A5007631091- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Photosynthetic Processes and Mechanisms
- Magnetism in coordination complexes
- Spectroscopy and Quantum Chemical Studies
- Electron Spin Resonance Studies
- Metal complexes synthesis and properties
- Lanthanide and Transition Metal Complexes
- Crystallography and molecular interactions
- Porphyrin and Phthalocyanine Chemistry
- Metal-Catalyzed Oxygenation Mechanisms
- Metal-Organic Frameworks: Synthesis and Applications
- Advanced Chemical Physics Studies
- Photochemistry and Electron Transfer Studies
- Catalytic Processes in Materials Science
- Advanced NMR Techniques and Applications
- Organometallic Complex Synthesis and Catalysis
- Supramolecular Chemistry and Complexes
- Catalysis and Oxidation Reactions
- Photoreceptor and optogenetics research
- Enzyme Structure and Function
- Microbial metabolism and enzyme function
- Amino Acid Enzymes and Metabolism
- Free Radicals and Antioxidants
- Electrocatalysts for Energy Conversion
Rensselaer Polytechnic Institute
2020-2022
University of Manchester
2015-2020
Engineering and Physical Sciences Research Council
2015-2019
University of Illinois Urbana-Champaign
2012-2017
University of Stuttgart
2009
ETH Zurich
2009
The flavoenzyme monoamine oxidase (MAO) regulates mammalian behavioral patterns by modulating neurotransmitters such as adrenaline and serotonin. mechanistic basis which underpins this enzyme is far from agreed upon. Reported herein that the combination of a synthetic flavin alloxan generates catalyst system facilitates biomimetic amine oxidation. Mechanistic electron paramagnetic (EPR) spectroscopic data supports conclusion reaction proceeds through radical manifold. This provides first...
Michael addition (MA) is one of the most well studied chemical transformation in synthetic chemistry. Here, we report synthesis and crystal structures a library 3d/4f coordination clusters (CCs) formulated as [ZnII2YIII2L4(solv)X(Z)Y] study their catalytic properties toward MA nitrostyrenes with barbituric acid derivatives. Each CC presents two borderline hard/soft Lewis acidic ZnII centers hard YIII defect dicubane topology that brings different metals into proximity ∼3.3 Å. Density...
An investigation of the redox-active tris[4-(pyridin-4-yl)phenyl]amine (NPy3) ligand in solution state and upon its incorporation into solid-state metal-organic framework (MOF) [Zn(NPy3)(NO2)2·xMeOH·xDMF]n (MeOH = methanol DMF N,N-dimethylformamide) was conducted using situ UV/vis/near-IR, electron paramagentic resonance (EPR), fluorescence spectroelectrochemical experiments. Through this multifaceted approach, properties were elucidated quantified as a function redox triarylamine core,...
Selective 15N isotope labeling of the cytochrome bo3 ubiquinol oxidase from Escherichia coli with auxotrophs was used to characterize hyperfine couplings side-chain nitrogens residues R71, H98, and Q101 peptide R71 H98 around semiquinone (SQ) at high-affinity QH site. The two-dimensional ESEEM (HYSCORE) data have directly identified Nε as an H-bond donor carrying largest amount unpaired spin density. In addition, weaker all SQ were determined. These reflect a distribution density over...
The structural and electrical properties of metastable defects in various types hydrogenated amorphous silicon have been studied using a powerful combination continuous wave electron-paramagnetic resonance spectroscopy, electron spin echo (ESE) decay measurements, Doppler broadening positron annihilation spectroscopy. observed dependence the paramagnetic defect density on $S$ parameter indicates that porous, nanosized void-rich materials exhibit higher densities, while dense,...
A family of [MIII2MII3]<sup>n+</sup> trigonal bipyramidal cages are characterised in the solution and solid state.
Mixed silver−sodium containing zeolite LTA was prepared by aqueous ion exchange. Reduction of oxidized Ag/NaA (12 wt %) using hydrogen leads to the formation a paramagnetic cluster possessing well-defined structure six equivalent Ag nuclei. The hyperfine silver clusters appeared only in Ag+-exchanged zeolite. Continuous wave and pulse EPR techniques revealed that unpaired spin density distribution strongly affected adsorption C2H4 at room temperature, initially symmetric reduced Ag6+ turned...
The reaction of the simple metalloligand [FeIIIL3] [HL = 1-(4-pyridyl)butane-1,3-dione] with a variety different MII salts results in formation family heterometallic cages formulae [FeIII8PdII6L24]Cl12 (1), [FeIII8CuII6L24(H2O)4Br4]Br8 (2), [FeIII8CuII6L24(H2O)10](NO3)12 (3), [FeIII8NiII6L24(SCN)11Cl] (4), and [FeIII8CoII6L24(SCN)10(H2O)2]Cl2 (5). metallic skeleton each cage describes cube which FeIII ions occupy eight vertices lie at center six faces. Direct-current magnetic susceptibility...
Abstract The flavoenzyme monoamine oxidase (MAO) regulates mammalian behavioral patterns by modulating neurotransmitters such as adrenaline and serotonin. mechanistic basis which underpins this enzyme is far from agreed upon. Reported herein that the combination of a synthetic flavin alloxan generates catalyst system facilitates biomimetic amine oxidation. Mechanistic electron paramagnetic (EPR) spectroscopic data supports conclusion reaction proceeds through radical manifold. This provides...
The cytochrome bo(3) ubiquinol oxidase from Escherichia coli resides in the bacterial cytoplasmic membrane and catalyzes two-electron oxidation of ubiquinol-8 four-electron reduction O(2) to water. one-electron reduced semiquinone forms transiently during reaction, enzyme has been demonstrated stabilize semiquinone. is also formed D75E mutant, where mutation little influence on catalytic activity, D75H which virtually inactive. In this work, wild-type as well mutant proteins were prepared...
The in vitro evolution and engineering of quorum-quenching lactonases with enhanced reactivities was achieved using a thermostable GKL enzyme as template, yielding the E101G/R230C mutant increased catalytic activity broadened substrate range [Chow, J. Y., Xue, B., Lee, K. H., Tung, A., Wu, L., Robinson, R. C., Yew, W. S. (2010) Biol. Chem. 285, 40911-40920]. This possesses (β/α)8-barrel fold is member PLL (phosphotriesterase-like lactonase) group enzymes within amidohydrolase superfamily...
Silver containing catalysts were prepared by aqueous ion exchange of Ag+ against Na+ in an LTA zeolite. A well-defined paramagnetic cluster consisting six equivalent silver nuclei was obtained after oxidation and hydrogen reduction. Continuous wave EPR demonstrates that the reduced Ag6+ clusters are isolated all atoms close to equivalent. Upon addition NO gas at room temperature, spectrum disappears immediately. new has character adsorbed NO. Its line is split hyperfine interaction between...
The electronic structure and geometry of redox-active metal cofactors in proteins are tuned by the pattern hydrogen bonding with backbone peptide matrix. In this study we developed a method for selective amino acid labeling hyperthermophilic archaeal metalloprotein engineered Escherichia coli auxotroph strains, applied to resolve bond interactions reduced Rieske-type [2Fe-2S] cluster two-dimensional pulsed electron spin resonance technique. Because deep spin–echo envelope modulation two...
Despite its prevalence, cation exchange is not the only immobilization pathway for foreign cations in epochal MOF-5 metal–organic framework.
In the Q(B) site of Rhodobacter sphaeroides photosynthetic reaction center, donation a hydrogen bond from hydroxyl group Ser-L223 to ubisemiquinone formed after first flash is debatable. this study, we use combination spectroscopy and quantum mechanics/molecular mechanics (QM/MM) calculations comprehensively explore topic. We show that ENDOR, ESEEM, HYSCORE spectroscopic differences between mutant L223SA wild-type sample (WT) are negligible, indicating only minor perturbations in spin...
Annealing [FeL2 ][BF4 ]2 ⋅2 H2 O (L=2,6-bis-[5-methyl-1H-pyrazol-3-yl]pyridine) affords an anhydrous material, which undergoes a spin transition at T1/2 =205 K with 65 thermal hysteresis loop. This occurs through sequence of phase changes, were monitored by powder diffraction in earlier study. [CuL2 and [ZnL2 are not perfectly isostructural but, unlike the iron compound, they undergo single-crystal-to-single-crystal dehydration upon annealing. All annealed compounds initially adopt same...
A family of heterometallic Anderson-type 'wheels' general formula [MM(hmp)12]4+ (MIII = Cr or Al and MII Ni Zn, Hhmp 2-pyridinemethanol) has been extended to include MIII Co, Fe, Mn Cu, affording five new species formulae [Cr2Co5(hmp)12](ClO4)4 (1), [Cr2Fe5(hmp)12](ClO4)4 (2), [Cr2Mn5(hmp)12](ClO4)4 (3), [Cr2Cu5(hmp)12](ClO4)2(NO3)2 (4) [Al2Co5(hmp)12](ClO4)4 (5). As per previous members, the metallic skeleton common cations 1-5 describes a centred hexagon with two sites disordered around...
Three complexes of cyclotricatechylene (H6ctc), [{PtL}3(μ3-ctc)], have been synthesised: (L = 1,2-bis(diphenylphosphino)benzene {dppb}, 1; L 1,2-bis(diphenylphosphino)ethane {dppe}, 2; 4,4'-bis(tert-butyl)-2,2'-bipyridyl { t Bu2bipy}, 3). The show three low-potential, chemically reversible voltammetric oxidations separated by ca. 180 mV, corresponding to stepwise oxidation the [ctc]6- catecholato rings semiquinonate level. redox series [1]0/1+/2+/3+ and [3]0/1+/2+/3+ characterised UV/vis/NIR...
The formation mechanism and bonding in a rare vanadocene complex with N-heterocyclic silylene (1,3-bis(2,6-diisopropylphenyl)-1,3-diaza-2-silacyclopent-4-en-2-ylidene) is elucidated using combination of experimental theoretical techniques.
Two-dimensional 13 C HYSCORE spectroscopy, in conjunction with QM/MM and DFT, indicates that methanol binds to the Mn 4 Ca-oxo cluster S 2 state of D1-N87A photosystem II from Synechocystis sp. PCC 6803.