Immobilization covalent attachment

Keywords DNA chip Microarrays Immobilization Covalent attachment Linker Solid supports Hybridization Detection... 

In most cases, the proteia is immobilized onto y-aminopropyl sUica and covalently attached usiag a cross-linking reagent such as -carbonyl diimidazole. The tertiary stmcture or three dimensional organization of proteias are thought to be important for their activity and chiral recognition. Therefore, mobile phase conditions that cause proteia "deaaturatioa" or loss of tertiary stmcture must be avoided. 

Si-C formation technique with hydrogen-terminated silicon substrates can also be used as the covalent attachment of nanomaterials onto silicon surface. The possibility of assembling nanomaterials in order is strongly desired in order to enable efficient utilization of their unique nano-sized properties. Ordered arranging and position controlling of nanomaterials on solid substrates especially on silicon surface have been intensively studied [10]. In this manuscript, the nanoparticle immobilization by thermal Si-C formation will be discussed [11]. 

Rasor and Tischer (1998) have brought out the advantages of enzyme immobilization. Examples of penicillin-G to 6-APA, hydrolysis of cephalospwrin C into 7-ACA, hydrolysis of isosorbide diacetate and hydrolysis of 5-(4-hydroxy phenyl) hydantom are cited. De Vroom (1998) has reported covalent attachment of penicillin acylase (EC 3.51.11) from E.Coli in a gelatine-based carrier to give a water insoluble catalyst assemblase which can be recycled many times, and is suitable for the production of semi-synthetic antibiotics in an aqueous environment. The enzyme can be applied both in a hydrolytic fashion and a synthetic fashion. 6-APA was produced from penicillin-G similarly, 7-ADCA was produced from desa acetoxycephalosporin G, a ring expansion product of penicillin G. 

A very promising method, immobilized artificial membrane (IAM) chromatography, was developed by Pidgeon and co-workers [299-304,307], where silica resin was modified by covalent attachment of phospholipid-like groups to the surface. The retention parameters mimic the partitioning of drugs into phospholipid bilayers. The topic has been widely reviewed [47,298,307,309-311]. 

Run/Nin heteronuclear complexes such as (653), in which a photosensitizer [Ru(bpy)3]2+ or [Ru(phen)3]2+ is covalently attached to the Ni1 cyclam complex, have been synthesized in order to improve the efficiency of electron transfer from the photoexcited photosensitizer to the catalytic site.1 44-1646 However, these complexes did not perform particularly well, either due to unfavorable configuration of the Nin-cyclam subunit and the resulting steric hindrance or due to short lifetime of the excited states of the Ru photosensitizer moieties. A stable catalytic system has been prepared by immobilizing macrocyclic Ni11 complexes and [Ru(bipy)3]2+ in a nafion membrane.164... 

Size-related problems may become important for all microsensors. Leakage of sensing materials from a small membrane may lead to rapid deterioration of sensor properties [104], While the lipophilicity of membrane components cannot be increased infinitely, immobilization of ionophore and ion exchanger in the polymer by covalent attachment or molecular imprinting along with utilization of plasticizer-free membranes could help solve the leakage problem. 

Many enzymes require the participation of dissociable coenzymes such as NAD+, NADP+ or ATP for their catalytic activities. The use of coenzymes to activate immobilized enzymes on a large scale is hampered by their relatively low stability and high cost. Attempts are therefore being made to stabilize the coenzymes and to find suitable means for their continuous regeneration. The principal approach has been to covalently attach a co-enzyme to a polymeric water-soluble matrix, thus making the co-enzyme, like the enzyme, potentially reusable (9,10). 

Figure 16.2 Three different approaches used by Crooks et at. to immobilize PAMAM dendrimers on Au surfaces (A) Direct attachment, using amine-Au interactions [39-41 ] (B) covalent attachment on a SAM prepared from alkylthiols using multiple interactions [42] (C) covalent attachment on a SAM prepared from alkylthiols using only one or a few connections [43]...

---