Solution structure of a DNA duplex containing a biphenyl pair.

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• DNA and RNA double helices are stabilized by noncovalent interactions, primarily hydrogen bonding and base stacking.
• Previous research demonstrated that biphenyl pairs, incapable of hydrogen bonding, can be incorporated into DNA without compromising duplex stability.

Purpose of the Study:

• To investigate the structural and dynamic properties of DNA containing biphenyl nucleoside analogs.
• To elucidate the role of interstrand stacking interactions of biphenyl residues in maintaining DNA duplex stability.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was used to determine the solution structure of a modified DNA decamer duplex.
• Structural analysis focused on the intercalation and stacking of biphenyl units within the DNA helix.

Main Results:

• The NMR structure revealed a B-DNA duplex with a slight kink at the modified site.
• Biphenyl groups were found to be intercalated side-by-side and stacked head-to-tail, forming van der Waals contacts.
• Intrastrand stacking of biphenyl units with adjacent natural bases influenced intercalation geometry.
• The DNA helix exhibited widened pitch and reduced twist at the modification site.
• Biphenyl rings displayed dynamic motion within the duplex even at room temperature.

Conclusions:

• Interstrand stacking interactions of biphenyl pairs can effectively stabilize DNA duplexes, independent of hydrogen bonding.
• The structural and dynamic behavior of these modified nucleosides provides insights into DNA structural plasticity.
• This work expands the understanding of noncovalent interactions in nucleic acid structure and stability.