Immobilization noncovalent attachment

Noncovalent attachment is a popular method of immobilization, and numerous different support materials have been employed, ranging from organic supports, like cellulose. 

In summary, enzyme immobilization is extremely important in the scale-up of many biocatalytic processes. The preferred method for pharmaceutical production involves covalent binding through cross-linking or attachment to a support. Noncovalent attachment is less attractive, but it is heavily utihzed owing to the commercial availabihty of industrial quantities of some enzymes immobilized using this technique. 

Call et al. (2001) of the Pacific Northwest National Laboratory in Richland, WA, also studied the immobilization of unmodified oligonucleotides. Amine-modified and unmodified oligonucleotides could be attached to epoxysilane slides (covalent attachment) or acid-washed slides (noncovalent attachment) under the same conditions by printing in an alkaline-sodium... 

The resulting noncovalently immobilized complexes have been used as ligand systems for both the Pd-catalyzed allylic amination reaction and the Rh-catalyzed hydroformylation. A glycine-urea functionalized PPh3 ligand, 4(S), was noncovalently attached to the immobilized dendritic support, and the application of this system in the Pd-catalyzed allylic amination attains similar yields and product distributions as the homogeneous analogue for the... 

Fig. 4. Immobilization methods. (A) Attachment of biomolecules onto thiol-derivatized surfaces (see Subheading 3.2.1 for experimental details). (B) Attachment of biomolecules onto amine-derivatized surfaces (Subheading 3.2.2) using amine-amine linking (upper pathway, Subheading Amine-Amine (Homobifunctional Crosslinkers) ) and amine-thiol linking (lower pathway, Subheading Amine-Thiol Crosslinking (Heterobifunctional Crosslinkers) ). (C) Noncovalent attachment of gangliosides/globosides onto hydrophobic surfaces (Subheading 3.2.3),...

Figure 2.70 Immobilization of Cso on surfaces, (a) Covalent linking to gold or to indium-tin oxide and noncovalent attachment to gold modified with coronene ( RSC 2005) ...

Immobilization The immobilization chemistry allows for covalently or noncovalently attaching small molecules or biopolymers onto a glass microscope slide. This method produces uniform spots containing equivalent amounts of samples. 

A third item to consider in using affinity chromatography is the way in which the ligand is attached to the solid support, or the immobilization method. Several techniques are available for this, including both covalent and noncovalent coupling methods [25,36]. For a protein or peptide, this generally... 

In protein microarrays, capture molecules need to be immobilized in a functional state on a solid support. In principle, the format of the assay system does not limit the choice of appropriate surface chemistry. The same immobilization procedure can be applied for both planar and bead-based systems. Proteins can be immobilized on various surfaces (Fig. 1) (12). Two-dimensional polystyrene, polylysine, aminosilane, or aldehyde, epoxy- or thiol group-coated surfaces can be used to immobilize proteins via noncovalent or covalent attachment (13,14). Three-dimensional supports like nitrocellulose or hydrogel-coated surfaces enable the immobilization of the proteins in a network structure. Larger quantities of proteins can be immobilized and kept in a functional state. Affinity binding reagents such as protein A, G, and L can be used to immobilize antibodies (15), streptavidin is used for biotinylated proteins (16), chelate for His-tagged proteins (17, 18), anti-GST antibodies for GST fusion proteins (19), and oligonucleotides for cDNA or mRNA-protein hybrids (20). 

A wide range of immobilization chemistries are commercially available in conjunction with Sepharose beads. We have investigated a limited subset of these possibilities which include direct, nonoriented immobilization via Schiff s base chemistry, oriented nonco-valent immobilization via immobilized metal affinity chromatography resins and oriented noncovalent immobilization via biotin-streptavidin binding. At present we favor direct, covalent attachment of proteins via primary amines since it is highly efficient (typically better than 85% yield), minimizes leaching and provides the best NMR results (Figure 6.2). 

In Sect. 2 of this overview, the NCN-pincer platinum(II) complex was covalently attached to hyperbranched polyglycerol by substitution of tosylate groups to obtain catalyst 4. This NCN-pincer platinum complex may also be noncovalently immobilized on polyglycerols, and the activity/selectivity of these systems in catalytic reactions has been investigated. 

The methods of attachment to the solid support can be divided into two broad categories covalent and noncovalent. Several factors should be considered. First, the ligands should be stable to immobilization, storage, and assay conditions. Second, the immobilized ligands should be accessible to the receptors, which are usually in solution. Third, the method should be efficient. 

An elegant alternative approach for noncovalent interaction relies on fluorous-lluorous interactions. A glycan array of monosaccharides and disaccharides bearing anomeric fluorous tags was noncovalently immobilized on fluorous-derivatized glass slides (19, 20). The attachment method is compatible with a wide range of functional groups and has been successfully used to probe carbohydrate-protein interactions. 

I) covalent bonding, (2) noncovalent interactions (including physical adsorption and electrostatic interactions), and (3) encapsulation. Additionally, for the first two types of immobilization procedures, interaction with the support can occur directly between the support and the molecular species or through bifunctional molecules, previously attached to the support or reacted with the metallic complex, usually termed spacers or linkers. 

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