FT-Raman and QM/MM study of the interaction between histamine and DNA

The interaction between histamine and highly polymerized calf-thymus DNA has been investigated using FT-Raman spectroscopy and the hybrid QM/MM (quantum mechanics/molecular mechanics) methodology. Raman spectra of solutions containing histamine and calf-thymus DNA, at different molar ratios, were recorded. Solutions were prepared at physiological settings of pH and ionic strength, using both natural and heavy water as the solvent. The analysis of the spectral changes on the DNA Raman spectra when adding different concentrations of histamine allowed us to identify the reactive sites of DNA and histamine, which were used to built two minor groove and one intercalated binding models. They were further used as starting points of the QM/MM theoretical study. However, minimal energy points were only reached for the two minor groove models. For each optimized structure, we calculated analytical force constants of histamine molecule in order to perform the vibrational dynamics. Normal mode descriptions allowed us to compare calculated wavenumbers for DNA-interacting histamine to those measured in the Raman spectra of DNA-histamine solutions.