including acenaphthene, fluorene, phenanthrene, anthracene, and pyrene are chosen as target analytes to evaluate the performance of the material by GC-FID analysis. The mesoporous Al-MCM-41 composite was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption/desorption measurement, and thermogravimetric analysis. The parameters affecting the extraction efficiency of HS-SPME were investigated. Under the optimal conditions, the method exhibits ideal linearity for target analytes in the range of 0.3-600 ng⋅mL-1 with the coefficients (R2) equal or higher than 0.9906. The enrichment factors are calculated from 540 to 1760. The limits of detection (LODs) and limits of quantitation (LOQs) are between the ranges of 0.06-0.18 and 0.3-0.9 ng⋅mL-1, respectively. The relative standard deviations (RSDs) (n = 5) of intra-day and inter-day are in the ranges of 1.08-7.49% and 2.84-18.3% respectively. The fiber-to-fiber reproducibility (n = 3) is in the range of 6.47-13.9%. The method was successfully applied for the analysis of PAHs in human urine with reasonable recoveries which is ranging from 73.29 to 116.1%.


Assuntos
Alumínio/química , Hidrocarbonetos Policíclicos Aromáticos/urina , Dióxido de Silício/química , Microextração em Fase Sólida/métodos , Adsorção , Cristalização , Humanos , Limite de Detecção , Masculino , Concentração Osmolar , Porosidade , Padrões de Referência , Reprodutibilidade dos Testes , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Fatores de Tempo , Difração de Raios X
6.
Environ Pollut ; 266(Pt 2): 115361, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32810833

RESUMO

Struvite (MgNH4PO3·6H2O) crystallization is one of important methods of phosphorus recovery from wastewater. As to livestock wastewater, the high-strength occurrence of antibiotics and antibiotic resistance genes might induce struvite recovery to spread antibiotic resistance to the environment. However, limited information has been reported on the simultaneous transport of antibiotics and ARGs in struvite recovery. In the present study, tetracyclines (TCs) and tetracyclines antibiotic resistance genes (ARGs) were selected as the targeted pollutants, and their discrepant residues in struvite recovery from swine wastewater were investigated. TCs and ARGs were obviously detected, with their contents of 4.88-79.5 mg/kg and 6.99 × 107-2.14 × 1011 copies/g, notably higher than those of TCs 0.550-1.94 mg/kg and ARGs 3.98 × 104-5.66 × 107 copies/g obtained from synthetic wastewater. The correlational relationship revealed that predominant factors affecting TCs and ARGs transports were different. Results from network analyses indicated that among the total edges, the negative correlations between TCs and ARGs predominately occupied 18.0%. The redundancy analysis revealed that mineral components in the recovered products, including struvite, K-struvite and amorphous calcium phosphate, coupling with organic contents, displayed insignificant roles on TCs residues, where heavy metals exerted positive and remarkable functions to boost TCs migration. Unexpectedly, mineral components and heavy metals did not displayed significant promotion on ARGs transport as a whole.


Assuntos
Fósforo , Águas Residuárias/análise , Animais , Antibacterianos/farmacologia , Cristalização , Resistência Microbiana a Medicamentos/efeitos dos fármacos , Genes Bacterianos/efeitos dos fármacos , Estruvita , Suínos
7.
Water Sci Technol ; 81(12): 2511-2521, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32857739

RESUMO

The struvite crystallization process can recover struvite crystals as a valuable slow-release fertilizer from the side stream of wastewater treatment plants (WWTPs). The purpose of this study is to demonstrate the crystal growth characteristics and determine the appropriate recovery criteria for a struvite crystallization pilot plant. A pilot plant (8.6 m3/d) was designed with a feeding system of MgO (magnesium oxide), a pH controller, and a hydrocyclone for recovering struvite; the plant was operated for 42 hours at a pH range of 8.25-8.5. The removal efficiencies for PO4-P and NH4-N were 82.5-90.7% and 13.4-22.9%, respectively. The struvite recovered from the hydrocyclone was sifted using standard sieves and analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The dry weight fraction of the precipitate in the 300-600 µm range increased gradually from 7% to 74% in 18 hours. The XRD analysis revealed that the crystalline structure of the precipitate in the 150-600 µm range indicates struvite without any peaks of MgO, Mg(OH)2, and MgCO3. This indicates that the critical conditions for recovering struvite from the side-stream of WWTPs are an operation period of 18 hours and a crystal size greater than 300 µm.


Assuntos
Compostos de Magnésio , Óxido de Magnésio , Cristalização , Fosfatos , Fósforo , Estruvita
8.
Water Sci Technol ; 81(11): 2300-2310, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32784275

RESUMO

Phosphorus crystallization-filtration (PCF) was devised as a novel tertiary process for phosphorus removal from domestic wastewater. The results obtained showed that during the PCF process, high pH and excessive calcium dosage conditions were required to obtain effluents with total phosphorus (T-P) and suspended solid (SS) concentrations below 0.2 and 10 mg/L, respectively, within 2 h of operation. Phosphorus was precipitated during the pre-treatment step, and thereafter it crystallized on the surface of the fixed seed material in the PCF reactor. Furthermore, the addition of Ca2+ resulted in phosphorus removal efficiencies >95%, and pH, residual Ca2+, filtration depth, and linear velocity were identified as the main design and operation parameters of the PCF process. Following the pilot-scale PCF process, the average concentrations of T-P, PO4-P, and SS in the effluent were 0.05, 0.04, and 1.1 mg/L, respectively, corresponding to removal efficiencies of 90.9, 86.5, and 79.7%, respectively. The investigation of the backwashing sludge characteristics of the PCF process using scanning electron microscopy (SEM), Fourier transform-infrared vacuum spectrometry (FT-IR), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses showed that owing to its high contents in calcite and hydrated phosphorus compounds, PCF sludge could be used as an alternative soil amendment resource.


Assuntos
Fósforo , Águas Residuárias , Cristalização , Durapatita , Esgotos , Espectroscopia de Infravermelho com Transformada de Fourier , Eliminação de Resíduos Líquidos
9.
Sci Rep ; 10(1): 13875, 2020 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-32807805

RESUMO

Respiratory protection is key in infection prevention of airborne diseases, as highlighted by the COVID-19 pandemic for instance. Conventional technologies have several drawbacks (i.e., cross-infection risk, filtration efficiency improvements limited by difficulty in breathing, and no safe reusability), which have yet to be addressed in a single device. Here, we report the development of a filter overcoming the major technical challenges of respiratory protective devices. Large-pore membranes, offering high breathability but low bacteria capture, were functionalized to have a uniform salt layer on the fibers. The salt-functionalized membranes achieved high filtration efficiency as opposed to the bare membrane, with differences of up to 48%, while maintaining high breathability (> 60% increase compared to commercial surgical masks even for the thickest salt filters tested). The salt-functionalized filters quickly killed Gram-positive and Gram-negative bacteria aerosols in vitro, with CFU reductions observed as early as within 5 min, and in vivo by causing structural damage due to salt recrystallization. The salt coatings retained the pathogen inactivation capability at harsh environmental conditions (37 °C and a relative humidity of 70%, 80% and 90%). Combination of these properties in one filter will lead to the production of an effective device, comprehensibly mitigating infection transmission globally.


Assuntos
Filtros de Ar/microbiologia , Antibacterianos/química , Betacoronavirus , Infecções por Coronavirus/prevenção & controle , Máscaras/microbiologia , Membranas Artificiais , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Dispositivos de Proteção Respiratória/microbiologia , Cloreto de Sódio/química , Aerossóis , Antibacterianos/farmacologia , Infecções por Coronavirus/transmissão , Infecções por Coronavirus/virologia , Cristalização , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Temperatura Alta , Humanos , Umidade , Pneumonia Viral/transmissão , Pneumonia Viral/virologia , Cloreto de Sódio/farmacologia
10.
J Cancer Res Ther ; 16(3): 440-444, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32719248

RESUMO

Introduction: Crystallization test is based on the principle that, when a salt crystallizes out of an aqueous solution, the crystal growth is influenced by the presence of other substances in the solution, such as blood or plant extracts. If a mixture of copper chloride solution with a small amount of whole blood is allowed to crystallize under controlled experimental conditions, an aggregate of crystals forms. Crystallization method can be used as a diagnostic aid to provide information about the systemic conditions and general health of the patient. Aim: This study aims to study the patterns of crystallization and to further determine the efficacy of crystallization test as a screening modality in premalignant lesions and oral squamous cell carcinoma (OSCC). Materials and Methods: Fifty patients of OSCC, 50 patients of premalignant lesions, and 50 healthy individuals were selected. One drop of blood was collected from the study groups to perform crystallization using cupric chloride. Statistical Analysis Used: Statistical analysis was performed using Chi-square test, Student's t-test (two-tailed), and analysis of variance. Results: The different patterns of crystals formed were studied and statistically analyzed. Conclusion: Based on the study, it was concluded that Crystallization test can be used as an effective screening modality for detection of premalignant lesions and OSCC.


Assuntos
Biomarcadores Tumorais/análise , Carcinoma de Células Escamosas/diagnóstico , Cobre/química , Cristalização/métodos , Leucoplasia/sangue , Neoplasias Bucais/diagnóstico , Lesões Pré-Cancerosas/diagnóstico , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Carcinoma de Células Escamosas/sangue , Carcinoma de Células Escamosas/química , Estudos de Casos e Controles , Feminino , Humanos , Leucoplasia/patologia , Masculino , Programas de Rastreamento , Pessoa de Meia-Idade , Neoplasias Bucais/sangue , Neoplasias Bucais/química , Estadiamento de Neoplasias , Lesões Pré-Cancerosas/sangue , Adulto Jovem
11.
Nature ; 583(7814): 66-71, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32612224

RESUMO

Dental enamel is a principal component of teeth1, and has evolved to bear large chewing forces, resist mechanical fatigue and withstand wear over decades2. Functional impairment and loss of dental enamel, caused by developmental defects or tooth decay (caries), affect health and quality of life, with associated costs to society3. Although the past decade has seen progress in our understanding of enamel formation (amelogenesis) and the functional properties of mature enamel, attempts to repair lesions in this material or to synthesize it in vitro have had limited success4-6. This is partly due to the highly hierarchical structure of enamel and additional complexities arising from chemical gradients7-9. Here we show, using atomic-scale quantitative imaging and correlative spectroscopies, that the nanoscale crystallites of hydroxylapatite (Ca5(PO4)3(OH)), which are the fundamental building blocks of enamel, comprise two nanometric layers enriched in magnesium flanking a core rich in sodium, fluoride and carbonate ions; this sandwich core is surrounded by a shell with lower concentration of substitutional defects. A mechanical model based on density functional theory calculations and X-ray diffraction data predicts that residual stresses arise because of the chemical gradients, in agreement with preferential dissolution of the crystallite core in acidic media. Furthermore, stresses may affect the mechanical resilience of enamel. The two additional layers of hierarchy suggest a possible new model for biological control over crystal growth during amelogenesis, and hint at implications for the preservation of biomarkers during tooth development.


Assuntos
Amelogênese , Esmalte Dentário/química , Ácidos/química , Cálcio/química , Carbonatos/química , Cristalização , Teoria da Densidade Funcional , Esmalte Dentário/ultraestrutura , Durapatita/química , Fluoretos/química , Humanos , Magnésio/química , Microscopia Eletrônica de Transmissão e Varredura , Sódio/química , Tomografia , Difração de Raios X
12.
Food Chem ; 333: 127538, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32712546

RESUMO

The effects of water content; 15, 30, and 40% (w/w), water droplet size; d43 15.0-19.6 µm (larger) and d43 1.2-2.7 µm (smaller), and sodium alginate (0.5%, w/w) induced water gelation on crystallization kinetics and water and fat proton relaxation were studied in water-in-milk fat emulsions during in situ cooling from 40 °C to 5 °C. Anhydrous milk fat (AMF) and commercial butter were employed as two separate fat sources. Although emulsions were crystallized faster than the bulk fat, the variations in the water fraction and droplet size did not show major influence on crystallization properties. Smaller droplet size induced significant (p < 0.05) reduction in water mobility with a minimal effect of the temperature. In AMF-based emulsions, gelation of water phase not only immobilized the water molecules but also enhanced the rate of fat crystallization. Globular fat and serum solids in butter-based emulsions showed to fasten the water proton relaxation.


Assuntos
Ácidos Graxos/química , Leite/química , Movimento (Física) , Transição de Fase , Água/química , Animais , Manteiga/análise , Cristalização , Emulsões , Géis , Cinética , Temperatura
13.
Yakugaku Zasshi ; 140(7): 913-921, 2020.
Artigo em Japonês | MEDLINE | ID: mdl-32612056

RESUMO

Controlling the physicochemical properties of a drug formulation is important for proper drug efficacy, since in the gastrointestinal tract many drugs undergo dissolution, limiting their efficacy. Factors affecting a drug's physicochemical properties include its crystal habit. Therefore, we predicted the crystal habit by molecular simulation for the purpose of controlling crystal morphology. In this study, we used aspirin as a model compound. By performing simulations based on known crystal structure data, we trained the simulation algorithm to produce the cubic and plate-like morphologies of crystals actually obtained. By these methods, we showed that the crystal plane of the crystal form actually obtained coincides with the characteristic crystal plane obtained by simulation. Furthermore, to consider the influence of the crystallization solvent on crystal growth, we simulated adsorption of solvent molecules on characteristic crystal planes. The difference in adsorption energy of the solvent molecules prevents the aspirin molecules from attaching to the crystal plane. As a result, we concluded that the crystal habit was caused by the difference in growth rate of the crystal plane. By applying the methods developed in this research, the growth of crystal planes can be predicted by molecular simulation, making it possible to efficiently obtain crystal forms with optimal physical properties for drug development. We believe that further development of this approach will lead to dramatic decreases in the cost and duration of drug development.


Assuntos
Aspirina/química , Adsorção , Fenômenos Químicos , Cristalização , Composição de Medicamentos , Previsões , Modelos Moleculares , Solventes/química
14.
Food Chem ; 333: 127514, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32683259

RESUMO

This study investigated the effect of pH on the denaturation extent, the surface chemical composition, the water sorption isotherm and the glass transition temperature of camel and bovine whey protein's powders. The LC-MS analysis indicated that the ß-Lactoglobulin was the most denatured protein in bovine whey powders regardless the pH value, while this protein was totally absent in camel whey. The α-Lactalbumin was relatively heat stable after drying and predominated the powder surface (X-ray photoelectron spectroscopy results) in both camel and bovine whey powders regardless the pH (neutral (6.7) or acidic (4.3 and 4.6)). Analysis of the water sorption isotherms indicated that decreasing the pH induced the increase of the water activity of lactose crystallization for camel and bovine whey powders. Finally, decreasing the pH led to the decrease of the glass transition temperature of camel and bovine whey powder (at 0.13, 0.23, and 0.33 of water activity).


Assuntos
Pós/química , Proteínas do Soro do Leite/química , Adsorção , Animais , Calorimetria , Camelus , Bovinos , Cromatografia Líquida de Alta Pressão , Cristalização , Concentração de Íons de Hidrogênio , Lactoglobulinas/química , Lactoglobulinas/metabolismo , Lactose/química , Espectrometria de Massas , Desnaturação Proteica , Propriedades de Superfície , Temperatura de Transição , Água/química , Proteínas do Soro do Leite/metabolismo
15.
J Vis Exp ; (159)2020 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-32478746

RESUMO

The M42 aminopeptidases form functionally active complexes made of 12 subunits. Their assembly process appears to be regulated by their metal ion cofactors triggering a dimer-dodecamer transition. Upon metal ion binding, several structural modifications occur in the active site and at the interaction interface, shaping dimers to promote the self-assembly. To observe such modifications, stable oligomers must be isolated prior to structural study. Reported here is a method that allows the purification of stable dodecamers and dimers of TmPep1050, an M42 aminopeptidase of T. maritima, and their structure determination by X-ray crystallography. Dimers were prepared from dodecamers by removing metal ions with a chelating agent. Without their cofactor, dodecamers became less stable and were fully dissociated upon heating. The oligomeric structures were solved by the straightforward molecular replacement approach. To illustrate the methodology, the structure of a TmPep1050 variant, totally impaired in metal ion binding, is presented showing no further breakdown of dimers to monomers.


Assuntos
Aminopeptidases/química , Cristalografia por Raios X , Multimerização Proteica , Thermotoga maritima/enzimologia , Sequência de Aminoácidos , Aminopeptidases/isolamento & purificação , Aminopeptidases/metabolismo , Cromatografia em Gel , Cristalização , Recombinação Homóloga , Modelos Moleculares
16.
Int J Nanomedicine ; 15: 3729-3740, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32547025

RESUMO

Background: Duraplasty is one of the most critical issues in neurosurgical procedures because the defect of dura matter will cause many complications. Electrospinning can mimic the 3D structure of the natural extracellular matrix whose structure is similar to that of dura matter. Poly(L-lactic acid) (PLLA) has been used to fabricate dura matter substitutes and showed compatibility to dural tissue. However, the mechanical properties of the PLLA substitute cannot match the mechanical properties of the human dura mater. Methods and Results: We prepared stereocomplex nanofiber membranes based on enantiomeric poly(lactic acid) and poly(D-lactic acid)-grafted tetracalcium phosphate via electrospinning. X-ray diffraction results showed the formation of stereocomplex crystallites (SC) in the composite nanofiber membranes. Scanning electron microscope observation images showed that composites nanofibers with higher SC formation can keep its original morphologies after heat treatment, suggesting the heat resistance of composite nanofiber membranes. Differential scanning calorimeter tests confirmed that the melting temperature of composite nanofiber membranes was approximately 222°C, higher than that of PLLA. Tensile testing indicated that the ultimate tensile strength and the elongation break of the stereocomplex nanofiber membranes were close to human dura matter. In vitro cytotoxicity studies proved that the stereocomplex nanofiber membranes were non-toxic. The neuron-like differentiation of marrow stem cells on the stereocomplex nanofiber membranes indicated its neuron compatibility. Conclusion: The stereocomplex nanofiber membranes have the potential to serve as a dura mater substitute.


Assuntos
Materiais Biomiméticos/química , Dura-Máter/fisiologia , Nanofibras/química , Poliésteres/química , Animais , Fosfatos de Cálcio/química , Varredura Diferencial de Calorimetria , Diferenciação Celular , Linhagem Celular , Cristalização , Humanos , Masculino , Células-Tronco Mesenquimais/citologia , Camundongos , Nanofibras/ultraestrutura , Neurônios/citologia , Ratos Sprague-Dawley , Estereoisomerismo , Temperatura , Difração de Raios X
17.
Biochim Biophys Acta Proteins Proteom ; 1868(9): 140460, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32474107

RESUMO

Eukaryotic serine racemase (SR) is a pyridoxal 5'-phosphate enzyme belonging to the Fold-type II group, which catalyzes serine racemization and is responsible for the synthesis of D-Ser, a co-agonist of the N-methyl-d-aspartate receptor. In addition to racemization, SR catalyzes the dehydration of D- and L-Ser to pyruvate and ammonia. The bifuctionality of SR is thought to be important for D-Ser homeostasis. SR catalyzes the racemization of D- and L-Ser with almost the same efficiency. In contrast, the rate of L-Ser dehydration catalyzed by SR is much higher than that of D-Ser dehydration. This has caused the argument that SR does not catalyze the direct D-Ser dehydration and that D-Ser is first converted to L-Ser, then dehydrated. In this study, we investigated the substrate and solvent isotope effect of dehydration of D- and L-Ser catalyzed by SR from Dictyostelium discoideum (DdSR) and demonstrated that the enzyme catalyzes direct D-Ser dehydration. Kinetic studies of dehydration of four Thr isomers catalyzed by D. discoideum and mouse SRs suggest that SR discriminates the substrate configuration at C3 but not at C2. This is probably the reason for the difference in efficiency between L- and D-Ser dehydration catalyzed by SR.


Assuntos
Desidratação , Eucariotos/enzimologia , Racemases e Epimerases/química , Racemases e Epimerases/metabolismo , Serina/metabolismo , Animais , Catálise , Cristalização , Dictyostelium/enzimologia , Cinética , Camundongos , Modelos Moleculares , Racemases e Epimerases/genética , Receptores de N-Metil-D-Aspartato , Especificidade por Substrato
18.
J Vis Exp ; (159)2020 05 12.
Artigo em Inglês | MEDLINE | ID: mdl-32478723

RESUMO

In single molecule fluorescence enzymology, background fluorescence from labeled substrates in solution often limits fluorophore concentration to pico- to nanomolar ranges, several orders of magnitude less than many physiological ligand concentrations. Optical nanostructures called zero mode waveguides (ZMWs), which are 100-200 nm in diameter apertures fabricated in a thin conducting metal such as aluminum or gold, allow imaging of individual molecules at micromolar concentrations of fluorophores by confining visible light excitation to zeptoliter effective volumes. However, the need for expensive and specialized nanofabrication equipment has precluded the widespread use of ZMWs. Typically, nanostructures such as ZMWs are obtained by direct writing using electron beam lithography, which is sequential and slow. Here, colloidal, or nanosphere, lithography is used as an alternative strategy to create nanometer-scale masks for waveguide fabrication. This report describes the approach in detail, with practical considerations for each phase. The method allows thousands of aluminum or gold ZMWs to be made in parallel, with final waveguide diameters and depths of 100-200 nm. Only common lab equipment and a thermal evaporator for metal deposition are required. By making ZMWs more accessible to the biochemical community, this method can facilitate the study of molecular processes at cellular concentrations and rates.


Assuntos
Microscopia de Fluorescência , Microtecnologia/métodos , Nanoestruturas/química , Imagem Individual de Molécula , Alumínio/química , Coloides/química , Cobre/química , Cristalização , Análise de Elementos Finitos , Transferência Ressonante de Energia de Fluorescência , Corantes Fluorescentes/química , Ouro/química , Microesferas , Poliestirenos/química , Porosidade
19.
Ann Biol Clin (Paris) ; 78(4): 349-362, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32540796

RESUMO

The prevalence of crystalline pathologies including urolithiasis, gallstones, vascular calcifications and crystalline arthritis, is very high in the general population beyond 60 years old. Characterization of microcrystals in tissue at the micrometer and at the nanometer scale through physico-chemical techniques constitutes a new opportunity for the physician to decipher the early stage of the pathogenesis of these biological entities. In this review, such description indicates a wide variety of the chemical process associated to the nucleation process directly from supersaturated solution or from organic support such as DNA or elastin. We will also discuss the case of vesicles which play a major role in the case of ectopic calcification situated in kidney tissue, namely the Randall's plaque. All this research focused on the very first steps of the genesis of pathological calcifications constitute a major step to develop specific therapy able to avoid the formation of these abnormal deposits in tissues. As already underlined, crystals may be the consequence of various pathologies, but they are also involved in the dysfunction of the tissues.


Assuntos
Calcinose/etiologia , Cristalização , Litíase/etiologia , Calcinose/metabolismo , Calcinose/patologia , Humanos , Cálculos Renais/etiologia , Cálculos Renais/metabolismo , Cálculos Renais/patologia , Litíase/metabolismo , Litíase/patologia , Urolitíase/etiologia , Urolitíase/metabolismo , Urolitíase/patologia , Calcificação Vascular/etiologia , Calcificação Vascular/metabolismo , Calcificação Vascular/patologia
20.
Sci Total Environ ; 729: 138999, 2020 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-32498172

RESUMO

Phosphorus (P) and nitrogen (N) recovery from swine manure has attracted considerable interest for biomass valorization. In this study, a catalytic-thermal hydrolysis (TH) process combined with struvite crystallization was investigated to promote P and N conversion from swine manure. Its potential as a phosphate-based fertilizer was investigated. Two periods for P solubilization and transformation were observed, i.e., an initial increase with reaction time followed by a decrease as treatment continued. Nitrogen conversion efficiency increased with increasing temperature and time. Treatment of swine manure by catalytic-TH with HCl + H2O2 showed the best performance for P and N solubilization and transformation. With a Mg2+/PO43- molar ratio of 2.49 and a pH of 9.11, the struvite crystallization efficiency from the supernatant after catalytic-TH with HCl + H2O2 reached 99.2%. Hydroculture bioassay showed that struvite had a positive effect on the early growth of wheat. The P concentrations in both root and shoot tissues for struvite treatment were more than two times higher than that of soluble P. These encouraging results warrant further studies on the conversion of biowaste given that recycling nutrients sources may outperform traditional synthetic fertilizers.


Assuntos
Esterco , Animais , Cristalização , Peróxido de Hidrogênio , Hidrólise , Compostos de Magnésio , Nitrogênio , Fosfatos , Fósforo , Estruvita , Suínos , Eliminação de Resíduos Líquidos
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