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1.
Int J Mol Sci ; 22(6)2021 Mar 10.
Artículo en Inglés | MEDLINE | ID: mdl-33802169

RESUMEN

In order to treat Coronavirus Disease 2019 (COVID-19), we predicted and implemented a drug delivery system (DDS) that can provide stable drug delivery through a computational approach including a clustering algorithm and the Schrödinger software. Six carrier candidates were derived by the proposed method that could find molecules meeting the predefined conditions using the molecular structure and its functional group positional information. Then, just one compound named glycyrrhizin was selected as a candidate for drug delivery through the Schrödinger software. Using glycyrrhizin, nafamostat mesilate (NM), which is known for its efficacy, was converted into micelle nanoparticles (NPs) to improve drug stability and to effectively treat COVID-19. The spherical particle morphology was confirmed by transmission electron microscopy (TEM), and the particle size and stability of 300-400 nm were evaluated by measuring DLSand the zeta potential. The loading of NM was confirmed to be more than 90% efficient using the UV spectrum.


Asunto(s)
/tratamiento farmacológico , Biología Computacional/métodos , Sistemas de Liberación de Medicamentos/métodos , Células A549 , Antiinflamatorios/química , Antiinflamatorios/uso terapéutico , Benzamidinas/química , Benzamidinas/uso terapéutico , Supervivencia Celular/efectos de los fármacos , Análisis por Conglomerados , Simulación por Computador , Bases de Datos Farmacéuticas , Portadores de Fármacos/química , Reposicionamiento de Medicamentos , Estabilidad de Medicamentos , Ácido Glicirrínico/química , Ácido Glicirrínico/uso terapéutico , Guanidinas/química , Guanidinas/uso terapéutico , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Micelas , Microscopía Electrónica de Transmisión , Estructura Molecular , Nanopartículas/química , Tamaño de la Partícula
2.
Food Chem ; 352: 129333, 2021 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-33662916

RESUMEN

Intelligent packaging with a pH indicator has been a hot research topic due to its extra active role compared with traditional ones. Considering the possible toxicity of synthetic pH sensitive pigments, natural pigments are promising alternative indicators. This work aimed to develop and characterize active and pH sensitive films based on psyllium seed gum (PSG) incorporated with free and microencapsulated mulberry pomace extracts (MPE). Compared with PSG control film, PSG-MPE films showed an increase in total phenolic content and DPPH scavenging activity, and decrease in surface hydrophobicity, lightness, and tensile strength. The molecular interactions between PSG and MPE were confirmed by thermal and microstructure analysis. Moreover, PSG-MPE films displayed wide color differences from red to blue at pH 2.0 - 12.0. PSG-based films containing 10% free and microencapsulated MPE demonstrated better overall performance and economy in packaging applications, which could be used as promising active and pH-sensitive food packaging materials.


Asunto(s)
Embalaje de Alimentos/métodos , Morus/química , Extractos Vegetales/química , Gomas de Plantas/química , Psyllium/química , Semillas/química , Cápsulas , Color , Concentración de Iones de Hidrógeno , Interacciones Hidrofóbicas e Hidrofílicas , Resistencia a la Tracción
3.
Nat Commun ; 12(1): 1620, 2021 03 12.
Artículo en Inglés | MEDLINE | ID: mdl-33712624

RESUMEN

Amyotrophic lateral sclerosis and several other neurodegenerative diseases are associated with brain deposits of amyloid-like aggregates formed by the C-terminal fragments of TDP-43 that contain the low complexity domain of the protein. Here, we report the cryo-EM structure of amyloid formed from the entire TDP-43 low complexity domain in vitro at pH 4. This structure reveals single protofilament fibrils containing a large (139-residue), tightly packed core. While the C-terminal part of this core region is largely planar and characterized by a small proportion of hydrophobic amino acids, the N-terminal region contains numerous hydrophobic residues and has a non-planar backbone conformation, resulting in rugged surfaces of fibril ends. The structural features found in these fibrils differ from those previously found for fibrils generated from short protein fragments. The present atomic model for TDP-43 LCD fibrils provides insight into potential structural perturbations caused by phosphorylation and disease-related mutations.


Asunto(s)
Amiloide/química , Microscopía por Crioelectrón/métodos , Proteínas de Unión al ADN/química , Amiloide/genética , Amiloide/metabolismo , Esclerosis Amiotrófica Lateral/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Interacciones Hidrofóbicas e Hidrofílicas , Modelos Moleculares , Mutación Puntual , Conformación Proteica
4.
Food Chem ; 351: 129344, 2021 Jul 30.
Artículo en Inglés | MEDLINE | ID: mdl-33647688

RESUMEN

Protein oxidation is considered as an important factor affecting the texture quality of surimi. In this work, the myofibrillar protein (MP) from shrimp (Penaeus vannamei) was subjected to a hydroxyl radical generating system at various concentrations of H2O2, to simulate the oxidative environment during surimi processing. After the hydroxyl radical oxidation, it was found that the carbonyl content, surface hydrophobicity, and MP aggregation increased. Meanwhile, the a-helix decreased, but ß-sheet increased after oxidation. The moderate oxidation led to a dense network microstructure, increased water holding capacity (WHC) and decreased water mobility, which ultimately enhanced textural (hardness and springiness increased by 0.51- and 0.06-fold, respectively) and rheological properties of MP gel (MPG). However, excessive oxidation could reduce the mechanical properties of MPG. The microstructure, WHC and water distribution played a key role in the mechanical properties of MPG. This study can provide a theoretical basis for processing of shrimp surimi products.


Asunto(s)
Anostraca , Fenómenos Químicos , Radical Hidroxilo/química , Proteínas Musculares/química , Animales , Geles , Interacciones Hidrofóbicas e Hidrofílicas , Oxidación-Reducción , Reología , Alimentos Marinos , Agua/química
5.
Food Chem ; 351: 129318, 2021 Jul 30.
Artículo en Inglés | MEDLINE | ID: mdl-33647690

RESUMEN

Linusorbs, known as cyclolinopeptides, are a group of cyclic hydrophobic peptides derived from flaxseed oil with various health benefits. However, the current research efforts on both the biological activities and antioxidant capacities of linusorbs are limited because of existing issues with their purification and characterization. A practical method based on preparative HPLC for isolating 12 linusorbs simultaneously was developed and factors such as the solvent selection, gradient elution program, flow rate, loaded mass, and loading concentration, were optimized. The optimum conditions were an initial acetonitrile (ACN) to water ratio of 40%, final ACN ratio of 80%, eluting time of 21 min, a flow rate of 16 mL/min, sample load of 12.5 mg, and concentration of 80 mg/mL (in methanol). The 12 linusorbs obtained were verified using off-line MS/MS, recording purities of above 95.5%. The method could serve as a practical and fast isolation method enabling further investigation of minor linusorbs.


Asunto(s)
Cromatografía Líquida de Alta Presión/métodos , Aceite de Linaza/química , Péptidos Cíclicos/aislamiento & purificación , Acetonitrilos/química , Interacciones Hidrofóbicas e Hidrofílicas , Metanol/química , Péptidos Cíclicos/química , Factores de Tiempo
6.
Zhongguo Zhong Yao Za Zhi ; 46(3): 638-644, 2021 Feb.
Artículo en Chino | MEDLINE | ID: mdl-33645031

RESUMEN

According to human carboxylesterase 2(hCE2) inhibitors reported in the literature, the pharmacophore model of hCE2 inhibitors was developed using HipHop module in Discovery Studio 2016. The optimized pharmacophore model, which was validated by test set, contained two hydrophobic, one hydrogen bond acceptor, and one aromatic ring features. Using the pharmacophore model established, 5 potential hCE2 inhibitors(CS-1,CS-2,CS-3,CS-6 and CS-8) were screened from 20 compounds isolated from the roots of Paeonia lactiflora, which were further confirmed in vitro, with the IC_(50) values of 5.04, 5.21, 5.95, 6.64 and 7.94 µmol·L~(-1), respectively. The results demonstrated that the pharmacophore model exerted excellent forecasting ability with high precision, which could be applied to screen novel hCE2 inhibitors from Chinese medicinal materials.


Asunto(s)
Carboxilesterasa , Carboxilesterasa/antagonistas & inhibidores , Carboxilesterasa/metabolismo , Humanos , Enlace de Hidrógeno , Interacciones Hidrofóbicas e Hidrofílicas
7.
Methods Mol Biol ; 2259: 247-257, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33687720

RESUMEN

Protein phosphorylation is a critical posttranslational modification (PTM), with cell signaling networks being tightly regulated by protein phosphorylation. Despite recent technological advances in reversed-phase liquid chromatography (RPLC)-mass spectrometry (MS)-based proteomics, comprehensive phosphoproteomic coverage in complex biological systems remains challenging, especially for hydrophilic phosphopeptides that often have multiple phosphorylation sites. Herein, we describe an MS-based phosphoproteomics protocol for effective quantitative analysis of hydrophilic phosphopeptides. This protocol was built upon a simple tandem mass tag (TMT)-labeling method for significantly increasing peptide hydrophobicity, thus effectively enhancing RPLC-MS analysis of hydrophilic peptides. Through phosphoproteomic analyses of MCF7 cells, this method was demonstrated to greatly increase the number of identified hydrophilic phosphopeptides and improve MS signal detection. With the TMT labeling method, we were able to identify a previously unreported phosphopeptide from the G protein-coupled receptor (GPCR) CXCR3, QPpSSSR, which is thought to be important in regulating receptor signaling. This protocol is easy to adopt and implement and thus should have broad utility for effective RPLC-MS analysis of the hydrophilic phosphoproteome as well as other highly hydrophilic analytes.


Asunto(s)
Fosfopéptidos/análisis , Proteómica/métodos , Cromatografía Liquida/métodos , Cromatografía de Fase Inversa/métodos , Células HEK293 , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Inmunoprecipitación/métodos , Células MCF-7 , Fosfopéptidos/aislamiento & purificación , Proteoma/análisis , Proteoma/aislamiento & purificación , Espectrometría de Masas en Tándem/métodos
8.
Methods Mol Biol ; 2266: 39-72, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33759120

RESUMEN

The interaction between a protein and its ligands is one of the basic and most important processes in biological chemistry. Docking methods aim to predict the molecular 3D structure of protein-ligand complexes starting from coordinates of the protein and the ligand separately. They are widely used in both industry and academia, especially in the context of drug development projects. AutoDock4 is one of the most popular docking tools and, as for any docking method, its performance is highly system dependent. Knowledge about specific protein-ligand interactions on a particular target can be used to successfully overcome this limitation. Here, we describe how to apply the AutoDock Bias protocol, a simple and elegant strategy that allows users to incorporate target-specific information through a modified scoring function that biases the ligand structure towards those poses (or conformations) that establish selected interactions. We discuss two examples using different bias sources. In the first, we show how to steer dockings towards interactions derived from crystal structures of the receptor with different ligands; in the second example, we define and apply hydrophobic biases derived from Molecular Dynamics simulations in mixed solvents. Finally, we discuss general concepts of biased docking, its performance in pose prediction, and virtual screening campaigns as well as other potential applications.


Asunto(s)
Simulación del Acoplamiento Molecular/métodos , Proteínas/química , Solventes/química , Sitios de Unión , Cristalografía por Rayos X , Quinasa 2 Dependiente de la Ciclina/química , Interacciones Hidrofóbicas e Hidrofílicas , Ligandos , Conformación Molecular , Simulación de Dinámica Molecular , Unión Proteica , Programas Informáticos , Electricidad Estática
9.
Molecules ; 26(4)2021 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-33670043

RESUMEN

The aim of this study was to investigate and understand bacterial adhesion to different dental material surfaces like amalgam, Chromasit, an Co-Cr alloy, an IPS InLine ceramic, yttrium stabilized tetragonal polycrystalline zirconia (TPZ), a resin-based composite, an Au-Pt alloy, and a tooth. For all materials, the surface roughness was assessed by profilometry, the surface hydrophobicity was determined by tensiometry, and the zeta potential was measured by electrokinetic phenomena. The arithmetic average roughness was the lowest for the TPZ ceramic (Ra = 0.23 µm ± 0.02 µm), while the highest value was observed for the Au-Pt alloy (Ra = 0.356 µm ± 0.075 µm). The hydrophobicity was the lowest on the TPZ ceramic and the highest on the Co-Cr alloy. All measured streaming potentials were negative. The most important cause of tooth caries is the bacterium Streptococcus mutans, which was chosen for this study. The bacterial adhesion to all material surfaces was determined by scanning electron microscopy. We showed that the lowest bacterial extent was on the amalgam, whereas the greatest extent was on tooth surfaces. In general, measurements showed that surface properties like roughness, hydrophobicity and charge have a significant influence on bacterial adhesion extent. Therefore, dental material development should focus on improving surface characteristics to reduce the risk of secondary caries.


Asunto(s)
Aleaciones/química , Cerámica/química , Resinas Compuestas/química , Amalgama Dental/química , Metacrilatos/química , Streptococcus mutans/crecimiento & desarrollo , Uretano/química , Adhesión Bacteriana , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Tamaño de la Partícula , Propiedades de Superficie
10.
Molecules ; 26(4)2021 Feb 20.
Artículo en Inglés | MEDLINE | ID: mdl-33672689

RESUMEN

To expand the applications of graphene-based materials to biogas purification, a series of reduced graphene oxide aerogels (rGOAs) were prepared from industrial grade graphene oxide using a simple hydrothermal method. The influences of the hydrothermal preparation temperature on the textural properties, hydrophobicity and physisorption behavior of the rGOAs were investigated using a range of physical and spectroscopic techniques. The results showed that the rGOAs had a macro-porous three-dimensional network structure. Raising the hydrothermal treatment temperature reduced the number of oxygen-containing groups, whereas the specific surface area (SBET), micropore volume (Vmicro) and water contact angle values of the rGOAs all increased. The dynamic adsorption properties of the rGOAs towards hexamethyldisiloxane (L2) increased with increasing hydrothermal treatment temperature and the breakthrough adsorption capacity showed a significant linear association with SBET, Vmicro and contact angle. There was a significant negative association between the breakthrough time and inlet concentration of L2, and the relationship could be reliably predicted with a simple empirical formula. L2 adsorption also increased with decreasing bed temperature. Saturated rGOAs were readily regenerated by a brief heat-treatment at 100 °C. This study has demonstrated the potential of novel rGOA for applications using adsorbents to remove siloxanes from biogas.


Asunto(s)
Grafito/química , Siloxanos/química , Adsorción , Geles/química , Interacciones Hidrofóbicas e Hidrofílicas , Oxidación-Reducción , Tamaño de la Partícula , Propiedades de Superficie
11.
Food Chem ; 352: 129395, 2021 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-33677211

RESUMEN

Myofibrillar proteins (MPs), as a food-grade material, have the potential to improve the solubility and bioavailability of curcumin. However, the interaction mechanism between MPs and curcumin under charge regulation induced by alkaline pH and NaCl was unclear. In this study, the binding between curcumin and MPs at pH 12 was confirmed by the fluorescence quenching under different NaCl concentration (0, 0.3, 0.6 and 0.9 mol/L). Further kinetic experiments showed, MPs possessed a higher affinity to bind curcumin in the presence of NaCl, especially at 0.6 M NaCl. Followed pH shifting from 12 to 7 does not affect UV-Vis absorption spectra of protein-curcumin dispersions. The secondary structure of MPs was not affected by binding with curcumin. Formation of this stable complex can be explained by hydrophobic other than electrostatic interaction. Therefore, the presence of NaCl facilitated exposure of hydrophobic pocket to improve the binding affinity between curcumin and MPs due to the importance of hydrophobic interaction.


Asunto(s)
Curcumina/metabolismo , Proteínas Musculares/metabolismo , Curcumina/química , Interacciones Hidrofóbicas e Hidrofílicas , Cinética , Proteínas Musculares/química , Unión Proteica , Cloruro de Sodio/química , Solubilidad , Electricidad Estática
12.
Carbohydr Polym ; 260: 117843, 2021 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-33712117

RESUMEN

In this study, trehalose (TRE) was added to prepare whey protein concentrate (WPC)/pullulan (PUL)/TRE hydrogel and the hydrogel was used as the wall material to improve the viability of encapsulated L. plantarum during freeze drying and storage. The optimum conditions were 5.0 % TRE concentration and 1:4 (v:v) of the ratio of L. plantarum suspension to the hydrogel. Under these conditions, the survival rates of L. plantarum were 94.36 ± 1.06 % after freeze drying and 97.02 ± 0.30 % after storage for 240 d at 4 °C. Interactions and rheological properties of WPC/PUL/TRE hydrogel were also studied. The results showed TRE reduced storage modulus (G') of the hydrogel and weakened hydrophobic interactions, disulfide and hydrogen bonds between proteins and polysaccharides, which was not conducive to hydrogel formation. In addition, the excellent water-holding capacity of WPC/PUL/TRE hydrogel was found by the drying kinetic experiment.


Asunto(s)
Glucanos/química , Hidrogeles/química , Lactobacillus plantarum/fisiología , Trehalosa/química , Proteína de Suero de Leche/química , Liofilización , Hidrogeles/farmacología , Enlace de Hidrógeno , Interacciones Hidrofóbicas e Hidrofílicas , Viabilidad Microbiana/efectos de los fármacos , Reología , Compuestos de Sulfhidrilo/química
13.
Carbohydr Polym ; 260: 117792, 2021 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-33712140

RESUMEN

Methylcellulose (MC) has received considerable attention because of its thermogelation behavior in aqueous solutions upon heating; however, the accompanied macro-phase separation results in demixing and detriment of thickening power. To alleviate this drawback, a novel family of hydrophilically modified methylcelluloses (HMMCs) was prepared by introducing acylamino, carboxyl, and amino groups onto MC side chains. Above association temperature (Tass), MC solutions experienced obvious macro-phase separation and thermothinning phenomenon; on the contrary, HMMCs solutions exhibited thermo- and salt-thickening behaviors, and Tass could be adjusted from 44 °C to 87 °C by altering the nature of HMMCs or salt content in solutions. The mechanism to eliminate the macro-phase separation of HMMC stems from the balance between hydrophilicity and hydrophobicity. This work opens a new avenue for cellulose derivatives to sustain their thermoviscosifying ability and widen their applications in hostile environments.


Asunto(s)
Metilcelulosa/química , Polímeros/química , Interacciones Hidrofóbicas e Hidrofílicas , Reología , Temperatura , Viscosidad
14.
Carbohydr Polym ; 260: 117798, 2021 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-33712146

RESUMEN

The present study was conducted to investigate the structural characteristics of an acid-extracted polysaccharide fraction from mountain tea. The monosaccharide composition revealed that uronic acids (72.4 mol%) considerably predominated in the fraction, followed by smaller amounts of galactose (14.5 mol%) and glucose (6.2 mol%). The fraction contained mostly a highly methyl-esterified homogalacturonan (HG) - 71 mol%. The pectin had a high molecular weight population (∼60-100 kDa). Enzymatic fingerprinting was employed with a combination of HG degrading enzymes and LC-HILIC-MS, HPAEC, HPSEC to examine the structure in greater detail. Unsaturated oligomers released indicated the presence of large blocks of highly methyl-esterified GalA residues. Furthermore, the presence of blocks of non-esterified GalA residues and partly methyl-esterified and acetylated GalA residues in HG domain was demonstrated. The research findings provide a basis for further investigations regarding biological activity and commercial exploitation of mountain tea.


Asunto(s)
Polisacáridos/análisis , Sideritis/metabolismo , Cromatografía Líquida de Alta Presión , Interacciones Hidrofóbicas e Hidrofílicas , Espectrometría de Masas , Peso Molecular , Pectinas/química , Poligalacturonasa/metabolismo , Polisacaridoliasas/metabolismo , Polisacáridos/aislamiento & purificación , Polisacáridos/metabolismo
15.
Nat Commun ; 12(1): 1895, 2021 03 25.
Artículo en Inglés | MEDLINE | ID: mdl-33767131

RESUMEN

Soluble proteins are universally packed with a hydrophobic core and a polar surface that drive the protein folding process. Yet charged networks within the central protein core are often indispensable for the biological function. Here, we show that natural buried ion-pairs are stabilised by amphiphilic residues that electrostatically shield the charged motif from its surroundings to gain structural stability. To explore this effect, we build artificial proteins with buried ion-pairs by combining directed computational design and biophysical experiments. Our findings illustrate how perturbation in charged networks can introduce structural rearrangements to compensate for desolvation effects. We validate the physical principles by resolving high-resolution atomic structures of the artificial proteins that are resistant towards unfolding at extreme temperatures and harsh chemical conditions. Our findings provide a molecular understanding of functional charged networks and how point mutations may alter the protein's conformational landscape.


Asunto(s)
Conformación Proteica , Pliegue de Proteína , Proteínas/metabolismo , Secuencia de Aminoácidos , Biología Computacional , Simulación por Computador , Interacciones Hidrofóbicas e Hidrofílicas , Simulación de Dinámica Molecular , Termodinámica
16.
Int J Nanomedicine ; 16: 1377-1390, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33658778

RESUMEN

Background: Vascular drug delivery becomes a promising direction in the development of novel therapeutic strategies in the treatment of cardiovascular pathologies, such as hypertension. However, targeted delivery of hydrophobic substances, with poor bioavailability, remains a challenge. Here, we described the hypotensive effects of a low dose of curcumin delivered to the vascular wall using hyaluronic acid-based nanocapsules. Methods: The group of hypertensive TGR(m-Ren2)27 rats, was administrated respectively with the vehicle, curcumin solution or curcumin delivered using hyaluronic acid-based nanocapsules (HyC12-Cur), for 7 days each, maintaining the wash-out period between treatments. Arterial blood pressure (systolic - SBP, diastolic - DBP) and heart rate (HR) were monitored continuously using a telemetry system (Data Science International), and Mean Arterial Pressure (MAP) was calculated from SBP and DBP. Results: In hypertensive rats, a low dose of curcumin (4.5 mg/kg) administrated in HyC12-Cur for 7 days resulted in a gradual inhibition of SBP, DBP and MAP increase without an effect on HR. At the end of HyC12-Cur - based treatment changes in SBP, DBP and MAP amounted to -2.0±0.8 mmHg, -3.9±0.7 mmHg and -3.3±0.7 mmHg, respectively. In contrast, the administration of a curcumin solution (4.5 mg/kg) did not result in a significant hypotensive effect and the animals constantly developed hypertension. Vascular delivery of capsules with curcumin was confirmed using newly developed fluorine-rich nanocapsules (HyFC10-PFOB) with a shell based on a HA derivative and similar size as HyC12-Cur. HyFC10-PFOB gave fluorine signals in rat aortas analyzed ex vivo with a 19F NMR technique after a single intragastric administration. Conclusion: These results suggest that nanocapsules based on hyaluronic acid, the ubiquitous glycosaminoglycan of the extracellular matrix and an integral part of endothelial glycocalyx, may represent a suitable approach to deliver hydrophobic, poorly bioavailable compounds, to the vascular wall.


Asunto(s)
Curcumina/administración & dosificación , Curcumina/uso terapéutico , Ácido Hialurónico/química , Hipertensión/tratamiento farmacológico , Nanocápsulas/química , Administración Oral , Animales , Aorta/efectos de los fármacos , Aorta/patología , Presión Sanguínea/efectos de los fármacos , Curcumina/farmacología , Diástole/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Flúor/química , Frecuencia Cardíaca/efectos de los fármacos , Hidrodinámica , Interacciones Hidrofóbicas e Hidrofílicas , Hipertensión/fisiopatología , Espectroscopía de Resonancia Magnética , Masculino , Tamaño de la Partícula , Ratas , Electricidad Estática , Sístole/efectos de los fármacos
17.
Nat Commun ; 12(1): 1530, 2021 03 09.
Artículo en Inglés | MEDLINE | ID: mdl-33750792

RESUMEN

De novo protein design is advancing rapidly. However, most designs are for single states. Here we report a de novo designed peptide that forms multiple α-helical-bundle states that are accessible and interconvertible under the same conditions. Usually in such designs amphipathic α helices associate to form compact structures with consolidated hydrophobic cores. However, recent rational and computational designs have delivered open α-helical barrels with functionalisable cavities. By placing glycine judiciously in the helical interfaces of an α-helical barrel, we obtain both open and compact states in a single protein crystal. Molecular dynamics simulations indicate a free-energy landscape with multiple and interconverting states. Together, these findings suggest a frustrated system in which steric interactions that maintain the open barrel and the hydrophobic effect that drives complete collapse are traded-off. Indeed, addition of a hydrophobic co-solvent that can bind within the barrel affects the switch between the states both in silico and experimentally.


Asunto(s)
Péptidos/química , Cristalografía por Rayos X , Interacciones Hidrofóbicas e Hidrofílicas , Simulación de Dinámica Molecular , Conformación Proteica , Conformación Proteica en Hélice alfa , Ingeniería de Proteínas , Proteínas/química , Solventes
18.
Food Chem ; 352: 129398, 2021 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-33652197

RESUMEN

We investigated the effects of ultrasonic treatment (400 W, 20 kHz, 45.52 W/L) and storage time (0 d, 3 d, 7 d and 10 d) on functional properties, structural changes and in vitro digestion of actomyosin complex isolated from vacuum-packed pork. As storage time increased, turbidity, surface hydrophobicity, active sulfhydryl and total sulfhydryl of actomyosin complex increased, while protein solubility decreased. Ultrasonic treatment increased surface hydrophobicity, protein solubility and active sulfhydryl content but decreased turbidity and total sulfhydryl content compared with the control. Ultrasonic treatment caused a reduction in α-helix content on 0 day and the fluorescence intensity of tryptophan and tyrosine residues. It increased pancreatin digestibility of actomyosin complex and the number of peptides of smaller than 1 kDa. However, it decreased the number of peptides. The findings provide a new insight into the application of appropriate ultrasonic treatment to promote meat digestibility.


Asunto(s)
Actomiosina/química , Digestión , Almacenamiento de Alimentos , Carne/análisis , Ondas Ultrasónicas , Actomiosina/metabolismo , Animales , Interacciones Hidrofóbicas e Hidrofílicas , Solubilidad , Compuestos de Sulfhidrilo/química , Porcinos
19.
Food Chem ; 352: 129306, 2021 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-33677213

RESUMEN

Numerous human conditions can benefit from diets rich in proteins and bioactives, such as capsaicin (CAP), yet their effective delivery is a sensorial, scientific and technological challenge. This study hypothesized that CAP can form various complexes with native bovine alpha-lactalbumin (holo-ALA) and decalcified-ALA (apo-ALA). Calorimetric and spectroscopic techniques reveals ALA-CAP molecular complexation is spontaneous, exothermic and accompanied by various conformational changes. ITC shows the interaction stoichiometry (n) and binding constant (Kb) for holo-ALA to be 0.87 ± 0.03, 1.54 ± 0.23 × 105 M-1 and for apo-ALA to be 0.64 ± 0.09, 9.41 ± 2.16 × 104 M-1. Molecular docking further elucidates that hydrogen bonds govern CAP binding to holo-ALA while hydrophobic interactions dominate binding to apo-ALA in a structural cleft. Finally, this work shows these interactions along with controlled aggregation can be utilized to form CAP-loaded colloids with encapsulation efficiency of 47.1 ± 1.0%. Thus, this study shows great promise in the prospective use of ALA as an edible delivery vehicle for CAP.


Asunto(s)
Capsaicina/química , Capsaicina/metabolismo , Fenómenos Químicos , Lactalbúmina/química , Lactalbúmina/metabolismo , Animales , Bovinos , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Simulación del Acoplamiento Molecular , Unión Proteica
20.
Food Chem ; 352: 129267, 2021 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-33691207

RESUMEN

In this study, a soluble complex formed between 0.5% (w/v) heated whey protein isolate (HWPI) and 5% (w/v) octenyl succinic anhydride (OSA)-modified starch at pH 4.5 was used to encapsulate ß-carotene for improving its solubility and stability. The apparent aqueous solubility of ß-carotene was increased markedly (264.05 ± 72.53 µg/mL) after encapsulation in the soluble complex. Transmission electron microscopy and scanning electron microscopy were used to evaluate the effect of the encapsulation of ß-carotene on the structure of the soluble complex. Fourier transform infrared spectroscopy showed that the characteristic peaks of ß-carotene disappeared in the soluble complex, suggesting that ß-carotene may have been encapsulated into the soluble complex via hydrophobic interactions. X-ray diffraction indicated that the ß-carotene was in an amorphous form within the soluble complex. An accelerated stability test showed that the soluble complex could effectively improve the chemical stability of ß-carotene during long-term storage under low pH conditions.


Asunto(s)
Almidón/análogos & derivados , Proteína de Suero de Leche/química , beta Caroteno/química , Cápsulas , Interacciones Hidrofóbicas e Hidrofílicas , Solubilidad , Almidón/química
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