A5054564985- Advancements in Battery Materials
- Advanced Condensed Matter Physics
- Porphyrin Metabolism and Disorders
- Magnetic and transport properties of perovskites and related materials
- Electron and X-Ray Spectroscopy Techniques
- Extraction and Separation Processes
- Advanced Battery Materials and Technologies
- X-ray Spectroscopy and Fluorescence Analysis
- Heusler alloys: electronic and magnetic properties
- Porphyrin and Phthalocyanine Chemistry
- Supercapacitor Materials and Fabrication
- Advanced Chemical Physics Studies
- Metalloenzymes and iron-sulfur proteins
- Metal and Thin Film Mechanics
- Trace Elements in Health
- Folate and B Vitamins Research
- Enzyme function and inhibition
- Nanopore and Nanochannel Transport Studies
- Advanced biosensing and bioanalysis techniques
- Quantum, superfluid, helium dynamics
- Electrocatalysts for Energy Conversion
- Magnetic Properties and Synthesis of Ferrites
- Heme Oxygenase-1 and Carbon Monoxide
- Magnetism in coordination complexes
- Rare-earth and actinide compounds
University of Michigan
2015-2024
Indian Institute of Technology Guwahati
2021
SRM Institute of Science and Technology
2020
Ann Arbor Center for Independent Living
2020
Energy Institute
2014
Stanford Synchrotron Radiation Lightsource
2005-2008
SLAC National Accelerator Laboratory
2005-2008
Environmental Technologies (United States)
2007
Stanford University
2007
Lawrence Berkeley National Laboratory
2004-2006
The aggregation of human islet amyloid polypeptide (hIAPP) has been linked to beta-cell death in type II diabetes. Zinc present secretory granules shown affect this aggregation. A combination EXAFS, NMR, and AFM experiments shows that the influence zinc is most likely due stabilization prefibrillar aggregates hIAPP.
Abstract Protein design will ultimately allow for the creation of artificial enzymes with novel functions and unprecedented stability. To test our current mastery nature’s approach to catalysis, a Zn II metalloenzyme was prepared using de novo design. α 3 DH folds into stable single‐stranded three‐helix bundle binds high affinity His O coordination. The resulting catalyzes hydration CO 2 better than any small molecule model carbonic anhydrase an efficiency within 1400‐fold fastest isoform,...
Ultrafast, polarization-selective time-resolved X-ray absorption near-edge structure (XANES) was used to characterize the photochemistry of vitamin B12, cyanocobalamin (CNCbl), in solution. Cobalamins are important biological cofactors involved methyl transfer, radical rearrangement, and light-activated gene regulation, while also holding promise as agents for spatiotemporal controlled delivery therapeutics. We introduce polarized femtosecond XANES, combined with UV–visible spectroscopy,...
The layered LiNi1∕3Co1∕3Mn1∕3O2 system has recently drawn considerable interest for use as a cathode material rechargeable lithium batteries. In order to investigate the charge-compensation mechanism and structural perturbations occurring in during cycling, situ x-ray absorption spectroscopy (XAS) measurements were performed utilizing novel electrochemical cell specifically designed long term experiments. was cycled at moderate rate through typical Li-ion battery operating voltage range...
Water confined on the scale of 20 Å, is known to have different transport and thermodynamic properties from that bulk water, proton momentum distribution has recently been shown qualitatively exhibited in water. The electronic ground state nanoconfined water must be responsible for these anomalies but so far not investigated. We show here first time, using x-ray Compton scattering a computational model, configuration valence electrons particular system, Nafion, weakly electrostatically...
Lithium-ion batteries dominate the battery field, particularly for electric and hybrid vehicles. Monoclinic Li3V2(PO4)3 has emerged as one of most promising candidates cathode in lithium-ion batteries, offering better environmental safety lower cost than competing materials. We have used situ X-ray absorption spectroscopy to characterize evolution vanadium a it is cycled electrochemically. These data demonstrate presence significant kinetic effects such that measured electrochemical behavior...
<italic>In situ</italic> X-ray absorbance spectroscopy measurements show that encapsulating cobalt phthalocyanine within coordinating polymers leads to axial ligation of Co and results in enhanced rates for electrocatalytic CO<sub>2</sub> reduction.
Herein, we report a three-stranded coiled-coil (3SCC) de novo protein containing type II copper center (CuT2) composed of six-membered ring N-heterocycles. This design yields the most active homogeneous nitrite reductase (CuNiR) mimic in water. We achieved this result by controlling three factors. First, previous studies with Nδ- and Nε-methyl histidine had indicated that ligand providing pyridine-like electronic character to site was superior more donating Nδ for reduction. By substitution...
was investigated in practical Li-ion intercalation electrodes used for batteries by applying X-ray absorption spectroscopy (XAS). A special situ XAS cell constructed to charge and discharge the at current densities typically batteries. Ex measurements were made with technically relevant developed Hydro-Québec power research using as an electrolyte ethylene carbonate/dimethyl carbonate a solvent. The spectra measured initial state [containing mainly Fe(II)], which corresponds uncharged of...
Femtosecond time-resolved small and wide angle x-ray diffuse scattering techniques are applied to investigate the ultrafast nucleation processes that occur during ablation process in semiconducting materials. Following intense optical excitation, a transient liquid state of high compressibility characterized by large-amplitude density fluctuations is observed buildup these measured real time. Small-angle measurements reveal snapshots spontaneous nanoscale voids within metastable support...
The 3d–4f mixed metallacrowns frequently show single-molecule magnetic behavior. We have used Compton scattering to characterize the spin structure and orbital interactions in three isostructural metallacrowns: Gd2Mn4, Dy2Mn4, Y2Mn4. These data allow direct determination of only contribution overall moment. find that lanthanide 4f Gd2Mn4 Dy2Mn4 is aligned parallel Mn 3d spin. For Y2Mn4 (manganese-only spin) we evidence for delocalization into O 2p orbitals. Comparing with SQUID studies...
The ultrafast decay of the x-ray diffraction intensity following laser excitation an InSb crystal has been utilized to observe carrier dependent changes in potential energy surface. For first time, abrupt onset for surface softening and appearance accelerated atomic disordering a very high average density have observed. Inertial dynamics dominate early stages wide range densities between disordering.
Polarized ultrafast time-resolved X-ray absorption near edge structure (XANES) allows characterization of excited state dynamics following excitation. Excitation vitamin B12, cyanocobalamin (CNCbl), in the αβ-band at 550 nm and γ-band 365 was used to uniquely resolve axial equatorial contributions dynamics. The structural evolution molecule is best described by a coherent ballistic trajectory on potential energy surface. Prompt expansion Co cavity ca. 0.03 Å followed significant elongation...
The CblC and CblD chaperones are involved in early steps the cobalamin trafficking pathway. Cobalamin derivatives entering cytoplasm converted by to a common cob(II)alamin intermediate via glutathione-dependent alkyltransferase or reductive elimination activities. Cob(II)alamin is subsequently one of two biologically active alkylcobalamins downstream chaperones. function has been elusive although it known form complex with under certain conditions. Here, we report that provides sulfur ligand...
We have used transient absorption spectroscopy in the UV–visible and X-ray regions to characterize excited state of CarH, a protein photoreceptor that uses form B12, adenosylcobalamin (AdoCbl), sense light. With visible excitation, nanosecond-lifetime photoactive is formed with unit quantum yield. The time-resolved near edge structure difference spectrum this demonstrates AdoCbl CarH undergoes only modest structural expansion around central cobalt, behavior similar observed for...
Polarized time-resolved X-ray absorption spectroscopy at the Co K-edge is used to probe excited-state dynamics and photolysis of base-off methylcobalamin structure adenosylcobalamin. For both molecules, final minimum shows evidence for an expansion cavity around ion by ca. 0.04 0.05 Å. The 5-coordinate cob(II)alamin that formed following photodissociation has a similar base-on cob(II)alamin, with ring 0.03 Å contraction lower axial bond length relative in 6-coordinate ground state. These...
The extraction and insertion of lithium in LiFePO4 has been investigated practical Li-ion intercalation electrodes for batteries using Fe K-edge X-ray absorption spectroscopy (XAS). A versatile electrochemical situ reaction cell was utilized, specifically designed long-term experiments on battery during the lithium-extraction/insertion process electrode materials batteries. contained about 7.7 mg a 20 µm-thick Al foil. In order to determine charge compensation mechanism structural...