Thermochemistry of Noncovalent Interactions and Metal-Ligand Bonds of Biological Relevance

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In this project funded by the Chemical Structure, Dynamics and Mechanisms-A (CSDM-A) Program in the Division of Chemistry, Professor Mary T. Rodgers of Wayne State University is using mass spectrometry techniques to obtain information about the weak interactions that hold two or more molecules together without the formation of a strong "covalent" bond. Covalent bonds involve the actual sharing of electrons between the two molecules. "Non-covalent" interactions are generally weaker than covalent bonds. They play roles such things as the boiling point of liquids and the ability of insects to stick to walls. Professor Rodgers' research focuses on non-covalent interactions relevant to living systems, for example metal atom binding with nucleic molecules (these are constituents of DNA) and the binding of peptide molecules (constituents of proteins). The results of this research may advance our understanding of the chemical basis for biological processes and aid in the design of new technologies for sensing biologically relevant molecules. Graduate and undergraduate students involved in this project are gaining valuable experience in a multidisciplinary research environment encompassing chemistry, biochemistry, chemical physics and mass spectrometry. The resulting thermochemical data are being compiled and made available to the community via a web-based thermochemical database, the National Institutes of Standards and Technology (NIST) Chemistry Webbook and the CRC Handbook of Chemistry and Physics.In this work, experimental measurements and theoretical calculations are synergistically combined to elucidate quantitative thermochemical data and dynamical and structural information regarding noncovalent interactions and metal-ligand bonds of biological relevance. Guided ion beam tandem mass spectrometry (GIBMS) experiments are employed to probe the energy-resolved collision-induced dissociation (CID) behavior of the species of interest. Electronic structure calculations characterize the structures and energetics of the species of interest and their CID pathways. Thermochemical analysis of the experimental data are yielding energetic and structural information on the noncovalent interactions or metal-ligand bonds that are cleaved upon CID and on the mechanisms and energetic barrier(s) for the observed activated dissociation pathways. Continued development of the custom-built GIBMS instrument and associated data analysis procedures is an expected outcome of this work that may enable future studies on increasingly complex systems.