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1.
Chem Commun (Camb) ; 55(86): 12920-12923, 2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31608905

RESUMO

We report the direct observation of equilibrium folding-unfolding dynamics of a mechanically labile, three helix bundle protein GA using a commercial atomic force microscope (AFM). Our study extends the capability of commercial AFMs towards studying protein unfolding/refolding at equilibrium as well as increasingly complex biomolecular systems in the context of biological function.


Assuntos
Proteínas de Bactérias/química , Microscopia de Força Atômica , Conformação Proteica em alfa-Hélice , Domínios Proteicos , Dobramento de Proteína , Desdobramento de Proteína
2.
Braz Oral Res ; 33(suppl 1): e065, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31576949

RESUMO

Additive manufacturing (AM) is an emerging process for biomaterials and medical devices. Direct Laser Metal Sintering (DLMS) is an AM technique used to fabricate Ti-6Al-4V implant materials with enhanced surface-related properties compared with wrought samples; thus, this technique could influence microbial adsorption and colonization. Therefore, this in vitro study was conducted to evaluate the impact of different implant production processes on microbial adhesion of periodontal pathogens. Titanium discs produced using two different processes-conventional and AM-were divided into three groups: conventional titanium discs with machined surface (G1), AM titanium discs with chemical treatment (G2) and AM titanium discs without chemical treatment (G3). Subgingival biofilm composed of 32 species was formed on the titanium discs, and positioned vertically in 96-well plates, for 7 days. The proportions of microbial complexes and the microbial profiles were analyzed using a DNA-DNA hybridization technique, and data were evaluated using Kruskal-Wallis and Dunnett tests (p < 0.05). Lower proportions of the red complex species were observed in the biofilm formed in G2 compared with that in G1 (p < 0.05). Moreover, the proportions of the microbial complexes were similar between G2 and G3 (p > 0.05). Compared with G1, G2 showed reduced levels of Porphyromonas gingvalis , Actinomyces gerencseriae, and Streptococcus intermedius , and increased levels of Parvimonas micra , Actinomyces odontolyticus, and Eikenella corrodens (p < 0.05). The microbial profile of G3 did not differ from G1 and G2 (p > 0.05). The results of this in vitro study showed that titanium discs produced via AM could alter the microbial profile of the biofilm formed around them. Further clinical studies should be conducted to confirm these findings.


Assuntos
Biofilmes/crescimento & desenvolvimento , Titânio/química , Titânio/farmacologia , Análise de Variância , Bactérias/efeitos dos fármacos , Biofilmes/efeitos dos fármacos , Sondas de DNA , Microscopia de Força Atômica , Microscopia Eletrônica de Varredura , Espectroscopia Fotoeletrônica , Valores de Referência , Reprodutibilidade dos Testes , Estatísticas não Paramétricas , Propriedades de Superfície , Fatores de Tempo
3.
Chem Biol Interact ; 313: 108821, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31525342

RESUMO

Decrease in the bioavailability of vasoactive nitric oxide (NO), derived from the endothelial nitric oxide synthase (NOS3), underlines vascular endothelial damage. Our expanding knowledge on mature red blood cells (RBCs) makes it supposable that RBCs might contribute to vascular function and integrity via their active NO synthetizing system (RBC-NOS3). This "rescue" mechanism of RBCs could be especially important during pregnancy with smoking habit, when smoking acts as an additional stressor and causes active change in the redox status. In this study RBC populations of 82 non-smoking (RBC-NS) and 75 smoking (RBC-S) pregnant women were examined. Morphological variants were followed by confocal microscopy and quantified by a microscopy based intelligent analysis software. Fluorescence activated cell sorting was used to examine the translational and posttranslational regulation of RBC-NOS, Arginase-1 and the formation of the major product of lipid peroxidation, 4-hydroxy-2-nonenal. To survey the rheological parameters of RBCs like elasticity and plasticity atomic force microscopy-based measurement was applied. Significant morphological and functional differences of RBCs were found between the non-smoking and smoking groups. The phenotypic variations in RBC-S population, even the characteristic biconcave disc-shaped cells, could be connected to impaired NOS3 activation and are compromised in their physiological properties. Membrane lipid studies reveal an elevated lipid oxidation state well paralleled with the changed elastic and plastic activities. These features can form a basic tool in the prenatal health screening conditions; hence the compensatory mechanism of RBC-S population completely fails to sense and rescue the acute oxidative stress conditions.


Assuntos
Arginase/metabolismo , Eritrócitos/metabolismo , Óxido Nítrico Sintase Tipo III/metabolismo , Óxido Nítrico/metabolismo , Fumar/efeitos adversos , Adulto , Aldeídos/metabolismo , Estudos de Casos e Controles , Morte Celular/efeitos dos fármacos , Eritrócitos/efeitos dos fármacos , Feminino , Humanos , Peroxidação de Lipídeos/efeitos dos fármacos , Microscopia de Força Atômica , Gravidez
4.
BMC Bioinformatics ; 20(1): 465, 2019 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-31500563

RESUMO

BACKGROUND: Atomic force microscopy (AFM) allows the mechanical characterization of single cells and live tissue by quantifying force-distance (FD) data in nano-indentation experiments. One of the main problems when dealing with biological tissue is the fact that the measured FD curves can be disturbed. These disturbances are caused, for instance, by passive cell movement, adhesive forces between the AFM probe and the cell, or insufficient attachment of the tissue to the supporting cover slide. In practice, the resulting artifacts are easily spotted by an experimenter who then manually sorts out curves before proceeding with data evaluation. However, this manual sorting step becomes increasingly cumbersome for studies that involve numerous measurements or for quantitative imaging based on FD maps. RESULTS: We introduce the Python package nanite, which automates all basic aspects of FD data analysis, including data import, tip-sample separation, base line correction, contact point retrieval, and model fitting. In addition, nanite enables the automation of the sorting step using supervised learning. This learning approach relates subjective ratings to predefined features extracted from FD curves. For ratings ranging from 0 to 10, our approach achieves a mean squared error below 1.0 rating points and a classification accuracy between good and poor curves that is above 87%. We showcase our approach by quantifying Young's moduli of the zebrafish spinal cord at different classification thresholds and by introducing data quality as a new dimension for quantitative AFM image analysis. CONCLUSION: The addition of quality-based sorting using supervised learning enables a fully automated and reproducible FD data analysis pipeline for biological samples in AFM.


Assuntos
Confiabilidade dos Dados , Aprendizado de Máquina , Microscopia de Força Atômica , Software , Animais , Automação , Nanotecnologia , Peixe-Zebra
5.
J Agric Food Chem ; 67(35): 9907-9915, 2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31436102

RESUMO

The impact of covalent or non-covalent bound gallic acid (GA) on the formation, physicochemical properties, and digestion of ovotransferrin (OTF) nanofibrils was comprehensively studied. Thioflavin T fluorescence results revealed that bound GA could inhibit OTF nanofibrillation and that the fibril-inhibitory activity of bound GA was dose dependent. Covalent bound GA exerted stronger inhibition on OTF nanofibrillation than an equal amount of non-covalent bound GA. Atomic force microscopy revealed that covalent bound GA shortened OTF nanofibrils significantly, while non-covalent bound GA did not change the contour length of OTF fibrils remarkably. Bound GA altered diameter of OTF nanofibrils. Both covalent and non-covalent bound GA could alter the zeta potential, surface hydrophobicity, and rheological properties of OTF nanofibrils. Bound GA endowed OTF nanofibrils with a strong antioxidant activity. In vitro gastrointestinal digestion results showed that covalent bound GA elevated the fibril digestion rate better than non-covalent bound GA. Polyphenol binding provided a new approach to modulating the physicochemical properties of protein nanofibrils.


Assuntos
Conalbumina/química , Ácido Gálico/química , Nanofibras/química , Animais , Antioxidantes/química , Antioxidantes/metabolismo , Galinhas , Conalbumina/metabolismo , Digestão , Ácido Gálico/metabolismo , Interações Hidrofóbicas e Hidrofílicas , Microscopia de Força Atômica , Modelos Biológicos , Reologia
6.
J Agric Food Chem ; 67(37): 10470-10480, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31469565

RESUMO

Foodborne nanoparticles (FNPs) produced by roasting have attracted the attention of people, owing to their safety risk to body health. Herein, we reported the formation, physicochemical properties, elemental composition, biodistribution, and binding with human serum albumin (HSA) of FNPs extracted from roast squid. The results showed that the FNP size gradually decreased from 4.1 to 2.3 nm as the roasting temperature changed from 190 to 250 °C. The main component elements of FNPs are carbon, oxygen, and nitrogen, and the carbon and nitrogen contents of FNPs increased with the roasting temperature rising. The surface of FNPs contained hydroxyl, amino, and carboxyl functional groups. The FNPs can emit fluorescence in ultraviolet light and show excitation-dependent emission behavior. Furthermore, it was found that the FNPs derived from roast squid could be accumulated in the stomach, intestine, and brain of BALB/c mice after oral feeding. Static fluorescence quenching of HSA was found by the Stern-Volmer equation and ultraviolet-visible spectrum analysis after interaction with the FNPs. After the addition of FNPs, the α-helix content of HSA decreased and the morphological height of HSA increased, which indicated that the FNPs could cause structural changes in HSA. The atomic force microscopy characterization showed the formation of nanocorona between FNPs and HSA.


Assuntos
Decapodiformes/química , Nanopartículas/química , Nanopartículas/metabolismo , Albumina Sérica Humana/química , Animais , Culinária , Decapodiformes/metabolismo , Fluorescência , Temperatura Alta , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Microscopia de Força Atômica , Tamanho da Partícula , Ligação Proteica , Conformação Proteica , Albumina Sérica Humana/metabolismo , Distribuição Tecidual
7.
Chem Commun (Camb) ; 55(70): 10444-10447, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31410430

RESUMO

A new series of 2D catalytic materials whose inorganic surfaces are fully covered with pre-designed "promoter" groups are reported. One of them showed excellent biomimetic catalytic activity and provided the lowest detection limit to glucose among the reported 2D materials and their composite materials.


Assuntos
Biomimética , Calcogênios/química , Metais/química , Catálise , Limite de Detecção , Microscopia de Força Atômica , Microscopia Eletrônica de Transmissão , Espectroscopia Fotoeletrônica , Difração de Pó
8.
Chem Commun (Camb) ; 55(70): 10484-10487, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31414101

RESUMO

The de novo design of stapled peptide-based self-assemblies attracts vast interest, yet still remains challenging. The development of an oxidation trigger for peptide stapling and subsequent self-assembly is described here. A self-assembling sequence, Fmoc-R(RCEX)2-NH2, transformed from a random coil to an α-helical structure upon disulphide bonding of the flanking cysteine residues positioning at the i/i + 4 locations. The stapling form of this peptide enforces a conformational restraint that affords the driving force for self-assembly into nanorod/nanovesicle structures. Moreover, these assembled materials can transport siRNA into cancer cells and immediately release the cargo in a reductive environment.


Assuntos
Peptídeos/química , Microscopia de Força Atômica , Oxirredução , Conformação Proteica em alfa-Hélice
9.
J Photochem Photobiol B ; 197: 111555, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31326844

RESUMO

A series of heterocyclic donor-acceptor systems were synthesized and well characterized by using 1H, 13C NMR, FT-IR, and elemental analysis. They were designed to investigate the effect of thiophene and cyanoacrylic acid number units on the thermal, optical, electrochemical and finally photovoltaic properties of dye-sensitized solar cells prepared with the selected compounds. The effect of chemical structure on their properties was demonstrated. They showed the beginning of thermal decomposition between 230 and 270 °C. The compounds absorbed the radiation in the range of 300-500 nm or 200-400 nm. They were electrochemically active and varied in energy band gap from 3.40 to 1.58 eV. Additionally, their optimized geometry, HOMO-LUMO levels, ionization potential, and electron affinity were evaluated using density functional theory. The photovoltaic devices based on TiO2 sensitized with the obtained molecules exhibited low power conversion efficiency, which was the highest for the device containing the symmetrical molecule with bithiophene structure. Under co-sensitization, the cell made of the same compound gave significant enhancement of efficiency of 6.3% being higher to that of the individual device prepared from dye N719 (5.75%). Moreover, the effects of immersion time of TiO2 electrode in the dye solution and co-sensitization methods were tested. The surface morphology of photoanode was investigated using atomic force microscopy.


Assuntos
Corantes/química , Cianoacrilatos/química , Energia Solar , Cianoacrilatos/síntese química , Teoria da Densidade Funcional , Fontes de Energia Elétrica , Microscopia de Força Atômica , Oxirredução , Titânio/química
10.
J Chem Phys ; 151(1): 014901, 2019 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-31272182

RESUMO

The elasticity of dsDNA molecules is investigated by Monte Carlo simulations based on a coarse-grained model of DNA. The force-displacement (f-r) curves are computed under the constraints of the constant force (Gibbs) or the constant length (Helmholtz) ensemble. Particular attention was paid to the compressional (negative) and weak tensile forces. It was confirmed that simulations using the vector Gibbs ensemble fail to represent the compression behavior of polymers. Simulations using the scalar Gibbs protocol resulted in a qualitatively correct compressional response of DNA provided that the quadratic averages of displacements were employed. Furthermore, a well-known shortcoming of the popular Marko-Siggia relation for DNA elasticity at weak tensile forces is elucidated. Conversely, the function f-r from the simulation at the constant length constraint, as well as the new closed-form expressions, provides a realistic depiction of the DNA elasticity over the wide range of negative and positive forces. Merely a qualitative resemblance of the compression functions f-r predicted by the employed approaches supports the notion that the elastic response of DNA molecules may be greatly affected by the specifics of the experimental setups and the kind of averaging of the measured variable.


Assuntos
DNA/química , Microscopia de Força Atômica , Método de Monte Carlo , Pinças Ópticas
11.
Phys Chem Chem Phys ; 21(28): 15787-15797, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31282520

RESUMO

With the aim of improving the reproducibility of capacitive immunosensors, we performed a comparative study of four different insulating/immobilization chemistries. Each chemistry targeted different areas of an interdigitated electrode including an alkyl thiol monolayer on the electrode surface, an amino silane monolayer on the gaps between electrodes, and conformal coatings via passive adsorption of the probe and a spin-coated layer of poly(methyl methacrylate) (PMMA). We analyzed the dielectric properties of these chemistries by comparing their capacitive behavior through equivalent circuit modeling and correlate the observed behavior with their surface characteristics by using atomic force microscopy and finite element modeling. We found that surface binding events occurring in the interdigitated electrode gaps play a major role in the overall change in capacitance. This was confirmed via finite element modeling showing an increased electric field intensity in the electrode gaps by 14%, compared to directly above the electrodes. Among the investigated surface chemistries, PMMA conformal coating produced a smooth surface (Rq roughness = 0.21 ± 0.02 nm) providing the most reproducible and stable capacitance change (15.6 ± 0.4%) in response to specific antigen-antibody binding.


Assuntos
Técnicas Biossensoriais/instrumentação , Eletrodos , Imunoensaio/instrumentação , Capacitância Elétrica , Microscopia de Força Atômica , Modelos Químicos , Ligação Proteica
12.
J Chromatogr A ; 1603: 361-370, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31257038

RESUMO

Separation efficiency is ideally controlled by molecular diffusion in capillary electrophoresis (CE). However, other adverse phenomena, such as solute adsorption on capillary surface, tend to increase the peak dispersion. An interesting alternative to limit the solute adsorption is to avoid as much as possible the contact of the solute with the capillary surface by elaborating superhydrophobic (SH) coatings on fused silica capillary surfaces. This work describes an optimized protocol to get non-wettable SH coating using hydrophobically modified silica nanoparticle suspensions (Glaco™), based on simple capillary flushes and thermal stabilization. In this protocol, the control of the air flushing after the introduction of the Glaco™ suspension in the capillary was found crucial to get optimized coating coverage and reproducibility. The SH coating was characterized by ellipsometry, atomic force microscopy, scanning electron microscopy, contact angle (about 159°) and the observation of the meniscus of water in the coated capillary. The hydrodynamic behavior of the SH coated capillary was investigated by plotting the Poiseuille law. Finally, electrophoretic separations of a peptide mixture in acidic conditions demonstrated the interest of this approach with an increase by a factor 2 of the separation efficiency compared to fused silica capillary.


Assuntos
Eletroforese Capilar/métodos , Interações Hidrofóbicas e Hidrofílicas , Adsorção , Vidro/química , Hidrodinâmica , Microscopia de Força Atômica , Peptídeos/análise , Reprodutibilidade dos Testes
13.
Adv Exp Med Biol ; 1140: 159-179, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31317500

RESUMO

Atomic force microscopy employs a nanometric tip located at the end of a micro-cantilever to probe surface-mounted samples at nanometer resolution. Because the technique can also work in a liquid environment it offers unique possibilities to study individual viruses under conditions that mimic their natural milieu. Here, we review how AFM imaging can be used to study the surface structure of viruses including that of viruses lacking a well-defined symmetry. Beyond imaging, AFM enables the manipulation of single viruses by force spectroscopy experiments. Pulling experiments can provide information about the early events of virus-host interaction between the viral fibers and the cell membrane receptors. Pushing experiments measure the mechanical response of the viral capsid and its contents and can be used to show how virus maturation and exposure to different pH values change the mechanical response of the viruses and the interaction between the capsid and genome. Finally, we discuss how studying capsid rupture and self-healing events offers insight in virus uncoating pathways.


Assuntos
Microscopia de Força Atômica , Vírus , Capsídeo/química , Capsídeo/ultraestrutura , Proteínas do Capsídeo/química , Proteínas do Capsídeo/ultraestrutura , Vírus/ultraestrutura
14.
Food Chem ; 297: 125021, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31253338

RESUMO

In this study, the effects of ultrasonic intensity on conformational changes in aqueous citrus pectin solution under ultrasonic processing and its possible transition mechanism were investigated. The results demonstrated that higher ultrasonic intensity (104.7 W/cm2) caused larger alterations in the molecular and conformational parameters of the semiflexible pectin (Mark-Houwink relation exponent a: 0.820, conformational parameter α: 0.607, structural parameter ρ: 2.22) in aqueous solution. Meanwhile, the semiflexible chain of pectin became more flexible (a: 0.804, α: 0.601, ρ: 1.75) at higher ultrasonic intensity in aqueous solution, as was verified by atomic force microscopy. Moreover, conformational changes in pectin from semiflexible chains to flexible chains or even flexible coils (a: 0.791, α: 0.597, ρ: 1.70) could be attributed to the decreased degree of methoxylation and neutral sugars in side chains and the destruction of inter- and intramolecular hydrogen bonds under ultrasonic processing. Therefore, these results have important implications for understanding the ultrasonic modification of pectin.


Assuntos
Citrus/metabolismo , Pectinas/química , Configuração de Carboidratos , Cromatografia Líquida de Alta Pressão , Dicroísmo Circular , Ligações de Hidrogênio , Microscopia de Força Atômica , Sonicação , Açúcares/química , Viscosidade
15.
Int J Nanomedicine ; 14: 3543-3555, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31190811

RESUMO

Background: In recent years, non-invasive imaging technologies for early cancer detection have drawn worldwide attention. In this study, an antinucleolin aptamer, AS1411, was successfully conjugated to BODIPY-labeled chitosan and studied on T47D and HEK-293 cell lines. Methods: After conjugation of the aptamer to chitosan nanoparticles and purification, its structure was confirmed using atomic force microscopy (AFM), electrophoretic light scattering (ELS) and dynamic light scattering (DLS). Results of AFM, DLS and ELS of both conjugation and chitosan were compared for confirmation of conjugation. Conjugates were mixed with BODIPY FL fluorescent dye, purified and lyophilized. The labeled conjugate was characterized using Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, ELS and DLS. In vitro cellular uptake and cytotoxic effects of BODIPY-labeled chitosan-AS1411 aptamer conjugates were evaluated using the XTT assay on T47D and HEK-293 cells and flow cytometry on T47D cells. Results: The data showed that uptake of BODIPY-labeled chitosan-AS1411 aptamer conjugate was satisfactory. Moreover, there was no statistically significant cytotoxicity of the conjugate on either cell line. Conclusion: The outcomes confirmed the potential application of this new targeted imaging agent as a novel cancer diagnostic agent for molecular imaging.


Assuntos
Compostos de Boro/química , Quitosana/química , Imagem Molecular/métodos , Nanopartículas/química , Oligodesoxirribonucleotídeos/química , Tamanho da Partícula , Aptâmeros de Nucleotídeos/química , Linhagem Celular Tumoral , Proliferação de Células , Endocitose , Fluorescência , Corantes Fluorescentes/química , Células HEK293 , Humanos , Microscopia de Força Atômica , Nanoconjugados/química , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier , Eletricidade Estática
16.
Soft Matter ; 15(27): 5455-5463, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31231747

RESUMO

Development of fast force volume (FFV), PeakForce Tapping (PFT), and related AFM techniques allow fast acquisition and mapping of a sample's mechanical properties. The methods are well-suited for studying soft biological samples like living cells in a liquid environment. However, the question remains how the measured mechanical properties are related to those acquired with the classical force volume (FV) technique conducted at low indentation rates. The difference is coming mostly from the pronounced viscoelastic behavior of cells, making apparent elastic parameters depending on the probing rate. Here, the viscoelastic analysis was applied directly to the force curves acquired with force volume or PeakForce Tapping by their post-processing based on the Ting's model. Maps from classical force volume, FFV and PFT obtained using special PFT cantilevers and cantilevers modified with microspheres were compared here. With the correct viscoelastic model, which was found to be the power-law rheology model, all the techniques have provided self-consistent results. The techniques were further modified for the mapping of the viscoelastic model-independent complex Young's modulus.


Assuntos
Fibroblastos/citologia , Animais , Linhagem Celular , Simulação por Computador , Módulo de Elasticidade , Camundongos , Microscopia de Força Atômica , Ratos , Reologia , Propriedades de Superfície , Viscosidade
17.
Clin Hemorheol Microcirc ; 71(4): 437-449, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31156152

RESUMO

BACKGROUND: Circulating red blood cells (RBCs) undergo aging, a fundamental physiological phenomenon that regulates their turnover. OBJECTIVE: Understanding the role of Aß in the cross talk between cell signalling pathways and modulation of the cell structural and biomechanical properties occurring in RBCs during aging. METHODS: The morphological pattern has been monitored using Atomic Force Microscopy (AFM) imaging and measuring the RBCs' plasma membrane roughness employed as a morphological parameter capable to provide information on the structure and integrity of the membrane-skeleton. RESULTS: We show that treatment with Aß accelerates the occurrence of morphological and biochemical aging markers in human RBC and influences the cell metabolism. Biochemical data demonstrate that contemporaneously to morphological alterations, Aß triggers: (i) metabolic alterations and (ii) a complex signaling pathway involving caspase 3, protein kinase C and nitric oxide derived metabolites. CONCLUSIONS: our study provides a comprehensive picture in which Aß treatment of RBC induces changes in specific cell signalling events and/or metabolic pathways, in turns affecting the membrane-cytoskeleton interaction and the membrane integrity.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Contagem de Eritrócitos/métodos , Microscopia de Força Atômica/métodos , Óxido Nítrico/metabolismo , Humanos , Transdução de Sinais
18.
World J Microbiol Biotechnol ; 35(7): 101, 2019 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-31236717

RESUMO

Propionibacterium acidipropionici produces propionic acid from different sugars and glycerol; the production can be improved by high cell density fermentations using immobilized cells that help to overcome the limitations of the non-productive lag phase and product inhibition. In this study, the use of stress factors to induce P. acidipropionici to form biofilm and its use as an immobilization procedure in fermentations in bioreactors for producing propionic acid was investigated. Citric acid and sodium chloride increased exopolysaccharide production, biofilm forming capacity index and trehalose production. Analysis of the expression of trehalose synthesis-related genes otsA and treY by RT-qPCR showed significantly increased expression of only treY during log phase with citric acid, while FISH analysis showed expression of treY and luxS under the influence of both stress factors. The stress factors were then used for development of microbial biofilms as immobilization procedure on Poraver® and AnoxKaldnes® carriers in recycle batch reactors for propionic acid production from 20 g/L glycerol. Highest productivities of 0.7 and 0.78 g/L/h were obtained in Poraver® reactors, and 0.39 and 0.43 g/L/h in AnoxKaldnes® reactors with citric acid and NaCl, respectively.


Assuntos
Biofilmes , Propionatos/metabolismo , Propionibacterium/metabolismo , Estresse Fisiológico , Reatores Biológicos/microbiologia , Células Imobilizadas , Fermentação , Regulação da Expressão Gênica , Genes Bacterianos , Glicerol/metabolismo , Hibridização in Situ Fluorescente , Microscopia de Força Atômica , Propionibacterium/genética , RNA Ribossômico 16S/genética , RNA Ribossômico 16S/isolamento & purificação , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Trealose/metabolismo
19.
Forensic Sci Int ; 301: 254-262, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31181409

RESUMO

Bloodstains can provide important information about a criminal act. These biological traces, when analyzed at murder sites, for example, can determine the dynamics of a criminal offense, the identity of a suspect, and the time at which a crime was committed. Determine the time since deposition (TSD) of these blood traces may be the first clue for the police investigators to estimate the time-lapse of a murder. During a criminal attack, the blood spilled from an injury begins the process of degradation and aging from the moment it leaves the human body and comes into contact with the physical environment. The biophysical properties (morphology and elasticity) of red blood cells (RBCs) undergo several changes when outside the human body, which can be analyzed using microscopic techniques such as atomic force microscopy (AFM). Aiming to apply the AFM/force spectroscopy techniques in the analysis of criminal traces, the present study investigated the TSD for blood smears by analyzing possible changes in the RBCs of a group of voluntary donors. Also, we investigated whether there was any difference in TSD analysis after blood smears deposition onto three different surfaces (glass, metal, or ceramic); and finally, we evaluated force×distance curves obtained from deformation of the membrane surface of RBCs as a function of time. The qualitative results apparently showed that there is no perceptible difference in the structure of RBCs when AFM images were analyzed by simple visual comparison over 28 days (T0-T5). Nevertheless, our quantitative results, measured by AFM, demonstrated the increasing trend of the measurements, such as average height (µm), perimeter (µm), area (µm2) and volume (µm3) of these cells during that period. Additionally, the type of surface of bloodstain deposition should be considered during analyses for the TSD, and the results obtained on glass, metal, or ceramic supports showed significant differences. Therefore, the use of force spectroscopy to obtain force×distance curves for the forensic science approach has been shown to have applicability for the calculation of TSD in the RBCs present in the blood smears. In spite of the promising observations obtained, the use of AFM in crime scenes still requires the expansion and development of more studies for a definitive evaluation of the TSD for blood spots.


Assuntos
Manchas de Sangue , Eritrócitos/ultraestrutura , Microscopia de Força Atômica , Adulto , Membrana Celular , Cerâmica , Elasticidade , Feminino , Medicina Legal/métodos , Vidro , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Metais , Software , Propriedades de Superfície , Fatores de Tempo , Adulto Jovem
20.
Food Chem ; 297: 124766, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31253308

RESUMO

The complexation of nanoparticles in extreme alkali treated (pH 10.0, 11.0 and 12.0) soy protein isolate (SPI) with 1-Octacosanol (1-Octa) was investigated. The nanoparticles were compared in complexing with the 1-Octa concerning their characteristics, along with the changes in secondary structure and stability of 1-Octa upon complexation. The nanoparticles did not display obvious changes in size and morphology upon complexation with 1-Octa, except the surface hydrophobicity. The encapsulation efficiency (EE) and loading amount (LA) of the SPI-Octa were first increased and then decreased with an enhanced pH value. The treatment conditions modified some secondary structures, causing greater protein unfolding to expose more hydrophobic clusters. Additionally, the nanocomplex had higher thermal and saline ion stability, the majority of the nanocomplexes were evenly dispersed in the aqueous phase.


Assuntos
Álcoois Graxos/química , Nanopartículas/química , Proteínas de Soja/química , Álcoois Graxos/metabolismo , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Microscopia de Força Atômica , Tamanho da Partícula , Estrutura Secundária de Proteína , Desdobramento de Proteína , Proteínas de Soja/metabolismo , Propriedades de Superfície
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