Chemically-active surface groups

The immobilization of enzymes on solid supports is the oldest of new biotechnologies. As for most of the chemical applications, the uses in this field require a multi-step modification. As a first layer a simple silane, mostly APTS, is used. In order to minimize sterical hindrance in the ultimate application reaction, a spacer molecule is often introduced between the active surface group and the immobilizing species. This may either be introduced at once, using a long-chain functional silane, or in a second step, after silanization. 

A filler can offer small particle size and high surface area but still provide relatively poor reinforcement if it has low specific surface activity. Filler which has chemically active surface that formed by various chemical groups such as hydroxyl, carboxyl, quinone, phenol and lactone groups provides good interaction between rubber and filler generally is related to the formation of strong covalent bonding. The physical surface such as porosity will increase the surface activities. ... 

Development of conditional (or variable) surface charges involves chemical reactions in the interfacial layer. Therefore, the individual material features, (i.e., the chemical properties of both the potentially charged sohd material and the dissolved species) have to be considered. When a chemically reactive surface group is exposed to an aqueous solution, the surface may become charged due to a surface reaction (e.g., dissociation, association, complexation) if the aqueous solution contains the other reactant as a dissolved species. The charging process on variable-charge sites is determined by not only the quality and quantity of active sites but also the composition of aqueous solution. An elechical double layer develops around particles due to the distribution of ionic species between the solid-liquid interfacial layer and the equilibrium Uquid phase. 

Fig. 3.16 Formation of porous pol5uners with chemically active surfaces. The shaded circles represent diamine groups of polar side chains of polymerizable surfactant which absoibs/adsoibs into or onto water pools solubilized (dispersed) in styiene/divinyl benzene mixture (after [54])...

Adsorption The attachment of charged particles to the chemically active group on the surface and in the pores of an ion exchanger. 

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... 

The pore structure and surface area of carbon-based materials determine their physical characteristics, while the surface chemical structure affects interactions with polar and nonpolar molecules due to the presence of chemically reactive fimctional groups. Active sites—edges, dislocations, and discontinuities—determine the reactivity of the carbon surface. As shown in Fig. 1, graphitic materials have at least two distinct types of surface sites, namely, the basal-plane and edge-plane sites [11]. It is generally considered... 

Another approach to producing latexes with chemically bound surface-active groups is to use a reactive surfactant—a surfactant with a polymerizable double bond, such as sodium dodecyl allyl sulfosuccinate [Wang et al., 2001a,b,c]. Copolymerization of the reactive surfactant with the monomer of interest binds the surface active groups into the polymer chains. 

Because surfaces of ribosomal particles have a variety of potential binding sites for such clusters, attempts are in progress to bind heavy-atoms covalently to a few specific sites on the ribosomal particles prior to crystallization. This may be achieved either by direct interaction of a heavy-atom cluster with chemically active groups such as -SH or the ends of rRNA on the intact particles or by covalent attachment of a cluster to natural or tailor-made carriers that bind specifically to ribosomes. 

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