Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 58.600
Filtrar
1.
Food Chem ; 366: 130422, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34392082

RESUMO

Tea cream, produced by interactions among tea ingredients, is undesirable in tea beverage industry. The interaction between bovine serum albumin (BSA) and theaflavin-3,3'-digallate (TFDG, an important component in tea cream and functional substance of black tea) was investigated by fluorescence spectroscopy, ultraviolet-visible (UV-vis) absorption spectroscopy, synchronous fluorescence spectroscopy, fourier-transform infrared (FT-IR) spectroscopy, and molecular docking technique. Multi-spectroscopic experiments demonstrated that TFDG interacted with BSA via static quenching, and the microenvironment around BSA became more hydrophobicity. FT-IR showed that the α-helix of BSA was increased when binding with TFDG. Thermodynamic parameters and molecular docking demonstrated that hydrophobic interactions and hydrogen bonds dominated the interaction between TFDG and BSA. The mechanism proposed in this research could further develop some nanoparticles to excellent biochemical properties while reducing the formation of tea cream, and explore the potential of BSA as transport carrier for TFDG.


Assuntos
Soroalbumina Bovina , Biflavonoides , Sítios de Ligação , Catequina/análogos & derivados , Dicroísmo Circular , Simulação de Acoplamento Molecular , Ligação Proteica , Soroalbumina Bovina/metabolismo , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica
2.
Spectrochim Acta A Mol Biomol Spectrosc ; 264: 120261, 2022 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-34419830

RESUMO

Bovine serum albumin (BSA) has been used as a transporter protein for levothyroxine (LT4) and rutin, due to its property of binding to various ligands. Rutin binding to the BSA-LT4 complex can bring many benefits due to its proven pharmacological properties. Using Fourier-Transform Infrared Spectroscopy (FT-IR) the changes induced by rutin in the structure of BSA-LT4 complex were determined. Fluorescence studies allowed us to determine the quenching mechanism and affinity of rutin to the BSA-LT4 complex. The thermodynamic parameters suggest the binding of rutin to BSA-LT4 is a spontaneous process, driven by enthalpy and electrostatic forces. Also, the second derivative of the emission spectra suggests the Trp's of BSA are located in two different microenvironments. Thermal and chemical denaturation of BSA-LT4-rutin complex presents similar behavior but with better stability of the complex in case of chemical denaturation. Molecular docking studies show the binding of the two ligands to the same BSA site, suggesting that rutin may influence the bond of LT4 with the protein. Studies on the antioxidant activity of the BSA-LT4-rutin complex suggest that the presence of LT4 decreases the antioxidant activity of the rutin, but even so this antioxidant activity can be used to bring benefits for medical purposes.


Assuntos
Rutina , Soroalbumina Bovina , Sítios de Ligação , Simulação de Acoplamento Molecular , Ligação Proteica , Soroalbumina Bovina/metabolismo , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica , Tiroxina
3.
Spectrochim Acta A Mol Biomol Spectrosc ; 264: 120298, 2022 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-34464920

RESUMO

Dapagliflozin (DAPA) is a selective sodium-glucose cotransporter-2 inhibitor that reduces renal glucose reabsorption. The drug has recently become a crucial milestone in the management of diabetes and heart failure. In this study, the interaction of DAPA with bovine serum albumin (BSA) was investigated for the first time using various fluorescence spectroscopic techniques, UV-absorption spectroscopy, molecular docking, and molecular dynamic (MD) simulation. The fluorescence spectroscopic titration study performed at different temperatures showed that DAPA quenched the fluorescence of BSA through a combination of dynamic and static mechanisms, which was confirmed by UV absorption, fluorescence-resonance energy transfer measurements, and MD simulation. The binding thermodynamic parameters demonstrated that the binding stoichiometry between BSA and DAPA was 1:1. Competitive binding experiments using site-specific markers as well as molecular docking studies showed that DAPA binds to site I on BSA. The positive values of enthalpy change (ΔH) and entropy change (ΔS) revealed that hydrophobic forces played a predominant role in the binding of DAPA to BSA, whereas the negative value of Gibbs free energy change (ΔG) indicated the spontaneity of the interaction. Moreover, the synchronous fluorescence spectroscopy has shown that DAPA binding to the protein molecule occurs in the vicinity of the tryptophan residue. These findings were confirmed by the molecular docking and MD simulation studies.


Assuntos
Diabetes Mellitus Tipo 2 , Inibidores do Transportador 2 de Sódio-Glicose , Compostos Benzidrílicos , Sítios de Ligação , Glucosídeos , Humanos , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Ligação Proteica , Soroalbumina Bovina/metabolismo , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta , Termodinâmica
4.
Spectrochim Acta A Mol Biomol Spectrosc ; 264: 120334, 2022 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-34481252

RESUMO

Herein, a simple spectrophotometric method coupled with chemometric techniques i.e. partial least square (PLS) and genetic algorithm (GA) were utilized for the simultaneous determination of the vital ternary antiretroviral therapy dolutegravir (DTG), lamivudine (LMV), and abacavir (ACV) in their combined dosage form. Calibration (25 samples) and validation (13 samples) sets were prepared for these drugs at different concentrations via implementing partial factorial experimental designs. The zero order UV spectra of calibration and validation sets were measured and then subjected for further chemometric analysis. Partial least squares with/without variable selection procedures i.e. genetic algorithm (GA) were utilized to untangle the UV spectral overlapping of these mixtures. Cross-validation and external validation methods were applied to compare the performance of these chemometric techniques in terms of accuracy and predictive abilities. It was found that six latent variables were optimum for modelling DTG, four latent variables for modelling LMV and three latent variables for modelling ACV. Although, good recoveries with prompt predictive ability were attained by these PLS, GA-PLS showed better analytical performance owing to its capability to remove redundant variables i.e. the number of absorbance variables have been reduced to about 21-29%. The proposed chemometric methods can be reliably applied for simultaneous determination of DTG, LMV, and ACV in their laboratory prepared mixtures and pharmaceutical preparation posing these chemometric methods as worthy and substantial analytical tools in in-process testing and quality control analysis of many antiretroviral pharmaceutical preparations.


Assuntos
Infecções por HIV , Lamivudina , Calibragem , Didesoxinucleosídeos , Compostos Heterocíclicos com 3 Anéis , Humanos , Análise dos Mínimos Quadrados , Oxazinas , Piperazinas , Piridonas , Espectrofotometria , Espectrofotometria Ultravioleta
5.
Food Chem ; 372: 131280, 2022 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-34818732

RESUMO

In this study, the binding mechanism between bovine serum albumin (BSA) and three gingerols ([6]-, [8]- and [10]-gingerol) was evaluated to explore an effective strategy for improving solubility and stability of gingerols. The fluorescence analysis suggested gingerols could bind with BSA to form a stable BSA/gingerols complex and [10]-gingerol had the strongest binding affinity (Ka = 4.016 × 104 L/mol) at 298 K. Thermodynamic parameters and molecular modeling validated that hydrophobic interaction and hydrogen bonds were the main driving force for the interaction of BSA/gingerols. Gingerols bound to BSA at site I (subdomain IIA) resulted in a conformational change of BSA with a structure shrinkage, which was responsible for the decrease of surface hydrophobicity. The formation of BSA/gingerols complexes promoted the solubility of [6]-, [8]- and [10]-gingerol increasing by 1.50, 6.04 and 23.50 times, respectively. In addition, the stability and antioxidant capacity of gingerols was significantly improved after binding with BSA.


Assuntos
Soroalbumina Bovina , Sítios de Ligação , Catecóis , Dicroísmo Circular , Álcoois Graxos , Simulação de Acoplamento Molecular , Ligação Proteica , Soroalbumina Bovina/metabolismo , Solubilidade , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta , Termodinâmica
6.
Molecules ; 26(20)2021 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-34684721

RESUMO

Green nanoparticle synthesis is an environmentally friendly approach that uses natural solvents. It is preferred over chemical and physical techniques due to the time and energy savings. This study aimed to synthesize zinc oxide nanoparticles (ZnO NPs) through a green method that used Phlomis leaf extract as an effective reducing agent. The synthesis and characterization of ZnO NPs were confirmed by UV-Vis spectrophotometry, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Dynamic light scattering (DLS), Zeta potential, and Field Emission Scanning Electron Microscope (FESEM) techniques. In vitro cytotoxicity was determined in L929 normal fibroblast cells using MTT assay. The antibacterial activity of ZnO nanoparticles was investigated using a disk-diffusion method against S. aureus and E. coli, as well as minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) content concentrations. XRD results confirmed the nanoparticles' crystalline structure. Nanoparticle sizes were found to be around 79 nm by FESEM, whereas the hydrodynamic radius of nanoparticles was estimated to be around 165 ± 3 nm by DLS. FTIR spectra revealed the formation of ZnO bonding and surfactant molecule adsorption on the surface of ZnO NPs. It is interesting to observe that aqueous extracts of Phlomis leave plant are efficient reducing agents for green synthesis of ZnO NPs in vitro, with no cytotoxic effect on L929 normal cells and a significant impact on the bacteria tested.


Assuntos
Química Verde/métodos , Nanopartículas Metálicas/química , Phlomis/metabolismo , Antibacterianos/farmacologia , Anti-Infecciosos/farmacologia , Bactérias/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Extratos Vegetais/química , Substâncias Redutoras/farmacologia , Espectrometria por Raios X/métodos , Espectrofotometria Ultravioleta/métodos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Difração de Raios X/métodos , Óxido de Zinco/química
7.
Anal Chim Acta ; 1185: 339042, 2021 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-34711315

RESUMO

The nitro functional group (NO2) features strongly in compounds such as explosives, pharmaceuticals, and fragrances. However, its gas phase absorbance characteristics in the vacuum UV region (120-200 nm) have not been systematically studied. Gas chromatography/vacuum UV spectroscopy (GC/VUV) was utilized to study the gas phase VUV spectra of various nitrated compounds (e.g., nitrate esters (-R-O-NO2), nitramines (R-N-NO2), nitroaromatics (Ar-NO2), and nitroalkanes (R-NO2)). The nitro absorption maximum appeared over a wide range (170-270 nm) and its wavelength and intensity were highly dependent upon the structure of the rest of the molecule. For example, the nitroalkanes exhibited a trend in that the ratio of the relative absorption intensity between these two absorption features between the alkyl group (<150 nm) and the nitro group (200 nm) increases as the molecular weight increases. It was observed that the addition of multiple nitro functional groups on benzene or toluene resulted in an increase in intensity and blue shift from approximately 240 nm-210 nm. Nitrate esters exhibited an absorption between 170 nm and 210 nm and absorbance increased with increasing nitrogen content. The relative diversity of the spectra obtained was analyzed by Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA). These calculations revealed that the spectra of all the compounds analyzed could be reliably differentiated without any misclassifications.


Assuntos
Ésteres , Cromatografia Gasosa , Análise Discriminante , Espectrofotometria Ultravioleta , Vácuo
8.
Molecules ; 26(19)2021 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-34641538

RESUMO

Response surface methodology (RSM) with a Box-Behnken design (BBD) was used to optimize the extraction of bioactive compounds from Ephedra fragilis. The results suggested that extraction with 61.93% ethanol at 44.43 °C for 15.84 h was the best solution for this combination of variables. The crude ethanol extract (CEE) obtained under optimum extraction conditions was sequentially fractionated with solvents of increasing polarity. The content of total phenolic (TP) and total flavonoid (TF) as well as the antioxidant and antiglycation activities were measured. The phytochemical fingerprint profile of the fraction with the highest activity was characterized by using RP-HPLC. The ethyl acetate fraction (EAF) had the highest TP and TF contents and exhibited the most potent antioxidant and antiglycation activities. The Pearson correlation analysis results showed that TP and TF contents were highly significantly correlated with the antioxidant and antiglycation activities. Totally, six compounds were identified in the EAF of E. fragilis, including four phenolic acids and two flavonoids. Additionally, molecular docking analysis also showed the possible connection between identified bioactive compounds and their mechanisms of action. Our results suggest new evidence on the antioxidant and antiglycation activities of E. fragilis bioactive compounds that may be applied in the treatment and prevention of aging and glycation-associated complications.


Assuntos
Antioxidantes/química , Ephedra/química , Compostos Fitoquímicos/química , Compostos Fitoquímicos/farmacologia , Animais , Bovinos , Fracionamento Químico/métodos , Cromatografia Líquida de Alta Pressão , Flavonoides/análise , Flavonoides/isolamento & purificação , Peróxido de Hidrogênio/química , Ácido Linoleico/química , Reação de Maillard , Simulação de Acoplamento Molecular , Fenóis/análise , Fenóis/isolamento & purificação , Compostos Fitoquímicos/isolamento & purificação , Compostos Fitoquímicos/metabolismo , Extratos Vegetais/química , Reprodutibilidade dos Testes , Soroalbumina Bovina/metabolismo , Espectrofotometria Ultravioleta , beta Caroteno/química
9.
ScientificWorldJournal ; 2021: 8856147, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34594161

RESUMO

Candida albicans and Candida tropicalis are the leading causes of human fungal infections worldwide. There is an increase in resistance of Candida pathogens to existing antifungal drugs leading to a need to find new sources of antifungal agents. Tormentic acid has been isolated from different plants including Callistemon citrinus and has been found to possess antimicrobial properties, including antifungal activity. The study aimed to determine the effects of tormentic and extracts from C. citrinus on C. albicans and C. tropicalis and a possible mode of action. The extracts and tormentic acid were screened for antifungal activity using the broth microdilution method. The growth of both species was inhibited by the extracts, and C. albicans was more susceptible to the extract compared to C. tropicalis. The growth of C. albicans was inhibited by 80% at 100 µg/ml of both the DCM: methanol extract and the ethanol: water extract. Tormentic acid reduced the growth of C. albicans by 72% at 100 µg/ml. The effects of the extracts and tormentic acid on ergosterol content in C. albicans were determined using a UV/Vis scanning spectrophotometer. At concentrations of tormentic acid of 25 µg/ml, 50 µg/ml, 100 µg/ml, and 200 µg/ml, the content of ergosterol was decreased by 22%, 36%, 48%, and 78%, respectively. Similarly, the DCM: methanol extract at 100 µg/ml and 200 µg/ml decreased the content by 78% and 88%, respectively. A dose-dependent decrease in ergosterol content was observed in cells exposed to miconazole with a 25 µg/ml concentration causing a 100% decrease in ergosterol content. Therefore, tormentic acid inhibits the synthesis of ergosterol in C. albicans. Modifications of the structure of tormentic acid to increase its antifungal potency may be explored in further studies.


Assuntos
Candida albicans/efeitos dos fármacos , Candida tropicalis/efeitos dos fármacos , Ergosterol/biossíntese , Melaleuca/química , Extratos Vegetais/farmacologia , Triterpenos/farmacologia , Antifúngicos/farmacologia , Candida albicans/crescimento & desenvolvimento , Candida albicans/metabolismo , Candida tropicalis/crescimento & desenvolvimento , Candida tropicalis/metabolismo , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Folhas de Planta/química , Especificidade da Espécie , Espectrofotometria Ultravioleta
10.
Inorg Chem ; 60(19): 14515-14519, 2021 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-34505770

RESUMO

Nanozyme is a class of artificial materials that possess enzyme-like activities and can overcome limitations of natural enzymes. However, controllability of the active sites, uniformity of the particles, and dispersion in the physiological media are still challenging for nanomaterial-based nanozymes. In this work, a protein-based nanozyme has been constructed by the encapsulation of hemin into the nanocavity of a recombinant human heavy chain ferritin (Ftn), generating a monodispersed peroxidase-mimetic nanozyme (hemin@Ftn). Hemin@Ftn possesses high peroxidase catalytic activity and high tolerance to the harsh environmental conditions, such as high temperature and chemical denaturant. Remarkably, hemin@Ftn can act as a colorimetric probe for the detection of tumor cells because it can selectively catalyze reactions in tumor cells. This protein-based nanozyme bridges the gap between natural enzymes and nanomaterial-based nanozymes by the incorporation of a catalytically active prosthetic group into a highly stable Ftn.


Assuntos
Ferritinas/química , Hemina/química , Nanoestruturas/química , Animais , Linhagem Celular , Humanos , Camundongos , Espectrofotometria Ultravioleta
11.
J Phys Chem Lett ; 12(37): 9020-9025, 2021 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-34516127

RESUMO

Ribonucleotide reductase (RNR), which supplies the building blocks for DNA biosynthesis and its repair, has been linked to human diseases and is emerging as a therapeutic target. Here, we present a mechanistic investigation of triapine (3AP), a clinically relevant small molecule that inhibits the tyrosyl radical within the RNR ß2 subunit. Solvent kinetic isotope effects reveal that proton transfer is not rate-limiting for inhibition of Y122· of E. coli RNR ß2 by the pertinent 3AP-Fe(II) adduct. Vibrational spectroscopy further demonstrates that unlike inhibition of the ß2 tyrosyl radical by hydroxyurea, a carboxylate containing proton wire is not at play. Binding measurements reveal a low nanomolar affinity (Kd ∼ 6 nM) of 3AP-Fe(II) for ß2. Taken together, these data should prompt further development of RNR inactivators based on the triapine scaffold for therapeutic applications.


Assuntos
Inibidores Enzimáticos/química , Proteínas de Escherichia coli/metabolismo , Escherichia coli/enzimologia , Compostos Ferrosos/química , Piridinas/química , Ribonucleotídeo Redutases/metabolismo , Tiossemicarbazonas/química , Inibidores Enzimáticos/metabolismo , Proteínas de Escherichia coli/antagonistas & inibidores , Radicais Livres/química , Radicais Livres/metabolismo , Hidroxiureia/química , Ligação Proteica , Subunidades Proteicas/antagonistas & inibidores , Subunidades Proteicas/química , Subunidades Proteicas/metabolismo , Ribonucleotídeo Redutases/antagonistas & inibidores , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier
12.
Photochem Photobiol Sci ; 20(10): 1309-1321, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34562236

RESUMO

The initial objective of our work was to synthesize a series of 2-amino-4H-pyran-3-carbonitriles to be tested for their antifungal activities against economically relevant phytopathogenic fungi. Fourteen compounds were prepared in up to 94% yield and shown percentages of Botrytis cinerea inhibition above 70%. Despite the promising biological results, we observed that stock solutions prepared for biological tests showed color changing when kept for a few days on the laboratory bench, under room conditions, illuminated by common LED daylight tubes (4500-6000 k). This prompted us to investigate the possible photo-induced degradation of our compounds. FT-IR ATR experiments evidenced variations in the expected bands for functional of -amino-4H-pyran-3-carbonitriles stored under LED daylight. Following, HPLC-UV analysis showed reductions in the intensity of chromatographic peaks of 2-amino-4H-pyran-3-carbonitriles, and but not for solutions kept in the dark. A solution of (E)-2-amino-8-(4-nitrobenzylidene)-4-(4-nitrophenyl)-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile underwent 84.4% of conversion after 72 h of exposure to continuous LED daylight in a BOD chamber, and the reaction product was isolated in 36% yield and characterized as (E)-7-cyano-5-(4-nitrobenzylidene)-8-(4-nitrophenyl)bicyclo[4.2.0]oct-1(6)-ene-7-carboxamide (7*). Despite freshly prepared solutions of 2-amino-4H-pyran-3-carbonitriles produced antifungal activities, these solutions lost biological activity when left on the bench for a week. Besides, compound 7* formed from photo-induced degradation of 7 also showed no antifungal activity. With this, we hope to bring two contributions: (1) production of cyclobutenes through photochemical reactions of 2-amino-4H-pyran-3-carbonitriles can be carried out through exposure to simple white LED daylight; (2) biological applications of such 2-amino-4H-pyran-3-carbonitriles may be impaired by their poor photostability.


Assuntos
Antifúngicos/farmacologia , Botrytis/efeitos dos fármacos , Luz , Piranos/química , Antifúngicos/síntese química , Antifúngicos/química , Cromatografia Líquida de Alta Pressão , Conformação Molecular , Fotólise/efeitos da radiação , Piranos/síntese química , Piranos/farmacologia , Espectrofotometria Ultravioleta
13.
Molecules ; 26(18)2021 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-34577104

RESUMO

During forced degradation, the intrinsic stability of active pharmaceutical ingredients (APIs) could be determined and possible impurities that would occur during the shelf life of the drug substance or the drug product could be estimated. Vildagliptin belongs to relatively new oral antidiabetic drugs named gliptins, inhibiting dipeptidyl peptidase 4 (DPP-4) and prolonging the activities of the endogenous incretin hormones. At the same time, some gliptins were shown as prone to degradation under specific pH and temperature conditions, as well as in the presence of some reactive excipients. Thus, forced degradation of vildagliptin was performed at high temperature in extreme pH and oxidative conditions. Then, selective LC-UV was used for quantitative determination of non-degraded vildagliptin in the presence of its degradation products and for degradation kinetics. Finally, identification of degradation products of vildagliptin was performed using an UHPLC-DAD-MS with positive ESI. Stability of vildagliptin was also examined in the presence of pharmaceutical excipients, using mid-IR and NIR with principal component analysis (PCA). At 70 °C almost complete disintegration of vildagliptin occurred in acidic, basic, and oxidative media. What is more, high degradation of vildagliptin following the pseudo first-order kinetics was observed at room temperature with calculated k values 4.76 × 10-4 s-1, 3.11 × 10-4 s-1, and 1.73 × 10-4 s-1 for oxidative, basic and acidic conditions, respectively. Next, new degradation products of vildagliptin were detected using UHPLC-DAD-MS and their molecular structures were proposed. Three degradants were formed under basic and acidic conditions, and were identified as [(3-hydroxytricyclo- [3.3.1.13,7]decan-1-yl)amino]acetic acid, 1-{[(3-hydroxytricyclo[3.3.1.13,7]decan-1-yl)amino]acetyl}-pyrrolidine-2-carboxylic acid and its O-methyl ester. The fourth degradant was formed in basic, acidic, and oxidative conditions, and was identified as 1-{[(3-hydroxytricyclo[3.3.1.13,7]-decan-1-yl)amino]acetyl}pyrrolidine-2-carboxamide. When stability of vildagliptin was examined in the presence of four excipients under high temperature and humidity, a visible impact of lactose, mannitol, magnesium stearate, and polyvinylpirrolidone was observed, affecting-NH- and CO groups of the drug. The obtained results (kinetic parameters, interactions with excipients) may serve pharmaceutical industry to prevent chemical changes in final pharmaceutical products containing vildagliptin. Other results (e.g., identification of new degradation products) may serve as a starting point for qualifying new degradants of vildagliptin as it is related to substances in pharmacopoeias.


Assuntos
Cromatografia Líquida/métodos , Estabilidade de Medicamentos , Hipoglicemiantes/química , Espectrofotometria Infravermelho/métodos , Vildagliptina/química , Inibidores da Dipeptidil Peptidase IV/química , Excipientes/química , Temperatura Alta , Umidade , Concentração de Íons de Hidrogênio , Cinética , Lactose/química , Manitol/química , Espectrometria de Massas , Oxirredução , Povidona/análogos & derivados , Povidona/química , Análise de Componente Principal , Espectrofotometria Ultravioleta , Ácidos Esteáricos/química
14.
J Phys Chem Lett ; 12(39): 9470-9474, 2021 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-34558899

RESUMO

Mechanophores that are embedded in a polymer backbone respond to the application of mechanical stretching forces by geometric changes such as bond rupture. Typically, these structural changes are irreversible, which limits the applicability of functional materials incorporating mechanophores. Using computational methods, we, here, present a general method of restoring a force-activated mechanophore to its deactivated form by using hydrostatic pressure. We use the spiropyran-merocyanine (SP-MC) interconversion to show that repeated activation of the SP mechanophore and deactivation of MC can be achieved by alternating mechanical stretching and hydrostatic compression, respectively. In the baromechanical cycle, MC acts as a "barophore" that responds to hydrostatic pressure by bond formation. The activation and deactivation of SP/MC are understood in terms of strain and electronic effects. Beneficially, this two-step baromechanical cycle can be observed in real time by using UV/vis spectroscopy. Our calculations pave the way for improving the applicability and reusability of force-responsive materials.


Assuntos
Benzopiranos/química , Indóis/química , Nitrocompostos/química , Pressão Hidrostática , Espectrofotometria Ultravioleta , Termodinâmica
15.
PLoS One ; 16(9): e0257071, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34506550

RESUMO

Aspergillus niger metabolites exhibited a wide range of biological properties including antioxidant and neuro-protective effects and some physical properties as green synthesis of silver nanoparticles AgNP. The present study presents a novel evidence for the various biological activities of green synthesized AgNPs. For the first time, some isolated naphtho-γ-pyrones from marine-derived Aspergillus niger, flavasperone (1), rubrofusarin B (2), aurasperone A (3), fonsecinone A (4) in addition to one alkaloid aspernigrin A (7) were invistigated for their inhibitory activity of acetylcholine esterase AChE, a hallmark of Alzheimer's disease (AD). The ability to synthesize AgNPs by compounds 3, 4 and 7 has been also tested for the first time. Green synthesized AgNPs were well-dispersed, and their size was ranging from 8-30 nm in diameter, their morphology was obviously spherical capped with the organic compounds. Further biological evaluation of their AChE inhibitory activity was compared to the parent compounds. AgNps dramatically increased the inhibitory activity of Compounds 4, 3 and 7 by 84, 16 and 13 fold, respectively to be more potent than galanthamine as a positive control with IC50 value of 1.43 compared to 0.089, 0.311 and 1.53 of AgNPs of Compounds 4, 3 and 7, respectively. Also compound 2 showed moderate inhibitory activity. This is could be probably explained by closer fitting to the active sites or the synergistic effect of the stabilized AgNPs by the organic compouds. These results, in addition to other intrinsic chemical and biological properties of naphtho-γ-pyrones, suggest that the latter could be further explored with a view towards other neuroprotective studies for alleviating AD.


Assuntos
Acetilcolinesterase/metabolismo , Organismos Aquáticos/microbiologia , Aspergillus niger/química , Inibidores da Colinesterase/farmacologia , Química Verde , Nanopartículas/química , Pironas/isolamento & purificação , Prata/química , Nanopartículas/ultraestrutura , Pironas/química , Espectrofotometria Ultravioleta
16.
Molecules ; 26(16)2021 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-34443509

RESUMO

The main goal of this work was to study the structural transformation of humic acids (HAs) under the influence of selected strains of fungi (Aspergillus niger and Paecilomyces lilacinus) and bacteria (Bacillus sp., Paenibacillus polymyxa and Bacillus amyloliquefaciens) with/without the presence of NPK fertilizers. Two-year experiments were conducted on two different soils and HAs isolated from these soils were examined for structure, humification degree, and quantity using fluorescence and UV-Vis spectroscopy, elemental analysis, and extraction methods. Results showed that the applied additives contributed to the beneficial transformation of HAs, but effects differed for various soils. HAs from silty soil with higher organic carbon content showed simplification of their structure, and decreases in humification, molecular weight, and aromaticity under the influence of fungi and bacteria without NPK, and with NPK alone. With both fungi and NPK, increases in O/H and O/C atomic ratios indicated an increase in the number of O-containing functional groups. HAs from sandy soil did not show as many significant changes as did those from silty soil. Sandy soil exhibited a strong decline in HA content in the second year that was reduced/neutralized by the presence of fungi, bacteria, and NPK. Periodically observed fluorescence at ~300 nm/450 nm reflected formation of low-molecular HAs originating from the activity of microorganisms.


Assuntos
Agricultura , Bactérias/efeitos dos fármacos , Fertilizantes/análise , Fungos/efeitos dos fármacos , Substâncias Húmicas/análise , Minerais/farmacologia , Solo/química , Fluorescência , Espectrofotometria Ultravioleta
17.
Molecules ; 26(16)2021 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-34443447

RESUMO

Okara is a soybean transformation agri-food by-product, the massive production of which currently poses severe disposal issues. However, its composition is rich in seed storage proteins, which, once extracted, can represent an interesting source of bioactive peptides. Antimicrobial and antifungal proteins and peptides have been described in plant seeds; thus, okara is a valuable source of compounds, exploitable for integrated pest management. The aim of this work is to describe a rapid and economic procedure to isolate proteins from okara, and to produce an enzymatic proteolyzed product, active against fungal plant pathogens. The procedure allowed the isolation and recovery of about 30% of okara total proteins. Several proteolytic enzymes were screened to identify the proper procedure to produce antifungal compounds. Antifungal activity of the protein digested for 24 h with pancreatin against Fusarium and R. solani mycelial growth and Pseudomonas spp was assessed. A dose-response inhibitory activity was established against fungi belonging to the Fusarium genus. The exploitation of okara to produce antifungal bioactive peptides has the potential to turn this by-product into a paradigmatic example of circular economy, since a field-derived food waste is transformed into a source of valuable compounds to be used in field crops protection.


Assuntos
Antifúngicos/farmacologia , Enzimas/metabolismo , Proteínas de Plantas/metabolismo , Plantas/microbiologia , Polissacarídeos/metabolismo , Liofilização , Fusarium/efeitos dos fármacos , Fusarium/crescimento & desenvolvimento , Testes de Sensibilidade Microbiana , Peso Molecular , Proteólise/efeitos dos fármacos , Alimentos de Soja , Espectrofotometria Ultravioleta , Tripsina/metabolismo , Inibidores da Tripsina/farmacologia
18.
Phys Chem Chem Phys ; 23(33): 17813-17825, 2021 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-34397052

RESUMO

Photoactive yellow protein (PYP) is one of the typical light sensor proteins. Although its photoreaction has been extensively studied, no downstream partner protein has been identified to date. In this study, the intermolecular interaction dynamics observed between PYP from Rhodobacter capsulatus (Rc-PYP) and a possible downstream protein, PYP-binding protein (PBP), were investigated. It was found that UV light induced a long-lived product (pUV*), which interacts with PBP to form a stable hetero-hexamer (Complex-2). The reaction scheme for this interaction was revealed using transient absorption and transient grating methods. Time-resolved diffusion detection showed that a hetero-trimer (Complex-1) is formed transiently, which produced Complex-2 via a second-order reaction. Any other intermediates, including those from pBL, do not interact with PBP. The reaction scheme and kinetics are determined. Interestingly, long-lived Complex-2 dissociates upon excitation with blue light. These results demonstrate that Rc-PYP is a photochromic and new type of UV sensor to sense the relative intensities of UV-A and blue light.


Assuntos
Proteínas de Bactérias/química , Fotorreceptores Microbianos/química , Proteínas de Bactérias/isolamento & purificação , Fotorreceptores Microbianos/isolamento & purificação , Rhodobacter capsulatus/química , Espectrofotometria Ultravioleta , Raios Ultravioleta
19.
Photochem Photobiol Sci ; 20(9): 1173-1181, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34460093

RESUMO

Solvent access to the protein interior plays an important role in the function of many proteins. Phytochromes contain a specific structural feature, a hairpin extension that appears to relay structural information from the chromophore to the rest of the protein. The extension interacts with amino acids near the chromophore, and hence shields the chromophore from the surrounding solvent. We envision that the detachment of the extension from the protein surface allows solvent exchange reactions in the vicinity of the chromophore. This can facilitate for example, proton transfer processes between solvent and the protein interior. To test this hypothesis, the kinetics of the protonation state of the biliverdin chromophore from Deinococcus radiodurans bacteriophytchrome, and thus, the pH of the surrounding solution, is determined. The observed absorbance changes are related to the solvent access of the chromophore binding pocket, gated by the hairpin extension. We therefore propose a model with an "open" (solvent-exposed, deprotonation-active on a (sub)second time-scale) state and a "closed" (solvent-gated, deprotonation inactive) state, where the hairpin fluctuates slowly between these conformations thereby controlling the deprotonation process of the chromophore on a minute time scale. When the connection between the hairpin and the biliverdin surroundings is destabilized by a point mutation, the amplitude of the deprotonation phase increases considerably. In the absence of the extension, the chromophore deprotonates essentially without any "gating". Hence, we introduce a straightforward method to study the stability and fluctuation of the phytochrome hairpin in its photostationary state. This approach can be extended to other chromophore-protein systems where absorption changes reflect dynamic processes of the protein.


Assuntos
Proteínas de Bactérias/química , Biliverdina/química , Deinococcus/química , Fitocromo/química , Sítios de Ligação , Concentração de Íons de Hidrogênio , Cinética , Modelos Moleculares , Conformação Proteica , Prótons , Solventes , Espectrofotometria Ultravioleta
20.
Inorg Chem ; 60(17): 12681-12684, 2021 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-34382784

RESUMO

Aquacobalamin binds hydrogen peroxide reversibly to form a cobalt(III) hydroperoxo adduct with a 0.25 mM dissociation constant, as evidenced by UV-vis absorption spectroscopy and corroborated by NMR, Raman spectroscopy, stopped-flow UV-vis measurements, and density functional theory calculations.


Assuntos
Peróxido de Hidrogênio/química , Vitamina B 12/análogos & derivados , Cobalto/química , Teoria da Densidade Funcional , Espectroscopia de Ressonância Magnética , Modelos Químicos , Espectrofotometria Ultravioleta , Análise Espectral Raman , Vitamina B 12/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...