| 1. |
- Nabavi Zadeh, Pegah Sadat, 1986, et al.
(författare)
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Förster Resonance Energy Transfer Study of the Improved Biocatalytic Conversion of CO2 to Formaldehyde by Coimmobilization of Enzymes in Siliceous Mesostructured Cellular Foams
- 2018
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 8:8, s. 7251-7260
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Tidskriftsartikel (refereegranskat)abstract
- By combining two enzymes, formate dehydrogenase (FateDH) and formaldehyde dehydrogenase (FaldDH), it is possible to drive the thermodynamically unfavorable conversion of CO2to formaldehyde. For this purpose, the enzymes were coimmobilized in siliceous mesostructured cellular foams (MCFs). A high degree of adsorption of both enzymes was achieved by coimmobilizing the enzymes sequentially, i.e., first FateDH and then FaldDH. The highest conversion rate was obtained with an enzyme mass ratio of 1:15 (FateDH/FaldDH). Using MCF functionalized with mercaptopropyl groups (MCF-MP), the activity increased ∼4 times compared to the enzymes free in solution. To probe the distance between the two enzymes, they were separately labeled with either Cy3 or Cy5 dyes and studied with Förster resonance energy transfer (FRET). An increased energy transfer was observed when the enzymes were coimmobilized in MCF-MP, suggesting that the two enzymes are in close proximity, resulting in higher conversion of CO2to formaldehyde.
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| 2. |
- Nabavi Zadeh, Pegah Sadat, 1986, et al.
(författare)
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Measuring viscosity inside mesoporous silica using protein-bound molecular rotor probe
- 2018
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 20:36, s. 23202-23213
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescence spectroscopy of protein-bound molecular rotors Cy3 and Cy5 is used to monitor the effective viscosity inside the pores of two types of mesoporous silica (SBA-15 and MCF) with pore diameters between 8.9 and 33 nm. The ratio of the peak intensities is used to measure viscosity independently of solvent polarity, and the response of the lipase-bound dyes is calibrated using glycerol/water mixtures (no particles). The two dyes are either attached to the same protein or separate proteins in order to investigate potential effects of energy transfer (FRET) on the fluorescence properties, when using them as reporter dyes. The effective viscosity inside the pores at infinite protein dilution is one order of magnitude higher than in bulk water, and the effect of protein concentration on the measured viscosity indicates a stronger effect of protein–protein interactions in the pores than in similarly concentrated protein solutions without particles. In MCF-particles with octyl-groups covalently attached to the pore walls, a more efficient uptake of the lipase resulted in FRET between the protein-bound dyes even if the two dyes were attached to different proteins. In contrast to the unmodified particles the intensity-ratio method could therefore not be used to measure the viscosity, but the presence of FRET in itself indicates that octyl–protein interactions lead to a non-homogenous protein distribution in the pores. The dye labels also report a less polar pore environment as sensed by the proteins through a redshift in the dye emission. Both observations may help in understanding the higher efficiency of lipase immobilization in octyl-modified particles.
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| 3. |
- Zezzi Do Valle Gomes, Milene, 1987, et al.
(författare)
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Improved biocatalytic cascade conversion of CO2 to methanol by enzymes Co-immobilized in tailored siliceous mesostructured cellular foams
- 2021
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Ingår i: Catalysis Science and Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 11:21, s. 6952-6959
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Tidskriftsartikel (refereegranskat)abstract
- CO2 can be enzymatically reduced to methanol in a cascade reaction involving three enzymes: formate-, formaldehyde- and alcohol dehydrogenase (FateDH, FaldDH, ADH). We report an improvement in the yield of this reaction by co-immobilizing the three dehydrogenases in siliceous mesostructured cellular foams (MCF). This material consists of large mesopores suitable for the co-immobilization of these comparatively large enzymes. To improve the interaction between the enzymes and support, the host silica material was functionalized with mercaptopropyl groups (MCF-MP). The enzymes were fluorescently labelled to independently monitor their uptake and spatial distribution into the particle. The three dehydrogenases were co-immobilized using two sequential methods. In the first one, the enzymes were immobilized according to the reaction order (FateDH -> FaldDH -> ADH) and secondly in order of increasing enzyme size (FateDH -> ADH -> FaldDH). Two protein loadings were also tested: 50 and 150 mg(enzymes) g(support)(-1). We could observe a 4.5-fold higher methanol yield in comparison to enzymes free in solution when the enzymes were immobilized in order of size and with a loading of 50 mg(enzymes) g(support)(-1). The results of this work show that by using MCF-MP, a simple method of immobilization can be applied to significantly increase the activity of the enzymes for the cascade reaction.
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| 4. |
- Zezzi Do Valle Gomes, Milene, 1987, et al.
(författare)
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Spatial Distribution of Enzymes Immobilized in Mesoporous Silicas for Biocatalysis
- 2019
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 2:11, s. 7245-7254
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Tidskriftsartikel (refereegranskat)abstract
- Mesoporous silica (MPS) particles are promising materials for the immobilization of a variety of enzymes due to the possibility of tailoring their morphology and surface properties. A better understanding of the spatial distribution of enzymes immobilized in these materials is important for improved biocatalytic applications. In this work three types of MPS materials are compared for the immobilization of alcohol dehydrogenase (ADH): two ordered mesoporous silica type SBA-15 particles with 6.8 and 10 nm pore diameters and one mesostructured cellular foam (MCF) with a pore diameter of 26.8 nm and window diameter of 10.7 nm. Nitrogen sorption analysis and transmission electron microscopy (TEM) using immunogold staining (IGS) are used to study the immobilized amount and spatial distribution of ADH in the MPS. In the MCF the mesopore volume occupied by the enzymes measured by nitrogen sorption analysis agrees well with the calculated pore filling, which indicates that the amount of enzyme bound to the external surface is small as supported by TEM imaging showing an essentially even distribution in the MCF particles at least up to 2000 nm from the particle surface. In the case of SBA-15 with 6.8 nm pore size the ADH can enter the pores even though the pore size distribution is smaller than the hydrodynamic size of the protein, but the enzymes only penetrate to about 500 nm from the particle surface. With 10 nm pores the ADH penetrates further into SBA-15 but is still not evenly distributed. MCF can accommodate the largest amount of enzyme per gram of particles and still has a substantial fraction of its mesopore volume available, showing that MCF is a good host for the immobilization of large enzymes such as ADH.
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