| 1. |
- Andreasen, Laura, et al.
(författare)
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Brugada syndrome-associated genetic loci are associated with J-point elevation and an increased risk of cardiac arrest
- 2018
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 9:JUL
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: A previous genome-wide association study found three genetic loci, rs9388451, rs10428132, and rs11708996, to increase the risk of Brugada Syndrome (BrS). Since the effect of these loci in the general population is unknown, we aimed to investigate the effect on electrocardiogram (ECG) parameters and outcomes in the general population. Materials and Methods: A cohort of 6,161 individuals (median age 45 [interquartile range (IQR) 40-50] years, 49% males), with available digital ECGs, was genotyped and subsequently followed for a median period of 13 [IQR 12.6-13.4] years. Data on outcomes were collected from Danish administrative healthcare registries. Furthermore, ~400,000 persons from UK Biobank were investigated for associations between the three loci and cardiac arrest/ventricular fibrillation (VF). Results: Homozygote carriers of the C allele in rs6800541 intronic to SCN10A had a significantly larger J-point elevation (JPE) compared with wildtype carriers (11 vs. 6 μV, P < 0.001). There was an additive effect of carrying multiple BrS-associated risk alleles with an increased JPE in lead V1. None of the BrS-associated genetic loci predisposed to syncope, atrial fibrillation, or total mortality in the general Danish population. The rs9388451 genetic locus adjacent to the HEY2 gene was associated with cardiac arrest/VF in an analysis using the UK Biobank study (odds ratio = 1.13 (95% confidence interval: 1.08-1.18), P = 0.006). Conclusions: BrS-associated risk alleles increase the JPE in lead V1 in an additive manner, but was not associated with increased mortality or syncope in the general population of Denmark. However, the HEY2 risk allele increased the risk of cardiac arrest/VF in the larger population study of UK Biobank indicating an important role of this common genetic locus.
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| 2. |
- Barauskas, Justas, et al.
(författare)
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Thermomyces lanuginosus lipase-catalyzed hydrolysis of the lipid cubic liquid crystalline nanoparticles
- 2016
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Ingår i: Colloids and Surfaces B. - : Elsevier. - 0927-7765 .- 1873-4367. ; 137, s. 50-59
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Tidskriftsartikel (refereegranskat)abstract
- In this study well-ordered glycerol monooleate (GMO)-based cubic liquid crystalline nanoparticles (LCNPs) have been used as substrates for Thermomyces lanuginosus lipase in order to establish the relation between the catalytic activity, measured by pH-stat titration, and the change in morphology and nano-structure determined by cryogenic transmission electron microscopy and synchrotron small angle X-ray diffraction. The initial lipase catalyzed LCNP hydrolysis rate is approximately 25% higher for large 350 nm nanoparticles compared to the small 190 nm particles, which is attributed to the increased number of structural defects on the particle surface. At pH 8.0 and 8.4 bicontinuous Im3m cubic LCNPs transform into "sponge"-like assemblies and disordered multilamellar onion-like structures upon exposure to lipase. At pH 6.5 and 7.5 lipolysis induced phase transitions of the inner core of the particles, following the sequence Im3m cubic -> reversed hexagonal -> reversed micellar Fd3m cubic -> reversed micelles. These transitions to the liquid crystalline phases with higher negative curvature of the lipid/water interface were found to trigger protonation of the oleic acid produced during lipase catalyzed reaction. The increase curvature of the reversed discrete micellar cubic phase was suggested to cause an increase in the oleic acid pK(a) to a larger value observed by pH-stat titration. (C) 2015 Elsevier B.V. All rights reserved.
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| 3. |
- Brennan, Jennifer L., et al.
(författare)
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Enzymatic Activity of Lipase-Nanoparticle Conjugates and the Digestion of Lipid Liquid Crystalline Assemblies
- 2010
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 26:16, s. 13590-13599
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Tidskriftsartikel (refereegranskat)abstract
- Variants of lipase were attached to gold nanoparticles (NPs) and their enzymatic activity was studied. The two bioengineered lipase variants have been prepared with biotin groups attached to different residues on the protein outer surface. The biotinylation was evidenced by denaturing polyacrylamide gel electrophoresis and quantified by the ([2-(4'-hydroxyazobenzene)]benzoic acid spectrophotometric test. NPs of 14 +/- 1 nm diameter coated with thiolated-polyethylene glycol ligands containing controlled proportions of biotin moieties have been prepared and characterized by transmission electron microscopy, UV-vis spectroscopy, small angle neutron scattering, and elemental analysis. These biotin-functionalized NPs were conjugated to lipase using streptavidin as a linker molecule. Enzyme activity assays on the lipase-nanoparticle conjugates show that the lipase loading and activity of the NPs can be controlled by varying the percentage of biotin groups in the particle protecting coat. The lipase-NP conjugates prepared using one variant display higher activity than those prepared using the other variant, demonstrating orientation-dependent enzyme activity. Cryogenic transmission electron microscopy was used to visualize the enzymatic activity of lipase-NP on well-defined lipid substrates. It was found that lipase-coated NPs are able to digest the substrates in a different manner in comparison to the free lipase.
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| 4. |
- Holmquist, Mats Torsten, et al.
(författare)
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Lipases from Rhizomucor miehei and Humicola lanuginosa : Modification of the lid covering the active site alters enantioselectivity
- 1993
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Ingår i: Journal of Protein Chemistry. - 0277-8033. ; 12:6, s. 749-757
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Tidskriftsartikel (refereegranskat)abstract
- The homologous lipases from Rhizomucor miehei and Humicola lanuginosa showed approximately the same enantioselectivity when 2-methyldecanoic acid esters were used as substrates. Both lipases preferentially hydrolyzed the S- enantiomer of 1-heptyl 2-methyldecanoate (R. miehei: E(S) = 8.5; H. lanuginosa: E(S) = 10.5), but the R-enantiomer of phenyl 2-methyldecanoate (E(R) = 2.9). Chemical arginine specific modification of the R. miehei lipase with 1,2-cyclohexanedione resulted in a decreased enantioselectivity (E(R) = 2.0), only when the phenyl ester was used as a substrate. In contrast, treatment with phenylglyoxal showed a decreased enantioselectivity (E(S) = 2.5) only when the heptyl ester was used as a substrate. The presence of guanidine, an arginine side chain analog, decreased the enantioselectivity with the heptyl ester (E(S) = 1.9) and increased the enantioselectivity with the aromatic ester (E(R) = 4.4) as substrates. The mutation, Glu 87 Ala, in the lid of the H. lanuginosa lipase, which might decrease the electrostatic stabilization of the open-lid conformation of the lipase, resulted in 47% activity compared to the native lipase, in a tributyrin assay. The Glu 87 Ala mutant showed an increased enantioselectivity with the heptyl ester (E(S) = 17.4) and a decreased enantioselectivity with the phenyl ester (E(R) = 2.5) as substrates, compared to native lipase. The enantioselectivities of both lipases in the esterification of 2-methyldecanoic acid with 1-heptanol were unaffected by the lid modifications.
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| 5. |
- Naik, Sangeeta, et al.
(författare)
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Lipases for use in industrial biocatalysis : Specificity of selected structural groups of lipases
- 2010
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Ingår i: Journal of Molecular Catalysis B. - : Elsevier BV. - 1381-1177 .- 1873-3158. ; 65:1-4, s. 18-23
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Tidskriftsartikel (refereegranskat)abstract
- Lipases for biocatalysis The substrate specificity of a selected group of lipases was investigated. The enzymes selected were from four structural groups. Group 1: lipases having wide alcohol binding cleft but a narrow acyl binding cleft (Rhizomucor miehei lipase. Thermomyces lanuginosus lipase. Fusarium oxysporum lipase); Group 2: lipases which exhibit strong restriction on the acid part having a narrow tunnel to accommodate the acyl group but wider alcohol binding site (Candida antarctica A, Candida rugosa lipase); Group 3: lipases having wide acyl binding cleft but narrow alcohol binding cleft (C. antarctica lipase B, Ustilago maydis lipase), and Group 4: having wider alcohol and wider acyl binding clefts (Fusarium solani pisi cutinase, Humicola insolens cutinase). Owing to the wide substrate specificity and higher expression levels in recombinant host, these lipases have tremendous importance for hydrolysis and synthesis reactions. Various substrates with substitutions on the alcohol and/or the acid part of the ester molecule were selected. The experimental results support the classification of lipases on the basis of their binding sites. For substrates with heavy alcohol side, C. Antarctica lipase A and R. miehei lipase type enzymes gave the highest extent of hydrolysis, while for acid heavy substrates the highest conversions were shown by C. antarctica lipase B. It is noteworthy that the acid heavy substrates which had aromatic side chains were hydrolyzed only by C. antarctica lipase B type of enzymes. Lipases were found to be more active on the alcohol-substituted substrates than acid-substituted substrates. (C) 2010 Elsevier B.V. All rights reserved.
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| 6. |
- Skjot, Michael, et al.
(författare)
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Understanding the Plasticity of the alpha/beta Hydrolase Fold : Lid Swapping on the Candida antarctica Lipase B Results in Chimeras with Interesting Biocatalytic Properties
- 2009
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Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 10:3, s. 520-527
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Tidskriftsartikel (refereegranskat)abstract
- The Candida antarctica lipase B (CALB) has found very extensive use in biocatalysis reactions. Long molecular dynamics simulations of CALB in explicit aqueous solvent confirmed the high mobility of the regions lining the channel that leads into the active site, in particular, of helices alpha 5 and alpha 10. The simulation also confirmed the function of helix alpha 5 as a lid of the lipase. Replacing it with corresponding lid regions from the CALB homologues from Neurospora crassa and Gibberella zeae resulted in two new CALB mutants. Characterization of these revealed several interesting properties, including increased hydrolytic activity on simple esters, specifically substrates with C. branching on the carboxylic side, and much increased enantioselectivity in hydrolysis of racemic ethyl 2-phenylpropanoate (E > 50), which is a common structure of the profen drug family.
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| 7. |
- Stamm, Arne, et al.
(författare)
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The triolein/aqueous interface and lipase activity studied by spectroscopic ellipsometry and coarse grained simulations
- 2018
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Ingår i: Chemistry and Physics of Lipids. - : Elsevier BV. - 0009-3084 .- 1873-2941. ; 211, s. 37-43
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Tidskriftsartikel (refereegranskat)abstract
- In spite of the importance of the triglyceride aqueous interface for processes like emulsification, surfactant interactions and lipase activity, relatively little is known about this interface compared to that between alkanes and water. Here, the contact between triolein and water was investigated in terms of water inclusion in the oil phase and orientation of the molecules at the interface. Coarse grained models of triglycerides in contact with water were constructed and correlated with experimental results of the changes in thickness and refractive index, obtained using spectroscopic ellipsometry of spin-coated triolein films. The topography of the layer was revealed by atomic force microscopy. Dry triolein and a triolein sample after equilibration with water were also compared structurally using small-angle X-ray scattering. Additionally, the kinetics of adsorption/activity of three different variants of the Thermomyces lanuginosus lipase (TLL) were investigated. The results show that uptake of water in the triolein phase leads to increase in thickness of the layer. The observed increase of thickness was further enhanced by an active lipase but reduced when an inactive mutant of the enzyme was applied.
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| 8. |
- Svendsen, Allan, et al.
(författare)
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Editorial
- 2018
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Ingår i: Chemistry and Physics of Lipids. - : Elsevier BV. - 0009-3084. ; 211, s. 1-3
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Tidskriftsartikel (refereegranskat)
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| 9. |
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