Enrichment for RNA molecules that bind a Diels-Alder transition state analog

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Biology

Background:

• RNA molecules, or ribozymes, can be engineered to bind specific targets.
• The Diels-Alder reaction is a crucial carbon-carbon bond-forming reaction in organic chemistry.
• Isolating RNA binders for non-planar or hydrophobic ligands is challenging and less explored.

Purpose of the Study:

• To isolate RNA molecules that bind a transition state analog of the Diels-Alder reaction.
• To characterize the binding affinity and specificity of the isolated RNA molecules.
• To investigate whether these RNA binders possess catalytic activity for the Diels-Alder reaction.

Main Methods:

• Affinity chromatography was used to select RNA molecules from a large library (approximately 10^14 sequences).
• Step gradient elution was employed to enrich for RNA sequences with higher binding affinities.
• Binding affinity was quantified using dissociation constant (Kd) measurements.

Main Results:

• RNA molecules with a dissociation constant (Kd) of 0.35 +/- 0.05 mM for the Diels-Alder transition state analog were successfully isolated.
• A conserved nucleotide sequence and secondary structure were identified in the selected RNA binders, which are necessary but not sufficient for binding.
• No catalytic activity for the targeted Diels-Alder reaction was detected among the isolated RNA binders.

Conclusions:

• This study demonstrates the successful isolation of RNA molecules binding a non-planar, hydrophobic ligand, specifically a transition state analog for the Diels-Alder reaction.
• The findings highlight that while specific binding can be achieved, catalytic activity is not guaranteed and may require different selection strategies.
• The absence of catalysis in these RNA binders, unlike some antibody studies, suggests alternative approaches may be needed for discovering catalytic oligonucleotides.