A Kinetic Approach to Double Proton Transfer in Watson-Crick DNA Base Pairs

Area of Science:

• Biophysics
• Computational Chemistry
• Molecular Biology

Background:

• Double proton transfer (DPT) in DNA base pairs generates tautomeric forms.
• These tautomers, such as G*C* and A*T*, are implicated in genetic mutations.

Purpose of the Study:

• To investigate the intrinsic reaction coordinates for DPT in GC and AT base pairs.
• To calculate the probabilities of forming tautomeric forms (G*C* and A*T*).
• To determine the infrared absorption intensities of GC and G*C*.

Main Methods:

• Density functional theory (DFT) calculations.
• Eyring's chemical kinetics.
• Analysis of intrinsic reaction coordinates and vibrational modes.

Main Results:

• Probabilities of GC to G*C* change were 3 × 10^-8; AT to A*T* change were 2 × 10^-10.
• These probabilities align with known mutation rates.
• G*C* tautomers show distinct vibrational modes near 3000 cm^-1, unlike standard GC pairs.

Conclusions:

• The calculated probabilities of DPT are consistent with observed mutation rates, suggesting DPT as a potential source of mutations.
• Infrared spectroscopy can identify G*C* tautomers through unique vibrational signatures around 3000 cm^-1.