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Rocha M, Abreu B, Nunes MS, Freire C, Marques EF. Ternary (molybdenum disulfide/graphene)/carbon nanotube nanocomposites assembled via a facile colloidal electrostatic path as electrocatalysts for the oxygen reduction reaction: Composition and nitrogen-doping play a key role in their performance. J Colloid Interface Sci 2024; 664:1056-1068. [PMID: 38531183 DOI: 10.1016/j.jcis.2024.03.014] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Revised: 02/13/2024] [Accepted: 03/03/2024] [Indexed: 03/28/2024]
Abstract
Nanocomposites have garnered attention for their potential as catalysts in electrochemical reactions vital for technologies like fuel cells, water splitting, and metal-air batteries. This work focuses on developing three-dimensional (3D) nanocomposites through aqueous phase exfoliation, non-covalent functionalization of building blocks with surfactants and polymers, and electrostatic interactions in solution leading to the nanocomposites assembly and organization. By combining molybdenum disulfide (MoS2) layers with graphene nanoplatelets (GnPs) to form a binary 2D composite (MoS2/GnP), and subsequently incorporating multiwalled carbon nanotubes (MWNTs) to create ternary 3D composites, we explore their potential as catalysts for the oxygen reduction reaction (ORR) critical in fuel cells. Characterization techniques such as X-ray photoelectron spectroscopy, scanning electron microscopy, and X-ray diffraction elucidate material composition and structure. Our electrochemical studies reveal insights into the kinetics of the reactions and structure-activity relationships. Both the (MoS2/GnP)-to-MWNT mass ratio and nitrogen-doping of GnPs (N-GnPs) play a key role on the electrocatalytic ORR performance. Notably, the (MoS2/N-GnP)/MWNT material, with a 3:1 mass ratio, exhibits the most effective ORR activity. All catalysts demonstrate good long-term stability and methanol crossover tolerance. This facile fabrication method and observed trends offer avenues for optimizing composite electrocatalysts further.
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Affiliation(s)
- Marcos Rocha
- CIQUP - Centro de Investigação em Química da Universidade do Porto, Institute of Molecular Sciences (IMS), Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, Porto 4169-007, Portugal; REQUIMTE-LAQV, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, Porto 4169-007, Portugal
| | - Bárbara Abreu
- CIQUP - Centro de Investigação em Química da Universidade do Porto, Institute of Molecular Sciences (IMS), Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, Porto 4169-007, Portugal; REQUIMTE-LAQV, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, Porto 4169-007, Portugal
| | - Marta S Nunes
- REQUIMTE-LAQV, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, Porto 4169-007, Portugal.
| | - Cristina Freire
- REQUIMTE-LAQV, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, Porto 4169-007, Portugal
| | - Eduardo F Marques
- CIQUP - Centro de Investigação em Química da Universidade do Porto, Institute of Molecular Sciences (IMS), Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, Porto 4169-007, Portugal.
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Bravo A, Nascimento C, Abreu B, Revés J, Morão B, Frias-Gomes C, Canhoto M, Glória L, Fidalgo C. 1278P How do hospitalized patients with chronic liver disease, with and without hepatocellular carcinoma, die? End-of-life quality analysis. Ann Oncol 2022. [DOI: 10.1016/j.annonc.2022.07.1411] [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: 11/01/2022] Open
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Abreu B, Almeida B, Ferreira P, M. F. Fernandes R, Fernandes DM, Marques EF. A critical assessment of the role of ionic surfactants in the exfoliation and stabilization of 2D nanosheets: the case of the transition metal dichalcogenides MoS2, WS2 and MoSe2. J Colloid Interface Sci 2022; 626:167-177. [DOI: 10.1016/j.jcis.2022.06.097] [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] [Received: 03/28/2022] [Revised: 06/13/2022] [Accepted: 06/21/2022] [Indexed: 10/31/2022]
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Ellul P, Revés J, Abreu B, Chaparro M, Gisbert JP, Allocca M, Fiorino G, Barberio B, Zingone F, Pisani A, Cassar D, Michalopoulos G, Mantzaris G, Koutroubakis I, Karmiris K, Katsanos K, Ďuricova D, Burisch J, Madsen GR, Maaser C, Arebi N, Orfanoudaki E, Milivojevic V, Buisson A, Avedano L, Leone S, Torres J. Implementation and Short-term Adverse Events of Anti-SARS-CoV-2 Vaccines in Inflammatory Bowel Disease Patients: An International Web-based Survey. J Crohns Colitis 2022; 16:1070-1078. [PMID: 35037033 PMCID: PMC8807305 DOI: 10.1093/ecco-jcc/jjac010] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 12/06/2021] [Accepted: 01/13/2022] [Indexed: 12/12/2022]
Abstract
INTRODUCTION Anti-SARS-CoV-2 vaccine clinical trials did not include patients with immune-mediated conditions such as inflammatory bowel disease [IBD]. We aimed to describe the implementation of anti-SARS-CoV-2 vaccination among IBD patients, patients' concerns, and the side effect profile of the anti-SARS-CoV-2 vaccines, using real-world data. METHODS An anonymous web-based self-completed survey was distributed in 36 European countries between June and July 2021. The results of the patient characteristics, concerns, vaccination status, and side effect profile were analysed. RESULTS In all 3272 IBD patients completed the survey, 79.6% had received at least one dose of anti-SARS-CoV-2 vaccine, and 71.7% had completed the vaccination process. Patients over 60 years old had a significantly higher rate of vaccination [p < 0.001]. Patients' main concerns before vaccination were the possibility of having worse vaccine-related adverse events due to their IBD [24.6%], an IBD flare after vaccination [21.1%], and reduced vaccine efficacy due to IBD or associated immunosuppression [17.6%]. After the first dose of the vaccine, 72.4% had local symptoms and 51.4% had systemic symptoms [five patients had non-specified thrombosis]. Adverse events were less frequent after the second dose of the vaccine and in older patients. Only a minority of the patients were hospitalised [0.3%], needed a consultation [3.6%], or had to change IBD therapy [13.4%] after anti-SARS-CoV-2 vaccination. CONCLUSIONS Although IBD patients raised concerns about the safety and efficacy of anti-SARS-CoV-2 vaccines, the implementation of vaccination in those responding to our survey was high and the adverse events were comparable to the general population, with minimal impact on their IBD.
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Affiliation(s)
- Pierre Ellul
- Corresponding author: Pierre Ellul, MD PhD Division of GastroenterologyMater Dei Hospital, Msida, Malta
| | - Joana Revés
- Gastroenterology Division, Surgical Department, Hospital Beatriz Ângelo, Loures, Portugal
| | - Bárbara Abreu
- Gastroenterology Division, Surgical Department, Hospital Beatriz Ângelo, Loures, Portugal
| | - María Chaparro
- Gastroenterology Unit, Hospital Universitario de La Princesa, Instituto de Investigación Sanitaria Princesa (IIS-IP), Universidad Autónoma de Madrid (UAM), and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Madrid, Spain
| | - Javier P Gisbert
- Gastroenterology Unit, Hospital Universitario de La Princesa, Instituto de Investigación Sanitaria Princesa (IIS-IP), Universidad Autónoma de Madrid (UAM), and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Madrid, Spain
| | - Mariangela Allocca
- IBD Center, Humanitas Clinical and Research Center, Milan, Italy; Department of Surgery, Oncology and Gastroenterology (DiSCOG), Gastroenterology Unit, University of Padova, Padova, Italy
| | - Gionata Fiorino
- IBD Center, Humanitas Clinical and Research Center, Milan, Italy; Department of Surgery, Oncology and Gastroenterology (DiSCOG), Gastroenterology Unit, University of Padova, Padova, Italy
| | - Brigida Barberio
- IBD Center, Humanitas Clinical and Research Center, Milan, Italy; Department of Surgery, Oncology and Gastroenterology (DiSCOG), Gastroenterology Unit, University of Padova, Padova, Italy
| | - Fabiana Zingone
- IBD Center, Humanitas Clinical and Research Center, Milan, Italy; Department of Surgery, Oncology and Gastroenterology (DiSCOG), Gastroenterology Unit, University of Padova, Padova, Italy
| | - Anthea Pisani
- Division of Gastroenterology Mater Dei Hospital, Msida, Malta
| | - David Cassar
- Division of Gastroenterology Mater Dei Hospital, Msida, Malta
| | | | | | | | | | | | - Dana Ďuricova
- IBD Clinical and Research Centre, ISCARE, Prague, Czech Republic,Institute of Pharmacology, 1 Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Johan Burisch
- Gastrounit, medical division, Hvidovre Hospital, University of Copenhagen Hvidovre, Denmark,Copenhagen Center for Inflammatory Bowel Disease in Children, Adolescents and Adults, Hvidovre Hospital, University of Copenhagen Hvidovre, Denmark
| | - Gorm Roager Madsen
- Gastrounit, medical division, Hvidovre Hospital, University of Copenhagen Hvidovre, Denmark,Copenhagen Center for Inflammatory Bowel Disease in Children, Adolescents and Adults, Hvidovre Hospital, University of Copenhagen Hvidovre, Denmark
| | | | - Naila Arebi
- St Mark's National Bowel Hospital, London, UK
| | | | - Vladimir Milivojevic
- Clinic for gastroenterology and hepatology, Clinical center of Serbia, School of Medicine, Belgrade, Serbia
| | - Anthony Buisson
- Université Clermont Auvergne, Inserm, CHU Clermont-Ferrand, 3iHP, Service d’Hépato-Gastro Entérologie, Clermont-Ferrand, France,Université Clermont Auvergne, Clermont-Ferrand, France
| | - Luisa Avedano
- The European Federation of Crohn's & Ulcerative Colitis Associations (EFCCA)
| | - Salvo Leone
- The European Federation of Crohn's & Ulcerative Colitis Associations (EFCCA)
| | - Joana Torres
- Gastroenterology Division, Surgical Department, Hospital Beatriz Ângelo, Loures, Portugal,Faculdade de Medicina, Universidade de Lisboa, Portugal
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Alves Z, Abreu B, Ferreira NM, Marques EF, Nunes C, Ferreira P. Enhancing the dispersibility of multiwalled carbon nanotubes within starch-based films by the use of ionic surfactants. Carbohydr Polym 2021; 273:118531. [PMID: 34560944 DOI: 10.1016/j.carbpol.2021.118531] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 07/30/2021] [Accepted: 07/30/2021] [Indexed: 12/26/2022]
Abstract
The incorporation of carbon-based nanomaterials into biopolymer matrix, to provide mechanical reinforcement and to obtain electrically conductive bionanocomposites, requires the homogeneous dispersion of the fillers. Herein, it is investigated the influence of surfactant structures on the dispersibility of multiwalled carbon nanotubes (MWNT) within starch matrix. Three different ionic surfactants, sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromide (CTAB) and sodium cholate (SC), are employed to disperse the MWNT. Films with MWNT-SC show better dispersibility and an increase of about 75% of tensile strength and 60% of Young's modulus compared with films using MWNT-SDS and MWNT-CTAB. Nevertheless, MWNT functionalized with CTAB impart the highest values of antioxidant activity (scavenging activity around 30% in 1.5 h) and electrical conductivity (σ =14.75 S/m) to starch matrix. The properties of starch-based films can be tailored according to the physical adsorption of each surfactant on MWNT surface and/or the interfacial interaction of the surfactant with starch chains.
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Affiliation(s)
- Zélia Alves
- Department of Chemistry, CICECO - Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal; Department of Materials and Ceramic Engineering, CICECO - Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Bárbara Abreu
- CIQUP, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, s/n, P 4169-007 Porto, Portugal
| | - Nuno M Ferreira
- Department of Physics, I3N, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Eduardo F Marques
- CIQUP, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, s/n, P 4169-007 Porto, Portugal
| | - Cláudia Nunes
- Department of Chemistry, CICECO - Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal.
| | - Paula Ferreira
- Department of Materials and Ceramic Engineering, CICECO - Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal.
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Abreu B, Cruz C, Oliveira ASF, Soares CM. ATP hydrolysis and nucleotide exit enhance maltose translocation in the MalFGK 2E importer. Sci Rep 2021; 11:10591. [PMID: 34012037 PMCID: PMC8134467 DOI: 10.1038/s41598-021-89556-y] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 04/27/2021] [Indexed: 02/03/2023] Open
Abstract
ATP binding cassette (ABC) transporters employ ATP hydrolysis to harness substrate translocation across membranes. The Escherichia coli MalFGK2E maltose importer is an example of a type I ABC importer and a model system for this class of ABC transporters. The MalFGK2E importer is responsible for the intake of malto-oligossacharides in E.coli. Despite being extensively studied, little is known about the effect of ATP hydrolysis and nucleotide exit on substrate transport. In this work, we studied this phenomenon using extensive molecular dynamics simulations (MD) along with potential of mean force calculations of maltose transport across the pore, in the pre-hydrolysis, post-hydrolysis and nucleotide-free states. We concluded that ATP hydrolysis and nucleotide exit trigger conformational changes that result in the decrease of energetic barriers to maltose translocation towards the cytoplasm, with a concomitant increase of the energy barrier in the periplasmic side of the pore, contributing for the irreversibility of the process. We also identified key residues that aid in positioning and orientation of maltose, as well as a novel binding pocket for maltose in MalG. Additionally, ATP hydrolysis leads to conformations similar to the nucleotide-free state. This study shows the contribution of ATP hydrolysis and nucleotide exit in the transport cycle, shedding light on ABC type I importer mechanisms.
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Affiliation(s)
- Bárbara Abreu
- grid.10772.330000000121511713ITQB NOVA, Instituto de Tecnologia Química E Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Carlos Cruz
- grid.10772.330000000121511713ITQB NOVA, Instituto de Tecnologia Química E Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - A. Sofia F. Oliveira
- grid.10772.330000000121511713ITQB NOVA, Instituto de Tecnologia Química E Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal ,grid.5337.20000 0004 1936 7603School of Biochemistry and Centre for Computational Chemistry, University of Bristol, Bristol, UK
| | - Cláudio M. Soares
- grid.10772.330000000121511713ITQB NOVA, Instituto de Tecnologia Química E Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
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Abreu B, Lopes EF, Oliveira ASF, Soares CM. F508del disturbs the dynamics of the nucleotide binding domains of CFTR before and after ATP hydrolysis. Proteins 2019; 88:113-126. [PMID: 31298435 DOI: 10.1002/prot.25776] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 06/17/2019] [Accepted: 07/06/2019] [Indexed: 12/20/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) channel is an ion channel responsible for chloride transport in epithelia and it belongs to the class of ABC transporters. The deletion of phenylalanine 508 (F508del) in CFTR is the most common mutation responsible for cystic fibrosis. Little is known about the effect of the mutation in the isolated nucleotide binding domains (NBDs), on dimer dynamics, ATP hydrolysis and even on nucleotide binding. Using molecular dynamics simulations of the human CFTR NBD dimer, we showed that F508del increases, in the prehydrolysis state, the inter-motif distance in both ATP binding sites (ABP) when ATP is bound. Additionally, a decrease in the number of catalytically competent conformations was observed in the presence of F508del. We used the subtraction technique to study the first 300 ps after ATP hydrolysis in the catalytic competent site and found that the F508del dimer evidences lower conformational changes than the wild type. Using longer simulation times, the magnitude of the conformational changes in both forms increases. Nonetheless, the F508del dimer shows lower C-α RMS values in comparison to the wild-type, on the F508del loop, on the residues surrounding the catalytic site and the portion of NBD2 adjacent to ABP1. These results provide evidence that F508del interferes with the NBD dynamics before and after ATP hydrolysis. These findings shed a new light on the effect of F508del on NBD dynamics and reveal a novel mechanism for the influence of F508del on CFTR.
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Affiliation(s)
- Bárbara Abreu
- Protein Modelling Lab, ITQB-NOVA, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Emanuel F Lopes
- Protein Modelling Lab, ITQB-NOVA, Universidade Nova de Lisboa, Oeiras, Portugal
| | - A S F Oliveira
- Protein Modelling Lab, ITQB-NOVA, Universidade Nova de Lisboa, Oeiras, Portugal.,School of Biochemistry & Center for Computational Chemistry, University of Bristol, Bristol, UK
| | - Cláudio M Soares
- Protein Modelling Lab, ITQB-NOVA, Universidade Nova de Lisboa, Oeiras, Portugal
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Abreu B, Rocha J, Fernandes RMF, Regev O, Furó I, Marques EF. Gemini surfactants as efficient dispersants of multiwalled carbon nanotubes: Interplay of molecular parameters on nanotube dispersibility and debundling. J Colloid Interface Sci 2019; 547:69-77. [PMID: 30939346 DOI: 10.1016/j.jcis.2019.03.082] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 03/18/2019] [Accepted: 03/24/2019] [Indexed: 12/26/2022]
Abstract
Surfactants have been widely employed to debundle, disperse and stabilize carbon nanotubes in aqueous solvents. Yet, a thorough understanding of the dispersing mechanisms at molecular level is still warranted. Herein, we investigated the influence of the molecular structure of gemini surfactants on the dispersibility of multiwalled carbon nanotubes (MWNTs). We used dicationic n-s-n gemini surfactants, varying n and s, the number of alkyl tail and alkyl spacer carbons, respectively; for comparisons, single-tailed surfactant homologues were also studied. Detailed curves of dispersed MWNT concentration vs. surfactant concentration were obtained through a stringently controlled experimental procedure, allowing for molecular insight. The gemini are found to be much more efficient dispersants than their single-tailed homologues, i.e. lower surfactant concentration is needed to attain the maximum dispersed MWNT concentration. In general, the spacer length has a comparatively higher influence on the dispersing efficiency than the tail length. Further, scanning electron microscopy imaging shows a sizeable degree of MWNT debundling by the gemini surfactants in the obtained dispersions. Our observations also point to an adsorption process that does not entail the formation of micelle-like aggregates on the nanotube surface, but rather coverage by individual molecules, among which the ones that seem to be able to adapt best to the nanotube surface provide the highest efficiency. These studies are relevant for the rational design and choice of optimal dispersants for carbon nanomaterials and other similarly water-insoluble materials.
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Affiliation(s)
- Bárbara Abreu
- CIQUP, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
| | - Jessica Rocha
- CIQUP, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
| | - Ricardo M F Fernandes
- CIQUP, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal; Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - Oren Regev
- Department of Chemical Engineering, Ben-Gurion University of the Negev, 84105 Beer-Sheva, Israel; Ilse Katz Institute for Nanotechnology, Ben-Gurion University of the Negev, 84105 Beer-Sheva, Israel
| | - István Furó
- Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - Eduardo F Marques
- CIQUP, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal.
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Kaur H, Abreu B, Akhmetzyanov D, Lakatos-Karoly A, Soares CM, Prisner T, Glaubitz C. Unexplored Nucleotide Binding Modes for the ABC Exporter MsbA. J Am Chem Soc 2018; 140:14112-14125. [PMID: 30289253 DOI: 10.1021/jacs.8b06739] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The ATP-binding cassette (ABC) transporter MsbA is an ATP-driven lipid-A flippase. It belongs to the ABC protein superfamily whose members are characterized by conserved motifs in their nucleotide binding domains (NBDs), which are responsible for ATP hydrolysis. Recently, it was found that MsbA could catalyze a reverse adenylate kinase (rAK)-like reaction in addition to ATP hydrolysis. Both reactions are connected and mediated by the same conserved NBD domains. Here, the structural foundations underlying the nucleotide binding to MsbA were therefore explored using a concerted approach based on conventional- and DNP-enhanced solid-state NMR, pulsed-EPR, and MD simulations. MsbA reconstituted into lipid bilayers was trapped in various catalytic states corresponding to intermediates of the coupled ATPase-rAK mechanism. The analysis of nucleotide-binding dependent chemical shift changes, and the detection of through-space contacts between bound nucleotides and MsbA within these states provides evidence for an additional nucleotide-binding site in close proximity to the Q-loop and the His-Switch. By replacing Mg2+ with Mn2+ and employing pulsed EPR spectroscopy, evidence is provided that this newly found nucleotide binding site does not interfere with the coordination of the required metal ion. Molecular dynamic (MD) simulations of nucleotide and metal binding required for the coupled ATPase-rAK mechanism have been used to corroborate these experimental findings and provide additional insight into nucleotide location, orientation, and possible binding modes.
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Affiliation(s)
- Hundeep Kaur
- Institute for Biophysical Chemistry & Centre for Biomolecular Magnetic Resonance , Goethe-University Frankfurt , 60438 Frankfurt , Germany
| | - Bárbara Abreu
- ITQB NOVA, Instituto de Tecnologia Química e Biológica António Xavier , Universidade Nova de Lisboa , 2780-157 Oeiras , Portugal
| | - Dmitry Akhmetzyanov
- Institute for Physical and Theoretical Chemistry & Centre for Biomolecular Magnetic Resonance , Goethe-University Frankfurt , 60438 Frankfurt , Germany
| | - Andrea Lakatos-Karoly
- Institute for Biophysical Chemistry & Centre for Biomolecular Magnetic Resonance , Goethe-University Frankfurt , 60438 Frankfurt , Germany
| | - Cláudio M Soares
- ITQB NOVA, Instituto de Tecnologia Química e Biológica António Xavier , Universidade Nova de Lisboa , 2780-157 Oeiras , Portugal
| | - Thomas Prisner
- Institute for Physical and Theoretical Chemistry & Centre for Biomolecular Magnetic Resonance , Goethe-University Frankfurt , 60438 Frankfurt , Germany
| | - Clemens Glaubitz
- Institute for Biophysical Chemistry & Centre for Biomolecular Magnetic Resonance , Goethe-University Frankfurt , 60438 Frankfurt , Germany
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Fernandes RMF, Abreu B, Claro B, Buzaglo M, Regev O, Furó I, Marques EF. Dispersing Carbon Nanotubes with Ionic Surfactants under Controlled Conditions: Comparisons and Insight. Langmuir 2015; 31:10955-65. [PMID: 26390187 DOI: 10.1021/acs.langmuir.5b02050] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A fundamental understanding of the mechanisms involved in the surfactant-assisted exfoliation and dispersion of carbon nanotubes (CNTs) in water calls for well-controlled experimental methodologies and reliable comparative metrics. We have assessed the ability of several ionic surfactants to disperse single and multiwalled carbon nanotubes, resorting to a stringently controlled sonication-centrifugation method for the preparation of the dispersions. The CNT concentration was accurately measured for a wide range of surfactant concentration, using combined thermogravimetric analysis and UV-vis spectroscopy. The obtained dispersibility curves yield several quantitative parameters, which in turn allow for the effects of nanotube morphology and surfactant properties (aromatic rings, chain length, headgroup charge, and cmc) to be assessed and rationalized, both in terms of dispersed nanotube mass and surface area. The data also indicate that the CNT-surfactant association follows patterns that are markedly different from other equilibrium processes governed by hydrophobicity (such as micellization); in particular, the surfactant concentration needed for maximum dispersibility, c(s,max), and the number of surfactant molecules per unit CNT area at c(s,max) are shown to depend linearly on chain length. The results further suggest that the presence of micelles in the exfoliation process is not a key factor either for starting CNT dispersibility or attaining its saturation value.
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Affiliation(s)
- Ricardo M F Fernandes
- Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto , Rua do Campo Alegre, s/n, P-4169-007 Porto, Portugal
- Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology , SE-10044 Stockholm, Sweden
| | - Bárbara Abreu
- Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto , Rua do Campo Alegre, s/n, P-4169-007 Porto, Portugal
| | - Bárbara Claro
- Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto , Rua do Campo Alegre, s/n, P-4169-007 Porto, Portugal
| | | | | | - István Furó
- Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology , SE-10044 Stockholm, Sweden
| | - Eduardo F Marques
- Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto , Rua do Campo Alegre, s/n, P-4169-007 Porto, Portugal
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Sousa CF, Ferreira M, Abreu B, Medforth CJ, Gameiro P. Interactions of a non-fluorescent fluoroquinolone with biological membrane models: A multi-technique approach. Int J Pharm 2015; 495:761-70. [PMID: 26392242 DOI: 10.1016/j.ijpharm.2015.09.037] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2015] [Revised: 09/15/2015] [Accepted: 09/16/2015] [Indexed: 11/30/2022]
Abstract
Fluoroquinolones are antibiotics which act by penetrating into bacterial cells and inhibiting enzymes related to DNA replication, and metal complexes of these drugs have recently been investigated as one approach to counteracting bacterial resistance. In this work, we apply a multi-technique approach to studying the partition coefficient (Kp) for the non-fluorescent third-generation fluoroquinolone sparfloxacin or its copper-complex with lipid membrane models of Gram-negative bacteria. The techniques investigated are UV-vis absorption and (19)F NMR spectroscopies together with quenching of a fluorescent probe present in the lipids (using steady-state and time-resolved methods). (19)F NMR spectroscopy has previously been used to determine the Kp values of fluorinated drugs but in the case of sparfloxacin did not yield useful data. However, similar Kp values for sparfloxacin or its copper-complex were obtained for the absorption and fluorescence quenching methods confirming the usefulness of a multi-technique approach. The Kp values measured for sparfloxacin were significantly higher than those found for other fluoroquinolones. In addition, similar Kp values were found for sparfloxacin and copper-complex suggesting that in contrast to other fluoroquinolones hydrophobic diffusion occurs readily for both of these molecules.
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Affiliation(s)
- Carla F Sousa
- Requimte/UCIBIO, Departmento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Portugal
| | - Mariana Ferreira
- Requimte/UCIBIO, Departmento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Portugal
| | - Bárbara Abreu
- Requimte/UCIBIO, Departmento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Portugal
| | - Craig J Medforth
- Requimte/UCIBIO, Departmento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Portugal
| | - Paula Gameiro
- Requimte/UCIBIO, Departmento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Portugal.
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Sherwin E, Whiteneck G, Corrigan J, Bedell G, Brown M, Abreu B, Depompei R, Gordon W, Kreutzer J. Domains of a TBI minimal data set: Community reintegration phase. Brain Inj 2009; 20:383-9. [PMID: 16716984 DOI: 10.1080/02699050600663097] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Efforts to establish a minimal data set for the period of community integration after traumatic brain injury (TBI) have been the focus of a working group of leading researchers, clinicians and advocates attending the Galveston Brain Injury Symposium in 2001 and 2002. The purpose of the data set is to increase the consistency and interpretability of TBI research and programme evaluation by providing a common set of measures to document key aspects of community integration. It is intended to be sensitive to intervention, comprehensive, reflect satisfaction and outcome and promote future treatment/therapy. In deciding on the components of a minimal data set, the tri-partite model of outcomes was adopted (initially employed in psychotherapy, adapted to TBI) which focuses on the needs of the individual, society and the health provider. Scales are recommended for the respective components of the model.
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Affiliation(s)
- E Sherwin
- University of Arkansas at Little Rock, AR 72204-1099, USA.
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Christiansen C, Abreu B, Ottenbacher K, Huffman K, Masel B, Culpepper R. Task performance in virtual environments used for cognitive rehabilitation after traumatic brain injury. Arch Phys Med Rehabil 1998; 79:888-92. [PMID: 9710158 DOI: 10.1016/s0003-9993(98)90083-1] [Citation(s) in RCA: 68] [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: 02/08/2023]
Abstract
OBJECTIVE This report describes a reliability study using a prototype computer-simulated virtual environment to assess basic daily living skills in a sample of persons with traumatic brain injury (TBI). The benefits of using virtual reality in training for situations where safety is a factor have been established in defense and industry, but have not been demonstrated in rehabilitation. SUBJECTS Thirty subjects with TBI receiving comprehensive rehabilitation services at a residential facility. METHODS An immersive virtual kitchen was developed in which a meal preparation task involving multiple steps could be performed. The prototype was tested using subjects who completed the task twice within 7 days. RESULTS The stability of performance was estimated using intraclass correlation coefficients (ICCs). The ICC value for total performance based on all steps involved in the meal preparation task was .73. When three items with low variance were removed the ICC improved to .81. Little evidence of vestibular optical side-effects was noted in the subjects tested. CONCLUSION Adequate initial reliability exists to continue development of the environment as an assessment and training prototype for persons with brain injury.
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Affiliation(s)
- C Christiansen
- The University of Texas Medical Branch, Galveston 77555-1028, USA
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Clark F, Zemke R, Frank G, Parham D, Neville-Jan A, Hedricks C, Carson M, Fazio L, Abreu B. Dangers inherent in the partition of occupational therapy and occupational science. Am J Occup Ther 1993; 47:184-6. [PMID: 8470751 DOI: 10.5014/ajot.47.2.184] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Affiliation(s)
- F Clark
- Department of Occupational Therapy, University of Southern California, Los Angeles 90033
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