In this award funded by the Chemical Structure, Dynamics and Mechanisms Program of the Division of Chemistry, Professor Mark A. Johnson of Yale University will continue his integration of vibrational spectroscopy with cryogenic mass spectrometry to create a new, generally applicable structural probe for chemical analysis with dramatically enhanced resolution and sensitivity. This development exploits very recent technological advances that allow increasingly complex species to be extracted from solution, frozen into well-defined structures near 10 K, mass-selected, and then characterized with vibrational, electronic and (in the case of anions) photoelectron spectroscopies. The most important aspect of these gas-phase studies is that, because species are quenched into configurations with minimal thermal fluctuations, much sharper band patterns are recovered than are observed in condensed media. Johnson's program will extend and expand the utility of cryogenic vibrational spectroscopy to elucidate the particular H-bond donor-acceptor pairs of folded structures of biopolymers as well as those at play in non-covalently bonded host-guest complexes. Special emphasis will be placed on identifying scenarios which yield highly selective docking of substrate molecules to biomimetic peptide catalysts. An important aspect of the study will be to elucidate the relationship between the conformations obtained in the gas phase and those found in solution, which will be accomplished by following the dependence of ion structure on the number of solvent molecules retained in the gas-phase cluster. Because these measurements are carried out using methods specifically built for this application, his program dedicates significant effort toward refinement of the experimental approach, including temperature control and micro-solvation of the isolated species.
Johnson's program directly interfaces physical chemistry students with immediate challenges addressed by synthetic colleagues, and thus prepares a new generation of scientists with a versatile skill set, well centered in the chemical sciences. His program contributes to the strong foundation of an emerging branch of chemical analysis where complex systems are subjected to structural characterization in the ansatz of a supermolecule. The generality of the approach is ideally suited to engage young researchers and established colleagues alike, with exciting and powerful new ways to explore chemical structure.
