Halogen-Bonded Guanine Base Pairs, Quartets and Ribbons

Area of Science:

• Biophysical Chemistry
• Supramolecular Chemistry
• Computational Chemistry

Background:

• Halogen bonding (XB) is a significant non-covalent interaction crucial in molecular recognition and self-assembly.
• Guanine bases form various self-assembled structures, including base pairs, ribbons, and quartets, which are fundamental in nucleic acids.
• Understanding halogen bonding in these guanine structures provides insights into their stability and function.

Purpose of the Study:

• To investigate the nature and strength of halogen bonds in different halogenated guanine DNA structures.
• To analyze how halogenation affects the structural stability and geometry of guanine assemblies.
• To explore the role of different halogens (Cl, Br, I, At) in modulating these interactions.

Main Methods:

• Computational modeling and quantum chemical calculations were employed.
• Analysis of potential energy surfaces and interaction energies.
• Geometric analysis of halogen bond parameters (distances, angles).

Main Results:

• Halogen bonding patterns (N-X•••N, N-X•••O, N-X•••X, O-X•••X, O-X•••O) vary significantly across different guanine structures (base pairs, R-I/R-II ribbons, G-quartets).
• Halogenation generally reduces structural stability, but heavier halogens (especially astatine) can increase stability in specific configurations, sometimes surpassing hydrogenated counterparts.
• Deviations from linear halogen bonds were observed, with angles around 150°, indicating complex interactions.

Conclusions:

• Halogen bonding offers a versatile tool for tuning the structural and energetic properties of guanine assemblies.
• The observed halogen bond patterns and stability trends are dependent on the specific guanine architecture and the nature of the halogen atom.
• These findings have implications for the rational design of novel DNA-based nanomaterials and drug candidates.