Streptavidin conjugation

Oligonucleotide-Directed Assembly Using DNA-Streptavidin Conjugates... 

Streptavidin-single-stranded DNA covalent conjugates were described as the building blocks for assembling nanostructured scaffolds [31], The amount and type of biotinylated ligands were used to modulate the affinity of duplex formation between solid-phase-bound nucleic acid templates and DNA-streptavidin conjugates. This system has been proposed for the design of fine-tuned sequence detection systems. 

NHS-LC-biotin can be used to add a biotin tag to monoclonal antibodies directed at certain tumor antigens. The biotinylated monoclonals are allowed to bind to the tumor cell surfaces in vivo, and subsequent administration of an avidin or streptavidin conjugate can form the basis for inducing cytotoxic effects or creating traceable complexes for use in imaging techniques (Hnatowich et al., 1987). 

Block nonspecific sites on the membrane with an appropriate blocking component (such as BSA) and detect the biotinylated proteins using an avidin or streptavidin conjugate. 

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.

Make it visible the fluorophore label can be visualized directly using fluorescent microscopy. The biotin label (see Sect. 6.2.1) can be detected using streptavidin conjugated with an enzyme the latter must be visualized through an enzyme chromogenic system. Incubate sections with an appropriate enzyme substrate until optimal color develops (see Sect. 2.3). 

A very interesting approach was presented recently by Niemeyer et al. [113]. They prepared covalent DNA-streptavidin conjugates to which biotinylated alkaline phosphatase, beta-galactosidase, and horseradish peroxidase, as well as biotinylated anti-mouse and anti-rabbit immunoglobulins, were coupled. Immobilization of DNA-streptavidin conjugates was performed by hybridization with the complementary oligonucleotides, bound to the surface. It was demonstrated... 

Assay for human immunodeficiency virus type 1 (HIV-1) proviral DNA in peripheral blood monuclear cells can be performed by PCR followed by detection of PCR products by electrochemiluminescence-labeled oligonucleotide probe [Tris-bipyridine ruthenium (II) complex]. Since one of the PCR primers is biotin-labeled at the 5 end, facile capture of the PCR product-probe complex can be accomplished on streptavidin-conjugated magnetic particles, prior to analysis in an electrochemiluminescence analyzer (S3). 

A disposable electrochemical enzyme-amplified genosensor was described for specific detection of Salmonella (Del Giallo et al., 2005). A DNA probe specific for Salmonella was immobilized onto screen-printed carbon electrodes and allowed to hybridize with a biotinylated PCR-amplified product of Salmonella. The hybridization reaction was detected using streptavidin conjugated-AP where the enzyme catalyzed the conversion of electroinactive a-naphthyl phosphate to electroactive a-naphthol, which was detected by differential pulse voltammetry. 

Kam et al. [32] Purified and shortened SW CNT -1- streptavidin SW CNT-streptavidin conjugate caused extensive cell death, which was attributed to the delivery of streptavidin to the cells (proleukemia cells of human and T-lymphocytes)... 

Streptavidin-gold conj ugate. streptavidin conjugated to 1.0-nm gold particles... 

The following sections discuss the main techniques used to make avidin (or streptavidin) conjugates and various biotinylated components. Chapter 8, Section 3, should be consulted for a complete overview of the biotinylation reagents currently available. 

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