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1.
Food Chem ; 352: 129410, 2021 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-33677210

RESUMO

The purpose of this exploration was to determine the density and volumetric properties of the aqueous solution of Na2H2P2O7 with the molality varied from 0.08706 to 0.88402 mol·kg-1 measured at temperature intervals of 5 K from 283.15 to 363.15 K at 101.325 kPa using Anton Paar Digital vibrating-tube densimeter. The thermal expansion coefficient (α), apparent molar volume (VΦ), expansibility (ϕE), and partial molar volume (VB) of Na2H2P2O7 (aq) against temperature and molality have been evaluated from density data. On the basis of Pitzer ion-interaction apparent molar volume theory, the Pitzer single-salt parameters (ßM,X0v, ßM,X1v, ßM,X2v and CM,Xv, MX = Na2H2P2O7), and their correlation coefficients ai of the temperature-dependence formula f (i, p, T) = a1 + a2ln(T/298.15) + a3(T - 298.15) + a4/(620 - T) + a5/(T - 227) for Na2H2P2O7 were obtained for the first time. It was revealed that predicted apparent molar volumes agreed well with the experimental values indicating the single salt parameters and the temperature-dependent formula are reliable.


Assuntos
Difosfatos/química , Temperatura , Água/química , Pressão , Soluções
2.
Int J Mol Sci ; 22(2)2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33467686

RESUMO

Phosphate-based glasses (PBGs) offer significant therapeutic potential due to their bioactivity, controllable compositions, and degradation rates. Several PBGs have already demonstrated their ability to support direct cell growth and in vivo cytocompatibility for bone repair applications. This study investigated development of PBG formulations with pyro- and orthophosphate species within the glass system (40 - x)P2O5·(16 + x)CaO·20Na2O·24MgO (x = 0, 5, 10 mol%) and their effect on stem cell adhesion properties. Substitution of phosphate for calcium revealed a gradual transition within the glass structure from Q2 to Q0 phosphate species. Human mesenchymal stem cells were cultured directly onto discs made from three PBG compositions. Analysis of cells seeded onto the discs revealed that PBG with higher concentration of pyro- and orthophosphate content (61% Q1 and 39% Q0) supported a 4.3-fold increase in adhered cells compared to glasses with metaphosphate connectivity (49% Q2 and 51% Q1). This study highlights that tuning the composition of PBGs to possess pyro- and orthophosphate species only, enables the possibility to control cell adhesion performance. PBGs with superior cell adhesion profiles represent ideal candidates for biomedical applications, where cell recruitment and support for tissue ingrowth are of critical importance for orthopaedic interventions.


Assuntos
Adesão Celular , Técnicas de Cultura de Células , Vidro/química , Células-Tronco Mesenquimais/efeitos dos fármacos , Fosfatos/química , Materiais Biocompatíveis/química , Cálcio/química , Varredura Diferencial de Calorimetria , Núcleo Celular/metabolismo , Difosfatos/química , Consolidação da Fratura , Proteínas de Fluorescência Verde/metabolismo , Humanos , Espectroscopia de Ressonância Magnética , Teste de Materiais , Células-Tronco Mesenquimais/citologia , Osteoblastos/citologia , Difração de Raios X
3.
Food Chem ; 346: 128910, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33460961

RESUMO

Phosphates are commonly included in meat processing, where oxidation is inevitable, to improve water binding. This present study attempted to reveal the interactive roles of protein oxidation and tetrasodium pyrophosphate (TSPP) on the crosslinking pattern of myosin mediated by transglutaminase (TGase). Mild oxidation at 1 mM H2O2 facilitated the TGase-initiated crosslinking, with the dominate crosslinking site shifted from S1 (in nonoxidized myosin) to Rod. The introduction of TSPP alleviated the oxidation stress on proteins, and was conductive to the crosslinking reaction notably at the LMM domain. The crosslinking sites in untreated myosin were identified as Gln-613 (S1) and Gln-1498 (LMM) by amino-acid sequence analysis, while strongly oxidation resulted in the loss of Gln-1498. Contrastively, four new reactive crosslinking sites were generated by TSPP, one (Gln-558/Gln-567) located on S1 and three (Gln-1362, Gln-1374, and Gln-1423/Gln-1426) on LMM. Yet, Gln-1362 was eliminated under strong oxidation at 50 mM H2O2.


Assuntos
Proteínas de Bactérias/metabolismo , Difosfatos/química , Subfragmentos de Miosina/metabolismo , Transglutaminases/metabolismo , Sequência de Aminoácidos , Animais , Peróxido de Hidrogênio/química , Carne/análise , Subfragmentos de Miosina/química , Oxirredução , Suínos
4.
Food Chem ; 340: 128185, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33010647

RESUMO

In this study, sodium tripolyphosphate (STP) and tetrasodium pyrophosphate (TSPP) were utilized to modify duck egg white protein (EWP). The phosphorylated EWP was prepared as egg white gel (EWG) by adding sodium hydroxide. The phosphorus content of EWP reached 2.18 mg/g and 2.07 mg/g with the addition of STP and TSPP, respectively, after 2 h phosphorylation. The average particle size, absolute zeta potential value, and surface hydrophobicity of EWP increased significantly during phosphorylation. FTIR results indicate that phosphorylation reduced the random structure and α-helical content while increasing the content of ß-sheets and ß-turn. The mechanical and rheological properties of EWG decreased obviously after phosphorylation. A three-dimensional porous network microstructure was formed, and the gel with added TSPP had larger pores. Adding STP and TSPP to EWG weakened its salt and solvent sensitivity. The findings provide a direction for the exploration of gel properties after protein modification.


Assuntos
Álcalis/química , Patos , Proteínas do Ovo/química , Animais , Difosfatos/química , Géis , Interações Hidrofóbicas e Hidrofílicas , Tamanho da Partícula , Fosforilação , Reologia , Cloreto de Sódio/química , Hidróxido de Sódio/química
5.
Food Chem ; 338: 128146, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33091990

RESUMO

Myofibrillar protein isolated from beef muscles were treated with 3 phosphates (Sodium Hexametaphosphate, sodium tripolyphosphate, sodium pyrophosphate) with different concentrations of 0.3%, 0.6%, 0.9%, 1.2% respectively. Protein solubility, surface hydrophobicity and reactive sulfhydryl group was determined. Atomic force microscopy was used to observe the microscopic protein surface. SDS-PAGE was carried out to determine the proteolysis of myofibrillar protein. The solubility and surface hydrophobic bond of myofibrillar protein was highly increased and the diameter decreased by SHMP, TSPP, STPP. Reactive sulfhydryl groups increased after SHMP addition, but slightly decreased in STPP and TSPP treated MP. TSPP and STPP had the same effect on myofibrillar microstructure and was different from SHMP. Three phosphates all caused MP unfolding. The MP gel complexity was increased, and roughness was decreased after phosphates addition, indicating phosphates helped to construct a more ordered and smoother gel microcosmic surface.


Assuntos
Difosfatos/química , Microscopia de Força Atômica , Proteínas Musculares/química , Fosfatos/química , Polifosfatos/química , Carne Vermelha , Animais , Bovinos , Interações Hidrofóbicas e Hidrofílicas , Solubilidade
6.
Anal Chim Acta ; 1113: 18-25, 2020 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-32340665

RESUMO

Magnetic trapping has been employed in the development of analytical methods owing to its ease and simplicity in handling samples. Nevertheless, the generation of functional probes is usually time consuming. A new and simple affinity method that uses gadolinium ion (Gd3+), a magnetic ion, as affinity probe for magnetic tapping of pathogenic bacteria was demonstrated in the present study. Escherichia coli O157:H7, Staphylococcus aureus, and Acinetobacter baumannii were selected as model bacteria. The model bacteria were magnetically isolated after incubation in Tris buffer (pH 8) containing Gd3+ (0.1 M) under microwave heating (power: 180 W, 90 s × 3). The resultant Gd3+-bacterium conjugates possessed sufficient magnetism, resulting in magnetic aggregations by an external magnet (∼4,000 Gauss). For ease of magnetic isolation, the sample containing Gd3+-bacterium complexes was stirred by a small magnet. After 1 h, the magnet attached with precipitates, i.e., Gd3+-bacterium conjugates, was readily removed using a pair of tweezers. The bacteria in the resultant conjugates were characterized by matrix-assisted laser desorption/ionization mass spectrometry. The limits of detection of the current approach toward E. coli O157:H7, S. aureus, and A. baumannii in complex samples were ∼104-105 cells mL-1.


Assuntos
Acinetobacter baumannii/isolamento & purificação , Técnicas Bacteriológicas/métodos , Escherichia coli O157/isolamento & purificação , Gadolínio/química , Staphylococcus aureus/isolamento & purificação , Acinetobacter baumannii/química , Animais , Sangue/microbiologia , Bovinos , Complexos de Coordenação/química , Difosfatos/química , Escherichia coli O157/química , Limite de Detecção , Fenômenos Magnéticos , Microbiologia do Solo , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Staphylococcus aureus/química
7.
J Nutr ; 150(5): 1109-1115, 2020 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-32073619

RESUMO

BACKGROUND: Bouillon cubes are a potential vehicle for iron fortification. They are currently fortified with ferric pyrophosphate (FePP), which is known to be poorly absorbed. The objective of this study was to assess the iron absorption of Aspergillus oryzae grown in FePP (ASP-p) and compare it with FePP and ferrous sulfate (FeSO4)-fortified bouillon cubes. METHODS: In 2 single-blinded, crossover studies, healthy women with serum ferritin concentrations <40 µg/L were randomly assigned to consume a rice-vegetable meal with iron-fortified chicken bouillon. Subjects in study I (n = 17, 18-26 y) consumed iron from both iron sources as 57FePP and 58ASP-p (intrinsically labeled with 58FePP) with a meal containing 4.2 mg of total iron provided for 3 d. Study II (n = 18, 18-29 y) was similar except that subjects consumed 57FeSO4 and 58ASP-p. Whole-blood stable isotope enrichment after 14 d was used to measure fractional iron absorption. Hemoglobin, hematocrit, serum ferritin, hepcidin, and serum C-reactive protein were analyzed at baseline and at 14 d. A t test was used to compare the mean differences in fractional absorptions within each study and baseline characteristics between studies. RESULTS: Geometric mean (95% CI) fractional iron absorption of FePP [0.94% (0.63%, 1.40%)] was lower than ASP-p [2.20% (1.47%, 3.30%)] (P < 0.0001) in study I. In study II, ASP-p fractional absorption [2.98% (2.03%, 4.38%)] was lower than that of FeSO4 [9.88% (6.70%, 14.59%)] (P < 0.0001). Both ferritin (r = -0.41, P = 0.014) and hepcidin (r = -0.42, P = 0.01) concentrations were inversely correlated with ASP-p iron absorption. Fractional absorption of ASP-p was also positively correlated with FePP (r = 0.92, P < 0.0001) and FeSO4 (r = 0.52, P < 0.02) absorption. CONCLUSIONS: ASP-p-fortified bouillon provided 2.3-fold higher absorbable iron than the currently used FePP. Bouillon fortified with ASP-p may contribute sufficient bioavailable iron to meet the daily iron requirements in young women only if consumed with other iron-fortified staple foods. This trial was registered at clinicaltrials.gov as NCT03586245.


Assuntos
Aspergillus oryzae , Difosfatos/farmacocinética , Alimentos Fortificados , Ferro/farmacocinética , Adolescente , Adulto , Estudos Cross-Over , Difosfatos/administração & dosagem , Difosfatos/química , Feminino , Humanos , Ferro/administração & dosagem , Ferro/química , Adulto Jovem
8.
Macromol Rapid Commun ; 41(5): e1900606, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32003531

RESUMO

Supramolecular chemistry has provided versatile and affordable solutions for the design of tough, flexible polymers. However, application of supramolecular chemistry has been limited to the production of rigid, high-performance polymers due to weak segment mobility. This paper describes a new method of toughening rigid high-performance polymers using the synergistic effect between dual Cu2+ -coordination bonds as a crosslink. These dual Cu2+ -coordination cross-linked high-performance polymers are a class of rigid polymers with an outstanding combination of strength and toughness. The distinct lifetimes and binding strengths of the dual Cu2+ -coordination bonds in a rigid polymer network elicit different dynamic behaviors to improve its energy dissipation and mechanical properties. Moreover, the reformation and removal of Cu2+ -coordination bonds by pyrophosphoric acid endows these cross-linked high-performance polymers with recyclability.


Assuntos
Cobre/química , Polímeros/química , Difosfatos/química , Ligação de Hidrogênio , Teste de Materiais , Reciclagem , Temperatura
9.
J Inorg Biochem ; 203: 110867, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31715376

RESUMO

In this study we applied the dual-responsive chromo-fluorescent Cu2+ chelate 1C for the recognition of miRNA-146a through a pyrophosphate (PPi) sensing strategy in a rolling circle amplification (RCA) process. This approach for the recognition of miRNA-146a was highly robust, selective, and sensitive down to the attomolar (fluorogenic) and sub-micromolar (chromogenic) ranges under modified biochemical conditions at elevated temperature. Probe 1 selectively recognized Cu2+ and PPi ions in a sequential manner, as evidenced by colorless→pink→colorless transitions; the fluorescence emissions centered at 480 nm underwent a corresponding on-off-on sequence in the bluish-green region. We attribute this reversible switching upon the addition of Cu2+/PPi ions to effective chelation-induced ligand-to-metal charge/electron transfer that resulted in opening of the lactam ring upon complexation and closing of the lactam ring upon decomplexation. We also report a label-free approach for monitoring miRNA-146a amplification in an RCA process under modified T4 ligase and ϕ29 buffer conditions, using the Cu2+ ensemble 1C at pH 7.0 (4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid: HEPES, 10 mM MgCl2); the time required to perform this process (40-50 min) was relatively shorter than conventional RCA process. This ensemble 1C could recognize miRNA-146a colorimetrically (from pink to colorless) and fluorimetrically ("turn-on" mode) at concentrations within the highly sensitive atto-/nanomolar range under physiological conditions. This cost-effective label-free sensing strategy appears to be a universal method for detecting miRNAs according to the specified length of the template.


Assuntos
Corantes Fluorescentes/química , Hidrazonas/química , MicroRNAs/análise , Xantenos/química , Colorimetria , Cobre/química , Teoria da Densidade Funcional , Difosfatos/química , Limite de Detecção , Modelos Químicos , Técnicas de Amplificação de Ácido Nucleico , Espectrometria de Fluorescência
10.
Luminescence ; 35(3): 355-364, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31863531

RESUMO

Traditional methods of identifying food-borne pathogens are time consuming and laborious, so innovative methods for their rapid identification must be developed. Testing for bioluminescence pyrophosphate is a convenient and fast method of detecting pathogens without complex equipment. However, the sensitivity of the method is not as high as that of other methods, and it has a very high detection limit. In this study, the method was optimized to improve its sensitivity. The shortcomings of the method were first identified and corrected using dATPαS instead of dATP for the polymerase chain reaction (PCR), therefore reducing the background signal. Also, when the DNA template extracted from the food-borne pathogens was purified, the new bioluminescence pyrophosphate assay had a limit of detection of <10 copy/µl or 10 colony-forming units/ml, and its sensitivity was higher than that of fluorescent real-time quantitative PCR. Moreover, a single copy of a food-borne pathogen could be detected when a single DNA template was included in the PCR. Salmonella was detected in and isolated from 60 samples of broiler chicken, and the accuracy of the results was verified using a culture method (GB 4789.4-2010). These results showed that the new bioluminescence pyrophosphate assay has the advantages of an intuitive detection process, convenient operation, and rapid measurements. Therefore, it can be used for the rapid detection of pathogenic bacteria and probiotics in various fields.


Assuntos
Difosfatos/química , Salmonella typhimurium/isolamento & purificação , DNA Bacteriano/genética , Análise de Alimentos , Microbiologia de Alimentos , Reação em Cadeia da Polimerase , Salmonella typhimurium/genética
11.
Environ Sci Pollut Res Int ; 26(36): 36845-36856, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31745796

RESUMO

This study investigated the impact of adding zeolite (F), superphosphate (G), and ferrous sulfate (L) in various combinations on reducing greenhouse gas (GHG) emission and improving nitrogen conservation during factory-scale chicken manure composting, aimed to identify the combination that optimizes the performance of the process. Chicken manure was mixed with F, G, FL, or FGL and subjected to windrow composting for 46 days. Results showed that global warming potential (GWP) was reduced by 21.9% (F), 22.8% (FL), 36.1% (G), and 39.3% (FGL). Further, the nitrogen content in the final composting product increased by 27.25%, 9.45%, and 21.86% in G, FL, and FGL amendments, respectively. The fertilizer efficiency of the compost product was assessed by measuring the biomass of plants grown in it, and it was consistent with the nitrogen content. N2O emission was negligible during composting, and 98% of the released GHGs comprised CO2 and CH4. Reduction in GHG emission was mainly achieved by reducing CH4 emission. The addition of FL, G, and FGL caused a clear shift in the abundance of dominant methanogens; particularly, the abundance of Methanobrevibacter decreased and that of Methanobacterium and Methanocella increased, which was correlated with CH4 emissions. Meanwhile, the changes in moisture content, NH4+-N content, and pH level also played an important role in the reduction of GHG emission. Based on the effects of nitrogen conservation, fertilizer efficiency improvement, and GHG emission reduction, we conclude that G and FGL are more beneficial than F or FL and suggest these additives for efficient chicken manure composting.


Assuntos
Compostagem , Difosfatos/química , Fertilizantes/análise , Gases de Efeito Estufa/análise , Esterco , Zeolitas/química , Animais , Galinhas , Aquecimento Global , Metano/análise , Nitrogênio/análise , Óxido Nitroso/análise , Solo
12.
Environ Sci Pollut Res Int ; 26(32): 33683-33693, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31595408

RESUMO

Cellulose and lignin belongs to refractory organic matters in the traditional composting. In this research, the degradation of lignocellulose in dairy cattle manure was investigated through adding calcium oxide (CaO) and superphosphate (SSP). In the presence of CaO and SSP, the degradation rate of cellulose and lignin were improved by 25.0% and 8.33%, respectively. The results indicated that the pH value in system would be slightly higher with the addition of CaO and SSP. Besides, the pH value of all cow manure piles were about 8.4 after composting rotten, which could be well neutralized by the gradually acidified soil in the southwest of China with the full effect of fertilizer released. In addition, the abundance of Bacillales, Actinomycetes, and Thermoactinomycetaceae in the experimental groups (AR) was slightly better than that in the control groups (CK) during composting, which led to a conclusion that an elaborate physical-chemical-multivariate aerobic microorganism evolution model of cellulose degradation products (PCMC) was deduced and the physical-chemical-multivariate aerobic microorganism model of lignin cycle degradation (PCML) was developed.


Assuntos
Compostos de Cálcio/química , Compostagem/métodos , Difosfatos/química , Lignina , Esterco/análise , Óxidos/química , Actinobacteria/metabolismo , Animais , Bovinos , Celulose , China , Feminino , Fertilizantes , Concentração de Íons de Hidrogênio , Lignina/metabolismo , Solo
13.
J Am Chem Soc ; 141(45): 18104-18112, 2019 11 13.
Artigo em Inglês | MEDLINE | ID: mdl-31651170

RESUMO

Achieving multiple cycles of RNA replication within a model protocell would be a critical step toward demonstrating a path from prebiotic chemistry to cellular biology. Any model for early life based on an "RNA world" must account for RNA strand cleavage and hydrolysis, which would degrade primitive genetic information and lead to an accumulation of truncated, phosphate-terminated strands. We show here that cleavage of the phosphodiester backbone is not an end point for RNA replication. Instead, 3'-phosphate-terminated RNA strands can participate in template-directed copying reactions with activated ribonucleotide monomers. These reactions form a pyrophosphate linkage, the stability of which we have characterized in the context of RNA copying chemistry. The presence of free magnesium cations results in cleavage of the pyrophosphate bond within minutes. However, we found that the pyrophosphate bond is relatively stable within an RNA duplex and in the presence of chelated magnesium. We show that, under these conditions, pyrophosphate-linked RNA can act as a template for the polymerization of ribonucleotides into canonical 3'-5' phosphodiester-linked RNA. We suggest that primer extension of 3'-phosphate-terminated RNA followed by template-directed copying represents a plausible nonenzymatic pathway for the salvage and recovery of genetic information following strand cleavage.


Assuntos
Difosfatos/química , RNA/química , Meia-Vida , Hidrólise , Cinética , Clivagem do RNA
14.
J Biol Chem ; 294(50): 19269-19278, 2019 12 13.
Artigo em Inglês | MEDLINE | ID: mdl-31662435

RESUMO

Inorganic pyrophosphate (PPi) consists of two phosphate molecules and can act as an energy and phosphate donor in cellular reactions, similar to ATP. Several kinases use PPi as a substrate, and these kinases have recently been suggested to have evolved from ATP-dependent functional homologs, which have significant amino acid sequence similarity to PPi-utilizing enzymes. In contrast, phosphoenolpyruvate carboxykinase (PEPCK) can be divided into three types according to the phosphate donor (ATP, GTP, or PPi), and the amino acid sequence similarity of these PEPCKs is too low to confirm that they share a common ancestor. Here we solved the crystal structure of a PPi-PEPCK homolog from the bacterium Actinomyces israelii at 2.6 Å resolution and compared it with previously reported structures from ATP- and GTP-specific PEPCKs to assess the degrees of similarities and divergences among these PEPCKs. These comparisons revealed that they share a tertiary structure with significant value and that amino acid residues directly contributing to substrate recognition, except for those that recognize purine moieties, are conserved. Furthermore, the order of secondary structural elements between PPi-, ATP-, and GTP-specific PEPCKs was strictly conserved. The structure-based comparisons of the three PEPCK types provide key insights into the structural basis of PPi specificity and suggest that all of these PEPCKs are derived from a common ancestor.


Assuntos
Difosfatos/metabolismo , Fosfoenolpiruvato Carboxilase/metabolismo , Difosfatos/química , Humanos , Modelos Moleculares , Fosfoenolpiruvato Carboxilase/química , Conformação Proteica
15.
Dalton Trans ; 48(39): 14737-14747, 2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31549128

RESUMO

This work illustrates the highly selective fluorescence detection of ATP in the presence of other competing anions, such as AMP, ADP, PPi and other phosphates by using a set of hydroxide-bridged dizinc(ii) complexes offering a cavity lined with hydrogen bonds and other interactive forces. ATP, as a whole, was recognized by the synergic combination of Zn-phosphate bonding, ππ stacking between the adenine ring of ATP and the pyridine ring of the dizinc complex and hydrogen bonding interactions that modulate the cavity structure of the dizinc complexes.


Assuntos
Difosfato de Adenosina/química , Monofosfato de Adenosina/química , Trifosfato de Adenosina/química , Complexos de Coordenação/química , Difosfatos/química , Hidróxidos/química , Zinco/química , Difosfato de Adenosina/isolamento & purificação , Monofosfato de Adenosina/isolamento & purificação , Trifosfato de Adenosina/isolamento & purificação , Cristalografia por Raios X , Difosfatos/isolamento & purificação , Fluorescência , Ligação de Hidrogênio , Modelos Moleculares , Estrutura Molecular
16.
Food Funct ; 10(10): 6568-6581, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31552989

RESUMO

Formation of a gel matrix, involving interactions between proteins, lipids, and water, plays an essential role in the textural properties of processed meats. This study investigated the effects of sodium pyrophosphate (SPP) on the textural properties and oxidative stability of myofibrillar protein (MP)-stabilized emulsion gels under different pH conditions (5.0-9.0). The SPP-modified MP emulsion gels showed an improved elasticity, strength, water-holding capacity, and oxidative stability at pH 6.0 and 7.0. This improvement should be mainly attributed to the enhanced protein-protein crosslinks via ionic interaction between phosphate groups and -NH3+ of amino acids, which were homogeneously formed among adsorbed and/or unadsorbed proteins, entrapping fractions of MPs (myosin heavy chain, actin, and troponin T) within the network. Therefore, the oil droplets were better adherent to the gel matrix. Nevertheless, increased electrostatic repulsion between protein molecules due to excessive phosphates attached to MPs at pH 8.0 and 9.0, as well as protein precipitation at pH 5.0, caused the collapse of the MP-stabilized emulsion gel structure, and thus, overall decreased the gel properties and oxidative stability. LC-MS/MS results confirmed that phosphate groups were successfully introduced to MPs through C-O-P bonds at pH 6.0, and the phosphorylation sites were found to be on serine residues (Ser14, Ser79, Ser96, Ser148, Ser2427, and Ser5272), threonine residues (Thr118 and Thr926), and tyrosine residues (Tyr215 and Tyr425). The results provided a new aspect for better understanding the effect of polyphosphates in meat protein/oil composite systems.


Assuntos
Produtos da Carne/análise , Proteínas Musculares/química , Animais , Galinhas , Difosfatos/química , Emulsões/química , Géis/química , Concentração de Íons de Hidrogênio , Miofibrilas/química , Oxirredução , Fosforilação
17.
Biochemistry ; 58(38): 3971-3979, 2019 09 24.
Artigo em Inglês | MEDLINE | ID: mdl-31512860

RESUMO

RNAs are involved in myriad cellular events. In general, RNA function is affected by cellular conditions. For instance, molecular crowding promotes RNA folding through compaction of the RNA. Metabolites generally destabilize RNA secondary structure, which improves RNA folding cooperativity and increases the fraction of functional RNA. Our recent studies demonstrate that cellular concentrations of amino acid-chelated magnesium (aaCM) stimulate RNA folding and catalysis while protecting RNAs from magnesium ion-induced degradation. However, effects of other cellular magnesium ion chelators on RNA function have not been tested. Herein, we report that nucleotide diphosphate-chelated magnesium, which is of intermediate strength, promotes RNA catalysis much like aaCM. Nucleotides are some of the major metabolites in cells and have one to three phosphates, which have increasingly tight binding of magnesium. On the basis of binding calculations, ∼85% ATP, ∼40% ADP, and only 5% AMP are estimated to possess a magnesium ion under cellular conditions of 0.50 mM Mg2+free. We tested the self-cleaving activity of the hammerhead ribozyme in the presence of these chelated magnesium species. Our results indicate that NTP-chelated magnesium and NMP-chelated magnesium do not appreciably stimulate RNA catalysis, whereas NDP-chelated magnesium promotes RNA catalysis up to 6.5-fold. Inspired by NDP, we observed similar stimulatory effects for several other Mg2+ diphosphate-containing metabolites, including UDP-GlcNAC and UDP-Glc; in addition, we found similar effects for a DNAzyme. Thus, rate stimulatory effects are general with respect to the diphosphate and nucleic acid enzyme. These results implicate magnesium-chelated diphosphate metabolites as general facilitators of RNA function inside cells.


Assuntos
DNA Catalítico/metabolismo , Magnésio/química , Nucleotídeos/metabolismo , RNA Catalítico/metabolismo , RNA/metabolismo , Biocatálise , Cátions Bivalentes/química , Cátions Bivalentes/metabolismo , Quelantes/química , Quelantes/metabolismo , Difosfatos/química , Difosfatos/metabolismo , Ensaios Enzimáticos , Escherichia coli/química , Escherichia coli/enzimologia , Magnésio/metabolismo , Conformação de Ácido Nucleico , Nucleotídeos/química , Dobramento de RNA
18.
Int J Mol Sci ; 20(18)2019 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-31500178

RESUMO

All living things have pyrophosphatases that hydrolyze pyrophosphate and release energy. This energetically favorable reaction drives many energetically unfavorable reactions. An accepted catalytic model of pyrophosphatase shows that a water molecule activated by two divalent cations (M1 and M2) within the catalytic center can attack pyrophosphate in an SN2 mechanism and thus hydrolyze the molecule. However, our co-crystal structure of Acinetobacter baumannii pyrophosphatase with pyrophosphate shows that a water molecule from the solvent may, in fact, be the actual catalytic water. In the co-crystal structure of the wild-type pyrophosphatase with pyrophosphate, the electron density of the catalytic centers of each monomer are different from one another. This indicates that pyrophosphates in the catalytic center are dynamic. Our mass spectroscopy results have identified a highly conserved lysine residue (Lys30) in the catalytic center that is phosphorylated, indicating that the enzyme could form a phosphoryl enzyme intermediate during hydrolysis. Mutation of Lys30 to Arg abolished the activity of the enzyme. In the structure of the apo wild type enzyme, we observed that a Na+ ion is coordinated by residues within a loop proximal to the catalytic center. Therefore, we mutated three key residues within the loop (K143R, P147G, and K149R) and determined Na+ and K+-induced inhibition on their activities. Compared to the wild type enzyme, P147G is most sensitive to these cations, whereas K143R was inactive and K149R showed no change in activity. These data indicate that monovalent cations could play a role in down-regulating pyrophosphatase activity in vivo. Overall, our results reveal new aspects of pyrophosphatase catalysis and could assist in the design of specific inhibitors of Acinetobacter baumannii growth.


Assuntos
Acinetobacter baumannii/enzimologia , Modelos Moleculares , Conformação Proteica , Pirofosfatases/química , Sequência de Aminoácidos , Sítios de Ligação , Catálise , Domínio Catalítico , Difosfatos/química , Difosfatos/metabolismo , Ativação Enzimática , Hidrólise , Peptídeos , Fosforilação , Ligação Proteica , Pirofosfatases/metabolismo , Relação Estrutura-Atividade
19.
Chemosphere ; 237: 124549, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31549661

RESUMO

The addition of organic amendment in soils affected by residual pollution of potentially harmful elements (PHEs) is evaluated. The area was polluted twenty years ago and remediation actions were intensively applied, but evidence of pollution are still detected in some sectors. The amendment application produces significant changes in the main soil properties and modifies the mobility and availability of the pollutants. In general, Cu, Zn, Cd and Pb, showed a significant reduction in soluble and exchangeable forms after the vermicompost addition (percentage of reduction ranging from 59% for soluble Pb to 95% for exchangeable Zn), both in highly (UVS) as in moderately (VS1) polluted soils. This reduction is strongly related to the rise in OC content and pH. Arsenic presented no significant reduction or even an increase in soluble forms in moderately polluted soils (VS1), where the competing effects of OC and phosphorous could be responsible for this increase. Pb also showed an increase in availability after vermicompost application, probably related to the competing effect of Mg2+ coming from the organic amendment. The less mobile forms (those extracted with oxalic-oxalate, pyrophosphate and EDTA), indicate that vermicompost application reduce medium-long term mobility to similar values of those found in less polluted soils (VS2); anyway, an increase in available forms of Pb and As was detected in some cases, indicating a potential risk of toxicity that should be monitored over time.


Assuntos
Compostagem , Recuperação e Remediação Ambiental/métodos , Metais Pesados/análise , Poluentes do Solo/análise , Solo/química , Animais , Carbono , Fracionamento Químico/métodos , Difosfatos/química , Ácido Edético/química , Cavalos , Concentração de Íons de Hidrogênio , Esterco , Metais Pesados/farmacocinética , Poluentes do Solo/farmacocinética , Espanha
20.
J Mater Chem B ; 7(31): 4794-4800, 2019 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-31389965

RESUMO

Alkaline phosphatase (ALP) is extensively used as a clinical biomarker because of its close relevance with a variety of diseases. Thus, exploring reliable and practical methods for ALP analysis is of great significance. In the present work, we explored MIL-53(Fe) as a bifunctional platform with pyrophosphate (PPi)-mediated peroxidase-like activity and oxidation-stimulated fluorescence switching for ALP sensing. The proposed MIL-53(Fe) could exhibit favorable peroxidase-mimicking activity to catalytically decompose H2O2 to hydroxyl radicals, which had strong oxidizing ability to oxidize the terephthalic acid bridging ligand, resulting in the oxidation-stimulated turn-on fluorescence of MIL-53(Fe) itself. Due to the strong coordination interaction between PPi and Fe3+, the former with a relatively large molecular structure was able to inhibit the catalytic activity of MIL-53(Fe) via capping active Fe3+ sites, leading to the suppression of its self-fluorescence response. When ALP was present, it could hydrolyze the PPi inhibitor and restore the dual functions of MIL-53(Fe) to provide fluorescence again. With the above principle, highly sensitive and selective determination of ALP with a linear scope of 2-80 U L-1 and a detection limit down to 0.7 U L-1 was achieved. The MIL-53(Fe) was also demonstrated to be very reliable in measuring the target in human serum, indicating its great promise as an integrated tool for ALP detection in clinical practice.


Assuntos
Fosfatase Alcalina/sangue , Difosfatos/química , Estruturas Metalorgânicas/química , Fosfatase Alcalina/química , Biomarcadores/sangue , Catálise , Colorimetria/métodos , Fluorescência , Humanos , Peróxido de Hidrogênio/química , Limite de Detecção , Oxirredução , Peroxidase/química , Ácidos Ftálicos/química , Espectrometria de Fluorescência/métodos
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