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1.
Mater Sci Eng C Mater Biol Appl ; 104: 109876, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31500007

RESUMO

Nanosilver immobilized on TiO2 nanometric fibers (Ag/TiO2) was produced by solution blow spinning and characterized using scanning electron microscopy, transmission electron microscopy, N2 adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy, water contact angle, and inductively coupled plasma emission spectroscopy analyses. The in vitro antimicrobial and anticancer activities of the produced nanofibers was also investigated. Ag/TiO2 nanofibers revealed a crystalline structure compatible with the rutile crystalline phase, as well as a mesoporous and superhydrophilic nature. XPS profiles showed Ti4+ and Ag0, indicating a strong interaction between the Ag nanoparticles and TiO2. The Ag/TiO2 nanofibers presented antimicrobial activity against Staphylococcus aureus, Enterococcus faecalis, and Escherichia coli. The release of silver ions from 5 mg∙mL-1 and 50 mg∙mL-1 of Ag/TiO2 nanofibers was approximately 0.08 µg∙mL-1 and 0.18 µg∙mL-1, respectively. The nanofiber cytotoxicity in both macrophages (ATCC RAW 264.7) and cancer cells (murine AT-84 oral squamous carcinoma cells) was dose-dependent. A concentration of 5 mg∙mL-1 induced partial suppression growth and migration of cancer cells, while a concentration of 50 mg∙mL-1 resulted in complete inhibition of proliferation and migration of murine AT-84 cells. The overall results indicate that Ag/TiO2 nanofibers can selectively inhibit the cellular mechanism of AT-84 by apoptosis with DNA damage and cell death. The antimicrobial and anticancer performance of Ag/TiO2 nanofibers is probably the result of its nanometric dimension, high surface reactivity, and the interaction between TiO2 and Ag. Electron transfer at the metal-semiconductor interface and reactive oxygen species production, in addition to the biological activity of released silver ions, confirm the potential for use as an agent in antimicrobial and anticancer therapy.


Assuntos
Anti-Infecciosos/química , Antineoplásicos/química , Nanopartículas Metálicas/química , Nanofibras/química , Prata/química , Titânio/química , Anti-Infecciosos/farmacologia , Antineoplásicos/farmacologia , Bactérias/efeitos dos fármacos , Testes de Sensibilidade Microbiana/métodos , Microscopia Eletrônica de Varredura/métodos , Microscopia Eletrônica de Transmissão/métodos , Espectroscopia Fotoeletrônica/métodos , Difração de Raios X/métodos
2.
Anal Bioanal Chem ; 411(12): 2481-2485, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30919014

RESUMO

Spectroscopy, a powerful tool for analyzing material structure and composition, often encounters difficulties when investigating complex systems, such as soil and water. Here, it is hypothesized that bioinformatic methods based on the definition of the operational taxonomic unit can be applied to spectral analysis and to improve the resolving power of spectroscopic approaches. To test this hypothesis, we investigated SOC structure in response to three fertilization regimes using X-ray photoelectron spectroscopy (XPS). The operational taxonomic unit in spectroscopy (OTUsp) was defined and then the Manhattan plots were performed. Our approach turned out to be successful in determining the discrimination of SOC structure, while the traditional peak fitting method of XPS spectra failed. The results were then validated by chemical extraction analysis. Spectral analysis based on OTUsp can supplement traditional spectral interpretation and enhance its usability for studying complex systems. Graphical abstract.


Assuntos
Carbono/análise , Biologia Computacional , Compostos Orgânicos/análise , Espectroscopia Fotoeletrônica/métodos , Solo/química , Fertilizantes , Substâncias Húmicas/análise , Estrutura Molecular , Reprodutibilidade dos Testes
3.
Mater Sci Eng C Mater Biol Appl ; 98: 1179-1195, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30813001

RESUMO

Herein we present our research on generation of silver nanoparticles (AgNPs) on cellulose nanofibers by thermal treatment and DMF as reducing agents. The cellulose (CE) nanofibers were prepared by deacetylation of electrospun cellulose acetate (CA) nanofibers which were subsequently silver coated using AgNO3 followed by thermal and DMF induced reduction processes. The samples were characterized with scanning electron microscopy (SEM), Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and antibacterial assays. Effect of these methods on mechanical properties, thermal stabilities (DTA analysis) and swelling of the CE nanofibers were also studied. Both the processes were effective and efficient in generation of AgNPs on CE nanofibers with higher contents and very good spatial distributions. The XRD, XPS and TEM results evidenced formation metallic AgNPs. TEM images depicted the CE nanofibers highly decorated with spherical AgNPs. The DMF induced process generated AgNPs with comparatively larger sizes. The antibacterial results confirmed excellent antibacterial performance of the CEAgNPs against S. aureus and E. coli. The CEAgNP nanofibers well decorated with AgNPs having good spatial distribution and excellent antibacterial performance suggests CEAgNPs as promising candidate for efficient antimicrobial activities.


Assuntos
Antibacterianos/química , Celulose/química , Nanopartículas Metálicas/química , Nanofibras/química , Prata/química , Antibacterianos/farmacologia , Celulose/análogos & derivados , Escherichia coli/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Microscopia Eletrônica de Varredura/métodos , Microscopia Eletrônica de Transmissão/métodos , Espectroscopia Fotoeletrônica/métodos , Espectrometria por Raios X/métodos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Staphylococcus aureus/efeitos dos fármacos , Difração de Raios X/métodos
4.
Int J Biol Macromol ; 125: 414-422, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30529550

RESUMO

Interaction between split RNA aptamer and the clinically important target, HIV-1 Tat was investigated on a biosensing surface transduced by functionally choreographed multiwall carbon nanotubes (MWCNTs). Acid oxidation was performed to functionalize MWCNTs with carboxyl functional groups. X-ray photoelectron spectroscopy analysis had profound ~2.91% increment in overall oxygen group and ~1% increment was noticed with a specific carboxyl content owing to CO and OCO bonding. The interaction between split RNA aptamer and HIV-1 Tat protein was quantified by electrical measurements with the current signal (Ids) over a gate voltage (Vgs). Initially, 34.4 mV gate voltage shift was observed by the immobilization of aptamer on MWCNT. With aptamer and HIV-1 Tat interaction, the current flow was decreased with the concomitant gate voltage shift of 23.5 mV. The attainment of sensitivity with split aptamer and HIV-1 Tat interaction on the fabricated device was 600 pM. To ensure the genuine interaction of aptamer with HIV-1 Tat, other HIV-1 proteins, Nef and p24 were interacted with aptamer and they displayed the negligible interferences with gate voltage shift of 3.5 mV and 5.7 mV, which shows 4 and 2.5 folds lesser than HIV-1 Tat interaction, respectively.


Assuntos
Aptâmeros de Nucleotídeos/química , Aptâmeros de Nucleotídeos/metabolismo , HIV-1/metabolismo , Nanotubos de Carbono/química , Produtos do Gene tat do Vírus da Imunodeficiência Humana/metabolismo , Técnicas Biossensoriais/métodos , Espectroscopia Fotoeletrônica/métodos , RNA/metabolismo
5.
Proc Natl Acad Sci U S A ; 115(46): 11772-11777, 2018 11 13.
Artigo em Inglês | MEDLINE | ID: mdl-30373827

RESUMO

Fluctuation X-ray scattering (FXS) is an emerging experimental technique in which X-ray solution scattering data are collected from particles in solution using ultrashort X-ray exposures generated by a free-electron laser (FEL). FXS experiments overcome the low data-to-parameter ratios associated with traditional solution scattering measurements by providing several orders of magnitude more information in the final processed data. Here we demonstrate the practical feasibility of FEL-based FXS on a biological multiple-particle system and describe data-processing techniques required to extract robust FXS data and significantly reduce the required number of snapshots needed by introducing an iterative noise-filtering technique. We showcase a successful ab initio electron density reconstruction from such an experiment, studying the Paramecium bursaria Chlorella virus (PBCV-1).


Assuntos
Cristalografia por Raios X/métodos , Espectroscopia Fotoeletrônica/métodos , Chlorella , Cristalografia por Raios X/estatística & dados numéricos , Espectroscopia Fotoeletrônica/estatística & dados numéricos , Radiografia/estatística & dados numéricos , Projetos de Pesquisa , Espalhamento de Radiação , Difração de Raios X , Raios X
6.
J Vis Exp ; (137)2018 07 27.
Artigo em Inglês | MEDLINE | ID: mdl-30102284

RESUMO

Anion photoelectron imaging is a very efficient method for the study of energy states of bound negative ions, neutral species and interactions of unbound electrons with neutral molecules/atoms. State-of-the-art in vacuo anion generation techniques allow application to a broad range of atomic, molecular, and cluster anion systems. These are separated and selected using time-of-flight mass spectrometry. Electrons are removed by linearly polarized photons (photo detachment) using table-top laser sources which provide ready access to excitation energies from the infra-red to the near ultraviolet. Detecting the photoelectrons with a velocity mapped imaging lens and position sensitive detector means that, in principle, every photoelectron reaches the detector and the detection efficiency is uniform for all kinetic energies. Photoelectron spectra extracted from the images via mathematical reconstruction using an inverse Abel transformation reveal details of the anion internal energy state distribution and the resultant neutral energy states. At low electron kinetic energy, typical resolution is sufficient to reveal energy level differences on the order of a few millielectron-volts, i.e., different vibrational levels for molecular species or spin-orbit splitting in atoms. Photoelectron angular distributions extracted from the inverse Abel transformation represent the signatures of the bound electron orbital, allowing more detailed probing of electronic structure. The spectra and angular distributions also encode details of the interactions between the outgoing electron and the residual neutral species subsequent to excitation. The technique is illustrated by the application to an atomic anion (F-), but it can also be applied to the measurement of molecular anion spectroscopy, the study of low lying anion resonances (as an alternative to scattering experiments) and femtosecond (fs) time resolved studies of the dynamic evolution of anions.


Assuntos
Ânions/metabolismo , Espectroscopia Fotoeletrônica/métodos , Humanos
7.
J Vis Exp ; (136)2018 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-30010669

RESUMO

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser (laser-SARPES), and demonstrate a power of this technique for studying solid state physics. Laser-SARPES achieves two great capabilities. Firstly, by examining orbital selection rule of linearly polarized lasers, orbital selective excitation can be carried out in SAPRES experiment. Secondly, the technique can show full information of a variation of the spin quantum axis as a function of the light polarization. To demonstrate the power of the collaboration of these capabilities in laser-SARPES, we apply this technique for the investigations of spin-orbit coupled surface states of Bi2Se3. This technique affords to decompose spin and orbital components from the spin-orbit coupled wavefunctions. Moreover, as a representative advantage of using the direct spin detection collaborated with the polarization-variable laser, the technique unambiguously visualizes the light polarization dependence of the spin quantum axis in three-dimension. Laser-SARPES dramatically increases a capability of photoemission technique.


Assuntos
Lasers/estatística & dados numéricos , Espectroscopia Fotoeletrônica/métodos
8.
J Pharm Biomed Anal ; 159: 119-126, 2018 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-29980013

RESUMO

Lateral flow immunoassay (LFIAs) has found widespread applications in point-of-care testing (POCT). However, conventional LFIAs based on gold nanoparticles can only provide limited information (qualitative or semi-quantitative information) and suffer from low sensitivity. To address this issue, we developed a Fe3O4 nanocrystal cluster-based highly sensitive LFIAs for the simultaneously qualitative and quantitative detection of trace-level biomarkers. The synthesis of poly (acrylic acid)-stabilized superparamagnetic nanocrystal clusters (PAA-MNCs) is a one-pot, simple and convenient technique, and the polyelectrolyte coating provides enough stability, good dispersity and downstream conjugation sites. Using these PAA-MNCs as a label nanomaterial in LFIAs, a model biomarker (amino-terminal pro-B-type natriuretic peptide (NT-proBNP) antibody) was detected qualitatively and quantitatively. The results show that tests have a qualitative detection limit of 100 pg/mL and a quantitative linear relationship between the magnetic signal and antibody concentration (20-8000 pg/mL) under the optimized experimental conditions. The developed LFIA based on PAA-MNCs for NT-proBNP could be used for the clinical assessment of heart failure, offering tremendous potential for personalized medicine.


Assuntos
Resinas Acrílicas/análise , Compostos Férricos/análise , Nanopartículas Metálicas/análise , Espectroscopia Fotoeletrônica/métodos , Biomarcadores/análise , Humanos , Imunoensaio/métodos , Sistemas Automatizados de Assistência Junto ao Leito
9.
Spectrochim Acta A Mol Biomol Spectrosc ; 204: 348-353, 2018 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-29957413

RESUMO

In this study, we evaluated the effect of the Celecoxib (CXB) adsorption on the electronic and optical properties of B12N12 fullerene by using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations with the M06-2X functional and the 6-311+G** basis set. The calculated adsorption energies of CXB with the B12N12 fullerene was evaluated at T = 298.15 K in the vacuum and solvent (water) environments with the M06-2X functional. UV absorption and IR spectra were calculated and studied in order to identify the most important changes happening as a consequence of interactions between CXB and B12N12 fullerene. The results revealed that the adsorption of the CXB molecule from its NH2 head on the B12N12 is more favorable than those of the SO2 and NH groups in the gas and solvent environments. It is anticipated that the applied B12N12 fullerene could be suitable as a biomedical carrier for the delivery of CXB drug.


Assuntos
Celecoxib/química , Fulerenos/química , Espectroscopia Fotoeletrônica/métodos , Adsorção , Celecoxib/análise , Fulerenos/análise , Espectrofotometria Infravermelho/métodos , Vibração
10.
Environ Pollut ; 240: 717-724, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29778057

RESUMO

In this study, the dynamic Cr(VI) removal process from water by the synthesized multilayer material coated nanoscale zerovalent iron (SBC-nZVI) was systematically discussed at different treatment conditions. The results showed that initial pH, contact time, Cr(VI) concentration and the dosage of SBC-nZVI were important parameters that influenced the Cr(VI) removal efficiency. The major Cr(VI) removal occurred within 60 min and gradually tend to equilibrium with consistent treatment. The removal efficiency was highly depended on pH values and the adsorption kinetics agreed well with the pseduo-second-order model (PSO). When the initial Cr(VI) concentration was below 15 mg/L, the removal rate could reach to about 100%. Moreover, the removal efficiency increased with the increase of SBC-nZVI dosage, which related to the increase of reactive sites. To understand the removal mechanism, SBC-nZVI before and after reaction with Cr(VI) were characterized by fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS). These analysis showed that the interaction of SBC-nZVI with Cr(VI) was mainly controlled by reduction and electrostatic attraction. Therefore, these results explained the interaction between Cr(VI) and SBC-nZVI material in detail, and further proved that SBC-nZVI could be an effective material to remove Cr(VI) from water.


Assuntos
Cromo/análise , Recuperação e Remediação Ambiental/métodos , Ferro/química , Poluentes Químicos da Água/análise , Água/química , Adsorção , Cinética , Microscopia Eletrônica de Varredura/métodos , Espectroscopia Fotoeletrônica/métodos , Difração de Raios X/métodos
11.
Int J Biol Macromol ; 116: 255-263, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29746971

RESUMO

In this study, the Cu(II) and Cd(II) ions removal behavior of crosslinked chitosan beads grafted poly(methacrylamide) (abbreviated as crosslinked chitosan-g-PMAm) from single metal ion solutions was investigated. The modified chitosan beads presented a remarkable improvement in acid resistance. The batch experiments demonstrated that pH of solution played a significant role in adsorption. It was found that the adsorption of Cu(II) and Cd(II) were optimum at pH 4 and pH 5, respectively. The maximum adsorption capacities for Cu(II) and Cd(II) based on Langmuir equation were 140.9 mg g-1 and 178.6 mg g-1, respectively. Pseudo-second order gave a better fit for adsorption data with respect to linearity coefficients than pseudo-first order suggesting that chemisorption or electron transfer is the dominant mechanism of the metal ions onto crosslinked chitosan-g-PMAm. In addition, X-ray photoelectron spectroscopy (XPS) investigations revealed that adsorption of both metal ions took place on the surfaces of crosslinked chitosan-g-PMAm by chelation through CNH2, CO and CO groups. Overall, the modified chitosan has proved a promising adsorbent for removal of metal ions.


Assuntos
Cádmio/química , Quitosana/química , Cobre/química , Íons/química , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Espectroscopia Fotoeletrônica/métodos , Poluentes Químicos da Água/química , Purificação da Água/métodos
12.
Pharm Res ; 35(7): 137, 2018 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-29744598

RESUMO

PURPOSE: To evaluate the different degrees of residual structure in the unfolded state of interferon-τ using chemical denaturation as a function of temperature by both urea and guanidinium hydrochloride. METHODS: Asymmetrical flow field-flow fractionation (AF4) using both UV and multi-angle laser light scattering (MALLS). Flow Microscopy. All subvisible particle imaging measurements were made using a FlowCAM flow imaging system. RESULTS: The two different denaturants provided different estimates of the conformational stability of the protein when extrapolated back to zero denaturant concentration. This suggests that urea and guanidinium hydrochloride (GnHCl) produce different degrees of residual structure in the unfolded state of interferon-τ. The differences were most pronounced at low temperature, suggesting that the residual structure in the denatured state is progressively lost when samples are heated above 25°C. The extent of expansion in the unfolded states was estimated from the m-values and was also measured using AF4. In contrast, the overall size of interferon-τ was determined by AF4 to decrease in the presence of histidine, which is known to bind to the native state, thereby providing conformational stabilization. Addition of histidine as the buffer resulted in formation of fewer subvisible particles over time at 50°C. Finally, the thermal aggregation was monitored using AF4 and the rate constants were found to be comparable to those determined previously by SEC and DLS. The thermal aggregation appears to be consistent with a nucleation-dependent mechanism with a critical nucleus size of 4 ± 1. CONCLUSION: Chemical denaturation of interferon-τ by urea or GnHCl produces differing amounts of residual structure in the denatured state, leading to differing estimates of conformational stability. AF4 was used to determine changes in size, both upon ligand binding as well as upon denaturation with GnHCl. Histidine appears to be the preferred buffer for interferon-τ, as shown by slower formation of soluble aggregates and reduced levels of subvisible particles when heated at 50°C.


Assuntos
Interferon Tipo I/química , Proteínas da Gravidez/química , Agregados Proteicos , Desnaturação Proteica , Desdobramento de Proteína , Água/química , Interferon Tipo I/análise , Interferon Tipo I/metabolismo , Soluções Farmacêuticas/química , Soluções Farmacêuticas/metabolismo , Espectroscopia Fotoeletrônica/métodos , Proteínas da Gravidez/análise , Proteínas da Gravidez/metabolismo , Agregados Proteicos/fisiologia , Água/metabolismo
13.
Spectrochim Acta A Mol Biomol Spectrosc ; 199: 349-355, 2018 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-29635179

RESUMO

DNA nucleotides are used as a molecular recognition system on electrodes modified to be applied in the detection of various diseases, but immobilization mechanisms, as well as, charge transfers are not satisfactorily described in the literature. An electrochemical and spectroscopic study was carried out to characterize the molecular groups involved in the direct immobilization of DNA structures on the surface of nanostructured TiO2 with the aim of evaluating the influence of the geometrical aspects. X-ray photoelectron spectroscopy at O1s and P2p core levels indicate that immobilization of DNA samples occurs through covalent (POTi) bonds. X-ray absorption spectra at the Ti2p edge reinforce this conclusion. A new species at 138.5eV was reported from P2p XPS spectra analysis which plays an important role in DNA-TiO2 immobilization. The POTi/OTi ratio showed that quantitatively the DNA immobilization mechanism is dependent on their geometry, becoming more efficient for plasmid ds-DNA structures than for PCR ds-DNA structures. The analysis of photoabsorption spectra at C1s edge revealed that the molecular groups that participate in the C1s→LUMO electronic transitions have different pathways in the charge transfer processes at the DNA-TiO2 interface. Our results may contribute to additional studies of immobilization mechanisms understanding the influence of the geometry of different DNA molecules on nanostructured semiconductor and possible impact to the charge transfer processes with application in biosensors or aptamers.


Assuntos
Técnicas Biossensoriais/métodos , Eletrodos , Ácidos Nucleicos Imobilizados/química , Espectroscopia Fotoeletrônica/métodos , Titânio/química
14.
Mol Biol Rep ; 45(4): 403-411, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29626318

RESUMO

Spatially confined environments are seen in biological systems and in the fields of biotechnology and nanotechnology. The confinement restricts the conformational space of polymeric molecules and increasing the degree of molecular crowding. Here, we developed preparation methods for agarose and polyacrylamide gels applicable to UV spectroscopy that can evaluate the confinement effects on DNA and protein structures. Measurements of UV absorbance and CD spectra showed no significant effect of the confinement in the porous media of agarose gels on the base-pair stability of DNA polynucleotides [poly(dA)/poly(dT)] and oligonucleotides (hairpin, duplex, and triplex structures). On the other hand, a highly confined environment created by polyacrylamide gels at high concentrations increased the stability of polynucleotides while leaving that of oligonucleotides unaffected. The changes in the base-pair stability of the polynucleotides were accompanied by the perturbation of the helical conformation. The polyacrylamide gels prepared in this study were also used for the studies on proteins (lysozyme, bovine serum albumin, and myoglobin). The effects on the proteins were different from the effects on DNA structures, suggesting different nature of interactions within the gel. The experimental methods and results are useful to understand the physical properties of nucleic acids and proteins under confined conditions.


Assuntos
DNA/química , Hidrogéis/química , Espectroscopia Fotoeletrônica/métodos , Resinas Acrílicas , Pareamento de Bases , Hidrogéis/farmacologia , Conformação de Ácido Nucleico , Oligonucleotídeos/química , Polinucleotídeos/química , Conformação Proteica , Proteínas/química , Sefarose
15.
Mol Pharm ; 15(5): 2045-2053, 2018 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-29641898

RESUMO

Surface composition critically impacts stability (e.g., crystallization) and performance (e.g., dissolution) of spray dried amorphous solid dispersion (ASD) formulations; however, traditional characterization techniques such as Raman and infrared spectroscopies may not provide useful information on surface composition on the spray dried ASD particles due to low spatial resolution, high probing depth, and lack of quantitative information. This study presents an advanced surface characterization platform consisting of two complementary techniques: X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Such a platform enables qualitative and quantitative measurements of surface composition for the fine spray dried ASD particles with ultrasurface-sensitivity (less than 10 nm from the surface) and superior spatial resolution (approximately 250 nm for ToF-SIMS). Both XPS and ToF-SIMS demonstrated that the polymer (PVPVA) was dominantly enriched on the surface of our spray dried naproxen-PVPVA ASD particles. Of a particular note was that XPS could differentiate two batches of spray dried ASD particles with a subtle difference in surface composition produced by varying feed solution solvents. This advanced surface characterization platform will provide essential surface information to understand the mechanisms underlying the impact of surface composition on stability (e.g., crystallization) and functionality (e.g., dissolution) in future studies.


Assuntos
Naproxeno/química , Química Farmacêutica/métodos , Estabilidade de Medicamentos , Espectrometria de Massas/métodos , Espectroscopia Fotoeletrônica/métodos , Polímeros/química , Povidona/análogos & derivados , Povidona/química , Solubilidade/efeitos dos fármacos , Solventes/química , Propriedades de Superfície
16.
Talanta ; 182: 536-543, 2018 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-29501189

RESUMO

The identification of microorganisms is very important in different fields and alternative methods are necessary for a rapid and simple identification. The use of fatty acids for bacterial identification is gaining attention as phenotypic characteristics are reflective of the genotype and are more easily analyzed. In this work, gas chromatography-vacuum ultraviolet spectroscopy (GC-VUV) was used to determine bacteria fatty acid methyl esters (FAMEs), to identify and discriminate different environmental bacteria based on their fatty acid profile. Microorganisms were grown in agar and their fatty acids extracted, saponified, and esterified before analysis. Unique FAME profiles were obtained for each microorganism mainly composed of branched, cyclopropane, hydroxy, saturated, and unsaturated fatty acid methyl esters. S. maltophilia showed a higher diversity of fatty acids while Bacillus species showed higher complexity in terms of branched-chain FAMEs, with several iso and anteiso forms. 12 different bacteria genera and 15 species were successfully differentiated based on their fatty acid profiles after performing PCA and cluster analysis. Some difficult to differentiate species, such as Bacillus sp., which are genetically very similar, were differentiated with the developed method.


Assuntos
Bactérias/isolamento & purificação , Cromatografia Gasosa/métodos , Ácidos Graxos/isolamento & purificação , Água Subterrânea/microbiologia , Espectroscopia Fotoeletrônica/métodos , Aeromonadaceae/classificação , Aeromonadaceae/isolamento & purificação , Aeromonadaceae/metabolismo , Alcaligenaceae/classificação , Alcaligenaceae/isolamento & purificação , Alcaligenaceae/metabolismo , Bacillaceae/classificação , Bacillaceae/isolamento & purificação , Bacillaceae/metabolismo , Bactérias/classificação , Bactérias/metabolismo , Análise por Conglomerados , Comamonadaceae/classificação , Comamonadaceae/isolamento & purificação , Comamonadaceae/metabolismo , Enterobacteriaceae/classificação , Enterobacteriaceae/isolamento & purificação , Enterobacteriaceae/metabolismo , Ésteres , Ácidos Graxos/química , Ácidos Graxos/classificação , Moraxellaceae/classificação , Moraxellaceae/isolamento & purificação , Moraxellaceae/metabolismo , Análise de Componente Principal , Pseudomonadaceae/classificação , Pseudomonadaceae/isolamento & purificação , Pseudomonadaceae/metabolismo , Vácuo , Microbiologia da Água , Xanthomonadaceae/classificação , Xanthomonadaceae/isolamento & purificação , Xanthomonadaceae/metabolismo
17.
Chemosphere ; 201: 708-715, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29547859

RESUMO

Characterization of dissolved organic matter/nitrogen (DOM/DON) is critical in water quality assessment and nutrient management in watershed or ecosystem. This study was to investigate the link between DOM/DON and its source using fluorescence excitation-emission matrix (EEM) spectroscopy coupled with parallel factor analysis (PARAFAC). Water samples were collected from various aquatic systems in a watershed located in central Missouri, including rural watershed with various land use and land cover (LULC), landfill, and constructed wetland. PARAFAC results based on EEM spectroscopy revealed four DOM components: two humic/fulvic acid-like components, one xenobioic-like component, and one protein-like component (f4). The f4 score was found highly correlated to LULC, indicating its distinctive EEM structure in relation to source. It is believed that the f4 score could be used as a surrogate for DOM/DON source-tracking in complex ecosystems. The nitrogen 1s X-ray photoelectron spectroscopy (XPS) of the solid DOM showed a close relationship between N oxidation state and its origin. The classification of the sample origins by the N oxidation state confirmed the grouping by the f4 score of EEM/PARAFAC. This study demonstrated that EEM/PARAFAC could be used as a tool for DOM/DON source tracking, point or non-point source pollution control, and understanding of DOM/DON fate and transport in complex aquatic ecosystems.


Assuntos
Monitoramento Ambiental/métodos , Substâncias Húmicas/análise , Nitrogênio/análise , Rios/química , Poluentes Químicos da Água/análise , Áreas Alagadas , Ecossistema , Análise Fatorial , Missouri , Espectroscopia Fotoeletrônica/métodos , Espectrometria de Fluorescência/métodos , Qualidade da Água
18.
Molecules ; 23(1)2017 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-29267245

RESUMO

Pre-shaped mesoporous amorphous rice husk ash (RHA) and MCM-41 derived from RHA as a silica source were transformed into MFI-type zeolites using two different structure-directing agents. Tetrapropylammonium hydroxide (TPAOH) was utilized as an alkali source for silica dissolution and structure control during the direct transformation of RHA into zeolite. A monopropylamine (PA)-containing alkaline solution (NaOH) was used for the pseudomorphic transformation of RHA or MCM-41 into zeolite. The hydrothermal conversion of RHA or MCM-41 into MFI-type zeolites was investigated as a function of reaction time at 175 °C. With PA as template, the crystallization took place inside and on the outer surface of RHA or MCM-41 without losing the original shape of the initial silica sources, while TPAOH led to the formation of conventional MFI-type zeolite crystals due to the complete dissolution of RHA. The final products were characterized by X-ray diffraction, nitrogen adsorption, scanning electron microscopy, and optical emission spectroscopy.


Assuntos
Cristalização/métodos , Oryza/química , Dióxido de Silício/síntese química , Zeolitas/síntese química , Adsorção , Microscopia Eletrônica de Varredura/métodos , Nitrogênio/química , Espectroscopia Fotoeletrônica/métodos , Porosidade , Propriedades de Superfície , Temperatura Ambiente , Difração de Raios X/métodos
19.
Sci Rep ; 7(1): 17728, 2017 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-29255234

RESUMO

A submerged dielectric barrier discharge (DBD) plasma reactor was used to inactivate artificially inoculated reference strains of Salmonella Typhimurium ATCC 14028 on sliced onion (3 cm × 3 cm). Salmonella Typhimurium reductions obtained after 10 min of treatment were 3.96 log CFU/slice and 1.64 log CFU/slice for clean dry air and N2 feed gas, respectively. Variations observed in Optical Emission Spectra (OES) for different feed gases are responsible for the inactivation level variations of Salmonella Typhimurium. The physiochemical properties of the onion slices, such as quercetin content, ascorbic acid content and color parameters, were monitored before and after treatment and the changes that occurred were measured to be in the acceptable range. Quercetin content was reduced only 3.74-5.07% for 10 min treatment, higher reduction was obtained for the use of clean dry air than that of N2 feed gas. Ascorbic acid loss was measured to be 11.82% and 7.98% for a 10 min treatment with clean dry air and N2 feed gas, respectively. The color parameters did not show significant changes upon treatment (p > 0.05) of the same duration for the uses of different feed gases.


Assuntos
Manipulação de Alimentos/métodos , Cebolas/microbiologia , Salmonella typhimurium/efeitos dos fármacos , Contagem de Colônia Microbiana/métodos , Contaminação de Alimentos/análise , Microbiologia de Alimentos/métodos , Conservação de Alimentos/métodos , Gases/química , Cebolas/metabolismo , Espectroscopia Fotoeletrônica/métodos , Gases em Plasma/química , Quercetina/análise , Salmonella typhimurium/patogenicidade
20.
Biomacromolecules ; 18(12): 3978-3991, 2017 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-29131607

RESUMO

In this work, carbon papers and aerogels based on graphene layers and chitosan were prepared. They were obtained by mixing chitosan (CS) and a high surface area nanosized graphite (HSAG) in water in the presence of acetic acid. HSAG/CS water dispersions were stable for months. High resolution transmission electron microscopy revealed the presence of few graphene layers in water suspensions. Casting or lyophilization of such suspensions led to the preparation of carbon paper and aerogel, respectively. In X-ray spectra of both aerogels and carbon paper, peaks due to regular stacks of graphene layers were not detected: graphene with unaltered sp2 structure was obtained directly from graphite without the use of any chemical reaction. The composites were demonstrated to be electrically conductive thanks to the graphene. Chitosan thus makes it possible to obtain monolithic carbon aerogels and flexible and free-standing graphene papers directly from a nanosized graphite by avoiding oxidation to graphite oxide and successive reduction. Strong interaction between polycationic chitosan and the aromatic substrate appears to be at the origin of the stability of HSAG/CS adducts. Cation-π interaction is hypothesized, also on the basis of X-ray photoelectron spectroscopy findings. This work paves the way for the easy large-scale preparation of carbon papers through a method that has a low environmental impact and is based on a biosourced polymer, graphene, and water.


Assuntos
Carbono/química , Quitosana/química , Grafite/química , Acetatos/química , Liofilização/métodos , Microscopia Eletrônica de Varredura/métodos , Microscopia Eletrônica de Transmissão/métodos , Nanocompostos/química , Oxirredução , Óxidos/química , Papel , Tamanho da Partícula , Espectroscopia Fotoeletrônica/métodos , Polímeros/química , Água/química
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