Streptavidin modification with

Fig. 18 LSPR spectra of each step in the surface modification of Ag nanoparticles to form a biotinylated Ag nanobiosensor and the specific binding of streptavidin. (a) Ag nanoparticles before chemical modification, 2niax = 561.4 nm. (b) Ag nanoparticles after modification with 1 mM 1 3 11-MUA/l-OT, = 598.6 nm. (c) Ag nanoparticles after modification with 1 mM biotin, max = 609.6nm. (d) Ag nanoparticles aftermodification with 100 nM streptavidin, 2 ,ax = 636.6 nm. Reproduced with permission from [38]. Copyright2002American Chemical Society...

The traditional radioimmunoassay technique could be utilized with rare earth phosphate NPs. Lin et al. reported the LuP04-apoferritin coreshell NPs synthesized in apoferritin templates. The NPs were further modified with biotin and exhibited affinity for streptavidin-modifed magnetic beads or streptavidin-modifed fluorescein isothiocyanate. Radioactive Lu was used to label the NPs (Wu et al., 2008a). 

Modification with BxNHS provides both MAb 9B9 and catalase with streptavidin-binding ability (17,20). Biotinylation at high BxNHS protein ratio,... 

Figure 27.1 Three common nucleoside triphosphate derivatives that can be incorporated into oligonucleotides by enzymatic means. The first two are biotin derivatives of pyrimidine and purine bases, respectively, that can be added to an existing DNA strand using either polymerase or terminal transferase enzymes. Modification of DNA with these nucleosides results in a probe detectable with labeled avidin or streptavidin conjugates. The third nucleoside triphosphate derivative contains an amine group that can be added to DNA using terminal transferase. The modified oligonucleotide then can be labeled with amine-reactive bioconjugation reagents to create a detectable probe.

Fig. 1. Different types of surface modification, (a) Two-dimensionai surface, e.g., poiystyrene, poiy-iysine, aminosiiane, or aidetiyde, epoxy- or thioi group-coated surface, etc. (b) Three-dimensionai surface, e.g., nitrocellulose or hydrogel-coated surface, (c) Surfaces with a special type of spacer and immobilization procedures such as PEG-epoxy, streptavidin, and N 2+ chelate, etc.

Biotin s interaction with the proteins avidin and streptavidin is among the strongest noncovalent affinities known (K l = 1015 M l). The binding occurs between the bicyclic ring of biotin and a pocket within each of the four subunits of the proteins. The valeric acid portion is not involved or required for the interaction (Green, 1975 Wilchek and Bayer, 1988). This characteristic allows modification of the valeric acid side chain without affecting the binding potential toward avidin or streptavidin. 

Modifications done with biotin-HPDP produce biotinylated compounds with long spacer arms (29.2 A), ensuring good binding efficiency with avidin or streptavidin... 

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