| 1. |
- Adam, Rania E., et al.
(author)
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Graphene-based plasmonic nanocomposites for highly enhanced solar-driven photocatalytic activities
- 2019
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 9:52, s. 30585-30598
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Journal article (peer-reviewed)abstract
- High-efficiency photocatalysts are crucial for the removal of organic pollutants and environmental sustainability. In the present work, we report on a new low-temperature hydrothermal chemical method, assisted by ultrasonication, to synthesize disruptive plasmonic ZnO/graphene/Ag/AgI nanocomposites for solar-driven photocatalysis. The plasmonic nanocomposites were investigated by a wide range of characterization techniques, confirming successful formation of photocatalysts with excellent degradation efficiency. Using Congo red as a model dye molecule, our experimental results demonstrated a photocatalytic reactivity exceeding 90% efficiency after one hour simulated solar irradiation. The significantly enhanced degradation efficiency is attributed to improved electronic properties of the nanocomposites by hybridization of the graphene and to the addition of Ag/AgI which generates a strong surface plasmon resonance effect in the metallic silver further improving the photocatalytic activity and stability under solar irradiation. Scavenger experiments suggest that superoxide and hydroxyl radicals are responsible for the photodegradation of Congo red. Our findings are important for the fundamental understanding of the photocatalytic mechanism of ZnO/graphene/Ag/AgI nanocomposites and can lead to further development of novel efficient photocatalyst materials.
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| 2. |
- Angelico, R., et al.
(author)
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Flow-induced structures observed in a viscoelastic reverse wormlike micellar system by magnetic resonance imaging and NMR velocimetry
- 2016
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:40, s. 33339-33347
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Journal article (peer-reviewed)abstract
- The aim of the present work is to illustrate and discuss an application of rheo-NMR techniques in the investigation of the flow micro-morphology of a rheo-thinning fluid. The viscoelastic material is composed by weakly hydrated nonionic Wormlike Micelles (WM), stabilized by the biocompatible phospholipid in an organic solvent (lecithin organogel). By applying rheo-NMR techniques, such as micro-imaging and flow velocimetry in Couette flow, to lecithin organogels in the concentrated isotropic phase, a new phase nucleating inhomogeneously at the inner rotating cylinder showing periodic fluctuations in space in some cases, has been identified for applied shear rates within the isotropic-nematic stress plateau. On the other hand, evident slippage phenomena have been found in flow regimes consistent with a full shear-induced nematic state. Bulk rheometric investigations executed in oscillatory, steady state and transient mode have been finally carried out to bridge different flow micro-heterogeneities detected by rheo-NMR with a variety of mechanical responses manifested by lecithin WM.
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| 3. |
- Asad Ayoubi, Mehran, et al.
(author)
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Self-assembly of block copolymer-based ionic supramolecules based upon multi-tail amphiphiles
- 2015
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 5:39, s. 31091-31103
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Journal article (peer-reviewed)abstract
- Utilising simple acid-base titration chemistry, a new family of Linear-b-Amphiphilic Comb (L-b-AC) ionic supramolecules [Soft Matter 2013, 9, 1540-1555] featuring multi-tail side-chains have been synthesized and examined by synchrotron SAXS. To three different parent diblock copolymers of poly(styrene)-b-poly( methacrylic acid) PS-b-PMAA multi-tail ammonium side-chains of (C8)(2)-, (C8)(4) -or (C12)(2)-type were attached at various side-chain grafting densities (X), making it possible to separate effects of the details of the AC-block architecture from effects of the overall volume fraction of the AC block. The micro-segregated morphologies of these systems include AC-block filled spherical microdomains in a liquid-like state (SPHLL), AC-block filled hexagonally-packed cylinders (CYL), alternating lamellar microlayers of AC- and L-blocks (LAM) and L-block filled hexagonally-packed cylinders (CYL*). For systems with the same parent diblock copolymer that also carry a constant volume fraction of AC-blocks, an increase in the side-chain length (l(sc)) and/or in the number of alkyl tails at a side-chain branch point (m) result in a microdomain morphology that is either unchanged or changed into one with a less curved interface. For lamellae-forming L-b-AC ionic supramolecules made up of the same parent diblock copolymer, a body of experimental data showing small variations in the repeat distance of the LAM micro-segregated structure (d(LAM)) could be obtained by making appropriate combinations of X, lsc and m. For such lamellae-forming L-b-AC ionic supramolecules, the average of d(LAM) values decreases when l(sc) and/or m increase. For systems with (C12)(2)-type side-chains, the effective Flory-Huggins interaction parameter between L-and AC-blocks chi'(C12)(2)/X was determined at various side-chain grafting densities and it was observed that chi'(C12)(2)/X increases when X is increased.
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| 4. |
- Assarsson, A., et al.
(author)
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Kinetic and thermodynamic study of the interactions between human carbonic anhydrase variants and polystyrene nanoparticles of different size
- 2016
-
In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:42, s. 35868-35874
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Journal article (peer-reviewed)abstract
- The activity and adsorption of three variants of human carbonic anhydrase (HCA) with similar topology but variation in charge and stability were studied in the presence of carboxyl-modified polystyrene nanoparticles of different sizes ranging from 25 nm to 114 nm. The balance of forces driving the adsorption of carbonic anhydrase variants is affected by the physicochemical properties of the protein and the nanoparticle size. All enzymes are totally inhibited upon adsorption due to the transition towards a molten globule like state that lacks enzymatic activity. The size of the particle affects the adsorption of human carbonic anhydrase I and N-terminal truncated human carbonic anhydrase II. Investigations on pH effects indicate that the size of the particle modulates the lateral interactions at the protein layer for these particular variants whose adsorption is mainly driven by electrostatic forces. A third variant, human carbonic anhydrase II, instead shows no strong influence of nanoparticle size which supports an adsorption process mainly driven by the hydrophobic effect.
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| 5. |
- Bagan Navarro, Hector, et al.
(author)
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Synthesis and characterization of epitope-imprinted polymers for purification of human hemoglobin.
- 2017
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In: RSC Advances. - 2046-2069. ; 7:66, s. 41705-41712
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Journal article (peer-reviewed)abstract
- One promising method to prepare protein-selective polymers is the epitope-imprinting approach, where surface-accessible peptides from a target protein are used as templates to create surface-exposed binding sites on molecularly imprinted polymers (MIPs). However, selection of a suitable peptide target is not always straightforward, and synthesis of peptide on a large scale can be costly. In this work, we developed a new approach that can be used to select peptide epitopes on protein surface to be used as templates to prepare protein-selective MIPs. In this case study, human hemoglobin (Hb) was immobilized on silica nanoparticles and then fragmented by tryptic digestion. The particle-supported peptides were then used as templates to synthesize the Hb-selective MIPs, which were obtained after removal of the silica support and the peptides. The MIPs were tested in equilibrium binding experiments to evaluate their protein separation performance. The new surface imprinted MIPs displayed high selectivity for Hb, and was able to separate different variants of Hb from protein mixtures and crude cell extracts.
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| 6. |
- Beech, Jason P, et al.
(author)
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Using symmetry to control viscoelastic waves in pillar arrays
- 2023
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In: RSC Advances. - 2046-2069. ; 13:45, s. 31497-31506
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Journal article (peer-reviewed)abstract
- Solutions of macromolecules exhibit viscoelastic properties and unlike Newtonian fluids, they may break time-reversal symmetry at low Reynolds numbers resulting in elastic turbulence. Furthermore, under some conditions, instead of the chaotic turbulence, the result is large-scale waves in the form of cyclic spatial and temporal concentration variations, as has been shown for macromolecular DNA flowing in microfluidic pillar arrays. We here demonstrate how altering the symmetry of the individual pillars can be used to influence the symmetry of these waves. We control the extent of instabilities in viscoelastic flow by leveraging the effects of the symmetry of the pillars on the waves, demonstrating suppressed viscoelastic fluctuations with relevance for transport and sorting applications, or conversely opening up for enhanced viscoelasticity-mediated mixing. The onset of waves, which changes flow resistance, occurs at different Deborah numbers for flow in different directions through the array of triangular pillars, thus breaking the symmetry of the flow resistance along the device, opening up for using the occurrence of the waves to construct a fluidic diode.
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| 7. |
- Bhakat, Soumendranath
(author)
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Pepsin-like aspartic proteases (PAPs) as model systems for combining biomolecular simulation with biophysical experiments
- 2021
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 11:18, s. 11026-11047
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Research review (peer-reviewed)abstract
- Pepsin-like aspartic proteases (PAPs) are a class of aspartic proteases which shares tremendous structural similarity with human pepsin. One of the key structural features of PAPs is the presence of a β-hairpin motif otherwise known as flap. The biological function of the PAPs is highly dependent on the conformational dynamics of the flap region. In apo PAPs, the conformational dynamics of the flap is dominated by the rotational degrees of freedom associated withχ1 andχ2 angles of conserved Tyr (or Phe in some cases). However it is plausible that dihedral order parameters associated with several other residues might play crucial roles in the conformational dynamics of apo PAPs. Due to their size, complexities associated with conformational dynamics and clinical significance (drug targets for malaria, Alzheimer's diseaseetc.), PAPs provide a challenging testing ground for computational and experimental methods focusing on understanding conformational dynamics and molecular recognition in biomolecules. The opening of the flap region is necessary to accommodate substrate/ligand in the active site of the PAPs. The BIG challenge is to gain atomistic details into how reversible ligand binding/unbinding (molecular recognition) affects the conformational dynamics. Recent reports of kinetics (Ki,Kd) and thermodynamic parameters (ΔH,TΔS, and ΔG) associated with macro-cyclic ligands bound to BACE1 (belongs to PAP family) provide a perfect challenge (how to deal with big ligands with multiple torsional angles and select optimum order parameters to study reversible ligand binding/unbinding) for computational methods to predict binding free energies and kinetics beyond typical test systemse.g.benzamide-trypsin. In this work, i reviewed several order parameters which were proposed to capture the conformational dynamics and molecular recognition in PAPs. I further highlighted how machine learning methods can be used as order parameters in the context of PAPs. I then proposed some open ideas and challenges in the context of molecular simulation and put forward my case on how biophysical experimentse.g.NMR, time-resolved FRETetc.can be used in conjunction with biomolecular simulation to gain complete atomistic insights into the conformational dynamics of PAPs.
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| 8. |
- Bhakat, Soumendranath, et al.
(author)
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Reaching beyond HIV/HCV: nelfinavir as a potential starting point for broad-spectrum protease inhibitors against dengue and chikungunya virus
- 2015
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 5:104, s. 85938-85949
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Journal article (peer-reviewed)abstract
- Drug repurposing or re-profiling has become an effective strategy to identify novel indications for already-approved drugs. In this study, peptidomimetic FDA-approved HIV/HCV inhibitors were explored for their potential to be repurposed for the inhibition of the replication of dengue (DENV) and chikungunya virus (CHIKV) by targeting the NS2B-NS3 and NSP2 protease, respectively. MM/GBSA-based binding free energy results put nelfinavir forward as a potential inhibitor of both dengue and chikungunya virus, which subsequently was further explored in a virus-cell-based assay for both viruses. Nelfinavir showed modest antiviral activity against CHIKV (EC50 = 14 +/- 1 mu M and a selectivity index of 1.6) and was slightly more active against DENV-2 (EC50 = 3.5 +/- 0.4 mu M and a selectivity index of 4.6). Even though the antiviral potency was limited, the fact that some activity was observed in these assays made it worthwhile exploring the potential and properties of nelfinavir as a stepping-stone compound: a more detailed computational analysis was performed to understand the binding mode, interaction, hydrogen bond distance, occupancy and minimum pharmacophoric features. The comprehensive data set that resulted from these analyses may prove to be useful for the development of novel DENV and CHIKV protease inhibitors.
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| 9. |
- Bhattacharyya, Anik, et al.
(author)
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A combined experimental and computational study of supramolecular assemblies in ternary copper(II) complexes with a tetradentate N-4 donor Schiff base and halides
- 2014
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:102, s. 58643-58651
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Journal article (peer-reviewed)abstract
- Three new copper(II) complexes, [Cu(L)(Cl)]ClO4 (1), [Cu(L)(Br)]ClO4 (2) and [Cu(L)(I)]ClO4 (3), have been prepared from a tetradentate symmetrical Schiff base, N,N'-bis-(1-pyridin-2-yl-ethylidene)-propane-1,3-diamine (L), and characterized by elemental analysis, IR and UV-Vis spectroscopy and single-crystal X-ray diffraction studies. Extended supra-molecular networks were generated through different weak noncovalent forces. Density functional theory (DFT) calculations were employed to estimate the contribution of each interaction in the formation of the assembly using several theoretical models. The interplay between the anion-pi and pi-pi interactions is also analyzed and a mutual reinforcement of both interactions is demonstrated. The assignment of the contribution of each interaction and its mutual influence is certainly important to shed light on the delicate mechanism that governs the molecular recognition and crystal packing.
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| 10. |
- Blomfeldt, Thomas O. J., et al.
(author)
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Novel freeze-dried foams from glutenin- and gliadin-rich fractions
- 2012
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 2:16, s. 6617-6627
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Journal article (peer-reviewed)abstract
- This is the first study on freeze-dried foams prepared from glutenin- and gliadin-rich fractions of wheat gluten and blends thereof. It was found that the foam density and stiffness could be controlled by a suitable choice of the glutenin/gliadin ratio. The glutenin-rich samples had the highest foam densities and the density decreased with increasing gliadin content. The compression modulus also decreased with increasing gliadin content, which was explained by the decrease in foam density, a more open porosity and the more aggregated/polymerized structure in the presence of glutenin. IR and SE-HPLC revealed that the least aggregated foams were those consisting only of the gliadin-rich fraction. Confocal laser scanning microscopy revealed the presence of both HMW-glutenin and gliadin (to a certain extent probably resisting the ethanol extraction process) in the glutenin-rich foams. SAXS indicated that the gliadin-rich fraction contributed with weakly correlated protein aggregates with a characteristic distance of 40-43 Å.
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