Kristy L. Mardis, Ph.D.
Electron transfer (ET) reactions crucial for a wide range of biologically important
processes including photosynthesis and respiration. In photosynthesis and respiration,
ET reactions require an organized assembly of proteins. Our long-term goal is to determine
the role of protein conformation on ET. This requires the construction and investigation
of model supramolecular assemblies capable of ET. Our hypothesis is that c-type cytochromes
will provide such a model system. We base this hypothesis on three observations:
1.) they are involved in the respiratory processes of almost all organisms, 2.) some
can self-assemble into chains, and 3.) they are capable of electron transfer when
bound to certain small molecules.
Multi-domain c-cytochromes have applications as components in bio-mimetic energy storage
devices as electric wires or catalytic sites. Detailed structural information about
these supramolecular architectures would provide insight into the role of conformation
in ET reactions and their suitability as ET agents. To resolve the structure of these
complexes in their biological environment (aqueous solutions) wide-angle x-ray scattering
techniques are employed. However, this technique requires the construction of molecular
models to interpret the experimental data. Hence, the specific goal of the proposed
work is to use molecular dynamics to create such models, calculate their x-ray scattering
patterns, and by comparison to the experimental data, provide an atomic level picture
of c-type cytochrome complexes. In this pilot project, we will: 1) Elucidate the
structure of di-, tri-, and tetramers of cytochrome c7 by construction of conformation
models via solution phase molecular dynamics calculations and comparison of the calculated
and experimental scattering data. 2) Acquire sufficient data to allow submission of
a SC1-type proposal.
Successful completion of this work will illuminate the role of conformation in ET
and the suitability of cytochrome c7 complexes as building blocks for energy storage
devices. Relevance to Public Health: The current study focuses on evaluating a self-assembling
system that has been proposed as a new solar energy storage device. More efficient
solar energy systems would allow a reduction in fossil fuel usage which, due to its
contribution to air pollution, has been linked to increasing respiratory disorders.
K. L. Mardis, “Can configuration Entropy Losses Be Predicted from the Binding Affinities
of Hydrogen-Bonded Complexes with Varying Numbers of Single Bonds?” J. Phys. Chem.
110(2), 971 (2006).
K. L. Mardis, R. Luo, M. K. Gilson, “Interpreting Trends in the Binding of Cyclic
Urea to HIV-1 Protease.” J. Mol Bio. 309, 507 (2001)
K. L. Mardis, B. J. Brune, P. Vishwanath, B. Giorgis, G. F. Payne, and M. K. Gilson,
“Intramolecular versus Intermolecular Hydrogen Bonding in the Adsorption of Aromatic
Alcohols onto an Acrylic Ester Sorbent.” J. Phys. Chem. B. 104, 4735 (2000)
J. Glemza, K. L. Mardis, A. A. Chaudhry, M. K. Gilson, and G. F. Payne. “Competition
between Intra- and Inter-molecular Hydrogen Bonding.” Ind. Eng. Chem. Res., 39, 463
K. L. Mardis, L. David, R. Luo, M. Potter, G. Payne and M. K. Gilson, “Modeling Molecular
Recognition: Method and Applications” J. Biomolecular Struct. & Des., Conv. 11, 1
K. L. Mardis, A. J. Glemza, B. J. Brune, G. F. Payne, and M. K. Gilson, “The Differential
Adsorption of Phenol Derivatives onto a Polymeric Sorbent: A Combined Molecular Modeling
and Experimental Study.” J. Phys. Chem. B., 103, 9879 (1999)
K. L. Mardis and E. L. Sibert. “The Effect of Nonadiabatic Coupling on the Calculation
of N(E,J) for the Methane Association Reaction.” J. Chem. Phys. 109, 8897 (1998).
K. L. Mardis and E. L. Sibert. “The Effectiveness of Newton’s Method for Improving
Ab Initio Force Fields with Applications for CO2 and H2CO.” J. Molec. Spec. 187, 167
K. L. Mardis and E. L. Sibert. “Derivation of Rotation-Vibration Hamiltonians that
Satisfy the Casimir Condition.” J. Chem. Phys. 106, 6618, (1997).