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(cell and molecular biology)
A submicroscopic structural unit of protoplasm built up from polymeric molecules.
(physical chemistry)
A colloidal aggregate of a unique number (between 50 and 100) of amphipathic molecules, which occurs at a well-defined concentration known as the critical micelle concentration.



a particle of the disperse phase of a sol, that is, of a highly disperse colloidal system with a liquid dispersion medium.

Micelles consist of nuclei of crystalline or amorphous structure and of a surface layer containing solvated molecules of the liquid medium. The surface layer of a micelle of a lyophilic sol is formed of adsorbed molecules or ions of a stabilizer. In the case of lyophobic hydrosols stabilized by electrolytes, the nucleus of the micelle is surrounded by two layers of oppositely charged ions (the electric double layer). There is an equal number of positive and negative charges in the electric double layer; the micelle as a whole is therefore electrically neutral.

The ions of the adsorption layer are located directly on the surface of the nucleus. All ions of one of the signs and some of those of the opposite sign (counterions) are part of this layer. The remainder of the counterions form the diffuse layer, which surrounds the micelle as an ionic cloud whose density decreases with increasing distance from the nucleus. The diffuse layer hinders the approach and aggregation (cohesion) of particles in Brownian motion.

In lyophilic sols and colloidal dispersions of the soap hydrosol type (for example, of sodium oleate or potassium lauryl sulfate), the micelles are molecular aggregates. In each molecule a long hydrocarbon (hydrophobic) chain is bound to a polar (hydrophilic) group. In forming the micelle, dozens or even hundreds of molecules aggregate, so that the hydrophobic radicals form the nucleus (inner region) and the hydrophilic groups form the surface layer. If the dispersion medium is an organic liquid, the orientation of the molecules in the micelle may be reversed. The polar groups concentrate in the nucleus, and the hydrophobic radicals are directed toward the external phase.

The simplest structural types of micelles may be diagramed with the micelle-forming molecule represented as a wavy line (hydrophobic chain) with a small circle (hydrophilic group) at the end (see Figure 1).

Figure 1. Basic micelle types

Micelle structures (1) and (2) represent hydrophilic sols; types (3) and (4), organophilic sols. Upon dilution of the system below the critical micelle-formation concentration, spherical micelles (1) and (3) decompose reversibly into separate molecules or dimers. At higher concentrations, they are converted into lamellar micelles, represented by types (2) and (4); these may interact to form a structural gel network within the system.

The detergent action of aqueous solutions (more precisely, of colloidal dispersions) of soaps, as well as certain phenomena in biological systems and technological processes, are explained by the presence of micelles.


References in periodicals archive ?
FOR REMOVING HEAVY MAKE-UP Clinique Take The Day Off Micellar Cleansing Towelettes, PS16 Pricey, but larger size and extra-saturated formula means they get off even waterproof mascara without a fight.
Sw and Sm are substrates in aqueous and micellar pseudo phase respectable; K'w and K'm are the related first order rate constants and Ks is the binding constant (Domingos et al.
Drug-surfactant binding constant and micelle-water partition coefficient are useful parameters for the quantitative evaluation of the micellar effect on the properties of pharmaceutical drugs[31, 32], which in turn helps in understanding the drug structure-activity relationships as well as its interaction with the biological membranes [33].
This scheme represents the micellized surfactant as Dn where [Dn] = [D] - CMC and [D] is the concentration of surfactant where m and w refer to the micellar and aqueous pseudophases, respectively.
For graduate students and professionals in bioengineering and chemical, environmental, civil, agricultural, and industrial engineering, De, who teaches chemical engineering at the Indian Institute of Technology, and Mondal, who is pursuing a master's degree in chemical engineering there, outline the benefits and use of micellar enhanced ultrafiltration (MEUF) as an alternative to other methods (such as membrane-based techniques) to achieve continuous removal of organic and inorganic pollutants from waste emerging from various industries.
Micellar catalysts of reactions are important due to their industrial applications pertinence to biological processes and analytical chemistry and also because of the parallel behavior of biological macro-molecules and enzymes.
The Commissioner of the Japan Patent Office granted the company a patent titled "Mixed Micellar Pharmaceutical Delivery System and Method of Preparation.
Their topics include the pharmacological importance of chiral separations, cyclodextrin-mediated chiral separations, macrocyclic antibiotics as chiral selectors, chiral ligand exchange capillary electrophoresis, chiral separations by micellar electrokinetic chromatography, quantitative analysis in pharmaceutical analysis, analyzing chiral drugs in body fluids, enantioseparations by capillary electrochromatography, and chiral separations with microchip technology.
Our previous paper was on the kinetics of the reduction of dithiazone by sulphite ions [15] in micellar media and now we have attempted to explore the use of micellar media for the kinetics of the reduction of azo compounds by stannous chloride in aqueous medium.
The Australian Patent Office has granted the Company a patent titled Micellar Pharmaceutical Compositions for Buccal and Pulmonary Application.
BIREFRINGENT visualization of the micellar fluid layer around a diagonally oriented square "cutting tool.
The researchers obtained native micellar casein and soy protein isolates using membrane separation.