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| 3. |
- Borisova, Anna, et al.
(författare)
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Sequencing, biochemical characterization, crystal structure and molecular dynamics of cellobiohydrolase Cel7A from Geotrichum candidum 3C
- 2015
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Ingår i: FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 282, s. 4515-4537
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Tidskriftsartikel (refereegranskat)abstract
- The ascomycete Geotrichum candidum is a versatile and efficient decay fungus that is involved, for example, in biodeterioration of compact discs; notably, the 3C strain was previously shown to degrade filter paper and cotton more efficiently than several industrial enzyme preparations. Glycoside hydrolase (GH) family 7 cellobiohydrolases (CBHs) are the primary constituents of industrial cellulase cocktails employed in biomass conversion, and feature tunnel-enclosed active sites that enable processive hydrolytic cleavage of cellulose chains. Understanding the structure-function relationships defining the activity and stability of GH7 CBHs is thus of keen interest. Accordingly, we report the comprehensive characterization of the GH7 CBH secreted by G. candidum (GcaCel7A). The bimodular cellulase consists of a family 1 cellulose-binding module (CBM) and linker connected to a GH7 catalytic domain that shares 64% sequence identity with the archetypal industrial GH7 CBH of Hypocrea jecorina (HjeCel7A). GcaCel7A shows activity on Avicel cellulose similar to HjeCel7A, with less product inhibition, but has a lower temperature optimum (50 degrees C versus 60-65 degrees C, respectively). Five crystal structures, with and without bound thio-oligosaccharides, show conformational diversity of tunnel-enclosing loops, including a form with partial tunnel collapse at subsite -4 not reported previously in GH7. Also, the first O-glycosylation site in a GH7 crystal structure is reported - on a loop where the glycan probably influences loop contacts across the active site and interactions with the cellulose surface. The GcaCel7A structures indicate higher loop flexibility than HjeCel7A, in accordance with sequence modifications. However, GcaCel7A retains small fluctuations in molecular simulations, suggesting high processivity and low endo-initiation probability, similar to HjeCel7A.
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- Mugheri, Abdul Qayoom, et al.
(författare)
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An advanced and efficient Co3O4/C nanocomposite for the oxygen evolution reaction in alkaline media
- 2019
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 9:59, s. 34136-34143
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Tidskriftsartikel (refereegranskat)abstract
- The design of efficient nonprecious catalysts for the hydrogen evolution reaction (HER) or the oxygen evolution reaction (OER) is a necessary, but very challenging task to uplift the water-based economy. In this study, we developed a facile approach to produce porous carbon from the dehydration of sucrose and use it for the preparation of nanocomposites with cobalt oxide (Co3O4). The nanocomposites were studied by the powder X-ray diffraction and scanning electron microscopy techniques, and they exhibited the cubic phase of cobalt oxide and porous structure of carbon. The nanocomposites showed significant OER activity in alkaline media, and the current densities of 10 and 20 mA cm(-2) could be obtained at 1.49 and 1.51 V versus reversible hydrogen electrode (RHE), respectively. The impedance study confirms favorable OER activity on the surface of the prepared nanocomposites. The nanocomposite is cost-effective and can be capitalized in various energy storage technologies.
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- Mugheri, Abdul Qayoom, et al.
(författare)
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Facile efficient earth abundant NiO/C composite electrocatalyst for the oxygen evolution reaction Electronic supplementary information (ESI) available. See DOI: 10.1039/c8ra10472g
- 2019
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Ingår i: RSC Advances. - : ROYAL SOC CHEMISTRY. - 2046-2069. ; 9:10, s. 5701-5710
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Tidskriftsartikel (refereegranskat)abstract
- Due to the increasing energy consumption, designing efficient electrocatalysts for electrochemical water splitting is highly demanded. In this study, we provide a facile approach for the design and fabrication of efficient and stable electrocatalysts through wet chemical methods. The carbon material, obtained by the dehydration of sucrose sugar, provides high surface area for the deposition of NiO nanostructures and the resulting NiO/C catalysts show higher activity towards the OER in alkaline media. During the OER, a composite of NiO with 200 mg C can produce current densities of 10 and 20 mA cm(-2) at a bias of 1.45 V and 1.47 V vs. RHE, respectively. Electrochemical impedance spectroscopy experiments showed the lowest charge transfer resistance and the highest double layer capacitance in the case of the NiO/C composite with 200 mg C. The presence of C for the deposition of NiO nanostructures increases the active centers and consequently a robust electrocatalytic activity is achieved. The obtained results in terms of the low overpotential and small Tafel slope of 55 mV dec(-1) for non-precious catalysts are clear indications for the significant advancement in the field of electrocatalyst design for water splitting. This composite material based on NiO/C is simple and scalable for widespread use in various applications, especially in supercapacitors and lithium-ion batteries.
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| 6. |
- Qayoom Mugheri, Abdul, et al.
(författare)
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Co3O4/ NiO bifunctional electrocatalyst for water splitting
- 2019
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Ingår i: Electrochimica Acta. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0013-4686 .- 1873-3859. ; 306
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Tidskriftsartikel (refereegranskat)abstract
- The development of noble metal free and active bifunctional catalysts for water splitting in alkaline media is highly demanded but very challenging. Herein, synergetic effects developed between two nonprecious metal oxides, Co3O4 and NiO, are reported, with the resulting composite showing promising properties as a catalyst for alkaline water electrolysis. The activity of the composite material towards both the HER and the OER was enhanced and the dynamic potential decreased, as compared with its counterparts. Importantly, low Tafel slopes of 101 and 61 mVdec(-1) are found for the composite catalyst for OER and HER respectively. EIS measurements revealed a decreased impedance response of the composite dominated by the intermediate frequency relaxation, related to the adsorption of intermediates. Moreover, based on the structural features the improved catalytic activity of the composite is also due to high electroactive surface area, swift electron transfer kinetics, and excellent electrical chemical coupling between Co3O4 and NiO. (c) 2019 Elsevier Ltd. All rights reserved.
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| 7. |
- Glasbey, JC, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 8. |
- Bravo, L, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 10. |
- Tabiri, S, et al.
(författare)
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- 2021
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swepub:Mat__t
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