Presentation Title

Computational investigation of water oxidation catalyzed by Tryptophan

Faculty Mentor

Emily Jarvis

Start Date

18-11-2017 2:15 PM

End Date

18-11-2017 3:15 PM

Location

BSC-Ursa Minor 17

Session

Poster 3

Type of Presentation

Poster

Subject Area

physical_mathematical_sciences

Abstract

We examine the ability of Tryptophan exposed to singlet oxygen to catalytically drive the oxidation of water via two possible reaction mechanisms, one of which forms an H2O2 leaving group and the other produces H2O3. Hydroperoxide derivatives resulting from oxidation of certain amino acids have been observed experimentally and predicted as stable intermediates computationally. We perform Density Functional Theory (DFT) calculations using the B3LYP functional to determine the free energy values for reactant, product and transition state structures. Once appropriate structures have been identified, we refine our resulting wavefunctions using coupled-cluster singles and doubles with perturbative triples calculations. Additionally, the order of protonation sites of the molecule is determined to find the relative pKa’s of the various structures to compare to experimental values and ensure that the pertinent structure is used in transition state calculations. Our efforts to isolate and refine transition state structures for the two proposed mechanisms are ongoing and will allow insight into the energetic and structural feasibility of this oxidation process. Elucidating a water oxidizing mechanism of a Tryptophan derivative would represent a novel pathway with possible implications in renewable energy technology.

Summary of research results to be presented

Computed structures and energetics for two proposed mechanisms

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Nov 18th, 2:15 PM Nov 18th, 3:15 PM

Computational investigation of water oxidation catalyzed by Tryptophan

BSC-Ursa Minor 17

We examine the ability of Tryptophan exposed to singlet oxygen to catalytically drive the oxidation of water via two possible reaction mechanisms, one of which forms an H2O2 leaving group and the other produces H2O3. Hydroperoxide derivatives resulting from oxidation of certain amino acids have been observed experimentally and predicted as stable intermediates computationally. We perform Density Functional Theory (DFT) calculations using the B3LYP functional to determine the free energy values for reactant, product and transition state structures. Once appropriate structures have been identified, we refine our resulting wavefunctions using coupled-cluster singles and doubles with perturbative triples calculations. Additionally, the order of protonation sites of the molecule is determined to find the relative pKa’s of the various structures to compare to experimental values and ensure that the pertinent structure is used in transition state calculations. Our efforts to isolate and refine transition state structures for the two proposed mechanisms are ongoing and will allow insight into the energetic and structural feasibility of this oxidation process. Elucidating a water oxidizing mechanism of a Tryptophan derivative would represent a novel pathway with possible implications in renewable energy technology.