L-Ribonucleic acid aptamer

L-RNA aptamers, built using L-ribose, are the enantiomers of natural oligonucleotides, which are made with D-ribose. Nucleic acid aptamers, including L-RNA aptamers, contain adenosine monophosphate, guanosine monophosphate, cytidine monophosphate, uridine monophosphate, a phosphate group, a nucleobase and a ribose sugar.

Like other aptamers, L-RNA aptamers are able to bind molecules such as peptides, proteins, and substances of low molecular weight. The affinity of L-RNA aptamers to their target molecules often lies in the pico to nanomolar range and is thus comparable to antibodies.[3]

L-RNA aptamers themselves have low antigenicity. In contrast to other aptamers, L-RNA aptamers have high stability in blood serum, since they are less susceptible to be cleaved hydrolytically by enzymes.[4] They are excreted by the kidneys in a short time due to their low molar mass (which is below the renal threshold).

L-RNA aptamers modified with a higher molar mass, such as PEGylated L-RNA aptamers, show a prolonged plasma half-life.

The first step is the production of the target's enantiomer. In the case of peptides and small proteins that are produced synthetically, an enantiomer is made using synthetic D-amino acids. If the target is a larger protein molecule, beyond synthetic abilities, the enantiomer of an epitope is produced.[4]

Conventional (up to 10¹⁶ different oligonucleotides) existing molecule library serves as a starting point for the subsequent SELEX process. Selection, separation, and amplification using the mirror image of the target molecule is performed.

The sequence of the oligonucleotide selected using SELEX is determined with the help of DNA sequencing. This information is used for the synthesis of the oligonucleotide's enantiomer, the L-RNA aptamer, using L-nucleotides.