Dear Eyal,
Thank you for your interest in TriLink’s Aptamer Libraries. The complexity of the final library varies with the random region length. Libraries with longer random regions have more unique sequence motifs than libraries with shorter random regions. However, not all possible unique sequences can be represented in each selection. In contrast, libraries with shorter random regions will give you a better representation of all possible sequences but are inherently less complex than a library with a longer randomer region. However, once an aptamer is selected shorter aptamers are easier and less expensive to synthesize

Aptamers have been designed to bind to specific amino acids.Geiger et. al. found an aptamer that distinguished with a 12,000-fold improvement between L-arginine and D-arginine. I don’t know the specific discrimination between Proline and Glycine. It would need to be determined experimentally. Proline and Glycine have different structures but the location within the protein and the protein folding may affect the ability to find an appropriate aptamer.

Good luck with your experiments.

Best regards,
Sabrina Shore, MS