Single conformation spectroscopy and dynamics of multichromophore networks

Purdue University, West Lafayette IN

Investigators

Abstract

With this award, the Chemical Structure, Dynamics and Mechanisms (CSDM-A) Program of the Division of Chemistry is funding Professor Timothy Zwier of Purdue University and his collaborators to investigate the subtle intermolecular interactions that influence the ways in which large molecules fold up on themselves. Using sophisticated techniques to get these molecules into the gas phase, combined with exquisitely-sensitive spectroscopic methods, Professor Zwier and his group are doing experiments that will unravel the delicate forces that hold single conformations of these molecules in their specific geometries. Molecules to be studied include peptides as well as molecules that may find use in electronic materials. The knowledge obtained from these studies will provide theoretical and computational chemists with benchmarks for testing the ability of new computational methods to accurately predict the subtle intermolecular forces that give rise to particular conformations. A unique element in this project is the collaboration with a number of synthetic and theoretical chemists as well as with faculty and students at primarily undergraduate institutions in the Midwest. Professor Zwier and his research group make low-temperature samples of neutral and charged forms of large, conformationally-flexible molecules in the gas-phase using a variety of methods including laser-desorption (neutrals) and electro-spray ionization (ions). The species' spectra are interrogated using a variety of laser spectroscopic methods that are capable of separating the spectra of individual conformers. Specific species that are being examined include: peptides that form helices, peptides that form parallel and anti-parallel beta-sheets, glutamine- or asparagine-rich peptides that are involved in the formation of tangled networks, and specific hexapeptides that are believed to play a role in the formation of amyloid fibrils. In addition to the peptides, Zwier and his group are studying the spectra of isolated cycloparaphenylenes (nano-hoops) that are predicted to have interesting vibronic coupling. The Zwier research group is collaborating with a wide variety of researchers from synthetic chemists to theoretical and computational chemists. The impact of this research is significantly broadened through the collaboration with a number of faculty and undergraduate students from small liberal arts colleges, including Hope College, Kalamazoo College and the University of Wisconsin - Eau Claire.