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1.
J Agric Food Chem ; 68(9): 2773-2782, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-32013417

RESUMO

The influence of covalent protein modifications resulting from the Maillard reaction (glycation) of casein and lactose on the noncovalent association behavior of the protein was studied. Nonenzymatic cross-linking with methylglyoxal (MGO) and glutaraldehyde (GTA) as well as enzymatic cross-linking with microbial transglutaminase (mTG) was investigated in comparison. Molar mass, particle size, and conformational characteristics of nonmicellar casein associates as well as the extent of intraparticle protein cross-linking were examined utilizing size-exclusion chromatography (SEC) combined with UV detection and static and dynamic light scattering. Cross-linking resulted in the stabilization of a certain fraction of casein associates, with particle sizes of approximately 30 nm in radius of gyration (Rg), and promoted an incorporation of further casein molecules into those particles, yielding molar masses (Mw) of 1.0-1.2 × 106 g/mol. When caseins were additionally conjugated with lactose during the early Maillard reaction, a further growth of the associates up to approximately 50 nm in Rg with a Mw of 2.1 × 106 g/mol was observed. Furthermore, glycation reactions induced a transition from slightly elongated, random-coil structures toward more anisotropic conformations. Associates consisting of caseins cross-linked with GTA appeared to preserve the original particle conformation.


Assuntos
Caseínas/química , Cromatografia em Gel , Reagentes para Ligações Cruzadas/química , Difusão Dinâmica da Luz , Glutaral/química , Lactose/química , Reação de Maillard , Tamanho da Partícula , Aldeído Pirúvico/química
2.
Histochem Cell Biol ; 153(2): 121-127, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31848702

RESUMO

Epoxy-embedded semithin sections are useful for the analysis of cell and tissue organization, as well as for the processing of samples for transmission electron microscopy. Because only a very limited number of staining protocols have been developed for epoxy-embedded sections; semithin sections are used infrequently compared to conventional paraffin sections. Here, we describe a simple and reproducible polychromatic protocol for the routine staining of epoxy-embedded semithin sections by adapting Twort's staining method (mixture of neutral red and fast green FCF). The method can be used for the visualization of cellular organization as well as for the detection of elastic and collagen fibers. The proposed protocol demonstrated the best results for samples fixed for transmission electron microscopy, which suggests, as we demonstrated here, that this staining protocol can also be used for correlative light and electron microscopy.


Assuntos
Resinas Epóxi/química , Técnicas Histológicas , Tetróxido de Ósmio/química , Coloração e Rotulagem , Animais , Glutaral/química , Camundongos , Camundongos Endogâmicos BALB C , Microscopia Eletrônica , Coelhos
3.
Talanta ; 207: 120305, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31594628

RESUMO

The 3-aminopropyltriethoxysilane (APTES) is a common method for biomolecule immobilization on silicon and silicon derivatives such as silicon nitride (Si3N4). However, there are many parameters which impact the efficiency of APTES modification such as APTES concentration and reaction time. Thus, various APTES concentrations (0.1%, 0.5%, 1%, 2%, 5%, and 10%) under different reaction times (15, 30, 60 and 120 min) were compared to achieve the optimal APTES modification condition which produced a thin and stable APTES layer on Si3N4 surface. The modified surfaces were characterized by contact angle (CA) measurement, Fourier transform infrared (FTIR) spectroscopy and spectroscopic ellipsometry to determine the wetting property, chemical bonding composition and surface thickness, respectively. In addition, biotin was used as a model to determine the effectiveness of APTES modification condition by coupling with glutaraldehyde (GA). The Alexa Flour 488 conjugated streptavidin was performed to visualize the presence of biotin using fluorescence microscopy due to the specifically binding between biotin and streptavidin. The atomic force microscopy (AFM) was utilized to determine the surface topology which was an indicator to demonstrate the agglomeration of APTES molecule. Moreover, ion sensitive field effect transistor (ISFET) was employed as a biosensor model to demonstrate the effect between surface thickness and sensitivity of biosensor. The results show that the APTES thickness is directly correlated to the APTES concentration and reaction time. Since the importance parameter for ISFET measurement is the distance between biomolecule and sensing membrane of ISFET, the thicker APTES layer negatively impacts the sensitivity of ISFET based biosensor because of the ion shielding effect. Therefore, these results would be valuable information for development of Si3N4 biosensor, especially ISFET based biosensor.


Assuntos
Técnicas Biossensoriais/métodos , Propilaminas/química , Silanos/química , Compostos de Silício/química , Glutaral/química , Cinética , Propriedades de Superfície , Transistores Eletrônicos
4.
Enzyme Microb Technol ; 132: 109397, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31731972

RESUMO

Pectin lyase (from Rohapect 10 L) was immobilized on glutaraldehyde supports at low ionic strength at pH 5, 6.5 or 8 and later incubated at pH 8 for 48 h. The activity recovery of the biocatalysts versus pectin was quite low, under 10% for all of the immobilized biocatalyst at 20 °C. However, a high stabilization was found when the enzyme was immobilized at pH 5, (e.g., the immobilized enzyme kept 83% of the activity when the free enzyme was fully inactivated (pH 4.8 and 55 °C in 5 h)). This biocatalyst increased the activity versus pectin in an almost exponential way when temperature increased until reach the maximum temperature used in the study (90 °C), conditions where the free enzyme was almost inactive. The immobilized biocatalyst was also active even at pH 9, where the free enzyme was fully inactive. This biocatalyst could be reused for pectin hydrolysis 5 times for 72 h reaction cycles at 40 °C maintaining more than 90% of the initial activity.


Assuntos
Enzimas Imobilizadas/metabolismo , Glutaral/química , Polissacarídeo-Liase/metabolismo , Estabilidade Enzimática , Enzimas , Concentração de Íons de Hidrogênio , Hidrólise , Temperatura
5.
Mater Sci Eng C Mater Biol Appl ; 105: 110024, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31546434

RESUMO

We extracted collagen (CL) from the scales of Ctenopharyngodon idella and fabricated a CL self-assembly film. Catalase (CAT) was immobilized on the films using cross-linking, adsorption, and embedding methods. The activity and operational stability of immobilized CAT were investigated, along with the influence of the concentration of glutaraldehyde (GTA) and of the initial concentration of embedded CAT. The results showed that the CL triple helix remained intact. Differential scanning calorimetry data showed that the thermal stability of CL was significantly improved by neutral salt-induced self-aggregation and GTA cross-linking. The immobilized enzyme had high activity and good operational stability. When the enzyme concentration reached 0.5 mg/mL, immobilized enzyme activity of grass carp scales reached a maximum of 2596 U/g, and after twenty-two uses, enzyme activity remained above 50%, and it could be reused >45 times (CAT = 0.5 mg/mL, GTA = 5%, Temperature = 30 °C, pH = 7). Moreover, the optimum temperature and pH of immobilized CAT were 35 °C and 7, respectively, while the same for free CAT was 30 °C and 7, respectively. This indicated that immobilization of CAT has a protective effect.


Assuntos
Escamas de Animais/química , Carpas/anatomia & histologia , Catalase/metabolismo , Colágeno/química , Enzimas Imobilizadas/metabolismo , Adsorção , Escamas de Animais/ultraestrutura , Animais , Estabilidade Enzimática , Glutaral/química , Peróxido de Hidrogênio/metabolismo , Concentração de Íons de Hidrogênio , Desnaturação Proteica , Padrões de Referência , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura
6.
Adv Colloid Interface Sci ; 272: 102016, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31421454

RESUMO

The design of immobilized enzyme preparations is an important and relevant area of modern sciences and technologies. Immobilization of enzymes from animal sources (component I) on natural carriers (component II) increases the system stability by protecting the active site of the enzyme from deactivation; facilitates the separation and accelerates the recovery of the enzyme. This makes reuse possible and provides a significant reduction in operating costs. Hydrolytic enzymes (such as lipases) and polysaccharides (such as chitosan) are the most promising of such pairs of components. The main attention here is devoted to the discussion on lipase immobilization on polysaccharide (mainly - chitin and chitosan). Based on the analysis of the available literature, the most adequate method is the immobilization of lipase from porcine pancreas (LPP) on polysaccharide particles (such as chitin or chitosan) pre-treated with ultrasound (to increase the particle surface area) and glutaraldehyde (for particle activation) that shows reasonably high LPP activity and stability. In order to increase further the activity of the lipase, some authors proposed to incorporate a spacer in the form of 1,3-diaminopropane (or 1,3-diaminobutane) prior to activation of the surface of the chitosan particles. In particular cases, the use of chitin (instead of chitosan) may be an alternative solution for biotechnological applications. Recently the idea of constructing "supramolecular enzyme systems" realized in the so-called "coimmobilized multienzymatic systems" strategy. The most fascinating example is the combined assay of a mixture of native LPP, glycerol kinase (from Cellulomonas) and glycerol-3-phosphate oxidase (from Aerococcus viridans) linked by glutaraldehyde to chitosan (as shell for inorganic nanoparticle core). This material was placed on a Pt-electrode as biosensor and was successfully applied for amperometric determination of the triglyceride level in the serum of healthy and diseased person. Thus, the whole innovative research-production sequence is described by Aggarwal V. and Pundir C.S.: from simple components to advanced material and further biomedical application. Thus, the following approach of lipase immobilization appears the most promising for future applications: a few types of lipases or the combination of LPP with some other enzymes immobilized simultaneously on multifunctional carriers (as nanohybrids of inorganic core and polysaccharide shell).


Assuntos
Enzimas Imobilizadas/química , Lipase/química , Lipase/metabolismo , Polissacarídeos/química , Animais , Biotecnologia/métodos , Quitina/química , Quitosana/química , Enzimas Imobilizadas/metabolismo , Glutaral/química , Nanopartículas/química , Suínos
7.
J Pharm Biomed Anal ; 175: 112795, 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31387029

RESUMO

Magnetic ligand fishing is one of the most widely used methods to screen and separate potentially bioactive compounds from complex mixtures. However, it is poorly understood the ambiguous relations between immobilized enzyme activity and fishing results (accuracy and sensitivity). Therefore, to investigate the underlying relationship of them, we fabricated the immobilized enzyme with different activities by introducing a novel support material, nickel ions (Ni2+) functionalized magnetic mesoporous silica microspheres (MMSM@PDA-Ni2+). It possesses a higher activity than the previous report because of site-directed immobilization. Then, the immobilized COX-2 with different activities were prepared using different immobilization methods, including Ni2+ affinity-oriented immobilization, polydopamine (PDA) covalent immobilization, and conventional glutaraldehyde (GA) covalent immobilization. A standard mixture (COX-2 inhibitors and noninhibitors) and green tea extract were used to compare and evaluate the fishing results systematically. It displayed the fished inhibitors were dramatically reduced with the decreased activity of immobilized COX-2, indicating that immobilized enzyme activity played a critical role in a reliable magnetic ligand fishing analysis. This development questions some of the previous studies aimed at rapid screening bioactive compounds in natural products and opens new possibilities for accurate and sensitive magnetic ligand fishing analysis. Also, the introduced novel materials with mild immobilization strategy preserve enzyme activity and spatial conformational, therefore, provides a valuable tool in future applications.


Assuntos
Inibidores de Ciclo-Oxigenase 2/química , Enzimas Imobilizadas/química , Produtos Biológicos/química , Descoberta de Drogas/métodos , Glutaral/química , Indóis/química , Ligantes , Fenômenos Magnéticos , Magnetismo/métodos , Microesferas , Níquel/química , Extratos Vegetais/química , Polímeros/química , Chá/química
8.
Int J Biol Macromol ; 137: 1060-1067, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31295494

RESUMO

The physical (UV irradiation) and chemical (glutaraldehyde) modification of galactomannan (GMP) film was successfully prepared in this study. The data indicated that the UV irradiation with increasing dosage of photo-initiator could gradually consume the free hydroxyl groups in GMP to form the crosslinked networks, reducing the hydrophilic property and water vapor permeability of the modified film. The tensile strength of the obtained film with 20% sodium benzoate addition achieved 2.8 times higher than the control sample. In comparison, aldol reaction between hydroxyl groups in GMP and glutaraldehyde resulted in a homogeneous surface of films, and the introduction of glutaraldehyde significantly increased the hydrophilicity of the modified films. After chemical treatment, the value of elongation at break was remarkably enhanced by nearly 15 times, corresponding to the great flexible property against stretching.


Assuntos
Embalagem de Alimentos , Glutaral/química , Mananas/química , Raios Ultravioleta , Fenômenos Químicos , Interações Hidrofóbicas e Hidrofílicas , Fenômenos Mecânicos , Permeabilidade , Solubilidade , Vapor , Temperatura
9.
Colloids Surf B Biointerfaces ; 182: 110339, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31284147

RESUMO

Biocompatible polymers are being used in recent times for treating skin injuries and burn wounds. Polymers like Poly Vinyl Alcohol and Chitosan are proven to be biocompatible with least toxic to treat injuries with minimal side-effects. Curcumin, a primary component of turmeric has anti-inflammatory properties and anti-microbial activity but has extremely low bioavailability. Converting Curcumin to its nano form increased its bioavailability exponentially allowing it to play a vital role in the process of wound healing. This PVA/Chi/Cur patch increased cell proliferation as shown by the results of cell line studies and MTT assay. Its anti-bacterial activity against four major bacterial strains commonly found in wound sites and water retainability indicates it to be a perfect material for wound treatment. Results of in-vivo studies conducted on wistar rats by testing the patch's healing ability on a surgically induced wound displayed its superiority over commercial ointment. This treatment for epidermal wounds reduces the frequency in which the patch has to be replaced and increases the rate of wound rehabilitation.


Assuntos
Antibacterianos/farmacologia , Anti-Inflamatórios/farmacologia , Quitosana/química , Curcumina/farmacologia , Álcool de Polivinil/química , Ferida Cirúrgica/tratamento farmacológico , Cicatrização/efeitos dos fármacos , Animais , Antibacterianos/química , Anti-Inflamatórios/química , Bacillus subtilis/efeitos dos fármacos , Bacillus subtilis/crescimento & desenvolvimento , Bandagens , Reagentes para Ligações Cruzadas/química , Curcumina/química , Preparações de Ação Retardada/química , Epiderme/efeitos dos fármacos , Epiderme/lesões , Epiderme/microbiologia , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Glutaral/química , Humanos , Testes de Sensibilidade Microbiana , Pseudomonas aeruginosa/efeitos dos fármacos , Pseudomonas aeruginosa/crescimento & desenvolvimento , Ratos , Ratos Wistar , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/crescimento & desenvolvimento , Ferida Cirúrgica/microbiologia , Ferida Cirúrgica/patologia
10.
Food Chem ; 300: 125249, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31352291

RESUMO

Under the optimal conditions, a crosslinked electrospun polyvinyl alcohol/cinnamon essential oil/ß-cyclodextrin (CPVA-CEO-ß-CD) nanofibrous films for sustained release of antimicrobials were successfully prepared. Cinnamon essential oil (CEO) can be sustainably released due to CPVA-CEO-ß-CD nanofibers complex delivery systems. The chemical crosslinking and physical welding achieved simultaneously by glutaraldehyde atomization fumigation, making fibers more suitable for fresh food packaging. Nanofibrous films were characterized in terms of SEM, ATR-FTIR, DSC, water contact angle analysis and antibacterial trials. ATR-FTIR and DSC data indicated that CEO was encapsulated in a ß-CD cavity and they coexisted in PVA nanofibers. The water contact angle of the crosslinked PVA nanofibrous films increased with CEO and the values were always below 90°. Crosslinked nanofibers possessed fine properties in vitro antibacterial against Staphylococcus aureus and Escherichia coli. Furthermore, CPVA/ß-CD/CEO nanofibrous films delayed decay of mushroom during storage, indicating their potential implementation in active food packaging.


Assuntos
Agaricales/fisiologia , Embalagem de Alimentos/métodos , Nanofibras/química , Álcool de Polivinil/química , beta-Ciclodextrinas/química , Antibacterianos/química , Antibacterianos/farmacologia , Cinnamomum zeylanicum/química , Reagentes para Ligações Cruzadas/química , Escherichia coli/efeitos dos fármacos , Embalagem de Alimentos/instrumentação , Armazenamento de Alimentos , Glutaral/química , Microscopia Eletrônica de Varredura , Óleos Voláteis/química , Espectroscopia de Infravermelho com Transformada de Fourier , Staphylococcus aureus/efeitos dos fármacos
11.
Soft Matter ; 15(36): 7127-7136, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31334536

RESUMO

Intermediate filaments are cytoskeletal proteins that are key regulators of cell mechanics, a role which is intrinsically tied to their hierarchical structure and their unique ability to accommodate large axial strains. However, how the single-filament response to applied strains translates to networks remains unclear, particularly with regards to the crosslinking role played by the filaments' disordered "tail" domains. Here we test the role of these noncovalent crosslinks in the nonlinear rheology of reconstituted networks of the intermediate filament protein vimentin, probing their stress- and rate-dependent mechanics. Similarly to previous studies we observe elastic stress-stiffening but unlike previous work we identify a characteristic yield stress σ*, above which the networks exhibit rate-dependent softening of the network, referred to as inelastic fluidization. By investigating networks formed from tail-truncated vimentin, in which noncovalent crosslinking is suppressed, and glutaraldehyde-treated vimentin, in which crosslinking is made permanent, we show that rate-dependent inelastic fluidization is a direct consequence of vimentin's transient crosslinking. Surprisingly, although the tail-tail crosslinks are individually weak, the effective timescale for stress relaxation of the network exceeds 1000 s at σ*. Vimentin networks can therefore maintain their integrity over a large range of strains (up to ∼1000%) and loading rates (10-3 to 10-1 s-1). Our results provide insight into how the hierarchical structure of vimentin networks contributes to the cell's ability to be deformable yet strong.


Assuntos
Filamentos Intermediários/metabolismo , Vimentina/química , Reagentes para Ligações Cruzadas/química , Elasticidade , Glutaral/química , Cinética , Modelos Moleculares , Multimerização Proteica , Reologia
12.
Pak J Pharm Sci ; 32(3 (Supplementary)): 1137-1143, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31303582

RESUMO

The aim of study was cross linking of high molecular weight chitosan nanoparticles containing 5-fluorouracil to improve dissolution rate and ultimately enhance its bioavailability by reverse emulsion/micelles method and cross-linking agent i.e. glutaraldehyde (GA 25% aqueous solution in water). The nature and outer morphologies were evaluated by scanning electron microscopy (SEM). Drug release models were functional to support way from cross linked NPs. Cross linking of 5-fluorouracil with glutaraldehyde improved dissolution rate. Mean dissolution time of 5-fluorouracil decreased significantly upon reverse emulsion/cross linking as encapsulated drug is protective and thermally stable within cross linked chitosan NPs. FTIR studies showed formation of intermolecular hydrogen bonding between 5-fluorouracil and GA-co-CHNPs. DSC studies indicated a less crystalline state of 5-fluorouracil in cross linking. SEM showed spherical nanoparticles with somewhat rough surface. 5-FU release followed Korsmeyer-Peppas model which indicate diffusion and dissociation control drug release from GA-co-CH-NPs. 5-FU cross linked chitosan nanoparticles can be safe and useful tool for other chemotherapeutic agents.


Assuntos
Quitosana/química , Preparações de Ação Retardada/química , Preparações de Ação Retardada/farmacocinética , Fluoruracila/farmacocinética , Nanopartículas/química , Disponibilidade Biológica , Varredura Diferencial de Calorimetria , Reagentes para Ligações Cruzadas/química , Estabilidade de Medicamentos , Fluoruracila/química , Glutaral/química , Ligação de Hidrogênio , Microscopia Eletrônica de Varredura , Peso Molecular , Tamanho da Partícula , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
13.
Talanta ; 203: 203-209, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31202327

RESUMO

A label-free liquid crystal (LC) immosensorsensor based on the orientation changes of LC was developed for the detection of HBD-2 (human ß-defensin-2) through competitive immunoassay. HBD-2 was tethered onto the semassembled film surface on a glass slide via a cross-linker glutaradehyde. The DMOAP/APTES/GA (N,N-dimethyl-N-octadecyl (3-aminopropyl) trimethoxysilyl chloride/(3-aminopropyl) trimethoxysilane/glutaraldehyde) mixed self-assembled monolayers formed by both long and short alkyls could cause vertical alignment uniformly of liquid crystal. The specific binding of anti-HBD-2 antibody and HBD-2 induced the homeotropic-to-tilted transition of liquid crystal, making a visible optical change observed under the crossed polarized light and achieving the detection of HBD-2. The average gray-scale intensity of optical appearances has a good linear relationship with the concentration of HBD-2 when the concentration of HBD-2 is in the range of 1-10 ng mL-1 and the linear correlation coefficient is 0.9956. The limit of quantification is 0.53 ng mL-1 for the HBD-2. This study offers a simple, highly sensitive and specific, label -free method for HBD-2 detection.


Assuntos
Técnicas Biossensoriais/métodos , Imunoensaio/métodos , Cristais Líquidos/química , beta-Defensinas/sangue , Animais , Anticorpos Imobilizados/imunologia , Bovinos , Glutaral/química , Humanos , Limite de Detecção , Compostos de Organossilício/química , Transição de Fase , Propilaminas/química , Silanos/química , beta-Defensinas/imunologia
14.
Anal Chim Acta ; 1074: 131-141, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31159933

RESUMO

Semiconducting single-walled carbon nanotubes (s-SWCNTs) have been demonstrated as an excellent material for transistors, miniaturized devices and sensors due to their high carrier mobility, stability, scattering-free ballistic transport of carriers etc. Herein, we have designed a biosensor to selectively detect methyl parathion (MP, organophosphorus pesticide) using glutaraldehyde (Glu) cross-linked with acetylcholinesterase (AChE) immobilized on s-SWCNTs wrapped with bovine serum albumin (BSA). The fabricated biosensor was characterized and confirmed by Fourier-transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). In the presence of MP, the effective interaction between AChE and MP favours the accumulation of MP-AChE complex on the glassy carbon electrode (GCE) surface which reduces the electron transfer property. Based on this interaction, detection of various concentration of MP was demonstrated by SWV using BSA/AChE-Glu-s-SWCNTs composite modified electrode. The proposed biosensor exhibited a wide linear range (WLR) for MP target in 100 mM phosphate buffered saline solution (PBS) (pH 7.4) from 1 × 10-10 M to 5 × 10-6 M with a limit of detection (LOD) of 3.75 × 10-11 M. In addition, the BSA/AChE-Glu-s-SWCNTs/GCE biosensor showed good repeatability and reproducibility for MP detection. Moreover, the proposed biosensor showed better electrode stability when stored at 4 °C. This new electrochemical biosensor is also exhibited high selectivity and sensitivity for MP, which made it possible to test MP in real strawberry and apple juices. Furthermore, the BSA/AChE-Glu-s-SWCNTs/GCE offered a favourable electron transfer between the acetylthiocholine chloride (ATCl) and electrode interface than BSA/AChE-s-SWCNTs/GCE, s-SWCNTs/GCE and bare GCE.


Assuntos
Acetilcolinesterase/química , Inseticidas/análise , Metil Paration/análise , Nanocompostos/química , Nanotubos de Carbono/química , Soroalbumina Bovina/química , Animais , Técnicas Biossensoriais/métodos , Carbono , Bovinos , Reagentes para Ligações Cruzadas/química , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Electrophorus , Enzimas Imobilizadas/química , Contaminação de Alimentos/análise , Fragaria/química , Glutaral/química , Inseticidas/química , Limite de Detecção , Malus/química , Metil Paration/química , Reprodutibilidade dos Testes
15.
J Microbiol Biotechnol ; 29(6): 913-922, 2019 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-31154745

RESUMO

Magnetic Ni0.7Co0.3Fe2O4 nanoparticles that were prepared via the rapid combustion process were functionalized and modified to obtain magnetic Ni0.7Co0.3Fe2O4@SiO2-CHO nanocomposites, on which penicillin G acylase (PGA) was covalently immobilized. Selections of immobilization concentration and time of fixation were explored. Catalytic performance of immobilized PGA was characterized. The free PGA had greatest activity at pH 8.0 and 45oC while immobilized PGA's a ctivities peaked a t pH 7.5 and 45°C. Immobilized PGA had better thermal stability than free PGA at the range of 30-50°C for different time intervals. The activity of free PGA would be 0 and that of immobilized PGA still retained some activities at 60°C after 2 h. Vmax and Km of immobilized PGA were 1.55 mol/min and 0.15 mol/l, respectively. Free PGA's Vmax and Km separately were 0.74 mol/min and 0.028 mol/l. Immobilized PGA displayed more than 50% activity after 10 successive cycles. We concluded that immobilized PGA with magnetic Ni0.7Co0.3Fe2O4@SiO2-CHO nanocomposites could become a novel example for the immobilization of other amidohydrolases.


Assuntos
Cobalto/química , Enzimas Imobilizadas/química , Nanopartículas de Magnetita/química , Nanocompostos/química , Níquel/química , Penicilina Amidase/química , Penicilina Amidase/metabolismo , Catálise , Estabilidade Enzimática , Enzimas Imobilizadas/metabolismo , Glutaral/química , Concentração de Íons de Hidrogênio , Dióxido de Silício/química , Temperatura
16.
Nucleic Acids Res ; 47(11): 5950-5962, 2019 06 20.
Artigo em Inglês | MEDLINE | ID: mdl-31106331

RESUMO

Carboxysomes, protein-coated organelles in cyanobacteria, are important in global carbon fixation. However, these organelles are present at low copy in each cell and hence must be segregated to ensure transmission from one generation to the next. Recent studies revealed that a DNA partition-like ParA-ParB system mediates carboxysome maintenance, called McdA-McdB. Here, we describe the first McdA and McdB homolog structures. McdA is similar to partition ParA Walker-box proteins, but lacks the P-loop signature lysine involved in ATP binding. Strikingly, a McdA-ATP structure shows that a lysine distant from the P-loop and conserved in McdA homologs, enables ATP-dependent nucleotide sandwich dimer formation. Similar to partition ParA proteins this ATP-bound form binds nonspecific-DNA. McdB, which we show directly binds McdA, harbors a unique fold and appears to form higher-order oligomers like partition ParB proteins. Thus, our data reveal a new signature motif that enables McdA dimer formation and indicates that, similar to DNA segregation, carboxysome maintenance systems employ Walker-box proteins as DNA-binding motors while McdB proteins form higher order oligomers, which could function as adaptors to link carboxysomes and provide for stable transport by the McdA proteins.


Assuntos
Proteínas de Bactérias/metabolismo , Cianobactérias/metabolismo , Cyanothece/metabolismo , Organelas/química , Adenosina Trifosfatases/metabolismo , Trifosfato de Adenosina/química , Motivos de Aminoácidos , Proteínas de Bactérias/química , Ciclo do Carbono , Cristalografia por Raios X , DNA Bacteriano/metabolismo , Proteínas de Ligação a DNA/metabolismo , Dimerização , Escherichia coli , Glutaral/química , Ligação Proteica , Dobramento de Proteína
17.
Chemosphere ; 230: 40-50, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31102870

RESUMO

Photocatalytic membranes (PMs), coupling of membrane filtration and photocatalysis, have exhibited the potential for application in the wastewater treatment. In this study, we firstly adopted the supramolecular aggregates of melamine (M), cyanuric acid (C), and urea (U) in specific dimethyl sulfoxide (DMSO) as precursors to prepare carbon nitride MCU-C3N4 with high photocatalytic performance, and a kind of novel-designed photocatalytic membrane was prepared via filtrating the mixture of graphene oxide (GO) nanosheets and MCU-C3N4 on PVDF membrane supports, and then crosslinked using glutaraldehyde (GA) to construct a steady coating on the GO/MCU-C3N4/PVDF membrane. GO/MCU-C3N4/PVDF composite membrane exhibited higher permeation flux than that of GO/PVDF membrane and exhibited excellent separation performance for oil-in-water emulsion. A visible light-driven self-cleaning four-stage filtration by a self-built dead-end filtration system was carried out to evaluate membrane antifouling property, and GO/MCU-C3N4/PVDF membrane (M2) possessed higher flux recovery ratio (FRR) (∼92.36%) and lower irreversible fouling resistance (Rir) ratio (∼8%) under 30min visible-light irradiation, maintaining relatively higher FRR (>72%) during 4 cycling of four-stage filtrating experiments. GO/MCU-C3N4/PVDF PMs are equipped with high permeation flux, separation performance, anti-fouling property and stability, indicating potential application in water treatment.


Assuntos
Filtração/instrumentação , Filtração/métodos , Glutaral/química , Grafite/química , Membranas Artificiais , Nitrilos/química , Polivinil/química , Purificação da Água/métodos , Catálise , Luz , Triazinas/química
18.
Int J Biol Macromol ; 134: 604-612, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31100395

RESUMO

In the present research the effect of incorporating cinnamon essential oil (CEO), oleic acid (OA) and glutaraldehyde (GL) on antimicrobial, antioxidant, mechanical, physical and morphological properties of chitosan-carboxymethyl cellulose composite films were investigated. Cross-linking effect of GL (as determined by FTIR analysis) significantly resulted in higher mechanical strength and lower water vapor permeability (WVP). Cross-linked films incorporated with CEO revealed higher and steady state antioxidant activity as well as in vitro antimicrobial properties against Listeria monocytogenes and Pseudomonas aeruginosa. Thickness, elongation at break (EAB) and WVP increased by including OA; however, water solubility significantly decreased. Color properties and microstructure of composite films were significantly affected by the additives as confirmed by SEM analyses. We showed that the antimicrobial, antioxidant, mechanical and physical properties of chitosan-carboxymethyl cellulose composite films could be improved via incorporating CEO and GL to the film matrix.


Assuntos
Quitosana/análogos & derivados , Quitosana/química , Cinnamomum zeylanicum/química , Glutaral/química , Óleos Voláteis/química , Ácido Oleico/química , Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Fenômenos Químicos , Fenômenos Mecânicos , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Solubilidade , Análise Espectral
19.
J Biosci Bioeng ; 128(4): 504-509, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31029540

RESUMO

In this paper, a biocompatible, non-toxic porous chitosan microcarrier was prepared by high voltage electrostatic field and freeze drying technology. The chitosan solution was pushed from the syringe drop into the sodium polyphosphate solution using a booster pump. The droplet diameter of the chitosan solution was adjusted by the voltage of the electrostatic field formed between the syringe and the sodium polyphosphate solution. The droplets were dropped into a sodium polyphosphate solution to form microspheres. The microspheres were subsequently immersed in 25% (v/v) glutaraldehyde for crosslinking to enhance the mechanical strength of the microspheres. These microspheres were then frozen and lyophilized to form a microcarrier. By performance characterization, these microcarriers had a particle size of 400-500 µm, a pore size of 15-20 µm, and a porosity of 90%. Under simulated human environmental conditions, the 21-day degradation rate was about 30%, indicating that the microcarriers have potential clinical value.


Assuntos
Quitosana/química , Eletricidade Estática , Células Cultivadas , Liofilização , Glutaral/química , Humanos , Microesferas , Tamanho da Partícula , Polifosfatos/química , Porosidade
20.
Anal Bioanal Chem ; 411(13): 2755-2758, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30972470

RESUMO

Erythropoietin (EPO) is a glycoprotein hormone which promotes red cell replenishment and is also a global biotherapeutic medicine widely used to treat anaemia resulting, for example, from chemotherapy. Requirements of the European Pharmacopoeia stipulate that the level of dimer must be quantified in clinical EPO products (with a limit of 2%). Quantification is hampered by the lack of reference preparations containing stable measurable levels of EPO dimer, but the reproducible generation of a stable dimerised EPO preparation is challenging. We describe here the development of a lyophilised, chemically cross-linked EPO preparation, which has good stability and may be used for calibration and system suitability assurance for the size exclusion chromatographic separation of EPO preparations. Graphical abstract.


Assuntos
Reagentes para Ligações Cruzadas/química , Eritropoetina/química , Glutaral/química , Calibragem , Cromatografia em Gel/métodos , Cromatografia em Gel/normas , Eritropoetina/análise , Eritropoetina/uso terapêutico , Liofilização , Humanos , Multimerização Proteica , Estabilidade Proteica , Controle de Qualidade , Padrões de Referência
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