Immobilization reactions

The Smoluchowski-Levich approach discounts the effect of the hydrodynamic interactions and the London-van der Waals forces. This was done under the pretense that the increase in hydrodynamic drag when a particle approaches a surface, is exactly balanced by the attractive dispersion forces. Smoluchowski also assumed that particles are irreversibly captured when they approach the collector sufficiently close (the primary minimum distance 5m). This assumption leads to the perfect sink boundary condition at the collector surface i.e. cp 0 at h Sm. In the perfect sink model, the surface immobilizing reaction is assumed infinitely fast, and the primary minimum potential well is infinitely deep. 

Besides the resuspension of particles, the perfect sink model also neglects the effect of deposited particles on incoming particles. To overcome these limitations, recent models [72, 97-99] assume that particles accumulate within a thin adsorption layer adjacent to the collector surface, and replace the perfect sink conditions with the boundary condition that particles cannot penetrate the collector. General continuity equations are formulated both for the mobile phase and for the immobilized particles in which the immobilization reaction term is decomposed in an accumulation and a removal term, respectively. Through such equations, one can keep track of the particles which arrive at the primary minimum distance and account for their normal and tangential motion. These equations were solved both approximately, and by numerical integration of the governing non-stationary transport equations. 

The previous models were developed for Brownian particles, i.e. particles that are smaller than about 1 pm. Since most times particles that are industrially codeposited are larger than this, Fransaer developed a model for the codeposition of non-Brownian particles [38, 50], This model is based on a trajectory analysis of particles, including convective mass transport, geometrical interception, and migration under specific forces, coupled to a surface immobilization reaction. The codeposition process was separated in two sub-processes the reduction of metal ions and the concurrent deposition of particles. The rate of metal deposition was obtained from the diffusion... 

High chemical stability at the conditions required for immobilization reaction and ligand (enzyme) regeneration... 

Using this reaction fumaryl groups [24], cofactors [64] and carbohydrate derivatives [65] have been incorporated site selectively into folded four-helix bundle proteins. The reaction can also be expected to be of general use in site-selective immobilization reactions of folded proteins. 

H-Lys(Fmoc)-Pro-Gly-Lys[Z(N02)]-Glu(OtBu)-Lys(Dde)-Pro-Gly-Lys(Aloc)-Ala-OH (1.11 g, 0.60mmol) was dissolved in DMF (600mL) and the pH adjusted to 8-9 by addition of DIPEA. HATU (0.26g, 1.1 equiv) was added and the soln was stirred at rt for 3 h. The solvent was removed under high vacuum and the residue was dissolved in TFA/CH2C12 (1 1,70mL) and allowed to stand at rt for 45 min. The soln was concentrated under reduced pressure and the residue triturated with Et20. Filtration afforded crude product yield 0.94 g purity >90%. The crude product (780 mg, -75%) was dissolved in MeCN/H20 (1 1) and the pH raised to 7-8 by addition of collidine (180 pL). Solid-phase extraction (Sep-Pak Vac cartridge, C18,15 mL) and lyophilization afforded the collidine salt of the title compound (750 mg) and was directly used for the immobilization reaction. 

Immobilization by reductive amination of amine-containing biological molecules onto aldehyde-containing solid supports has been used for quite some time (Sanderson and Wilson, 1971). The reaction proceeds with excellent efficiency (Domen et al., 1990). The optimum pH for the reaction is alkaline, although good yield can be realized from pH 7—10. At high pH (9—10) the formation of the Schiff bases is more efficient and the yield of conjugation or immobilization reactions can be dramatically increased (Hornsey et al., 1986). 

Following the corona-discharge treatment of a silicone surface and the subsequent graft polymerization of AAc, type I atelocollagen was immobilized onto the grafted surface with the use of water-soluble carbodiimide [176, 177]. As depicted in Fig. 17, the immobilization reaction involves two steps, i.e., activation of carboxylic acids and the following nucleophilic substitution with prima-... 

Tab. 6.2.1. I immobilization reactions used for the preparation of DNA arrays, protein arrays, and small molecule arrays. 

Tiller, J., Berlin, P., and Klemm, D., A novel efficient enzyme-immobilization reaction on NH2 polymers by means of L-ascorbic acid. Biotechnol. Appl. Biochem. 30 (2), 155-162 (1999). 

Solovev AA, Katz E, Shuvalov VA, Erokhin YE (1991) Photoelectrochemical effects for chemically modified platinum electrodes with immobilized reaction centers for Rhodobacter sphaeroides R-26. Bioelectrochem Bioenerg 26 29-41... 

Nanoparticles have been used during the last four years to label nucleic acid sequences. Considering the size of the nanoparticles, usually 10-200 nm, labeling DNA with these is equivalent to an immobilization reaction. Indeed, usually a large number of identical probes are simultaneously grafted on a particular nanoparticle. 

Nanoparticles are therefore interesting tools for DNA chip development. Indeed, by using classical immobilization reactions, nanoparticles enable the achievement of either enhanced labeling or new detection possibilities. 

Polysaccharides. Polysaccharides possess readily accessible hydroxyl groups that may be derivatized for selective protein immobilization. We will consider the two most commonly used immobilization reactions, the triazine and the cyanogen bromide reactions. 

If cross-linking is not expected to occur, then Woodward s reagent K may be included in an enzyme solution, and a single-step immobilization reaction may be performed. 

Table 4.2 shows a summary of the selectivities of the immobilization reactions discussed in Section 4.2.1. 

The reaction between the modifier and the structural groups of surface resulting in a fixation of the modifier on a surface is referred to as immobilization reaction, Eq. (1). Transformation of already bonded groups is referred to as the surface assembly reaction, Eq. (2). Decomposition, release, hydrolysis and other transformations of already bonded groups, that is surface chemical modifications without clear participation of the modifier, are also possible, Eq. (3). Besides, the interaction between two chemically modified supports is rather possible, Eq. (4). 

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