A5042218726- Advanced Chemical Physics Studies
- Photochemistry and Electron Transfer Studies
- Mass Spectrometry Techniques and Applications
- Spectroscopy and Quantum Chemical Studies
- Spectroscopy and Laser Applications
- Analytical Chemistry and Sensors
- Ion-surface interactions and analysis
- Atmospheric Ozone and Climate
- Molecular Junctions and Nanostructures
- Atmospheric chemistry and aerosols
- Laser Design and Applications
- Nanocluster Synthesis and Applications
- Electron Spin Resonance Studies
- Analytical Chemistry and Chromatography
- Solid-state spectroscopy and crystallography
- Monoclonal and Polyclonal Antibodies Research
- Protein purification and stability
- Various Chemistry Research Topics
- Free Radicals and Antioxidants
- Protein Structure and Dynamics
- Inorganic Fluorides and Related Compounds
- Catalytic Processes in Materials Science
- Gold and Silver Nanoparticles Synthesis and Applications
- Glycosylation and Glycoproteins Research
- Electrochemical Analysis and Applications
National Institute of Standards and Technology
2014-2023
Material Measurement Laboratory
2013-2023
Institute for Bioscience and Biotechnology Research
2013-2023
University of Maryland, College Park
2014-2021
University of Maryland, Baltimore
2014-2021
Bristol-Myers Squibb (United States)
2015
Advanced Bioscience Laboratories (United States)
2014
University of the Andes
2008-2009
George Mason University
2008-2009
Pennsylvania State University
2007
A mass resolved multiphoton ionization spectroscopy study of CH3 and CD3 has revealed two new electronic Rydberg series in these radicals. Simultaneous absorption photons prepared the excited states. Absorption a third photon from state generated parent ions methyl radical (m/z 15; m/z 18; CD3) which were detected quadrupole spectrometer. The np 2A″2 was identified by rotational assignment 3p polarization quantum defect this 0.6. constants determined for ground states B″0=4.798 cm−1...
Triphenylphosphine (PPh3) is commonly used during syntheses of stable, closed-shell monolayer protected clusters (MPCs). Models transition metal (TM) cluster and nanoparticle assign PPh3 a passive role as chemical placeholder, electron balancing species, or surfactant. This study provides the first direct evidence that proactive etching agent promotes formation specific sizes. To observe this effect, we developed colorimetric tool simultaneously monitors size distribution population...
The technique of arrested relaxation infrared chemiluminescence has been utilized for the observation emission from polyatomic substitution products fluorine atom reactions with ethylene, propene, vinyl chloride, and bromide. A new apparatus performing such experiments is described. entire apparatus, including scanning Michelson interferometer used in obtaining spectra, cooled to liquid nitrogen temperatures or lower. resulting improvement signal noise ratio allows spectra be recorded down...
Alginate is a polysaccharide produced by certain seaweeds and bacteria that consists of mannuronic acid guluronic residues. Seaweed alginate used in food industrial chemical processes, while the biosynthesis bacterial associated with pathogenic Pseudomonas aeruginosa. lyases cleave this into short oligo-uronates thus have potential to be utilized for both medicinal applications. An lyase gene, algMsp, from Microbulbifer sp. 6532A, was synthesized as an E.coli codon-optimized clone. The...
By using 193 nm laser photolysis and cavity ring-down spectroscopy to produce monitor the propargyl radical (CH2CCH), self-reaction oxygen termolecular association rate coefficients for were measured at 295 K between total pressures of 300 Pa 13300 (2.25 100 Torr) in Ar, He, N2 buffer gases. The obtained by simple second-order fits decay data observed vary with photolytic precursors: allene, chloride, bromide. a numerical fitting routine more comprehensive mechanisms, distinct coefficient...
We report a new strategy that provides stringent control for the size and dispersity of ultrasmall nanoclusters through preparation gold complex distributions formed from precursor, AuClPPh3 (PPh3 = triphenylphosphine), L6 (L6 1,6-bis(diphenylphosphino) hexane) ligand prior to reduction with NaBH4 in 1:1 methanol/chloroform solutions. Monodisperse distinct nuclearity are obtained specific ratios; [L6]/[PPh3] 4 yields [Au8L64]2+, 0.4 [Au9L64Cl]2+, 8 ligated Au10 cores form [Au10L64]2+...
Hydrogen–deuterium exchange mass spectrometry (HDX-MS) is an established, powerful tool for investigating protein–ligand interactions, protein folding, and dynamics. However, HDX-MS still emergent quality control of biopharmaceuticals establishing dynamic similarity between a biosimilar innovator therapeutic. Because industry will conduct measurements over product lifetime in multiple locations, understanding reproducibility critical. To determine the continuous-labeling, bottom-up...
Cytochrome P450 46A1 (CYP46A1) is a microsomal enzyme and cholesterol 24-hydroxylase that controls elimination from the brain. This also potential target for Alzheimer disease because it can be activated pharmacologically by some marketed drugs, as exemplified efavirenz, anti-HIV medication. Previously, we suggested pharmaceuticals activate CYP46A1 allosterically through binding to site on cytosolic protein surface, which different active facing membrane. Here identified this allosteric...
B 2A‘(3p) ← X 2A‘‘ spectra of the isotopically substituted hydroxymethyl radicals (CH2OH, CH2OD, CD2OH, CD2OD) were observed between 39 700 and 43 000 cm-1 by 2+1, 2+2, 1+1 resonance-enhanced multiphoton ionization (REMPI) spectroscopy. Analyses vibrational hot bands in these show that ν8 torsion modes ν9 CH2-wag mode are strongly coupled governed nonharmonic potential energy functions; for example, 12CH216OH(X 2A‘‘) we obtain 2ν8 = 846 ± 6 cm-1(1σ), 1ν9 234 5 cm-1, 2ν9 615 cm-1. Using...
A miniature-cavity realization of the cavity ring-down concept, which permits extension technique to spectroscopy surfaces, thin films, liquids, and, potentially, solids, is explored using a wave-optics model. The novel spectrometer design incorporates monolithic, total-internal-reflection-ring regular polygonal geometry with at least one convex facet induce stability. Evanescent waves generated by total-internal reflection probe absorption matter in vicinity cavity. Optical radiation enters...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMultiphoton ionization of methyl radicals in the gas phaseT. G. DiGiuseppe, Jeffrey W. Hudgens, and M. C. LinCite this: J. Phys. Chem. 1982, 86, 1, 36–41Publication Date (Print):January 1982Publication History Published online1 May 2002Published inissue 1 January 1982https://pubs.acs.org/doi/10.1021/j100390a008https://doi.org/10.1021/j100390a008research-articleACS PublicationsRequest reuse permissionsArticle Views209Altmetric-Citations61LEARN ABOUT...
This report outlines the determination of a reaction mechanism that can be manipulated to develop directed syntheses gold monolayer-protected clusters (MPCs) prepared by reduction solutions containing 1,3-bis(diphenylphosphino)propane (L3) ligand and Au(PPh3)Cl. Nanocluster synthesis was initiated two-coordinate phosphine-ligated [AuILL′]+ complexes (L, L′ = PPh3, L3), resulting in free radical complexes. The [Au0LL′]• radicals nucleated, forming broad size distribution ligated clusters....
An understanding of how conformational dynamics modulates function and catalysis human monoacylglycerol lipase (hMGL), an important pharmaceutical target, can facilitate the development novel ligands with potential therapeutic value. Here, we report discovery characterization allosteric, regulatory hMGL site comprised residues Trp-289 Leu-232 that reside over 18 Å away from catalytic triad. These were identified as critical mediators long-range communication contributors to integrity...
A laser photolysis reactor that uses cavity ring-down spectroscopic (CRDS) detection was characterized and used to measure the rate coefficients of three benchmark reactions known importance ethane oxidation. At 295 K approximately 700 Pa (5.5 Torr) total pressure, we obtained self-reaction k = (1.99 ± 0.44) × 10-11 cm3 molecule-1 s-1 for C2H5 + (7.26 2.4) 10-14 C2H5O2 C2H5O2. We (2.7 0.3) 10-12 pseudo-first-order association reaction O2 Ar. also measured absorption cross sections ethyl...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics of the reaction trichloromethyl + bromine and thermochemistry radical cationJeffrey W. Hudgens, Russell D. Johnson III, R. S. Timonen, J. A. Seetula, GutmanCite this: Phys. Chem. 1991, 95, 11, 4400–4405Publication Date (Print):May 1, 1991Publication History Published online1 May 2002Published inissue 1 1991https://pubs.acs.org/doi/10.1021/j100164a043https://doi.org/10.1021/j100164a043research-articleACS PublicationsRequest reuse...
The resonance enhanced multiphoton ionization (REMPI) spectrum of O2 a 1Δg between 305 and 350 nm is reported. compared to the REMPI ground state molecular oxygen in same electronic energy region, number differences respective spectra are observed. Detection limits for by calculated be 5×109 molecule cm−3 ion source mass spectrometer.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTObservation of the 3s 2A1 Rydberg states allyl and 2-methylallyl radicals with multiphoton ionization spectroscopyJeffrey W. Hudgens C. S. DulceyCite this: J. Phys. Chem. 1985, 89, 8, 1505–1509Publication Date (Print):April 1, 1985Publication History Published online1 May 2002Published inissue 1 April 1985https://pubs.acs.org/doi/10.1021/j100254a039https://doi.org/10.1021/j100254a039research-articleACS PublicationsRequest reuse permissionsArticle...
Human α1-acid glycoprotein (AGP), an acute-phase glycoprotein, exists predominantly in blood. With its ability to bind basic, lipophilic, and acidic drugs, AGP has served as a drug carrier. It been shown that the carbohydrate composition of changes response tissue injury, inflammation, or infection can have great impact on AGP's binding activities. The molecular-level details effects desialylation conformation AGP-ligand interactions, however, are unknown. Here we report use...
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The reactions of O(3P) atoms with CS2 and CS were studied by the technique arrested relaxation infrared chemiluminescence. Emissions from products CS, SO, CO observed reaction O+CS2. product channel O+CS2 is shown to be active displays a double maxima vibrational population distribution. Models are proposed account for this No emission previously reported OCS was observed, indicating that almost inactive respect energy partitioning into stretching modes OCS. A populuation distribution O+CS...
For hydrogen-deuterium exchange mass spectrometry (HDX-MS) to have an increased role in quality control of biopharmaceuticals, H for D back-exchange occurring during protein analyses should be minimized promote greater reproducibility. Standard HDX-MS analysis systems that digest proteins and separate peptides at pH 2.7 0 °C can lose >30% the deuterium marker within 15 min sample injection. This report describes architecture performance a dual-enzyme, instrument conducts liquid...