The Effect of Nonionic Surfactant Micelles Or Microemulsions on Brush Border Membranes PDF Download

Author: Merav Edan
Publisher:
ISBN:
Category :
Languages : en
Pages : 250

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Author: William M. Gelbart
Publisher: Springer Science & Business Media
ISBN: 1461383897
Category : Science
Languages : en
Pages : 620

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Book Description
Over the last decades, the study of surfactants (detergents, for example) has been profoundly changed by ideas and techniques from physics, chemistry, and materials science. Among these are: self assembly; critical phenomena, scaling, and renormalization; high-resolution scattering, and magnetic resonance spectroscopy. This book represents the first systematic account of these new developments, providing both a general introduction to the subject as well as a review of recent developments. The book will be a very useful tool for the biophysist, biochemist or physical chemist working in the field of surfactants.

Author: Carolina Bianco
Publisher: ProQuest
ISBN: 9780549812203
Category : Membrane proteins
Languages : en
Pages :

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Book Description
Membrane proteins are characterized by their extensive hydrophobic surface area designed to interact with the lipid bilayer. These proteins provide functionality to the cell membrane by stabilizing this interface, acting as selective transporters and receptors. Because of their central role in communications between the cell and its environment, membrane proteins are common targets for pharmaceuticals. Nonionic surfactants are commonly used amphiphiles that can serve to shield the hydrophobic surface area of membrane proteins and allow their solubilization in aqueous solutions, resulting in the formation of protein-detergent complexes. The ideal surfactant is able to maintain the physiological function and structure of a target membrane protein in solution, therefore preventing unfolding and aggregation. Currently, trial and error is necessary to determine the best nonionic surfactant for each membrane protein target. This thesis focuses on the role of nonionic surfactants in the folding and stability of integral membrane proteins. Two points of view are considered: the role of the surfactant in establishing and stabilizing the protein structure, and the morphology and interactions of protein-detergent complexes. The main integral membrane protein under consideration was the outer membrane protein X, ompX, from E. coli, and its interactions were studied with polyoxyethylene nonionic surfactants noctyltetraoxyethylene (C 8 E 4), n-octylpentaoxyethylene, (C 8 E 5), n-dodecylhexaoxyethylene (C 12 E 6) and n-dodecyloctaoxyethylene (C 12 E 8). OmpX production was achieved through recombinant inclusion body expression in its native host, followed by purification in a denatured conformation. A rapid dilution refolding protocol was developed and was applied to compare the refolding of ompX in various nonionic surfactants. The final protein structure was determined from circular dichroism, fluorescence and FTIR spectroscopy analyses. The secondary structure of ompX was found to be very similar in all surfactants studied, and comparable to the estimates from its NMR structure and from the secondary structure of other refolded outer membrane proteins. Nonionic surfactants self-assemble into micelles in aqueous solutions at concentrations above the critical micelle concentration (CMC). Solutions of nonionic surfactants at concentrations above their CMC may display a phase separation with increasing temperature. The lowest temperature at which this separation can be detected is called the cloud point temperature (CPT). As the CPT is approached, micelle interactions can be considered to become more attractive or their morphology to become more elongated. In the process of understanding how surfactants can stabilize integral membrane proteins, it was necessary to examine how the chaotropic agent urea, commonly used in protein unfolding studies, affects surfactant phase behavior. Urea was found to increase the CMC of all polyoxyethylene surfactants studied significantly, as well as increase their CPT. The effect of urea on micelle morphology and interaction was probed by small-angle neutron scattering (SANS) experiments. It was found that micelles of C 8 E 4 and C 12 E 6 appeared elongated without urea in solution and become globular with increasing urea concentration. This effect was absent for C 8 E 5 and C 12 E 8 micelles, which remained globular independent of urea concentration. Therefore, we suggest an analogy between the effect of increasing urea concentration and decreasing temperature on the phase behavior of polyoxyethylene surfactants. The ability of nonionic surfactants to stabilize ompX in solution was tested by unfolding the PDC by increasing the urea concentration. Loss of protein structure was monitored by circular dichroism and fluorescence spectroscopies. Surfactant type and concentration were found to influence ompX unfolding. The protein stability was greatly diminished if the surfactant concentration fell below the CMC compared to when the surfactant concentration was adjusted to account for CMC changes with increasing urea concentration. The interactions and morphologies of ompX PDCs in solution with micelles of C 8 E 4, C 8 E 5, C 12 E 6 and C 12 E 8 surfactants with increasing urea concentration were examined by SANS. The challenge of these experiments was to distinguish the scattering of PDCs from that of micelles. Differences between the two sets of scattering curves are most prominent at urea concentrations below 2 M, and become small at urea concentrations at which ompX is denatured. These differences are more prominent in C 8 surfactants at 0 and 2 M urea, which contain elongated particles interpreted as aggregated PDCs. Simple models were applied to analyze the scattering of solutions containing PDCs and micelles but were unable to capture the entire scattering curves within physically realistic parameter constraints.

Author: Arun K. Chattopadhyay
Publisher: CRC Press
ISBN: 1000105415
Category : Science
Languages : en
Pages : 434

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Contains selected invited papers presented at the 10th International Symposium on Surfactants in Solution held in Caracas, Venezuela. The volume covers phase behaviour of monolayers, contact angle hysteresis, micellar relaxation, micellar catalyzed reactions, polymerization in microemulsions, polymer-surfactant complexation, asphaltenes, and more.

Author: Ron Liu
Publisher: CRC Press
ISBN: 1351646826
Category : Medical
Languages : en
Pages : 781

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Book Description
Properties and Formulation: From Theory to Real-World Application Scientists have attributed more than 40 percent of the failures in new drug development to poor biopharmaceutical properties, particularly water insolubility. Issues surrounding water insolubility can postpone or completely derail important new drug development. Even the much-needed reformulation of currently marketed products can be significantly affected by these challenges. More recently it was reported that the percentage increased to 90% for the candidates of new chemical entities in the discovery stage and 75% for compounds under development. In the most comprehensive resource on the topic, this third edition of Water-Insoluble Drug Formulation brings together a distinguished team of experts to provide the scientific background and step-by-step guidance needed to deal with solubility issues in drug development. Twenty-three chapters systematically describe the detailed discussion on solubility theories, solubility prediction models, the aspects of preformulation, biopharmaceutics, pharmacokinetics, regulatory, and discovery support of water-insoluble drugs to various techniques used in developing delivery systems for water-insoluble drugs. This book includes more than 15 water-insoluble drug delivery systems or technologies, illustrated with case studies and featuring oral and parenteral applications. Highlighting the most current information and data available, this seminal volume reflects the significant progress that has been made in nearly all aspects of this field. The aim of this book is to provide a handy reference for pharmaceutical scientists in the handling of formulation issues related to water-insoluble drugs. In addition, this book may be useful to pharmacy and chemistry undergraduate students and pharmaceutical and biopharmaceutical graduate students to enhance their knowledge in the techniques of drug solubilization and dissolution enhancement.

Author: N.M. van Os
Publisher: Elsevier
ISBN: 0444600280
Category : Technology & Engineering
Languages : en
Pages : 627

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Book Description
The number of physico-chemical investigations of surfactants in solution, whether aqueous or nonaqueous, has dramatically increased in recent years. However, literature reports on surfactants in solutions are scattered over a plethora of scientific journals and books which differ widely in scope and readership. Such data are often difficult to retrieve because there have been no systematic compilations, with the exception of those for CMCs and for micelle aggregation numbers. The present compilation meets that need by covering, as completely as possible, the physico-chemical properties of selected series of homologous surfactants. These surfactants are in most cases isomerically pure, are well-known, and have been used in numerous academic and industrial studies. The properties include aggregation number, cloud point, CMC, 13C-NMR, correlation length, counterion binding, density, enthalpy of micelle formation, entropy of micelle formation, Gibbs' free energy of micelle formation, head group area, 1H-NMR, hydration number, Krafft temperature, melting point, micelle radius, microscopic viscosity, miscibility curve, partial molar volume, phase inversion temperature, refractive index, self-diffusion coefficient, surface tension, and upper critical temperature. The book also contains two- and three-component phase diagrams of many nonionic surfactants. The solvent is water in most cases; however, some data refer to properties in D2O, electrolyte solutions, and nonaqueous solvents. The variables are temperature and concentration. Where possible, the method of measurement is given. Data on the purity of the compounds and the accuracy of the measurement methods are not included, as these can easily be found in the original sources, which mostly date from the period 1970-1991 and are given at the end of each chapter. The Index section contains a compound index, a property index, a symbol index and a cross index which facilitate easy access to the data. This valuable collection of data will be of great use to anyone involved in Colloid and Surface Science, academics as well as industrial workers, and will stimulate further work.

Author: Milton J. Rosen
Publisher: Wiley-Interscience
ISBN:
Category : Science
Languages : en
Pages : 454

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Book Description
The Second Edition has been updated to reflect recent advances in our knowledge of theory and practices. New applications run the gamut from microelectronics and magnetic recording, to biotechnology and nonconventional energy conversion. There is a new chapter on the interactions between surfactants. New sections have been added, and original sections expanded, on such topics as ultralow liquid-liquid interfacial tension, microemulsions, miniemulsions, and multiple emulsions, liquid crystal formation, hydrotropy, and steric forces in the stabilization of dispersions. There is also new material on lime soap dispersing agents, fabric softeners, adsorption and wetting of solid surfaces--both equilibrium and nonequilibrium, the relationship between adsorption and micellation in aqueous solutions and its effect on surface tension reduction, and factors determining micellar structure and shape.

Author: Gregory Goodman Warr
Publisher:
ISBN:
Category : Surface active agents
Languages : en
Pages : 226

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Author: Milton J. Rosen
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 376

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Author: Wyatt Jacob Musnicki
Publisher:
ISBN: 9781267969217
Category :
Languages : en
Pages :

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The purpose of this work is to advance the understanding of the diffusive transport of hydrophobic compounds (pharmaceuticals, nutraceuticals, flavors, pesticides, etc.) solubilized in microemulsions and the particles that carry them through solution and in fibrous media. The first focus of this research was to investigate the gradient-diffusion of charged anionic micelles in solution and a fibrous gel at moderate but dilute concentrations above the critical micelle concentration. Of particular interest were the effects of micelle, gel, and sodium chloride concentration on the micelle diffusivity. Holographic interferometry was used extensively to measure the micelle gradient-diffusion coefficient as a function of surfactant concentration at multiple sodium chloride and gel concentrations. The micelle diffusivity was shown to increase linearly with surfactant concentration at the two larger sodium chloride concentrations and all gel concentrations. In general, the strength of this effect increased with decreasing sodium chloride concentration and increased with gel concentration. This behavior is evidence of decreasing micelle-micelle electrostatic interactions with increasing sodium chloride concentrations, and increasing excluded volume effects and hydrodynamic screening with increasing gel concentration, respectively. The extrapolated, infinite-dilution diffusion coefficients and the rate at which the micelle diffusivity increased with surfactant concentration were compared with predictions of previously published theories in which the micelles are treated as charged, colloidal spheres and the gel as a Brinkman medium. The experimental data and theoretical predictions were in good agreement, particularly at the higher salt concentrations. The second focus of this work was to investigate the gradient-diffusion of hydrophobic compounds in microemulsions. Three solutes of increasing hydrophobicity were used and two different types of surfactants, one non-ionic and the other anionic, were investigated. The transport of the hydrophobic compounds within the microemulsions were tracked using holographic interferometry. For three of the solute-surfactant pairs, the measured interferometry patterns exhibited pseudo-binary features and the effective binary diffusion coefficient of the solutes was extracted from these patterns. The effective diffusion coefficient of one solute-surfactant pair was between the slowest diffusing component, the micelle, and the fastest diffusing component, the solute in water. The other measured effective diffusivities were either much smaller than the micelle diffusivity or much larger than the solute's diffusivity in water. For the remaining three solute-surfactant pairs, the interferometric patterns clearly demonstrated the transport of more than two components. For these, the effective binary diffusion coefficients could not be extracted. To improve on the pseudo-binary results and to account for the coupled transport of solute, a ternary multicomponent method was adapted for use with holographic interferometry. The ternary diffusivities: D11, D12, D21, and D22 were determined for all sets of solutes and surfactants. The value of D22 were found to be in all cases equal to the micelle diffusivity. The values of D11 were found to be less than the solute's diffusivity in water and to decrease as the solute's hydrophobicity increased. The values of D12 and D21 were found to depend in a complex manner with the solute's hydrophobicity and the type of surfactant used. Holographic interferometry was a useful tool for extracting complex information from the transport mechanisms of the solute and surfactant gradient-diffusion in micelles and microemulsions.