Monomolecular film technique

Ransac, S., Rogalska, E., Gargouri, Y., Deveer, A. M. T. J., Paltauf, F., De Haas, G. H., and Verger, R. 1990. Stereoselectivity of lipases I. Hydrolysis of enantiomeric glyceride analogues by gastric and pancreatic lipases, a kinetic study using the monomolecular film technique. J. Biol. Chem., 265, 20263-20270. 

The efficacy of orlistat in inhibiting HPL acting on PSO was found to be higher when using the monomolecular film technique as compared to the single oil drop technique. 

Rogalska, E., Nury, S., Douchet, 1. and Verger, R. (1995) Lipase stereoselectivity and regioselectivity toward three isomers of dicaprin A kinetic study by the monomolecular film technique. Chirality 7, 505-515... 

A recent report describes the radioactive labeled chromium (iii) ion adsorption on stearic acid LB films. The adsorption of chromium (iii) on a stearic acid monolayer on the surface of CrCl3 was described. Stearic acid monomolecular films on I0 3 M CaCl2 subsolutions were deposited in paraffin-coated microscope glass slides by the LB technique (pH range 2-9). 

Monolayer Films of Phthalocyanine Derivatives. A series of organic derivatives of phthalocyanines were prepared that have two important characteristics of materials to be deposited by the Langmuir-Blodgett technique (1) they are soluble in volatile organic solvents, and (2) they form monomolecular films on the surface of water. Further study of deposited films of these phthalocyanine derivatives will be necessary in order to determine the exact orientations on the surface, but regardless of their orientations, they offer interesting possibilities for construction of thin films of ordered arrays of molecules on the surface of gas sensors. 

If a small amount of protein solution is suitably spread at the surface of an aqueous substrate, most of the protein will be surface-denatured, giving an insoluble monomolecular film before it has a chance to dissolve. The techniques already described for studying spread monolayers of insoluble material can, therefore, be used in... 

Emphasis was first placed on the adsorptive behavior of Compound D on the surface of chromium because that metal has the following desirable properties (a) it is an excellent adsorbent for carboxylic acid groups (5) (b) a large body of data is available on the properties of adsorbed, monomolecular films of aliphatic (16), partially fluorinated (13), fully fluorinated (2), and chloro-fluoro carboxylic acids (2) (c) the metal surface can be readily and reproducibly cleaned by standard metal-lographic polishing techniques and (d) there is a hard, coherent, thin-film oxide on the surface (18). 

A very versatile approach to the formation of multilayer films has been developed by Decher, based on polyelectrolytes. If a solid substrate with ionic groups at the surface is dipped into a solution of a complementary polyelectrolyte, an ultrathin, essentially monomolecular film of the polyion is adsorbed [340]. The adsorption is based on pairing of surface bound ionic sites with oppositely charged ions, bound to the macromolecule. The polymers adsorb in an irregular flattened coil structure and only part of the polymer ions can be paired with the surface ions (Figure 29a). Ionic sites which remain with small counterions provide anchor points for a next layer formed by a complementary polyelectrolyte [342,343]. This way multilayer polyelectrolyte films can be prepared layer-by-layer just by dipping a suitable substrate alternately in an aqueous solution of polyanions and polycations. The technique can be employed with nearly all soluble charged polymers and results in films with a... 

T. Smith, MonomolecuLar Films on Mercury, Adv. Colloid Interface Set 3 (1972) 161-22. (Review techniques, including electriced ones, examples for various simple molecules in the interfaces.)... 

The monolayer technique was also used to study the covalent inhibition of lipases using mixed monomolecular films of substrate containing amphiphilic inhibitor molecules and using a zero order trough with a reaction compartment containing the mixed substrate/inhibitor film whereas the reservoir compartment was covered with a film of pure substrate [44, 57]. 

An ordered arrangement of GOD and ferrocene on a platinum electrode has been obtained by using the Langmuir-Blodgett (LB) technique (Moriizumi et al., 1988). Monomolecular films on electrodes were made by mixing the mediator with lipid followed by adsorption of GOD on the film at the trough surface. The quantity of GOD could be flexibly controlled by the number of LB films, thus giving sensors of different sensitivity. 

The investigation of solution and surface film properties of two- or three-component liquid solutions is the subject of this chapter. In one extreme, the components in the liquid solution are completely miscible giving a one-phase solution, and in the other extreme, the components are almost completely immiscible, and an insoluble monomolecular film of one component forms on the surface of the other giving a two-phase solution. Between these two extremes, different kinds of films form on the solution surfaces depending on the extent of molecular interactions between the components. The theoretical approaches and experimental techniques that are applied to these solution types will be described in Chapters 5 and 6 respectively. 

In the LB technique, a monolayer of amphiphilic molecules, prepared at the air-water interface, is transferred to a substrate, thus giving a monomolecular film. The molecules must be solvable in a volatile, water-insoluble (organic) solvent, but not, or to a very limited extent, in water. Thus, when the solution of the molecules in the organic solvent is spread over the surface of water, the solvent evaporates, leaving a monolayer of molecules at the air-water interface. This monolayer can be compressed and transferred to a substrate. When the molecules are replaced by colloidal, nanosized particles, monolayers of these particles on a substrate are obtained. Smectites are especially well suited for the LB technique. The elementary clay sheets are about 1 nm thick and a few tens to hundreds nm wide and long. In the alkali- or alkaline earth form, they are hydrophilic, but by ion exchange with suitable amphiphilic cations, they become hydrophobic. There are then two ways to prepare mono-layers of smectite clay particles by the LB technique. 

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