A5060124781- Metal-Catalyzed Oxygenation Mechanisms
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Porphyrin and Phthalocyanine Chemistry
- Metal complexes synthesis and properties
- Photochemistry and Electron Transfer Studies
- CO2 Reduction Techniques and Catalysts
- Catalytic Processes in Materials Science
- Radical Photochemical Reactions
- Electrochemical Analysis and Applications
- Spectroscopy and Quantum Chemical Studies
- Oxidative Organic Chemistry Reactions
- Hemoglobin structure and function
- Ga2O3 and related materials
- Porphyrin Metabolism and Disorders
- Advanced Photocatalysis Techniques
- Photosynthetic Processes and Mechanisms
- Trace Elements in Health
- Electrochemical sensors and biosensors
- X-ray Spectroscopy and Fluorescence Analysis
- Metalloenzymes and iron-sulfur proteins
- Plasmonic and Surface Plasmon Research
- Photonic Crystals and Applications
- Electron Spin Resonance Studies
- Chemical Reaction Mechanisms
Stanford University
2014-2025
SLAC National Accelerator Laboratory
2017-2025
Jeonbuk National University
2024
Stanford Synchrotron Radiation Lightsource
2017
Seoul National University
1998-2011
The multifunctional protein cytochrome c (cyt c) plays key roles in electron transport and apoptosis, switching function by modulating bonding between a heme iron the sulfur methionine residue. This Fe-S(Met) bond is too weak to persist absence of constraints. We ruptured ferrous cyt using an optical laser pulse monitored reformation within active site ultrafast x-ray pulses from free-electron laser, determining that enthalpy ~4 kcal/mol stronger than 4 comparable with calculations...
A macrocyclic ligand (L4–) comprising two pyridine(dicarboxamide) donors was used to target reactive copper species relevant proposed intermediates in catalytic hydrocarbon oxidations by particulate methane monooxygenase and heterogeneous zeolite systems. Treatment of LH4 with base Cu(OAc)2·H2O yielded (Me4N)2[L2Cu4(μ4-O)] (1) or (Me4N)[LCu2(μ-OH)] (2), depending on conditions. Complex 2 found undergo reversible 1-electron via cyclic voltammetry low-temperature chemical reactions. On the...
The question of ligand noninnocence in Cu corroles has long been a topic discussion. Presented herein is K-edge X-ray absorption spectroscopy (XAS) study, which provides direct probe the metal oxidation state, three corroles, Cu[TPC], Cu[Br8TPC], and Cu[(CF3)8TPC] (TPC = meso-triphenylcorrole), analogous Cu(II) porphyrins, Cu[TPP], Cu[Br8TPP], Cu[(CF3)8TPP] (TPP meso-tetraphenylporphyrin). K rising-edges were found to be about 0–1 eV upshifted relative substantially lower than 1–2 shifts...
Lytic polysaccharide monooxygenases (LPMOs) catalyze the degradation of recalcitrant carbohydrate substrates. These enzymes are characterized by a mononuclear Cu(I) active site with three-coordinate T-shaped "His-brace" configuration including N-terminal histidine and its amine group as ligands. This study explicitly investigates electronic structure d10 in LPMO using Kβ X-ray emission spectroscopy (XES). The lack inversion symmetry His-brace enables 3d/p mixing required for intensity...
To fully harness the potential of abundant metal coordination complex photosensitizers, a detailed understanding molecular properties that dictate and control electronic excited-state population dynamics initiated by light absorption is critical. In absence detectable luminescence, optical transient (TA) spectroscopy most widely employed method for interpreting electron redistribution in such excited states, particularly those with charge-transfer character. The assignment TA spectral...
The formylglycine-generating enzyme (FGE) is required for the posttranslational activation of type I sulfatases by oxidation an active-site cysteine to C α -formylglycine. FGE has emerged as enabling biotechnology tool due robust utility aldehyde product a bioconjugation handle in recombinant proteins. Here, we show that Cu(I)–FGE functional O 2 and reveal high-resolution X-ray crystal structure complex with its catalytic copper cofactor. We establish atom coordinated two residues nearly...
The central role of cupric superoxide intermediates proposed in hormone and neurotransmitter biosynthesis by noncoupled binuclear copper monooxygenases like dopamine-β-monooxygenase has drawn significant attention to the unusual methionine ligation CuM ("CuB") active site characteristic this class enzymes. copper-sulfur interaction proven critical for turnover, raising still-unresolved questions concerning Nature's selection an oxidizable Met residue facilitate C-H oxygenation. We describe...
In multicopper oxidases (MCOs), the type 1 (T1) Cu accepts electrons from substrate and transfers these to trinuclear cluster (TNC) where O2 is reduced H2O. The T1 potential in MCOs varies 340 780 mV, a range not explained by existing literature. This study focused on ∼350 mV difference of center Fet3p Trametes versicolor laccase (TvL) that have same 2His1Cys ligand set. A spectroscopies performed oxidized sites shows they equivalent geometric electronic structures. However, two His ligands...
Peroxynitrite (
A series of Ni complexes bearing a redox and acid-base noninnocent tetraamido macrocyclic ligand, H4-(TAML-4) {H4-(TAML-4) = 15,15-dimethyl-5,8,13,17-tetrahydro-5,8,13,17-tetraaza-dibenzo[a,g]cyclotridecene-6,7,14,16-tetraone}, with formal oxidation states NiII, NiIII, NiIV were synthesized characterized structurally spectroscopically. The X-ray crystallographic analysis the revealed square planar geometry, [Ni(TAML-4)] complex state was to be [NiIII(TAML-4•+)] NiIII ion one-electron...
We report a combined experimental and theoretical investigation of the ultrafast internal conversion (IC) intersystem crossing (ISC) dynamics two thiopyridone isomers in solution. Our study used sulfur K-edge transient x-ray absorption spectroscopy (XAS), conjunction with electronic excited state surface hopping molecular simulations XAS, to investigate impact functional group substitution pattern solvent on IC ISC. The combination localized probe simulation results enables, part,...
Highly covalent Ni bis(dithiolene) and related complexes provide an ideal platform for investigating the effects of metal-ligand orbital hybridization on excited state character dynamics. In particular, we focus ligand field states that dominate photophysics first-row transition metal complexes. We investigate if they can be significantly delocalized off center, possibly yielding photochemical reactivity more similar to charge transfer than metal-centered states. Here, [Ni(mpo)2] (mpo =...
Abstract The dynamics of photodissociation and recombination in heme proteins represent an archetypical photochemical reaction widely used to understand the interplay between chemical environment. We report a study mechanism for Fe(II)-S bond iron methionine sulfur ferrous cytochrome c . This dissociation is essential step conversion from electron transfer protein peroxidase enzyme. use ultrafast X-ray solution scattering follow 1 s 3 p (Kβ) emission spectroscopy charge spin multiplicity...
The excited-state double proton transfer of model DNA base pairs, 7-hydroxyquinoline dimers, in benzene has been investigated using picosecond time-resolved fluorescence spectroscopy. Upon excitation, whereas singly hydrogen-bonded noncyclic dimers do not go through tautomerization within the relaxation time 1400 ps, doubly cyclic undergo on scale 25 ps to form tautomeric which subsequently a conformational change 180 produce tautomers. rate constant reaction is temperature-independent,...
Photocatalytic CO2 reduction to CO under unassisted (unbiased) conditions was recently demonstrated using heterostructure catalysts that combine p-type GaN with plasmonic Au nanoparticles and Cu as cocatalysts (p-GaN/Al2O3/Au/Cu). Here, we investigate the mechanistic role of in p-GaN/Al2O3/Au/Cu photocatalytic operating K-edge X-ray absorption spectroscopy first-principles calculations. Upon exposure gas-phase H2O vapor reaction conditions, composition is identified a mixture CuI CuII oxide,...
Cu(I) active sites in metalloproteins are involved O2 activation, but their reactivity is difficult to study due the d10 closed shell which precludes use of conventional spectroscopic methods. Kβ X-ray emission spectroscopy (XES) a promising technique for investigating as it detects photons emitted by electronic transitions from occupied orbitals. Here, we demonstrate utility XES probing model complexes and metalloprotein. Using Cu(I)Cl, features double-ionization (DI) states identified...
The protonation of several Ni-centered pyridine-2-thiolate photocatalysts for hydrogen evolution is investigated using X-ray absorption spectroscopy (XAS). While the pyridinethiolate ligand was previously thought to result in partial dechelation from metal at pyridyl N site, we instead observe complete dissociation protonated and replacement by solvent molecules. A combination Ni K-edge S XAS catalyst Ni(bpy)(pyS)2 (bpy = 2,2'-bipyridine; pyS pyridine-2-thiolate) identifies structure fully...
The excited-state double proton transfer of model DNA base pairs, 7-azaindole (7AI) dimers, is explored in a low-temperature organic glass n-dodecane using picosecond time-resolved fluorescence spectroscopy. Reaction mechanisms are found to depend on the conformations 7AI dimers at moment excitation; whereas planar conformers tautomerize rapidly (<10 ps), twisted undergo form tautomeric time scale 250 ps 8 K. consist two orthogonal steps: precursor-configurational optimization and intrinsic...
The excited-state triple proton relay of 7-hydroxyquinoline (7HQ) along a hydrogen-bonded methanol chain in room temperature ionic liquids (RTILs) has been investigated using picosecond time-resolved fluorescence spectroscopy. rate constant the methanol-added RTIL is found to be slower by an order magnitude than that bulk and have unity its kinetic isotope effect. These suggest tautomerization dynamics 7HQ RTILs mainly controlled solvent reorganization form cyclically complex...
Abstract With the advancement of light‐emitting diode (LED) display technologies, optical crosstalk has emerged as a significant challenge due to increasing miniaturization and pixel density LED arrays. To address this issue, introduction nanorod (NR) shield in devices is proposed. The fabricated using straightforward process involving etching epitaxial layers with self‐assembled Ni nanoparticles SiO 2 hard mask, resulting formation an NR array. effectively reduced by confining light...