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2.
ACS Chem Neurosci ; 11(8): 1178-1191, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32207962

RESUMO

The residue lysine 28 (K28) is known to form an important salt bridge that stabilizes the Aß amyloid structure, and acetylation of lysine 28 (K28Ac) slows the Aß42 fibrillization rate but does not affect fibril morphology. On the other hand, acetylation of lysine 16 (K16Ac) residue greatly diminishes the fibrillization property of Aß42 peptide and also affects its toxicity. This is due to the fact that lysine 16 acetylated amyloid beta peptide forms amorphous aggregates instead of amyloid fibrils. This is likely a result of increased hydrophobicity of the K16-A21 region due to K16 acetylation, as confirmed by molecular dynamic simulation studies. The calculated results show that the hydrophobic patches of aggregates from acetylated peptides were different when compared to wild-type (WT) peptide. K16Ac and double acetylated (KKAc) peptide aggregates show significantly higher cytotoxicity compared to the WT or K28Ac peptide aggregates alone. However, the heterogeneous mixture of WT and acetylated Aß42 peptide aggregates exhibited higher free radical formation as well as cytotoxicity, suggesting dynamic interactions between different species could be a critical contributor to Aß pathology.

4.
Med Chem ; 16(2): 256-270, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-30848207

RESUMO

BACKGROUND: The well-known antibacterial agent Triclosan (TCL) that targets bacterial enoylacyl protein reductase has been described to inhibit human fatty acid synthase (FASN) via the enoylacyl reductase domain. A Literature survey indicates that TCL is selectively toxic to cancer cells and furthermore might indeed reduce cancer incidence in vivo. A recent study found that TCL inhibits FASN by acting as an allosteric protein-protein interface (PPI) inhibitor. It induces dimer orientation changes that effect in a downstream reorientation of catalytic residues in the NADPH binding site proposing TCL as a viable scaffold to design a superior molecule that might have more inhibitory potential. This unveils tons of potential interaction space to take advantage of future inhibitor design. OBJECTIVES: Synthesis of TCL mimicking novel diphenyl ether derivatives, biological evaluation as potential antiproliferative agents and molecular docking and molecular dynamics simulation studies. METHODS: A series of novel N-(1-(3-hydroxy-4-phenoxyphenyl)-3-oxo-3-phenylpropyl)acetamides (3a-n) and N-(3(3-hydroxy-4phenoxyphenyl)-3-oxo-1-phenylpropyl) acetamides (6a-n) were designed, synthesized, characterized and evaluated against HepG2, A-549, MCF-7 and Vero cell lines. The induction of antiproliferative activity of selected compounds (3d and 6c) was done by AO/EB (acridine orange/ethidium bromide) nuclear staining method, DNA fragmentation study, and cell cycle analysis was performed by flow cytometry. Molecular docking and dynamics simulation study was also performed. RESULTS: Among the tested compounds, compound 3d was most active (IC50 13.76 ± 0.43 µM) against A-549 cell line. Compounds 3d and 3g were found to be moderately active with IC50 30.56 ± 1.1 µM and 25.05 ± 0.8 µM respectively against MCF-7 cell line. Morphological analysis of A-549 cells treated with 3d and 6c clearly demonstrated the reduction of cell viability and induction of apoptosis. DNA fragmentation was observed as a characteristic of apoptosis in treated cells. Further, cell cycle analysis by flow cytometry confirmed that compounds 3d and 6c significantly arrested the cell cycle at the G0/G1 phase. Molecular docking study demonstrated that these compounds exhibit high affinity for the human fatty acid synthase (hFASN) target. Molecular dynamics simulation study of the most active compound 3d was performed for calculating binding free energies using Molecular Mechanics-Generalized Born Surface Area (MM/GBSA). CONCLUSION: Compound 3d (IC50 13.76 ± 0.43 µM) has been identified as a potential lead molecule for anticancer activity against A-549 cells followed by 3l, 6c, and 3g. Thus, the design of diphenyl ether derivatives with enhanced affinity to the binding site of hER may lead to the discovery of potential anticancer agents.

5.
Mol Divers ; 2019 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-31506871

RESUMO

Diphenyl ether derivatives inhibit mycobacterial cell wall synthesis by inhibiting an enzyme, enoyl-acyl carrier protein reductase (InhA), which catalyses the last step in the fatty acid synthesis cycle of genus Mycobacterium. To select and validate a protein crystal structure of enoyl-acyl carrier protein reductase of Mycobacterium tuberculosis for designing inhibitors using molecular modelling, a cross-docking and correlation study was performed. A series of novel 1-(3-(3-hydroxy-4-phenoxyphenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl) ethan-1-ones were synthesized from this model and screened for their antitubercular activity against M. tuberculosis H37Rv. Compound PYN-8 showed good antitubercular activity on M. tuberculosis H37Rv (MIC = 4-7 µM) and Mycobacterium bovis (% inhibition at 10 µM = 95.91%). Cytotoxicity of all the synthesized derivatives was assessed using various cell lines, and they were found to be safe. Structure of PYN-8 was also confirmed by single-crystal X-ray diffraction. The molecular modelling studies also corroborated the biological activity of the compounds. Further, in silico findings revealed that all these tested compounds exhibited good ADME properties and drug likeness and thus may be considered as potential candidates for further drug development.

6.
Mater Sci Eng C Mater Biol Appl ; 104: 109886, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31500014

RESUMO

Common approaches for DNA mutation detection are high cost and have difficult or complex procedure. We propose a fast quantitative method for recognition of DNA mutation based on SWNT/DNA self-assembled nanostructure. Covalent SWNT/DNA hybrid nanostructures are widely used in the fabrication of electrochemical biosensors. Interfacing carbon nanotubes with DNA in particular, is used as a detection method for the analysis of genetic disorders or the detection of mismatches in DNA hybridisation. We have designed a self-assembled, branch-shaped hybrid nanostructure by hybridisation of two sticky oligos that are attached to the ends of SWNTs via a linker oligo. These hybrid nanostructures showed a good conductivity that was greater than free SWNTs. Impedance spectroscopy studies illustrated that the conductivity of these hybrid nanostructures depended on the conformation and structure of the hybridised DNA. We demonstrated that the strategy of using SWNT/DNA self-assembled hybrid nanostructure fabrication yields sensitive and selective tools to discriminate mismatches in DNA. Cyclic voltammetry (CV) and impedance spectroscopy clearly revealed that the conductivity of the branch-shaped and hierarchical hybridised SWNT/DNA nanostructure is higher when matched, than when mismatched in a 1 and 1' hybridised SWNT/DNA nanostructure. Rapid biosensing of match and mismatch nanostructure based on carbon printed electrode showed similar results which can be used for rapid and fast detection of DNA mismatch.


Assuntos
DNA/química , Nanoestruturas/química , Nanotubos de Carbono/química , Técnicas Biossensoriais/métodos , Espectroscopia Dielétrica/métodos , Condutividade Elétrica , Técnicas Eletroquímicas/métodos , Eletrodos
7.
Mater Sci Eng C Mater Biol Appl ; 103: 109733, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31349519

RESUMO

Helicobacter pylori (H. pylori) immunosensor based on platinum nanoparticles/poly(3,4-ethylenedioxythiophene)/reduced graphene oxide (Ptnano/PEDOT/red-GOx) modified gold electrode (Au-ET) was stepwise fabricated for the detection of cytotoxin-associated gene A antibody (CagA antibody). H. pylori is a microaerophillic and a Gram-negative bacteria that causes gastric ulcer leading eventually to adenocarcinoma (gastric cancer) in the later stage. H. pylori colonizes inner lining of human stomach. The developed diagnostic sensing interface would allow H. pylori (stomach infection) detection in early stage and would be a great contribution in clinical laboratories. In order to fabricate the immunosensor, CagA antigen was immobilized over the Ptnano/PEDOT/red-GOx modified Au-ET. Afterwards, the modified electrode was used for immuno-sensing of H. pylori specific Cag A antibodies in serum. At lower voltage the modified Ptnano/PEDOT/red-GOx/Au-ET shows an amplified sensing at the interface that makes the sensor more sensitive and specific. CagA is a virulence factor produced by H. pylori was determined by sudden decrease in the current. The laboratory synthesized nano composites were characterised by Scanning Electron Microscopy (SEM) and Atomic force microscopy (AFM) studies. The sensor had excellent linear range of 0.1 ng/ml to 30 ng/ml by limiting the detection range up to 0.1 ng/ml. Moreover, the novel immunosensor formed had good accuracy, precision and reliability. The immunosensor also showed an excellent storage stability by retaining 60-70% of its initial activity until 60 days kept at 4 °C. Highly sensitive interface of CagA antigen@Ptnano/PEDOT/red-GOx/Au-ET shows a promising future for H. pylori detection in diagnosis of stomach ulcer and stomach cancer.


Assuntos
Anticorpos Antibacterianos , Antígenos de Bactérias , Proteínas de Bactérias , Compostos Bicíclicos Heterocíclicos com Pontes/química , Materiais Revestidos Biocompatíveis/química , Técnicas Eletroquímicas , Infecções por Helicobacter , Helicobacter pylori , Nanocompostos/química , Platina/química , Polímeros/química , Anticorpos Antibacterianos/sangue , Anticorpos Antibacterianos/imunologia , Antígenos de Bactérias/química , Antígenos de Bactérias/imunologia , Proteínas de Bactérias/química , Proteínas de Bactérias/imunologia , Eletrodos , Infecções por Helicobacter/sangue , Infecções por Helicobacter/imunologia , Helicobacter pylori/imunologia , Helicobacter pylori/metabolismo , Humanos , Imunoensaio
8.
Methods ; 168: 40-50, 2019 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-31344405

RESUMO

Sterically hindered fluorescent probes (A-C) have been developed by introducing 2-aminophenylboronic acid pinacol ester to a traditional, A, a near-infrared rhodamine dye, B, and a near-infrared hemicyanine dye, C, forming closed spirolactam ring structures. Probe A was non-fluorescent under basic pH conditions whereas probes B and C were moderately fluorescent with fluorescence quantum yields of 9% and 5% in pH 7.4 PBS buffer containing 1% ethanol, respectively. With all probes increasing acidity leads to significant increases in fluorescence at 580 nm, 644 and 744 nm for probes A, B and C with fluorescence quantum yields of 26%, 21% and 10% in pH 4.5 PBS buffer containing 1% ethanol, respectively. Probes A, B and C were calculated to have pKa values of 5.81, 5.45 and 6.97. The difference in fluorescence under basic conditions is ascribed to easier opening of the closed spirolactam ring configurations due to significant steric hindrance between the 2-aminophenylboronic acid pinacol ester residue and an adjacent H atom in the xanthene derivative moiety in probe B or C. The probes show fast, reversible, selective and sensitive fluorescence responses to pH changes, and are capable of sensing lysosomal pH variations in living cells.

9.
Sci Rep ; 9(1): 7873, 2019 05 27.
Artigo em Inglês | MEDLINE | ID: mdl-31133671

RESUMO

This work deals with first-principles and in silico studies of graphene oxide-based whole-cell selective aptamers for cancer diagnostics utilising a tunable-surface strategy. Herein, graphene oxide (GO) was constructed as a surface-based model with poly(N-isopropylacrylamide) (PNIPAM) covalently grafted as an "on/off"-switch in triggering interactions with the cancer-cell protein around its lower critical solution temperature. The atomic building blocks of the aptamer and the PNIPAM adsorbed onto the GO was investigated at the density functional theory (DFT) level. The presence of the monomer of PNIPAM stabilised the system's π-π interaction between GO and its nucleobases as confirmed by higher bandgap energy, satisfying the eigenvalues of the single-point energy observed rather than the nucleobase and the GO complex independently. The unaltered geometrical structures of the surface emphasise the physisorption type interaction between the nucleobase and the GO/NIPAM surface. The docking result for the aptamer and the protein, highlighted the behavior of the PNIPAM-graft-GO  is exhibiting globular and extended conformations, further supported by molecular dynamics (MD) simulations. These studies enabled a better understanding of the thermal responsive behavior of the polymer-enhanced GO complex for whole-cell protein interactions through computational methods.

10.
Sci Rep ; 9(1): 3133, 2019 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-30816270

RESUMO

Spin thermoelectrics represents a new paradigm of thermoelectricity that has a potential to overcome the fundamental limitation posed by the Wiedmann-Franz law on the efficiency of conventional thermoelectric devices. A typical spin thermoelectric device consists of a bilayer of a magnetic insulator and a high spin-orbit coupling (SOC) metal coated over a non-magnetic substrate. Pt is the most commonly used metal in spin thermoelectric devices due to its strong SOC. In this paper, we found that an alloy of Cu and Pt can perform much better than Pt in spin thermoelectric devices. A series of CuPt alloy films with different Pt concentrations were deposited on yttrium iron garnet (YIG) films coated gadolinium gallium garnet (GGG) substrate. Through spin Seebeck measurements, it was found that the Cu0.4Pt0.6/YIG/GGG device shows almost 3 times higher spin Seebeck voltage compared to Pt/YIG/GGG under identical conditions. The improved performance was attributed to the higher resistivity as well as enhanced spin hall angle of the CuPt layer.

12.
Appl Biochem Biotechnol ; 187(3): 1011-1027, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30151637

RESUMO

Recently conducted human phase- I trials showed protective effect of anti-HIV-1 broadly neutralizing antibodies (bnAbs). The V3 region of the HIV-1 envelope is highly conserved as it is the co-receptor binding site, and is highly immunogenic. Recombinant single-chain antibody fragments (scFvs) can serve as potential tools for construction of chimeric/bispecific antibodies that can target different epitopes on the HIV-1 envelope. Previously, we have constructed a V3 specific human scFv phage recombinant library by a combinational approach of Epstein-Barr virus (EBV) transformation and antigen (V3) preselection, using peripheral blood mononuclear cells (PBMCs), from a subtype C HIV-1 infected antiretroviral naive donor. In the present study, by biopanning this recombinant scFv phage library with V3B (subtype B) and V3C (subtype C) peptides, we identified unique cross reactive anti-V3 scFv monoclonals. These scFvs demonstrated cross-neutralizing activity when tested against subtype A, subtype B, and subtype C viruses. Further, molecular modeling of the anti-V3 scFvs with V3C and V3B peptides predicted their sites of interaction with the scFvs, providing insights for future immunogen design studies. A large collection of such monoclonal antibody fragments with diverse epitope specificities can be useful immunotherapeutic reagents along with antiretroviral drugs to prevent HIV-1 infection and disease progression.


Assuntos
Anticorpos Neutralizantes/imunologia , Antígenos Virais/imunologia , Reações Cruzadas , Proteína gp120 do Envelope de HIV/imunologia , HIV-1/imunologia , Fragmentos de Peptídeos/imunologia , Biblioteca de Peptídeos , Anticorpos de Cadeia Única/imunologia , Sequência de Aminoácidos , Anticorpos Neutralizantes/química , Anticorpos Neutralizantes/isolamento & purificação , Antígenos Virais/química , Proteína gp120 do Envelope de HIV/química , Simulação de Acoplamento Molecular , Fragmentos de Peptídeos/química , Conformação Proteica , Anticorpos de Cadeia Única/química , Anticorpos de Cadeia Única/isolamento & purificação
14.
Immunol Res ; 66(4): 503-512, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29931558

RESUMO

Typhoid fever caused by human restricted Salmonella typhi presents a considerable health burden on developing South-Asian nations like India. The suboptimal sensitivity and specificity associated with culture-based isolation of etiological agent and the extensively used surface antigen-based serological assays often lead to misdiagnosis and inappropriate antimicrobial treatment. The increasing reports of the emergence of resistant strains and undefined disease burden signify the critical need for an inexpensive, reliable, easy-to-use, and highly sensitive diagnostic test for typhoid fever. Utilizing S. typhi-specific and immunogenic antigens in sero-diagnostic assays could lead to precise diagnosis of acute typhoid and prompt treatment. In this study, we report cloning, expression, and purification of recombinant Cytolethal distending toxin subunit B (CdtB) of S. typhi, which is reported to be highly specific, immunogenic, and expressed only upon S. typhi infection. We further evaluated the purified recombinant CdtB for its diagnostic potential in an IgM-based indirect ELISA format using 33 human samples. Twenty-one serum samples from blood culture confirmed cases (n = 21) of typhoid and 12 samples from healthy controls (n = 12) were tested. The assay showed sensitivity of 100% and specificity of 83.3% respectively with positive and negative predictive values of 91.3 and 100% respectively. Efficient detection of specific IgM antibodies indicates that CdtB could be highly valuable in sero-diagnosis of acute typhoid and rapid screening of clinical samples.


Assuntos
Proteínas de Bactérias/genética , Toxinas Bacterianas/genética , Salmonella typhi/fisiologia , Febre Tifoide/diagnóstico , Anticorpos Antibacterianos/sangue , Proteínas de Bactérias/imunologia , Toxinas Bacterianas/imunologia , Clonagem Molecular , Ensaio de Imunoadsorção Enzimática , Humanos , Imunoglobulina M/sangue , Índia , Programas de Rastreamento , Valor Preditivo dos Testes , Proteínas Recombinantes/genética , Sensibilidade e Especificidade , Testes Sorológicos
16.
ACS Appl Bio Mater ; 1(3): 549-560, 2018 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-30906925

RESUMO

Two near-infrared luminescent probes with Stokes-shift and single-photon anti-Stokes-shift fluorescence properties for sensitive determination of pH variance in lysosomes have been synthesized. A morpholine residue in probe A which serves as a targeting group for lysosomes in viable cells was attached to the fluorophores via a spirolactam moiety while a mannose residue was ligated to probe B resulting in increased biocompatibility and solubility in water. Probes A and B contain closed spirolactam moieties, and show no Stokes-shift or anti-Stokes-shift fluorescence under neutral or alkali conditions. However, the probes incrementally react to pH variance from 7.22 to 2.76 with measurable increases in both Stokes-shift and anti-Stokes-shift fluorescence at 699 nm and 693 nm under 645 nm and 800 nm excitation, respectively. This acid-activated fluorescence is produced by the breaking of the probe spirolactam moiety, which greatly increased overall π-conjugation in the probes. These probes possess upconversion near-infrared fluorescence imaging advantages including minimum cellular photo-damage, tissue penetration, and minimum biological fluorescence background. They display excellent photostability with low dye photobleaching and show good biocompatibility. They are selective and capable of detecting pH variances in lysosomes at excitation with two different wavelengths, i.e., 645 and 800 nm.

17.
Sensors (Basel) ; 17(12)2017 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-29182539

RESUMO

Magnetic materials with perpendicular magnetic anisotropy (PMA) have wide-ranging applications in magnetic recording and sensing devices. Multilayers comprised of ferromagnetic and non-magnetic metals (FM-NM) are interesting materials, as their magnetic anisotropy depends strongly on composition and growth parameters. In this context, (Co/Pd) multilayers have gained huge interest recently due to their robustness and tunable PMA. Here, we report a systematic study of the effect of composition on the magnetic anisotropy of (Co/Pd) multilayers grown by Direct Current (DC) magnetron sputtering. Four different series of (Co/Pd)×10 multilayers with different thicknesses of Co and Pd were examined. Vibrating sample magnetometery was used to determine the magnetic anisotropy of these films. X-ray diffraction and transmission electron microscopy experiments were performed to understand the structural morphology of the films. Our results showed that (Co/Pd)×10 multilayers exhibit PMA when the Co to Pd ratio is less than or equal to 1 and the thickness of Co layers is not more than 5 Å. Maximum effective anisotropy energy is shown by the films with a Co to Pd ratio of 1/3.

18.
Sci Rep ; 7: 44027, 2017 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-28382946

RESUMO

Regeneration of immunosensors is a longstanding challenge. We have developed a re-usable troponin-T (TnT) immunoassay based on localised surface plasmon resonance (LSPR) at gold nanorods (GNR). Thermosensitive poly(N-isopropylacrylamide) (PNIPAAM) was functionalised with anti-TnT to control the affinity interaction with TnT. The LSPR was extremely sensitive to the dielectric constant of the surrounding medium as modulated by antigen binding after 20 min incubation at 37 °C. Computational modelling incorporating molecular docking, molecular dynamics and free energy calculations was used to elucidate the interactions between the various subsystems namely, IgG-antibody (c.f., anti-TnT), PNIPAAM and/or TnT. This study demonstrates a remarkable temperature dependent immuno-interaction due to changes in the PNIPAAM secondary structures, i.e., globular and coil, at above or below the lower critical solution temperature (LCST). A series of concentrations of TnT were measured by correlating the λLSPR shift with relative changes in extinction intensity at the distinct plasmonic maximum (i.e., 832 nm). The magnitude of the red shift in λLSPR was nearly linear with increasing concentration of TnT, over the range 7.6 × 10-15 to 9.1 × 10-4 g/mL. The LSPR based nano-immunoassay could be simply regenerated by switching the polymer conformation and creating a gradient of microenvironments between the two states with a modest change in temperature.


Assuntos
Imunoensaio/métodos , Ressonância de Plasmônio de Superfície/métodos , Troponina T/análise , Resinas Acrílicas/química , Ouro/química , Humanos , Imunoensaio/instrumentação , Simulação de Acoplamento Molecular , Nanotubos , Ressonância de Plasmônio de Superfície/instrumentação , Troponina T/imunologia
19.
Anal Chim Acta ; 968: 97-104, 2017 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-28395779

RESUMO

A novel near-infrared fluorescent probe for ß-galactosidase has been developed based on a hemicyanine skeleton, which is conjugated with a d-galactose residue via a glycosidic bond. The probe serves as a substrate of ß-galactosidase and displays rapid and sensitive turn-on fluorescent responses to ß-galactosidase in aqueous solution. A 12.8-fold enhancement of fluorescence intensity at 703 nm was observed after incubation of 10 nM of ß-galactosidase with 5 µM probe for 10 min. The probe can sensitively detect as little as 0.1 nM of ß-galactosidase and shows linear responses to the enzyme concentration below 1.4 nM. The kinetic study showed that the probe has high binding affinity to ß-galactosidase with Km = 3.6 µM. The probe was used to detect ß-galactosidase in living cells by employing the premature cell senescence model. The probe exhibited strong fluorescent signals in senescent cells but not in normal cells, which demonstrates that the probe is able to detect the endogenous senescence-associated ß-galactosidase in living cells.


Assuntos
Corantes Fluorescentes , Espectroscopia de Luz Próxima ao Infravermelho , beta-Galactosidase/análise , Células Cultivadas , Fibroblastos , Humanos
20.
Sci Rep ; 7: 44621, 2017 03 20.
Artigo em Inglês | MEDLINE | ID: mdl-28317853

RESUMO

The potential of thermoelectric materials to generate electricity from the waste heat can play a key role in achieving a global sustainable energy future. In order to proceed in this direction, it is essential to have thermoelectric materials that are environmentally friendly and exhibit high figure of merit, ZT. Oxide thermoelectric materials are considered ideal for such applications. High thermoelectric performance has been reported in single crystals of Ca3Co4O9. However, for large scale applications single crystals are not suitable and it is essential to develop high-performance polycrystalline thermoelectric materials. In polycrystalline form, Ca3Co4O9 is known to exhibit much weaker thermoelectric response than in single crystal form. Here, we report the observation of enhanced thermoelectric response in polycrystalline Ca3Co4O9 on doping Tb ions in the material. Polycrystalline Ca3-xTbxCo4O9 (x = 0.0-0.7) samples were prepared by a solid-state reaction technique. Samples were thoroughly characterized using several state of the art techniques including XRD, TEM, SEM and XPS. Temperature dependent Seebeck coefficient, electrical resistivity and thermal conductivity measurements were performed. A record ZT of 0.74 at 800 K was observed for Tb doped Ca3Co4O9 which is the highest value observed till date in any polycrystalline sample of this system.

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