1
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Zhang Z, Chaudhuri K, Kaefer F, Malanoski AP, Page KA, Smieska LM, Pham JT, Ober CK. Controlling Anti-Penetration Performance by Post-Grafting of Fluorinated Alkyl Chains onto Polystyrene- block-poly(vinyl methyl siloxane). ACS Appl Mater Interfaces 2024; 16:19594-19604. [PMID: 38588386 DOI: 10.1021/acsami.4c01905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/10/2024]
Abstract
Polydimethylsiloxane (PDMS) has been widely used as a surface coating material, which has been reported to possess dynamic omniphobicity to a wide range of both polar and nonpolar solvents due to its high segmental flexibility and mobility. However, such high flexibility and mobility also enable penetration of small molecules into PDMS coatings, which alter the chemical and physical properties of the coating layers. To improve the anti-penetration properties of PDMS, a series of fluorinated alkyl segments are grafted to a diblock copolymer of polystyrene-block-poly(vinyl methyl siloxane) (PS-b-PVMS) using thiol-ene click reactions. This article reports the chemical characterization of these model fluorosilicone block copolymers and uses fluorescence measurements to investigate the dye penetration characteristics of polymer thin films. The introduction of longer fluorinated alkyl chains can gradually increase the anti-penetration properties as the time to reach the maximum fluorescence intensity (tpeak) gradually increases from 11 s of PS-b-PVMS to more than 1000 s of PS-b-P(n-C6F13-VMS). The improvement of anti-penetration properties is attributed to stronger inter-/intrachain interactions, phase segregation of ordered fluorinated side chains, and enhanced hydrophobicity caused by the grafting of fluorinated alkyl chains.
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Affiliation(s)
- Zhenglin Zhang
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
| | - Krishnaroop Chaudhuri
- Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Florian Kaefer
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
| | - Anthony P Malanoski
- United States Naval Research Laboratory, Center for Biomolecular Science and Engineering, Washington, District of Columbia 20375, United States
| | - Kirt A Page
- Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853, United States
- Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB, Dayton, Ohio 45433, United States
- UES Inc., Dayton, Ohio 45432, United States
| | - Louisa M Smieska
- Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853, United States
| | - Jonathan T Pham
- Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Christopher K Ober
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States
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2
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Jayamaha H, Ugras TJ, Page KA, Hanrath T, Robinson RD, Shepherd LM. Chiroptical Strain Sensors from Electrospun Cadmium Sulfide Quantum-Dot Fibers. ACS Appl Mater Interfaces 2024; 16:17757-17765. [PMID: 38535523 PMCID: PMC11009915 DOI: 10.1021/acsami.3c17623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 02/27/2024] [Accepted: 03/08/2024] [Indexed: 04/12/2024]
Abstract
Controllable synthesis of homochiral nano/micromaterials has been a constant challenge for fabricating various stimuli-responsive chiral sensors. To provide an avenue to this goal, we report electrospinning as a simple and economical strategy to form continuous homochiral microfibers with strain-sensitive chiroptical properties. First, electrospun homochiral microfibers from self-assembled cadmium sulfide (CdS) quantum dot magic-sized clusters (MSCs) are produced. Highly sensitive and reversible strain sensors are then fabricated by embedding these chiroptically active fibers into elastomeric films. The chiroptical response on stretching is indicated quantitatively as reversible changes in magnitude, spectral position (wavelength), and sign in circular dichroism (CD) and linear dichroism (LD) signals and qualitatively as a prominent change in the birefringence features under cross-polarizers. The observed periodic twisted helical fibrils at the surface of fibers provide insights into the origin of the fibers' chirality. The measurable shifts in CD and LD are caused by elastic deformations of these helical fibrillar structures of the fiber. To elucidate the origin of these chiroptical properties, we used field emission-electron microscopy (FE-SEM), atomic force microscopy (AFM), synchrotron X-ray analysis, polarized optical microscopy, as well as measurements to isolate the true CD, and contributions from photoelastic modulators (PEM) and LD. Our findings thus offer a promising strategy to fabricate chiroptical strain-sensing devices with multiple measurables/observables using electric-field-assisted spinning of homochiral nano/microfibers.
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Affiliation(s)
- Hansadi Jayamaha
- Department
of Human Centered Design, Cornell University, Ithaca, New York 14853, United States
| | - Thomas J. Ugras
- School
of Applied and Engineering Physics, Cornell
University, Ithaca, New York 14853, United States
| | - Kirt A. Page
- Materials
and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
- UES,
Inc., Beavercreek, Ohio 45432, United States
- Cornell
High Energy Synchrotron Source, Cornell
University, Ithaca, New York 14853, United States
| | - Tobias Hanrath
- Robert F.
Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, United States
| | - Richard D. Robinson
- Department
of Materials Science and Engineering, Cornell
University, Ithaca, New York 14853, United States
| | - Larissa M. Shepherd
- Department
of Human Centered Design, Cornell University, Ithaca, New York 14853, United States
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3
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Bhagwandin DD, Page KA, Tran LD, Yao Y, Reidell A, Muratore C, Fang Q, Ruditskiy A, Hampton CM, Kennedy WJ, Drummy LF, Zhong Y, Marks TJ, Facchetti A, Lou J, Koerner H, Baldwin LA, Glavin NR. Orientation and morphology control in acid-catalyzed covalent organic framework thin films. Nanoscale 2024. [PMID: 38572999 DOI: 10.1039/d3nr05798d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/05/2024]
Abstract
As thin films of semiconducting covalent organic frameworks (COFs) are demonstrating utility for ambipolar electronics, channel materials in organic electrochemical transistors (OECTs), and broadband photodetectors, control and modulation of their thin film properties is paramount. In this work, an interfacial growth technique is utilized to synthesize imine TAPB-PDA COF films at both the liquid-liquid interface as well as at the liquid-solid interface on a Si/SiO2 substrate. The concentration of acetic acid catalyst in the aqueous phase is shown to significantly influence the thin film morphology of the liquid-solid growth, with concentrations below 1 M resulting in no film nucleation, concentrations of 1-4 M enabling smooth film formation, and concentrations greater than 4 M resulting in films with a higher density of particulates on the surface. Importantly, while the films grown at the liquid-liquid interface are mixed-orientation, those grown directly at the liquid-solid interface on the Si/SiO2 surface have highly oriented COF layers aligned parallel to the substrate surface. Moreover, this liquid-solid growth process affords TAPB-PDA COF thin films with p-type charge transport having a transconductance of 10 μS at a gate voltage of -0.9 V in an OECT device structure.
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Affiliation(s)
- Dayanni D Bhagwandin
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA.
- UES, Inc., Beavercreek, Ohio 45432, USA
| | - Kirt A Page
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA.
- UES, Inc., Beavercreek, Ohio 45432, USA
- Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York 14853, USA
| | - Ly D Tran
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA.
- UES, Inc., Beavercreek, Ohio 45432, USA
| | - Yao Yao
- Department of Chemistry and the Materials Research Center, Northwestern University, Sheridan Road, Evanston, IL 60208, USA
| | - Alexander Reidell
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA.
- UES, Inc., Beavercreek, Ohio 45432, USA
| | - Christopher Muratore
- Department of Chemical and Materials Engineering, University of Dayton, Dayton, Ohio 45469, USA
| | - Qiyi Fang
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, USA
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Aleksey Ruditskiy
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA.
- UES, Inc., Beavercreek, Ohio 45432, USA
| | - Cheri M Hampton
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA.
- UES, Inc., Beavercreek, Ohio 45432, USA
| | - W Joshua Kennedy
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA.
| | - Lawrence F Drummy
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA.
| | - Yu Zhong
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Tobin J Marks
- Department of Chemistry and the Materials Research Center, Northwestern University, Sheridan Road, Evanston, IL 60208, USA
| | - Antonio Facchetti
- Department of Chemistry and the Materials Research Center, Northwestern University, Sheridan Road, Evanston, IL 60208, USA
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Jun Lou
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, USA
| | - Hilmar Koerner
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA.
| | - Luke A Baldwin
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA.
| | - Nicholas R Glavin
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA.
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4
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Bider-Canfield Z, Martinez MP, Wang X, Yu W, Bautista MP, Brookey J, Page KA, Buchanan TA, Xiang AH. Maternal obesity, gestational diabetes, breastfeeding and childhood overweight at age 2 years. Pediatr Obes 2017; 12:171-178. [PMID: 26956226 DOI: 10.1111/ijpo.12125] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 01/21/2016] [Accepted: 02/10/2016] [Indexed: 01/06/2023]
Abstract
BACKGROUND Maternal obesity, excessive gestational weight gain (EGWG), gestational diabetes mellitus (GDM) and breastfeeding are four important factors associated with childhood obesity. OBJECTIVES The objective of the study was to assess the interplay among these four factors and their independent contributions to childhood overweight in a cohort with standard clinical care. METHODS The cohort included 15 710 mother-offspring pairs delivered in 2011. Logistic regression was used to assess associations between maternal exposures and childhood overweight (body mass index >85th percentile) at age 2 years. RESULTS Mothers with pre-pregnancy obesity or overweight were more likely to have EGWG, GDM and less likely to breastfeed ≥6 months. Mothers with GDM had 40-49% lower EGWG rates and similar breastfeeding rates compared with mothers without GDM. Analysis adjusted for exposures and covariates revealed an adjusted odds ratio (95% confidence interval) associated with childhood overweight at age 2 years of 2.34 (2.09-2.62), 1.50 (1.34-1.68), 1.23 (1.12-1.35), 0.95 (0.83-1.10) and 0.76 (0.69-0.83) for maternal obesity, overweight, EGWG, GDM and breastfeeding ≥6 months vs. <6 months, respectively. CONCLUSIONS In this large clinical cohort, GDM was not associated with, but maternal pre-pregnancy obesity or overweight and EGWG were independently associated with an increased risk, and breastfeeding ≥6 months was associated with a decreased risk of childhood overweight at age 2 years.
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Affiliation(s)
- Z Bider-Canfield
- Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA
| | - M P Martinez
- Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA
| | - X Wang
- Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA
| | - W Yu
- Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA
| | - M P Bautista
- Consulting & Implementation, Kaiser Permanente Southern California, Pasadena, CA, USA
| | - J Brookey
- Quality and Risk, Kaiser Permanente Southern California, Pasadena, CA, USA
| | - K A Page
- Department of Medicine and Diabetes and Obesity Research Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - T A Buchanan
- Department of Medicine and Diabetes and Obesity Research Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - A H Xiang
- Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA
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5
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Frieberg BR, Page KA, Graybill JR, Walker ML, Stafford CM, Stafford GR, Soles CL. Mechanical Response of Thermally Annealed Nafion Thin Films. ACS Appl Mater Interfaces 2016; 8:33240-33249. [PMID: 27934151 DOI: 10.1021/acsami.6b12423] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Perfluorinated ionomers, in particular, Nafion, are a critical component in hydrogen fuel cells as the ion conducting binder within the catalyst layer in which it can be confined to thicknesses on the order of 10 nm or less. It is well reported that many physical properties, such as the Young's modulus, are thickness dependent when the film thickness is less than 100 nm. Here we utilize a cantilever bending methodology to quantify the swelling-induced stresses and relevant mechanical properties of Nafion films as a function of film thickness exposed to cyclic humidity. We observe a factor of 5 increase in the Young's modulus in films thinner than 50 nm and show how this increased stiffness translates to reduced swelling or hydration. The swelling stress was found to increase by a factor of 2 for films approximately 40 nm thick. We demonstrate that thermal annealing enhances the modulus at all film thicknesses and correlate these mechanical changes to chemical changes in the infrared absorption spectra.
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Affiliation(s)
- Bradley R Frieberg
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Kirt A Page
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Joshua R Graybill
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Marlon L Walker
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Christopher M Stafford
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Gery R Stafford
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - Christopher L Soles
- Materials Science and Engineering Division and ‡Materials Measurement Science Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
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6
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Nadermann NK, Davis EM, Page KA, Stafford CM, Chan EP. Using Indentation to Quantify Transport Properties of Nanophase-Segregated Polymer Thin Films. Adv Mater 2015; 27:4924-4930. [PMID: 26179206 DOI: 10.1002/adma.201501880] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 06/17/2015] [Indexed: 06/04/2023]
Abstract
Indentation of hydrated Nafion thin films reveals that both the in-plane diffusivity of water and the intrinsic permeability of the phase-segregated network decrease dramatically with decreasing film thickness. Using pore-network theory, this decrease in diffusivity is attributed to both an increase in ionic-domain heterogeneity and a reduction in ionic-domain connectivity upon confinement.
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Affiliation(s)
- Nichole K Nadermann
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Eric M Davis
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Kirt A Page
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Christopher M Stafford
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Edwin P Chan
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
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7
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Page KA, Shin JW, Eastman SA, Rowe BW, Kim S, Kusoglu A, Yager KG, Stafford GR. In Situ Method for Measuring the Mechanical Properties of Nafion Thin Films during Hydration Cycles. ACS Appl Mater Interfaces 2015; 7:17874-17883. [PMID: 26258630 DOI: 10.1021/acsami.5b04080] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Perfluorinated ionomers, in particular Nafion, are an essential component in hydrogen fuel cells, as both the proton exchange membrane and the binder within the catalyst layer. During normal operation of a hydrogen fuel cell, the ionomer will progressively swell and deswell in response to the changes in hydration, resulting in mechanical fatigue and ultimately failure over time. In this study, we have developed and implemented a cantilever bending technique in order to investigate the swelling-induced stresses in biaxially constrained Nafion thin films. When the deflection of a cantilever beam coated with a polymer film is monitored as it is exposed to varying humidity environments, the swelling induced stress-thickness product of the polymer film is measured. By combining the stress-thickness results with a measurement of the swelling strain as a function of humidity, as measured by quartz crystal microbalance (QCM) and X-ray reflectivity (XR), the swelling stress can be determined. An estimate of the Young's modulus of thin Nafion films as a function of relative humidity is obtained. The Young's modulus values indicate orientation of the ionic domains within the polymer films, which were confirmed by grazing incidence small-angle X-ray scattering (GISAXS). This study represents a measurement platform that can be expanded to incorporate novel ionomer systems and fuel cell components to mimic the stress state of a working hydrogen fuel cell.
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Affiliation(s)
- Kirt A Page
- †Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Jae Wook Shin
- †Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Scott A Eastman
- ‡United Technologies Research Center, East Hartford, Connecticut 06108, United States
| | - Brandon W Rowe
- †Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Sangcheol Kim
- †Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Ahmet Kusoglu
- §Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Kevin G Yager
- ∥Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Gery R Stafford
- †Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
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8
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Yager KG, Forrey C, Singh G, Satija SK, Page KA, Patton DL, Douglas JF, Jones RL, Karim A. Thermally-induced transition of lamellae orientation in block-copolymer films on 'neutral' nanoparticle-coated substrates. Soft Matter 2015; 11:5154-5167. [PMID: 26053660 DOI: 10.1039/c5sm00896d] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Block-copolymer orientation in thin films is controlled by the complex balance between interfacial free energies, including the inter-block segregation strength, the surface tensions of the blocks, and the relative substrate interactions. While block-copolymer lamellae orient horizontally when there is any preferential affinity of one block for the substrate, we recently described how nanoparticle-roughened substrates can be used to modify substrate interactions. We demonstrate how such 'neutral' substrates can be combined with control of annealing temperature to generate vertical lamellae orientations throughout a sample, at all thicknesses. We observe an orientational transition from vertical to horizontal lamellae upon heating, as confirmed using a combination of atomic force microscopy (AFM), neutron reflectometry (NR) and rotational small-angle neutron scattering (RSANS). Using molecular dynamics (MD) simulations, we identify substrate-localized distortions to the lamellar morphology as the physical basis of the novel behavior. In particular, under strong segregation conditions, bending of horizontal lamellae induce a large energetic cost. At higher temperatures, the energetic cost of conformal deformations of lamellae over the rough substrate is reduced, returning lamellae to the typical horizontal orientation. Thus, we find that both surface interactions and temperature play a crucial role in dictating block-copolymer lamellae orientation. Our combined experimental and simulation findings suggest that controlling substrate roughness should provide a useful and robust platform for controlling block-copolymer orientation in applications of these materials.
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Affiliation(s)
- Kevin G Yager
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, USA.
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9
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Abstract
Ion-exchange membranes are critical components of hydrogen fuel cells, where these ionomers can be confined to nanoscale thicknesses, altering the physical properties of these films from that of bulk membranes. Therefore, it is important to develop methods capable of measuring and elucidating the transport mechanisms under thin film confinement compared to bulk Nafion. In this study, water sorption and diffusion in a Nafion thin film were measured using time-resolved in situ polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). Interfacial mass transport limitations were confirmed to be minimal, while restricted water diffusion was observed, where the effective diffusion coefficient of water in the thin Nafion film was many orders of magnitude lower (between 4 and 5 orders of magnitude) than those reported for bulk membranes and was dependent on the initial hydration state of the Nafion. Furthermore, the response of the hydrophobic domains (Teflon backbone) to the swelling of the hydrophilic domains (ionic clusters) was shown to be orders of magnitude slower than that of bulk Nafion.
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Affiliation(s)
- Eric M. Davis
- Materials
Science and Engineering
Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Christopher M. Stafford
- Materials
Science and Engineering
Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Kirt A. Page
- Materials
Science and Engineering
Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
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10
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Page KA, Kusoglu A, Stafford CM, Kim S, Kline RJ, Weber AZ. Confinement-driven increase in ionomer thin-film modulus. Nano Lett 2014; 14:2299-2304. [PMID: 24773397 DOI: 10.1021/nl501233g] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Ion-conductive polymers, or ionomers, are critical materials for a wide range of electrochemical technologies. For optimizing the complex heterogeneous structures in which they occur, there is a need to elucidate the governing structure-property relationships, especially at nanoscale dimensions where interfacial interactions dominate the overall materials response due to confinement effects. It is widely acknowledged that polymer physical behavior can be drastically altered from the bulk when under confinement and the literature is replete with examples thereof. However, there is a deficit in the understanding of ionomers when confined to the nanoscale, although it is apparent from literature that confinement can influence ionomer properties. Herein we show that as one particular ionomer, Nafion, is confined to thin films, there is a drastic increase in the modulus over the bulk value, and we demonstrate that this stiffening can explain previously observed deviations in materials properties such as water transport and uptake upon confinement. Moreover, we provide insight into the underlying confinement-induced stiffening through the application of a simple theoretical framework based on self-consistent micromechanics. This framework can be applied to other polymer systems and assumes that as the polymer is confined the mechanical response becomes dominated by the modulus of individual polymer chains.
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Affiliation(s)
- Kirt A Page
- Materials Science and Engineering Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
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11
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Page KA, Rowe BW, Masser KA, Faraone A. The effect of water content on chain dynamics in nafion membranes measured by neutron spin echo and dielectric spectroscopy. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/polb.23457] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Kirt A. Page
- Division of Materials Science and Engineering; National Institute of Standards and Technology; Gaithersburg Maryland 20899
| | - Brandon W. Rowe
- Division of Materials Science and Engineering; National Institute of Standards and Technology; Gaithersburg Maryland 20899
| | - Kevin A. Masser
- Division of Materials Science and Engineering; National Institute of Standards and Technology; Gaithersburg Maryland 20899
| | - Antonio Faraone
- NIST Center for Neutron Research; Gaithersburg Maryland 20899
- Department of Materials Science and Engineering; University of Maryland; College Park Maryland 20742
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12
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Kim S, Dura JA, Page KA, Rowe BW, Yager KG, Lee HJ, Soles CL. Surface-Induced Nanostructure and Water Transport of Thin Proton-Conducting Polymer Films. Macromolecules 2013. [DOI: 10.1021/ma400750f] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Sangcheol Kim
- Materials Science and Engineering
Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Joseph A. Dura
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg,
Maryland 20899, United States
| | - Kirt A. Page
- Materials Science and Engineering
Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Brandon W. Rowe
- Materials Science and Engineering
Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Kevin G. Yager
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973,
United States
| | - Hae-Jeong Lee
- Materials Science and Engineering
Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Christopher L. Soles
- Materials Science and Engineering
Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
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13
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Eastman SA, Kim S, Page KA, Rowe BW, Kang S, DeCaluwe SC, Dura JA, Soles CL, Yager KG. Correction to Effect of Confinement on Structure, Water Solubility, and Water Transport in Nafion Thin Films. Macromolecules 2013. [DOI: 10.1021/ma302140d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [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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14
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Abstract
Small-angle neutron scattering and turbidity were used to probe nanoscale structure in bicontinuous microemulsions before and after polymerization. Difficulties in capturing nanoscale structure by polymerizing microemulsions have persisted with the use of thermal initiation. Bicontinuous microemulsion polymerization with a reactive surfactant monomer and cross-linker was done with only a 20% increase in repeat distance. This small increase represents better than an order of magnitude advance over previous attempts, exhibiting hundreds to thousands percent increases. Both the network gel and the precursor microemulsion were transparent and devoid of microphase separation.
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Affiliation(s)
- Kirt A. Page
- Materials
Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg,
Maryland 20899, United States
| | - Dustin England
- Coatings Research Institute,
School of Engineering Technology, Eastern Michigan University, Ypsilanti, Michigan 48197, United States
| | - John Texter
- Coatings Research Institute,
School of Engineering Technology, Eastern Michigan University, Ypsilanti, Michigan 48197, United States
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Eastman SA, Kim S, Page KA, Rowe BW, Kang S, Soles CL, Yager KG. Effect of Confinement on Structure, Water Solubility, and Water Transport in Nafion Thin Films. Macromolecules 2012. [DOI: 10.1021/ma301289v] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Scott A. Eastman
- Polymers
Division, National Institute of Standards and Technology, Gaithersburg, Maryland
20899, United States
| | - Sangcheol Kim
- Polymers
Division, National Institute of Standards and Technology, Gaithersburg, Maryland
20899, United States
| | - Kirt A. Page
- Polymers
Division, National Institute of Standards and Technology, Gaithersburg, Maryland
20899, United States
| | - Brandon W. Rowe
- Polymers
Division, National Institute of Standards and Technology, Gaithersburg, Maryland
20899, United States
| | - Shuhui Kang
- Polymers
Division, National Institute of Standards and Technology, Gaithersburg, Maryland
20899, United States
| | - Christopher L. Soles
- Polymers
Division, National Institute of Standards and Technology, Gaithersburg, Maryland
20899, United States
| | - Kevin G. Yager
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States
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Patton DL, Page KA, Hoff EA, Fasolka MJ, Beers KL. A robust and high-throughput measurement platform for monomer reactivity ratios from surface-initiated polymerization. Polym Chem 2012. [DOI: 10.1039/c2py20023f] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [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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Page KA, Rowe BW. An Overview of Polymer Electrolyte Membranes for Fuel Cell Applications. Polymers for Energy Storage and Delivery: Polyelectrolytes for Batteries and Fuel Cells 2012. [DOI: 10.1021/bk-2012-1096.ch009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [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)
- Kirt A. Page
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899
| | - Brandon W. Rowe
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899
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18
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Page KA, Park JK, Moore RB, Garcia Sakai V. Direct Analysis of the Ion-Hopping Process Associated with the α-Relaxation in Perfluorosulfonate Ionomers Using Quasielastic Neutron Scattering. Macromolecules 2009. [DOI: 10.1021/ma801533h] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [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)
- Kirt A. Page
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, and Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742
| | - Jong Keun Park
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, and Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742
| | - Robert B. Moore
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, and Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742
| | - Victoria Garcia Sakai
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, and Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742
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19
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Marszalek J, Pojman JA, Page KA. Neutron scattering study of the structural change induced by photopolymerization of AOT/D2O/dodecyl acrylate inverse microemulsions. Langmuir 2008; 24:13694-13700. [PMID: 18980349 DOI: 10.1021/la8022634] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Small-angle and ultrasmall-angle neutron scattering (SANS/USANS) measurements were used to determine the structural changes induced by photopolymerization of AOT/D2O/(dodecyl acrylate) inverse microemulsion systems. Scattering profiles were collected for the initial microemulsions and the films resulting from photopolymerization of the oil phase. The SANS data for the microemulsions were modeled as spherical, core-shell droplets. Upon polymerization, the clear mircoemulsions formed opaque films. From the SANS/USANS data of the films, it was apparent that this morphology was not preserved upon polymerization; however, it was clearly observed that the formulation of the microemulsion had a large impact on the structure within the films. The Guinier region in the USANS data (2.5 x 10(-5) A(-1) < or = Q < or = 5.3 x 10(-3) A(-1)) from the films indicates that very large structures are formed. Simultaneously, a well-defined peak (0.15 A(-1) < or = Q < or = 0.25 A(-1)) in the SANS data indicates that there are also much smaller structures formed. It is proposed that the low-Q scattering arises from aggregation of the nanometer-size water droplets in the microemulsion to form droplets large enough to scatter visible light, while the peak in the high-Q region results from bilayered structures formed by the surfactant.
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Affiliation(s)
- Jolanta Marszalek
- Department of Chemistry and Biochemistry, The University of Southern Mississippi, Hattiesburg, Mississippi 39406-0001, USA
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20
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Psurek T, Soles CL, Page KA, Cicerone MT, Douglas JF. Quantifying Changes in the High-Frequency Dynamics of Mixtures by Dielectric Spectroscopy. J Phys Chem B 2008; 112:15980-90. [DOI: 10.1021/jp8034314] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [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)
- Tatiana Psurek
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899
| | - Christopher L. Soles
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899
| | - Kirt A. Page
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899
| | - Marcus T. Cicerone
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899
| | - Jack F. Douglas
- Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899
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Somlai AP, Cozad RA, Page KA, Williams HR, Creed D, Hoyle CE. The photochemistry of some main chain liquid crystalline 4,4′-stilbene dicarboxylate polyesters. Photochem Photobiol Sci 2008; 7:578-87. [DOI: 10.1039/b719409a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [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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Patton DL, Page KA, Xu C, Genson KL, Fasolka MJ, Beers KL. Measurement of Reactivity Ratios in Surface-Initiated Radical Copolymerization†. Macromolecules 2007. [DOI: 10.1021/ma070944+] [Citation(s) in RCA: 17] [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: 11/28/2022]
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23
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Page KA, Jarrett W, Moore RB. Variable temperature19F solid-state NMR study of the effect of electrostatic interactions on thermally-stimulated molecular motions in perfluorosulfonate ionomers. ACTA ACUST UNITED AC 2007. [DOI: 10.1002/polb.21216] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Taylor EP, Landis FA, Page KA, Moore RB. Counterion dependent crystallization kinetics in blends of a perfluorosulfonate ionomer with poly(vinylidene fluoride). POLYMER 2006. [DOI: 10.1016/j.polymer.2006.08.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [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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25
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Page KA, Landis FA, Phillips AK, Moore RB. SAXS Analysis of the Thermal Relaxation of Anisotropic Morphologies in Oriented Nafion Membranes. Macromolecules 2006. [DOI: 10.1021/ma052359j] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kirt A. Page
- Department of Polymer Science, The University of Southern Mississippi, Hattiesburg, Mississippi 39406-0076, and Polymers Division, National Institute of Standards and Technology, 100 Bureau Dr., Gaithersburg, Maryland 20899
| | - Forrest A. Landis
- Department of Polymer Science, The University of Southern Mississippi, Hattiesburg, Mississippi 39406-0076, and Polymers Division, National Institute of Standards and Technology, 100 Bureau Dr., Gaithersburg, Maryland 20899
| | - Alan K. Phillips
- Department of Polymer Science, The University of Southern Mississippi, Hattiesburg, Mississippi 39406-0076, and Polymers Division, National Institute of Standards and Technology, 100 Bureau Dr., Gaithersburg, Maryland 20899
| | - Robert B. Moore
- Department of Polymer Science, The University of Southern Mississippi, Hattiesburg, Mississippi 39406-0076, and Polymers Division, National Institute of Standards and Technology, 100 Bureau Dr., Gaithersburg, Maryland 20899
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26
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Page KA, Cable KM, Moore RB. Molecular Origins of the Thermal Transitions and Dynamic Mechanical Relaxations in Perfluorosulfonate Ionomers. Macromolecules 2005. [DOI: 10.1021/ma0503559] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kirt A. Page
- Department of Polymer Science, The University of Southern Mississippi, Hattiesburg, Mississippi 39406-0001
| | - Kevin M. Cable
- Department of Polymer Science, The University of Southern Mississippi, Hattiesburg, Mississippi 39406-0001
| | - Robert B. Moore
- Department of Polymer Science, The University of Southern Mississippi, Hattiesburg, Mississippi 39406-0001
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Abstract
OBJECTIVE Adipocyte apoptosis plays an important role in adipose tissue homeostasis and can be altered under a variety of physiological and pathological conditions. This study was carried out to determine whether laser scanning cytometry (LSC) can be used to measure changes in apoptosis of adipocytes over time. DESIGN LSC was used to investigate adipocyte apoptosis induced by tumor necrosis factor-alpha (TNF-alpha), a cytokine that is associated with obesity and insulin resistance. LSC, a slide-based solid phase cytofluorometer, provides quantitative flow fluorescence data together with morphological information for apoptotic detection. Both 3T3-L1 cells and rat adipocytes from primary cell culture were incubated with 0 or 25 nM TNF-alpha for up to 24 h. Both the FITC-conjugated annexin V/propidium iodide assay and the TUNEL assay were used to distinguish cells with apoptotic characteristics from nonapoptotic cells. RESULTS Apoptosis did not increase over time in the absence of TNF-alpha for both 3T3-L1 cells and rat primary adipocytes. For both 3T3-L1 cells and rat primary adipocytes, a significant increase in the percentage of apoptotic cells was observed by 3-4 h incubation with TNF-alpha (P<0.05). By 24 h, more than 50% of cells incubated with TNF-alpha were apoptotic (P<0.001). This process was also associated with morphological changes typical of adipocytes undergoing apoptosis. By estimating the percentage of cell subpopulations after different times of incubation with TNF-alpha, we were able to develop grading parameters, based on the adipose apoptotic measurements. CONCLUSION With morphological information, LSC can be a useful tool to evaluate adipocyte apoptosis.
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Affiliation(s)
- J Lin
- Department of Animal and Dairy Science, University of Georgia, Athens, GA 30602-2771, USA
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Page KA, Schilling GD, Moore RB. Influence of ionic aggregation on the surface energies of crystallites in poly(butylene terephthalate) ionomers. POLYMER 2004. [DOI: 10.1016/j.polymer.2004.10.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Mason BR, Page KA, Fallon K. An analysis of movement and discomfort of the female breast during exercise and the effects of breast support in three cases. J Sci Med Sport 1999; 2:134-44. [PMID: 10476977 DOI: 10.1016/s1440-2440(99)80193-5] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.3] [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: 11/26/2022]
Abstract
Breast pain is common during exercise, occurring in up to 56% of subjects in some surveys. This pain is mainly associated with the movement of breast tissue. In an attempt to analyse this movement and the resulting pain, the movement of the female breast tissue was quantified in four conditions of breast support ("sports bra", "fashion bra", "crop top" and bare breasted) during four different activities (running, jogging, aerobics march and walking). These activities represented general patterns of exercise for adult females in Australian society. All three subjects were healthy, active, young women of varying breast size (12B, 14B & 14C) that were typical of young women. Two of the subjects had noted breast pain whilst exercising. The results showed that wearing external support for the breast tissue reduced absolute vertical movement and maximum downward deceleration force on the breast. Support also reduced perceived pain. When compared to other forms of breast support a "sports bra" (brassiere designed for breast support whilst exercising) provided superior support for the breast in relation to the amplitude of movement, deceleration forces on the breast, and perceived pain. The data indicates that adult females should wear appropriate breast support to reduce perceived breast discomfort or pain. Of the three garments examined in this study, the fitted sports bra provided superior support and pain reduction.
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Affiliation(s)
- B R Mason
- Australian Institute of Sport, Canberra
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Abstract
Exercise usually results in a large displacement of the breasts, often leading to breast pain. Although breast pain is a common concern of exercising females, little research has been conducted in the area of breast pain. It has been suggested that a cause of breast pain is excessive breast motion. As the female breast does not contain strong intrinsic structural support, this breast motion is difficult to reduce. It is suggested that the primary anatomical support for the breast is the Cooper's ligaments; however, their true functional properties are unknown. Because of the lack of internal breast support it has been suggested that the skin covering the breast may also act as a support structure for the breast, but this has not been quantified. In an attempt to reduce breast motion, external breast supports (brassieres) have been developed. This article discusses components of current sports brassieres with implications for future research required to improve brassiere design and performance.
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Affiliation(s)
- K A Page
- Department of Biomedical Science, University of Wollongong, New South Wales, Australia.
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Page KA, Liegler T, Feinberg MB. Use of a green fluorescent protein as a marker for human immunodeficiency virus type 1 infection. AIDS Res Hum Retroviruses 1997; 13:1077-81. [PMID: 9282811 DOI: 10.1089/aid.1997.13.1077] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [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: 02/05/2023] Open
Abstract
We constructed a recombinant human immunodeficiency virus type 1 (HIV-1) provirus called R7-GFP that expresses a modified form of a green fluorescent protein (GFP) from the jellyfish Aequorea victoria by substituting GFP-coding sequences for Nef-coding sequences. Alanine was substituted for serine at amino acid position 65 in the modified GFP, resulting in markedly increased fluorescence at an excitation wavelength of 488 nm as compared to wild-type GFP. The replication kinetics of R7-GFP were identical to that measured with an isogenic, nef-negative strain lacking GFP. Expression of GFP by replication-competent HIV-1 allowed simultaneous quantitation of viral infection and cell surface CD4 levels, revealing rapid and nearly complete CD4 downregulation on R7-GFP-infected PBMCs.
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Affiliation(s)
- K A Page
- Gladstone Institute of Virology and Immunology and the Department of Microbiology and Immunology, University of California, San Francisco 94141, USA
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Abstract
We have developed an in vitro model to study the influence that human immunodeficiency virus type 1 (HIV-1) may have on the ability of T cells to respond to antigenic challenge. We have examined consequences of HIV-1 gene expression on T-cell activation in antigen-dependent T cells that have stably integrated copies of replication-defective proviral HIV-1. Virus production by HIV-infected, antigen-dependent T cells was induced in response to antigenic stimulation and then decreased as infected cells returned to a state of quiescence. Contrary to the predictions of models proposing that Nef alters signal transduction pathways in T lymphocytes and thereby alters cellular activation, Nef expression in antigen-dependent T-cell clones did not influence their proliferative responses to low or intermediate concentrations of antigen and did not affect other measures of T-cell activation, such as induction of interleukin 2 receptor alpha-chain expression and cytokine production. In addition, we found no evidence for alteration of T-cell responsiveness to antigen by the gag, pol, vif, tat, or rev gene of HIV-1.
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Affiliation(s)
- K A Page
- Department of Microbiology and Immunology, University of California-San Francisco 94141-9100, USA.
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Veugelers PJ, Strathdee SA, Moss AR, Page KA, Tindall B, Schechter MT, Coutinho RA, van Griensven GJ. Is the human immunodeficiency virus-related Kaposi's sarcoma epidemic coming to an end? Insights from the Tricontinental Seroconverter Study. Epidemiology 1995; 6:382-6. [PMID: 7548345 DOI: 10.1097/00001648-199507000-00009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [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: 01/25/2023]
Abstract
A decline in the proportion of Kaposi's sarcoma among AIDS cases since the 1980s has been attributed to changes in sexual behavior among homosexual men and a decreasing exposure to a hypothesized Kaposi's sarcoma cofactor. Recent studies have shown that the incidence rate of Kaposi's sarcoma has remained relatively stable, which seems to argue against the hypothesis of a declining exposure to the putative cofactor. To examine this paradox, we evaluated the incidence of Kaposi's sarcoma, using Cox proportional hazard analyses, and performed a simulation to compare incidences of different AIDS outcomes among 407 homosexual men with documented dates of seroconversion. Our data show that men who seroconverted early in the epidemic did not progress faster to Kaposi's sarcoma than men who seroconverted more recently. A lower incidence rate of Kaposi's sarcoma would be expected among the latter group if exposure to the hypothesized cofactor is decreasing over time. The percentage of Kaposi's sarcoma among incident AIDS cases decreased over the years following seroconversion, but not over calendar time. This study demonstrates that the decline in the proportion of Kaposi's sarcoma among AIDS cases should not be interpreted as a decline in the incidence of Kaposi's sarcoma and that there is no evidence that a hypothesized Kaposi's sarcoma cofactor is declining over calendar time.
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Affiliation(s)
- P J Veugelers
- Municpal Health Service, Department of Public Health, Amsterdam, The Netherlands
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Miller MD, Warmerdam MT, Page KA, Feinberg MB, Greene WC. Expression of the human immunodeficiency virus type 1 (HIV-1) nef gene during HIV-1 production increases progeny particle infectivity independently of gp160 or viral entry. J Virol 1995; 69:579-84. [PMID: 7983759 PMCID: PMC188614 DOI: 10.1128/jvi.69.1.579-584.1995] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.1] [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: 01/28/2023] Open
Abstract
The nef gene product of human immunodeficiency virus type 1 (HIV-1) promotes more-rapid kinetics of viral replication in primary peripheral blood mononuclear cells. We have previously shown that these enhancing effects of Nef on HIV-1 replication reflect an increase in viral infectivity detectable both in limiting dilution assays and through a single-cycle infection of the HeLa-CD4-long terminal repeat-beta-galactosidase indicator cell line. We now demonstrate that nef-defective HIV-1 can be rescued to near wild-type levels of infectivity by coexpressing Nef in trans in the cell line producing the virus. This observation indicates that HIV-1 virions produced in the presence of Nef are intrinsically different. However, we show that the major viral structural proteins are quantitatively similar in purified viral preparations. We also demonstrate the functional equivalence of the gp120-gp41 envelope glycoprotein complexes of Nef+ and Nef- HIV-1 through an assay for viral entry. Finally, we show that env-defective Nef+ HIV-1 pseudotyped with an amphotropic envelope is also more infectious than similarly pseudotyped Nef- HIV-1. Thus, the production of HIV-1 in the presence of Nef results in viral particles that are more infectious, and this increased infectivity is manifested at a stage after viral entry but prior to or coincident with HIV-1 gene expression.
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Affiliation(s)
- M D Miller
- Gladstone Institute of Virology and Immunology, San Francisco, California 94141
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35
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Veugelers PJ, Page KA, Tindall B, Schechter MT, Moss AR, Winkelstein WW, Cooper DA, Craib KJ, Charlebois E, Coutinho RA. Determinants of HIV disease progression among homosexual men registered in the Tricontinental Seroconverter Study. Am J Epidemiol 1994; 140:747-58. [PMID: 7942776 DOI: 10.1093/oxfordjournals.aje.a117322] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.3] [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: 01/28/2023] Open
Abstract
Data on 403 homosexual/bisexual men with documented dates of human immunodeficiency virus (HIV) seroconversion were merged. All subjects originated from cohort studies that started between 1982 and 1984 in Amsterdam, The Netherlands; San Francisco, California; Sydney, Australia; and Vancouver, British Columbia, Canada. With respect to the four geographic locations, no statistically significant differences in progression time from HIV seroconversion to acquired immunodeficiency syndrome (AIDS) and death as well as in AIDS diagnoses patterns could be demonstrated. The median time from HIV seroconversion to AIDS was 8.3 years, that from HIV seroconversion to death was 8.9 years, and that from AIDS to death was 17 months. The authors evaluated HIV disease progression with respect to demographic, clinical, and behavioral cofactors. Younger age and use of prophylaxis against Pneumocystis carinii pneumonia were significantly related to slower progression from seroconversion to death. In addition, an association between slower progression and earlier dates of seroconversion was found. No relation of sexual behavior; history of sexually transmitted diseases; or use of alcohol, tobacco, and recreational drugs with rates of disease progression could be demonstrated.
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Affiliation(s)
- P J Veugelers
- Municipal Health Service, Department of Public Health, Amsterdam, The Netherlands
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Veugelers PJ, Strathdee SA, Tindall B, Page KA, Moss AR, Schechter MT, Montaner JS, van Griensven GJ. Increasing age is associated with faster progression to neoplasms but not opportunistic infections in HIV-infected homosexual men. AIDS 1994; 8:1471-5. [PMID: 7818819 DOI: 10.1097/00002030-199410000-00015] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [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: 01/27/2023]
Abstract
OBJECTIVE To characterize the associations of age and progression rates to AIDS-defining neoplasms and opportunistic infections (OI) in HIV-infected homosexual men. METHODS Data from 407 homosexual men with documented dates of HIV seroconversion participating in cohort studies from four geographic locations were merged. Kaplan-Meier and Cox proportional hazards analyses were conducted with respect to the association of age with time from seroconversion to the first AIDS-defining neoplasm and OI. RESULTS Among the 407 participants, 139 (34%) were diagnosed with AIDS; 45 (11%) with neoplasms and 90 (22%) with OI. Older age at seroconversion was significantly associated with faster progression to neoplasms, but not to OI. For each 10-year increase in age the risk for neoplasms increased 1.65-fold [95% confidence interval (CI), 1.12-2.43], after adjustment for clinical treatments. For OI this risk estimate was 0.98 (95% CI, 0.72-1.34). CONCLUSIONS Increasing age is associated with faster progression to AIDS-defining neoplasms, but not with progression to OI. This has not been previously reported and may explain conflicting results in other studies among homosexual men that considered AIDS as a single entity. Our findings suggest that age and AIDS manifestations should be considered, particularly in the context of natural history studies, clinical trials and mathematical modelling.
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Affiliation(s)
- P J Veugelers
- Municipal Health Service, Department of Public Health, Amsterdam, The Netherlands
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Page KA, Wayson K, Steinberg GK, Adler JR. Stereotaxic radiosurgical ablation: an alternative treatment for recurrent and multifocal hemangioblastomas. A report of four cases. Surg Neurol 1993; 40:424-8. [PMID: 8211662 DOI: 10.1016/0090-3019(93)90225-p] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Craniotomy and resection is usually a safe and effective treatment for hemangioblastoma. However, since the surgical removal of recurrent and multifocal tumors can be associated with greater risks, stereotaxic radiosurgery was used to ablate hemangioblastomas in four patients with von Hippel-Lindau disease. In two of these cases a symptomatic lesion was surgically resected just prior to radiosurgery. The 11 radiosurgically treated tumors (four patients) were spherical and varied in diameter from 0.75 to 2.0 cm with a mean of 1.25 cm. Dose ranged from 30 to 75 Gy with a mean of 35 Gy. After a mean clinical and radiologic follow-up of greater than 1 1/2 years, tumor size and/or cyst formation was controlled in all cases. Nevertheless, it was necessary to temporarily shunt a tumor cyst in one patient. In another case, aggressive treatment resulted in symptomatic radiation necrosis. Despite such potential problems we believe that radiosurgical tumor ablation is a reasonable alternative to craniotomy and/or radiation therapy in poor risk patients. This report is believed to be the first published description of the use of radiosurgery in the treatment of hemangioblastoma.
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Affiliation(s)
- K A Page
- Department of Neurosurgery, Stanford University School of Medicine, California
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Veugelers PJ, Schechter MT, Tindall B, Moss AR, Page KA, Craib KJ, Cooper DA, Coutinho RA, Charlebois E, Winkelstein W. Differences in time from HIV seroconversion to CD4+ lymphocyte end-points and AIDS in cohorts of homosexual men. AIDS 1993; 7:1325-9. [PMID: 7903540 DOI: 10.1097/00002030-199310000-00004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [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: 01/27/2023]
Abstract
OBJECTIVE To evaluate the decline in CD4+ counts in relation to the incidence of AIDS in different cohorts of homosexual men and to quantify possible consequences of laboratory variation in CD4+ measurement. METHODS Our study includes 403 men with well documented dates of HIV seroconversion originating from five cohort studies among homosexual men. Differences in time from HIV seroconversion to the first CD4+ count dropping < 500 or 200 x 10(6)/l and to AIDS were evaluated using Kaplan-Meier survival analyses. RESULTS We found considerable differences between cohorts in CD4+ depletion, but not in the incidence of AIDS (1987 definition). CONCLUSIONS Variation in CD4+ depletion appears to be mainly the result of laboratory differences. Policy recommendations on a basis of CD4+ counts probably requires a calibration of measurement. The 1993 AIDS case definition leads to a site-specific shortening of the incubation time, which complicates the study of the natural history of HIV infection and of trends in the AIDS epidemic.
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Affiliation(s)
- P J Veugelers
- Municipal Health Service, Department of Public Health, Amsterdam, The Netherlands
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Schulz TF, Reeves JD, Hoad JG, Tailor C, Stephens P, Clements G, Ortlepp S, Page KA, Moore JP, Weiss RA. Effect of mutations in the V3 loop of HIV-1 gp120 on infectivity and susceptibility to proteolytic cleavage. AIDS Res Hum Retroviruses 1993; 9:159-66. [PMID: 8457383 DOI: 10.1089/aid.1993.9.159] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [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: 01/30/2023] Open
Abstract
It has been suggested that the V3 domain of human immunodeficiency virus type 1 (HIV-1) isolates has to interact with a cell-surface-associated or endosomal proteinase during virus entry into susceptible cells. To investigate this hypothesis, we examined the effect of several mutations in the V3 loop on its susceptibility to proteolytic cleavage by thrombin and cathepsin E and compared it with the effect of these mutations on viral infectivity. The data obtained indicate that, if an interaction between the V3 loop and a proteinase is indeed crucial for viral entry, the substrate requirements for such a proteinase(s) would have to be very complex. In particular, it seems unlikely that a single enzyme with a unique specificity would be able to interact with all of the different HIV-1 and HIV-2/SIV strains isolated so far. Therefore, one would have to postulate the involvement of several cellular proteinases, or proteases with multiple specificities, in V3-based viral tropism.
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Affiliation(s)
- T F Schulz
- Chester Beatty Laboratories, Institute of Cancer Research, London, UK
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40
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Abstract
This report describes the neuropathological findings in a 32 year old woman with acute myelogenous leukemia (AML) and central nervous system (CNS) involvement, who received a total of 48 mg of methotrexate (MTX) intended to be delivered to the ventricle. At autopsy, the tip of the infusion catheter was found to have been inadvertently placed in the left basal ganglia. The delivery of the MTX at that site caused white matter lesions characteristic of those previously reported in MTX encephalopathy following diverse modes of administration. This case is unusual in that there was the direct infusion of MTX into cerebral parenchyma, circumventing both the blood:brain and cerebrospinal fluid:brain barriers. Axonal abnormalities were widespread in the MTX-infused tissue, frequently but not always accompanied by myelin loss. Since radiation therapy had not been employed, this case permitted the assessment of pathologic changes largely attributable to MTX.
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Affiliation(s)
- K A Page
- Department of Pathology (Neuropathology), Stanford University Medical Center, CA 94305
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Abstract
The third hypervariable (V3) domain of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein has been proposed to play an important role in mediating viral entry. Antibodies to the V3 domain block HIV-1 infection but not virus binding to CD4. At the center of the V3 domain is a relatively conserved sequence of amino acids, GPGRA. It has previously been shown that mutation of some of these amino acids reduced the ability of gp160 expressed on the surface of cells to induce fusion with CD4-bearing cells. In order to analyze the role of V3 domain sequences in mediating HIV entry, we introduced several amino acid substitution mutations in the GPGRA sequence of gp160 derived from HIV-1 strain HXB2 and in the analogous sequence of strain SF33, GPGKV. Virus was generated by cotransfecting the env constructs and a selectable env-negative HIV vector, HIV-gpt. When complemented with a retrovirus env gene, infectious virus capable of a single round of replication was produced. The viral particles produced were analyzed biochemically for core and envelope proteins and for infectious titer. The transfected envs were also analyzed for ability to bind to CD4 and mediate cell fusion. Several of the amino acid substitutions resulted in moderate to severe decreases in virus infectivity and fusion activity. Envelope glycoprotein assembly onto particles and CD4 binding were not affected. These results provide evidence that V3 sequences are involved in mediating the fusion step of HIV-1 entry.
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Affiliation(s)
- K A Page
- Department of Microbiology and Immunology, University of California, San Francisco 94143-0414
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Jasin M, Page KA, Littman DR. Glycosylphosphatidylinositol-anchored CD4/Thy-1 chimeric molecules serve as human immunodeficiency virus receptors in human, but not mouse, cells and are modulated by gangliosides. J Virol 1991; 65:440-4. [PMID: 1670644 PMCID: PMC240534 DOI: 10.1128/jvi.65.1.440-444.1991] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Human and mouse cell lines that expressed a CD4/Thy-1 fusion protein on the cell surface were constructed and tested for the capacity to be infected with human immunodeficiency virus. The human cell lines, in contrast to the mouse line, were infectable. The CD4/Thy-1 fusion, which is anchored to the membrane by a glycosylphosphatidylinositol tail rather than a peptide linkage, can therefore serve as a human immunodeficiency virus receptor. In addition, this molecule, like CD4, is down-modulated in its cell surface expression by exogenous gangliosides.
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Affiliation(s)
- M Jasin
- Beckman Center, Department of Biochemistry, Stanford Medical Center, California 94305
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Abstract
Several epidemiologic and clinical studies suggest that patients coinfected with human immunodeficiency virus (HIV), the primary etiologic agent in AIDS, and other viruses, such as cytomegalovirus or human T-cell leukemia virus (HTLV), have a more severe clinical course than those infected with HIV alone. Cells infected with two viruses can, in some cases, give rise to phenotypically mixed virions with altered or broadened cell tropism and could therefore account for some of these findings. Such pseudotypes could alter the course of disease by infecting more tissues than are normally infected by HIV. We show here that HIV type 1 (HIV-1) efficiently incorporates the HTLV type I (HTLV-I) envelope glycoprotein and that both HIV-1 and HTLV-II accept other widely divergent envelope glycoproteins to form infectious pseudotype viruses whose cellular tropisms and relative abilities to be transmitted by cell-free virions or by cell contact are determined by the heterologous envelope. We also show that the mechanism by which virions incorporate heterologous envelope glycoproteins is independent of the presence of the homologous glycoprotein or heterologous gag proteins. These results may have important implications for the mechanism of HIV pathogenesis.
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Affiliation(s)
- N R Landau
- Department of Microbiology and Immunology, University of California, San Francisco
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Abstract
We constructed a recombinant human immunodeficiency virus (HIV) vector to facilitate studies of virus infectivity. A drug resistance gene was inserted into a gp160- HIV proviral genome such that it could be packaged into HIV virions. The HIV genome was rendered replication defective by deletion of sequences encoding gp160 and insertion of a gpt gene with a simian virus 40 promoter at the deletion site. Cotransfection of the envelope-deficient genome with a gp160 expression vector resulted in packaging of the defective HIV-gpt genome into infectious virions. The drug resistance gene was transmitted and expressed upon infection of susceptible cells, enabling their selection in mycophenolic acid. This system provides a quantitative measure of HIV infection, since each successful infection event leads to the growth of a drug-resistant colony. The HIV-gpt virus produced was tropic for CD4+ human cells and was blocked by soluble CD4. In the absence of gp160, noninfectious HIV particles were efficiently produced by cells transfected with the HIV-gpt genome. These particles packaged HIV genomic RNA and migrated to the same density as gp160-containing virions in a sucrose gradient. This demonstrates that HIV virion formation is not dependent on the presence of a viral envelope glycoprotein. Expression of a murine leukemia virus amphotropic envelope gene in cells transfected with HIV-gpt resulted in the production of virus capable of infecting both human and murine cells. These results indicate that HIV can incorporate envelope glycoproteins other than gp160 onto particles and that this can lead to altered host range. Like HIV type 1 and vesicular stomatitis virus(HIV) pseudotypes, gp-160+ HIV-gpt did not infect murine NIH 3T3 cells that bear human CD4, confirming that these cells are blocked at an early stage of HIV infection.
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Affiliation(s)
- K A Page
- Department of Microbiology and Immunology, University of California, San Francisco 94143-0414
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Abstract
This article provides a summary of the attempts of various researchers to establish predictive relationships between certain perinatal risk factors and the neurologic outcome in the very low birth weight population and outlines some of the methodological problems inherent in developmental research. Information gathered through current assessment methods has limited prognostic value and should be used judiciously in decision making about diagnosis or intervention.
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