Assistant Professor – Inorganic, Bioinorganic & Physical Inorganic Chemistry
Research and/or Creative Works
Research in the Liptak group seeks to advance fundamental understanding of the relationships between electronic structure and function. One exciting research area from this viewpoint is the biochemical function of transition metals, where small structural changes can introduce dramatic functional changes due to the accessibility of several electronic states at ambient temperatures. Another interesting research area is the photophysics of conjugated organic molecules, whose fluorescent properties are determined by the excited state electronic structure.
Students in the Liptak group have the opportunity to learn a wide range of air-sensitive and biochemical techniques. In addition, students regularly employ a variety of spectroscopic techniques, including: absorption, fluorescence, circular dichroism, magnetic circular dichroism, electron paramagnetic resonance, and nuclear magnetic resonance. Finally, much of our data analysis relies upon electronic structure calculations, which are validated by comparison to experiment and then used to provide deep insight into the electronic structure and function of systems under investigation.
One active project in the Liptak group aims to understand how non-canonical heme oxygenases catalyze the formation of novel mycobilin and staphylobilin products despite the fact that heme iron has the same first coordination sphere as in canonical heme oxygenases, peroxidases, and hemoglobin. In order to understand how second-sphere interactions in the enzyme active sites tune the electronic structure and reactivity of His-ligated heme, we employ site-directed mutagenesis in conjunction with functional and spectroscopic characterization. Results from our laboratory strongly suggest that the novel reactivity arises from a complex electronic structure change induced by the coordinated influences of several second-sphere amino acids.
A second research project in the Liptak group seeks to elucidate the origins of catalytic hydrogen evolution by cobalt and nickel tetrapyrroles. Researchers in the Liptak group biosynthesize novel monomeric and dimeric cobalt and nickel tetrapyrroles, and characterize their electronic and functional properties. To further understand the origins of Co(I) nucleophilicity, we are developing 59Co nuclear magnetic resonance spectroscopy as a probe of diamagnetic cobalt electronic structure in solution.
A third project in the Liptak group strives to advance fundamental understanding of the remarkable photophysical properties of hydrazone-based materials. Students in the Liptak group employ a range of optical spectroscopies and quantum mechanical calculations to both understand and predict the fluorescent properties of these materials. In many cases, we have found that simple substituent changes dramatically alter the photophysics of these dyes!
Lockhart, C.L.; Conger, M.A.; Pittman, D.S.; Liptak, M.D. “Hydrogen bond donation to the heme distal ligand of Staphylococcus aureus IsdG tunes the electronic structure” J. Biol. Inorg. Chem. 2015, 20, 757-770.
Graves, A.B.; Morse, R.P.; Chao, A.; Iniguez, A.; Goulding, C.W.; Liptak, M.D. “Crystallographic and Spectroscopic Insights into Heme Degradation by Mycobacterium tuberculosis MhuD” Inorg. Chem. 2014, 53, 5931-5940.
Owens, C.P.; Chim, N.; Graves, A.B.; Harmston, C.A.; Contreras, H.; Iniguez, A.; Liptak, M.D.; Goulding, C.W. “The Mycobacterium tuberculosis Secreted Protein, Rv0203, Transfers Heme to Membrane Proteins, Mycobacterial membrane protein Large 3 (MmpL3) and MmpL11” J. Biol. Chem. 2013, 288, 21714-21728.
Su, X.; Liptak, M.D.; Aprahamian, I. “Water-soluble Triazolopyridiniums as Tunable Blue Light Emitters” Chem. Commun. 2013, 49, 4160-4162.
Liptak, M.D.; Wen, X.; Bren, K.L. “NMR and DFT Investigation of Heme Ruffling: Functional Implications for Cytochrome c” J. Am. Chem. Soc. 2010, 132, 9753-9763.
Liptak, M.D.; Datta, S.; Matthews, R.G.; Brunold, T.C. "Spectroscopic Study of the Cobalamin-Dependent Methionine Synthase in the Activation Conformation: Effects of the Y1139 Residue and S-Adenosylmethionine on the B12 Cofactor" J. Am. Chem. Soc. 2008, 130, 16374-16381.
Liptak, M.D.; Shields, G.C. “Accurate pKa Calculations for Carboxylic Acids Using Complete Basis Set and Gaussian-n Models Combined with CPCM Continuum Solvation Methods” J. Am. Chem. Soc. 2001, 123, 7314-7319.
Awards and Recognition
- 2009 - Ruth Kirschstein-NRSA
- 2015 - Paul Saltman Award
Areas of Expertise and/or Research
bioinorganic chemistry, optical spectroscopy, computational chemistry
- Ph.D., University of Wisconsin-Madison, 2008
- Postdoctoral fellowship, University of Rochester, 2008-2011
- (802) 656-0161