DNA is stabilized by two noncovalent interactions: base stacking via pi-pi interaction, and base pairing via hydrogen bonding. The presence of these two interactions affects the excited state dynamics. Base stacking has been mainly studied in solution, and found to have a relaxation mechanism dominated by delocalized exciton formation and recombination. Meanwhile, base pairing has been studied in the gas phase and observed to decay via proton transfer. This bifurcation is due to the relative stabilities of these interactions in different media. Therefore, base stacking has been little studied in the gas phase. We want to observe the exciton decay of stacked bases in the gas phase, free from solvent, to help understand the role of solvent in the relaxation pathway.

Because we are unable to study ions, and therefore DNA with its charged phosphate backbone, we have developed a neutral DNA analogue, peptide nucleic acids (PNA). PNA will form stacked bases due to pi-pi interaction in the gas phase, similar to DNA. This will allow us to study the excitonic behavior of excited stacked bases in the gas phase, free from solvent, assuming excitons will form without solvent present. This research is supported by the synthetic efforts of Prof. Amelia Fuller at Santa Clara University and structure calculations done by Prof. Glake Hill at Jackson State University.