Unraveling the Correlated Dynamics of the Double Hydrogen Bonds of Nucleic Acid Base Pairs in Solution

Quantum mechanics/molecular mechanics hybrid simulations (CPMD/GROMOS) of nonlinear infrared spectra are performed for a modified adenine uracil base pair in CDCl3 solution. Employing a mapping between hydrogen bond distances and fundamental as well as overtone transition frequencies on the basis of on-the-fly snapshot potential energy curves, energy gap correlation functions are established. These correlation functions are utilized to determine pump probe and two-dimensional photon echo spectra. Analysis of the latter yields off-diagonal peaks signifying correlated fluctuations of the N-H center dot center dot center dot N and N-H center dot center dot center dot O hydrogen bonds.