Target-specific aptamers examples

The SELEX process for the selection of target-specific aptamers is a universal process characterized by the repetition of five main steps binding, partition, elution, amplification, and conditioning however, for each aptamer selection, the protocol has to be adapted to the current requirements. The SELEX design and the specific selection conditions depend, for example, on the target, the oligonucleotide hbrary, or the desired features and application of the aptamers to be selected. Therefore, a multitude of SELEX variants have been developed since the first description of this technology in 1990 (Table 2.1). 

The first example of aptamer-based target-specific chromatographic chiral separation has been reported using an antioligopeptide DNA aptamer. The enantiomers of arginine-vasopressin were separated using an inunobilized 55-base DNA aptamer (Michaud et al., 2003) known to bind the D-enantiomer of the oligopeptide stereopecifically (Williams et al., 1997). The influence of... 

Materials differ significantly with the kind of target and selection procedure. Here we list materials used for the example selection of moenomycin A-specific 2 -modified RNA aptamers (Section 7.3.6). 

Third, we have selected aptamers that can bind to the 3II isozyme of protein kinase C from an RNA pool that spanned 120 random positions [5], The aptamers fell into several families, and individuals from two of the most prominent families were assayed for their ability to inhibit the enzymatic activity ofPKC. While these aptamers efficiently inhibited the enzymatic activity of the 3II isozyme, they had a 10-fold lower K, for the 3I isozyme (96% similar) and showed no activity against the a isozyme (80% similar). These specificities rival those seen with monoclonal antibodies. We have now selected aptamers that can bind to the a isozyme ofPKC from the same RNA pool. Sequence comparisons of the anti-pil and anti-a aptamers (Fig. 13) suggest that the map that relates target space and sequence space is convoluted. For example, while one family of aptamers was returned from both selections, other families were unique for one or the other isozyme. 

Aptamer is a globular-shaped oligonucleotide that is identified by the systematic evolution of ligands by exponential enrichment (SELEX) process. It has the similar composition as natural nucleic acid, but the nucleotides of aptamer have 2 -modified sugars to enhance the nuclease resistance [122]. Since its discovery in 1990, aptamer has become a valuable research tool. Aptamers can specifically bind to target protein with high affinity, therefore it can be utilized in the targeted delivery of siRNA [37,123]. For example, prostate-specific membrane... 

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