SELEX systematic evolution

SELEX (systematic evolution of ligands by exponential enrichment) is used to generate aptamers, oligonucleotides selected to tightly bind a specific molecular target. The process is generally automated to allow rapid identification of one or more aptamers with the desired binding specificity. 

Aptamers are nucleic acids which exhibit a defined structure due to their nucleotide sequence and therefore, are able to specifically bind selected targets [1] (aptus [lat.] = fitting, sticking to). Aptamers and likewise, ribozymes [2] and deoxyribozymes [3] are selected in vitro by screening nucleic acid libraries. Here we describe in detail the selection of aptamers by a process called SELEX (Systematic Evolution of Ligands by Exponential enrichment) [4]. 

B.23 SELEX Systematic Evolution of Ligands by Exponential Enrichment 433... 

SELEX Systematic evolution of ligands by exponential enrichment... 

Profile Founded in 1995 with the merger of NeXagen and Vestar, the company utilizes proprietary compounds to develop therapeutics and diagnostics to serve unmet medical needs. From NeXagen, NeXstar acquired the SELEX (Systematic Evolution of Ligands by Exponential Enrichment) combinatorial chemistry technology. 

Daniels, D. A., Chen, H., Hicke, B. J., Swiderek, K. M., and Gold, L. (2003) A tenascin-c aptamer identified by tumor cell selex Systematic evolution of ligands by exponential enrichment. Proc Natl Acad Sci USA. 100, 15416-15421... 

CML chronic myeloid leukemia SELEX systematic evolution of ligands... 

The formation of aptamers rests upon a technique termed SELEX (systematic evolution of ligands by exponential enrichment). It involves the synthesis of a DNA molecule with constant sections at both ends and a randomly variable segment of nucleotides in the middle. A variable segment as short as 10 nucleotides has a combinatorial library of 4 ° or about 10 different sequences a variable sequence of 30 nucleotides generates a combinatorial library of 4 or about 10 different sequences. The DNA mixture so synthesized is then enzymatically transcribed to a combinatorial RNA library. This mixture is applied to a chromatography column in which the substance of interest (e.g., amino acid, protein, drug) is bound. RNA molecules in the combinatorial library that do not bind with the target compound are simply washed out of the column. 

Aptamers are oligonucleotides (DNA or RNA molecules) which are able to bind selectively to low-molecular-weight molecules or to macromolecules such as proteins. The interest in aptamers as ligands is related to their ease of preparation by an evolutionary selection procedure that eliminates the need for structural design of the ligand sites. Selection of the aptamers for the specific target is based on the SELEX (systematic evolution of ligands by exponential enrichment) procedure. 

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