Search results for "permeation"
showing 10 items of 274 documents
Thermodynamics and kinetics of ion permeation in wild-type and mutated open active conformation of the human α7 nicotinic receptor
2020
Molecular studies of human pentameric ligand-gated ion channels (LGICs) expressed in neurons and at neuromuscular junctions are of utmost importance in the development of therapeutic strategies for neurological disorders. We focus here on the nicotinic acetylcholine receptor nAChR-α7, a homopentameric channel widely expressed in the human brain, with a proven role in a wide spectrum of disorders including schizophrenia and Alzheimer's disease. By exploiting an all-atom structural model of the full (transmembrane and extracellular) protein in the open, agonist-bound conformation we recently developed, we evaluate the free energy and the mean first passage time of single-ion permeation using …
Multiple Mass Transfers of Small Volatile Molecules Through Flexible Food Packaging
2007
This article deals with evolution of packed foodstuff quality with time of storage. The transport of small volatile molecules (flavor compounds, water vapor, and gases) into and through flexible food packaging materials is reviewed, as well as their multiple transfers. Sorption, diffusion, and permeation phenomena are distinguished. Transport properties are largely determined by packaging characteristics, flavor molecules properties, food matrix composition, and environmental conditions. Transfer of small volatile molecules into and through food packaging materials can modify food quality and properties of the packaging materials, thus possibly altering packed foodstuff shelflife. More rese…
Isolation of a peptidic fraction from the goat cheese water-soluble extract by nanofiltration for sensory evaluation studies
1997
Abstract The effect of the small water-soluble peptides on the taste of cheeses has not been clarified yet because of the high difficulties to isolate them from the other water-soluble compounds. A new filtration method, nanofiltration, using ionizable membranes, allowed us to purify a peptidic fraction prepared from the permeate obtained by ultrafiltration (MWCO=1000) of a goat cheese water-soluble extract. A large proportion of mineral salts and a part of amino acids were eliminated from the nanofiltration retentate where a majority of small peptides were concentrated. The peptidic fraction was incorporated in a cheese model with known synergistic effectors such as mineral salts and amino…
Human artificial membranes in (bio)analytical science: Potential for in vitro prediction of intestinal absorption-A review
2021
Abstract Artificial membranes for investigation of the human absorption (oral, dermal or respiratory) of target organic compounds are aimed at mimicking the interactions occurring at and within the cell lipid membrane. Biomolecules such as proteins are also integral components of the lipid membranes and play a pivotal role towards understanding the complex mechanisms of human absorption. In this review, we will differentiate biomimetic platforms based on static (batchwise) and dynamic modes. In the former, a synthetic membrane placed between two phases (donor and acceptor) mimics a given biological system to study permeability. Parallel artificial membrane permeation assays are the most com…
From macroscopic to molecular scale investigations of mass transfer of small molecules through edible packaging applied at interfaces of multiphase f…
2009
Abstract This paper presents a multi-scale approach to investigate mass transfer properties of edible films that integrates some published data and new original results. The transport of small molecules, such as water, between the different parts of multiphase food products leads to quality deterioration and thus requires the use of barrier edible films or coatings. Therefore, it is necessary to characterise the properties of both food and edible barriers, like the diffusivities of their respective migrants. Surface properties characterisation of edible films, composed of an iota-carrageenan matrix in association with a high melting point fat was investigated by goniometry and allows the de…
Synthesis and characterization of well-defined poly(tert-butyl acrylate) star polymers
2009
Abstract Star polymers with different numbers and lengths of poly(tert-butyl acrylate) (PTBA) arms were obtained via atom transfer radical polymerization. Aliphatic alcohols with different number of hydroxyl groups varying from 3 to 6 and calix[4]arenes based on pyrogallol with 12 and 16 phenol groups were transformed to bromoester derivatives to prepare multifunctional ATRP initiators used as the cores of the stars. The star polymers were characterized by GPC with refractive index, multiangle laser light scattering and viscosimetric detectors. The molar masses of the stars reached 70,000 g/mol and the molar mass dispersities did not exceed 1.2. To elucidate the compact structure of the sta…
Transport mechanism of peptides through supported liquid membranes
2007
Abstract The transport of selected dipeptides through supported liquid membranes impregnated with di(2-ethylhexyl) phosphoric acid in n-dihexylether has been investigated. The fluxes depend on the side chain of amino acids, presence in the peptide structure. The highest fluxes were obtained for the peptides extracted with the highest efficiency. It has been found that the hydrophobicity of investigated peptides, was not the major factor, influences their SLM permeation. In the conditions studied, it has been observed that the transport of peptide–carrier complex was depending on the acidic–basic properties of the analyte. The linearly least-square fittings of log {K1 + [H+]D} and log[(HR)2]…
Solution properties of polyelectrolytes
1993
Abstract Aqueous size-exclusion chromatography was used to analyse the elution behaviour of several standard ionic polymers, including poly( l -glutamic acid), sodium poly(styrene sulphonate) and poly(acrylic acid), different in nature and chain flexibility, as a function of the pH and ionic strength of the eluent. Two organic-based hydrophilic packings, Spherogel TSK PW4000 and Ultrahydrogel 250, were tested in order to select the optimal conditions of macromolecular separation, and the results obtained for each column were compared. A set of calibration graphs for the above polyions as a function of eluent pH and ionic strength were obtained and compared with those obtained for uncharged …
Cell Adhesive and Antifouling Polyvinyl Chloride Surfaces Via Wet Chemical Modification
2012
Polyvinyl chloride (PVC) is one of the most frequently used polymers for the manufacturing of medical devices. Limitations for its usage are based upon unfavorable surface properties of the polymer including its hydrophobicity and lack of functionalities in order to increase its versatility. To address this issue, wet chemical modification of PVC was performed through surface amination using the bifunctional compound ethylene diamine. The reaction was conducted in order to achieve maximum surface amination while leaving the bulk material unaffected. The initial activation step was characterized by means of various methods including contact angle measurements, colorimetric amine quantificati…
Zur kinetik des einstellvorganges im osmometer. IV. Bestimmung des zahlenmittels des molekulargewichts bei unfraktionierten polymeren1
1962
Der durch teilweise Permeation bedingte Fehler des gemessenen osmotischen Druckes eines unfraktionierten Polymeren kann berechnet werden, wenn die fur das Permeationsverhalten masgebenden Konstanten der Membran und die molekulare Verteilungsfunktion des Polymeren bekannt sind. Unter diesen Voraussetzungen wird unter Verwendung fruher abgeleiteter Beziehungen1 der durch Gl. (1) definierte Fehlbetrag Δt berechnet. Ist die spezielle Verteilungsfunktion nicht bekannt, so kann der Fehlbetrag fur ein bestimmtes Polymeres abgeschatzt werden, wenn auser einer osmotischen Mesreihe eine Bestimmung des Gewichtsmittels des Molekulargewichts Mw (bzw. Pw) vorliegt. Voraussetzung der Rechnung ist die Kenn…