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1.
J Phys Chem A ; 126(1): 3-15, 2022 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-34978833

RESUMO

Fluorinated carboxylic acids and their radicals are becoming more prevalent in environmental waters and soils as they have been produced and used for numerous commercial applications. Understanding the thermochemical properties of fluorinated carboxylic acids will provide insights into the stability and reaction paths of these molecules in the environment, in body fluids, and in biological and biochemical processes. Structures and thermodynamic properties for over 50 species related to fluorinated carboxylic acids with two and three carbons are determined with density functional computational calculations B3LYP, M06-2X, and MN15 and higher ab initio levels CBS-QB3, CBS-APNO, and G4 of theory. The lowest energy structures, moments of inertia, vibrational frequencies, and internal rotor potentials of each target species are determined. Standard enthalpies of formation, ΔfH298°, from CBS-APNO calculations show the smallest standard deviation among methods used in this work. ΔfH298° values are determined via several series of isodesmic and/or isogyric reactions. Enthalpies of formation are determined for fluorinated acetic and propionic acids and their respective radicals corresponding to the loss of hydrogen and fluorine atoms. Heat capacities as a function of temperature, Cp(T), and entropy at 298 K, S298°, are determined. Thermochemical properties for the fluorinated carbon groups used in group additivity are also developed. Bond dissociation energies (BDEs) for the carbon-hydrogen, carbon-fluorine, and oxygen-hydrogen (C-H, C-F, and O-H BDEs) in the acids are reported. The C-H, C-F, and O-H bond energies of the fluorinated carboxylic acids are in the range of 89-104, 101-125, and 109-113 kcal mol-1, respectively. General trends show that the O-H bond energies on the acid group increase with the increase in the fluorine substitution. The strong carbon fluorine bonds in a fluorinated acid support the higher stability of the perfluorinated acids in the environment.


Assuntos
Ácidos Carboxílicos , Temperatura Alta , Entropia , Termodinâmica
2.
Arch Microbiol ; 204(2): 128, 2022 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-34997859

RESUMO

Remazol Brilliant Blue R (RBBR) is a widely used carcinogenic and toxic dye. This study focused on RBBR dye removal using chemically modified and unmodified Yarrowia lipolytica biomass. RBBR dye biosorption studies were carried out as a function of pH, initial dye concentration, biosorbent dose, contact time, and temperature. The pH of the aqueous solution strongly influenced the biosorption percent of RBBR dye. The highest dye biosorption capacity yield was obtained at pH 2-3 range. It has been found that the adsorption capacity is quite low at higher pH values. No differences were found between chemically modified and unmodified biomass in terms of RBBR dye biosorption capacity. In the first 15 min, almost 50% RBBR dye was removed from the solution and reached equilibrium within180 min at pH 2. Biosorption isotherm obeyed Langmuir isotherm model and pseudo-second-order kinetic model.


Assuntos
Poluentes Químicos da Água , Yarrowia , Antraquinonas , Biomassa , Concentração de Íons de Hidrogênio , Cinética , Termodinâmica
3.
J Agric Food Chem ; 70(2): 656-668, 2022 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-34982560

RESUMO

The kinetics and thermodynamics of the pH-dependent reversible and irreversible processes leading to color fading of pelargonidin-3-O-glucoside, peonidin-3-O-glucoside, malvidin-3-O-glucoside, and cyanidin-3-O-glucoside dyes in aqueous solutions are reported. Following the addition of base to the flavylium cation, the quinoidal bases disappear by three distinct steps: (i) in an acidic medium by a biexponential process, in which the faster step is controlled by the hydration reaction and the slower one by cis-trans isomerization; the degradation process occurs essentially from the anionic quinoidal base; (ii) in a basic medium (pH > 9.5), in which the disappearance of the anionic bases is monoexponential, with the rate proportional to the hydroxyl concentration (hydroxyl attack), leading to anionic chalcones (cis and trans) at equilibrium─the slower degradation step occurs from the di- and trianionic chalcones; and (iii) in the pH region circa 7.7 < pH < 9.5, in which hydration and hydroxyl attacks are much slower than anionic quinoidal base degradation (which is the rate-controlling step) and the equilibrium cannot be attained.


Assuntos
Antocianinas , Chalcona , Concentração de Íons de Hidrogênio , Cinética , Termodinâmica
4.
Chemosphere ; 286(Pt 3): 131863, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34411928

RESUMO

Nanoplastic (NP) pollution is an emerging global concern due to its adverse impact on aquatic ecosystems. Nevertheless, the removal of aqueous NPs from aquatic environments remains a significant challenge. This study aims to investigate whether polystyrene NP in aqueous solutions can be removed using coffee grounds. Due to the difficulty associated with directly measuring NP levels and monitoring the biosorption process, we used fluorescent-orange amine-modified polystyrene beads (fluo-NP, 100 nm) to evaluate the efficacy of the biosorption process. The factors including pH, coffee grounds concentration, initial fluo-NP concentration, and contact time were optimized on batch experiments. In addition, the isotherm and kinetic models were employed to clarify the adsorption behaviors and mechanisms. It was found that aqueous fluo-NP particles were effectively adsorbed onto the coffee grounds over a wide pH range (pH 2-12), with a coffee ground concentration of 25 g/L leading to the maximum adsorption efficiency (74%). The equilibrium adsorption capacity of the coffee grounds was 4 mg/g for a reaction time of 40 min. Coffee grounds demonstrated the highest removal efficiency when the initial fluo-NP concentration was 100-125 mg/L. The Dubinin-Radushkevich model and pseudo-second-order model described the adsorption isotherm and kinetics well, respectively, and the adsorption at high fluo-NP concentration range was favorable. Moreover, the results suggest that the mechanism lies in the electrostatic interactions and hydrogen bonding between surface functional groups of the coffee grounds and the fluo-NP particles. Given that there is an urgent need to remove NPs from aqueous systems, this study illustrates that it is possible to use coffee ground biowaste for this purpose.


Assuntos
Café , Poluentes Químicos da Água , Adsorção , Ecossistema , Concentração de Íons de Hidrogênio , Cinética , Plásticos , Poliestirenos , Soluções , Termodinâmica , Poluentes Químicos da Água/análise
5.
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
6.
Chemosphere ; 286(Pt 3): 131938, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34426299

RESUMO

Magnetic activated charcoal/Fe2O3 nanocomposite (AC/Fe2O3NC) was fabricated using Spondias dulcis leaf extract by a facile method and used for the adsorptive removal of 2,4-Dichlorophenoxyacetic acid (2,4-D) from aqueous solutions for the first time. The nanocomposite was characterized by methods such as FE-SEM, EDS, XRD, FTIR, TGA, VSM, and BET to identify and confirm the surface morphology, elemental composition, crystalline nature, functional groups, thermal stability, magnetic behavior, and surface area respectively. Box-Behnken Design (BBD) - an optimization method, which belongs to the Response surface methodology (RSM) and a modeling tool - Artificial Neural Network (ANN) were employed to design, optimize and predict the relationship between the input parameters (pH, initial concentration of 2,4-D, time and agitation speed) versus the output parameter (adsorption efficiency of 2,4-D). Adsorption efficiency of 98.12% was obtained at optimum conditions (pH: 2.05, initial concentration: 32 ppm, contact time: 100 min, agitation speed: 130 rpm, temperature: 30 °C, and dosage: 0.2 g/L). The predictive ability of the ANN was superior (R2 = 0.99) than the quadratic model, given by the RSM (R2 = 0.93). The equilibrium data were best-fitted to Langmuir isotherm (R2 = 0.9944) and the kinetics obeyed pseudo-second-order model (R2 = 0.9993) satisfactorily. Thermodynamic studies revealed the spontaneity and exothermic nature of adsorption. The maximum adsorption capacity, qm was found to be 255.10 mg/g, substantially larger than the reported values for 2,4-D adsorption by other magnetic nanoadsorbents. Therefore, this nanoadsorbent may be utilized as an excellent alternative for the elimination of 2,4-D from the waterbodies.


Assuntos
Nanocompostos , Poluentes Químicos da Água , Ácido 2,4-Diclorofenoxiacético , Adsorção , Carvão Vegetal , Concentração de Íons de Hidrogênio , Cinética , Fenômenos Magnéticos , Termodinâmica , Poluentes Químicos da Água/análise
7.
J Environ Manage ; 301: 113854, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34607141

RESUMO

Insights into thermal degradation behaviour, kinetics, reaction mechanism, possible synergism, and thermodynamic analysis of co-pyrolysis of carbonaceous materials are crucial for efficient design of co-pyrolysis reactor systems. Present study deals with comprehensive kinetics and thermodynamic investigation of co-pyrolysis of petroleum coke (PC) and banana leaves biomass (BLB) for realizing the co-pyrolysis potential. Thermogravimetric non-isothermal studies have been performed at 10, 20, and 30 °C/min heating rates. Synergistic effect between PC and BLB was determined by Devolatilization index (Di) and mass loss method. Kinetic parameters were estimated using seven model-free methods. Standard activation energy for PC + BLB blend from FWO, KAS, Starink, and Vyazovkin methods was ≈165 kJ/mol and that from Friedman and Vyazovkin advanced isoconversional methods was ≈171 kJ/mol. The frequency factor calculated for the blend from Kissinger method was found to be in the range of 106-1016s-1. Devolatilization index (Di) showed synergistic effect of blending. The data pertaining to co-pyrolysis was found to fit well with R2 (second order) and D3 (three dimensional) from Z(α) master plot. Thermodynamic parameters, viz. ΔH ≈ 163 kJ/mol and ΔG ≈ 151 kJ/mol were calculated to determine the feasibility and reactivity of the co-pyrolysis process. The results are expected to be useful in the design of petcoke and banana leaves biomass co-pyrolysis systems.


Assuntos
Coque , Musa , Petróleo , Biomassa , Cinética , Folhas de Planta , Pirólise , Termodinâmica , Termogravimetria
8.
Sci Total Environ ; 806(Pt 4): 150885, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34634354

RESUMO

Seasonal algal blooms in surface water release a significant amount of algal organic matter (AOM), which alters the composition of dissolved organic matter (DOM). AOM affects the drinking water treatment processes and finished water quality. In this study, the relative removal efficiency of AOM and humic acid by granular activated carbon (GAC) adsorption was determined. Batch experiments were conducted to evaluate the adsorption capacity of GAC, which varied from 4.235-31.45 mg/g for AOM originated from different algae. Freundlich isotherm models fitted the adsorption equilibrium data, and the adsorption kinetics data were fitted well using a pseudo-second order kinetic model. The calculated thermodynamics parameters (∆G0, ∆H0 and ∆S0) indicated that GAC adsorption for DOM removal was endothermic and spontaneous in nature.


Assuntos
Carvão Vegetal , Poluentes Químicos da Água , Adsorção , Cinética , Termodinâmica , Poluentes Químicos da Água/análise
9.
J Colloid Interface Sci ; 608(Pt 1): 683-691, 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-34634544

RESUMO

Both, experimental and modelling evidence is presented in this study showing that interlayer anion exchange is the dominant sorption mechanism for iodide (I-) on AFm phases. AFm phases are Ca-Al(Fe) based layered double hydroxides (LDH) known for their large potential for the immobilization of anionic radionuclides, such as dose-relevant iodine-129, emanating from low- and intermediate-level radioactive waste (L/ILW) repositories. Monosulfate, sulfide-AFm, hemicarbonate and monocarbonate are safety-relevant AFm phases, expected to be present in the cementitious near-field of such repositories. Their ability to bind I- was investigated in a series of sorption and co-precipitation experiments. The sorption of I- on different AFm phases was found to depend on the type of the interlayer anion. Sorption Rd values are very similar for monosulfate, sulfide-AFm and hemicarbonate. A slightly higher uptake occurs by AFm phases with a singly charged anion in the interlayer (HS-AFm) as compared to AFm with divalent ions (monosulfate), whereas uptake by hemicarbonate is intermediate. No significant sorption occurs onto monocarbonate. Our derived thermodynamic solid solution models reproduce the experimentally obtained sorption isotherms on HS-AFm, hemicarbonate and monosulfate, indicating that anion exchange in the interlayer is the dominant mechanism and that the contribution of I- electrostatic surface sorption to the overall uptake is negligible.


Assuntos
Hidróxidos , Iodetos , Termodinâmica
10.
Methods Mol Biol ; 2376: 3-30, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34845601

RESUMO

The analysis of protein folding reactions by monitoring the kinetic effects of specifically designed single-point mutations, the so-termed phi-value analysis, has been a favorite technique to experimentally probe the mechanisms of protein folding. The idea behind phi-value analysis is that the effects that mutations have on the folding and unfolding rate constants report on the energetic/structural features of the folding transition state ensemble (TSE), which is the highest point in the free energy surface connecting the native and unfolded states, and thus the rate limiting step that ultimately defines the folding mechanism. For single-domain, two-state folding proteins, the general procedure to perform the phi-value analysis of protein folding is relatively simple to implement in the lab. Once the mutations have been produced and purified, the researcher needs to follow a few specific guidelines to perform the experiments and to analyze the data so produced. In this chapter, a step-by-step description of how to measure and interpret the effects induced by site-directed mutations on the folding and unfolding rate constants of a protein of interest is provided. Some possible solutions to the most typical problems that arise when performing phi-value analysis in the lab are also provided.


Assuntos
Dobramento de Proteína , Cinética , Mutação , Mutação Puntual , Conformação Proteica , Proteínas/genética , Termodinâmica
11.
Methods Mol Biol ; 2376: 31-63, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34845602

RESUMO

The formation of the transition state ensemble (TSE) represents the rate-limiting step in protein folding. The TSE is the least populated state on the pathway, and its characterization remains a challenge. Properties of the TSE can be inferred from the effects on folding and unfolding rates for various perturbations. A difficulty remains on how to translate these kinetic effects to structural properties of the TSE. Several factors can obscure the translation of point mutations in the frequently used method, "mutational Phi analysis." We take a complementary approach in "Psi analysis," employing rationally inserted metal binding sites designed to probe pairwise contacts in the TSE. These contacts can be confidently identified and used to construct structural models of the TSE. The method has been applied to multiple proteins and consistently produces a considerably more structured and native-like TSE than Phi analysis. This difference has significant implications to our understanding of protein folding mechanisms. Here we describe the application of the method and discuss how it can be used to study other conformational transitions such as binding.


Assuntos
Dobramento de Proteína , Sítios de Ligação , Cinética , Domínios Proteicos , Proteínas/genética , Termodinâmica
12.
Methods Mol Biol ; 2376: 105-116, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34845605

RESUMO

Protein folding/unfolding processes involve a large number of weak, non-covalent interactions and are more appropriately described in terms of the movement of a point representing protein conformation in a plot of internal free energy versus conformational degrees of freedom. While these energy landscapes have an astronomically large number of dimensions, it has been shown that many relevant aspects of protein folding can be understood in terms of their projections onto a few relevant coordinates. Remarkably, such low-dimensional free energy surfaces can be obtained from experimental DSC data using suitable analytical models. Here, we describe the experimental procedures to be used to obtain the high-quality DSC data that are required for free-energy surface analysis.


Assuntos
Varredura Diferencial de Calorimetria , Calorimetria , Conformação Proteica , Dobramento de Proteína , Termodinâmica
13.
Methods Mol Biol ; 2376: 173-185, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34845610

RESUMO

Theory and experimental evidence unequivocally indicate that protein folding is far more complex than the two-state (all-or-none) model that is usually assumed in the analysis of folding experiments. Proteins tend to fold hierarchically by forming secondary structure elements, followed by supersecondary arrangements, and other intermediate states that ultimately adopt the native tertiary fold as a result of a delicate balance between interatomic interactions and entropic contributions. However, small proteins with simple folds typically follow downhill folding, characterized by very small energetic barriers (<3 RT) that allow multiple protein conformations to be populated along the folding path down the free energy landscape, reaching the native fold at the lowest energy level.Here we describe the use of solution-state nuclear magnetic resonance (NMR) for the analysis of protein folding interaction networks at atomic resolution. The assignment of NMR spectra acquired at different unfolding conditions provides hundreds of atomic unfolding curves that are analyzed to infer the network of folding interactions. The method is particularly useful to study small proteins that fold autonomously in the sub-millisecond timescale. The information obtained from the application of this method can potentially unveil the basic relationships between protein structure and folding.


Assuntos
Dobramento de Proteína , Entropia , Cinética , Ressonância Magnética Nuclear Biomolecular , Conformação Proteica , Estrutura Secundária de Proteína , Proteínas , Termodinâmica
14.
Methods Mol Biol ; 2376: 303-315, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34845616

RESUMO

Computational coarse-grained models play a fundamental role as a research tool in protein folding, and they are important in bridging theory and experiments. Folding mechanisms are generally discussed using the energy landscape framework, which is well mapped within a class of simplified structure-based models. In this chapter, simplified computer models are discussed with special focus on structure-based ones.


Assuntos
Dobramento de Proteína , Simulação por Computador , Simulação de Dinâmica Molecular , Termodinâmica
15.
Methods Mol Biol ; 2376: 365-372, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34845620

RESUMO

Large differences exist between the experimentally measured folding and unfolding rates in single-domain proteins, which range from seconds to microseconds. Considerable effort has been dedicated to develop methods for the prediction of these rates using a simple set of rules. Much of this work has focused in identifying structural metrics derived from experimentally resolved protein structures that serve as good predictors of folding rates. An alternative to this ad-hoc methodology is the use of phenomenological free energy models, parametrized with empirical parameters. This alternative approach has become very useful to obtain estimates of folding and, importantly, also unfolding rates with only the information of protein size and secondary structure. Here we present the fundamentals of this type of approach and introduce a recent implementation of this predictive method.


Assuntos
Dobramento de Proteína , Proteínas/química , Cinética , Modelos Moleculares , Estrutura Secundária de Proteína , Termodinâmica
16.
Methods Mol Biol ; 2376: 373-386, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34845621

RESUMO

Mutational perturbations of protein structures, i.e., phi-value analysis, are commonly employed to probe the extent of involvement of a particular residue in the rate-determining step(s) of folding. This generally involves the measurement of folding thermodynamic parameters and kinetic rate constants for the wild-type and mutant proteins. While computational approaches have been reasonably successful in understanding and predicting the effect of mutations on folding thermodynamics, it has been challenging to explore the same on kinetics due to confounding structural, energetic, and dynamic factors. Accordingly, the frequent observation of fractional phi-values (mean of ~0.3) has resisted a precise and consistent interpretation. Here, we describe how to construct, parameterize, and employ a simple one-dimensional free energy surface model that is grounded in the basic tenets of the energy landscape theory to predict and simulate the effect of mutations on folding kinetics. As a proof of principle, we simulate one-dimensional free energy profiles of 806 mutations from 24 different proteins employing just the experimental destabilization as input, reproduce the relative unfolding activation free energies with a correlation of 0.91, and show that the mean phi-value of 0.3 essentially corresponds to the extent of stabilization energy gained at the barrier top while folding.


Assuntos
Dobramento de Proteína , Cinética , Mutação , Proteínas/genética , Termodinâmica
17.
Methods Mol Biol ; 2376: 387-398, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34845622

RESUMO

We present a detailed heuristic method to quantify the degree of local energetic frustration manifested by protein molecules. Current applications are realized in computational experiments where a protein structure is visualized highlighting the energetic conflicts or the concordance of the local interactions in that structure. Minimally frustrated linkages highlight the stable folding core of the molecule. Sites of high local frustration, in contrast, often indicate functionally relevant regions such as binding, active, or allosteric sites.


Assuntos
Conformação Proteica , Modelos Moleculares , Dobramento de Proteína , Proteínas , Termodinâmica
18.
J Colloid Interface Sci ; 611: 39-45, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-34929437

RESUMO

One of the most intriguing aspects of zwitterionic surfactant micelles is their propensity to exhibit selectivity in the binding of the anions of added salts. In this work we examine the thermodynamics of the interaction of the strongly bound perchlorate ion and the more weakly bound bromide ion with micelles of N-tetradecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SB3-14) in aqueous solution employing enthalpies derived from isothermal titration calorimetry combined with Gibbs free energies derived from literature data for the binding equilibria. In both cases, the binding is exothermic and enthalpy driven, but entropically unfavorable, with only modest changes in the Gibbs free energy as a function of the extent of anion binding. Likewise, perchlorate ion binding was found to have little or no effect on the aggregation numbers of SB3-14 micelles determined by time-resolved fluorescence quenching of pyrene by the N-hexadecylpyridinium cation. The results are interpreted within the context of the factors involved in the ion-pairing between the anions and the positive charge center of the zwitterion headgroup and the interplay between electrostatics, solvent reorganization and a net loss of translational degrees of freedom that accompany anion binding.


Assuntos
Micelas , Ânions , Betaína/análogos & derivados , Calorimetria , Termodinâmica
19.
J Colloid Interface Sci ; 611: 129-136, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-34933191

RESUMO

Sulfavant A and Sulfavant R, sulfoquinovoside-glycerol lipids under study as vaccine adjuvants, structurally differ only for the configuration of glyceridic carbon, R/S and R respectively. The in vitro activity of these substances follows a bell-shaped dose-response curve, but Sulfavant A gave the best response around 20 µM, while Sulfavant R at 10 nM. Characterization of aqueous self-assembly of these molecules by a multi-technique approach clarified the divergent and controversial biological outcome. Supramolecular structures were present at concentrations much lower than critical aggregation concentration for both products. The kind and size of these aggregates varied as a function of the concentration differently for Sulfavant A and Sulfavant R. At nanomolar range, Sulfavant A formed cohesive vesicles, while Sulfavant R arranged in spherical micellar particles whose reduced stability was probably responsible for an increase of monomer concentration in accordance with immunomodulatory profile. Instead, at micromolar concentrations transition from micellar to vesicular state of Sulfavant R occurred and thermodynamic stability of the aggregates, assessed by surface tensiometry, correlated with the bioactivity of Sulfavant A at 20 µM and the complete loss of efficacy of Sulfavant R. The study of Sulfavants provides clear evidence of how self-aggregation, often neglected, and the equilibria between monomers and aqueous supramolecular forms of lipophilic molecules deeply determine the overall bio-response.


Assuntos
Água , Adjuvantes Imunológicos , Micelas , Termodinâmica
20.
Environ Res ; 204(Pt A): 111920, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-34464618

RESUMO

One of the main causes for Alzheimer disease is the abnormal self-assembly of the amyloid-beta (Aß) peptide, which in turn forms a toxic ß-rich aggregation. A recent study suggests that gold nanoparticles (AuNPs) can inhibit the Aß aggregation. Nevertheless, the effects of AuNPs on Aß peptide system are still ambiguous and needs exploration that is more detailed. Molecular dynamics simulations have been carried out to investigate the aggregation mechanism of Aß42 peptide for 500 ns. During simulation, C-terminus regions of Met 35-Ala42 residues exhibits ß-sheet conformations. Meanwhile, the Au144MC coordination induces substantial α-helical character, both α-helix and 310-helix structure at 0-500ns, in the region of Asp1-Arg5 and Val36-Ile41 residues. The Au144MC strongly coordinates with Asp1, Ala2, Glu3, Phe4, Asp7, Tyr10 and Gln15 residues that plays the significant effects to loss the ß-sheet geometry in the N-terminal region and it converted into random α-helix, turn and bend conformation. On comparing the RMSF of the Aß42 peptide and Aß42-Au144MC complex shows that the coordination of Au144MC results in greater rigidity of the Aß42 peptide backbone regions with exemptions for the Asp1, Ala2, Glu3, Leu34, Ile41 and Ala42 residues due to the strong binding between the metal cluster and the CHC (Leu17-Ala21) region. The structural stability of the Aß42 peptide and Aß42-Au144MC complex is enhanced by the several intermolecular and intramolecular interactions and it was visibly revealed in the H-bond. From the above results, it is very evident that the Au144MC can be used as inhibitor agent for the oligomerization of Aß42.


Assuntos
Doença de Alzheimer , Nanopartículas Metálicas , Peptídeos beta-Amiloides , Ouro , Humanos , Fragmentos de Peptídeos , Termodinâmica
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