Structural and dynamical properties of two DNA oligomers with the same base composition and different sequence

Area of Science:

• Molecular Biology
• Biophysics
• Structural Biology

Background:

• DNA sequence is crucial for biological functions.
• Understanding sequence-structure-dynamics relationships is key.
• Purine-rich DNA structures are biologically significant.

Purpose of the Study:

• To investigate how DNA base sequence affects structural and dynamical properties.
• To correlate sequence variations with measurable physical quantities.
• To explore the role of purine-rich sequences in DNA conformation.

Main Methods:

• Comparative analysis of two DNA fragments (27 bp) with identical base composition but different sequences.
• Spectroscopic methods: Circular Dichroism (CD) and UV denaturation.
• Gamma-ray footprinting for fine conformational differences.
• Fluorescence Polarization Anisotropy (FPA) for dynamical properties (hydrodynamic radius, elastic torsion constant).

Main Results:

• Gamma-ray footprinting revealed structural alterations at the nucleotide level due to sequence 'scrambling'.
• The 'scrambled' DNA sample exhibited increased thermal stability.
• The 'scrambled' DNA sample showed enhanced torsional rigidity compared to the control.
• A potential link between base-stacking interactions and torsional rigidity was observed.

Conclusions:

• DNA base sequence significantly influences its three-dimensional structure and dynamics.
• Altering purine-homopyrimidine runs affects DNA structural integrity and physical properties.
• Base-stacking interactions appear to play a role in determining DNA torsional rigidity.