A5067725076- Photosynthetic Processes and Mechanisms
- Spectroscopy and Quantum Chemical Studies
- Porphyrin and Phthalocyanine Chemistry
- Electrocatalysts for Energy Conversion
- Metalloenzymes and iron-sulfur proteins
- Enzyme Structure and Function
- Photoreceptor and optogenetics research
- Photochemistry and Electron Transfer Studies
- Electrochemical Analysis and Applications
- Advanced Photocatalysis Techniques
- X-ray Diffraction in Crystallography
- Metal-Catalyzed Oxygenation Mechanisms
- TiO2 Photocatalysis and Solar Cells
- Protein Structure and Dynamics
- Algal biology and biofuel production
- CO2 Reduction Techniques and Catalysts
- Porphyrin Metabolism and Disorders
- Hemoglobin structure and function
- Lipid Membrane Structure and Behavior
- Crystallization and Solubility Studies
- Supramolecular Chemistry and Complexes
- Machine Learning in Materials Science
- Molecular Junctions and Nanostructures
- Quantum Dots Synthesis And Properties
- Microbial Fuel Cells and Bioremediation
Argonne National Laboratory
2016-2025
Florida Institute of Technology
2024
University of California, Riverside
2024
Washington University in St. Louis
2024
Alex's Lemonade Stand Foundation
2020
Northwestern University
2004-2018
North Carolina State University
2004-2009
Chicago State University
2009
National Institutes of Health
2008
Center for Information Technology
2008
Surface modification of nanocrystalline metal oxide particles with enediol ligands was found to result in altered optical properties nanoparticles. The surface results a red shift the semiconductor absorption compared unmodified nanocrystallites. is correlated dipole moment Ti−ligand complexes at particle and decreases ligand size. binding be exclusively characteristic colloids domain(<20 nm). X-ray near-edge structure measurements Ti K edge indicate that this size domain atoms adjust their...
The molecular replacement method has been succesfully used to provide a structure for the photosynthetic reaction center of Rhodopseudomonas sphaeroides at 3.7 Å resolution. Atomic coordinates derived from R. viridis were in search structure. crystallographic R ‐factor is 0.39 reflections between 8 and Å. Validity resulting model further suggested by visualization amino acid side chains not included . structure, arrangements centers unit cell. In initial calculations quinones or pigments...
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The structure of the photosynthetic reaction center (RC) from Rhodobacter sphaeroides was determined at 3.1-A resolution by molecular replacement method, using Rhodopseudomonas viridis RC as search structure. Atomic coordinates were refined with difference Fourier method and restrained least-squares refinement techniques to a current R factor 22%. tertiary complex is stabilized hydrophobic interactions between L M chains, pigments each other residues chains that coordinate Fe2+, salt bridges...
We report on two multi-chromophore building blocks that self-assemble in solution and surfaces into supramolecular light-harvesting arrays. Each block is based perylene-3,4:9,10-bis(dicarboximide) (PDI) chromophores. In one block, N-phenyl PDI chromophores are attached at their para positions to both nitrogens the 3 6 carbons of pyromellitimide form a cross-shaped molecule (PI-PDI(4)). second 1 7 fifth produce saddle-shaped (PDI(5)). These molecules partially ordered dimeric structures...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTComparison of reaction centers from Rhodobacter sphaeroides and Rhodopseudomonas viridis: overall architecture protein-pigment interactionsOssama El-Kabbani, Chong Hwan Chang, David Tiede, James Norris, Marianne SchifferCite this: Biochemistry 1991, 30, 22, 5361–5369Publication Date (Print):June 1, 1991Publication History Published online1 May 2002Published inissue 1 June...
Surface complexation of colloidal titanium dioxide nanoparticles (40−60 Å) with cysteine was investigated by electron paramagnetic resonance (EPR) and infrared (diffuse reflectance Fourier transform−DRIFT) spectroscopies. Cysteine found to bind strongly the TiO2 surface, resulting in formation new trapping sites where photogenerated electrons holes are localized. Illumination cysteine-modified at 77 K resulted radicals unpaired localized on carboxyl group. Upon warming 150 K, these...
Using a steric self-sorting strategy, the assembly of highly ordered and rigid supramolecular boxes possessing catalytic properties has been achieved in one step. The formation these assemblies, comprising up to 18 porphyrin centers, was readily confirmed by solution X-ray scattering conjunction with fluorescent spectroscopy. Size-selective enantioselective oxidation catalysis were both demonstrated.
Pair distribution function (PDF) analysis was applied for structural characterization of the cobalt oxide water-splitting catalyst films using high energy X-ray scattering. The found to be composed domains consistent with a dioxide lattice sheet structure, possibly containing Co4O4 cubane-type "defect". identifies film consist 13–14 atoms distorted coordination geometries that can modeled by alteration in terminal oxygen atom positions at domain edge. Phosphate is seen as disordered...
Solar energy conversion of water into the environmentally clean fuel hydrogen offers one best long-term solutions for meeting future demands. Nature provides highly evolved, finely tuned molecular machinery solar that exquisitely manages photon capture and processes to drive oxygenic water-splitting carbon fixation. Herein, we use Nature's specialized energy-converters, Photosystem I (PSI) protein, production from a synthetic catalyst comprised inexpensive, earth-abundant materials. PSI...
Stable TiO2/polypyrrole nanocomposites have been synthesized by a simple one-step hydrothermal method. The are capable of efficient visible-light photocatalysis driven their morphology that utilizes high concentration 4.5 nm TiO2 nanoparticles electronically coupled to 200–300 polypyrrole granules. acts as photosensitizer, and the photoactivity nanocomposite arises from electron transfer excited further across interface. is demonstrated methylene blue degradation production H2 water with...
Scrolled nanotubes of TiO2 are found to contain a large fraction undercoordinated surface sites that scroll layers anatase titania in proton-deficient aqueous systems. Reversible tube-to-sheet and sheet-to-tube transitions, associated reversible lattice transformations between quasianatase quasirutile, obtained, respectively, by protonation deprotonation (see Figure).
The synthesis and photophysical properties of butadiyne-linked chlorophyll porphyrin dimers in toluene solution several self-assembled prismatic structures are described. butadiyne linkage between the 20-positions macrocycles results new electronic transitions polarized along long axes dimers. These greatly increase ability these to absorb solar spectrum over a broad wavelength range. Femtosecond transient absorption spectroscopy reveals relative rate rotation around bond joining them....
Solution state x-ray diffraction fingerprinting is demonstrated as a method for experimentally assessing the accuracy of molecular dynamics (MD) simulations. Fourier transforms coordinate data from MD simulations are used to produce reciprocal space "fingerprints" atomic pair distance correlations that characteristic ensemble and direct numerical analogues experimental solution (SXD). SXD experiments were carried out test ability experiment simulation resolve sequence-dependent modifications...
A photocatalytic hydrogen-evolving system based on intermolecular electron transfer between native Photosystem I (PSI) and electrostatically associated Pt nanoparticles is reported. Using cytochrome c6 as the soluble mediator ascorbate sacrificial donor, visible-light-induced H2 production occurs for PSI/Pt nanoparticle biohybrids at a rate of 244 μmol (mg chlorophyll)−1 h−1 or 21 034 mol (mole PSI)−1 h−1. These results demonstrate that highly efficient photocatalysis can be obtained...
The 3 ′ untranslated region (3 UTR) of turnip crinkle virus (TCV) genomic RNA contains a cap-independent translation element (CITE), which includes ribosome-binding structural (RBSE) that participates in recruitment the large ribosomal subunit. In addition, symmetric loop RBSE plays key role coordinating incompatible processes viral and replication, require enzyme progression opposite directions on template. To understand basis for subunit intricate interplay among different parts molecule,...
Cu complexes as photosensitizers: Photoinduced charge-transfer dynamics from a copper(I) diimine complex to TiO2 nanoparticles were investigated by combining multiple time-resolved spectroscopic methods. An efficient and ultrafast electron transfer process the singlet MLCT state was discovered result of structural control owing flattening tetrahedral geometry in bulky groups ligands. Detailed facts importance specialist readers are published "Supporting Information". Such documents...
The direct conversion of sunlight into fuel is a promising means for the production storable renewable energy. Herein, we use Nature's specialized photosynthetic machinery found in Photosystem I (PSI) protein to drive solar from nickel diphosphine molecular catalyst. Upon exposure visible light, self-assembled PSI-[Ni(P2(Ph)N2(Ph))2](BF4)2 hybrid generates H2 at rate 2 orders magnitude greater than rates reported photosensitizer/[Ni(P2(Ph)N2(Ph))2](BF4)2 systems. environment enables...
Cobaloximes are popular H2 evolution molecular catalysts but have so far mainly been studied in nonaqueous conditions. We show here that they also valuable for the design of artificial hydrogenases application neutral aqueous solutions and report on preparation two well-defined biohybrid species via binding cobaloxime moieties, {Co(dmgH)2} {Co(dmgBF2)2} (dmgH2 = dimethylglyoxime), to apo Sperm-whale myoglobin (SwMb). All spectroscopic data confirm moieties inserted within pocket SwMb protein...
The solution structures of highly active Ir water-oxidation catalysts are elucidated by combining density functional theory, high-energy X-ray scattering (HEXS), and extended absorption fine structure (EXAFS) spectroscopy. We find that the dimers with mono-μ-O cores terminal anionic ligands, generated in situ through partial oxidation a common catalyst precursor. proposed supported 1H 17O NMR, EPR, resonance Raman UV–vis spectra, electrophoresis, etc. Our findings particularly valuable to...
Non-noble-metal, thin-film oxides are widely investigated as promising catalysts for oxygen evolution reactions (OER). Amorphous cobalt oxide films electrochemically formed in the presence of borate (CoBi) and phosphate (CoPi) share a common cobaltate domain building block, but differ significantly OER performance that derives from different electron–proton charge transport properties. Here, we use combination L edge synchrotron X-ray absorption (XAS), resonant emission (RXES), inelastic...