1. Could you explain the significance of your article to the non-specialist?

This article describes the first observation of spectroscopy for the molecules protonated acetone and its proton-bridged dimer. Proton binding to the carbonyl functional group of molecules like acetone is important in a variety of situations in Chemistry and Biology, such as the transport of protons across cell membranes. The infrared spectroscopy here reveals a snapshot of the structure for this model system, which then may provide insight into structures present in real proton-transport environments. Protonated acetone and its dimer had been seen previously in mass spectrometers, and there had been speculation about the structures of these systems, but the present measurements determine these structures.

2. What has motivated you to conduct this work?

Proton transport is ubiquitous in Chemistry and Biology, and we are studying a number of model complexes in which protons are attached to small simple molecules (water, CO2, acetylene, etc.). We want to investigate these systems with theory, and use infrared spectroscopy to test the structural predictions of theory.

3. Where do you see this work developing in the future? 

We plan to extend the work to more complex systems, including protonated amino acids and other real biological systems.

4. Are there any particular challenges facing future research in this area?

Protons are highly quantum mechanical particles, and their binding to many small molecules cannot be described by "simple" ab initio calculations. In particular, quantum theory presently has significant difficulty describing shared protons that link two small molecules (e.g., the protonated water dimer). By providing benchmark spectroscopic data, we can challenge theory to develop new approaches to handle these systems.