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Biochimica Et Biophysica Acta Oct 2013Reverse micelles are a versatile model system for the study of crowded microenvironments containing limited water, such as those found in various tissue spaces or... (Review)
Review
Reverse micelles are a versatile model system for the study of crowded microenvironments containing limited water, such as those found in various tissue spaces or endosomes. They also preclude protein aggregation. Reverse micelles are amenable to study by linear and nonlinear infrared spectroscopies, which have demonstrated that the encapsulation of polypeptides and enzymatically active proteins into reverse micelles leads to conformational changes not seen in bulk solution. The potential value of this model system for understanding the folding and kinetic behavior of polypeptides and proteins in biologically important circumstances warrants increased study of reverse micelle systems by infrared spectroscopy. This article is part of a Special Issue entitled: FTIR in membrane proteins and peptide studies.
Topics: Micelles; Protein Conformation; Proteins; Spectrophotometry, Infrared
PubMed: 23098833
DOI: 10.1016/j.bbamem.2012.10.019 -
Journal of Dairy Science Jun 2019The colloidal properties of the casein micelles play a major role in the structural properties of milk protein concentrates. Because of their great technological... (Review)
Review
The colloidal properties of the casein micelles play a major role in the structural properties of milk protein concentrates. Because of their great technological importance, the structural-functional relationships of casein micelles have been studied for decades in skim milk; however, novel ingredients are now available with higher protein concentrations and varying in composition. The colloidal behavior of caseins in these systems is not fully understood. Concentrates prepared with membrane technologies, and subjected to pre- or post-modifications that affect their technological functionality, have become increasingly widespread. This has created large opportunities for innovation and generation of value-added ingredients. The manner in which caseins interact with themselves and the other components in these concentrates will affect the structure of the final matrix. During concentration by filtration, the interparticle distance between the micelles decreases considerably, increasing their spatial correlation and decreasing their diffusivity. Rearrangements occur due to changes in environmental conditions, such as ionic composition, osmotic stress, shear, pH, or heating temperature. This will have important consequences on bulk viscosity of the concentrates, as well as on the mode of formation of structures' building blocks. This paper aims at highlighting some of the important factors affecting the colloidal structure of casein micelles, their destabilization and network formation, namely, processing history, volume fraction, composition of the serum phase, and ionic equilibrium. Understanding these factors will lead to a better quality control of dairy ingredients and to the development of a new generation of ingredients with targeted functionality.
Topics: Animals; Caseins; Cattle; Micelles; Milk; Milk Proteins
PubMed: 30981474
DOI: 10.3168/jds.2018-15943 -
Pharmaceutical Research Dec 2010Micelles are colloidal particles with a size around 5-100 nm which are currently under investigation as carriers for hydrophobic drugs in anticancer therapy. Currently,... (Review)
Review
Micelles are colloidal particles with a size around 5-100 nm which are currently under investigation as carriers for hydrophobic drugs in anticancer therapy. Currently, five micellar formulations for anticancer therapy are under clinical evaluation, of which Genexol-PM has been FDA approved for use in patients with breast cancer. Micelle-based drug delivery, however, can be improved in different ways. Targeting ligands can be attached to the micelles which specifically recognize and bind to receptors overexpressed in tumor cells, and chelation or incorporation of imaging moieties enables tracking micelles in vivo for biodistribution studies. Moreover, pH-, thermo-, ultrasound-, or light-sensitive block copolymers allow for controlled micelle dissociation and triggered drug release. The combination of these approaches will further improve specificity and efficacy of micelle-based drug delivery and brings the development of a 'magic bullet' a major step forward.
Topics: Antineoplastic Agents; Clinical Trials as Topic; Drug Delivery Systems; Humans; Micelles; Neoplasms; Polymers
PubMed: 20725771
DOI: 10.1007/s11095-010-0233-4 -
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi =... Oct 2022Polymer micelles formed by self-assembly of amphiphilic polymers are widely used in drug delivery, gene delivery and biosensors, due to their special hydrophobic... (Review)
Review
Polymer micelles formed by self-assembly of amphiphilic polymers are widely used in drug delivery, gene delivery and biosensors, due to their special hydrophobic core/hydrophilic shell structure and nanoscale. However, the structural stability of polymer micelles can be affected strongly by environmental factors, such as temperature, pH, shear force in the blood and interaction with non-target cells, leading to degradations and drug leakage as drug carriers. Therefore, researches on the structural integrity and distribution of micelle-based carriers are very important for evaluating their therapeutic effect and clinical feasibility. At present, fluorescence resonance energy transfer (FRET) technology has been widely used in real-time monitoring of aggregation, dissociation and distribution of polymer micelles ( and vo). In this review, the polymer micelles, characteristics of FRET technology, structure and properties of the FRET-polymer micelles are briefly introduced. Then, methods and mechanism for combinations of several commonly used fluorescent probes into polymer micelles structures, and progresses on the stability and distribution studies of FRET-polymer micelles ( and ) as drug carriers are reviewed, and current challenges of FRET technology and future directions are discussed.
Topics: Micelles; Drug Carriers; Polymers; Fluorescence Resonance Energy Transfer; Polyethylene Glycols
PubMed: 36310492
DOI: 10.7507/1001-5515.202111040 -
Biophysical Journal Aug 2020The functional roles of the lipid asymmetry of biomembranes are attracting increasing attention. This study characterizes the activity of surfactants to induce...
The functional roles of the lipid asymmetry of biomembranes are attracting increasing attention. This study characterizes the activity of surfactants to induce transmembrane flip-flop of lipids and thus "scramble" this asymmetry. Detergent-induced lipid scrambling of liposomes mimicking the charge asymmetry of bacterial membranes with 20 mol % of 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-rac-glycerol in the outer leaflet only was quantified by ζ-potential measurements for octaethylene glycol dodecyl ether (CEO), octyl glucoside (OG), and dodecyl maltoside. Membrane leakage was separately measured by the fluorescence lifetime-based calcein leakage assay and the onset of the membrane-to-micelle transition by isothermal titration calorimetry. Partition coefficients and partial molar areas were obtained as well. For the quickly membrane-permeant CEO and OG, leakage proceeds at a rather sharp threshold content in the membrane, which is well below the onset of solubilization and little dependent on incubation time; it is accompanied by fast lipid scrambling. However, unlike leakage, flip-flop is a relaxation process that speeds up gradually from taking weeks in the detergent-free membrane to minutes or less in the leaking membrane. Hence, after 24 h of incubation, 10 mol % of CEO or 50 mol % of OG in the membrane suffice for virtually complete lipid scrambling, whereas leakage remains below 10% for up to 14 mol % of CEO and 88 mol % of OG. There is thus a concentration window in which lipid scrambling proceeds without leakage. This implies that lipid scrambling must be considered a possible mode of action of antimicrobial peptides and other membrane-active drugs or biomolecules. A related, detergent-based protocol for scrambling the lipid asymmetry of liposomes and maybe cells without compromising their overall integrity would be a very valuable tool to study functions of lipid asymmetry.
Topics: Calorimetry; Lipid Bilayers; Lipids; Liposomes; Micelles; Phosphatidylcholines
PubMed: 32738218
DOI: 10.1016/j.bpj.2020.07.004 -
Yakugaku Zasshi : Journal of the... 2011The world constructed by self-organization of some amphiphils was discussed on the basis of micelle formation, vesicle formation, and oriented-nano-wire formation.... (Review)
Review
The world constructed by self-organization of some amphiphils was discussed on the basis of micelle formation, vesicle formation, and oriented-nano-wire formation. First, the micelle formation of a both water- and oil- soluble surfactant, Aerosol OT, was discussed. Solution states of micelles and monomer were discussed on the basis of thermodinamic and NMR spectroscopic analyses of micelle formation. Next, micelle-vesicle transition was discussed. It was proposed that the phospholipid LUV formation by removing detergents and destruction by adding detergents occurred via 4 stages. The 4 stage model instead of the 3 stage model could not only elucidate the complicated phenomena observed during micelle-vesicle transition, but predicted the size and properties of the vesicles formed by detergent removal from mixed micelles. Next, the vesicle formation of a fatty acid with a single hydrophobic chain different from phospholipid, which has two hydorophobic chains, was discussed. The vesicle formation was strongly affected by the presence of preformed vesicles and the size was biased on the preformed vesicles. It was shown there exist two pass ways in the process of micelle-vesicle transition by pH jump. One is fission of the preformed vesicles after transfer of monomers from newly added oleate micelles and the other is transition from the mixed micelles after partial solubilization by the oreate micelles. Then, the vesicle formation of HCO-10, which has 3 hydrophobic chains, the mixed vesicle formation of phosphatidylethanolamine and lysophosphtidylcholine, which can not form vesicles, and the phospholipid vesicle formation and destruction by removing and adding PEG-lipid, were discussed. Lastly, oriented nano wire formation of mulamyldipeptid-conjugated lipids with ca 5 nm of diameter was discussed.
Topics: Dioctyl Sulfosuccinic Acid; Fatty Acids; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Micelles; Nanowires; Particle Size; Phospholipids; Solutions; Surface-Active Agents; Thermodynamics; Unilamellar Liposomes
PubMed: 22129875
DOI: 10.1248/yakushi.131.1765 -
Scientific Reports Oct 2022Improving boiling is challenging due to the unpredictable nature of bubbles. One way to enhance boiling is with surfactants, which alter the solid-liquid and...
Improving boiling is challenging due to the unpredictable nature of bubbles. One way to enhance boiling is with surfactants, which alter the solid-liquid and liquid-vapor interfaces. The conventional wisdom established by previous studies suggests that heat transfer enhancement is optimized near the critical micelle concentration (CMC), which is an equilibrium property that depends on surfactant type. However, these studies only tested a limited number of surfactants over small concentration ranges. Here, we test a larger variety of nonionic and anionic surfactants over the widest concentration range and find that a universal, optimal concentration range exists, irrespective of CMC. To explain this, we show that surfactant-enhanced boiling is controlled by two competing phenomena: (1) the dynamic adsorption of surfactants to the interfaces and (2) the increase in liquid dynamic viscosity at very high surfactant concentrations. This dynamic adsorption is time-limited by the millisecond-lifetime of bubbles on the boiling surface-much shorter than the timescales required to see equilibrium behaviors such as CMC. At very high concentrations, increased viscosity inhibits rapid bubble growth, reducing heat transfer. We combine the effects of adsorption and viscosity through a simple proportionality, providing a succinct and useful understanding of this enhancement behavior for boiling applications.
Topics: Surface-Active Agents; Adsorption; Micelles; Pulmonary Surfactants; Excipients
PubMed: 36307430
DOI: 10.1038/s41598-022-21313-1 -
Angewandte Chemie (International Ed. in... Apr 2022Responsive fluorescent materials offer a high potential for sensing and (bio-)imaging applications. To investigate new concepts for such materials and to broaden their...
Responsive fluorescent materials offer a high potential for sensing and (bio-)imaging applications. To investigate new concepts for such materials and to broaden their applicability, the previously reported non-fluorescent zinc(II) complex [Zn(L)] that shows coordination-induced turn-on emission was encapsulated into a family of non-fluorescent polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer micelles leading to brightly emissive materials. Coordination-induced turn-on emission upon incorporation and ligation of the [Zn(L)] in the P4VP core outperform parent [Zn(L)] in pyridine solution with respect to lifetimes, quantum yields, and temperature resistance. The quantum yield can be easily tuned by tailoring the selectivity of the employed solvent or solvent mixture and, thus, the tendency of the PS-b-P4VP diblock copolymers to self-assemble into micelles. A medium-dependent off-on sensor upon micelle formation could be established by suppression of non-micelle-borne emission background pertinent to chloroform through controlled acidification indicating an additional pH-dependent process.
Topics: Micelles; Polymers; Solvents
PubMed: 35129881
DOI: 10.1002/anie.202117570 -
Biochimica Et Biophysica Acta Nov 2000The interaction of surfactants with membranes has been difficult to monitor since most detergents are small organic molecules without spectroscopic markers. The... (Comparative Study)
Comparative Study Review
The interaction of surfactants with membranes has been difficult to monitor since most detergents are small organic molecules without spectroscopic markers. The development of high sensitivity isothermal titration calorimetry (ITC) has changed this situation distinctly. The insertion of a detergent into the bilayer membrane is generally accompanied by a consumption or release of heat which can be measured fast and reliably with modern titration calorimeters. It is possible to determine the full set of thermodynamic parameters, i.e., the partitioning enthalpy, the partitioning isotherm, the partition coefficient, the free energy, and the entropy of transfer. The application of ITC to the following problems is described: (i) measurement of the critical micellar concentration (CMC) of pure detergent solutions; (ii) analysis of surfactant-membrane partitioning equilibria, including asymmetric insertion; and (iii) membrane-surfactant phase diagrams. Finally, the thermodynamic parameters derived for non-ionic detergents are discussed and the affinity for micelle formation is compared with membrane incorporation.
Topics: Calorimetry; Lipid Bilayers; Micelles; Models, Theoretical; Permeability; Phospholipids; Solubility; Surface-Active Agents; Thermodynamics; Titrimetry
PubMed: 11090819
DOI: 10.1016/s0304-4157(00)00009-5 -
Frontiers in Bioscience (Landmark... Jan 2009A new theory of solutions, the method of energy representation, is introduced by adopting the solute-solvent interaction energy as the coordinate of distribution... (Review)
Review
A new theory of solutions, the method of energy representation, is introduced by adopting the solute-solvent interaction energy as the coordinate of distribution functions. The density-functional theory is formulated over the energy coordinate, and an approximate functional for the solvation free energy is given in terms of energy distribution functions in the solution and reference solvent systems. The method of energy representation greatly expands the scope of solution theory and is amenable to supercritical fluid, flexible molecules with intramolecular degrees of freedom, inhomogeneous system, and quantum-mechanical/molecular-mechanical (QM/MM) system. Through the combination with molecular simulation, the functional for the solvation free energy is demonstrated to perform well for nonpolar, polar, and ionic solutes in water over a wide range of thermodynamics conditions, with drastic reduction of the computational demand compared to the standard free-energy perturbation and thermodynamic integration methods. As an application to inhomogeneous system involving flexible species, the molecular binding into micelle and membrane is analyzed by treating micelle and membrane as a mixed solvent system consisting of water and amphiphilic molecule.
Topics: Membranes, Artificial; Micelles; Solubility; Thermodynamics
PubMed: 19273291
DOI: 10.2741/3469