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1.
Environ Monit Assess ; 193(3): 131, 2021 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-33590376

RESUMEN

The adsorption properties of Shanghai silty clay (SSC) towards heavy metal ions Cd(II), Pb(II), As(V), and Cr(VI) were investigated by batch experiments. The effects of solid-solution ratio, pH, temperature, reaction time, and metal concentration on sorption were analyzed. In order to better understand the adsorption mechanisms, X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray fluorescence (XRF) were used to analyze the soil specimen before and after sorption. Three adsorption kinetic models and three adsorption isotherm models were used to analyze the adsorption characteristics. Thermodynamic parameters including changes in the Gibbs free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were also calculated. Sorption capacity of SSC was compared with other clay minerals reported in the literatures. The results show that the selectivity sequence is Pb(II) > Cd(II) > As(V) > Cr(VI), with equilibrium sorption capacities of 26.46, 8.90, 2.80, and 1.85 mg g-1, respectively. Adsorption is largely effective on the clay surface rather than on the crystals. The clay surface turns to be flat and slippery after adsorption. The Langmuir model shows the best fit for Cd(II) and Pb(II) data, while Freundlich model is more suitable for As(V) and Cr(VI). The optimum solid-solution ratios for sorption of Cd(II), Pb(II), As(V), and Cr(VI) are 15, 6, 40, and 40 g L-1, respectively. The optimum pHs for Cd(II), Pb(II), As(V), and Cr(VI) adsorption are 9.0, 6.0, 7.0, and 2.0, respectively. The pseudo-second-order kinetic is found to be the dominant sorption mechanism of these four ions on SSC. For Cd(II) and Pb(II), both particle diffusion and film diffusion are rate-limiting factors, whereas for As(V) and Cr(VI), intraparticle diffusion is the rate-controlling factor. The thermodynamic analysis reveals that the adsorption of Cd(II) and Pb(II) is spontaneous and endothermic and the system disorder increases, while adsorption of As(V) and Cr(VI) is exothermic and the system disorder decreases. Compared with most clay minerals, natural SSC exhibits comparable adsorption capacity and thus can potentially be used as a landfill liner material to retard the migration of heavy metals.


Asunto(s)
Cadmio , Contaminantes Químicos del Agua , Adsorción , China , Cromo , Arcilla , Monitoreo del Ambiente , Concentración de Iones de Hidrógeno , Cinética , Plomo , Termodinámica , Contaminantes Químicos del Agua/análisis
2.
Int J Mol Sci ; 22(3)2021 Jan 30.
Artículo en Inglés | MEDLINE | ID: mdl-33573283

RESUMEN

The synthesis of α-fluorinated methyl ketones has always been challenging. New methods based on the homologation chemistry via nucleophilic halocarbenoid transfer, carried out recently in our labs, allowed us to design and synthesize a target-directed dipeptidyl α,α-difluoromethyl ketone (DFMK) 8 as a potential antiviral agent with activity against human coronaviruses. The ability of the newly synthesized compound to inhibit viral replication was evaluated by a viral cytopathic effect (CPE)-based assay performed on MCR5 cells infected with one of the four human coronaviruses associated with respiratory distress, i.e., hCoV-229E, showing antiproliferative activity in the micromolar range (EC50 = 12.9 ± 1.22 µM), with a very low cytotoxicity profile (CC50 = 170 ± 3.79 µM, 307 ± 11.63 µM, and 174 ± 7.6 µM for A549, human embryonic lung fibroblasts (HELFs), and MRC5 cells, respectively). Docking and molecular dynamics simulations studies indicated that 8 efficaciously binds to the intended target hCoV-229E main protease (Mpro). Moreover, due to the high similarity between hCoV-229E Mpro and SARS-CoV-2 Mpro, we also performed the in silico analysis towards the second target, which showed results comparable to those obtained for hCoV-229E Mpro and promising in terms of energy of binding and docking pose.


Asunto(s)
Antivirales/química , Coronavirus Humano 229E/metabolismo , Dipéptidos/química , Cetonas/química , Células A549 , Antivirales/farmacología , Sitios de Unión , /virología , Línea Celular , /metabolismo , Humanos , Simulación del Acoplamiento Molecular , Simulación de Dinámica Molecular , /metabolismo , Termodinámica , Proteínas de la Matriz Viral/química , Proteínas de la Matriz Viral/metabolismo , Replicación Viral/efectos de los fármacos
3.
Commun Biol ; 4(1): 228, 2021 02 15.
Artículo en Inglés | MEDLINE | ID: mdl-33589648

RESUMEN

SARS-CoV-2 has been mutating since it was first sequenced in early January 2020. Here, we analyze 45,494 complete SARS-CoV-2 geneome sequences in the world to understand their mutations. Among them, 12,754 sequences are from the United States. Our analysis suggests the presence of four substrains and eleven top mutations in the United States. These eleven top mutations belong to 3 disconnected groups. The first and second groups consisting of 5 and 8 concurrent mutations are prevailing, while the other group with three concurrent mutations gradually fades out. Moreover, we reveal that female immune systems are more active than those of males in responding to SARS-CoV-2 infections. One of the top mutations, 27964C > T-(S24L) on ORF8, has an unusually strong gender dependence. Based on the analysis of all mutations on the spike protein, we uncover that two of four SASR-CoV-2 substrains in the United States become potentially more infectious.


Asunto(s)
/virología , Mutación/genética , /genética , Regiones no Traducidas 5'/genética , Secuencia de Aminoácidos , /metabolismo , Evolución Molecular , Femenino , Humanos , Masculino , Modelos Moleculares , Nucleocápside/metabolismo , Sistemas de Lectura Abierta/genética , Polimorfismo de Nucleótido Simple/genética , Unión Proteica , Dominios Proteicos , Pliegue de Proteína , Glicoproteína de la Espiga del Coronavirus/química , Glicoproteína de la Espiga del Coronavirus/genética , Termodinámica , Estados Unidos
4.
Water Sci Technol ; 83(3): 622-630, 2021 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-33600366

RESUMEN

Aspergillus parasiticus (A. parasiticus) CBS 100926T was used as a biosorbent for the removal of Methylene Blue (MB), Congo Red (CR), Sudan Black (SB), Malachite Green Oxalate (MGO), Basic Fuchsin (BF) and Phenol Red (PR) from aqueous solutions. The batch biosorption studies were carried out as a function of dye concentration and contact time. The biosorption process followed the pseudo-first-order and the pseudo-second-order kinetic models and the Freundlich and Langmuir isotherm models. The resulting biosorbent was characterized by Scanning Electron Microscopy (SEM), X-Ray Diffractometer and Fourier Transformer Infrared Spectroscopy (FTIR) techniques. The results of the present investigation suggest that A. parasiticus can be used as an environmentally benign and low cost biomaterial for the removal of basic and acid dyes from aqueous solution.


Asunto(s)
Colorantes , Contaminantes Químicos del Agua , Adsorción , Aspergillus , Biomasa , Concentración de Iones de Hidrógeno , Cinética , Espectroscopía Infrarroja por Transformada de Fourier , Termodinámica
5.
Water Sci Technol ; 83(3): 701-714, 2021 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-33600373

RESUMEN

In this study, we investigated the production conditions of Quercus coccifera hydrochar, which is an inexpensive and easy available adsorbent, for the adsorption of Basic Red 18 (BR18) azo dye. The hydrochar was produced in the eco-friendly subcritical water medium (SWM). The effects of the pH (2-10), adsorbent size (45-106 µm), adsorbent dose (0.5-1.5 g/L), dye concentration (40-455 mg/L), and contact time (5-120 min) were studied via optimization experiments. The optimum conditions were pH 10, particle size of 45 µm, particle amount of 1.5 g/L, dye concentration of 455 mg/L, and 60 min. The removal efficiency increased sharply for the first 5 min; after that the removal efficiency reached a steady state at 60 min, with a maximum removal of 88.7%. The kinetic studies for the adsorption of BR18 dye in aqueous solution using hydrochar showed pseudo-second-order kinetics. The Langmuir and Freundlich isotherm models were used to explain the relationship between adsorbent and adsorbate, and Freundlich isotherm was the most suitable model because of its high regression coefficient (R2) value. The intraparticle diffusion model was used to determine the adsorption mechanism of BR18 onto Q. coccifera acorn hydrochar. Desorption studies were also carried out using different types of acid and different molarities.


Asunto(s)
Quercus , Contaminantes Químicos del Agua , Adsorción , Colorantes , Concentración de Iones de Hidrógeno , Cinética , Termodinámica , Agua
6.
Sci Rep ; 11(1): 1156, 2021 01 13.
Artículo en Inglés | MEDLINE | ID: mdl-33441985

RESUMEN

Several viruses of the corona family interact, via their spike (S) proteins, with human cellular receptors. Spike proteins of SARS-CoV-1 and SARS-CoV-2 virions, being structurally related but not identical, mediate attachment to the human angiotensin-converting enzyme 2 (hACE2) receptor in similar but non-identical ways. Molecular-level understanding of interactions between spike proteins and hACE2 can aid strategies for blocking attachment of SARS-CoV-1, a potentially reemerging health threat, to human cells. We have identified dominant molecular-level interactions, some attractive and some repulsive, between the receptor binding domain of SARS-CoV-1 spike proteins (S-RBD) and hACE2. We performed fragment-based quantum-biochemical calculations which directly relate biomolecular structure to the hACE2...S-RBD interaction energy. Consistent with X-ray crystallography and cryo-EM, the interaction energy between hACE2 and S-RBD ([Formula: see text]26 kcal/mol) corresponds to a net intermolecular attraction which is significantly enhanced by inclusion of dispersion van der Waals forces. Protein fragments at the hACE2...S-RBD interface, that dominate host-virus attraction, have been identified together with their constituent amino acid residues. Two hACE2 fragments which include residues (GLU37, ASP38, TYR41, GLN42) and (GLU329, LYS353, GLY354), respectively, as well as three S-RBD fragments which include residues (TYR436), (ARG426) and (THR487, GLY488, TYR491), respectively, have been identified as primary attractors at the hACE2...S-RBD interface.


Asunto(s)
/química , Glicoproteína de la Espiga del Coronavirus/química , Glicoproteína de la Espiga del Coronavirus/metabolismo , Humanos , Modelos Moleculares , Unión Proteica , Conformación Proteica , Termodinámica
7.
Nat Commun ; 12(1): 120, 2021 01 05.
Artículo en Inglés | MEDLINE | ID: mdl-33402698

RESUMEN

Mitochondrial ATP synthase plays a key role in inducing membrane curvature to establish cristae. In Apicomplexa causing diseases such as malaria and toxoplasmosis, an unusual cristae morphology has been observed, but its structural basis is unknown. Here, we report that the apicomplexan ATP synthase assembles into cyclic hexamers, essential to shape their distinct cristae. Cryo-EM was used to determine the structure of the hexamer, which is held together by interactions between parasite-specific subunits in the lumenal region. Overall, we identified 17 apicomplexan-specific subunits, and a minimal and nuclear-encoded subunit-a. The hexamer consists of three dimers with an extensive dimer interface that includes bound cardiolipins and the inhibitor IF1. Cryo-ET and subtomogram averaging revealed that hexamers arrange into ~20-megadalton pentagonal pyramids in the curved apical membrane regions. Knockout of the linker protein ATPTG11 resulted in the loss of pentagonal pyramids with concomitant aberrantly shaped cristae. Together, this demonstrates that the unique macromolecular arrangement is critical for the maintenance of cristae morphology in Apicomplexa.


Asunto(s)
Mitocondrias/ultraestructura , Membranas Mitocondriales/ultraestructura , ATPasas de Translocación de Protón Mitocondriales/química , Subunidades de Proteína/química , Proteínas Protozoarias/química , Toxoplasma/ultraestructura , Sitios de Unión , Cardiolipinas/química , Cardiolipinas/metabolismo , Microscopía por Crioelectrón , Expresión Génica , Mitocondrias/genética , Mitocondrias/metabolismo , Membranas Mitocondriales/metabolismo , ATPasas de Translocación de Protón Mitocondriales/genética , ATPasas de Translocación de Protón Mitocondriales/metabolismo , Modelos Moleculares , Unión Proteica , Conformación Proteica en Hélice alfa , Conformación Proteica en Lámina beta , Dominios y Motivos de Interacción de Proteínas , Multimerización de Proteína , Subunidades de Proteína/genética , Subunidades de Proteína/metabolismo , Proteínas/química , Proteínas/genética , Proteínas/metabolismo , Proteínas Protozoarias/genética , Proteínas Protozoarias/metabolismo , Especificidad por Sustrato , Termodinámica , Toxoplasma/genética , Toxoplasma/metabolismo
8.
Water Sci Technol ; 83(1): 52-62, 2021 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-33460406

RESUMEN

The current study reports a systematic methodology of Zea mays L. (sweet corn) cobs (ZMLC) for the sequestration of synthetic dye (gentian violet) from aqueous solutions. Adsorbent was scrutinized by using scanning electron microscopy, Fourier transform infra-red spectrometry with pHpzc determination. The impact of various adsorption parameters including pH effect, ZMLC (sorbent) dosage, temperature, concentration and shaking time was examined. The equilibrium sorption isotherms were determined by the batch method from 283 to 303 K at pHpzc. Adsorption data were adjusted to four isothermal models: Langmuir, Freundlich, Dubinin-Radushkevich and Temkin's models, which presented the best adjustment to Freundlich, Dubinin-Radushkevich and Temkin's at 283 K. The kinetic profile fitted well to the pseudo-second order kinetic equation at three distinct concentrations 600, 700, 800 mg/L. Maximum sorption capacity was gained up to 700 mg.g-1 for gentian violet at pH 3, respectively. The adsorption process is endothermic, non-spontaneous, favorable thermodynamically due to positive values of entropy and Gibbs free energy and randomness decreases during the adsorption process. Furthermore, after biosorption onto ZMLC the dye can be desorbed effectively by using mineral base KOH solution. Consequently, the ZMLC is said to be a promising biosorbent to remediate gentian violet-contaminated water as well as wastewater.


Asunto(s)
Contaminantes Químicos del Agua , Zea mays , Adsorción , Violeta de Genciana , Concentración de Iones de Hidrógeno , Cinética , Espectroscopía Infrarroja por Transformada de Fourier , Termodinámica , Agua
9.
Water Sci Technol ; 83(1): 111-122, 2021 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-33460411

RESUMEN

Adsorption efficiency of acid-modified kola nut husk (KNHA) as a non-conventional adsorbent for the sorption of Ibuprofen from aqueous media was investigated in this study. The raw and modified samples were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, electron dispersive X-ray spectroscopy pH, and Boehm titration techniques respectively. Adsorption parameters such as pH effect, adsorbate concentration, contact time, and solution temperature were studied. The amount of Ibuprofen uptake was observed to increase with a corresponding increase in adsorption operational parameters. The kinetic data was found to best fit the pseudo-second-order kinetic model. Isotherm adsorption models of Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich were utilized to analyze the adsorption data. The Langmuir isotherm model showed the best fit for experimental data with a maximum monolayer adsorption capacity of 39.22 mg/g. The values of Gibbs free energy change were negative (-164.48 to -64.045.4 kJ/mol) suggesting that the process of ibuprofen adsorption onto KNHA was spontaneous. The positive value of standard enthalpy change (+34.203 kJ/mol) suggests that the process of ibuprofen adsorption was endothermic. KNHA adsorbent was found to be efficient and viable for the uptake of ibuprofen from aqueous medium. Hence, adsorbent prepared from kola nut husk waste has proved to be effective for the adsorptive uptake of Ibuprofen from aqueous media.


Asunto(s)
Ibuprofeno , Contaminantes Químicos del Agua , Adsorción , Concentración de Iones de Hidrógeno , Cinética , Espectroscopía Infrarroja por Transformada de Fourier , Temperatura , Termodinámica
10.
Water Sci Technol ; 83(1): 137-151, 2021 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-33460413

RESUMEN

In this study, the microporous metal organic framework-5 (MOF-5) has been synthesized to be used to remove methyl orange by adsorption. The adsorption experiments exhibit a good adsorption capacity at a catalyst dose of 0.1 g L-1 and for an initial concentration of 200 mg L-1, whereas the performance is stable over a wide pH range. The equilibrium adsorption data showed a sigmoidal course, which is well fitted by the Dubinin-Astakhov model applicable for physical adsorption processes (E = 0.055 kJ mol-1) onto heterogeneous surfaces and a more homogeneous pore structure (n = 9.9), with a maximum adsorption capacity of 1248.35 mg g-1. As can be observed from the evaluation of the kinetic data, the surface of the adsorbent is heterogeneous with different active sites for methyl orange (MO) adsorption. Moreover, based on the rate constant, it can be suggested that there is a specific interaction like electrostatic interaction between MO and the adsorbent for rapid and high uptake of the dye, whereas the adsorption phenomenon is reversible. According to the adsorption mechanisms, intra-particle and film diffusion models simultaneously controlled the rate sorption, which was confirmed by the calculated intra-particle diffusion and the film diffusion coefficients. The evaluation of the thermodynamic parameters revealed that the MO adsorption is spontaneous, endothermic and the randomness increases with the adsorption of MO.


Asunto(s)
Contaminantes Ambientales , Estructuras Metalorgánicas , Adsorción , Concentración de Iones de Hidrógeno , Cinética , Termodinámica
11.
AAPS PharmSciTech ; 22(1): 21, 2021 Jan 03.
Artículo en Inglés | MEDLINE | ID: mdl-33389277

RESUMEN

In order to better explain and predict the dissolution characteristics of binary drug delivery systems (BDDSs), the dissolution behaviors of co-crystal (CC) and co-amorphous (CA) systems of sacubitril (SCB) and valsartan (VST) were evaluated in vitro and in vivo by thermodynamic and kinetic methods. The CCs of SCB and VST were prepared into a CA state through rotary evaporation. Solid-state properties were systematically evaluated. Herein, based on the results from previous studies of single-phase systems, we used thermodynamic methods to evaluate the increase in drug dissolution rate after BDDSs change from the crystalline to the amorphous state. After comparing the predicted and measured dissolution rate enhancement of the CC and CA systems, this paper attempts to explain the dissolution rate characteristics of the BDDSs. We then evaluated the bioavailability of two BDDSs in beagle dogs to confirm that there was no discrepancy in vivo with the results obtained in vitro. The results exhibited that there is strong intermolecular interaction between SCB and VST and good physical stability for the CA system. Compared with the CC, the bioavailability of SCB and VST in the CA system increased by 313.9% and 130.5%, respectively. The predicted dissolution rate ratio between CC and CA systems and their actual intrinsic dissolution rates differed by only a factor of 2.5, demonstrating the good correlation between the predicted and measured values. In the future, this method could be expanded to a variety of new samples and exciting drug prospects.


Asunto(s)
Aminobutiratos/administración & dosificación , Antagonistas de Receptores de Angiotensina/administración & dosificación , Antihipertensivos/administración & dosificación , Sistemas de Liberación de Medicamentos , Tetrazoles/administración & dosificación , Termodinámica , Valsartán/administración & dosificación , Aminobutiratos/química , Aminobutiratos/farmacocinética , Antagonistas de Receptores de Angiotensina/química , Antagonistas de Receptores de Angiotensina/farmacocinética , Animales , Antihipertensivos/química , Antihipertensivos/farmacocinética , Disponibilidad Biológica , Perros , Combinación de Medicamentos , Estabilidad de Medicamentos , Cinética , Preparaciones Farmacéuticas , Difracción de Polvo , Solubilidad , Tetrazoles/química , Tetrazoles/farmacocinética , Valsartán/química , Valsartán/farmacocinética
12.
Commun Biol ; 4(1): 123, 2021 01 27.
Artículo en Inglés | MEDLINE | ID: mdl-33504944

RESUMEN

The macro domain is an ADP-ribose (ADPR) binding module, which is considered to act as a sensor to recognize nicotinamide adenine dinucleotide (NAD) metabolites, including poly ADPR (PAR) and other small molecules. The recognition of macro domains with various ligands is important for a variety of biological functions involved in NAD metabolism, including DNA repair, chromatin remodeling, maintenance of genomic stability, and response to viral infection. Nevertheless, how the macro domain binds to moieties with such structural obstacles using a simple cleft remains a puzzle. We systematically investigated the Middle East respiratory syndrome-coronavirus (MERS-CoV) macro domain for its ligand selectivity and binding properties by structural and biophysical approaches. Of interest, NAD, which is considered not to interact with macro domains, was co-crystallized with the MERS-CoV macro domain. Further studies at physiological temperature revealed that NAD has similar binding ability with ADPR because of the accommodation of the thermal-tunable binding pocket. This study provides the biochemical and structural bases of the detailed ligand-binding mode of the MERS-CoV macro domain. In addition, our observation of enhanced binding affinity of the MERS-CoV macro domain to NAD at physiological temperature highlights the need for further study to reveal the biological functions.


Asunto(s)
Coronavirus del Síndrome Respiratorio de Oriente Medio/química , Coronavirus del Síndrome Respiratorio de Oriente Medio/metabolismo , NAD/metabolismo , Proteínas Virales/química , Proteínas Virales/metabolismo , Adenosina Difosfato Ribosa/metabolismo , Sitios de Unión , Fenómenos Biofísicos , Cristalización , Cristalografía por Rayos X , Humanos , Ligandos , Modelos Moleculares , Resonancia Magnética Nuclear Biomolecular , Poli Adenosina Difosfato Ribosa/metabolismo , Unión Proteica , Dominios Proteicos , Estabilidad Proteica , Termodinámica
13.
Nucleic Acids Res ; 49(2): 713-725, 2021 01 25.
Artículo en Inglés | MEDLINE | ID: mdl-33406227

RESUMEN

We report a series of synthetic, nucleic acid mimics with highly customizable thermodynamic binding to DNA. Incorporation of helix-promoting cyclopentanes into peptide nucleic acids (PNAs) increases the melting temperatures (Tm) of PNA+DNA duplexes by approximately +5°C per cyclopentane. Sequential addition of cyclopentanes allows the Tm of PNA + DNA duplexes to be systematically fine-tuned from +5 to +50°C compared with the unmodified PNA. Containing only nine nucleobases and an equal number of cyclopentanes, cpPNA-9 binds to complementary DNA with a Tm around 90°C. Additional experiments reveal that the cpPNA-9 sequence specifically binds to DNA duplexes containing its complementary sequence and functions as a PCR clamp. An X-ray crystal structure of the cpPNA-9-DNA duplex revealed that cyclopentanes likely induce a right-handed helix in the PNA with conformations that promote DNA binding.


Asunto(s)
Ciclopentanos/química , ADN/metabolismo , Conformación de Ácido Nucleico , Ácidos Nucleicos de Péptidos/química , Calorimetría , Dicroismo Circular , Cristalografía por Rayos X , Ciclopentanos/metabolismo , Modelos Moleculares , Desnaturalización de Ácido Nucleico , Ácidos Nucleicos de Péptidos/metabolismo , Reacción en Cadena en Tiempo Real de la Polimerasa , Espectrofotometría Ultravioleta , Termodinámica , Temperatura de Transición
14.
Phys Chem Chem Phys ; 23(2): 1706-1717, 2021 Jan 21.
Artículo en Inglés | MEDLINE | ID: mdl-33427255

RESUMEN

The use of water as a component of deep eutectic systems (DES) has raised some questions regarding its influence on the nature of the mixture. Does it form a DES or an aqueous solution and what is the role of water? In this work, the nature of citric acid:l-arginine:water mixtures was explored through phase equilibria studies and spectroscopic analysis. In a first step, PC-SAFT was validated as a predictive tool to model the water influence on the solid liquid equilibria (SLE) of the DES reline using the individual-component approach. Hence, activity coefficients in the ternary systems citric acid:l-arginine:water and respective binary combinations were studied and compared using ePC-SAFT. It was observed that the water-free mixtures citric acid:l-arginine showed positive deviation from Raoult's law, while upon addition of water strong negative deviation from Raoult's law was found, yielding melting depressions around 100 K. Besides these strong interactions, pH was found to become acidic (pH = 3.5) upon water addition, which yields the formation of charged species ([H2Cit]- and [l-arg]+). Thus, the increased interactions between the molecules upon water addition might be caused by several mechanisms such as hydrogen bonding or ionic forces, both being induced by water. For further investigation, the liquid mixtures citric acid:l-arginine:water were studied by FTIR and NMR spectroscopy. FTIR spectra disproved a possible solubility enhancement caused by salt formation between citric acid and l-arginine, while NMR spectra supported the formation of a hydrogen bonding network different from the binary systems citric acid:water and l-arginine:water. Either being a DES or other type of non-ideal solution, the liquefaction of the studied systems is certainly caused by a water-mediator effect based on the formation of charged species and cross interactions between the mixture constituents.


Asunto(s)
Arginina/química , Ácido Cítrico/química , Agua/química , Cloruro de Calcio/química , Congelación , Modelos Químicos , Termodinámica , Temperatura de Transición , Urea/química
15.
Phys Chem Chem Phys ; 23(3): 2025-2037, 2021 Jan 28.
Artículo en Inglés | MEDLINE | ID: mdl-33469639

RESUMEN

The anti-apoptotic proteins B-cell lymphoma-extra large (Bcl-xL) and B-cell lymphoma/leukemia-2 (Bcl-2) are members of the Bcl-2 protein family, and they play important roles in regulating apoptosis and cell cycle retardation. However, the binding mechanisms of Bcl-xL/Bcl-2 with their associated agonists, including Bcl-2-associated death promoter (Bad) and Bcl-2-associated X protein (Bax), are not well understood. In the present study, the recently developed interaction entropy approach was employed for the calculation of entropic contribution, and the computational alanine scanning method was used to identify the hot spot in the protein-protein interactions between Bcl-xL/Bcl-2 and Bad/Bax. The calculated binding free energies and their ranks for the four systems were in good agreement with the experimental results. Computational analysis shows that there are more hot-spot residues in the Bcl-xL/Bad complex than that in the Bcl-xL/Bax complex, leading to a stronger binding affinity in the former. It is interesting to find that the reason for the stronger binding affinity of Bcl-2 to Bad than to Bax is different for the Bcl-xL system. Although there are more hot-spot residues in the Bcl-2/Bax system than in the Bcl-2/Bad complex, there are also more negatively contributing residues in the Bcl-2/Bax. Our study identified Arg104, Tyr105, Leu116, and Leu134 to be the common key residues in the Bcl-xL complexes, and Arg107, Tyr108, Phe112, Gln118, Leu137, Arg146, and Tyr202 are common key residues in the Bcl-2 complexes. These results would provide valuable information for the design of potent inhibitors of Bcl-xL/Bcl-2.


Asunto(s)
Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Proteína X Asociada a bcl-2/metabolismo , Proteína Letal Asociada a bcl/metabolismo , Proteína bcl-X/metabolismo , Animales , Sitios de Unión , Humanos , Ratones , Simulación de Dinámica Molecular , Unión Proteica , Proteínas Proto-Oncogénicas c-bcl-2/química , Termodinámica , Proteína X Asociada a bcl-2/química , Proteína Letal Asociada a bcl/química , Proteína bcl-X/química
16.
Phys Chem Chem Phys ; 23(3): 2015-2024, 2021 Jan 28.
Artículo en Inglés | MEDLINE | ID: mdl-33469642

RESUMEN

A computational methodology that couples the acidity (Ka) and density functional theory (DFT) calculations has been developed to explain the pH-dependent drug loading on and releasing from mesoporous silica nanoparticles. The model has been validated by investigating the pH-dependent loading and releasing of a bisphosphonate drug molecule, alendronate, on a propylamine-modified quartz surface (101), a model for functionalized mesoporous silica nanoparticles. The pH-dependent interacting molecular species are the neutral and anionic forms of the drug molecule, silanol group of quartz surface and the functional group in the case of functionalized quartz surface. The interaction energies of all the molecular species of alendronate with silica surface are calculated by using the DFT-based CASTEP method. Five molecular states of alendronate (D0, D-, D2-, D3- and D4-), two for silica surface (S0 and S-) and two for propylamine (P+ and P0) are considered. Ten possible combinations of interactions of alendronate with silica surface and twenty for alendronate and propylamine-functionalized silica surfaces are calculated. The relative probability of interaction of a particular pair of drug and surface combination at a particular pH is weighed by the product of their fractions, the latter is calculated by using the Handerson-Hasselbach equation. The total interaction energies at a particular pH are calculated by summing the possible individual interaction energies. The variation of total interaction energy with pH shows that the functional group of propylamine lowers the interaction energy at lower pH values (1-5), thus favouring adsorption or loading of the drug and increases the interaction energy at higher pH values (pH > 8) and thus favours desorption or release of the drug. This is in agreement with experimental results where it is shown that propylamine-functionalized mesoporous silica nanoparticles load alendronate in the pH range of 1-5 and release at pH = 8. This method can be used to predict the pH-dependent drug loading and releasing of a particular combination of drug and on a particular drug delivery system.


Asunto(s)
Alendronato/química , Propilaminas/química , Cuarzo/química , Teoría Funcional de la Densidad , Sistemas de Liberación de Medicamentos , Liberación de Fármacos , Concentración de Iones de Hidrógeno , Modelos Químicos , Propiedades de Superficie , Termodinámica
17.
Food Chem ; 346: 128976, 2021 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-33476948

RESUMEN

This study was aimed to investigate the effect of incubation temperature on the binding of hexanal, octanal and 3-methylbutyraldehyde to myosin. Fluorescence quenching, Fourier transform infrared spectroscopy, surface plasmon resonance (SPR), isothermal titration calorimetry (ITC) and gas chromatography-mass spectrometry (GC-MS) were employed. An increase in aldehyde concentration led to a reduction in fluorescence intensity in myosin. SPR revealed that the interactions were involved in a rapid combination and dissociation, and the dissociation constants significantly decreased from 25 to 37 °C. ITC showed that the values of entropy, enthalpy and Gibbs free energy were negative. The interactions were driven by hydrogen bonds and van der Waals forces. GC-MS further demonstrated that the highest binding capacity occurred at 37 °C between myosin and aldehydes. The findings provide a new insight into the mechanism on controlling or maintaining meat flavor.


Asunto(s)
Aromatizantes/química , Miosinas/química , Calorimetría , Aromatizantes/metabolismo , Cromatografía de Gases y Espectrometría de Masas , Enlace de Hidrógeno , Miosinas/metabolismo , Unión Proteica , Espectrometría de Fluorescencia , Electricidad Estática , Temperatura , Termodinámica
18.
Nat Commun ; 12(1): 548, 2021 01 22.
Artículo en Inglés | MEDLINE | ID: mdl-33483497

RESUMEN

Actin polymerization provides force for vital processes of the eukaryotic cell, but our understanding of actin dynamics and energetics remains limited due to the lack of high-quality probes. Most current probes affect dynamics of actin or its interactions with actin-binding proteins (ABPs), and cannot track the bound nucleotide. Here, we identify a family of highly sensitive fluorescent nucleotide analogues structurally compatible with actin. We demonstrate that these fluorescent nucleotides bind to actin, maintain functional interactions with a number of essential ABPs, are hydrolyzed within actin filaments, and provide energy to power actin-based processes. These probes also enable monitoring actin assembly and nucleotide exchange with single-molecule microscopy and fluorescence anisotropy kinetics, therefore providing robust and highly versatile tools to study actin dynamics and functions of ABPs.


Asunto(s)
Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Proteínas de Microfilamentos/metabolismo , Proteínas Musculares/metabolismo , Nucleótidos/metabolismo , Actinas/química , Algoritmos , Animales , Polarización de Fluorescencia , Colorantes Fluorescentes/química , Hidrólisis , Cinética , Modelos Teóricos , Proteínas Musculares/química , Nucleótidos/química , Unión Proteica , Conejos , Termodinámica
19.
J Environ Manage ; 282: 111950, 2021 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-33465714

RESUMEN

Dissolved copper in stormwater runoff is a significant environmental problem. Biosorption of dissolved metals using microorganisms is known as a green, low-cost and efficient method. However, the role of live biological agents in the remediation of dissolved copper in Sustainable Drainage (SuDS) has not been reported. In this study, the effect of pH, initial concentration and temperature, on bacteria in different stages of biofilm development on a geotextile, along with Cu(II) removal efficiencies, were evaluated. Maximum Cu(II) removal efficiency (92%) was observed at pH 6. By decreasing the pH from 6 to 2, a log 5 reduction in bacteria was observed and Carboxyl groups transformed from -COO- to -COOH. The maximum biosorption capacity (119 mg g-1) was detected on day 1 of biofilm development, however, maximum removal efficiency (97%) was measured on day 21 of biofilm incubation. Exteracellular Polymeric Substance (EPS) showed a better protection of CFUs in more mature biofilms (day 21) with less than 0.1 log decrease when exposed to 200 mL-1 Cu(II), whereas, biofilm on day 1 of incubation showed a 2 log reduction in CFUs number. Thermodynamic studies showed that the maximum Cu(II) biosorption capacity of biofilms, incubated for 7 days (117 mg g-1) occurred at 35 °C. Thermodynamic and kinetic modelling of data revealed that a physical, feasible, spontaneous and exothermic process controlled the biosorption, with a diffusion process observed in external layers of the biofilm, fitting a pseudo-second order model. Equilibrium data modelling and high R2 values of Langmuir model indicated that the biosorption took place by a monolayer on the living biofilm surface in all stages of biofilm development.


Asunto(s)
Cobre , Contaminantes Químicos del Agua , Adsorción , Biopelículas , Concentración de Iones de Hidrógeno , Cinética , Termodinámica
20.
Sci Total Environ ; 765: 144253, 2021 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-33418333

RESUMEN

Extensive application of imidacloprid (IMI) in pest control and its undesirable removal efficiency enabled it to be a critical global challenge. Low cost, efficient, sustainable and environment-friendly technologies are urgently needed to be developed to remove IMI from water. A novel adsorbent of potassium hydroxide activated magnetic microporous loofah sponge biochar (KOH+Fe/Zn-LBC) was synthesized, as well as its adsorption capacity and mechanisms for IMI were investigated in this study. KOH+Fe/Zn-LBC had the superior pore structure (surface area and pore volume) and its maximum adsorption capacity for IMI could reach 738 mg g-1 at 298 K. Kinetics, isotherms, thermodynamics and characterization analysis suggested that pore filling, hydrogen bonding and π-π conjugation were its main adsorption mechanisms. Additionally, the thermodynamic parameters described that IMI adsorption was a spontaneous, endothermic and less random process. Particularly, the magnetic separation of KOH+Fe/Zn-LBC was beneficial for its reuse. Ultrasound and ethanol co-processing could effectively regenerate the used KOH+Fe/Zn-LBC and maintain its stable sustainable adsorption capacity (99.4% of its fresh adsorption capacity after five reuse cycles). Besides, KOH+Fe/Zn-LBC exhibited a stable adsorption capacity and environmental safety in a wide pH range. Therefore, KOH+Fe/Zn-LBC has the potential to be an efficient, green and sustainable adsorbent for neonicotinoids removal.


Asunto(s)
Luffa , Contaminantes Químicos del Agua , Adsorción , Carbón Orgánico , Concentración de Iones de Hidrógeno , Hidróxidos , Cinética , Fenómenos Magnéticos , Neonicotinoides , Nitrocompuestos , Compuestos de Potasio , Termodinámica , Contaminantes Químicos del Agua/análisis
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