Physical immobilisation

A spread requires an emulsifier in order to be produced and is essentially formed by crystallised fat physically immobilising water droplets. As the amount of fat is decreased then the amount of water increases. 

A number of biomolecules have been physically immobilised on conducting polymers [66,112, 116-119]. This is the simplest method of enzyme immobilisation. Since the binding forces involved are hydrogen bonds, van der Waals forces, etc., porous conducting polymer surfaces are most commonly used. The pre-adsorption of an enzyme monolayer prior to the electrodeposition of the polymer, [120] and two-step enzyme adsorption on the bare electrode surface and then on PPy film [121] have also been investigated. 

In preparing immobilised cells, 1.5, 2, 3 and 6% alginate was used. By pressing them manually, the hardness and rigidity of the beads were tested. The physical criteria of the... 

Selection of columns and mobile phases is determined after consideration of the chemistry of the analytes. In HPLC, the mobile phase is a liquid, while the stationary phase can be a solid or a liquid immobilised on a solid. A stationary phase may have chemical functional groups or compounds physically or chemically bonded to its surface. Resolution and efficiency of HPLC are closely associated with the active surface area of the materials used as stationary phase. Generally, the efficiency of a column increases with decreasing particle size, but back-pressure and mobile phase viscosity increase simultaneously. Selection of the stationary phase material is generally not difficult when the retention mechanism of the intended separation is understood. The fundamental behaviour of stationary phase materials is related to their solubility-interaction... 

GFP was immobilised into SBA-15 and on Aerosil OX-50 (Degussa) by physical adsorption. The latter is one of the commercially available products of Si02, and it consists entirely of a highly dispersed amorphous silica (SSA ca. 50 m2/g). Generally, siloxane and silanol groups are situated on the surface of Aerosil nanoparticles and the latter are responsible for its hydrophilic behaviour [4]. 

To our knowledge, none of the developed SLP and SAP catalysts made their way into a technical process. Obviously, the possibility of using a supported liquid catalyst in a continuous liquid phase reaction is generally very restricted. The reason is that a very low solubility of the liquid in the feedstock/product mixture is enough to remove the catalyst from the surface over time (due to the very small amounts of liquid on the support). Even worse, the immobilised liquid film can be removed from the support physically by the mechanical forces of the continuous flow even in the case of complete immiscibility. 

Liquid fluidization is the basis of both the Oslo (or Krystal) continuous crystalliser (Mullin, 1993) which is used in the production of, for example, sugar or citric acid, and the bioreactors in which immobilised cells or enzymes are fluidized by the reactant solution (Epstein, 2003). It is used in the leaching of vegetable oils from seeds (Rios et al, 1985 Epstein, 2003) and in physical operations such as the washing and preparation of vegetables. 

Various strategies have been developed for the immobilisation of the affinity partner, among which physical adsorption as well as covalent binding are used, either to coat the walls of the reaction chamber, or to functionalise beads that are put in contact with the analyte solution or even in some cases to create a biologically modified membrane or electrode. 

In order to demonstrate the performance of this electrochemical microimmunoassay platform in terms of limits of detection and dynamic range, a series of ALP tests has been conducted in 100 nL polyimide microchips. To this end, anti-phosphatase antibodies have first been immobilised on the surface of the microchannels at a concentration of 10 pg/mL in a flow-through mode (4mL of anti-ALP solution pumped at 0.4 mL/min during 10 min) so as to saturate the microchannel surface by physical adsorption. Then, the surface was blocked with a 5% BSA in phosphate buffer in order to block the free sites remaining on the surface. Solutions of ALP at various concentrations (namely 0, 0.1, 1, 10 and 100 pM) were then injected and incubated during 9 min in the... 

Sometimes much greater amounts of solvent can be immobilised by mechanical entrapment within particle aggregates. This occurs when voluminous flocculent hydroxide precipitates are formed. In solutions of long thread-like molecules the polymer chains may cross-link, chemically or physically, and/or become mechanically entangled to such an extent that a continuous three-dimensional network is formed. If all of the solvent becomes mechanically trapped and immobilised within this network, the system as a whole takes on a solid appearance and is called a gel. 

The frequency of the chain motions of one of the two types of chain units, inferred from the minimum Tj around 195 K (-78 °C), is similar to that observed in unfilled PDMS. The mobility of the chain units of the other type is greatly hindered, resulting in a T1 minimum at higher temperature (at about 7 °C). This minimum becomes more pronounced in proportion to the total surface of filler particles in the mixture. It was suggested that the observed chain immobilisation is caused mainly by physical adsorption of PDMS chain units adjacent to the silica surface and to a lesser extent by entropy constraints at the silica surface [113]. 

Conjugated linoleic acid (CLA) may have a role in improving the nutritional and health properties of milk fat (Wahle et al., 2004 see Chapter 3). A range of lipases was compared for their efficacy of catalysing the incorporation of CLA into milk fat in solvent-free systems (Garcia et al., 2000). It was concluded that it was technically feasible to incorporate CLA into milk fat with the use of immobilised Candida antarctica lipase. However, the nutritional benefits and physical properties of the CLA-enriched milk fat need to be investigated prior to consideration of this technology for industrial application. 

Immobilisation of the chiral auxiliary on a polymeric support leads to ee s comparable to that obtained in homogeneous conditions.3 5 However, rates are lower and limitations reliable to the mechanical stability and stirring difficulties are described.6 Inorganic oxides may be preferred as supports because of their rigid structure and then-physical stability.7 10... 

Highly Lewis-acidic chloroaluminate ionic liquids (ILs) are well known to be both versatile solvents and effective catalysts for Friedel-Crafts reactions [1,2]. Tailoring the physical and chemical properties of the ILs to the needs of a specific reaction allows for a high diversity of applications [3,4]. We could show that immobilising these ILs on inorganic supports yields very active catalysts for alkylation reactions. The immobilisation of ionic liquids leads to novel Lewis-acidic catalysts (NLACs). The methods presented include the method of incipient wetness (method 1, further on called NLAC I), which has been introduced in detail by Hoelderich et al. f5], but focus of this presentation lies on the methods 2 (NLAC II) and 3 (NLAC III). 

Kumar and Landry217 used 31P SS NMR for the examination of the physical properties of the material obtained by immobilisation of the [PV2MoioC>4o] POM anion on the mesoporous MCM-41. The results obtained showed that the POM structure is intact after impregnation. The texture and structure of the support as a function of POM contents were studied, too. 

Advances in genetic and chemical enz)me modifications, enzyme immobilisation and enzymatic reactions in organic solvents, have increased the actual use and potential of enzymes in the production of industrial chemicals. Enzyme immobilisation, in particular, has proved to be a valuable approach to the use of enz5mes in chemical synthesis. The term denotes eirzymes that are physically confined or localised in a defined region in space with retention of their catalytic activities. A detailed consideration of immobilisation techniques is beyond the scope of this chapter the subject is covered adequately in the BKDTOL text entitled Technological Applications of Biocatalysts. ... 

Hrabakova, J., Ataka, K., Heberle, J., Hildebrandt, P., and Murgida, D.H. (2006) Long distance electron transfer in cytochrome c oxidase immobilised on electrodes. A surface enhanced resonance Raman spectroscopic smdy. Physical Chemistry Chemical Physics, 8, 759-766. 

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