DNA sequence selectivity of hairpin polyamide turn units

Area of Science:

• Molecular Biology
• Organic Chemistry
• Biochemistry

Background:

• Hairpin polyamides are molecules that can bind to DNA.
• The turn unit in these polyamides is crucial for DNA binding specificity.
• Previous analogs used alpha-amino-gamma-turns, but beta-amino-gamma-turns were explored for improved binding.

Purpose of the Study:

• To investigate the DNA sequence preferences of hairpin polyamides containing beta-amino-gamma-turns.
• To compare the binding affinities and specificities of beta-amino-gamma-turns with modified alpha-amino-gamma-turns.
• To establish a foundation for using turn subunits as DNA minor groove recognition elements.

Main Methods:

• Synthesis of six-ring polyamides incorporating beta-amino-gamma-turns.
• Quantitative footprinting titrations to assess DNA binding affinities and sequence preferences.
• Synthesis and comparative analysis of fluorine and hydroxyl substituted alpha-amino-gamma-turns.

Main Results:

• Polyamides with beta-amino-gamma-turns exhibited improved binding affinities compared to alpha-amino-gamma-turn analogs for specific DNA sequences.
• An energetic penalty was observed for G.C and C.G base pairs at the beta-amino-gamma-turn position.
• Little sequence preference was found for T.A over A.T base pairs at the beta-amino-gamma-turn position.
• Modified alpha-amino-gamma-turns showed diminished overall affinity and no enhanced specificity.

Conclusions:

• Beta-amino-gamma-turns represent a promising structural modification for enhancing polyamide-DNA binding affinity.
• The turn subunit's sequence preference is limited, particularly for T.A/A.T base pairs.
• This research provides a baseline for future development of polyamides targeting the DNA minor groove.