Bridging the gap between theoretical and experimentally inferred reorganization energy


Jonny Johannes, Ehsan Zahedinejad, Dennis Salahub, Barry Sanders



  • Institute for Quantum Science and Technology
  • University of Calgary
  • November 12, 2015
  • PHAS Symposium 2015

Overview

  • Background
  • Problem
  • Motivation
  • Methods
  • Results
  • Discussion

Background - Biology

Full

Photo credit: Richard Evans-Gowing at the University of East Anglia

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Background - Physical Chemistry

Marcus Theory


$$k_{\text{ET}} = \frac{2\pi}{\hbar}\left| H_{AB} \right|^2 \frac{1}{\sqrt{4 \pi k_{\text{B}} T}} \text{exp}\left(-\frac{\left( \lambda + \Delta G^\circ \right)^2}{4 \lambda k_{\text{B}} T}\right)$$
$$ \lambda_{\text{St}} = -\frac{\langle V_{\text{os}} \rangle}{2} \hspace{3cm} \lambda_{\text{var}} = \lambda_{\text{St}} - \frac{\langle \delta V_{\text{o}s} \delta V_{\text{o}p} \rangle}{2k_{\text{B}}T} $$

Martin, D and Matyushov, D. JCP, 2015.

Bill Nye

Problem

Disagreement between the theoretically calculated and experimentally inferred reorganization energy for the MADH-amicyanin complex.

Motivation

Efficient, site-selective electron transfer is crucial for effective metabolic processes.

Diseases associated with free radical production.

Characterize efficient atomic scale wires.

Methods

  • Apply the two-parameter model to the MADH-amicyanin system.

  • Quantum calculations using density functional theory.

  • Classical calculations using molecular mechanics, and molecular dynamics.

  • Combined classical and quantum.

Results

RMSD
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Discussion

  • Simulations allow us to probe inaccessible time and length scales.

  • Fluctuations in how the protein rearranges itself and surrounding solvent is vital.

  • $\lambda_{\text{var}}$ is an attempt to account for these fluctuations.
RMSD

Conclusion

  • Disagreement in theoretical and experimentally inferred $\lambda$ in MADH-amicyanin.

  • Claim: two-paramenter model, accounting for statistics around protein-solvent electrostatic interactions can bridge the gap between theory and experiment.

  • Novelty: application of the two-parameter model to MADH-amicyanin.
RMSD

Thank you, merci!