1
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Biering SB, Gomes de Sousa FT, Tjang LV, Pahmeier F, Zhu C, Ruan R, Blanc SF, Patel TS, Worthington CM, Glasner DR, Castillo-Rojas B, Servellita V, Lo NTN, Wong MP, Warnes CM, Sandoval DR, Clausen TM, Santos YA, Fox DM, Ortega V, Näär AM, Baric RS, Stanley SA, Aguilar HC, Esko JD, Chiu CY, Pak JE, Beatty PR, Harris E. SARS-CoV-2 Spike triggers barrier dysfunction and vascular leak via integrins and TGF-β signaling. Nat Commun 2022; 13:7630. [PMID: 36494335 PMCID: PMC9734751 DOI: 10.1038/s41467-022-34910-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 11/09/2022] [Indexed: 12/13/2022] Open
Abstract
Severe COVID-19 is associated with epithelial and endothelial barrier dysfunction within the lung as well as in distal organs. While it is appreciated that an exaggerated inflammatory response is associated with barrier dysfunction, the triggers of vascular leak are unclear. Here, we report that cell-intrinsic interactions between the Spike (S) glycoprotein of SARS-CoV-2 and epithelial/endothelial cells are sufficient to induce barrier dysfunction in vitro and vascular leak in vivo, independently of viral replication and the ACE2 receptor. We identify an S-triggered transcriptional response associated with extracellular matrix reorganization and TGF-β signaling. Using genetic knockouts and specific inhibitors, we demonstrate that glycosaminoglycans, integrins, and the TGF-β signaling axis are required for S-mediated barrier dysfunction. Notably, we show that SARS-CoV-2 infection caused leak in vivo, which was reduced by inhibiting integrins. Our findings offer mechanistic insight into SARS-CoV-2-triggered vascular leak, providing a starting point for development of therapies targeting COVID-19.
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Affiliation(s)
- Scott B Biering
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA.
| | | | - Laurentia V Tjang
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
| | - Felix Pahmeier
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
| | - Chi Zhu
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, USA
- Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA, USA
| | - Richard Ruan
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
| | - Sophie F Blanc
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
| | - Trishna S Patel
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
| | | | - Dustin R Glasner
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA, USA
| | - Bryan Castillo-Rojas
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
| | - Venice Servellita
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA, USA
| | - Nicholas T N Lo
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
| | - Marcus P Wong
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
| | - Colin M Warnes
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
| | - Daniel R Sandoval
- Department of Cellular and Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, La Jolla, CA, USA
| | - Thomas Mandel Clausen
- Department of Cellular and Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, La Jolla, CA, USA
| | - Yale A Santos
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA, USA
| | - Douglas M Fox
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Victoria Ortega
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY, USA
| | - Anders M Näär
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, USA
- Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA, USA
| | - Ralph S Baric
- Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Sarah A Stanley
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Hector C Aguilar
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY, USA
| | - Jeffrey D Esko
- Department of Cellular and Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, La Jolla, CA, USA
| | - Charles Y Chiu
- Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA, USA
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA, USA
- UCSF-Abbott Viral Diagnostics and Discovery Center, San Francisco, CA, USA
- Department of Medicine, University of California, San Francisco, San Francisco, CA, USA
| | - John E Pak
- Chan Zuckerberg Biohub, San Francisco, CA, USA
| | - P Robert Beatty
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Eva Harris
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, USA.
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
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2
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Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) utilizes its Spike (S) glycoprotein to bind to the angiotensin-converting enzyme 2 (ACE2) receptor for cellular entry. ACE2 is a critical negative regulator of the renin-angiotensin system and plays a protective role in preventing tissue injury. Expression of ACE2 has been shown to decrease upon infection by SARS-CoV. However, whether SARS-CoV-2 down-regulates ACE2 and the underlying mechanism and biological impact of this down-regulation have not been well defined. Here we show that the SARS-CoV-2 infection down-regulates ACE2 in vivo in an animal model, and in cultured cells in vitro, by inducing clathrin- and AP2-dependent endocytosis, leading to its degradation in the lysosome. SARS-CoV-2 S-treated cells and ACE2 knockdown cells exhibit similar alterations in downstream gene expression, with a pattern indicative of activated cytokine signaling that is associated with respiratory distress and inflammatory diseases often observed in COVID-19 patients. Finally, we have identified a soluble ACE2 fragment with a stronger binding to SARS-CoV-2 S that can efficiently block ACE2 down-regulation and viral infection. Thus, our study suggests that ACE2 down-regulation represents an important mechanism underlying SARS-CoV-2-associated pathology, and blocking this process could be a promising therapeutic strategy.
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Affiliation(s)
- Yi Lu
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Qingwei Zhu
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Douglas M. Fox
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720,Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA 94720
| | - Carol Gao
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Sarah A. Stanley
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720,Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA 94720
| | - Kunxin Luo
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720,*Address correspondence to: Kunxin Luo ()
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3
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Van Dis E, Fox DM, Morrison HM, Fines DM, Babirye JP, McCann LH, Rawal S, Cox JS, Stanley SA. IFN-γ-independent control of M. tuberculosis requires CD4 T cell-derived GM-CSF and activation of HIF-1α. PLoS Pathog 2022; 18:e1010721. [PMID: 35877763 PMCID: PMC9352196 DOI: 10.1371/journal.ppat.1010721] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 08/04/2022] [Accepted: 07/01/2022] [Indexed: 11/29/2022] Open
Abstract
The prevailing model of protective immunity to tuberculosis is that CD4 T cells produce the cytokine IFN-γ to activate bactericidal mechanisms in infected macrophages. Although IFN-γ-independent CD4 T cell based control of M. tuberculosis infection has been demonstrated in vivo it is unclear whether CD4 T cells are capable of directly activating macrophages to control infection in the absence of IFN-γ. We developed a co-culture model using CD4 T cells isolated from the lungs of infected mice and M. tuberculosis-infected murine bone marrow-derived macrophages (BMDMs) to investigate mechanisms of CD4 dependent control of infection. We found that even in the absence of IFN-γ signaling, CD4 T cells drive macrophage activation, M1 polarization, and control of infection. This IFN-γ-independent control of infection requires activation of the transcription factor HIF-1α and a shift to aerobic glycolysis in infected macrophages. While HIF-1α activation following IFN-γ stimulation requires nitric oxide, HIF-1α-mediated control in the absence of IFN-γ is nitric oxide-independent, indicating that distinct pathways can activate HIF-1α during infection. We show that CD4 T cell-derived GM-CSF is required for IFN-γ-independent control in BMDMs, but that recombinant GM-CSF is insufficient to control infection in BMDMs or alveolar macrophages and does not rescue the absence of control by GM-CSF-deficient T cells. In contrast, recombinant GM-CSF controls infection in peritoneal macrophages, induces lipid droplet biogenesis, and also requires HIF-1α for control. These results advance our understanding of CD4 T cell-mediated immunity to M. tuberculosis, reveal important differences in immune activation of distinct macrophage types, and outline a novel mechanism for the activation of HIF-1α. We establish a previously unknown functional link between GM-CSF and HIF-1α and provide evidence that CD4 T cell-derived GM-CSF is a potent bactericidal effector.
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Affiliation(s)
- Erik Van Dis
- Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California, Berkeley, Berkeley, California, United States of America
| | - Douglas M. Fox
- Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California, Berkeley, Berkeley, California, United States of America
| | - Huntly M. Morrison
- Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California, Berkeley, Berkeley, California, United States of America
| | - Daniel M. Fines
- Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California, Berkeley, Berkeley, California, United States of America
| | - Janet Peace Babirye
- Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California, Berkeley, Berkeley, California, United States of America
| | - Lily H. McCann
- School of Public Health, Division of Infectious Diseases and Vaccinology, University of California, Berkeley, Berkeley, California, United States of America
| | - Sagar Rawal
- Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California, Berkeley, Berkeley, California, United States of America
| | - Jeffery S. Cox
- Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California, Berkeley, Berkeley, California, United States of America
| | - Sarah A. Stanley
- Department of Molecular and Cell Biology, Division of Immunology and Pathogenesis, University of California, Berkeley, Berkeley, California, United States of America
- School of Public Health, Division of Infectious Diseases and Vaccinology, University of California, Berkeley, Berkeley, California, United States of America
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4
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Cho W, Shields JR, Dubrulle L, Wakeman K, Bhattarai A, Zammarano M, Fox DM. Ion – complexed chitosan formulations as effective fire-retardant coatings for wood substrates. Polym Degrad Stab 2022. [DOI: 10.1016/j.polymdegradstab.2022.109870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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5
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Song Y, Long J, Dunkers JP, Woodcock JW, Lin H, Fox DM, Liao X, Lv Y, Yang L, Chiang MYM. Micromechanical Compatibility between Cells and Scaffolds Directs the Phenotypic Transition of Stem Cells. ACS Appl Mater Interfaces 2021; 13:58152-58161. [PMID: 34808061 DOI: 10.1021/acsami.1c17504] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
This study experimentally substantiates that the micromechanical compatibility between cell and substrate is essential for cells to achieve energetically favorable mechanotransduction that directs phenotypic transitions. The argument for this compatibility is based on a thermodynamic model that suggests that the response of cells to their substrate mechanical environment is a consequence of the interchange between forms of energy governing the cell-substrate interaction. Experimental validation for the model has been carried out by investigating the osteogenic differentiation of dental follicle stem cells (DFSCs) seeded on electrospun fibrous scaffolds. Electrospinning of blends containing polycaprolactone (PCL) and silk fibroin (SF) with varying composition of cellulose nanocrystals (CNCs) resulted in three-dimensional (3D) fibrous scaffolds with bimodal distribution of fiber diameter, which provides both macroscopically stiff and microscopically compliant scaffolds for cells without affecting the surface chemical functionality of scaffolds. Atomic force microscopy (AFM) with a colloidal probe and single-cell force spectroscopy were used to characterize cell stiffness and scaffold stiffness on the cellular level, as well as cell-scaffold adhesive interaction (chemical functionality). This study has successfully varied scaffold mechanical properties without affecting their surface chemistry. In vitro tests indicate that the micromechanical compatibility between cells and scaffolds has been significantly correlated with mechanosensitive gene expression markers and osteogenic differentiation markers of DFSCs. The agreement between experimental observations and the thermodynamic model affirms that the cellular response to the mechanical environment, though biological in nature, follows the laws of the energy interchange to achieve its self-regulating behavior. More importantly, this study provides systematic evidence, through extensive and rigorous experimental studies, for the first time that rationalizes that micromechanical compatibility is indeed important to the efficacy of regenerative medicine.
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Affiliation(s)
- Yang Song
- Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
- 111 Project Laboratory of Biomechanics and Tissue Repair, Bioengineering College, Chongqing University, Chongqing 400044, China
| | - Jiaoyue Long
- Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
- Kangcell Biotechnology, Chongqing 400714, China
| | - Joy P Dunkers
- Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Jeremiah W Woodcock
- Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Hungchun Lin
- Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Douglas M Fox
- Department of Chemistry, American University, Washington, District of Columbia 20016, United States
| | - Xiaoling Liao
- Chongqing Key Laboratory of Nano/Micro Composite Materials and Devices, Chongqing University of Science and Technology, Chongqing 400050, China
| | - Yonggang Lv
- 111 Project Laboratory of Biomechanics and Tissue Repair, Bioengineering College, Chongqing University, Chongqing 400044, China
| | - Li Yang
- 111 Project Laboratory of Biomechanics and Tissue Repair, Bioengineering College, Chongqing University, Chongqing 400044, China
| | - Martin Y M Chiang
- Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
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6
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Biering SB, Van Dis E, Wehri E, Yamashiro LH, Nguyenla X, Dugast-Darzacq C, Graham TGW, Stroumza JR, Golovkine GR, Roberts AW, Fines DM, Spradlin JN, Ward CC, Bajaj T, Dovala D, Schulze-Gamen U, Bajaj R, Fox DM, Ott M, Murthy N, Nomura DK, Schaletzky J, Stanley SA. Screening a Library of FDA-Approved and Bioactive Compounds for Antiviral Activity against SARS-CoV-2. ACS Infect Dis 2021; 7:2337-2351. [PMID: 34129317 PMCID: PMC8231672 DOI: 10.1021/acsinfecdis.1c00017] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Indexed: 01/18/2023]
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has emerged as a major global health threat. The COVID-19 pandemic has resulted in over 168 million cases and 3.4 million deaths to date, while the number of cases continues to rise. With limited therapeutic options, the identification of safe and effective therapeutics is urgently needed. The repurposing of known clinical compounds holds the potential for rapid identification of drugs effective against SARS-CoV-2. Here, we utilized a library of FDA-approved and well-studied preclinical and clinical compounds to screen for antivirals against SARS-CoV-2 in human pulmonary epithelial cells. We identified 13 compounds that exhibit potent antiviral activity across multiple orthogonal assays. Hits include known antivirals, compounds with anti-inflammatory activity, and compounds targeting host pathways such as kinases and proteases critical for SARS-CoV-2 replication. We identified seven compounds not previously reported to have activity against SARS-CoV-2, including B02, a human RAD51 inhibitor. We further demonstrated that B02 exhibits synergy with remdesivir, the only antiviral approved by the FDA to treat COVID-19, highlighting the potential for combination therapy. Taken together, our comparative compound screening strategy highlights the potential of drug repurposing screens to identify novel starting points for development of effective antiviral mono- or combination therapies to treat COVID-19.
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Affiliation(s)
- Scott B. Biering
- School of Public Health, Division of Infectious
Diseases and Vaccinology, University of California, Berkeley,
Berkeley, California 94720, United States
| | - Erik Van Dis
- Department of Molecular and Cell Biology, Division of
Immunology and Pathogenesis, University of California,
Berkeley, Berkeley, California 94720, United States
| | - Eddie Wehri
- The Henry Wheeler Center for Emerging and
Neglected Diseases, 344 Li Ka Shing, Berkeley, California 94720,
United States
| | - Livia H. Yamashiro
- School of Public Health, Division of Infectious
Diseases and Vaccinology, University of California, Berkeley,
Berkeley, California 94720, United States
- Department of Molecular and Cell Biology, Division of
Immunology and Pathogenesis, University of California,
Berkeley, Berkeley, California 94720, United States
| | - Xammy Nguyenla
- School of Public Health, Division of Infectious
Diseases and Vaccinology, University of California, Berkeley,
Berkeley, California 94720, United States
| | - Claire Dugast-Darzacq
- Department of Molecular and Cell Biology, Division of
Biochemistry, Biophysics and Structural Biology, University of California,
Berkeley, Berkeley, California 94720, United
States
| | - Thomas G. W. Graham
- Department of Molecular and Cell Biology, Division of
Biochemistry, Biophysics and Structural Biology, University of California,
Berkeley, Berkeley, California 94720, United
States
| | - Julien R. Stroumza
- The Henry Wheeler Center for Emerging and
Neglected Diseases, 344 Li Ka Shing, Berkeley, California 94720,
United States
| | - Guillaume R. Golovkine
- Department of Molecular and Cell Biology, Division of
Immunology and Pathogenesis, University of California,
Berkeley, Berkeley, California 94720, United States
| | - Allison W. Roberts
- Department of Molecular and Cell Biology, Division of
Immunology and Pathogenesis, University of California,
Berkeley, Berkeley, California 94720, United States
| | - Daniel M. Fines
- Department of Molecular and Cell Biology, Division of
Immunology and Pathogenesis, University of California,
Berkeley, Berkeley, California 94720, United States
| | - Jessica N. Spradlin
- Departments of Chemistry, Molecular and Cell Biology,
and Nutritional Sciences and Toxicology, University of California,
Berkeley, Berkeley, California 94720, United
States
| | - Carl C. Ward
- Departments of Chemistry, Molecular and Cell Biology,
and Nutritional Sciences and Toxicology, University of California,
Berkeley, Berkeley, California 94720, United
States
| | - Teena Bajaj
- Department of Bioengineering, University of
California, Berkeley, Berkeley, California 94720, United
States
| | - Dustin Dovala
- Novartis Institutes for BioMedical
Research, Emeryville, California 94608, United
States
| | - Ursula Schulze-Gamen
- QBI Coronavirus Research Group Structural Biology
Consortium, University of California, San Francisco, California
94158, United States
| | - Ruchika Bajaj
- Department of Bioengineering and Therapeutic Sciences,
University of California, San Francisco, San Francisco,
California 94158, United States
| | - Douglas M. Fox
- School of Public Health, Division of Infectious
Diseases and Vaccinology, University of California, Berkeley,
Berkeley, California 94720, United States
- Department of Molecular and Cell Biology, Division of
Immunology and Pathogenesis, University of California,
Berkeley, Berkeley, California 94720, United States
| | - Melanie Ott
- Department of Medicine, Medical Scientist Training
Program, Biomedical Sciences Graduate Program, University of California, San
Francisco, San Francisco, California 94143, United
States
- J. David Gladstone
Institutes, San Francisco, California 94158, United
States
| | - Niren Murthy
- Department of Bioengineering, University of
California, Berkeley, Berkeley, California 94720, United
States
- Innovative Genomics Institute
(IGI), 2151 Berkeley Way, Berkeley, California 94704, United
States
| | - Daniel K. Nomura
- Departments of Chemistry, Molecular and Cell Biology,
and Nutritional Sciences and Toxicology, University of California,
Berkeley, Berkeley, California 94720, United
States
| | - Julia Schaletzky
- The Henry Wheeler Center for Emerging and
Neglected Diseases, 344 Li Ka Shing, Berkeley, California 94720,
United States
| | - Sarah A. Stanley
- School of Public Health, Division of Infectious
Diseases and Vaccinology, University of California, Berkeley,
Berkeley, California 94720, United States
- Department of Molecular and Cell Biology, Division of
Immunology and Pathogenesis, University of California,
Berkeley, Berkeley, California 94720, United States
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7
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Brown K, Mendoza M, Tinsley T, Bee-DiGregorio MY, Bible M, Brooks JL, Colorado M, Esenther J, Farag A, Gill R, Kalivas EN, Lara R, Lutz A, Nazaire J, Rasines Mazo A, Rodriguez RS, Schwabacher JC, Zestos AG, Hartings MR, Fox DM. Polyvinyl alcohol-montmorillonite composites for water purification: Analysis of clay mineral cation exchange and composite particle synthesis. Polyhedron 2021; 205. [PMID: 34305255 DOI: 10.1016/j.poly.2021.115297] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Municipal and residential water purification rely heavily on activated carbon (AC), but regeneration of AC is costly and cannot be performed at the point-of-use. Clay minerals (CMs) comprise a class of naturally abundant materials with known capacities for analyte adsorbance. However, the gel-forming properties of CMs in aqueous suspension pose problems for these materials being used in water-purification. In this study, we have taken three main steps to optimize the use of CMs in these applications. First, we produced several variants of montmorillonite CMs to evaluate the effect of interstitial cation hydrophobicity on the ability of the CM to uptake chargecarrying organic pollutants. These variants include CMs with the following cations: sodium, hexyl(triphenyl) phosphonium, hexyadecyl(triphenyl)phosphonium, and hexyl(tributyl)phosphonium. Second, we synthesized polymer-clay mineral composite films composed of polyvinyl alcohol (PVA), crosslinked in the presence of a CM variant. These films were evaluated for their ability to uptake malachite green (MG). Finally, we developed a one-pot synthetic method for the generation of polymer-clay particles for use in a continuous column process. We synthesized polymer-clay mineral particles using the highest performing CM (based on the film experiments) and evaluated the equilibrium capacity and kinetics of MG uptake from solution.
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Affiliation(s)
- Karlena Brown
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Mary Mendoza
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Tamanika Tinsley
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Madeleine Y Bee-DiGregorio
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Michael Bible
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Jerin L Brooks
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Melvin Colorado
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Jacob Esenther
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Andrew Farag
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Rachel Gill
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Eleni N Kalivas
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Raquel Lara
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Alex Lutz
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Jasmine Nazaire
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Alicia Rasines Mazo
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Rebeca S Rodriguez
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - James C Schwabacher
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Alexander G Zestos
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Matthew R Hartings
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
| | - Douglas M Fox
- American University, Department of Chemistry, 4400 Massachusetts Ave, NW, Washington, DC 20016, United States
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8
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Patel I, Woodcock J, Beams R, Stranick SJ, Nieuwendaal R, Gilman JW, Mulenos MR, Sayes CM, Salari M, DeLoid G, Demokritou P, Harper B, Harper S, Ong KJ, Shatkin JA, Fox DM. Fluorescently Labeled Cellulose Nanofibers for Environmental Health and Safety Studies. Nanomaterials (Basel) 2021; 11:1015. [PMID: 33921179 PMCID: PMC8071547 DOI: 10.3390/nano11041015] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/09/2021] [Accepted: 04/12/2021] [Indexed: 12/12/2022]
Abstract
An optimal methodology for locating and tracking cellulose nanofibers (CNFs) in vitro and in vivo is crucial to evaluate the environmental health and safety properties of these nanomaterials. Here, we report the use of a new boron-dipyrromethene (BODIPY) reactive fluorescent probe, meso-DichlorotriazineEthyl BODIPY (mDTEB), tailor-made for labeling CNFs used in simulated or in vivo ingestion exposure studies. Time-correlated single photon counting (TCSPC) fluorescence lifetime imaging microscopy (FLIM) was used to confirm covalent attachment and purity of mDTEB-labeled CNFs. The photoluminescence properties of mDTEB-labeled CNFs, characterized using fluorescence spectroscopy, include excellent stability over a wide pH range (pH2 to pH10) and high quantum yield, which provides detection at low (μM) concentrations. FLIM analysis also showed that lignin-like impurities present on the CNF reduce the fluorescence of the mDTEB-labeled CNF, via quenching. Therefore, the chemical composition and the methods of CNF production affect subsequent studies. An in vitro triculture, small intestinal, epithelial model was used to assess the toxicity of ingested mDTEB-labeled CNFs. Zebrafish (Danio rerio) were used to assess in vivo environmental toxicity studies. No cytotoxicity was observed for CNFs, or mDTEB-labeled CNFs, either in the triculture cells or in the zebrafish embryos.
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Affiliation(s)
- Ilabahen Patel
- Department of Chemistry, American University, Washington, DC 20016, USA;
| | - Jeremiah Woodcock
- Materials Science and Engineering Division, Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA; (J.W.); (R.B.); (S.J.S.); (R.N.); (J.W.G.)
| | - Ryan Beams
- Materials Science and Engineering Division, Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA; (J.W.); (R.B.); (S.J.S.); (R.N.); (J.W.G.)
| | - Stephan J. Stranick
- Materials Science and Engineering Division, Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA; (J.W.); (R.B.); (S.J.S.); (R.N.); (J.W.G.)
| | - Ryan Nieuwendaal
- Materials Science and Engineering Division, Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA; (J.W.); (R.B.); (S.J.S.); (R.N.); (J.W.G.)
| | - Jeffrey W. Gilman
- Materials Science and Engineering Division, Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA; (J.W.); (R.B.); (S.J.S.); (R.N.); (J.W.G.)
| | - Marina R. Mulenos
- Department of Environmental Science, Baylor University, Waco, TX 76798, USA; (M.R.M.); (C.M.S.)
| | - Christie M. Sayes
- Department of Environmental Science, Baylor University, Waco, TX 76798, USA; (M.R.M.); (C.M.S.)
| | - Maryam Salari
- Department of Environmental Health, Center for Nanotechnology and Nanotoxicology, T.H. Chan School of Public Health, Harvard University, Boston, MA 02115, USA; (M.S.); (G.D.); (P.D.)
| | - Glen DeLoid
- Department of Environmental Health, Center for Nanotechnology and Nanotoxicology, T.H. Chan School of Public Health, Harvard University, Boston, MA 02115, USA; (M.S.); (G.D.); (P.D.)
| | - Philip Demokritou
- Department of Environmental Health, Center for Nanotechnology and Nanotoxicology, T.H. Chan School of Public Health, Harvard University, Boston, MA 02115, USA; (M.S.); (G.D.); (P.D.)
| | - Bryan Harper
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331, USA; (B.H.); (S.H.)
| | - Stacey Harper
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331, USA; (B.H.); (S.H.)
| | - Kimberly J. Ong
- Vireo Advisors, LLC, Boston, MA 02130, USA; (K.J.O.); (J.A.S.)
| | - Jo Anne Shatkin
- Vireo Advisors, LLC, Boston, MA 02130, USA; (K.J.O.); (J.A.S.)
| | - Douglas M. Fox
- Department of Chemistry, American University, Washington, DC 20016, USA;
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9
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Lin YJ, Qin Z, Paton CM, Fox DM, Kong F. Influence of cellulose nanocrystals (CNC) on permeation through intestinal monolayer and mucus model in vitro. Carbohydr Polym 2021; 263:117984. [PMID: 33858577 DOI: 10.1016/j.carbpol.2021.117984] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 03/13/2021] [Accepted: 03/18/2021] [Indexed: 11/26/2022]
Abstract
Cellulose nanocrystals (CNC) as a novel ingredient in foods and pharmaceuticals still lacks the safety and functionality information. We aimed to assess the absorption of CNC in small intestine and the effect on cell viability. In the second part, the impact of CNC on substance permeation through mucus layer, including the potential functionality in improving high blood cholesterol, was tested. No noticeable amount of CNC was found to penetrate through differentiated Caco-2 monolayer and in vitro mucus layer, and CNC had low toxicity on Caco-2 cell viability up to 10 mg/mL. CNC at 2 % (w/w) may affect the permeability of the mucus layer and larger molecules are more easily influenced. CNC may also alleviate hypercholesteremia by increasing viscosity of digesta, adsorbing cholesterol, and decreasing bile acids permeation. The results suggest CNC may not penetrate the small intestinal lining and may be used as a functional supplement.
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Affiliation(s)
- Yu-Ju Lin
- Department of Food Science and Technology, University of Georgia, 100 Cedar Street, Athens, GA, 30602, USA
| | - Zijin Qin
- Department of Food Science and Technology, University of Georgia, 100 Cedar Street, Athens, GA, 30602, USA
| | - Chad M Paton
- Department of Food Science and Technology, University of Georgia, 100 Cedar Street, Athens, GA, 30602, USA; Department of Foods and Nutrition, University of Georgia, 205 Sanford Drive, Athens, GA, 30622, USA
| | - Douglas M Fox
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC, 20016, USA
| | - Fanbin Kong
- Department of Food Science and Technology, University of Georgia, 100 Cedar Street, Athens, GA, 30602, USA.
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10
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Goswami J, Haque E, Fox DM, Gilman JW, Holmes GA, Moon RJ, Kalaitzidou K. The Effect of Cellulose Nanocrystal Coatings on the Glass Fiber-Epoxy Interphase. Materials (Basel) 2019; 12:ma12121951. [PMID: 31212941 PMCID: PMC6630561 DOI: 10.3390/ma12121951] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 06/07/2019] [Accepted: 06/11/2019] [Indexed: 11/16/2022]
Abstract
This study focuses on understanding the effect of cellulose nanocrystals (CNCs) on glass fiber/epoxy interfacial interactions. The glass fibers (GF) were coated with solutions containing cellulose nanomaterial. The parameters that were investigated were the CNC surface chemistry, concentration, and dispersing medium, i.e., aqueous solution only versus emulsions. To determine the effect of the CNC coatings on the interfacial adhesion, specimens of a single GF in an epoxy matrix were prepared for GF coating by varying the coating formulations. The interfacial shear stress (IFSS) was determined by the single fiber fragmentation test (SFFT). Following the SFFT, the samples were investigated by cross-polarized microscopy in order to understand the fracture modes which are related to the nature of the interphase. According to the SFFT data and photoelastic fracture patterns, both the emulsion and aqueous coatings containing cellulose nanocrystals functionalized with methyl(triphenyl) phosphonium (CNCPh) improve the IFSS in comparison to coated GFs without CNCs.
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Affiliation(s)
- Joyanta Goswami
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
| | - Ejaz Haque
- School of Material Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
| | - Douglas M Fox
- Department of Chemistry, American University, Washington, DC 20016, USA.
| | - Jeffrey W Gilman
- Materials Science and Engineering Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
| | - Gale A Holmes
- Materials Science and Engineering Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
| | - Robert J Moon
- The Forest Products Laboratory, U.S. Forest Services, Madison, WI 53726, USA.
| | - Kyriaki Kalaitzidou
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
- School of Material Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
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11
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Mohanaraj S, Wonnenberg P, Cohen B, Zhao H, Hartings MR, Zou S, Fox DM, Zestos AG. Gold Nanoparticle Modified Carbon Fiber Microelectrodes for Enhanced Neurochemical Detection. J Vis Exp 2019:10.3791/59552. [PMID: 31132067 PMCID: PMC8266205 DOI: 10.3791/59552] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
For over 30 years, carbon-fiber microelectrodes (CFMEs) have been the standard for neurotransmitter detection. Generally, carbon fibers are aspirated into glass capillaries, pulled to a fine taper, and then sealed using an epoxy to create electrode materials that are used for fast scan cyclic voltammetry testing. The use of bare CFMEs has several limitations, though. First and foremost, the carbon fiber contains mostly basal plane carbon, which has a relatively low surface area and yields lower sensitivities than other nanomaterials. Furthermore, the graphitic carbon is limited by its temporal resolution, and its relatively low conductivity. Lastly, neurochemicals and macromolecules have been known to foul at the surface of carbon electrodes where they form non-conductive polymers that block further neurotransmitter adsorption. For this study, we modify CFMEs with gold nanoparticles to enhance neurochemical testing with fast scan cyclic voltammetry. Au3+ was electrodeposited or dipcoated from a colloidal solution onto the surface of CFMEs. Since gold is a stable and relatively inert metal, it is an ideal electrode material for analytical measurements of neurochemicals. Gold nanoparticle modified (AuNP-CFMEs) had a stability to dopamine response for over 4 h. Moreover, AuNP-CFMEs exhibit an increased sensitivity (higher peak oxidative current of the cyclic voltammograms) and faster electron transfer kinetics (lower ΔEP or peak separation) than bare unmodified CFMEs. The development of AuNP-CFMEs provides the creation of novel electrochemical sensors for detecting fast changes in dopamine concentration and other neurochemicals at lower limits of detection. This work has vast applications for the enhancement of neurochemical measurements. The generation of gold nanoparticle modified CFMEs will be vitally important for the development of novel electrode sensors to detect neurotransmitters in vivo in rodent and other models to study neurochemical effects of drug abuse, depression, stroke, ischemia, and other behavioral and disease states.
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Affiliation(s)
| | | | | | - He Zhao
- Department of Chemistry, American University
| | | | | | | | - Alexander G Zestos
- Department of Chemistry, American University; Center for Behavioral Neuroscience, American University;
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12
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Roy D, Kotula AP, Natarajan B, Gilman JW, Fox DM, Migler KB. Effect of cellulose nanocrystals on crystallization kinetics of polycaprolactone as probed by Rheo-Raman. POLYMER 2018; 153. [PMID: 31274931 DOI: 10.1016/j.polymer.2018.08.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The development of biocompatible polymer nano-composites that enhance mechanical properties while maintaining thermoplastic processability is a longstanding goal in sustainable materials. When the matrix is semi-crystalline, the nanoparticles may induce significant changes to crystallization kinetics and morphology due to their ability to act as nucleating agents. To fully model this behavior in a process line, an understanding of the relationship between crystallinity and modulus is required. Here, we introduce a scalable model system consisting of surface-compatibilized cellulose nanocrystals (CNC) dispersed into poly(ε-caprolactone) (PCL) and study the effects of nanoparticle concentration on isothermal crystallization kinetics. The dispersion is accomplished by exchange of the Na+ of sulfated cellulose nanocrystals by tetra-butyl ammonium cations (Bu4N+) followed by melt mixing via twin-screw extrusion. Crystallization kinetics are measured through the recently developed rheo-Raman instrument which extracts the relationship between the growth of the transient mechanical modulus and that of crystallinity. With extrusion and increasing CNC content, we find the expected enhancement of crystallization rate, but we moreover find a significant change in the relative kinetics of increase in modulus versus crystallinity. We analyze this via generalized effective medium theory which allows computation of a critical percolation threshold ξ c and discuss the results in terms of a change in nucleation density and a change in the anisotropy of crystallization.
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Affiliation(s)
- Debjani Roy
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Anthony P Kotula
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Bharath Natarajan
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.,Department of Physics, Georgetown University, Washington, DC, USA
| | - Jeffrey W Gilman
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Douglas M Fox
- Department of Chemistry, American University, Washington, DC, USA
| | - Kalman B Migler
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
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13
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Foster EJ, Moon RJ, Agarwal UP, Bortner MJ, Bras J, Camarero-Espinosa S, Chan KJ, Clift MJD, Cranston ED, Eichhorn SJ, Fox DM, Hamad WY, Heux L, Jean B, Korey M, Nieh W, Ong KJ, Reid MS, Renneckar S, Roberts R, Shatkin JA, Simonsen J, Stinson-Bagby K, Wanasekara N, Youngblood J. Current characterization methods for cellulose nanomaterials. Chem Soc Rev 2018; 47:2609-2679. [PMID: 29658545 DOI: 10.1039/c6cs00895j] [Citation(s) in RCA: 354] [Impact Index Per Article: 59.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A new family of materials comprised of cellulose, cellulose nanomaterials (CNMs), having properties and functionalities distinct from molecular cellulose and wood pulp, is being developed for applications that were once thought impossible for cellulosic materials. Commercialization, paralleled by research in this field, is fueled by the unique combination of characteristics, such as high on-axis stiffness, sustainability, scalability, and mechanical reinforcement of a wide variety of materials, leading to their utility across a broad spectrum of high-performance material applications. However, with this exponential growth in interest/activity, the development of measurement protocols necessary for consistent, reliable and accurate materials characterization has been outpaced. These protocols, developed in the broader research community, are critical for the advancement in understanding, process optimization, and utilization of CNMs in materials development. This review establishes detailed best practices, methods and techniques for characterizing CNM particle morphology, surface chemistry, surface charge, purity, crystallinity, rheological properties, mechanical properties, and toxicity for two distinct forms of CNMs: cellulose nanocrystals and cellulose nanofibrils.
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Affiliation(s)
- E Johan Foster
- Department of Materials Science and Engineering, Virginia Tech, 445 Old Turner St, 203 Holden Hall, Blacksburg, 24061, VA, USA.
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14
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Fox DM, Carrega P, Ren Y, Caillouet P, Bouillon C, Robert S. How wildfire risk is related to urban planning and Fire Weather Index in SE France (1990-2013). Sci Total Environ 2018; 621:120-129. [PMID: 29179067 DOI: 10.1016/j.scitotenv.2017.11.174] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 11/15/2017] [Accepted: 11/15/2017] [Indexed: 06/07/2023]
Abstract
Wildfires burn >450,000ha of forest every year in Euro-Mediterranean countries. Many fires originate in the Wildland Urban Interface (WUI) where housing density and weather conditions affect fire occurrence. Housing density is determined by long term land use policies while weather conditions evolve quickly. The first objective was to quantify the impacts of land use policy on WUI characteristics and fire risk in SE France during 1990-2012. The second objective was to quantify how Fire Weather Index (FWI) is related to fire occurrence. WUI was mapped from 1990, 1999, and 2012 building layers and crossed with a NDVI derived vegetation layer. In all, 12 WUI categories were derived: 4 building density classes and 3 vegetation layers. The I87 FWI was based on daily temperature, wind speed, relative humidity and soil water content. Despite a 30% increase in the number of new buildings, WUI area increased by only 5% as new housing filled in open space in existing WUI area. This trend can be linked to national level urban planning legislation and forest fire protection laws. Major driver variables determining housing location were aspect, slope, and distance to city centers. Fire frequency and burned area were nonlinearly related to FWI: 73% of the 99 fires occurred during weeks with FWI values ≥90 even though these accounted for only 44% of all weeks. Burned area was even more sensitive to FWI since 97% of total burned area occurred during weeks with mean FWI values ≥90. All days with burned areas >100ha had FWI values >150. The study demonstrated that WUI legislation can be an efficient tool to limit WUI fire risk. FWI results suggest the predicted increase in extreme summer heat events with global warming could increase burned area as firefighting resources are stretched beyond capacity.
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Affiliation(s)
- D M Fox
- UMR 7300 ESPACE CNRS, Université Côte d'Azur, France.
| | - P Carrega
- UMR 7300 ESPACE CNRS, Université Côte d'Azur, France
| | - Y Ren
- UMR 7300 ESPACE CNRS, Université Côte d'Azur, France
| | - P Caillouet
- UMR 7300 ESPACE CNRS, Université Côte d'Azur, France
| | | | - S Robert
- UMR 7300 ESPACE CNRS, Université d'Aix-Marseille, France
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15
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Hart C, Abuladel N, Bee M, Kreider MC, CVitan AC, Esson MM, Farag A, Ibeh T, Kalivas EN, Larco DM, Walker Long A, Lymperopoulos L, Mendel Z, Miles N, Zareba CM, Schwabacher JC, Slucher H, Vinals J, Heddleston JM, Li W, Fox DM, Hartings MR. Protein-templated gold nanoparticle synthesis: protein organization, controlled gold sequestration, and unexpected reaction products. Dalton Trans 2017; 46:16465-16473. [PMID: 29144523 DOI: 10.1039/c7dt03275g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Emerging applications that exploit the properties of nanoparticles for biotechnology require that the nanoparticles be biocompatible or support biological recognition. These types of particles can be produced through syntheses that involve biologically relevant molecules (proteins or natural extracts, for example). Many of the protocols that rely on these molecules are performed without a clear understanding of the mechanism by which the materials are produced. We have investigated a previously described reaction in which gold nanoparticles are produced from the reaction of chloroauric acid and proteins in solution. We find that modifications to the starting conditions can alter the product from the expected solution-suspended colloids to a product where colloids are formed within a solid, fibrous protein structure. We have interrogated this synthesis, exploiting the change in products to better understand this reaction. We have evaluated the kinetics and products for 7 different proteins over a range of concentrations and temperatures. The key factor that controls the synthetic outcome (colloid or fiber) is the concentration of the protein relative to the gold concentration. We find that the observed fibrous structures are more likely to form at low protein concentrations and when hydrophilic proteins are used. An analysis of the reaction kinetics shows that AuNP formation occurs faster at lower protein (fiber-forming) concentrations than at higher protein (colloid-forming) concentrations. These results contradict traditional expectations for reaction kinetics and protein-fiber formation and are instructive of the manner in which proteins template gold nanoparticle production.
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Affiliation(s)
- Cassidy Hart
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Nouf Abuladel
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Madeleine Bee
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Megan C Kreider
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Alexander C CVitan
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Moira M Esson
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Andrew Farag
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Trisha Ibeh
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Eleni N Kalivas
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Daniel-Mario Larco
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Andrew Walker Long
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Loukas Lymperopoulos
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Zachary Mendel
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Nancy Miles
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Carly M Zareba
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - James C Schwabacher
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Helen Slucher
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Javier Vinals
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - John M Heddleston
- Semiconductor and Dimensional Metrology Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Wenyue Li
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Douglas M Fox
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
| | - Matthew R Hartings
- Department of Chemistry, American University, 4400 Massachusetts Ave, NW, Washington, DC 20016, USA.
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16
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Natarajan B, Emiroglu C, Obrzut J, Fox DM, Pazmino B, Douglas JF, Gilman JW. Dielectric Characterization of Confined Water in Chiral Cellulose Nanocrystal Films. ACS Appl Mater Interfaces 2017; 9:14222-14231. [PMID: 28394559 PMCID: PMC5508566 DOI: 10.1021/acsami.7b01674] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
A known deterrent to the large-scale development and use of cellulose nanocrystals (CNCs) in composite materials is their affinity for moisture, which has a profound effect on dispersion, wetting, interfacial adhesion, matrix crystallization, water uptake, and hydrothermal stability. To quantify and control the hydration and confinement of absorbed water in CNCs, we studied sulfated-CNCs neutralized with sodium cations and CNCs functionalized with less hydrophilic methyl(triphenyl)phosphonium cations. Films were cast from water suspensions at 20 °C under controlled humidity and drying rate, yielding CNC materials with distinguishably different dielectric properties and cholesteric structures. By controlling the evaporation rate, we obtained self-assembled chiral CNC films with extended uniformity, having helical modulation length (nominal pitch) tunable from 1300 to 600 nm. SEM imaging and UV-vis-NIR total reflectance spectra revealed tighter and more uniform CNC packing in films cast at slow evaporation rates or having lower surface energy when modified with phosphonium. The dielectric constant was measured by a noncontact microwave cavity perturbation method and fitted to a classical mixing model employing randomly oriented ellipsoidal water inclusions. The dielectric constant of absorbed water was found to be significantly smaller than that for free liquid indicating a limited mobility due to binding with the CNC "matrix". In the case of hydrophilic Na-modified CNCs, a decreasing pitch led to greater anisotropy in the shape of moisture inclusions (ellipsoidal to platelet-like) and greater confinement. In contrast, the structure of hydrophobic phosphonium-modified CNC films was found to have reduced pitch, yet the shape of confined water remained predominantly spherical. These results provide a useful perspective on the current state of understanding of CNC-water interactions as well as on CNC self-assembly mechanisms. More broadly, we believe that our results are beneficial for the realization of CNC-based functional materials and composites.
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Affiliation(s)
- Bharath Natarajan
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
- Department of Physics, Georgetown University, Washington, D.C. 20057, United States
| | - Caglar Emiroglu
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
- Department of Physics, Georgetown University, Washington, D.C. 20057, United States
| | - Jan Obrzut
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Douglas M. Fox
- Department of Chemistry, American University, Washington, D.C. 20016, United States
| | - Beatriz Pazmino
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Jack F. Douglas
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Jeffrey W. Gilman
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
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17
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Fox DM, Rodriguez RS, Devilbiss MN, Woodcock J, Davis CS, Sinko R, Keten S, Gilman JW. Correction to "Simultaneously Tailoring Surface Energies and Thermal Stabilities of Cellulose Nanocrystals Using Ion Exchange: Effects on Polymer Composites Properties for Transportation, Infrastructure, and Renewable Energy Applications". ACS Appl Mater Interfaces 2016; 8:31483. [PMID: 27806568 DOI: 10.1021/acsami.6b13695] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
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18
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Fox DM, Rodriguez RS, Devilbiss MN, Woodcock J, Davis CS, Sinko R, Keten S, Gilman JW. Simultaneously Tailoring Surface Energies and Thermal Stabilities of Cellulose Nanocrystals Using Ion Exchange: Effects on Polymer Composite Properties for Transportation, Infrastructure, and Renewable Energy Applications. ACS Appl Mater Interfaces 2016; 8:27270-27281. [PMID: 27626824 DOI: 10.1021/acsami.6b06083] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Cellulose nanocrystals (CNCs) have great potential as sustainable reinforcing materials for polymers, but there are a number of obstacles to commercialization that must first be overcome. High levels of water absorption, low thermal stabilities, poor miscibility with nonpolar polymers, and irreversible aggregation of the dried CNCs are among the greatest challenges to producing cellulose nanocrystal-polymer nanocomposites. A simple, scalable technique to modify sulfated cellulose nanocrystals (Na-CNCs) has been developed to address all of these issues. By using an ion exchange process to replace Na+ with imidazolium or phosphonium cations, the surface energy is altered, the thermal stability is increased, and the miscibility of dried CNCs with a nonpolar polymer (epoxy and polystyrene) is enhanced. Characterization of the resulting ion exchanged CNCs (IE-CNCs) using potentiometry, inverse gas chromatography, dynamic vapor sorption, and laser scanning confocal microscopy reveals that the IE-CNCs have lower surface energies, adsorb less water, and have thermal stabilities of up to 100 °C higher than those of prepared protonated cellulose nanocrystals (H-CNCs) and 40 °C higher than that of neutralized Na-CNC. Methyl(triphenyl)phosphonium exchanged cellulose nanocrystals (MePh3P-CNC) adsorbed 30% less water than Na-CNC, retained less water during desorption, and were used to prepare well-dispersed epoxy composites without the aid of a solvent and well-dispersed polystyrene nanocomposites using a melt blending technique at 195 °C. Predictions of dispersion quality and glass transition temperatures from molecular modeling experiments match experimental observations. These fiber-reinforced polymers can be used as lightweight composites in transportation, infrastructure, and renewable energy applications.
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Affiliation(s)
- Douglas M Fox
- Department of Chemistry, American University , Washington, D.C. 20016-8014, United States
| | - Rebeca S Rodriguez
- Department of Chemistry, American University , Washington, D.C. 20016-8014, United States
| | - Mackenzie N Devilbiss
- Department of Chemistry, American University , Washington, D.C. 20016-8014, United States
| | - Jeremiah Woodcock
- Materials Science and Engineering Division, Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899-8664, United States
| | - Chelsea S Davis
- Materials Science and Engineering Division, Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899-8664, United States
| | - Robert Sinko
- Department of Civil and Environmental Engineering and Department of Mechanical Engineering, Northwestern University , Evanston, Illinois 60208-3109, United States
| | - Sinan Keten
- Department of Civil and Environmental Engineering and Department of Mechanical Engineering, Northwestern University , Evanston, Illinois 60208-3109, United States
| | - Jeffrey W Gilman
- Materials Science and Engineering Division, Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899-8664, United States
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Siegrist MS, Swarts BM, Fox DM, Lim SA, Bertozzi CR. Illumination of growth, division and secretion by metabolic labeling of the bacterial cell surface. FEMS Microbiol Rev 2015; 39:184-202. [PMID: 25725012 DOI: 10.1093/femsre/fuu012] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The cell surface is the essential interface between a bacterium and its surroundings. Composed primarily of molecules that are not directly genetically encoded, this highly dynamic structure accommodates the basic cellular processes of growth and division as well as the transport of molecules between the cytoplasm and the extracellular milieu. In this review, we describe aspects of bacterial growth, division and secretion that have recently been uncovered by metabolic labeling of the cell envelope. Metabolite derivatives can be used to label a variety of macromolecules, from proteins to non-genetically-encoded glycans and lipids. The embedded metabolite enables precise tracking in time and space, and the versatility of newer chemoselective detection methods offers the ability to execute multiple experiments concurrently. In addition to reviewing the discoveries enabled by metabolic labeling of the bacterial cell envelope, we also discuss the potential of these techniques for translational applications. Finally, we offer some guidelines for implementing this emerging technology.
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Affiliation(s)
- M Sloan Siegrist
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Benjamin M Swarts
- Department of Chemistry, Central Michigan University, Mount Pleasant, MI 48859, USA
| | - Douglas M Fox
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Shion An Lim
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Carolyn R Bertozzi
- Department of Chemistry, University of California, Berkeley, CA 94720, USA Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA
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Fox DM, Novy M, Brown K, Zammarano M, Harris RH, Murariu M, McCarthy ED, Seppala JE, Gilman JW. Flame retarded poly(lactic acid) using POSS-modified cellulose. 2. Effects of intumescing flame retardant formulations on polymer degradation and composite physical properties. Polym Degrad Stab 2014. [DOI: 10.1016/j.polymdegradstab.2014.01.007] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
Ionic liquids represent a unique class of solvents that offer unprecedented versatility and tunability. Nature has developed a wide variety of materials based upon both proteins and polysaccharides. Many of these materials have unique properties that are a function not only of the material identity but are also largely dictated by processing conditions. Recent work has shown the potential of ionic liquids as solvents for the dissolution and processing of biopolymers. In this research we have expanded upon the limited data available to date using several biopolymers including: silk, chitin, collagen and elastin.
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Affiliation(s)
| | | | - J. Marshall Green
- U.S. Naval Academy Department of Chemistry, Annapolis, MD 21402, USA
| | - Paul A. Fylstra
- U.S. Naval Academy Department of Chemistry, Annapolis, MD 21402, USA
| | - Hugh C. De Long
- Air Force Office of Scientific Research, Chemistry and Life Sciences Directorate, Arlington, VA 22203, USA
| | - Paul C. Trulove
- U.S. Naval Academy Department of Chemistry, Annapolis, MD 21402, USA
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22
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Hartings MR, Benjamin N, Briere F, Briscione M, Choudary O, Fisher TL, Flynn L, Ghias E, Harper M, Khamis N, Koenigsknecht C, Lazor K, Moss S, Robbins E, Schultz S, Yaman S, Haverhals LM, Trulove PC, De Long HC, Miller AE, Fox DM. Concurrent zero-dimensional and one-dimensional biomineralization of gold from a solution of Au 3+ and bovine serum albumin. Sci Technol Adv Mater 2013; 14:065004. [PMID: 27877624 PMCID: PMC5090305 DOI: 10.1088/1468-6996/14/6/065004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 10/28/2013] [Indexed: 06/06/2023]
Abstract
A technique was developed for preparing a novel material that consists of gold nanoparticles trapped within a fiber of unfolded proteins. These fibers are made in an aqueous solution that contains HAuCl4 and the protein, bovine serum albumin (BSA). By changing the ratio of gold to BSA in solution, two different types of outcomes are observed. At lower gold to BSA ratios (30-120), a purple solution results after heating the mixture at 80 °C for 4 h. At higher gold to BSA ratios (130-170), a clear solution containing purple fibers results after heating the mixture at 80 °C for 4 h. UV-Vis spectroscopy and light scattering techniques show growth in nanocolloid size as gold to BSA ratio rises above 100. Data indicate that, for the higher gold to BSA ratios, the gold is sequestered within the solid material. The material mass, visible by eye, appears to be an aggregation of smaller individual fibers. Scanning electron microscopy and transmission electron microscopy indicate that these fibers are primarily one-dimensional aggregates, which can display some branching, and can be as narrow as 400 nm in size. The likely mechanism for the synthesis of the novel material is discussed.
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Affiliation(s)
- Matthew R Hartings
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Noah Benjamin
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Floriene Briere
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Maria Briscione
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Omar Choudary
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Tamra L Fisher
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Laura Flynn
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Elizabeth Ghias
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Michaela Harper
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Nader Khamis
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Catherine Koenigsknecht
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Klare Lazor
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Steven Moss
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Elaine Robbins
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Susan Schultz
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Samiye Yaman
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Luke M Haverhals
- Department of Chemistry, US Naval Academy, Anapolis, MD 21402, USA
| | - Paul C Trulove
- Department of Chemistry, US Naval Academy, Anapolis, MD 21402, USA
| | - Hugh C De Long
- Directorate of Math, Information, and Life Sciences, US Air Force Office of Scientific Research, Arlington, VA 22203, USA
| | - Abigail E Miller
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
| | - Douglas M Fox
- Department of Chemistry, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016, USA
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Fox DM, Lee J, Citro CJ, Novy M. Flame retarded poly(lactic acid) using POSS-modified cellulose. 1. Thermal and combustion properties of intumescing composites. Polym Degrad Stab 2013. [DOI: 10.1016/j.polymdegradstab.2012.11.016] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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McCarthy ED, Zammarano M, Fox DM, Nieuwendaal RC, Kim YS, Maupin PH, Trulove PC, Gilman JW. Formation of extended ionomeric network by bulk polymerization of l,d-lactide with layered-double-hydroxide. POLYMER 2013. [DOI: 10.1016/j.polymer.2012.11.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Swarts BM, Holsclaw CM, Jewett JC, Alber M, Fox DM, Siegrist MS, Leary JA, Kalscheuer R, Bertozzi CR. Probing the mycobacterial trehalome with bioorthogonal chemistry. J Am Chem Soc 2012; 134:16123-6. [PMID: 22978752 PMCID: PMC3466019 DOI: 10.1021/ja3062419] [Citation(s) in RCA: 132] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Mycobacteria, including the pathogen Mycobacterium
tuberculosis, use the non-mammalian disaccharide trehalose
as a precursor for
essential cell-wall glycolipids and other metabolites. Here we describe
a strategy for exploiting trehalose metabolic pathways to label glycolipids
in mycobacteria with azide-modified trehalose (TreAz) analogues. Subsequent
bioorthogonal ligation with alkyne-functionalized probes enabled detection
and visualization of cell-surface glycolipids. Characterization of
the metabolic fates of four TreAz analogues revealed unique labeling
routes that can be harnessed for pathway-targeted investigation of
the mycobacterial trehalome.
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Affiliation(s)
- Benjamin M Swarts
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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26
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Fox DM, Lee J, Zammarano M, Katsoulis D, Eldred DV, Haverhals LM, Trulove PC, De Long HC, Gilman JW. Char-forming behavior of nanofibrillated cellulose treated with glycidyl phenyl POSS. Carbohydr Polym 2012. [DOI: 10.1016/j.carbpol.2012.01.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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McDermott G, Fox DM, Epperly L, Wetzler M, Barron AE, Le Gros MA, Larabell CA. Visualizing and quantifying cell phenotype using soft X-ray tomography. Bioessays 2012; 34:320-7. [PMID: 22290620 DOI: 10.1002/bies.201100125] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Soft X-ray tomography (SXT) is an imaging technique capable of characterizing and quantifying the structural phenotype of cells. In particular, SXT is used to visualize the internal architecture of fully hydrated, intact eukaryotic and prokaryotic cells at high spatial resolution (50 nm or better). Image contrast in SXT is derived from the biochemical composition of the cell, and obtained without the need to use potentially damaging contrast-enhancing agents, such as heavy metals. The cells are simply cryopreserved prior to imaging, and are therefore imaged in a near-native state. As a complement to structural imaging by SXT, the same specimen can now be imaged by correlated cryo-light microscopy. By combining data from these two modalities specific molecules can be localized directly within the framework of a high-resolution, three-dimensional reconstruction of the cell. This combination of data types allows sophisticated analyses to be carried out on the impact of environmental and/or genetic factors on cell phenotypes.
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Affiliation(s)
- Gerry McDermott
- Department of Anatomy, University of California, San Francisco, CA, USA
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28
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Fox DM, Temburni S, Novy M, Flynn L, Zammarano M, Kim YS, Gilman JW, Davis RD. Thermal and Burning Properties of Poly(lactic acid) Composites Using Cellulose-Based Intumescing Flame Retardants. ACS Symposium Series 2012. [DOI: 10.1021/bk-2012-1118.ch016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Douglas M. Fox
- Chemistry Department, American University, Washington, DC 20016
- Fire Research Division, Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8665
- Polymers Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-1070
- Guest Researcher at NIST
| | - Srilatha Temburni
- Chemistry Department, American University, Washington, DC 20016
- Fire Research Division, Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8665
- Polymers Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-1070
- Guest Researcher at NIST
| | - Melissa Novy
- Chemistry Department, American University, Washington, DC 20016
- Fire Research Division, Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8665
- Polymers Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-1070
- Guest Researcher at NIST
| | - Laura Flynn
- Chemistry Department, American University, Washington, DC 20016
- Fire Research Division, Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8665
- Polymers Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-1070
- Guest Researcher at NIST
| | - Mauro Zammarano
- Chemistry Department, American University, Washington, DC 20016
- Fire Research Division, Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8665
- Polymers Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-1070
- Guest Researcher at NIST
| | - Yeon S. Kim
- Chemistry Department, American University, Washington, DC 20016
- Fire Research Division, Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8665
- Polymers Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-1070
- Guest Researcher at NIST
| | - Jeffrey W. Gilman
- Chemistry Department, American University, Washington, DC 20016
- Fire Research Division, Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8665
- Polymers Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-1070
- Guest Researcher at NIST
| | - Rick D. Davis
- Chemistry Department, American University, Washington, DC 20016
- Fire Research Division, Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8665
- Polymers Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-1070
- Guest Researcher at NIST
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Haverhals LM, Foley MP, Brown EK, Fox DM, De Long HC, Trulove PC. Natural Fiber Welding: Ionic Liquid Facilitated Biopolymer Mobilization and Reorganization. ACS Symposium Series 2012. [DOI: 10.1021/bk-2012-1117.ch006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Luke M. Haverhals
- Department of Chemistry, U. S. Naval Academy, Annapolis, Maryland 21402
- Department of Chemistry, American University, Washington, DC 20016
- Directorate of Mathematics and Life Sciences, Air Force Office of Scientific Research, Arlington, Virginia 22203
| | - Matthew P. Foley
- Department of Chemistry, U. S. Naval Academy, Annapolis, Maryland 21402
- Department of Chemistry, American University, Washington, DC 20016
- Directorate of Mathematics and Life Sciences, Air Force Office of Scientific Research, Arlington, Virginia 22203
| | - E. Kate Brown
- Department of Chemistry, U. S. Naval Academy, Annapolis, Maryland 21402
- Department of Chemistry, American University, Washington, DC 20016
- Directorate of Mathematics and Life Sciences, Air Force Office of Scientific Research, Arlington, Virginia 22203
| | - Douglas M. Fox
- Department of Chemistry, U. S. Naval Academy, Annapolis, Maryland 21402
- Department of Chemistry, American University, Washington, DC 20016
- Directorate of Mathematics and Life Sciences, Air Force Office of Scientific Research, Arlington, Virginia 22203
| | - Hugh C. De Long
- Department of Chemistry, U. S. Naval Academy, Annapolis, Maryland 21402
- Department of Chemistry, American University, Washington, DC 20016
- Directorate of Mathematics and Life Sciences, Air Force Office of Scientific Research, Arlington, Virginia 22203
| | - Paul C. Trulove
- Department of Chemistry, U. S. Naval Academy, Annapolis, Maryland 21402
- Department of Chemistry, American University, Washington, DC 20016
- Directorate of Mathematics and Life Sciences, Air Force Office of Scientific Research, Arlington, Virginia 22203
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Fox DM, Harris RH, Bellayer S, Gilman JW, Gelfer MY, Hsaio BS, Maupin PH, Trulove PC, De Long HC. The pillaring effect of the 1,2-dimethyl-3(benzyl ethyl iso-butyl POSS) imidazolium cation in polymer/montmorillonite nanocomposites. POLYMER 2011. [DOI: 10.1016/j.polymer.2011.09.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Zammarano M, Maupin PH, Sung LP, Gilman JW, McCarthy ED, Kim YS, Fox DM. Revealing the interface in polymer nanocomposites. ACS Nano 2011; 5:3391-3399. [PMID: 21410222 DOI: 10.1021/nn102951n] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The morphological characterization of polymer nanocomposites over multiple length scales is a fundamental challenge. Here, we report a technique for high-throughput monitoring of interface and dispersion in polymer nanocomposites based on Förster resonance energy transfer (FRET). Nanofibrillated cellulose (NFC), fluorescently labeled with 5-(4,6-dichlorotriazinyl)-aminofluorescein (FL) and dispersed into polyethylene (PE) doped with Coumarin 30 (C30), is used as a model system to assess the ability of FRET to evaluate the effect of processing on NFC dispersion in PE. The level of energy transfer and its standard deviation, measured by fluorescence spectroscopy and laser scanning confocal microscopy (LSCM), are exploited to monitor the extent of interface formation and composite homogeneity, respectively. FRET algorithms are used to generate color-coded images for a real-space observation of energy transfer efficiency. These images reveal interface formation at a nanoscale while probing a macroscale area that is large enough to be representative of the entire sample. The unique ability of this technique to simultaneously provide orientation/spatial information at a macroscale and nanoscale features, encoded in the FRET signal, provides a new powerful tool for structure-property-processing investigation in polymer nanocomposites.
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Affiliation(s)
- Mauro Zammarano
- Department of Chemistry, American University, Washington, DC 20016, USA.
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Fox DM. Evaluation of the efficiency of some sediment trapping methods after a Mediterranean forest fire. J Environ Manage 2011; 92:258-265. [PMID: 19931969 DOI: 10.1016/j.jenvman.2009.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Revised: 03/16/2009] [Accepted: 10/12/2009] [Indexed: 05/28/2023]
Abstract
Forest fires are common in Mediterranean environments and may become increasingly more frequent as the climate changes. Destruction of the forest cover and litter layer leads to greater overland flow and increased erosion rates. The greatest risk occurs during the first rainstorms following a major fire, so local authorities must act quickly to put erosion control methods in place in order to avoid excessive post-fire sediment loads in river channels. Deciding on which methods to use requires accurate knowledge of their impact on sediment load and an estimate of their cost efficiency. The objective of this study was to evaluate the efficiency of Log Debris Dams (LDDs) and a sedimentation basin for their effectiveness in trapping sediments. Paired sub-catchments were studied to quantify the amount of sediments trapped in stream channels by a series of LDDs and a sedimentation basin. Cost efficiency was evaluated for each of the measures as a function of the cost per unit volume of sediments trapped. In addition, grain size analyses were performed to characterise the nature of the sediments trapped. A third sediment trapping method, Log Erosion Barriers (LEBs) was evaluated more superficially than the first two and conclusions regarding this method are tentative. LDDs trapped a mean volume of 1.57 m³ per unit (median=1.28 m³); mean LDD height was 105.4 cm (std. dev.=21.9 cm), and mean height of trapped sediments was only 50.0 cm (std. dev.=22.9 cm), showing that the traps were only half filled. Sediment height was limited by the presence of gaps between logs or branches that allowed runoff to flow through. Comparison of the textural characteristics of slope and trapped sediments showed distinct sorting: particles greater than 20mm were not mobilised from the slopes during the study period, sediments in the medium to coarse sand size fractions were trapped preferentially by the LDDs, and sediments in the sedimentation basin were enriched by clay and silt sized (< 0.050 mm) particles as coarser sediments were trapped upstream by the LDDs. Cost efficiency of LDDs was estimated at about 143 € m⁻³ for the LDDs and 217 € m⁻³ for the sedimentation basin at the time of sampling. The LDDs are therefore a cost effective method of trapping sediments, but they can only be used when pine trees or straight-trunked trees are locally available. In this case, they should be combined with LEBs, which had a cost efficiency estimated at about 250 € m⁻³. Installation of the LEBs had not been optimised and they have the advantage of trapping sediments on the slopes where they can continue to play an ecological role, so this method can give better results with more care. Sedimentation basins can be emptied if necessary and are useful in areas where pine trees are not available and where the site can be secured.
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Affiliation(s)
- D M Fox
- UMR 6012 "ESPACE" CNRS, Department of Geography, University of Nice-Sophia Antipolis, BP 3209, 06204 Nice Cedex 3, France.
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Fox DM, Gilman JW, Morgan AB, Shields JR, Maupin PH, Lyon RE, De Long HC, Trulove PC. Flammability and Thermal Analysis Characterization of Imidazolium-Based Ionic Liquids. Ind Eng Chem Res 2008. [DOI: 10.1021/ie800665u] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Douglas M. Fox
- Department of Chemistry, American University, Washington, D.C. 20016, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, University of Dayton Research Institute, Dayton, Ohio 45469, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, Federal Aviation Administration, Atlantic City International Airport, New Jersey 08405, Air Force Office of Scientific Research, Arlington, Virginia 22203, and Chemistry Department, U.S. Naval Academy, Annapolis, Maryland
| | - Jeffrey W. Gilman
- Department of Chemistry, American University, Washington, D.C. 20016, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, University of Dayton Research Institute, Dayton, Ohio 45469, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, Federal Aviation Administration, Atlantic City International Airport, New Jersey 08405, Air Force Office of Scientific Research, Arlington, Virginia 22203, and Chemistry Department, U.S. Naval Academy, Annapolis, Maryland
| | - Alexander B. Morgan
- Department of Chemistry, American University, Washington, D.C. 20016, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, University of Dayton Research Institute, Dayton, Ohio 45469, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, Federal Aviation Administration, Atlantic City International Airport, New Jersey 08405, Air Force Office of Scientific Research, Arlington, Virginia 22203, and Chemistry Department, U.S. Naval Academy, Annapolis, Maryland
| | - John R. Shields
- Department of Chemistry, American University, Washington, D.C. 20016, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, University of Dayton Research Institute, Dayton, Ohio 45469, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, Federal Aviation Administration, Atlantic City International Airport, New Jersey 08405, Air Force Office of Scientific Research, Arlington, Virginia 22203, and Chemistry Department, U.S. Naval Academy, Annapolis, Maryland
| | - Paul H. Maupin
- Department of Chemistry, American University, Washington, D.C. 20016, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, University of Dayton Research Institute, Dayton, Ohio 45469, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, Federal Aviation Administration, Atlantic City International Airport, New Jersey 08405, Air Force Office of Scientific Research, Arlington, Virginia 22203, and Chemistry Department, U.S. Naval Academy, Annapolis, Maryland
| | - Richard E. Lyon
- Department of Chemistry, American University, Washington, D.C. 20016, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, University of Dayton Research Institute, Dayton, Ohio 45469, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, Federal Aviation Administration, Atlantic City International Airport, New Jersey 08405, Air Force Office of Scientific Research, Arlington, Virginia 22203, and Chemistry Department, U.S. Naval Academy, Annapolis, Maryland
| | - Hugh C. De Long
- Department of Chemistry, American University, Washington, D.C. 20016, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, University of Dayton Research Institute, Dayton, Ohio 45469, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, Federal Aviation Administration, Atlantic City International Airport, New Jersey 08405, Air Force Office of Scientific Research, Arlington, Virginia 22203, and Chemistry Department, U.S. Naval Academy, Annapolis, Maryland
| | - Paul C. Trulove
- Department of Chemistry, American University, Washington, D.C. 20016, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, University of Dayton Research Institute, Dayton, Ohio 45469, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, Federal Aviation Administration, Atlantic City International Airport, New Jersey 08405, Air Force Office of Scientific Research, Arlington, Virginia 22203, and Chemistry Department, U.S. Naval Academy, Annapolis, Maryland
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Fox DM, Maupin PH, Harris RH, Gilman JW, Eldred DV, Katsoulis D, Trulove PC, De Long HC. Use of a polyhedral oligomeric silsesquioxane (POSS)-imidazolium cation as an organic modifier for montmorillonite. Langmuir 2007; 23:7707-14. [PMID: 17555333 DOI: 10.1021/la0636863] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Recent studies on organically modified clays (OMCs) have reported enhanced thermal stabilities when using imidazolium-based surfactants over the typical ammonium-based surfactants. Other studies have shown that polyhedral oligomeric silsesquioxanes (POSS) also improve the thermal properties of composites containing these macromers. In an attempt to utilize the beneficial properties of both imidazolium surfactants and POSS macromers, a dual nanocomposite approach to prepare OMCs was used. In this study, the preparation of a new POSS-imidazolium surfactant and its use as an organic modifier for montmorillonite are reported. The purity, solubility, and thermal characteristics of the POSS-imidazolium chloride were evaluated. In addition, several OMCs were prepared by exchanging the Na+ with POSS imidazolium cations equivalent to 100%, 95%, 40%, 20%, and 5% of the cation exchange capacity of the clay. The subsequent OMCs were characterized using thermal analysis techniques (DSC, SDT, and TGA) as well as 29Si NMR to determine the POSS content in the clay interlayer both before and after thermal oxidation degradation. Results indicate the following: (1) the solvent choice changes the efficiency of the ion-exchange reaction of the clay; (2) self-assembled crystalline POSS domains are present in the clay interlayer; (3) the d-spacing of the exchanged clay is large (3.6 nm), accommodating a bilayer structure of the POSS-imidazolium; and (4) the prepared POSS-imidazolium exchanged clays exhibit higher thermal stabilities than any previously prepared imidazolium or ammonium exchanged montmorillonite.
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Affiliation(s)
- Douglas M Fox
- Chemistry Department, U.S. Naval Academy, Annapolis, Maryland 21402, USA.
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Abstract
The crystal structures and thermal behavior of the 1-(2-methoxyethyl)-2,3-dimethylimidazolium chloride and hexa-fluorophosphate salts are compared with the analogous 1-butyl-2,3-dimethylimidazolium salts to examine the influence of the ether oxygen on salt thermal properties for a typical constituent cation used in the preparation of ionic liquids.
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Affiliation(s)
- Wesley A Henderson
- U. S. Naval Academy, Department of Chemistry, 572 M Holloway Road, Annapolis, Maryland 21402, USA
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Dahl K, Sando GM, Fox DM, Sutto TE, Owrutsky JC. Vibrational spectroscopy and dynamics of small anions in ionic liquid solutions. J Chem Phys 2005; 123:084504. [PMID: 16164309 DOI: 10.1063/1.2000229] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Fourier-transform infrared (FTIR) and time-resolved IR spectroscopies have been used to study vibrational band positions, vibrational energy relaxation (VER) rates, and reorientation times of anions in several ionic liquid (IL) solutions. The ILs primarily investigated are based on the 1-butyl-2,3-dimethylimidazolium ([BM(2)IM]) cation with thiocyanate (NCS-), dicyanamide (N(CN)2-), and tetrafluoroborate (BF4-) anions. Spectroscopic studies are carried out near 2000 cm-1 for the C[Triple Bond]N stretching bands of NCS- and N(CN)2- as the IL anion as well as for NCS-, N(CN)2-, and azide (N3-) anions dissolved in [BM2IM][BF4]. The VER studies of N(CN)2- are reported for the first time. VER of N3-, NCS-, and N(CN)2- is measured in normal solvents, such as N-methylformamide, to compare with the IL solutions. The spectral shifts and VER rates of the anions in IL solution are quite similar to those in polar aprotic, conventional organic solvents, i.e., dimethylsulfoxide, and significantly different than those in methanol, in which there is hydrogen bonding. Similar studies were also carried out for the anions in another IL, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), in which the C2 hydrogen is present. The results for the anions are similar to those in the [BM2IM] containing ILs, in which the C2 hydrogen is methyl substituted. This suggests that substituting this hydrogen has, at most, a minor effect on the degree of hydrogen bonding in the anion-IL solvation interaction based on the infrared spectra and dynamics.
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Affiliation(s)
- Kevin Dahl
- Code 6111, U.S. Naval Research Laboratory, Washington, DC 20375-5342, USA
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Phillips DM, Drummy LF, Naik RR, Long HCD, Fox DM, Trulove PC, Mantz RA. Regenerated silk fiber wet spinning from an ionic liquid solution. ACTA ACUST UNITED AC 2005. [DOI: 10.1039/b510069k] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Fox DM, Bryan RB, Price AG. The role of soil surface crusting in desertification and strategies to reduce crusting. Environ Monit Assess 2004; 99:149-159. [PMID: 15641378 DOI: 10.1007/s10661-004-4015-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Soil crusting decreases infiltration, increases erosion, and impedes vegetation establishment, so reducing the impact of crusting is of major importance in combating desertification. Although surface crusting has been the subject of considerable research over the past 50 years or more, the practical management of soil crusts remains a challenge for many dryland communities. Crusting occurs in two steps, an initial aggregate breakdown period that occurs under rainfall and a subsequent hardening phase during drying. Several factors influence crust development, but the single most important one is soil aggregate stability. Strategies to reduce crusting can be based either on protecting the surface from raindrop impact or improving aggregate stability, or a combination of both. However, crust control is labor and/or capital intensive and must be thought out clearly in terms of the benefits to be achieved.
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Affiliation(s)
- D M Fox
- CNRS UMR 6012 Espace, Department of Geography, University of Nice Sophia-Antipolis, BP 3209, 06204 Nice cedex 3, France.
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Phillips DM, Drummy LF, Conrady DG, Fox DM, Naik RR, Stone MO, Trulove PC, De Long HC, Mantz RA. Dissolution and Regeneration of Bombyx mori Silk Fibroin Using Ionic Liquids. J Am Chem Soc 2004; 126:14350-1. [PMID: 15521743 DOI: 10.1021/ja046079f] [Citation(s) in RCA: 264] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this work, the suitability of imidazolium-based ionic liquid solvents is investigated for the dissolution and regeneration of silkworm (Bombyx mori) silk. Within an ionic liquid the anion plays a larger role in dictating the ultimate solubility of the silk. The dissolution of the silk in the ionic liquid is confirmed using wide-angle X-ray scattering. The dissolved silk is also processed into 100 mum-thick, two-dimensional films, and the structure of these films is examined. The rinse solvent, acetonitrile or methanol, has a profound impact on both the topography of the films and the secondary structure of the silk protein. The image depicts a silkworm cocoon dissolved in 1-butyl-3-methylimidazolium chloride and then regenerated as a film with birefringence.
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Affiliation(s)
- David M Phillips
- Materials & Manufacturing Directorate, Air Force Research Laboratory, 2941 Hobson Way, Wright-Patterson AFB, Ohio 45433, USA
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Thomas EH, Fox DM. AIDS on Long Island:the regional history of an epidemic 1981-1988. Long Island Hist J 2001; 1:93-111. [PMID: 11617622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
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Fox DM. The consequences of consensus: American health policy in the twentieth century. Milbank Q 2001; 64:76-99. [PMID: 11608481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023] Open
Abstract
For most of the twentieth century the central theme in the history of health policy in the United States was the elaboration and implementation of a consensus that health services should be organized in regional hierarchies. This consensus was based on shared beliefs about how medical advances were made and disseminated. Hierarchical regionalism became national health policy in several stages that culminated in the 1960s. Since the 1970s, however, the national policy of hierarchical regionalism has been eroded by the unexpected consequences of its success.
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Thomas EH, Fox DM. AIDS on Long Island: the regional history of an epidemic 1981-1988. Long Island Hist J 2001; 1:93-111. [PMID: 11617621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
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Abstract
Law has been an essential tool of public health practice for centuries. From the 19th century until recent decades, however, most histories of public health described, approvingly, the progression of the field from marginally useful policy, made by persons learned in law, to effective policy, made by persons employing the methods of biomedical and behavioral science. Historians have recently begun to change this standard account by documenting the centrality of law in the development of public health practice. The revised history of public health offers additional justification for the program of public health law reform proposed in this issue of the Journal by Gostin and by Moulton and Matthews, who describe the new program in public health law of the Centers for Disease Control and Prevention.
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Affiliation(s)
- D M Fox
- Milbank Memorial Fund, New York, NY 10022-1095, USA.
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Affiliation(s)
- D M Fox
- Milbank Memorial Fund, New York, NY, USA
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Affiliation(s)
- Douglas M. Fox
- Department of Chemistry, Michigan Technological University, 1400 Townsend Drive, Houghton, Michigan 49931-1295
| | - Leslie Leifer
- Department of Chemistry, Michigan Technological University, 1400 Townsend Drive, Houghton, Michigan 49931-1295
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Affiliation(s)
- D M Fox
- Milbank Memorial Fund, New York, NY 10022-1095, USA.
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