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1.
PLoS One ; 15(2): e0226123, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32032370

RESUMO

The visual photopigment protein rhodopsin (Rh) is a typical G protein-coupled receptor (GPCR) that initiates the phototransduction cascade in retinal disk membrane of rod-photoreceptor cells. Rh molecule has a tendency to form dimer, and the dimer tends to form rows, which is suggested to heighten phototransduction efficiency in single-photon regime. In addition, the dimerization confers Rh an affinity for lipid raft, i.e. raftophilicity. However, the mechanism by which Rh-dimer raftophilicity contributes to the organization of the higher order structure remains unknown. In this study, we performed coarse-grained molecular dynamics simulations of a disk membrane model containing unsaturated lipids, saturated lipids with cholesterol, and Rh-dimers. We described the Rh-dimers by two-dimensional particle populations where the palmitoyl moieties of each Rh exhibits raftophilicity. We simulated the structuring of Rh in a disk for two types of Rh-dimer, i.e., the most and second most stable Rh dimers, which exposes the raftophilic regions at the dimerization-interface (H1/H8 dimer) and two edges away from the interface (H4/H5 dimer), respectively. Our simulations revealed that only the H1/H8 dimer could form a row structure. A small number of raftophilic lipids recruited to and intercalated in a narrow space between H1/H8 dimers stabilize the side-by-side interaction between dimers in a row. Our results implicate that the nano-sized lipid raft domains act as a "glue" to organize the long row structures of Rh-dimers.


Assuntos
Simulação de Dinâmica Molecular , Multimerização Proteica , Rodopsina/química , Rodopsina/metabolismo , Colesterol/metabolismo , Cristalografia por Raios X , Ácidos Graxos Insaturados/metabolismo , Cinética , Bicamadas Lipídicas/metabolismo , Lipoilação , Microdomínios da Membrana/metabolismo , Membranas/química , Membranas/metabolismo , Modelos Moleculares , Conformação Proteica em alfa-Hélice , Células Fotorreceptoras Retinianas Bastonetes/metabolismo
2.
Orig Life Evol Biosph ; 49(4): 241-254, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31883067

RESUMO

Amino acids and peptides have been demonstrated to form lipoamino acids and lipopeptides under presumed prebiotic conditions, and readily form liposomes. Of the common nucleobases, adenine forms a liponucleobase even below 100 °C. Adenine as well as other nucleobases can also be derivatized with ethylene carbonate (and likely other similar compounds) onto which fatty acids can be attached. The fatty acid tails along with appropriately functionalized nucleobases provide some solubility of liponucleobases in membranes. Such membranes would provide a structure in which three of biology's major components are closely associated and available for chemical interactions. Nucleobase-to-nucleobase interactions would ensure that the liponucleobases would have a uniquely different head-group relationship than other amphiphiles within a membrane, likely forming rafts due their π-π interactions and providing surface discontinuities that could serve as catalytic sites. The π-π bond distance in aromatic compounds is typically 0.34 nm, commensurate with that of the amine to carboxylate distance in alpha amino acids. This would have provided opportunity for hydrogen bonding between amino acids and the distal primary amines or tautomeric carbonyl/hydroxyl groups of two π-bonded nucleobases. Such bonding would weaken the covalent linkages within the amino acids, making them susceptible to forming peptide bonds with an adjacent amino acid, likely a lipoamino acid or lipopeptide. Were this second lipoamino acid bound to a third π-bonded nucleobase, it could result in orientation, destabilization and peptide formation. The stacked triplet of nucleobases might constitute the primordial codon triplet from which peptides were synthesized: primordial translation.


Assuntos
Evolução Química , Lipopeptídeos/química , Membranas/química , Origem da Vida
3.
Mater Sci Eng C Mater Biol Appl ; 104: 109944, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31500058

RESUMO

Anti-relapse therapy after surgery plays a critical role in cancer therapy. New strategies maximizing the delivery of drugs to tumor cells while reducing toxic side effects on normal tissues and organs are still urgently required. In order to solve the problems of the poor delivery and inadequate distribution of cytotoxic chemotherapeutic drugs in the clinical application, an ultrasound-controllable and implantable release-system that utilized waterborne polyurethane (WPU) and chitosan (CS) composite membrane as drug carrier with wide flexible loading capacity for doxorubicin (DOX) was described in present work. Benefiting from the hydrophilic segment in WPU and bioactivity of amino groups on side chains of CS, the resulting composite films exhibited fine biodegradability, favorable cytocompatibility and excellent blood compatibility. The in vitro release studies illustrated that the drug-loading membranes displayed a well sustained release effect manifested in slow release, stability and no sudden release, and the DOX was able to release in an ultrasound-controlled manner. Cellular uptake assay and CCK 8 assay showed that the DOX can be released efficiently from the drug-loading matrix and taken up by tumor cells. As a means of adjuvant local treatment, this work provided a facile approach to the design of ultrasound-regulated membrane matrix that is highly beneficial not only due to the higher and long-term therapeutic efficiency, and improvement of utilization efficiency of chemotherapeutic drugs but also the low toxicity to normal cells.


Assuntos
Antineoplásicos/química , Quitosana/química , Poliuretanos/química , Animais , Antineoplásicos/farmacologia , Linhagem Celular , Linhagem Celular Tumoral , Doxorrubicina/química , Doxorrubicina/farmacologia , Portadores de Fármacos/química , Sistemas de Liberação de Medicamentos/métodos , Liberação Controlada de Fármacos , Membranas/química , Camundongos , Nanopartículas/química , Ondas Ultrassônicas
4.
Eur J Pharm Biopharm ; 142: 61-69, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31195130

RESUMO

The release mechanism for proteins and peptides from vesicular phospholipid gels (VPGs) is very complex. Drug release proceeds via a combination of erosion of the gel and diffusion of the drug out of it. This diffusion can be retarded by a slow permeation of the drug across the lipid bilayers in the gel as well as by its direct binding or adsorption to the lipid bilayers. Finally, the viscosity and homogeneity of the formulation may affect the release behavior. So far a direct correlation between one of these parameters and the release kinetics is not possible. In the present study, we aimed to investigate the contribution of drug-membrane interactions to the release kinetics of exenatide from differently composed VPGs (POPC, POPG and mixtures of both). To this end, in vitro release of exenatide as well as in vitro release of the phospholipids was monitored. Binding affinities were determined by microscale thermophoresis (MST). The sustained release behavior of exenatide could not simply be correlated to high viscosity of the VPG formulation. Release of exenatide from VPGs of anionic membranes containing POPG proceeded with a half-life of the order of 5 days and it seems to be controlled by the erosion of the gel. Its rate is unaffected by the initial pH inside the gel, independently of the strong impact of pH on exenatide binding to the membrane. At pH 4.5, exenatide is cationic and binds to membranes containing anionic POPG with a high affinity (Kd ≈ 10-30 µM). No high affinity membrane binding of exenatide is detected in this at pH 7.4, where exenatide is anionic, and to zwitterionic membranes composed of POPC. Exenatide release from the latter has a significantly longer half-life of 30 to 55 days. That means, these VPGs are much more resistant to erosion and show a very slow diffusional release. In this case, diffusion should be slowed down by the barrier function of the membranes rather than membrane affinity. In conclusion, erosion of the VPG matrix and membrane permeability of the drug are the major parameters influencing the release of exenatide from VPGs of POPC-POPG, whereas drug binding to the membranes had a minor effect only.


Assuntos
Exenatida/química , Lipídeos/química , Fosfolipídeos/química , Proteínas/química , Preparações de Ação Retardada/química , Liberação Controlada de Fármacos/efeitos dos fármacos , Géis/química , Cinética , Bicamadas Lipídicas/química , Membranas/química , Peptídeos/química , Fosfatidilcolinas/química , Fosfatidilgliceróis/química
5.
Carbohydr Polym ; 220: 71-78, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31196552

RESUMO

In this work, we report a convenient method of grafting non-leachable bioactive amine functions onto the surface of bacterial cellulose (BC) nanofibrils, via a simple silylation treatment in water. Two different silylation protocols, involving different solvents and post-treatments were envisaged and compared, using 3-aminopropyl-trimethoxysilane (APS) and (2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPS) as silylating agents. In aqueous and controlled conditions, water-leaching resistant amino functions could be successfully introduced into BC, via a simple freeze-drying process. The silylated material remained highly porous, hygroscopic and displayed sufficient thermal stability to support the sterilization treatments generally required in medical applications. The impact of the silylation treatment on the intrinsic anti-bacterial properties of BC was investigated against the growth of Escherichia coli and Staphylococcus aureus. The results obtained after the in vitro studies revealed a significant growth reduction of S. aureus within the material.


Assuntos
Materiais Biomédicos e Odontológicos , Celulose/farmacologia , Gluconacetobacter/metabolismo , Membranas/química , Nanofibras , Silanos/química , Antibacterianos/farmacologia , Materiais Biomédicos e Odontológicos/química , Materiais Biomédicos e Odontológicos/farmacologia , Escherichia coli/efeitos dos fármacos , Nanofibras/química , Nanofibras/uso terapêutico , Staphylococcus aureus/efeitos dos fármacos
6.
Carbohydr Polym ; 219: 113-120, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31151507

RESUMO

Honey is an ancient natural wound-healing agent and has been reintroduced to modern clinical wound care as it has various bioactivities. In this study, honey was incorporated into an alginate/PVA-based electrospun nanofibrous membrane to develop an efficient wound dressing material. The morphology and chemical composition of the nanofibrous membrane were observed by scanning electron microscopy and characterized via Fourier transform infrared spectroscopy, respectively, demonstrating that honey was successfully introduced to the nanofibers. The nanofibrous membranes with increasing honey content showed enhanced antioxidant activity, suggesting the ability to control the overproduction of reactive oxygen species. Disc diffusion assay and dynamic contact assay proved the antibacterial activity of the honey loaded nanofibers towards Gram-positive bacterium (Staphylococcus aureus) and Gram-negative bacterium (Escherichia coli). The cytotoxicity assay illustrated the non-cytotoxicity and biocompatibility of the nanofibrous membranes. Therefore, the developed honey/alginate/PVA nanofibrous membranes are promising for wound dressings.


Assuntos
Alginatos , Antibacterianos , Antioxidantes , Mel , Membranas/química , Nanofibras , Alginatos/química , Alginatos/uso terapêutico , Animais , Antibacterianos/química , Antibacterianos/farmacologia , Antioxidantes/química , Antioxidantes/farmacologia , Apiterapia , Escherichia coli/efeitos dos fármacos , Humanos , Camundongos , Células NIH 3T3 , Nanofibras/química , Nanofibras/uso terapêutico , Nanofibras/toxicidade , Curativos Oclusivos , Espécies Reativas de Oxigênio/metabolismo , Staphylococcus aureus/efeitos dos fármacos , Cicatrização
7.
J Nutr Sci ; 8: e16, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31080589

RESUMO

CVD and associated metabolic diseases are linked to chronic inflammation, which can be modified by diet. The objective of the present study was to determine whether there is a difference in inflammatory markers, blood metabolic and lipid panels and lymphocyte gene expression in response to a high-fat dairy food challenge with or without milk fat globule membrane (MFGM). Participants consumed a dairy product-based meal containing whipping cream (WC) high in saturated fat with or without the addition of MFGM, following a 12 h fasting blood draw. Inflammatory markers including IL-6 and C-reactive protein, lipid and metabolic panels and lymphocyte gene expression fold changes were measured using multiplex assays, clinical laboratory services and TaqMan real-time RT-PCR, respectively. Fold changes in gene expression were determined using the Pfaffl method. Response variables were converted into incremental AUC, tested for differences, and corrected for multiple comparisons. The postprandial insulin response was significantly lower following the meal containing MFGM (P < 0·01). The gene encoding soluble epoxide hydrolase (EPHX2) was shown to be more up-regulated in the absence of MFGM (P = 0·009). Secondary analyses showed that participants with higher baseline cholesterol:HDL-cholesterol ratio (Chol:HDL) had a greater reduction in gene expression of cluster of differentiation 14 (CD14) and lymphotoxin ß receptor (LTBR) with the WC+MFGM meal. The protein and lipid composition of MFGM is thought to be anti-inflammatory. These exploratory analyses suggest that addition of MFGM to a high-saturated fat meal modifies postprandial insulin response and offers a protective role for those individuals with higher baseline Chol:HDL.


Assuntos
Suplementos Nutricionais , Expressão Gênica/efeitos dos fármacos , Glicolipídeos/metabolismo , Glicoproteínas/metabolismo , Secreção de Insulina/efeitos dos fármacos , Refeições , Obesidade/metabolismo , Sobrepeso/metabolismo , Período Pós-Prandial/efeitos dos fármacos , Adolescente , Adulto , Idoso , Biomarcadores/sangue , Proteína C-Reativa/metabolismo , Colesterol/sangue , Citocinas/metabolismo , Laticínios , Dieta , Epóxido Hidrolases/genética , Epóxido Hidrolases/metabolismo , Jejum , Ácidos Graxos , Feminino , Glicolipídeos/farmacologia , Glicoproteínas/farmacologia , Humanos , Insulina/sangue , Interleucina-6/metabolismo , Masculino , Membranas/química , Síndrome Metabólica , Pessoa de Meia-Idade , Adulto Jovem
8.
ACS Appl Mater Interfaces ; 11(24): 21314-21322, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31120236

RESUMO

Dispersions of cubic liquid crystalline phases, also known as cubosomes, have shown great promise as delivery vehicles for a wide range of medicines. Due to their ordered structure, comprising alternating hydrophilic and hydrophobic domains, cubosomes possess unique delivery properties and compatibility with both water-soluble and -insoluble drugs. However, the drug delivery mechanism and cubosome interaction with human cells and bacteria are still poorly understood. Herein, we reveal how cubosomes loaded with the human cathelicidin antimicrobial peptide LL-37, a system with high bacteria-killing effect, interact with the bacterial membrane and provide new insights into the eradication mechanism. Combining the advanced experimental techniques neutron reflectivity and quartz crystal microbalance with dissipation monitoring, a mechanistic drug delivery model for LL-37-loaded cubosomes on bacterial mimicking bilayers was constructed. Moreover, the cubosome interaction with Escherichia coli was directly visualized using super-resolution laser scanning microscopy and cryogenic electron tomography. We could conclude that cubosomes loaded with LL-37 adsorbed and distorted bacterial membranes, providing evidence that the peptide-loaded cubosomes function as an antimicrobial unit.


Assuntos
Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Escherichia coli/efeitos dos fármacos , Membranas/química , Peptídeos Catiônicos Antimicrobianos/química , Peptídeos Catiônicos Antimicrobianos/farmacologia , Tomografia com Microscopia Eletrônica , Humanos , Bicamadas Lipídicas/química , Lipossomos/química , Microscopia Confocal , Microscopia Eletrônica de Transmissão , Técnicas de Microbalança de Cristal de Quartzo
9.
Phys Chem Chem Phys ; 21(20): 10370-10376, 2019 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-31065643

RESUMO

The collective behaviour of individual lipid molecules determines the properties of phospholipid membranes. However, the collective molecular motions often remain challenging to characterise at the desired spatial and temporal resolution. Here we study collective vibrational motion on picosecond time scales in dioleoylphosphatidylcholine lipid bilayers with varying cholesterol content using all-atom molecular dynamics simulations. Cholesterol is found to not only laterally compact the lipid bilayer, but also to change the velocity of longitudinal density fluctuations propagating in the plane of the membrane. Cholesterol-induced reduction of the area per lipid alters the collective dynamics of the lipid headgroups, but not of the lipid tails. The introduction of cholesterol reduces the number of water molecules interacting with the lipid headgroups, leading to a decrease in the velocity of the laterally-propagating sound mode. Thus, the stiffening effect of cholesterol is found to be indirect: decreasing the area per lipid weakens the interactions between the lipid headgroups and water. The collective modes characterised in this work can enable the membrane to dissipate excess energy and thus maintain its structural integrity, e.g., under mechanical stress.


Assuntos
Colesterol/química , Membranas/química , Água/química , Simulação de Dinâmica Molecular , Vibração
10.
Macromol Rapid Commun ; 40(14): e1900148, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31070820

RESUMO

Multistep catalytic transformations using incompatible catalysts (Wolf-Lamb-type) in a one-pot reaction cascade require site isolation of different catalysts by compartmentalization. In this work, the use of different electrospun catalytic membranes in a modular way as individual compartments is shown for one-pot Wolf-Lamb-type reaction cascades. The data are presented for one-pot cascade reaction sequences catalyzed by acidic and basic membranes made by electrospinning polymeric acid (poly(styrene-co-styrene sulfonic acid-co-4-methacryloyl-oxybenzophen)) and basic (poly(styrene-co-4-vinylpyridine-co-4-methacryloyl-oxybenzophen)) catalysts, respectively. The two-step, one-pot system used is the acidic catalyzed deacetylation of dimethoxybenzylacetale to benzaldehyde, which reacts with ethyl cyanoformate to result in a high yield of product (over 90%) under base-catalyzed conditions. The reaction kinetics are further monitored and evaluated by using differential equations, showing the necessity of a parameter Δt to represent a retarded start for the second reaction step. The concept provides an easy and upscalable approach for use in Wolf-Lamb-type systems.


Assuntos
Catálise , Polímeros/química , Poliestirenos/química , Membranas/química , Metacrilatos/química , Polímeros/síntese química , Poliestirenos/síntese química , Piridinas/síntese química , Piridinas/química , Ácidos Sulfônicos/química
11.
Phys Chem Chem Phys ; 21(29): 15958-15965, 2019 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-31032502

RESUMO

Correlated vibrational motion on the sub-picosecond timescale and associated collective dynamics in a protein-membrane environment are characterized using molecular dynamics simulations. We specifically analyze correlated motion of a membrane-associated protein and a lipid bilayer for distinct separation distances. Correlated vibrations persist up to distances of 25 Å between both biomolecular surfaces. These correlations are mediated by separating layers of water molecules, whose collective properties are altered by the simultaneous presence of protein and lipid bilayer interfaces.


Assuntos
Bicamadas Lipídicas/química , Proteínas de Membrana/química , Membranas/química , Simulação de Dinâmica Molecular , Água/química , Vibração
12.
PLoS One ; 14(4): e0212269, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30947264

RESUMO

Lipid monolayers are used as experimental model systems to study the physical chemical properties of biomembranes. With this purpose, surface pressure/area per molecule isotherms provide a way to obtain information on packing and compressibility properties of the lipids. These isotherms have been interpreted considering the monolayer as a two dimensional ideal or van der Waals gas without contact with the water phase. These modelistic approaches do not fit the experimental results. Based on Thermodynamics of Irreversible Processes (TIP), the expansion/compression process is interpreted in terms of coupled phenomena between area changes and water fluxes between a bidimensional solution of hydrated head groups in the monolayer and the bulk solution. The formalism obtained can reproduce satisfactorily the surface pressure/area per lipid isotherms of monolayer in different states and also can explain the area expansion and compression produced in particles enclosed by bilayers during osmotic fluxes. This novel approach gives relevance to the lipid-water interaction in restricted media near the membrane and provides a formalism to understand the thermodynamic and kinetic response of biointerphases to biological effectors.


Assuntos
Bicamadas Lipídicas/química , Lipídeos/química , Membranas/química , Termodinâmica , Cinética , Lipossomos/química , Modelos Teóricos , Osmose/fisiologia , Propriedades de Superfície , Água
13.
Biosens Bioelectron ; 133: 205-214, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30939397

RESUMO

Surface plasmon resonance (SPR) based dopamine sensor is realized using the state-of-art technique of molecular imprinting over an optical fiber substrate. Polypyrrole (PPy) is depicted as an effective polymer for the imprinting of dopamine through a green synthesis approach. Sensitivity of the probe is enhanced by the augmenting effect of surface imprinting of dopamine in polypyrrole over multiwalled carbon nanotubes (MWCNTs). To ensure the permselectivity of the probe towards dopamine molecules, a cation exchange polymer, nafion, is utilized as a membrane over imprinted sites to reduce the interference from anionic analytes like ascorbic acid and uric acid at physiological pH. The probe is characterized for a wide range of dopamine concentration from 0 to 10-5 M in artificial cerebrospinal fluid. Various probe parameters are varied to maximize the sensitivity of the sensor. The sensor possesses 18.9 pM as the limit of detection (LOD) which is lowest of those reported in the literature. The manifestation of sensing probe over an optical fiber along with the improved LOD makes the approach highly advantageous in terms of stability, repeatability, online remote monitoring, fast response, and miniaturization for its in vivo/in vitro applications in clinical sensing of dopamine.


Assuntos
Técnicas Biossensoriais , Dopamina/isolamento & purificação , Impressão Molecular , Nanotubos de Carbono/química , Dopamina/líquido cefalorraquidiano , Tecnologia de Fibra Óptica , Polímeros de Fluorcarboneto/química , Humanos , Membranas/química , Fibras Ópticas , Polímeros/química , Ressonância de Plasmônio de Superfície
14.
Mater Sci Eng C Mater Biol Appl ; 98: 1053-1063, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30812989

RESUMO

Silver nanoparticles (AgNPs) are widely explored to enhance the antibacterial property of medical devices such as wound dressings. However, no consensus has been reached on the efficacy and safety of AgNP incorporation. This study aimed (1) to elucidate the effect of proteins and inorganic ions on the antibacterial properties, (2) to confirm the antibacterial efficacy in vivo, and (3) to evaluate the wound healing ability of AgNPs incorporation into chitosan-based membranes. Three membranes with different amount of AgNPs were prepared. The antibacterial properties and silver release profile were evaluated after interacting with phosphate buffered saline or with serum in vitro. The antibacterial efficacy and the wound healing ability were explored in vivo. The results indicated that the biological environment had strong influences on the silver release: the inorganic ions resulted in a slow release whereas the proteins formed a barrier to block the silver release. Consequently, high amount of AgNPs incorporation was necessary to achieve in vivo antibacterial effects. Moreover, the addition of AgNPs did not alter the wound healing rate and tissue response. We can conclude that the AgNP incorporation can enhance antibacterial efficacy of biomaterials without altering the wound healing ability of the chitosan-based membranes.


Assuntos
Antibacterianos/farmacologia , Quitosana/química , Membranas/química , Nanopartículas Metálicas/administração & dosagem , Nanofibras/química , Prata/farmacologia , Cicatrização/efeitos dos fármacos , Antibacterianos/química , Nanopartículas Metálicas/química , Prata/química
15.
Biochemistry ; 58(10): 1423-1431, 2019 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-30735034

RESUMO

Lipidated small GTP-binding proteins of the Arf family interact with multiple cellular partners and with membranes to regulate intracellular traffic and organelle structure. Here, we focus on the ADP-ribosylation factor 1 (Arf1), which interacts with numerous proteins in the Arf pathway, such as the ArfGAP ASAP1 that is highly expressed and activated in several cancer cell lines and associated with enhanced migration, invasiveness, and poor prognosis. Understanding the molecular and mechanistic details of Arf1 regulation at the membrane via structural and biophysical studies requires large quantities of fully functional protein bound to lipid bilayers. Here, we report on the production of a functional human Arf1 membrane platform on nanodiscs for biophysical studies. Large scale bacterial production of highly pure, N-myristoylated human Arf1 has been achieved, including complex isotopic labeling for nuclear magnetic resonance (NMR) studies, and the myr-Arf1 can be readily assembled in small nanoscale lipid bilayers (nanodiscs, NDs). It is determined that myr-Arf1 requires a minimum binding surface in the NDs of ∼20 lipids. Fluorescence and NMR were used to establish nucleotide exchange and ArfGAP-stimulated GTP hydrolysis at the membrane, indicating that phophoinositide stimulation of the activity of the ArfGAP ASAP1 is ≥2000-fold. Differences in nonhydrolyzable GTP analogues are observed, and GMPPCP is found to be the most stable. Combined, these observations establish a functional environment for biophysical studies of Arf1 effectors and interactions at the membrane.


Assuntos
Fator 1 de Ribosilação do ADP/química , Fator 1 de Ribosilação do ADP/genética , Fator 1 de Ribosilação do ADP/metabolismo , Fatores de Ribosilação do ADP/metabolismo , Humanos , Membranas Intracelulares/química , Membranas Intracelulares/metabolismo , Bicamadas Lipídicas/química , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Membranas/química , Membranas/metabolismo , Ácido Mirístico/metabolismo
16.
Molecules ; 24(3)2019 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-30759729

RESUMO

Membrane distillation (MD) has recently gained considerable attention as a valid process for the production of fresh-water due to its ability to exploit low grade waste heat for operation and to ensure a nearly feed concentration-independent production of high-purity distillate. Limitations have been related to polarization phenomena negatively affecting the thermal efficiency of the process and, as a consequence, its productivity. Several theoretical models have been developed to predict the impact of the operating conditions of the process on the thermal polarization, but there is a lack of experimental validation. In this study, electrospun nanofiber membranes (ENMs) made of Poly(vinylidene fluoride) (PVDF) and doped with (1, 10-phenanthroline) ruthenium (II) Ru(phen)3 were tested at different operating conditions (i.e., temperature and velocity of the feed) in direct contact membrane distillation (DCMD). The temperature sensitive luminophore, Ru(phen)3, allowed the on-line and non-invasive mapping of the temperature at the membrane surface during the process and the experimental evaluation of the effect of the temperature and velocity of the feed on the thermal polarization.


Assuntos
Sondas Moleculares/química , Nanofibras/química , Destilação/métodos , Água Doce/química , Membranas/química , Membranas Artificiais , Polivinil/química , Rutênio/química , Temperatura
17.
Mol Pharm ; 16(1): 448-461, 2019 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-30521350

RESUMO

The tendency of highly supersaturated solutions of poorly water-soluble drugs to undergo liquid-liquid phase separation (LLPS) into drug-rich and water-rich phases when the concentration exceeds the amorphous solubility, for example, during dissolution of some amorphous solid dispersions, is thought to be advantageous from a bioavailability enhancement perspective. Recently, we have developed a high surface area, flow-through absorptive dissolution testing apparatus that enables fast mass transfer providing more in vivo relevant conditions and time frames for formulation testing. Using this apparatus, the absorption behaviors of solutions with different extents of supersaturation below and above the amorphous solubility were evaluated. In addition, simultaneous dissolution-absorption testing of amorphous solid dispersions (ASDs) with varying drug loadings and polymer types was carried out to study and distinguish the absorption behavior of ASDs that do or do not undergo LLPS. When compared with closed-compartment dissolution testing, a significant influence of the absorptive compartment on the dissolution rate of ASDs, particularly at high drug loadings, was observed. The formation of drug-rich nanodroplets, generated by both solvent-addition and ASD dissolution, resulted in a higher amount of drug transferred across the membrane. Moreover, the mass transfer was further enhanced with increasing concentration above the amorphous solubility, thereby showing correlation with an increase in the number of drug-rich particles. The importance of including an absorptive compartment in dissolution testing is highlighted in this study, enabling coupling of dissolution to membrane transport, and providing a more meaningful comparison between different formulations.


Assuntos
Liberação Controlada de Fármacos , Membranas/química , Cristalização , Polímeros/química , Solubilidade
18.
Biopolymers ; 110(1): e23241, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30536858

RESUMO

Cell or tissue stretching and strain are present in any in vivo environment, but is difficult to reproduce in vitro. Here, we describe a simple method for casting a thin (about 500 µm) and soft (about 0.3 kPa) hydrogel of gelatin and a method for characterizing the mechanical properties of the hydrogel simply by changing pressure with a water column. The gelatin is crosslinked with mTransglutaminase and the area of the resulting hydrogel can be increased up 13-fold by increasing the radial water pressure. This is far beyond physiological stretches observed in vivo. Actuating the hydrogel with a radial force achieves both information about stiffness, stretchability, and contractability, which are relevant properties for tissue engineering purposes. Cells could be stretched and contracted using the gelatin membrane. Gelatin is a commonly used polymer for hydrogels in tissue engineering, and the discovered reversible stretching is particularly interesting for organ modeling applications.


Assuntos
Gelatina/química , Hidrogel de Polietilenoglicol-Dimetacrilato/química , Polímeros/química , Engenharia Tecidual , Gelatina/síntese química , Hidrogel de Polietilenoglicol-Dimetacrilato/síntese química , Fenômenos Mecânicos , Membranas/química , Polímeros/síntese química , Transglutaminases/química , Água/química
19.
Int J Biol Macromol ; 125: 503-509, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30537501

RESUMO

Modification of chitosan with cross-linkers, blends with various kinds of polymers, nanoparticles and new organic-inorganic hybrid composites in order to obtain some improved properties attached more attention nowadays due to their good sensitivity in changing electrical and optical properties. In the current work modified hybrid chitosan/calcium aluminosilicate (CH/CAS) nanocomposite membranes and doped with (3, 5 & 7 mol%) Al2O3 nanoparticles were synthesized via sol-gel process in acidic conditions, which can be efficiently employed to capture CO2 gas at lower and moderate temperatures. Furthermore, the fabricated CH/CAS nanocomposite membrane loading with (3, 5 & 7 mol%) Al2O3 were investigated using XRD, SEM, FTIR and dielectric measurements. The results indicated that the incorporation of Al2O3 in CH/CAS matrix significantly affected on the structural, dielectric and appeared good reliability for sensing CO2 at atmospheric pressure. The dielectric behaviour for the prepared CH/CAS indicates that the dielectric constant (ε') decreases. According to XRD the introducing of Al2O3 leads to increase the crystallinity of the system and thus the dipoles of the system orient hardly with the applied field and results in lesser dielectric constant (ε'). Correspondingly, the CH/CAS nanocomposite membranes were characterized and its performance as CO2 gas sensor was evaluated.


Assuntos
Aluminossilicato de Cálcio/química , Dióxido de Carbono/química , Quitosana/química , Géis/química , Membranas/química , Nanocompostos/química , Nanopartículas/química , Polímeros/química , Temperatura
20.
J Investig Clin Dent ; 10(1): e12380, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30525301

RESUMO

AIM: The aim of the present study was to develop a bovine pericardium biomembrane (BPB) and to evaluate pulp response in vivo. METHODS: A double-layer bovine BPB/chitosan was manufactured, and the porous chitosan side was coated with calcium hydroxide. The microstructure of the matrices was evaluated with electron microscopy. To test pulp response, cavities were prepared on the occlusal surface of Wistar rats' mandibular left first molars and capped with matrices, followed by appropriate adhesives/composite restorations. The animals were divided into three groups: group 1, calcium hydroxide alone; group 2, BPB without calcium hydroxide; and group 3, BPB coated with calcium hydroxide. Specimens were processed and histologically evaluated at 7, 14, and 30 days, postoperatively. RESULTS: Electron microscopy showed porous chitosan surface and a cohesive calcium hydroxide layer. Histological analysis showed that groups 1 and 3 had mild odontoblast layer disorganization, but normal pulp tissue appearance at 7, 14, and 30 days. At the same time points, group 2 showed a loss of general pulp tissue, pulp necrosis, and periapical abscess in some teeth. CONCLUSION: Coated bovine pericardium-based biomembranes resulted in favorable outcomes in cases of pulp exposure after a 30-day observation period, and might protect against injuries caused by adhesive systems and composites.


Assuntos
Hidróxido de Cálcio/uso terapêutico , Capeamento da Polpa Dentária/métodos , Membranas/química , Pericárdio , Tratamento do Canal Radicular/métodos , Animais , Hidróxido de Cálcio/efeitos adversos , Bovinos , Quitosana/química , Resinas Compostas/efeitos adversos , Cimentos Dentários , Polpa Dentária/patologia , Necrose da Polpa Dentária/patologia , Restauração Dentária Permanente/métodos , Masculino , Teste de Materiais , Modelos Animais , Dente Molar/patologia , Abscesso Periapical/patologia , Ratos , Ratos Wistar , Cimentos de Resina/efeitos adversos , Propriedades de Superfície , Fatores de Tempo
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