“Engineering Proteins for the Biomanufacturing of Light Harvesting Materials”
Leah Spangler, Ph.D.
Assistant Professor, Chemical and Life Science Engineering
Virginia Commonwealth University
Light harvesting devices, such as photovoltaics and photocatalysts, have achieved high efficiencies in recent years; however, such efficiencies require specialized inorganic materials synthesized at high temperatures and pressures with toxic precursors or solvents. Here, I demonstrate an alternative approach to synthesize functional materials in a scalable and sustainable way that uses proteins found in biological systems. In the first part of my talk, I will demonstrate the synthesis of semiconductor quantum dots using a biomineralization approach. Originally identified in the bacteria Stenotrophomonas maltophila, the biomineralization process was found to rely on a single enzyme, cystathionine g-lyase, which catalyzes nanocrystal growth by producing H2S from the amino acid L-cysteine. Biomineralization was used to generate many types of semiconductor quantum dots including CdS, PbS, CuInS2, (CuInZn)S2 and the first reported fully biomineralized core/shell quantum dots, PbS/CdS and CuInS2/ZnS. I will also demonstrate an alternative biomineralization approach which uses the artificially designed de novo protein, Construct K (ConK), to produce CdS quantum dots. ConK was not designed for function but found to catalyze production of H2S from L-cysteine precursors, enabling biomineralization of metal sulfide nanocrystals. Because de novo proteins are created by design to fold into stable structures, they are highly tolerant to mutations in their amino acid sequence, making them ideal candidates for future addition of new functionalities and properties.
In the second half of the presentation, I will motivate the replacement of inorganic functional materials with protein biomaterials by presenting two examples of light harvesting proteins with tunable optical properties. First, I demonstrate how protein structure and chromophore identity play an important role in tuning the absorbance spectra and energy transfer in the photosynthetic proteins of cryptophyte algae. By examining the natural process of photoacclimation, I show that cryptophyte algae can modify the absorbance spectra of their photosynthetic phycobiliproteins by replacing two of eight chromophores in response to changes in the spectral quality of light. Finally, I will present evidence of newly discovered intrinsic fluorescence found in proteins that lack traditional chromophores such as tryptophan or chlorophyll. This new intrinsic fluorescence originates from specific amino acid interactions that give rise to previously undetected electronic states within the protein. A mechanistic understanding of the relationship between protein structure and novel optical properties will enable the future development of proteins as new biomaterials for next-generation light harvesting devices.
Monday February 20th, 2023 at 2:30pm
Zoom
ID: 999 4976 2253
Password: CBESeminar
Dr. Leah Spangler is an Assistant Professor of Chemical and Life Science Engineering at Virginia Commonwealth University. She obtained her Ph.D. in Chemical Engineering from Lehigh University where she studied the single enzyme biomineralization of semiconductor quantum dots for biomedical and energy applications. Leah then continued her research career as a Postdoctoral Research Associate in Prof. Gregory Scholes’ lab in the Department of Chemistry at Princeton University where she studied the relationship between protein structure and optical properties of photosynthetic proteins, amyloid fibers, and de novo proteins. Leah’s current research interests include engineering de novo proteins with enzymatic activity for application in scalable biomaterial synthesis, and using time resolved spectroscopy to elucidate the photophysical mechanisms of newly discovered optical properties in supramolecular protein systems.