Paras N. Prasad

Korea University, Sŏul, Seoul, South Korea

Are you Paras N. Prasad?

Claim your profile

Publications (691)2793.83 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Silica-based nanoparticles are well known for their ease of synthesis, structural robustness, resistance to biofouling, enhanced storage stability, and multimodality. Organically modified silica (ormosil) nanoparticles are a special type of hybrid nanoparticle known for encapsulating/conjugating active agents for applications such as in photodynamic therapy (PDT), gene therapy and diagnostic imaging. Herein, we report the use of ormosil nanoparticles as a sustained release drug delivery vehicle, using the well-known anticancer and fluorescent drug doxorubicin (Dox). These drug/dye loaded nanoparticles have been synthesized within an oil-in-water microemulsion medium, and characterized for their size, shape, porosity, and optical properties. Nanoencapsulation significantly enhanced the optical stability of a dye against chemical quenching. Particle-size variation could be achieved by changing the amount of co-surfactant. However, size variation did not affect their pore size. The release pattern of encapsulated drug was found to depend on the size of the nanoparticles, with optimal drug release observed for the 50 nm particles at about 70% in a sustained manner over two weeks. Confocal bioimaging was used to demonstrate the differential pattern of cellular uptake of the free and nanoencapsulated drugs, as the sub-cellular distribution of nanoencapsulated Dox is guided by the nanoparticles distributing throughout the cytosol. Cell viability (MTS) and soft-agar colony formation assays in vitro have confirmed the cytotoxic effects of the drug loaded nanoparticles, but not of the blank nanoparticles. The results indicate that ormosil nanoparticles can act as a sustained release vehicle of potent lipophilic anticancer drugs.
    RSC Advances 10/2014; 4(2014):53498-54504. DOI:10.1039/c4ra10293b · 3.71 Impact Factor
  • Source
    Andrey N Kuzmin, Artem Pliss, Paras N Prasad
    [Show abstract] [Hide abstract]
    ABSTRACT: Fixation of biological sample is an essential technique applied in order to "freeze" in time the intracellular molecular content and permit mapping of cellular molecules. However, fixation induces changes of the cellular molecular structure, which mask physiological distribution of biomolecules and bias interpretation of results. Accurate, sensitive, and comprehensive characterization of changes in biomolecular composition, occurring during fixation, is crucial for proper analysis of experimental data. Here we apply Biomolecular Component Analysis for Raman spectra measured in the same nucleoli of HeLa cells before and after fixation by either formaldehyde solution or by chilled ethanol. It is found that fixation in formaldehyde does not strongly effect the Raman spectra of nucleolar biomolecular components, but may significantly decrease the nucleolar RNA concentration. At the same time, ethanol fixation leads to a proportional increase (up to 40%) in concentrations of nucleolar proteins and RNA, most likely due to cell shrinkage occurring in the presence of coagulant fixative. Ethanol fixation also triggers changes in composition of nucleolar proteome, as indicated by an overall reduction of the α-helical structure of proteins and increase in the concentration of proteins containing the β-sheet conformation. We conclude that cross-linking fixation is a more appropriate protocol for mapping of proteins in situ. At the same time, ethanol fixation is preferential for studies of RNA-containing macromolecules. We supplemented our quantitative Raman spectroscopic measurements with mapping of the protein and lipid macromolecular groups in live and fixed cells using Coherent Anti-Stokes Raman Scattering nonlinear optical imaging.
    Analytical Chemistry 09/2014; 86(21). DOI:10.1021/ac503172b · 5.83 Impact Factor
  • Source
    Andrey N Kuzmin, Artem Pliss, Paras N Prasad
    [Show abstract] [Hide abstract]
    ABSTRACT: Fixation of biological sample is an essential technique applied in order to " freeze " in time the intracellular molecular content and permit mapping of cellular molecules. However, fixation induces changes of the cellular molecular structure, which mask physiological distribution of biomolecules and bias interpretation of results. Accurate, sensitive, and comprehensive characterization of changes in biomolecular composition, occurring during fixation, is crucial for proper analysis of experimental data. Here we apply Biomolecular Component Analysis for Raman spectra measured in the same nucleoli of HeLa cells before and after fixation by either formaldehyde solution or by chilled ethanol. It is found that fixation in formaldehyde does not strongly effect the Raman spectra of nucleolar biomolecular components, but may significantly decrease the nucleolar RNA concentration. At the same time, ethanol fixation leads to a proportional increase (up to 40%) in concentrations of nucleolar proteins and RNA, most likely due to cell shrinkage occurring in the presence of coagulant fixative. Ethanol fixation also triggers changes in composition of nucleolar proteome, as indicated by an overall reduction of the α-helical structure of proteins and increase in the concentration of proteins containing the β-sheet conformation. We conclude that cross-linking fixation is a more appropriate protocol for mapping of proteins in situ. At the same time, ethanol fixation is preferential for studies of RNA-containing macromolecules. We supplemented our quantitative Raman spectroscopic measurements with mapping of the protein and lipid macromolecular groups in live and fixed cells using Coherent Anti-Stokes Raman Scattering nonlinear optical imaging.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The efficiency of most photovoltaic devices is severely limited by near-infrared (NIR) transmission losses. To alleviate this limitation, a new type of colloidal upconversion nanoparticles (UCNPs), hexagonal core/shell-structured β-NaYbF4:Er3+(2%)/NaYF4:Nd3+(30%), is developed and explored in this work as an NIR energy relay material for dye-sensitized solar cells (DSSCs). These UCNPs are able to harvest light energy in multiple NIR regions, and subsequently convert the absorbed energy into visible light where the DSSCs strongly absorb. The NIR-insensitive DSSCs show compelling photocurrent increases through binary upconversion under NIR light illumination either at 785 or 980 nm, substantiating efficient energy relay by these UCNPs. The overall conversion efficiency of the DSSCs was improved with the introduction of UCNPs under simulated AM 1.5 solar irradiation.
    ACS Applied Materials & Interfaces 09/2014; 6(20). DOI:10.1021/am504866g · 5.90 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Controllable 3D assembly of multicomponent inorganic nanomaterials by precisely positioning two or more types of nanoparticles to modulate their interactions and achieve multifunctionality remains a major challenge. The diverse chemical and structural features of biomolecules can generate the compositionally specific organic/inorganic interactions needed to create such assemblies. Toward this aim, we studied the materials-specific binding of peptides selected based upon affinity for Ag (AgBP1 and AgBP2) and Au (AuBP1 and AuBP2) surfaces, combining experimental binding measurements, advanced molecular simulation, and nanomaterial synthesis. This reveals, for the first time, different modes of binding on the chemically similar Au and Ag surfaces. Molecular simulations showed flatter configurations on Au and a greater variety of 3D adsorbed conformations on Ag, reflecting primarily enthalpically driven binding on Au and entropically driven binding on Ag. This may arise from differences in the interfacial solvent structure. On Au, direct interaction of peptide residues with the metal surface is dominant, while on Ag, solvent-mediated interactions are more important. Experimentally, AgBP1 is found to be selective for Ag over Au, while the other sequences have strong and comparable affinities for both surfaces, despite differences in binding modes. Finally, we show for the first time the impact of these differences on peptide mediated synthesis of nanoparticles, leading to significant variation in particle morphology, size, and aggregation state. Because the degree of contact with the metal surface affects the peptides ability to cap the nanoparticles and thereby control growth and aggregation, the peptides with the least direct contact (AgBP1 and AgBP2 on Ag) produced relatively polydispersed and aggregated nanoparticles. Overall, we show that thermodynamically different binding modes at metallic interfaces can enable selective binding on very similar inorganic surfaces and can provide control over nanoparticle nucleation and growth. This supports the promise of bionanocombinatoric approaches that rely upon materials recognition.
    Chemistry of Materials 09/2014; 26(17):4960-4969. DOI:10.1021/cm501529u · 8.54 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrate, for the first time, the use of plasmonic semiconductor nanocrystals for the analysis of heavy metal ions in water. This highly sensitive localized surface plasmon resonance (LSPR)-based platform is built on glutathione (GSH) capped Cu2−xS nanocrystals, which exhibit LSPR at near infrared (NIR) wavelengths. Aggregation of GSH-capped Cu2−x S occurs specifically in the presence of lead ions, Pb2+, producing a shift in the LSPR absorbance peak. Under optimal assay conditions, the detection limit was as low as 0.25 μM (52.5 ppb) of Pb2+. This provides a new plasmonic semiconductor nanocrystal-based assay for the detection of environmentally hazardous materials. The assay employs non-toxic and earth-abundant elements and could potentially be produced at much lower cost than similar gold nanoparticle-based assays.
    Plasmonics 08/2014; 9(4):893-898. DOI:10.1007/s11468-014-9694-3 · 2.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Hexagonal NaYbF4:Tm3+ upconversion nanoparticles hold promise for use in high contrast near infrared-to-near infrared (NIR-to-NIR) in vitro and in vivo bioimaging. However, significant hurdles remain in their preparation, their morphology and size control, as well as in upconversion efficiency enhancement. Here, we describe a systematic approach to produce highly controlled hexagonal NaYbF4:Tm3+ nanoparticles with superior upconversion. We found that doping appropriate concentrations of trivalent gadolinium (Gd3+) can convert NaYbF4:Tm3+ 0.5% nanoparticles with cubic phase and irregular shape into highly monodisperse NaYbF4:Tm3+ 0.5% nanoplates or nanospheres in a pure hexagonal-phase and of tunable size. The intensity and the lifetime of the upconverted NIR luminescence at 800 nm exhibited a direct dependence on the size distribution of the resulting nanoparticles, being ascribed to the varied surface-to-volume ratios determined by the different nanoparticle size. Epitaxial growth of a thin NaYF4 shell layer of ~2 nm on the ~22 nm core of hexagonal NaYbF4:Gd3+ 30%/Tm3+ 0.5% nanoparticles resulted in a 350 fold NIR upconversion efficiency enhancement, due to effective suppression of surface-related quenching mechanisms. In vivo NIR-to-NIR upconversion imaging was demonstrated using a dispersion of phospholipid-polyethylene glycol (DSPE-PEG)-coated core/shell nanoparticles in phosphate buffered saline.
    ACS Applied Materials & Interfaces 07/2014; 6(16). DOI:10.1021/am503288d · 5.90 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report the operation and characterization of an upconversion random laser emitting at 560 nm, when directly pumped by three photon excitation at the near IR wavelength of 1350 nm in a colloidal dye solution in the weakly scattering regime. Using a special dye with a high three-photon cross-section and TiO2 nanoparticles (250 nm diameter), optimized upconverted emission was obtained for particle densities of ~2 x 10^9/cm^3. A strong dependence on the nanoparticle concentration and the pumping area was verified. The presence of spikes with linewidths ~0.4 nm in the emitted spectrum is the signature of coherent emission from this three-photon pumped random laser.
    Optics Express 06/2014; Opt. Express(22):14305. DOI:10.1364/OE.22.014305 · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Development of long-term implantable luminescent biosensors for subcutaneous oxygen has proved challenging due to difficulties in immobilizing a biocompatible matrix that prevents sensor aggregation yet maintains sufficient concentration for transdermal optical detection. Here, Pd-porphyrins can be used as PEG cross-linkers to generate a polyamide hydrogel with extreme porphyrin density (≈5 × 10(-3) m). Dye aggregation is avoided due to the spatially constraining 3D mesh formed by the porphyrins themselves. The hydrogel exhibits oxygen-responsive phosphorescence and can be stably implanted subcutaneously in mice for weeks without degradation, bleaching, or host rejection. To further facilitate oxygen detection using steady-state techniques, an oxygen-non-responsive companion hydrogel is developed by blending copper and free base porphyrins to yield intensity-matched luminescence for ratiometric detection.
    Advanced Healthcare Materials 06/2014; 3(6). DOI:10.1002/adhm.201300483 · 4.88 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: J. F. Lovell and team present a new strategy to create a biocompatible implantable hydrogel for non-invasive oxygen sensing. On page 891, a tetracarboxy porphyrin is reacted with PEG diamines under conditions that result in nearly quantitative dye incorporation. Polyamide is formed with millimolar porphyrins exhibiting near infrared phosphorescence, ideal for in vivo detection. The spatially constraining mesh of the PEG-porphyrin matrix prevents porphyrin aggregation that would normally occur at such dye concentrations and attenuate the phosphorescence. The hydrogel can be implanted in mice for weeks without signs of toxicity, signal loss or polymer degradation, and could non-invasively detect changes in subcutaneous oxygen levels via transdermal phosphorescence detection.
    Advanced Healthcare Materials 06/2014; 3(6):890. DOI:10.1002/adhm.201470030 · 4.88 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Well-defined chitosan nanocapsules (CSNCs) with tunable sizes were synthesized through interfacial cross-linking of N-maleoyl-functionalized chitosan (MCS) in miniemulsions, and their application in the delivery of doxorubicin (Dox) was investigated. MCS was prepared by amidation reaction of CS with maleic anhydride in water/DMSO at 65 ºC for 20 h. Subsequently, thiol-ene cross-linking was conducted in oil-in-water miniemulsions at room temperature under UV irradiation for 1 h, using MCS as both surfactant and precursor polymer, 1,4-butanediol bis(3-mercapto-propionate) as cross-linker, and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) as co-surfactant. With the increase of co-surfactant concentration in the reaction systems, the sizes of the resulting CSNCs decreased steadily. Dox-loaded CSNCs were readily prepared by in situ encapsulation of Dox during miniemulsion cross-linking. With acid labile β-thiopropionate cross-linkages, the Dox-loaded CSNCs demonstrated faster release rate under acidic conditions. Relative to free Dox, Dox-loaded CSNCs exhibited enhanced cytotoxicity towards MCF-7 breast cancer cells without any noticeable cytotoxicity from empty CSNCs. Effective delivery of Dox into MCF-7 breast cancer cells via Dox-loaded CSNCs was also observed.
    Langmuir 03/2014; 30(14). DOI:10.1021/la4040485 · 4.38 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we report on efficient visible and near-IR upconversion emissions in colloidal hexagonal-phase core/shell NaYF<sub>4</sub>:Er<sup>3+</sup>/NaYF<sub>4</sub> nanoparticles (∼38 nm) under IR laser excitation at 1523 nm. Varying amounts of Er<sup>3+</sup> dopants were introduced into the core NaYF<sub>4</sub>:Er<sup>3+</sup> nanoparticles, revealing an optimized Er<sup>3+</sup> concentration of 10% for the highest luminescent efficiency. An inert epitaxial shell layer of NaYF<sub>4</sub> grown onto the core of the NaYF<sub>4</sub>:Er<sup>3+</sup>10% nanoparticle increased its upconversion emission intensity fivefold due to suppression of surface-related quenching mechanisms, yielding the absolute upconversion efficiency to be as high as ∼3.9±0.3% under an excitation density of 18 W/cm<sup>2</sup>. The dependence of the intensity of upconversion emission peaks on laser excitation density in the core/shell nanoparticle displayed "saturation effects" at low excitation density in the range of 1.5-18 W/cm<sup>2</sup>, which again demonstrates high upconversion efficiency.
    Optics Letters 03/2014; 39(6):1386-9. · 3.18 Impact Factor
  • Source
    Chemical Reviews 03/2014; 114(10). DOI:10.1021/cr400425h · 45.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The design, synthesis, and supramolecular organization of a nanocomposite in which nanoscale excitonic interactions between quantum dots and the chiral polymer dramatically enhance the optical activity is reported. This material is highly suitable for application in the emerging field of chiral photonics.
    Advanced Materials 03/2014; 26(10). DOI:10.1002/adma.201304071 · 15.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper is a review of the recent research in bio-based materials for photonics and electronics applications. Materials that we have been working with include: deoxyribonucleic acid (DNA)-based biopolymers and nucleobases. We will highlight work on increasing the ionic conductivity of DNA-based membranes, enhancing the direct (DC) current and photoconductivity of DNA-based biopolymers, crosslinking of DNA-based biopolymers and promising applications for DNA nucleobases. Key
    Proceedings of SPIE - The International Society for Optical Engineering 02/2014; DOI:10.1117/12.2041321 · 0.20 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we report on efficient visible and near-IR upconversion emissions in colloidal hexagonal-phase core/shell NaYF4:Er3+/NaYF4 nanoparticles (similar to 38 nm) under IR laser excitation at 1523 nm. Varying amounts of Er3+ dopants were introduced into the core NaYF4:Er3+ nanoparticles, revealing an optimized Er3+ concentration of 10% for the highest luminescent efficiency. An inert epitaxial shell layer of NaYF4 grown onto the core of the NaYF4:Er3+ 10% nanoparticle increased its upconversion emission intensity fivefold due to suppression of surface-related quenching mechanisms, yielding the absolute upconversion efficiency to be as high as similar to 3.9 +/- 0.3% under an excitation density of 18 W/cm(2). The dependence of the intensity of upconversion emission peaks on laser excitation density in the core/shell nanoparticle displayed "saturation effects" at low excitation density in the range of 1.5-18 W/cm(2), which again demonstrates high upconversion efficiency. (C) 2014 Optical Society of America
    Optics Letters 02/2014; 39(6). DOI:10.1364/OL.39.001386 · 3.18 Impact Factor
  • Source
  • [Show abstract] [Hide abstract]
    ABSTRACT: Biomimetic nanotechnologies that use peptides to guide the growth and assembly of nanostructures offer new avenues for the creation of functional nanomaterials and manipulation of their physicochemical properties. However, the impacts of peptide sequence and binding motif upon the surface characteristics and physicochemical properties of nanoparticles remain poorly understood. The configurations of the biomolecules are expected to be extremely important for directing the synthesis and achieving desired material functionality, and these binding motifs will vary with the peptide sequence. Here, we have prepared a series of Au nanoparticles capped with a variety of materials-directing peptides with known affinity for metal surfaces. These nanomaterials were characterized by UV-vis and circular dichroism spectroscopies, transmission electron microscopy, and ζ-potential measurement. Then their catalytic activity for 4-nitrophenol reduction was analyzed. The results indicate that substantially different Au-peptide interfaces are generated using different peptide sequences, even when these sequences have similar binding affinity. This is consistent with recent work showing that Au-peptide binding affinity can have varying entropic and enthalpic contributions, with enthalpically- and entropically-driven binders exhibiting quite different ensembles of configurations on the Au surface. The catalytic activity, as reflected by the measured activation energy, did not correlate with the particle size or with the binding affinity of the peptides, suggesting that the reactivity of these materials is governed by the more subtle details of the conformation of the bound peptide and on the nanoparticle surface reconstruction as dictated by the peptide structure. Such variations in both nanoparticle surface reconstruction and peptide configuration could potentially be used to program specific functionality into the peptide-capped nanomaterials.
    Nanoscale 02/2014; 6(6). DOI:10.1039/c3nr06201e · 6.74 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Nanoparticles (NPs) with high drug loading and pH-responsivity were prepared by nanoprecipitation of a hydrophobic polymer-drug conjugate (PDC). The PDC, polylactide-graft-doxorubicin (PLA-g-DOX), was synthesized by azide-alkyne click reaction to transform acetylene-functionalized PLA into PLA-graft-aldehyde (PLA-g-ALD), followed by DOX conjugation to form acid-sensitive Schiff base linkage between drug moieties and polymer scaffold. The DOX loading amount in PLA-g-DOX PDC was determined to be 32 wt% by 1H NMR and UV-Vis spectroscopies. PLA-g-DOX PDC was further used to prepare NPs with precisely controlled drug loading by nanoprecipitation in the presence of a PEGylated surfactant. The effects of organic solvent, PLA-g-DOX PDC concentration and PLA-g-DOX/surfactant mass ratio on size and size distribution of NPs were systematically examined based on analysis by dynamic light scattering (DLS) and transmission electron microscopy (TEM). NPs prepared under the optimal conditions exhibited well-defined spherical morphology with volume-average hydrodynamic diameter (Dh) around 100 nm. Due to the Schiff base conjugation linkage in PLA-g-DOX PDC, acid-sensitive drug release behavior of the NPs was observed. In vitro studies against MCF-7 breast cancer cells showed that the NPs can be readily uptaken and result in enhanced therapeutic efficiency than DOX•HCl, indicating their promising potential applications as anti-cancer nanomedicines.
    Biomacromolecules 01/2014; 15(2). DOI:10.1021/bm401471p · 5.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The luminescence efficiency of lanthanide-doped upconversion nanoparticles is of particular importance for their embodiment in biophotonic and photonic applications. Here, we show that the upconversion luminescence of typically used NaYF4:Yb3+30%/Tm3+0.5% nanoparticles can be enhanced by ~240 times through a hierarchical active core/active shell/inert shell (NaYF4:Yb3+30%/Tm3+0.5%)/NaYbF4/NaYF4 design, which involves the use of directed energy migration in the second active shell layer. The resulting active core/active shell/inert shell nanoparticles are determined to be about 11 times brighter than that of well-investigated (NaYF4:Yb3+30%/Tm3+0.5%)/NaYF4 active core/inert shell nanoparticles when excited at ~980 nm. The strategy for enhanced upconversion in Yb3+/Tm3+-codoped NaYF4 nanoparticles through directed energy migration might have implications for other types of lanthanide-doped upconversion nanoparticles.
    01/2014; 4(1-1):55-68. DOI:10.3390/nano4010055

Publication Stats

19k Citations
2,793.83 Total Impact Points

Institutions

  • 2012–2015
    • Korea University
      • Department of Chemistry
      Sŏul, Seoul, South Korea
    • Federal University of Pernambuco
      • Department of Physics
      Arrecife, Pernambuco, Brazil
  • 2001–2015
    • State University of New York
      New York, New York, United States
  • 1976–2015
    • University at Buffalo, The State University of New York
      • • Institute for Lasers, Photonics and Biophotonics
      • • Department of Chemistry
      • • Department of Electrical Engineering
      Buffalo, New York, United States
  • 2012–2014
    • Harbin Institute of Technology
      • School of Chemical Engineering and Technology
      Charbin, Heilongjiang Sheng, China
  • 2013
    • University of Delhi
      Old Delhi, NCT, India
  • 2004–2012
    • SUNY Ulster
      Kingston, New York, United States
  • 2011
    • Changchun University of Science and Technology
      Changchun, Fujian, China
    • Harvard University
      • School of Engineering and Applied Sciences
      Cambridge, Massachusetts, United States
  • 2009
    • Zhejiang University
      Hang-hsien, Zhejiang Sheng, China
  • 2008
    • National Central University
      • Department of Chemistry
      Taoyuan City, Taiwan, Taiwan
  • 2007
    • Johns Hopkins University
      Baltimore, Maryland, United States
  • 2003–2007
    • Roswell Park Cancer Institute
      • PDT Center
      Buffalo, New York, United States
  • 2006
    • University of Massachusetts Lowell
      • Department of Chemistry
      Lowell, Massachusetts, United States
    • KTH Royal Institute of Technology
      • Division of Theoretical Chemistry and Biology
      Stockholm, Stockholm, Sweden
    • Georgia Institute of Technology
      • School of Materials Science and Engineering
      Atlanta, Georgia, United States
    • Clarkson University
      • Department of Physics
      Potsdam, New York, United States
  • 2003–2004
    • University of California, Berkeley
      • Department of Chemistry
      Berkeley, MO, United States
  • 2002
    • State University of New York College at Buffalo
      • Department of Chemistry
      Buffalo, New York, United States
    • University of Toronto
      • Department of Physics
      Toronto, Ontario, Canada
  • 1993
    • Massachusetts Institute of Technology
      • Department of Materials Science and Engineering
      Cambridge, Massachusetts, United States
  • 1983
    • U.S. Department of State
      Washington, Washington, D.C., United States
  • 1972–1979
    • University of Michigan
      • Department of Chemistry
      Ann Arbor, MI, United States
  • 1972–1973
    • University of Pennsylvania
      • Laboratory for Research on the Structure of Matter
      Philadelphia, Pennsylvania, United States
    • Concordia University–Ann Arbor
      Ann Arbor, Michigan, United States