Mary T. Rodgers

Mary T. Rodgers

Mary T. Rodgers

Research Interest/Area of Expertise

  • Mass Spectrometry; Infrared Spectroscopy; Structure and Thermochemistry via Ion-Molecule Reactions, Collision-Induced Dissociation, and Theoretical Calculations.

Research

 Research in the Rodgers group is interdisciplinary in nature, making use of state-of-the-art physical and analytical techniques to study research problems that span all five disciplines of chemistry (i.e., analytical, biochemistry, inorganic, organic, and physical). However, most of the research projects we pursue are of either biological or inorganic relevance and involve the use of model systems. Our research efforts are generally aimed at achieving a better understanding of the interplay between structure and function in biological systems, or structure and intrinsic reactivity in inorganic systems. To this end, we make use of a variety of tandem mass spectrometry (MS/MS) approaches, often enhanced and supported by synergistic theoretical electronic structure calculations, in our research studies.

The primary tools of our research are tandem mass spectrometers (MS/MS) and computers. We currently have three MS/MS instruments available in our experimental arsenal. We also have three high performance liquid chromatographs (HPLC) that can be used independently or in combination with our commercial MS/MS instruments. A variety of supporting tools and instrumentation are also available including: (1) small analytical instruments for sample cleanup and preparation, (2) infrared lasers for complementary photodissociation or spectroscopic studies, (3) software packages for data analysis, and instrument design and control, (4) test and measurement electronics for diagnostics and control, and (5) mechanical tools and hardware. Our research sometimes involves instrument development and modification projects to enable improved MS/MS analyses. We collaborate extensively and thus make use of other MS and laser instrumentation available in the laboratories of our collaborators. Our computational efforts are primarily supported by the Wayne State University High Performance Grid and supplemented by PCs and workstations available in our laboratory. We make extensive use of two commercial computational chemistry software packages to perform relevant electronic structure theory calculations: (1) the Gaussian suite of programs and (2) Hyperchem professional.

Our first MS/MS instrument is a custom-built guided ion beam tandem mass spectrometer of the BOQ geometry (magnetic sector (B) - octopole ion guide (O) - quadrupole mass filter (Q)). This instrument is designed to allow the kinetic-energy dependence of ion-molecule reactions (IMR) or collision-induced dissociation (CID) processes to be examined from thermal to hyperthermal energies. Measured reactant and product intensities are converted to absolute IMR or CID cross sections using Beer’s law. Cross sections are analyzed to extract accurate thermochemical data (i.e., bond dissociation energies (BDEs), activation energies (AEs), heats of reaction (ï„Hrxns). These measurements are supported by complementary theoretical calculations to provide molecule parameters needed for the analysis of experimental data and theoretical estimates for the quantities measured.

Our next MS/MS instrument is a Bruker 7T Solarix Hybrid FTMS (Q-FT-ICR MS). This instrument is our flagship mass spectrometer capable of very high mass accuracy and mass resolution measurements. It is equipped with a variety of ionization sources including: (1) electrospray ionization (ESI) and nano-ESI, (2) matrix assisted laser desorption ionization (MALDI), and (3) chemical ionization (CI and n-CI). It is also equipped with a variety of activation methods including: CID (in-source, Q-CID, SORI-CID), ion-ion reactions (ETD and PTR), ion-electron reactions (ECD and EDD), and photodissociation (IRMPD). It can also be used to perform MS imaging of biological tissues and analytically prepared surfaces in combination with the MALDI source. As a trapping mass spectrometer, it can also be used to make kinetic (e.g., IMR and H/D exchange), equilibrium (e.g., acid-base, ligand exchange, and clustering reactions), and spectroscopic (in combination with tunable lasers) measurements under well-controlled conditions.

Our third MS/MS instrument is a Bruker amaZon ETD quadrupole ion trap mass spectrometer (QITMS). This instrument possesses several of the same capabilities as our FT-ICR MS, but is not capable of nearly as high of mass accuracy or mass resolution measurements. It is equipped with two ionization sources including: (1) ESI and (2) CI and n-CI). It is also equipped with a variety of activation methods including: (1) CID (in-source and multiple collision-CID), (3) ETD and PTR, and (4) IRMPD. Like the FT-ICR MS it is also a trapping MS, and thus can also be used to make kinetic (e.g., IMR and H/D exchange), equilibrium (e.g., acid-base, ligand exchange, and clustering reactions), and spectroscopic (in combination with tunable lasers) measurements, but under somewhat less well controlled conditions than in the FT-ICR MS.

Biomolecule Structure and Stability. Current research projects involve the study of the influence of the local environment (probed via deprotonation, protonation and noncovalent interactions with metal cations or binding of ligand and drug molecules) on the structures and stabilities of biologically relevant systems including: nucleic acids and their component building blocks (nucleobases, nucleosides and phosphate esters and including modifications), proteins and their component building blocks (peptides, amino acids, and post-translational modifications). The mechanisms, energetics and control of fundamental dissociation processes that occur in these systems and the effects of solvation on these systems are also of interest. These studies may lead to a better understanding of various metabolic pathways, provide information to help improve both solution and gas-phase sequencing techniques, and facilitate the development of new drug candidates.

Molecular Recognition. Current research projects involve the study of the factors that lead to strong and selective binding of cations, anions, various types of ligands as well as base-pairing interactions. Structure, size, charge, and the nature and number of donor-acceptor interactions all play a role in determining selectivity and thus are examined. In particular, interactions with macrocyclic ligands and those that lead to noncanonical structures in biological systems are of interest. These studies may help improve characterization, separations, and drug delivery applications.

Solvation. Partially solvated systems are also being studied to enhance our understanding of the effect of solvation on biochemical processes, to provide insight into folding and conformational stability of biological macromolecules, the energetics of solvation, and structural information on the solvated complex. This work also connects the gas-phase tandem MS/MS studies to those performed in condensed-phase environments.

Theoretical Calculations. Theoretical calculations are performed to support and enhance our experimental work and used to obtain model structures and energetics for the species and processes under investigation, to provide insight into the reaction or dissociation mechanisms, and to provide the molecular parameters and IR spectra needed for data analysis. 

 

Education – Degrees, Licenses, Certifications

  • B.S. Illinois State University 1985
  • Ph.D. California Institute of Technology 1992
  • Postdoctoral, California Institute of Technology 1992-94
  • Postdoctoral, University of Utah 1994-97

Selected Publications

 "Base-Pairing Energies of Protonated Nucleobase Pairs and Proton Affinities of 1-Methylated Cytosines: Model Systems for the Effects of the Sugar Moiety on the Stability of DNA i-Motif Conformation", B. Yang, A. A. Moehlig, C. E. Frieler, M. T. Rodgers, J. Phys. Chem. B 119, 1857-1868 (2015). doi:10.1021/acs.jcpb.5b00035

"Gas-Phase Conformations and Energetics of Protonated 2'-Deoxyadenosine and Adenosine: IRMPD Action Spectroscopy and Theoretical Studies", R.R. Wu, B. Yang, G. Berden, J. Oomens, and M.T. RodgersJ. Phys. Chem. B 119, 2795-2805 (2015). doi:10.1021/jp509267k

"Guided Ion Beam and Computational Studies of the Decomposition of a Model Thiourea Protein Cross-Linker", R. Wang, B. Yang, R. R. Wu, M. T. Rodgers, M. Schäfer, and P. B. Armentrout, J. Phys. Chem. B 119, 3727-3742 (2015). doi: 10.1021/jp512997z

"Intrinsic Affinities of Alkali Metal Cations for Diaza-18-Crown-6: Effects of Alkali Metal Cation Size and Donor Atoms on the Structure and Binding Energies", C.A. Austin, M.T. RodgersInt. J. Mass Spectrom. 377, 65-72 (2015). History of Mass Spectrometry Special Issue. doi:10.1016/j.ijms.2014.06.033

"Infrared Multiple Photon Dissociation Action Spectroscopy of Sodium Cationized Halouracils: Effects of Halogenation on Gas-Phase Conformation", C.M. Kaczan, A.I. Rathur, R.R. Wu, Y. Chen, C.A. Austin, G. Berden, J. Oomens, M.T. RodgersJ. Am. Soc. Mass Spectrom. 378, 76-85 (2015). Veronica M. Bierbaum Honor Issue. doi:10.1016/j.ijms.2014.07.016

"Base-Pairing Energies of Protonated Nucleoside Base Pairs of dCyd and m5dCyd: Implications for the Stability of DNA i-Motif Conformations", B. Yang, M.T. RodgersJ. Am. Soc. Mass Spectrom. 26, 1394-1403 (2015). doi:10.1007/s13361-015-1144-8

 

Currently Teaching

  • CHM5160 Instrumental Analytical Chemistry, 3 credit hours F2017

Courses taught

CHM 4850/8850   Frontiers in Chemistry, 1 credit hours   W2016
CHM 7180   Mass Spectrometry, 3 credit hours   W2016
CHM 8830   Seminar in Physical Chemistry, 1 credit hours   W2016
CHM 5160   Instrumental Analytical Chemistry, 3 credit hours   F2016
CHM 8800   Seminar in Analytical Chemistry, 1 credit hours   F2016
CHM 8830   Seminar in Physical Chemistry, ` credit hours   F2016
 

CHM7180 Mass Spectrometry, 3 credit hours W2017
CHM8800 Seminar in Analytical Chemistry, 1 credit hour W2017
CHM8830 Seminar in Physical Chemistry, 1 credit hour W201