High fidelity base pairing at the 3'-terminus.

Area of Science:

• Biochemistry
• Molecular Biology
• Nucleic Acid Chemistry

Background:

• Achieving single-base selectivity at the 3 -terminus of nucleic acid probes is challenging.
• Natural systems utilize mechanisms like wobble base pairs to tolerate terminal variations.
• Short RNA strands play crucial regulatory roles, necessitating high-fidelity binding methods.

Purpose of the Study:

• To develop a receptor-like approach for high-fidelity binding at the 3 -terminus of probes.
• To investigate the structural basis and binding characteristics of a novel 3 -terminal modification.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy to determine three-dimensional structure.
• Restrained molecular dynamics simulations.
• UV melting point analysis (DeltaT(m)) to assess binding affinity and selectivity.

Main Results:

• A DNA duplex with a 3 -terminal 2 -anthraquinoylamido-2 -deoxyuridine (Uaq) residue was structurally characterized.
• The Uaq residue binds via pi-stacking, hydrogen bonding, and minor groove interactions.
• Uaq significantly enhances binding affinity for RNA targets (up to +18.2 °C DeltaT(m)) and improves base-pairing selectivity, with large destabilization for mismatches (up to -29.5 °C DeltaDeltaT(m)).

Conclusions:

• The Uaq motif represents a highly effective molecular cap for 3 -termini.
• This modification facilitates routine incorporation into automated nucleic acid synthesis.
• The Uaq cap offers a powerful tool for improving the fidelity of nucleic acid hybridization assays.