The proton coupled electron transfer and electron transfer reactions of photochemically prepared charge separated states of biomimetic assemblies will be addressed experimentally ad theoretically with the goal of suggesting efficient charge separating reaction networks. A homologous series of biomimetic compounds has been designed that permits a comparative study of electron transfer and proton coupled electron transfer reactions. Well characterized charge separated states of a series of these donor/acceptor complexes will be prepared optically by picosecond laser excitation. The competition between recombination and subsequent propagation of charge separated states will be monitored on the picosecond time scale by the use of time absorption spectroscopy. These experiments will permit the role of solvent dynamics, as well as energetics, on charge recombination steps to be explored. In accord with theoretical predictions that charge recombination occurring in the inverted electron transfer regime will be strongly affected by solvent dynamical properties, electron transfer rates of the biomimetic donor/acceptor complexes will be measured in solvents providing a wide range of dielectric relaxation times, as may be evocative of a protein environment. Analytic developments will focus on the consequences of solvent dynamical effects on rates in dielectrically complex solvents, and molecular dynamics simulations will be carried out to provide a detailed framework within which to interpret the experiments. As local solvation effects are important to biological electron transfer, laser induced fluorescence and time-of-flight mass spectrometry will be used to measure gas phase electron transfer rates of selectively solvated donor/acceptor complexes in supersonic jets. Electron transfer theories incorporating molecular dynamics simulations to characterize the role of specific solvation will be carried out to aid the experimental program. With the electron transfer chemistry elaborated, the role of proton motion on electron transfer will be investigated. A study of proton coupled electron transfer reactions has been initiated on a series of donor/acceptor pairs that are intramolecularly juxtaposed by a cyclic hydrogen bonded network of a dicarboxylic acid dimer or quinhydrone. Theoretical developments point to a significant proton/deuteron isotope effect on and an atypical temperature dependence of the electron transfer rate induced by proton motion. The effect of proton transfer mediation on electron transfer rates will be assessed in well defined experimental systems with the goal of elucidating these effects in the biological context.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM047274-01
Application #
3306721
Study Section
Molecular and Cellular Biophysics Study Section (BBCA)
Project Start
1992-04-01
Project End
1995-03-31
Budget Start
1992-04-01
Budget End
1993-03-31
Support Year
1
Fiscal Year
1992
Total Cost
Indirect Cost
Name
Michigan State University
Department
Type
Schools of Arts and Sciences
DUNS #
193247145
City
East Lansing
State
MI
Country
United States
Zip Code
48824
Greene, Brandon L; Nocera, Daniel G; Stubbe, JoAnne (2018) Basis of dATP inhibition of RNRs. J Biol Chem 293:10413-10414
Greene, Brandon L; Stubbe, JoAnne; Nocera, Daniel G (2018) Photochemical Rescue of a Conformationally Inactivated Ribonucleotide Reductase. J Am Chem Soc 140:15744-15752
Guo, Junling; Suástegui, Miguel; Sakimoto, Kelsey K et al. (2018) Light-driven fine chemical production in yeast biohybrids. Science 362:813-816
Lee, Wankyu; Kasanmascheff, Müge; Huynh, Michael et al. (2018) Properties of Site-Specifically Incorporated 3-Aminotyrosine in Proteins To Study Redox-Active Tyrosines: Escherichia coli Ribonucleotide Reductase as a Paradigm. Biochemistry 57:3402-3415
Ravichandran, Kanchana; Minnihan, Ellen C; Lin, Qinghui et al. (2017) Glutamate 350 Plays an Essential Role in Conformational Gating of Long-Range Radical Transport in Escherichia coli Class Ia Ribonucleotide Reductase. Biochemistry 56:856-868
Greene, Brandon L; Taguchi, Alexander T; Stubbe, JoAnne et al. (2017) Conformationally Dynamic Radical Transfer within Ribonucleotide Reductase. J Am Chem Soc 139:16657-16665
Ravichandran, Kanchana R; Zong, Allan B; Taguchi, Alexander T et al. (2017) Formal Reduction Potentials of Difluorotyrosine and Trifluorotyrosine Protein Residues: Defining the Thermodynamics of Multistep Radical Transfer. J Am Chem Soc 139:2994-3004
Ravichandran, Kanchana R; Taguchi, Alexander T; Wei, Yifeng et al. (2016) A >200 meV Uphill Thermodynamic Landscape for Radical Transport in Escherichia coli Ribonucleotide Reductase Determined Using Fluorotyrosine-Substituted Enzymes. J Am Chem Soc 138:13706-13716
Olshansky, Lisa; Greene, Brandon L; Finkbeiner, Chelsea et al. (2016) Photochemical Generation of a Tryptophan Radical within the Subunit Interface of Ribonucleotide Reductase. Biochemistry 55:3234-40
Olshansky, Lisa; Stubbe, JoAnne; Nocera, Daniel G (2016) Charge-Transfer Dynamics at the ?/? Subunit Interface of a Photochemical Ribonucleotide Reductase. J Am Chem Soc 138:1196-205

Showing the most recent 10 out of 78 publications