Модификация SELEX/Aptamer

Aptamers are short single-stranded DNA or RNA oligonucleotides (< 100 nt). They gained increasing importance in drug discovery due to their inherent ability to form defined three-dimensional structures that enables them to bind to various targets (e.g. proteins) with antibody-antigen-like affinity and specificity^[1].

Aptamers with the highest binding affinity and specificity against a given target molecule are generated by an multi-step in vitro selection and enzymatic amplification process called "systematic evolution of ligands by exponential enrichment (SELEX) (for detailed information please refer to the references below^[2,3]).

The main advantages of aptamers compared to antibodies are heat stability, the lack of immunogenicity and minimal interbatch variability. Their usage in diagnostics however, is often hampered by nuclease-mediated degradation.

Enzymatic incorporation of fluoro-, amino- or O-methyl- 2'-ribose-modified nucleotides (1) by generating an initially modified combinatorial library or (2) post-SELEX markedly improve the nuclease resistance of aptamers (Tab. 1) ^[3-12]. Furthermore, a number of modified nucleotides suitable for the selection of cross-linking capable aptamers (Photo-SELEX) are available as well (Tab. 1)^[13-15].

n/a: not applicable

	Nucleotide	Modification	DNA aptamer selection (DNA SELEX)	RNA aptamer selection (RNA SELEX)
	2'F-dUTP	Substitution of 2'-OH by fluor (F)	[5]	[6,7]
	2'F-dCTP		[5]	[6,7]
	2'F-dATP		[5]	[6]
	2'F-dGTP		[5]
	2'OMe-UTP	Modification of 2'-OH by a methyl group (CH3)		[8,9,10,11]
	2'OMe-CTP			[8,9,11]
	2'OMe-ATP			[8]
	2'OMe-GTP			[8]
	2'NH2-dUTP	Substitution of 2'-OH by an amino group (NH2)		[6,12]
	2'NH2-dCTP			[12]
	2'NH2-dATP
	2'NH2-dGTP
	5Br-dUTP	Modification of C-5 by Bromine (Br)	[13]	n/a
	5I-UTP	Modification of C-5 by Iodine (I)	n/a	[14]
	4-Thio-UTP	Substitution of 4-O by Sulfur (S)	n/a	[15]

Фармацевтические исследования