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Botman F, Brown PR, van Meggelen M, Sonke GS, Buiting HM. Balancing proximity and distance in oncology during COVID-19 times and beyond. Eur J Oncol Nurs 2023; 66:102379. [PMID: 37517340 DOI: 10.1016/j.ejon.2023.102379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 06/13/2023] [Accepted: 06/29/2023] [Indexed: 08/01/2023]
Affiliation(s)
- Femke Botman
- University of Amsterdam, Department of Anthropology, Amsterdam, the Netherlands; Amsterdam UMC, Department of Medical Oncology, Amsterdam, the Netherlands
| | - Patrick R Brown
- University of Amsterdam, Department of Sociology, Amsterdam, the Netherlands
| | | | - Gabe S Sonke
- Antoni van Leeuwenhoek, Department of Medical Oncology, Amsterdam, the Netherlands; University of Amsterdam, Amsterdam, the Netherlands
| | - Hilde M Buiting
- Antoni van Leeuwenhoek, Department of Medical Oncology, Amsterdam, the Netherlands; University of Amsterdam, Amsterdam, the Netherlands; O2PZ, Platform of Palliative care, Amsterdam, the Netherlands.
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2
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Brown PR, Sadiq O, Weick A, Lenhart A, Elbatta M, Fernandez C, Kutait A, Pompa R, Jafri SM. Acute Kidney Injury in Patients Undergoing Chronic Hepatitis C Virus Treatment With Ledipasvir/Sofosbuvir. Hepatol Commun 2018; 2:1172-1178. [PMID: 30288472 PMCID: PMC6167069 DOI: 10.1002/hep4.1243] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 07/13/2018] [Indexed: 12/23/2022] Open
Abstract
Ledipasvir-sofosbuvir, a once-a-day, oral combination pill, was approved in 2014 for the treatment of chronic hepatitis C infection. Initial trials did not comment on nephrotoxicity; however, recent data suggest a risk of acute kidney injury (AKI) with the use of the medication. We assessed the rates of AKI in patients undergoing ledipasvir-sofosbuvir in a large, urban tertiary care center. This single-center retrospective observation study included all patients undergoing therapy from October 1, 2014, to October 1, 2015. Rates of AKI, defined by more than a 0.3 mg/dL increase in serum creatinine level, were calculated. Patients were followed 12 weeks after therapy to assess for sustained viral response as well as to assess for improvement of AKI after completion of therapy, defined by less than 0.2 mg/dL above baseline serum creatinine. In total, 197 patients were included in the final analysis who had completed ledipasvir-sofosbuvir therapy and completed laboratory values. Among the patients treated, 38 (19%) had AKI during therapy. An additional 4 (2%) had AKI at the end of therapy. Of the 38 patients who experienced AKI, 20 (53%) had improvement in serum creatinine to less than 0.2 mg/dL above their baseline. When comparing for chronic kidney disease (CKD) stage, those with CKD I or II experienced AKI 17% of the time compared with 47% of the time in CKD III or worse (P = 0.005). Conclusion: AKI was seen in nearly one-fifth of our patients, and patients with CKD stage III or worse are at increased risk. Although ledipasvir-sofosbuvir is generally safe in the general population, close monitoring of renal function is recommended.
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Affiliation(s)
- Patrick R Brown
- Department of Internal Medicine Henry Ford Hospital Detroit MI
| | - Omar Sadiq
- Department of Internal Medicine Henry Ford Hospital Detroit MI
| | - Alexander Weick
- Department of Gastroenterology Henry Ford Hospital Detroit MI
| | | | | | | | - Anas Kutait
- Department of Gastroenterology Henry Ford Hospital Detroit MI
| | - Robert Pompa
- Department of Gastroenterology Henry Ford Hospital Detroit MI
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3
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Hashem F, Calnan MW, Brown PR. Decision making in NICE single technological appraisals: How does NICE incorporate patient perspectives? Health Expect 2017; 21:128-137. [PMID: 28686809 PMCID: PMC5750768 DOI: 10.1111/hex.12594] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/08/2017] [Indexed: 12/01/2022] Open
Abstract
CONTEXT The National Institute for Health and Care Excellence (NICE) has an explicit mandate to include patient and public involvement in the appraisal of medicines to be available for funding on the NHS. NICE involves an appraisal committee who are required to take on board experiential evidence from patient experts alongside population-based evidence on clinical and cost-effectiveness when making a decision whether to fund a drug. OBJECTIVE This paper considers how NICE Single Technological Appraisal (STA) committees attempt to incorporate the views of patients in making decisions about funding medicines on the NHS. METHODS A prospective design was employed to follow three pharmaceutical products involving three different appraisal committees. Three data collection methods were used: analysis of documentary evidence sent by NICE, non-participant unstructured observations of the open and closed sessions of meetings and qualitative interviews. SETTINGS AND PARTICIPANTS Unstructured non-participant observations were carried out at nine STA meetings, and 41 semi-structured interviews were undertaken with committee members from NICE's STA committees, patient experts, analysts from NICE's project team and drug manufacturers. RESULTS Our analysis showed how the committees displayed a preference for an ideal-type of patient representative, disagreement among the committee when weighing-up patient statements in the STA process and more pre-preparation support for patient involvement. CONCLUSIONS Although NICE has attempted to adopt an approach flexible to patients and carers through formal decision-making arrangements that incorporate patient views, nonetheless, the processes of the STAs can in fact undermine the very evidence collected from patient representatives.
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Brown PR, Calnan MW. Chains of (dis)trust: exploring the underpinnings of knowledge-sharing and quality care across mental health services. Sociol Health Illn 2016; 38:286-305. [PMID: 26614364 DOI: 10.1111/1467-9566.12369] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [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: 06/05/2023]
Abstract
Quality and safety in healthcare settings are underpinned by organisational cultures, which facilitate or impede the refinement, sharing and application of knowledge. Avoiding the use of the term culture as a residual category, we focus specifically on describing chains of (dis)trust, analysing their development across relatively low-trust service contexts and their impact upon knowledge-sharing and caregiving. Drawing upon data from in-depth interviews with service users, healthcare professionals, service managers and other stakeholders across three mental healthcare (psychosis) teams in southern England, we identify micro-mechanisms that explain how (dis)trust within one intra-organisational relationship impacts upon other relationships. Experiences and inferences of vulnerability, knowledge, uncertainty, interests and time, among actors who are both trustees and trusters across different relationships, are pertinent to such analyses. This more micro-level understanding facilitates detailed conceptualisations of trust chains as meso-level tendencies that contribute to wider vicious or virtuous cycles of organisational (dis)trust. We explore how knowledge-sharing and caregiving are vitally interwoven within these chains of trust or distrust, enhancing and/or inhibiting the instrumental and communicative aspects of quality healthcare as a result.
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Affiliation(s)
- Patrick R Brown
- Department of Sociology and Centre for Social Science and Global Health, University of Amsterdam, The Netherlands
| | - Michael W Calnan
- School of Social Policy, Sociology and Social Research, University of Kent
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5
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Hussein D, Starr A, Heikal L, McNeill E, Channon KM, Brown PR, Sutton BJ, McDonnell JM, Nandi M. Validating the GTP-cyclohydrolase 1-feedback regulatory complex as a therapeutic target using biophysical and in vivo approaches. Br J Pharmacol 2015; 172:4146-57. [PMID: 26014146 PMCID: PMC4543619 DOI: 10.1111/bph.13202] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [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: 12/08/2014] [Revised: 05/12/2015] [Accepted: 05/13/2015] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND AND PURPOSE 6R-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4 ) is an essential cofactor for nitric oxide biosynthesis. Substantial clinical evidence indicates that intravenous BH4 restores vascular function in patients. Unfortunately, oral BH4 has limited efficacy. Therefore, orally bioavailable pharmacological activators of endogenous BH4 biosynthesis hold significant therapeutic potential. GTP-cyclohydrolase 1 (GCH1), the rate limiting enzyme in BH4 synthesis, forms a protein complex with GCH1 feedback regulatory protein (GFRP). This complex is subject to allosteric feed-forward activation by L-phenylalanine (L-phe). We investigated the effects of L-phe on the biophysical interactions of GCH1 and GFRP and its potential to alter BH4 levels in vivo. EXPERIMENTAL APPROACH Detailed characterization of GCH1-GFRP protein-protein interactions were performed using surface plasmon resonance (SPR) with or without L-phe. Effects on systemic and vascular BH4 biosynthesis in vivo were investigated following L-phe treatment (100 mg·kg(-1) , p.o.). KEY RESULTS GCH1 and GFRP proteins interacted in the absence of known ligands or substrate but the presence of L-phe doubled maximal binding and enhanced binding affinity eightfold. Furthermore, the complex displayed very slow association and dissociation rates. In vivo, L-phe challenge induced a sustained elevation of aortic BH4 , an effect absent in GCH1(fl/fl)-Tie2Cre mice. CONCLUSIONS AND IMPLICATIONS Biophysical data indicate that GCH1 and GFRP are constitutively bound. In vivo, data demonstrated that L-phe elevated vascular BH4 in an endothelial GCH1 dependent manner. Pharmacological agents which mimic the allosteric effects of L-phe on the GCH1-GFRP complex have the potential to elevate endothelial BH4 biosynthesis for numerous cardiovascular disorders.
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Affiliation(s)
- D Hussein
- Institute of Pharmaceutical Science, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
| | - A Starr
- Institute of Pharmaceutical Science, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
| | - L Heikal
- Institute of Pharmaceutical Science, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
| | - E McNeill
- British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe HospitalOxford, UK
| | - K M Channon
- British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe HospitalOxford, UK
| | - P R Brown
- The Randall Division of Cell and Molecular Biophysics, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
| | - B J Sutton
- The Randall Division of Cell and Molecular Biophysics, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
| | - J M McDonnell
- The Randall Division of Cell and Molecular Biophysics, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
| | - M Nandi
- Institute of Pharmaceutical Science, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
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6
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Grinolds DDW, Brown PR, Harris DK, Bulovic V, Bawendi MG. Quantum-dot size and thin-film dielectric constant: precision measurement and disparity with simple models. Nano Lett 2015; 15:21-26. [PMID: 25531164 DOI: 10.1021/nl5024244] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [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
We study the dielectric constant of lead sulfide quantum dot (QD) films as a function of the volume fraction of QDs by varying the QD size and keeping the ligand constant. We create a reliable QD sizing curve using small-angle X-ray scattering (SAXS), thin-film SAXS to extract a pair-distribution function for QD spacing, and a stacked-capacitor geometry to measure the capacitance of the thin film. Our data support a reduced dielectric constant in nanoparticles.
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Affiliation(s)
- Darcy D W Grinolds
- Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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7
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Thompson NJ, Wilson MWB, Congreve DN, Brown PR, Scherer JM, Bischof TS, Wu M, Geva N, Welborn M, Voorhis TV, Bulović V, Bawendi MG, Baldo MA. Energy harvesting of non-emissive triplet excitons in tetracene by emissive PbS nanocrystals. Nat Mater 2014; 13:1039-43. [PMID: 25282507 DOI: 10.1038/nmat4097] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 09/01/2014] [Indexed: 05/21/2023]
Abstract
Triplet excitons are ubiquitous in organic optoelectronics, but they are often an undesirable energy sink because they are spin-forbidden from emitting light and their high binding energy hinders the generation of free electron-hole pairs. Harvesting their energy is consequently an important technological challenge. Here, we demonstrate direct excitonic energy transfer from 'dark' triplets in the organic semiconductor tetracene to colloidal PbS nanocrystals, thereby successfully harnessing molecular triplet excitons in the near infrared. Steady-state excitation spectra, supported by transient photoluminescence studies, demonstrate that the transfer efficiency is at least (90 ± 13)%. The mechanism is a Dexter hopping process consisting of the simultaneous exchange of two electrons. Triplet exciton transfer to nanocrystals is expected to be broadly applicable in solar and near-infrared light-emitting applications, where effective molecular phosphors are lacking at present. In particular, this route to 'brighten' low-energy molecular triplet excitons may permit singlet exciton fission sensitization of conventional silicon solar cells.
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Affiliation(s)
- Nicholas J Thompson
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Mark W B Wilson
- 1] Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA [2] Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Daniel N Congreve
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Patrick R Brown
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Jennifer M Scherer
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Thomas S Bischof
- 1] Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA [2] Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Mengfei Wu
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Nadav Geva
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Matthew Welborn
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Troy Van Voorhis
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Vladimir Bulović
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Moungi G Bawendi
- 1] Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA [2] Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Marc A Baldo
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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8
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Chuang CHM, Brown PR, Bulović V, Bawendi MG. Improved performance and stability in quantum dot solar cells through band alignment engineering. Nat Mater 2014; 13:796-801. [PMID: 24859641 PMCID: PMC4110173 DOI: 10.1038/nmat3984] [Citation(s) in RCA: 644] [Impact Index Per Article: 64.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 04/15/2014] [Indexed: 05/19/2023]
Abstract
Solution processing is a promising route for the realization of low-cost, large-area, flexible and lightweight photovoltaic devices with short energy payback time and high specific power. However, solar cells based on solution-processed organic, inorganic and hybrid materials reported thus far generally suffer from poor air stability, require an inert-atmosphere processing environment or necessitate high-temperature processing, all of which increase manufacturing complexities and costs. Simultaneously fulfilling the goals of high efficiency, low-temperature fabrication conditions and good atmospheric stability remains a major technical challenge, which may be addressed, as we demonstrate here, with the development of room-temperature solution-processed ZnO/PbS quantum dot solar cells. By engineering the band alignment of the quantum dot layers through the use of different ligand treatments, a certified efficiency of 8.55% has been reached. Furthermore, the performance of unencapsulated devices remains unchanged for over 150 days of storage in air. This material system introduces a new approach towards the goal of high-performance air-stable solar cells compatible with simple solution processes and deposition on flexible substrates.
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Affiliation(s)
- Chia-Hao M. Chuang
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, United States
| | - Patrick R. Brown
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, United States
| | - Vladimir Bulović
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, United States
| | - Moungi G. Bawendi
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, United States
- Correspondence and requests for materials should be addressed to M.G.B. ()
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9
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Ko DK, Brown PR, Bawendi MG, Bulović V. p-i-n Heterojunction solar cells with a colloidal quantum-dot absorber layer. Adv Mater 2014; 26:4845-50. [PMID: 24862978 DOI: 10.1002/adma.201401250] [Citation(s) in RCA: 9] [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] [Received: 03/20/2014] [Revised: 04/15/2014] [Indexed: 05/04/2023]
Abstract
A quantum-dot (QD) p-i-n heterojunction solar cell with an increased depletion region is demonstrated by depleting the QD layer from both the front and back junctions. Due to a combination of improved charged extraction and increased light absorption, a 120% increase in the short-circuit current is achieved compared with that of conventional ZnO/QD devices.
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Affiliation(s)
- Dong-Kyun Ko
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA
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10
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Brown PR, Kim D, Lunt RR, Zhao N, Bawendi MG, Grossman JC, Bulović V. Energy level modification in lead sulfide quantum dot thin films through ligand exchange. ACS Nano 2014; 8:5863-72. [PMID: 24824726 DOI: 10.1021/nn500897c] [Citation(s) in RCA: 399] [Impact Index Per Article: 39.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The electronic properties of colloidal quantum dots (QDs) are critically dependent on both QD size and surface chemistry. Modification of quantum confinement provides control of the QD bandgap, while ligand-induced surface dipoles present a hitherto underutilized means of control over the absolute energy levels of QDs within electronic devices. Here, we show that the energy levels of lead sulfide QDs, measured by ultraviolet photoelectron spectroscopy, shift by up to 0.9 eV between different chemical ligand treatments. The directions of these energy shifts match the results of atomistic density functional theory simulations and scale with the ligand dipole moment. Trends in the performance of photovoltaic devices employing ligand-modified QD films are consistent with the measured energy level shifts. These results identify surface-chemistry-mediated energy level shifts as a means of predictably controlling the electronic properties of colloidal QD films and as a versatile adjustable parameter in the performance optimization of QD optoelectronic devices.
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Affiliation(s)
- Patrick R Brown
- Department of Physics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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11
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Jean J, Chang S, Brown PR, Cheng JJ, Rekemeyer PH, Bawendi MG, Gradečak S, Bulović V. ZnO nanowire arrays for enhanced photocurrent in PbS quantum dot solar cells. Adv Mater 2013; 25:2790-6. [PMID: 23440957 DOI: 10.1002/adma.201204192] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2012] [Revised: 11/24/2012] [Indexed: 05/11/2023]
Abstract
Vertical arrays of ZnO nanowires can decouple light absorption from carrier collection in PbS quantum dot solar cells and increase power conversion efficiencies by 35%. The resulting ordered bulk heterojunction devices achieve short-circuit current densities in excess of 20 mA cm(-2) and efficiencies of up to 4.9%.
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Affiliation(s)
- Joel Jean
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA
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12
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Chang LY, Lunt RR, Brown PR, Bulović V, Bawendi MG. Low-temperature solution-processed solar cells based on PbS colloidal quantum dot/CdS heterojunctions. Nano Lett 2013; 13:994-9. [PMID: 23406331 DOI: 10.1021/nl3041417] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
PbS colloidal quantum dot heterojunction solar cells have shown significant improvements in performance, mostly based on devices that use high-temperature annealed transition metal oxides to create rectifying junctions with quantum dot thin films. Here, we demonstrate a solar cell based on the heterojunction formed between PbS colloidal quantum dot layers and CdS thin films that are deposited via a solution process at 80 °C. The resultant device, employing a 1,2-ethanedithiol ligand exchange scheme, exhibits an average power conversion efficiency of 3.5%. Through a combination of thickness-dependent current density-voltage characteristics, optical modeling, and capacitance measurements, the combined diffusion length and depletion width in the PbS quantum dot layer is found to be approximately 170 nm.
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Affiliation(s)
- Liang-Yi Chang
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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13
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Jadhav PJ, Brown PR, Thompson N, Wunsch B, Mohanty A, Yost SR, Hontz E, Van Voorhis T, Bawendi MG, Bulović V, Baldo MA. Triplet exciton dissociation in singlet exciton fission photovoltaics. Adv Mater 2012; 24:6169-6174. [PMID: 22968762 DOI: 10.1002/adma.201202397] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 07/23/2012] [Indexed: 06/01/2023]
Abstract
Triplet exciton dissociation in singlet exciton fission devices with three classes of acceptors are characterized: fullerenes, perylene diimides, and PbS and PbSe colloidal nanocrystals. Using photocurrent spectroscopy and a magnetic field probe it is found that colloidal PbSe nanocrystals are the most promising acceptors, capable of efficient triplet exciton dissociation and long wavelength absorption.
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Affiliation(s)
- Priya J Jadhav
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA
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14
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Djuric Z, Ren J, Brown PR, Ellsworth JS, Sen A. Lifestyle factors associated with serum N-3 fatty acid levels in breast cancer patients. Breast 2012; 21:608-11. [PMID: 22377591 PMCID: PMC3368994 DOI: 10.1016/j.breast.2012.02.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [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] [Received: 06/30/2011] [Revised: 01/28/2012] [Accepted: 02/05/2012] [Indexed: 11/16/2022] Open
Abstract
Long chain n3 fatty acids appear to have beneficial effects in several domains of health relevant to breast cancer survivors. This study evaluated inter-individual differences in serum levels of n3 fatty acids in 40 breast cancer patients who were participating in a pilot study for prevention of weight gain. Significant predictors of baseline n3 fatty acid levels in serum were dietary intakes of n3 fatty acids, BMI, serum levels of carotenoids and TV hours watched/day, accounting for 43% of the variance. Counseling for prevention of weight gain also tended to increase n3 fatty acid blood levels over time during chemotherapy.
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Affiliation(s)
- Zora Djuric
- Department of Family Medicine, University of Michigan, Ann Arbor, MI 48109, USA.
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15
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Osedach TP, Zhao N, Andrew TL, Brown PR, Wanger DD, Strasfeld DB, Chang LY, Bawendi MG, Bulović V. Bias-stress effect in 1,2-ethanedithiol-treated PbS quantum dot field-effect transistors. ACS Nano 2012; 6:3121-7. [PMID: 22480161 DOI: 10.1021/nn3008788] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We investigate the bias-stress effect in field-effect transistors (FETs) consisting of 1,2-ethanedithiol-treated PbS quantum dot (QD) films as charge transport layers in a top-gated configuration. The FETs exhibit ambipolar operation with typical mobilities on the order of μ(e) = 8 × 10(-3) cm(2) V(-1) s(-1) in n-channel operation and μ(h) = 1 × 10(-3) cm(2) V(-1) s(-1) in p-channel operation. When the FET is turned on in n-channel or p-channel mode, the established drain-source current rapidly decreases from its initial magnitude in a stretched exponential decay, manifesting the bias-stress effect. The choice of dielectric is found to have little effect on the characteristics of this bias-stress effect, leading us to conclude that the associated charge-trapping process originates within the QD film itself. Measurements of bias-stress-induced time-dependent decays in the drain-source current (I(DS)) are well fit to stretched exponential functions, and the time constants of these decays in n-channel and p-channel operation are found to follow thermally activated (Arrhenius) behavior. Measurements as a function of QD size reveal that the stressing process in n-channel operation is faster for QDs of a smaller diameter while stress in p-channel operation is found to be relatively invariant to QD size. Our results are consistent with a mechanism in which field-induced nanoscale morphological changes within the QD film result in screening of the applied gate field. This phenomenon is entirely recoverable, which allows us to repeatedly observe bias stress and recovery characteristics on the same device. This work elucidates aspects of charge transport in chemically treated lead chalcogenide QD films and is of relevance to ongoing investigations toward employing these films in optoelectronic devices.
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Affiliation(s)
- Timothy P Osedach
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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16
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Paydavosi S, Aidala KE, Brown PR, Hashemi P, Supran GJ, Osedach TP, Hoyt JL, Bulović V. Detection of charge storage on molecular thin films of tris(8-hydroxyquinoline) aluminum (Alq3) by Kelvin force microscopy: a candidate system for high storage capacity memory cells. Nano Lett 2012; 12:1260-1264. [PMID: 22332966 DOI: 10.1021/nl203696v] [Citation(s) in RCA: 4] [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: 05/31/2023]
Abstract
Retention and diffusion of charge in tris(8-hydroxyquinoline) aluminum (Alq(3)) molecular thin films are investigated by injecting electrons and holes via a biased conductive atomic force microscopy tip into the Alq(3) films. After the charge injection, Kelvin force microscopy measurements reveal minimal changes with time in the spatial extent of the trapped charge domains within Alq(3) films, even for high hole and electron densities of >10(12) cm(-2). We show that this finding is consistent with the very low mobility of charge carriers in Alq(3) thin films (<10(-7) cm(2)/(Vs)) and that it can benefit from the use of Alq(3) films as nanosegmented floating gates in flash memory cells. Memory capacitors using Alq(3) molecules as the floating gate are fabricated and measured, showing durability over more than 10(4) program/erase cycles and the hysteresis window of up to 7.8 V, corresponding to stored charge densities as high as 5.4 × 10(13) cm(-2). These results demonstrate the potential for use of molecular films in high storage capacity nonvolatile memory cells.
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Affiliation(s)
- Sarah Paydavosi
- Laboratory of Organic and Nanostructured Electronics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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Park H, Brown PR, Bulović V, Kong J. Graphene as transparent conducting electrodes in organic photovoltaics: studies in graphene morphology, hole transporting layers, and counter electrodes. Nano Lett 2012; 12:133-140. [PMID: 22107487 DOI: 10.1021/nl2029859] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In this work, organic photovoltaics (OPV) with graphene electrodes are constructed where the effect of graphene morphology, hole transporting layers (HTL), and counter electrodes are presented. Instead of the conventional poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) PEDOT:PSS HTL, an alternative transition metal oxide HTL (molybdenum oxide (MoO(3))) is investigated to address the issue of surface immiscibility between graphene and PEDOT:PSS. Graphene films considered here are synthesized via low-pressure chemical vapor deposition (LPCVD) using a copper catalyst and experimental issues concerning the transfer of synthesized graphene onto the substrates of OPV are discussed. The morphology of the graphene electrode and HTL wettability on the graphene surface are shown to play important roles in the successful integration of graphene films into the OPV devices. The effect of various cathodes on the device performance is also studied. These factors (i.e., suitable HTL, graphene surface morphology and residues, and the choice of well-matching counter electrodes) will provide better understanding in utilizing graphene films as transparent conducting electrodes in future solar cell applications.
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Affiliation(s)
- Hyesung Park
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Macko JA, Lunt RR, Osedach TP, Brown PR, Barr MC, Gleason KK, Bulovic V. Multijunction organic photovoltaics with a broad spectral response. Phys Chem Chem Phys 2012; 14:14548-53. [DOI: 10.1039/c2cp43000b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [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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Lunt RR, Osedach TP, Brown PR, Rowehl JA, Bulović V. Practical roadmap and limits to nanostructured photovoltaics. Adv Mater 2011; 23:5712-27. [PMID: 22057647 DOI: 10.1002/adma.201103404] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2011] [Indexed: 05/11/2023]
Abstract
The significant research interest in the engineering of photovoltaic (PV) structures at the nanoscale is directed toward enabling reductions in PV module fabrication and installation costs as well as improving cell power conversion efficiency (PCE). With the emergence of a multitude of nanostructured photovoltaic (nano-PV) device architectures, the question has arisen of where both the practical and the fundamental limits of performance reside in these new systems. Here, the former is addressed a posteriori. The specific challenges associated with improving the electrical power conversion efficiency of various nano-PV technologies are discussed and several approaches to reduce their thermal losses beyond the single bandgap limit are reviewed. Critical considerations related to the module lifetime and cost that are unique to nano-PV architectures are also addressed. The analysis suggests that a practical single-junction laboratory power conversion efficiency limit of 17% and a two-cell tandem power conversion efficiency limit of 24% are possible for nano-PVs, which, when combined with operating lifetimes of 10 to 15 years, could position them as a transformational technology for solar energy markets.
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Affiliation(s)
- Richard R Lunt
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, 48824, USA.
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Brown PR, Lunt RR, Zhao N, Osedach TP, Wanger DD, Chang LY, Bawendi MG, Bulović V. Improved current extraction from ZnO/PbS quantum dot heterojunction photovoltaics using a MoO3 interfacial layer. Nano Lett 2011; 11:2955-61. [PMID: 21661734 DOI: 10.1021/nl201472u] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The ability to engineer interfacial energy offsets in photovoltaic devices is one of the keys to their optimization. Here, we demonstrate that improvements in power conversion efficiency may be attained for ZnO/PbS heterojunction quantum dot photovoltaics through the incorporation of a MoO(3) interlayer between the PbS colloidal quantum dot film and the top-contact anode. Through a combination of current-voltage characterization, circuit modeling, Mott-Schottky analysis, and external quantum efficiency measurements performed with bottom- and top-illumination, these enhancements are shown to stem from the elimination of a reverse-bias Schottky diode present at the PbS/anode interface. The incorporation of the high-work-function MoO(3) layer pins the Fermi level of the top contact, effectively decoupling the device performance from the work function of the anode and resulting in a high open-circuit voltage (0.59 ± 0.01 V) for a range of different anode materials. Corresponding increases in short-circuit current and fill factor enable 1.5-fold, 2.3-fold, and 4.5-fold enhancements in photovoltaic device efficiency for gold, silver, and ITO anodes, respectively, and result in a power conversion efficiency of 3.5 ± 0.4% for a device employing a gold anode.
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Affiliation(s)
- Patrick R Brown
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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Brown PR, Alaszewski A, Swift T, Nordin A. Actions speak louder than words: the embodiment of trust by healthcare professionals in gynae-oncology. Sociol Health Illn 2011; 33:280-295. [PMID: 21299570 DOI: 10.1111/j.1467-9566.2010.01284.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Trust is vital for quality healthcare outcomes, yet existing research neglects the 'embodiedness' of the interactions on which trust is based. This article draws on qualitative data from semi-structured interviews with cervical cancer patients. The significance of body work in winning or, on occasions, undermining trust emerged as a key theme within the responses. Interpretations of professionals' verbal and non-verbal presentations-of-self were often mutually reinforcing and intrinsically linked--forming a more general locus of meaning from which assumptions of competence and care were drawn. Yet it also became apparent that, whilst verbal communication was useful in establishing the agenda of the professional in relation to that of the patient, it was body work which was crucial in corroborating and validating beliefs pertaining to the ability and willingness of the professional to deliver this agenda in the future. The multi-temporal nature of trust makes apparent how certain seemingly distinct forms of body work--as presentation-of-self versus more hands-on modes--are inherently intertwined. Trust, and the affective relationship in which it is rooted, bridges the present with the future and thus makes apparent how seemingly 'detached' forms of body work are connected to the emotion-work of the caring role and the craftwork of body work as touch.
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Brown PR. The phenomenology of trust: A Schutzian analysis of the social construction of knowledge by gynae-oncology patients. Health, Risk & Society 2009. [DOI: 10.1080/13698570903180455] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Kay RG, Barton C, Velloso CP, Brown PR, Bartlett C, Blazevich AJ, Godfrey RJ, Goldspink G, Rees R, Ball GR, Cowan DA, Harridge SD, Roberts J, Teale P, Creaser CS. High-throughput ultra-high-performance liquid chromatography/tandem mass spectrometry quantitation of insulin-like growth factor-I and leucine-rich alpha-2-glycoprotein in serum as biomarkers of recombinant human growth hormone administration. Rapid Commun Mass Spectrom 2009; 23:3173-3182. [PMID: 19718777 DOI: 10.1002/rcm.4237] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Insulin-like growth factor-I (IGF-I) is a known biomarker of recombinant human growth hormone (rhGH) abuse, and is also used clinically to confirm acromegaly. The protein leucine-rich alpha-2-glycoprotein (LRG) was recently identified as a putative biomarker of rhGH administration. The combination of an ACN depletion method and a 5-min ultra-high-performance liquid chromatography/tandem mass spectrometry (uHPLC/MS/MS)-based selected reaction monitoring (SRM) assay detected both IGF-I and LRG at endogenous concentrations. Four eight-point standard addition curves of IGF-I (16-2000 ng/mL) demonstrated good linearity (r(2) = 0.9991 and coefficients of variance (CVs) <13%). Serum samples from two rhGH administrations were extracted and their uHPLC/MS/MS-derived IGF-I concentrations correlated well against immunochemistry-derived values. Combining IGF-I and LRG data improved the separation of treated and placebo states compared with IGF-I alone, further strengthening the hypothesis that LRG is a biomarker of rhGH administration. Artificial neural networks (ANNs) analysis of the LRG and IGF-I data demonstrated an improved model over that developed using IGF-I alone, with a predictive accuracy of 97%, specificity of 96% and sensitivity of 100%. Receiver operator characteristic (ROC) analysis gave an AUC value of 0.98. This study demonstrates the first large scale and high throughput uHPLC/MS/MS-based quantitation of a medium abundance protein (IGF-I) in human serum. Furthermore, the data we have presented for the quantitative analysis of IGF-I suggest that, in this case, monitoring a single SRM transition to a trypsin peptide surrogate is a valid approach to protein quantitation by LC/MS/MS.
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Affiliation(s)
- R G Kay
- Drug Development Services, Quotient Bioresearch Ltd., Fordham CB7 5WW, UK.
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Ali Akbar S, Nicolaides KH, Brown PR. The localisation of copper/zinc superoxide dismutase in human normal term placenta by an immunofluorescence technique. J OBSTET GYNAECOL 2009; 18:44-6. [PMID: 15512001 DOI: 10.1080/01443619868262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The antioxidant enzyme copper and zinc containing superoxide dismutase (Cu/Zn SOD) was localised in normal human term placenta to the syncytial trophoblast, using an immunofluorescence technique. Possible physiological roles of Cu/Zn SOD in the human placenta are discussed.
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Affiliation(s)
- S Ali Akbar
- Molecular Biology and Biophysics Section, Division of Biomedical Sciences, King's College London, UK
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Abstract
Recent reforms within the UK National Health Service, particularly the introduction of clinical governance, have been enacted with the apparent aim of rebuilding patient trust. This paper analyses the approach taken by policy makers, arguing that it is based very much on an instrumental conception of trust. The assumptions and limitations of this model are discussed and in so doing, a communicative understanding of trust is proposed as an alternative. It is argued that the instrumental rationality and institutional focus inherent to instrumental trust neglect the importance of the communication between patient and medical professional and its affective dimensions. Communicative trust goes beyond a mere cognitive appreciation of the system and rather is dependent on the qualitative interaction at the access point, where the patient comes to believe that the communicative rationality of their best interests is mirrored by the professional's instrumental rationality. Whilst recent challenges to the confidence of patients in professionals and medical knowledge make some approximation of an ideal speech situation more imperative than previously, the application of an instrumental concept of trust in the NHS makes such interactions less likely, as well as facilitating a divergence between instrumental and communicative rationality in healthcare provision.
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Ali Akbar S, Nicolaides KH, Brown PR. Measurement of Cu/Zn SOD in placenta, cultured cells, various fetal tissues, decidua and semen by ELISA. J OBSTET GYNAECOL 2005; 18:331-5. [PMID: 15512102 DOI: 10.1080/01443619867056] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The concentration of copper/zinc-containing superoxide dismutase (Cu/Zn SOD) was measured in placental villous tissues (8-20 weeks' gestation), decidual tissues, cultured cells from chorionic villi and amniotic fluid cells, various fetal tissues (8-11 weeks' gestation), spermatozoa, seminal plasma and ovarian follicular fluid using a sensitive enzyme-linked immunosorbent assay (ELISA). The isoenzyme was expressed in all samples expect ovarian follicular fluid. Cu/Zn SOD was also detected in hydatidiform mole and choriocarcinoma. In placental villous tissues the concentration of the enzyme increased with gestation between 8 and 20 weeks of pregnancy (n = 69, r = 0.34, P < 0.005).
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Affiliation(s)
- S Ali Akbar
- Molecular Biology and Biophysics Section, Division of Biomedical Sciences, and Harris Birthright Research Centre for Fetal Medicine, Department of Obstetrics and Gynaecology, King's College Hospital, London, UK
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Whitney RH, Mower MM, Brown PR, Ostrander GK. 12 EFFECT OF THERMAL APPLICATIONS ON DURATION OF EXPERIMENTAL ATRIAL FIBRILLATION. J Investig Med 2004. [DOI: 10.1136/jim-52-suppl1-565] [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: 11/04/2022]
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Abstract
Burkholderia cepacia (formerly Pseudomonas cepacia) grows in media containing acetamide or propionamide as C and N sources. Chromosomal DNA from a hospital isolate of B. cepacia served as a template in PCRs using primers designed for the amplification of the P. aeruginosa amiE gene that encodes an aliphatic amidase. Partial sequencing of the PCR products gave a translated sequence 100% identical with the amino acid sequence of P. aeruginosa amidase. A search of Burkholderia genomes detected a putative amidase in B. cepacia J2315 with high identity to the P. aeruginosa amidase and predicted that other Burkholderia species also possessed CN_hydrolases that use the same catalytic triad (Glu-Lys-Cys) as amidase. Superimposition of theoretical three-dimensional models suggested that differences in the amino acid sequences between amidases from B. cepacia (hospital isolate) and B. cepacia J2315 do not affect their three-dimensional structure.
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Affiliation(s)
- C Novo
- INETI/DB/UTPAM, Edifi;cio F, Estrada do Paço do Lumiar, 1649-038 Lisboa, Portugal.
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Brown PR. Looking back: a better knowledge of pediatrics has diminished the death rate of infants and increased the death rate of the adult in 1915. J Miss State Med Assoc 2002; 43:194-5. [PMID: 12101903] [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: 02/25/2023]
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Lietman SA, Miyamoto S, Brown PR, Inoue N, Reddi AH. The temporal sequence of spontaneous repair of osteochondral defects in the knees of rabbits is dependent on the geometry of the defect. J Bone Joint Surg Br 2002; 84:600-6. [PMID: 12043787 DOI: 10.1302/0301-620x.84b4.11631] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Damage to articular cartilage is a common injury, for which there is no effective treatment. Our aims were to investigate the temporal sequence of the repair of articular cartilage and to define a critical-size defect. Full-thickness defects were made in adult male New Zealand white rabbits. The diameter (1 to 4 mm) of the defects was varied in order to determine the effect that the size and depth of the defect had on its healing. The defects were made in the femoral groove of the knee with one defect per knee and eight knees per group. The tissues were fixed in formalin at days 3, 7, 14, 21, 28, 42, 84 and 126 after operation and the sections stained with Toluidine Blue. These were then examined and evaluated for several parameters including the degree of metachromasia and the amount of subchondral bone which had reformed in the defect. The defects had a characteristic pattern of healing which differed at different days and for different sizes of defect. Specifically, the defects of 1 mm first peaked in terms of metachromasia at day 21, those of 2 mm at day 28, followed by defects of 3 mm and 4 mm. The healing of the subchondral bone was slowest in defects of 1 mm.
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Affiliation(s)
- S A Lietman
- Department of Orthopaedic Surgery, The Johns Hopkins University, Baltimore, Maryland 21205, USA
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Abstract
Amidase from Pseudomonas aeruginosa was purified by anionic exchange chromatography and used to immunise female Balb/c mice. Monoclonal antibodies (MAbs) were raised by hybridoma technology using Sp2/0 myeloma cells as fusion partner. A selected IgM subclass MAb was purified from in vitro hybridoma cell line supernatant by a two-step anionic exchange chromatography. The MAb was specific for amidase from P. aeruginosa as determined by Western blotting and recognized the native and denatured forms of the enzyme.
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Affiliation(s)
- C Novo
- INETI, Departmento de Biotecnologia, UTPAM, Estrada do Paço do Lumiar, 1649-038, Lisboa, Portugal.
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Robb CS, Brown PR. Catechins in tea: chemistry and analysis. Adv Chromatogr 2001; 41:379-410. [PMID: 11263072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Affiliation(s)
- C S Robb
- Department of Chemistry, University of Rhode Island, Kingston, Rhode Island, USA
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Abstract
BACKGROUND This study evaluated the effects of dietary sodium manipulation in dogs on the regulation of canine angiotensin receptors (cAT1 and cAT2) in the kidney and adrenal. METHODS Isolated glomeruli and membranes from renal medulla and the adrenal gland were used in radioligand binding assays from two groups of dogs: dogs maintained on low-sodium diet for two weeks followed by a high-sodium diet for two weeks (H), and dogs were maintained on the reverse schedule (L). RESULTS Analysis of the binding data showed that dietary sodium manipulation had no significant effects on cAT1 and cAT2 receptor binding affinities in glomeruli, renal medulla, and adrenal tissues. In contrast, dietary sodium loading induced a marked increase in cAT1 receptor expression in both the glomeruli and adrenal compared with receptor expression in salt-restricted animals [H/L ratio: glomeruli (1.5), renal medulla (1.1), adrenal (1.6)] that inversely correlated with the activity of the plasma renin angiotensin system. Conversely, adrenal cAT2 receptor expression was regulated in an inverse manner in the H and L animal groups [H/L ratio: 0.7]. CONCLUSIONS This study demonstrates that renal glomerular and adrenal AT1 receptors in the dog are coordinately down-regulated by dietary sodium restriction compared with sodium loading, which is distinctly different from the reciprocal regulation observed for rat AT1 receptors in these tissues. Collectively, these data suggest that postreceptor events in dogs are determinants of the aldosterone response observed during sodium restriction. These findings have important implications for the regulation of the renin-angiotensin system in humans, and suggest that coordinate regulation of AT1 receptors in the adrenal and glomeruli represent a negative feedback mechanism that when functioning normally prevents fluctuations of arterial blood pressure and development of arterial hypertension in response to changes in dietary sodium.
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Affiliation(s)
- W Zheng
- Division of Nephrology and Hypertension, Department of Medicine, Georgetown University, Washington DC 20007-2145, USA
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Needham SR, Jeanville PM, Brown PR, Estape ES. Performance of a pentafluorophenylpropyl stationary phase for the electrospray ionization high-performance liquid chromatography-mass spectrometry-mass spectrometry assay of cocaine and its metabolite ecgonine methyl ester in human urine. J Chromatogr B Biomed Sci Appl 2000; 748:77-87. [PMID: 11092588 DOI: 10.1016/s0378-4347(00)00271-1] [Citation(s) in RCA: 33] [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] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A pentafluorophenylpropyl (PFPP) bonded silica column has been used for the high-performance liquid chromatography-electrospray ionization-mass spectrometry-mass spectrometry assay (HPLC-ESI-MS-MS) of cocaine (COC) and its metabolite, ecgonine methyl ester (EME) in human urine. COC and EME were used as model basic solutes to demonstrate that a PFPP phase yields excellent results for the assay and validation of drugs in biological fluids. The assay was linear over three orders of magnitude (1.0-1000 ng/ml) and precision and accuracy of the assay was 4 and 15%, respectively. The limit of detection (LOD) for COC and EME was 1.6 and 2.8 pg on column, respectively. In addition, only a simple 1:10 dilution of the urine was necessary for the sample preparation procedure thus saving time on a laborious extraction step. The major advantage of the PFPP phase was the enhancement of the ESI-MS signal by providing good retention and good peak shape of COC and EME with a mobile phase of 90% acetonitrile. The MS signal for COC was a factor of 12 times greater on the PFPP phase than on the C18 phase.
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Affiliation(s)
- S R Needham
- Drug Metabolism Technology Group, Pfizer, Inc., Central Research Division, Groton, CT 06340, USA.
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Abstract
A mutant strain, KLAM59, of Pseudomonas aeruginosa has been isolated that synthesizes a catalytically inactive amidase. The mutation in the amidase gene has been identified (Glu59Val) by direct sequencing of PCR-amplified mutant gene and confirmed by sequencing the cloned PCR-amplified gene. The wild-type and altered amidase genes were cloned into an expression vector and both enzymes were purified by affinity chromatography on epoxy-activated Sepharose 6B-acetamide followed by gel filtration chromatography. The mutant enzyme was catalytically inactive, and it was detected in column fractions by monoclonal antibodies previously raised against the wild-type enzyme using an ELISA sandwich method. The recombinant wild-type and mutant enzymes were purified with a final recovery of enzyme in the range of 70-80%. The wild-type and mutant enzymes behaved differently on the affinity column as shown by their elution profiles. The molecular weights of the purified wild-type and mutant amidases were found to be 210,000 and 78,000 Dalton, respectively, by gel filtration chromatography. On the other hand, the mutant enzyme ran as a single protein band on SDS-PAGE and native PAGE with a M(r) of 38,000 and 78,000 Dalton, respectively. These data suggest that the substitution Glu59Val was responsible for the dimeric structure of the mutant enzyme as opposed to the hexameric form of the wild-type enzyme. Therefore, the Glu59 seems to be a critical residue in the maintenance of the native quaternary structure of amidase.
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Affiliation(s)
- A Karmali
- Departamento de Engenharia Química do Instituto Superior de Engenharia de Lisboa, Portugal.
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Needham SR, Brown PR. The high performance liquid chromatography electrospray ionization mass spectrometry analysis of diverse basic pharmaceuticals on cyanopropyl and pentafluorophenylpropyl stationary phases. J Pharm Biomed Anal 2000; 23:597-605. [PMID: 10933554 DOI: 10.1016/s0731-7085(00)00348-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [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: 10/17/2022]
Abstract
Cyanopropyl (CN) and pentafluorophenylpropyl (PFPP) modified silica columns give good retention and good peak shape for the high performance liquid chromatography/electrospray ionization/mass spectrometry (HPLC/ESI/MS) analysis of several classes of basic drugs. These phases enhance the ESI-MS signal by providing good retention of basic drugs with a mobile phase containing 90% acetonitrile. With C18 columns, in order to achieve good retention of basic drugs, only a mobile phase containing less than 40% acetonitrile can be used. Higher concentrations of acetonitrile produce a larger MS signal in the ESI process; the MS signal was a factor of 9 and 12 times greater on the CN and PFPP phases when compared with the C18 phase for the analysis of codeine. The C18 phase required only 4.0-6.0% acetonitrile to obtain the same retention time for codeine. The CN and PFPP stationary phases can be used for the analysis of a range of basic drugs, including many compounds which are poorly retained on the popular C18 and C8 stationary phases. Applications of CN and PFPP columns in the HPLC/ESI/MS of basic drugs include the analysis of antimalarials, such as quinine, bronchodilators, such as salbutamol and tulobuterol, cardioactive drugs, such as procainamide and beta-blockers, tricyclic antidepressants (TCAs), such as protriptyline and trimipramine and alkaloids, such as morphine and codeine. The CN and PFPP phases are also useful for the analysis of bufuralol and its metabolite, hydroxy-bufuralol. All the above analyses were performed using the same mobile phase, 90% acetonitrile; thus the HPLC method development process was expedited. The CN and PFPP phases also gave reproducible retention times and peak shape after more than 8 h of analyses.
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Affiliation(s)
- S R Needham
- Candidate Synthesis Enhancement and Evaluation Group, Pfizer Central Research, Groton, CT 06340, USA.
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Rietmeijer CA, Oh MK, Bull SS, Brown PR, Wang SA, Mertz KJ. Monitoring std prevalence and reproductive health care among high-risk adolescent women. J Pediatr Adolesc Gynecol 2000; 13:90-1. [PMID: 10869977 DOI: 10.1016/s1083-3188(00)00020-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Background: Urban adolescent women, particularly those in socially disadvantaged situations are at high risk for infections with Chlamydia trachomatis (CT), and Neisseria gonorrhoeae (GC) and their sequelae. Non-invasive screening technologies, including ligase chain reaction (LCR) and polymerase chain reaction (PCR) urine tests for CT and GC allow for provision of screening services in settings frequented by high-risk adolescents where such services have not been traditionally provided. In 1999, the CDC lead a multi-site project monitoring STD prevalence and reproductive health service, collecting a standard set of variables in women <20 yrs in juvenile justice system, drug treatment centers, and school-based clinics. This report provides preliminary data from Alabama and Colorado. Methods: Adolescent women who present for intake/services at selected facilities are enrolled in the project. In collaboration with CDC, sites developed a set of standard variables to be collected, including demographics, risk behaviors, symptoms, test performed, and test results. Dependent on services already performed, sites added CT and/or GC urine PCR/LCR and pregnancy testing to existing screening protocols.Results: In first 3-months, 533 adolescent women were enrolled in this on-going study; 379 in juvenile institutions, 38 in drug treatment centers, and 116 in school-based clinics. Mean age was 16 yrs, over 90% were sexually experienced, nearly 50% did not use condom with the last sex, less than 40% reported "current" birth control use, over 2/3 had sexual intercourse in past 3 months, many with multiple partners. Prevalence rates for CT and GC are summarized in the table. Conclusions: Non-invasive (urine) LCR/PCR tests allow for easy monitoring of selected STDs among adolescent women in high-risk settings. These findings may contribute to a sentinel surveillance system among high-risk populations and, in turn, may provide the rationale for the development of health care/intervention priorities at policy level.
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Wu Q, Nelson WH, Treubig JM, Brown PR, Hargraves P, Kirs M, Feld M, Desari R, Manoharan R, Hanlon EB. UV resonance Raman detection and quantitation of domoic acid in phytoplankton. Anal Chem 2000; 72:1666-71. [PMID: 10763267 DOI: 10.1021/ac991052d] [Citation(s) in RCA: 20] [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: 11/28/2022]
Abstract
Cultures of the phytoplankton diatom, Pseudonitzschia multiseries, have been harvested under controlled growth conditions ranging from late logarithmic to late stationary phase (17-58 days). The amount of domoic acid (DA) present in the growth media and in the homogenized cells has been determined by HPLC. Defined samples of media, homogenized cells, whole cells, and whole cells in media have been laser excited at 251 nm for the purpose of selectively exciting intense UV resonance Raman spectra from DA in the samples. Neither media nor cell component spectra from algae seriously interfere with DA spectra. The spectral cross sections for the dominant 1652-cm-1 mode of DA have been determined for 242-, 251-, and 257-nm excitation. Maximum sensitivities are achieved with 251-nm excitation because cross sections for DA are a maximum, and interference from other algal components becomes very small. DA concentrations that have been determined with 251-nm excitation by resonance Raman methods correlate closely with values determined independently with HPLC, especially at higher DA concentrations. The UV resonance Raman analysis of DA in phytoplankton algae is shown to be very sensitive and quantitative as well as rapid and nonintrusive.
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Affiliation(s)
- Q Wu
- Department of Chemistry and School of Oceanography, University of Rhode Island, Kingston 02881, USA
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Abstract
The analysis and use of fullerenes in capillary electrophoresis (CE) was investigated. Sodium dodecyl sulfate (SDS) was used to solubilize fullerenes C60, C70, and a mixture of C60 and C70 in water. The behavior of the solutions of the C60- and C70-SDS complexes was examined by CE with on-line UV-Vis diode array detection. This study included the use of a C60-SDS complex as a new method of micellar electrokinetic chromatography (MEKC) for the separation of polycyclic aromatic hydrocarbons (PAHs) using CE with uniwavelength detection. Since SDS micelles act as a pseudostationary phase in which the PAH compounds partition with their hydrophobic interior, the addition of C60 within the micelles enhanced separation of the PAHs. The preliminary results using C60-MEKC with SDS were compared to those obtained with MEKC with SDS. The capillary electrophoretic separations were performed in 10 mM borate-phosphate buffer with 100 mM SDS at pH 9.5.
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Affiliation(s)
- J M Treubig
- Department of Chemistry, University of Rhode Island, Kingston 02881, USA
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Needham SR, Brown PR, Duff K, Bell D. Optimized stationary phases for the high-performance liquid chromatography-electrospray ionization mass spectrometric analysis of basic pharmaceuticals. J Chromatogr A 2000; 869:159-70. [PMID: 10720235 DOI: 10.1016/s0021-9673(99)00986-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [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: 10/18/2022]
Abstract
Stationary phases were investigated for HPLC coupled with electrospray ionization mass spectrometry (ESI-MS) for the analysis of basic drugs. Tricyclic antidepressants (TCAs) and beta-blockers were used as model solutes. The functional groups, pentafluorophenyl (PFP), OH, CN or CH3 were attached to the silica via a propyl chain. The effects of these stationary phases as well as C8 and C18 phases on retention and peak shape of the basic drugs were studied. The CN and PFP phases adequately retained (tR of 2 to 6 min) the basic drugs when the mobile phase was composed of 90% acetonitrile, whereas with the C4, C8 and C18 phases, less than 40% acetonitrile had to be used to provide adequate retention of the basic drugs. Because acetonitrile provides better desolvation in ESI than an aqueous solvent, it produces an increased MS signal. As an example of the HPLC-ESI-MS analysis of the beta-blocker, pindolol, on a CN phase, the use of 90% acetonitrile in the mobile phase increased the ESI-MS signal by 790% when compared to a C18 phase which could use only 5% acetonitrile in the mobile phase for retention of the solute. In addition, the CN and PFP phases provided better peak shape than the OH phase and the hydrophobic phases (C4, C8 and C18) and ion-pairing or ion-suppressing agents were not required. The retention behavior of the TCAs and beta-blockers on each of the phases is described.
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Affiliation(s)
- S R Needham
- Pfizer, Inc., Candidate Synthesis Enhancement and Evaluation Group, Groton, CT 06340, USA.
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41
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McNabb TJ, Cremesti AE, Brown PR, Fischl AS. The separation and direct detection of ceramides and sphingoid bases by normal-phase high-performance liquid chromatography and evaporative light-scattering detection. Anal Biochem 1999; 276:242-50. [PMID: 10603247 DOI: 10.1006/abio.1999.4354] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [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: 11/22/2022]
Abstract
Sphingolipids are an important class of lipids due to their role as biologically active molecules and as intracellular second messengers. Sphingolipid metabolites are involved in a wide variety of important biological processes including signal transduction and growth regulation. Simple, quantitative analytical methods are needed to assay these complex lipids, in order to study their biological functions. The current methods used to quantify ceramides and long-chain sphingoid bases are primarily based on derivatization with uv or fluorescent tags and with radioactive-based enzymatic assays. A method was developed to separate ceramides and sphingoid bases by normal-phase high-performance liquid chromatography and detect them directly with evaporative light-scattering detection. Ceramides and the sphingoid bases phytosphingosine, dihydrosphingosine, sphingosine, and sphingosine 1-phosphate were resolved with a rapid and quantitative assay in the nanomole range. Yeast extracts grown to various time points were assayed for ceramide and sphingoid bases using a simple, isocratic HPLC system. Both ceramide and phytosphingosine, the primary sphingoid base present in yeast cell extracts, were detected in yeast cell extracts. Phytosphingosine was resolved as a sharp peak with the addition of triethylamine and formic acid modifiers to a chloroform/ethanol mobile phase. This method demonstrates the first direct assay of both ceramides and sphingoid bases.
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Affiliation(s)
- T J McNabb
- Chemistry Department, University of Rhode Island, West Kingston, Rhode Island, USA
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42
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Kamel AM, Brown PR, Munson B. Effects of mobile-phase additives, solution pH, ionization constant, and analyte concentration on the sensitivities and electrospray ionization mass spectra of nucleoside antiviral agents. Anal Chem 1999; 71:5481-92. [PMID: 10624156 DOI: 10.1021/ac9906429] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [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
The effects of various mobile-phase additives, solution pH, pKa, and analyte concentration on electrospray ionization mass spectra of a series of purine and pyrimidine nucleoside antiviral agents were studied in both positive and negative ion models. The use of 1% acetic acid resulted in good HPLC separation and the greatest sensitivity for [M + H]+ ions. In the negative ion mode, 50 mM ammonium hydroxide gave the greatest sensitivity for [M - H]- ions. The sensitivities as [M + H]+ ions were significantly larger than the sensitivities as [M - H]- ions for purine antiviral agents. Vidarabine monophosphate and pyrimidine antiviral agents, however, showed comparable or greater sensitivities as [M - H]- ions. The sensitivity as [M + H]+ showed no systematic variation with pH; however, the sensitivity as [M - H]- did increase with increasing pH. At constant pH, the ion intensity of the protonated species increased with increasing pKa. At higher analyte concentrations, dimer (M2H+) and trimer (M3H+) ions were observed. [M + Na]+ adducts were the dominant ions with 0.5 mM sodium salts for these compounds. The spectra of the more basic purine antiviral agents showed no [M + NH4]+ adduct ions, but [M + NH4]+ ions were the major peaks in the spectra of the less basic pyrimidine antiviral agents with ammonium salts. The ammonium adduct ion was formed preferentially when the proton affinity of the analyte was close to that of NH3. Abundant [M + OAc]- ions were observed for all of the antiviral agents except vidarabine monophosphate from solutions with added HOAc, NaOAc, and NH4OAc. The utility of mobile phases containing 1% HOAc or 50 mM NH4OH was demonstrated for chromatographic separations.
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Affiliation(s)
- A M Kamel
- Department of Drug Metabolism, Pfizer Inc., Groton, Connecticut 06340, USA.
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McDonald AM, Ryan JW, Brown PR, Manners CJ, Falconer AD, Kinnear RC, Harvey WJ, Hearne PR, Banaszczyk M, Kaldor JM. HIV prevalence at reception into Australian prisons, 1991-1997. Med J Aust 1999; 171:18-21. [PMID: 10451666 DOI: 10.5694/j.1326-5377.1999.tb123491.x] [Citation(s) in RCA: 7] [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: 11/17/2022]
Abstract
OBJECTIVE To measure the extent and outcome of HIV antibody testing at reception into Australian prisons. DESIGN Cross-sectional survey at reception into prison. PARTICIPANTS AND SETTING People received into Australian prisons from 1991 to 1997. MAIN OUTCOME MEASURES Number of people tested for HIV infection and prevalence of diagnosed HIV infection. RESULTS In 1991-1997, HIV antibody testing was carried out for 72% of prison entrants in Australia; the percentage tested declined significantly from 76% in 1991 to 67% in 1997 (P < 0.001). In New South Wales, the percentage of entrants tested at reception into prison dropped from almost 100% in 1991-1994 to 45% in 1997, whereas in the Northern Territory, South Australia and Western Australia the extent of testing increased significantly (P < 0.001). HIV prevalence was 0.2% among people received into Australian prisons in 1991-1997, and did not differ by sex. Most people with HIV infection (242/378; 64%) received into prison in 1991-1997 had been diagnosed at a previous entry; 136 people (36% of the total number of diagnoses) were newly diagnosed at reception into prison. CONCLUSIONS A national monitoring system in place from 1991 indicates generally high rates of HIV antibody testing and a low prevalence of HIV infection among people entering Australian prisons. In each year, people not previously known to the prison health service to have HIV infection were received into prison, indicating continuing HIV infection in the population entering Australian prisons.
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Affiliation(s)
- A M McDonald
- National Centre in HIV Epidemiology and Clinical Research, Sydney, NSW.
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Farnaud S, Tata R, Sohi MK, Wan T, Brown PR, Sutton BJ. Evidence that cysteine-166 is the active-site nucleophile of Pseudomonas aeruginosa amidase: crystallization and preliminary X-ray diffraction analysis of the enzyme. Biochem J 1999; 340 ( Pt 3):711-4. [PMID: 10359655 PMCID: PMC1220302] [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] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Wild-type and site-specific mutants C166S and C166A (Cys-166-->Ser and Cys-166-->Ala respectively) of the amidase (acylamide amidohydrolase, EC 3.5.1.4) from Pseudomonas aeruginosa were expressed in Escherichia coli by using the vector pKK223-3. Both mutant proteins were catalytically inactive but showed complete cross-reactivity with polyclonal antiserum raised against the wild-type enzyme, as well as CD spectra identical with that of the wild-type enzyme, which were indicative of correct folding. Cys-166 is therefore implicated as the active-site nucleophile. Titration of free thiol groups with 5,5'-dithiobis-(2-nitrobenzoic acid) indicated that Cys-166 is not a rapidly reacting residue. Crystals of both wild-type and C166S amidase grew with identical, rhombohedral morphology; X-ray diffraction analysis established the unit cell dimensions (a=b=c=84 A; alpha=beta=gamma=75 degrees) and space group (R3 or R32). These results imply a quaternary structure of six subunits, with most probably 32 symmetry; the existence of a hexameric structure was supported by molecular mass determinations based on gel filtration and electrophoretic mobility.
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Affiliation(s)
- S Farnaud
- Molecular Biology and Biophysics Section, Division of Biomolecular Sciences, King's College London, Strand, London WC2R 2LS, UK
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Needham SR, Brown PR, Duff K. Phenyl ring structures as stationary phases for the high performance liquid chromatography electrospray ionization mass spectrometric analysis of basic pharmaceuticals. Rapid Commun Mass Spectrom 1999; 13:2231-2236. [PMID: 10547629 DOI: 10.1002/(sici)1097-0231(19991130)13:22<2231::aid-rcm779>3.0.co;2-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
To produce a large mass spectral signal in the analysis of basic drugs by high performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS), a high percentage of organic solvent is needed in the mobile phase. With the commonly used reversed phase columns (C18, C8 and C4) high concentrations of organic solvents cannot be used; therefore other stationary phases were investigated. The stationary phases investigated had phenyl ring structures; phenyl (Ph) and pentafluorophenyl (PFP) which were bonded directly to the silica backbone and other phases, pentafluorophenylpropyl (PFPP), phenylpropyl (PhP) and tolylpropyl (TP), which were attached to the silica via a propyl chain. The effects of these stationary phases on retention, peak shape and size of the signal in the mass spectrometric analysis of a selected group of basic drugs, tricyclic antidepressants (TCAs) and beta-blockers, were evaluated and compared with those obtained on a C18 column. The PFPP column was found to give the best results. The basic drugs were adequately retained with retention times greater than 2 minutes when the PFPP column was used with mobile phases of high concentrations of organic solvents. Thus the endogenous interferences could be eliminated and the analysis time was still rapid enough to have a high throughput. Most importantly, a mobile phase of 90% acetonitrile could be used which allowed easy desolvation in the ESI interface and provided good peak shapes. In addition, ion-pairing reagents and ion-suppressing agents which suppress the signal in ESI-MS were not required. The best results were obtained using a 1 cm column and a flow rate of 0.9 mL/min. With the PFPP stationary phase and a mobile phase of 90% acetonitrile, the HPLC/ESI mass spectral signal of the beta-blocker, oxprenolol, was increased by a factor of 16 compared with the C18 phase with only 12% acetonitrile in the mobile phase. Copyright 1999 John Wiley & Sons, Ltd.
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Affiliation(s)
- SR Needham
- Pfizer Central Research, Eastern Point Road, Groton, CT 06340, USA
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Abstract
Capillary electrophoresis is a useful tool for the analysis of nucleotides. Methods have been optimized for both CZE and MECC modes. A variety of CZE buffers, such as borate, carbonate and phosphate were used successfully. The pH of the buffer changes the charge on the nucleotides. Therefore, the selectivity of the analytes can be controlled by the acidity of the buffer solution. CE separations of nucleotides have been performed at all pH levels, in both CZE and MECC modes. SDS was the most commonly used modifier in MECC separations, but other additives have been added to optimize selectivity. In addition, nucleotides have been quantified in different matrices, including tissue and cell extracts and several DNA and RNA sources. This paper summarizes the methods used for the optimization of nucleotides by CE and includes the most recent techniques to improve selectivity, reproducibility and sensitivity. A summary of CE methods is used in analyses of nucleotides in biological matrices is included.
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Affiliation(s)
- S E Geldart
- Department of Chemistry, University of Rhode Island, Kingston 02881, USA
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Abstract
ELISA methods were used to determine the concentrations of CAI and CAII in spermatozoa, seminal plasma, ovarian follicular fluid, decidual tissues, chorionic villi and various fetal tissues at 8-11 weeks gestation. Both CAI and CAII were expressed in all subjects except ovarian follicular fluid samples. The possible physiological role(s) of carbonic anhydrases in fertilization, implantation and fetal development are discussed.
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Affiliation(s)
- S Ali Akbar
- Molecular Biology and Biophysics Section, Biomedical Sciences Division, King's College London, UK
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Sieber FE, Traystman RJ, Brown PR, Martin LJ. Protein kinase C expression and activity after global incomplete cerebral ischemia in dogs. Stroke 1998; 29:1445-52; discussion 1452-3. [PMID: 9660402 DOI: 10.1161/01.str.29.7.1445] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [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: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Studies suggest that protein kinase C (PKC) activation during ischemia plays an important role in glutamate neurotoxicity and that PKC inhibition may be neuroprotective. We tested the hypothesis that elevations in the biochemical activity and protein expression of Ca2+-dependent PKC isoforms occur in hippocampus and cerebellum during the period of delayed neurodegeneration after mild brain ischemia. METHODS We used a dog model of 20 minutes of global incomplete ischemia followed by either 6 hours, 1 day, or 7 days of recovery. Changes in PKC expression (Western blotting and immunocytochemistry) and biochemical activity were compared with neuropathology (percent ischemically damaged neurons) by means of hematoxylin and eosin staining. RESULTS The percentage of ischemically damaged neurons increased from 13+/-4% to 52+/-10% in CA1 and 24+/-11% to 69+/-6% in cerebellar Purkinje cells from 1 to 7 days, respectively. The occurrence of neuronal injury was accompanied by sustained increases in PKC activity (240% and 211% of control in hippocampus and cerebellum, respectively) and increased protein phosphorylation as detected by proteins containing phosphoserine residues. By Western blotting, the membrane-enriched fraction showed postischemic changes in protein expression with increases of 146+/-64% of control in hippocampal PKCalpha and increases of 138+/-38% of control in cerebellar PKCalpha, but no changes in PKCbeta and PKCgamma were observed. By immunocytochemistry, the neuropil of CA1 and CA4 in hippocampus and the radial glia in the molecular layer of cerebellum showed increased PKCalpha expression after ischemia. CONCLUSIONS This study shows that during the period of progressive ischemic neurodegeneration there are regionally specific increases in PKC activity, isoform-specific increases in membrane-associated PKC, and elevated protein phosphorylation at serine sites.
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Affiliation(s)
- F E Sieber
- Department of Anesthesiology, the Johns Hopkins Medical Institutions, Baltimore, MD, USA.
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Hatajik TD, Brown PR. Chiral separations of pharmaceuticals using capillary electrochromatography (CEC): an overview. J Capillary Electrophor 1998; 5:143-51. [PMID: 10797880] [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] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Enantiomers of bioactive molecules often differ in potency, toxicity, metabolism, and pharmacological actions. Capillary electrochromatography (CEC) is an emerging separation technique being investigated for use in chiral separations. CEC is a hybrid of HPLC and CE. CEC combines the electrophoretic mobility of CE with the partitioning mechanisms of HPLC. In this overview, several resolution mechanisms commonly used in CEC and the main parameters influencing the selectivity of the chiral separation will be discussed. Current applications of CEC in chiral separations of pharmaceuticals will be provided for each type of resolution mechanism. Finally, the advantages and limitations of CEC will be described, followed by the future outlook for CEC.
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Dix DJ, Allen JW, Collins BW, Poorman-Allen P, Mori C, Blizard DR, Brown PR, Goulding EH, Strong BD, Eddy EM. HSP70-2 is required for desynapsis of synaptonemal complexes during meiotic prophase in juvenile and adult mouse spermatocytes. Development 1997; 124:4595-603. [PMID: 9409676 DOI: 10.1242/dev.124.22.4595] [Citation(s) in RCA: 158] [Impact Index Per Article: 5.9] [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: 11/20/2022]
Abstract
Spermatogenic cells synthesize a unique 70-kDa heat shock protein (HSP70-2) during prophase of meiosis I, and targeted disruption of the Hsp70-2 gene has shown that this protein is required for spermatogenic cell differentiation in adult mice. HSP70-2 is associated with synaptonemal complexes formed between paired homologous chromosomes during meiotic prophase. The present study focuses on the nearly synchronous first wave of spermatogenesis in 12- to 28-day old juvenile mice to determine more precisely when HSP70-2 is required and what meiotic processes are affected by its absence. Spermatogenesis in homozygous mutant mice (Hsp70-2[−/−]) proceeded normally until day 15 when increasing numbers of pachytene spermatocytes became apoptotic and differentiation of cells beyond the pachytene stage began to falter. Synaptonemal complexes assembled in Hsp70-2(−/−) mice and spermatocytes developed through the final pachytene substage. However, synaptonemal complexes failed to desynapse and normal diplotene spermatocytes were not observed. Metaphase spermatocytes were not seen in tissue sections from testes of Hsp70-2(−/−) mice, and expression of mRNAs and antigens characteristic of late pachytene spermatocytes (e.g., cyclin A1) and development of spermatids did not occur. Thus, HSP70-2 is required for synaptonemal complex desynapsis, and its absence severely impairs the transition of spermatogenic cells through the late meiotic stages and results in apoptosis beginning with the first wave of germ cell development in juvenile mice.
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Affiliation(s)
- D J Dix
- Reproductive Toxicology Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA
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