For receptors that identify small, nonpolar molecules, molecular shape does not offer enough information for a binding site to distinguish different compounds. Other kinds of information, including chemical reactivity, must play a role. In the sense of smell, we have uncovered evidence that Schiff base formation, plays a role in olfactory detection of ketone-containing odorants. This chemistry is being explored with a number of new approaches, including Two-Step Affinity Chromatography and Accelerator Mass Spectrometry. Gas Phase Organic Chemistry Electrically charged organic molecules enjoy a vastly different environment in the gas phase than in bulk solvent.
Solvation is negligible, and counterions are absent.
Chemical reactions take place on a timescale that is much faster than the timescale for exchange of energy with the ambient heat bath. Therefore the outcome of an ionic reaction in the gas phase is not determined by the physics of collision so much as by the chemistry of the reactants. We have found out that SN2 displacements go by backside attack in the gas phase, just as they do in solution. In general we are discovering aspects of gas phase chemistry that ought to hold true for reactions in biological media as well. J. Mass Spectrom.