Thermochemistry of Metal-Ligand Bonds and Protonated Peptides

University Of Utah, Salt Lake City UT

Investigators

Abstract

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) program in the Division of Chemistry, Professor Peter B. Armentrout and his group at the University of Utah will use a guided ion beam tandem mass spectrometer coupled with electrospray, flow tube, and ion mobility sources to study gas-phase organometallic and biological ion chemistry. These studies will seek to examine the complex challenges associated with quantifying the chemistry of excited electronic states of transition metal cations and determining absolute energies differences between specific conformations of biomolecular ions. Professor Armentrout and his students will investigate angular momentum effects in collision-induced dissociation experiments, state-specific chemistry of transition metal (TM) ions, energetics for decomposition of protonated peptides along with their structures, as well as species formed by transition metal activation of C-H bonds involving methane and larger hydrocarbons. Their studies could lead to better understandings of spin-orbit coupling effects in reactions of transition metal ions, peptide degradation processes especially for conformation-specific energetics, and industrially important C-H bond activation and C-C coupling processes. In addition to these broader impacts in science, the work performed will also further the education of an informed science, technology, engineering, and mathematics (STEM) workforce, including both graduate and undergraduate students. Under this award, the Armentrout group at the University of Utah will examine several interrelated areas; a recently developed IM source will be enhanced by the addition of novel ion sources and a compact SLIM (structures for lossless ion manipulation) device for enhanced resolution. The IM source will be used to study state-specific chemistry of TM ions and the energetics for decomposition of conformer-specific protonated peptides. The latter processes are important in understanding analytical applications for protein sequence identification and will experimentally establish the true ground conformer for the first time. Systems of focus will include those containing asparagine, where deamidation is believed to be a major molecular process contributing to aging and the onset of neurodegenerative diseases. Infrared action spectroscopy will be used to determine structures of biological systems as well as to probe structures of species formed by CH bond activation and CC coupling reactions of TM cations with hydrocarbons. All areas of study will be complemented by theoretical calculations. Potentially transformative studies include quantitative characterization of spin-orbit coupling effects, absolute measurements of energy differences between conformations, and methane activation processes. In all these endeavors, the studies will provide thermodynamic data and educate future scientists. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.