| 1. |
- Bohlin, Christina, et al.
(författare)
-
Product profiles in enzymic and non-enzymic oxidations of the lignin model compound erythro-1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol
- 2005
-
Ingår i: Journal of Molecular Catalysis - B Enzymatic. - : Elsevier BV. - 1381-1177 .- 1873-3158. ; 35:4-6, s. 100-107
-
Tidskriftsartikel (refereegranskat)abstract
- The erythro form of the lignin model compound 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol (1) was oxidized with laccase/ABTS, lead(IV) tetraacetate (LTA), lignin peroxidase/H2O2, cerium(IV) ammonium nitrate (CAN) and Fenton's reagent. The product profiles obtained with the different oxidants were compared after separation, identification and quantification of the products using HPLC, UV-diode array detector and electrospray ionization mass spectrometry in positive ionization mode. The oxidants generated different product profiles that reflected their different properties. Oxidation with laccase/ABTS resulted almost exclusively in formation of 1-(3,4-dimethoxyphenyl)-3-hydroxy-2-(2-methoxyphenoxy)-1-propanone (2). Oxidation with LTA resulted in more 3,4-dimethoxybenzaldehyde (3) than ketone 2. Lignin peroxidase and CAN gave similar product profiles and aldehyde 3 was the predominant product (only small amounts of ketone 2 were formed). Oxidation with Fenton's reagent resulted in the formation of more aldehyde 3 than ketone 2 but the yields were very low. CAN served as an excellent model for the lignin peroxidase-catalyzed oxidation, while the laccase-mediator system, LTA and Fenton's reagent provided distinctly different product profiles. Erythro-1-(3,4-dimethoxyphenyl)-1,2,3-propanetriol was present among the products obtained on oxidation with LTA, lignin peroxidase, CAN and Fenton's reagent. The differences in redox potential between the oxidants afford an explanation of the diverse product patterns but other factors may also be of importance. The reactions leading to cleavage of the β-ether bond with formation of 1-(3,4-dimethoxyphenyl)-1,2,3-propanetriol (veratrylglycerol) were found to proceed without affecting the configuration at the β-carbon atom.
|
|
| 2. |
|
|
| 3. |
- Bjelosevic, Haris, et al.
(författare)
-
Synthesis and structural characterisation of novel platinum-based drug candidates with extended functionality by incorporation of bis(diphenylphosphino)ferrocene units as metal chelators
- 2006
-
Ingår i: Tetrahedron. - : Elsevier BV. - 0040-4020. ; 62:18, s. 4519-4527
-
Tidskriftsartikel (refereegranskat)abstract
- Among the metal-based anticancer drugs, cisplatin (cis-diaminedichloroplatinum(II)) is the most widely used species in therapy. Despite its clinical success, cisplatin still suffers in generating resistance, as well as being highly toxic due to poor selectivity between healthy and sick cells. By molecular design it ought to be possible to generate new cis-platinum compounds with increased selectivity and improved cellular behaviour. In this paper, we report a synthetic pathway for construction of derivatives of 1,1'-bis(diphenylphosphino)-ferrocene, together with their corresponding cis-platinum compounds with the aim testing them for their interaction capacity with respect to various DNA models. We also report a synthetic route for a nucleoside-based cis-platinum compound containing a bidentate ferrocenylphosphine derivative connected through a succinamic-based linker to the 5-position of the heterocyclic moiety of uridine. Our preliminary kinetic investigation of 5-{N-[1-[1',2-bis(diphenylphosphino)ferrocenyl]ethyl]1-N'-[prop-2-yn-3-y l]succinamide} uridinedichloroplatinum(II) showed that this compound reacted faster with the phosphorothioate containing oligonucleotides d(T(6)p(S)T-6), with an observed first-order rate constant k(obs) = (1.4 +/- 0.1) X 10(-4) s(-1), compared with the G-N7 target in d(T(7)GGT(7)), for which the observed first-order rate constant is k(obs) = (7.2 +/- 0.5) X 10(-4) s(-1). (c) 2006 Elsevier Ltd. All rights reserved.
|
|
| 4. |
- Shleev, Sergey, et al.
(författare)
-
Interaction of fungal laccases and laccase-mediator systems with lignin
- 2006
-
Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229 .- 1879-0909. ; 39:4, s. 841-847
-
Tidskriftsartikel (refereegranskat)abstract
- The interaction between fungal laccases from Trametes basidiomycetes and different lignins has been studied using electrochemical and chromatographic methods. The kinetic parameters for the oxidation reaction of hydroquinone and for Kraft lignin by molecular oxygen catalysed by Trametes hirsuta laccase have been investigated. Polymerisation of lignin by laccase was shown. The process was independent on the source of lignin as well as on the origin and purity of the enzymes. A complex pattern of interaction between the laccase-mediator system (LMS) and lignin was shown. Along with the polymerisation of lignin, the ability to degrade lignin using the LMS was observed. Data generated by combining size exclusion chromatographic separation of lignin with the use of a laccase modified electrode as post column detector, strongly suggest that laccase can oxidise natural lignin by a long-range electron transfer mechanism. The influence of the origin of lignin as well as source of the enzyme on this process was also shown. (c) 2006 Elsevier Inc. All rights reserved.
|
|
| 5. |
- Tasca, Federico, et al.
(författare)
-
Increasing amperometric biosensor sensitivity by length fractionated single-walled carbon nanotubes.
- 2008
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 24:2, s. 272-278
-
Tidskriftsartikel (refereegranskat)abstract
- In this work the sensitivity-increasing effect of single-walled carbon nanotubes (SWCNTs) in amperometric biosensors, depending on their average length distribution, was studied. For this purpose the SWCNTs were oxidatively shortened and subsequently length separated by size exclusion chromatography. Transmission electron micrographs of different fractions of SWCNTs were collected. Diaphorase "wired" to an osmium redox polymer was blended with the shortened SWCNTs of different lengths. Depending on the average length of the SWCNTs the sensitivity of the amperometric biosensor model system towards oxidation of 1,4-dihydronicotinamide adenine dinucleotide (NADH) was increased by a factor of five. The best performance was achieved with SWCNTs of medium length. The linear range for NADH detection was between 5muM and 7mM, the maximum sensitivity was 47nAmuM(-1)cm(-2), and the detection limit was 1muM. The biosensor exhibited excellent electrocatalytic properties. Even at relatively high NADH concentrations the oxidative current was limited by the diffusion rate of NADH.
|
|
| 6. |
- Tkac, Jan, et al.
(författare)
-
Improved selectivity of microbial biosensor using membrane coating. Application to the analysis of ethanol during fermentation
- 2003
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 18:9, s. 1125-1134
-
Tidskriftsartikel (refereegranskat)abstract
- A ferricyanide mediated microbial biosensor for ethanol detection was prepared by surface modification of a glassy carbon electrode. The selectivity of the whole Gluconobacter oxydans cell biosensor for ethanol determination was greatly enhanced by the size exclusion effect of a cellulose acetate (CA) membrane. The use of a CA membrane increased the ethanol to glucose sensitivity ratio by a factor of 58.2 and even the ethanol to glycerol sensitivity ratio by a factor of 7.5 compared with the use of a dialysis membrane. The biosensor provides rapid and sensitive detection of ethanol with a limit of detection of 0.85 µM (S/N=3). The selectivity of the biosensor toward alcohols was better compared to previously published enzyme biosensors based on alcohol oxidase or alcohol dehydrogenases. The biosensor was successfully used in an off-line monitoring of ethanol during batch fermentation by immobilized Saccharomyces cerevisiae cells with an initial glucose concentration of 200 g l-1. © 2002 Elsevier Science B.V. All rights reserved.
|
|
| 7. |
- Tuoriniemi, Jani, 1982, et al.
(författare)
-
Determination of the Distance Between the Cytochrome and Dehydrogenase Domains of Immobilized Cellobiose Dehydrogenase by Using Surface Plasmon Resonance with a Center of Mass Based Model
- 2020
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 92:3, s. 2620-2627
-
Tidskriftsartikel (refereegranskat)abstract
- Changes in the tertiary conformation of adsorbed biomolecules can induce detectable shifts (Delta theta(r)) in the surface plasmon resonance (SPR) angle. Here it is shown how to calculate the corresponding shifts in the adsorbate's center of mass (Delta z(avg)) along the sensing surface normal from the measured Delta theta(r). The novel developed model was used for determining the mean distance between the cytochrome (CYT) and flavodehydrogenase (DH) domains of the enzyme cellobiose dehydrogenase (CDH) isolated from the fungi Neurospora crassa, Corynascus thermophilus, and Myriococcum thermophilum as a function of pH, [Ca2+], and substrate concentration. SPR confirmed the results from earlier electrochemical and SAXS studies stating that the closed conformation, where the two domains are in close vicinity, is stabilized by a lower pH and an increased [Ca2+]. Interestingly, an increasing substrate concentration in the absence of any electron acceptors stabilizes the open conformation as the electrostatic repulsion due to the reaped electrons pushes the DH and CYT domains apart. The accuracy of distance determination was limited mostly by the random fluctuations between replicate measurements, and it was possible to detect movements <1 nm of the domains with respect to each other. The results agreed with calculations using already established models treating conformational changes as contraction or expansion of the thickness of the adsorbate layer (t(protein)). Although the models yielded equivalent results, in this case, the Delta z(avg)-based method also works in situations, where the adsorbate's mass is not evenly distributed within the layer.
|
|
| 8. |
- Bunea, Ada-Ioana, et al.
(författare)
-
Micropatterned Carbon-on-Quartz Electrode Chips for Photocurrent Generation from Thylakoid Membranes
- 2018
-
Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 1:7, s. 3313-3322
-
Tidskriftsartikel (refereegranskat)abstract
- Harvesting the energy generated by photosynthetic organisms through light-dependent reactions is a significant step toward a sustainable future energy supply. Thylakoid membranes are the site of photosynthesis, and thus particularly suited for developing photo-bioelectrochemical cells. Novel electrode materials and geometries could potentially improve the efficiency of energy harvesting using thylakoid membranes. For commercial applications, electrodes with large surface areas are needed. Photolithographic patterning of a photoresist, followed by pyrolysis, is a flexible and fast approach for the fabrication of carbon electrodes with tailored properties. In this work, electrode chips consisting of patterned carbon supported on quartz were designed and fabricated. The patterned electrode area is 1 cm2, and the measurement chamber footprint is 0.5 cm2, 1 order of magnitude larger than previously tested electrodes for thylakoid membrane immobilization. The use of a transparent substrate allows back-side illumination, protecting the bioelectrochemical system from the environment and vice versa. Two different mediators, monomeric ([Ru(NH3)6]3+) and polymeric ([Os(2,2′-bipyridine)2-poly(N-vinylimidazole)10Cl]+/2+), are used for evaluating photocurrent generation from thylakoid membranes with different electrode geometries. Current densities up to 71 μA cm–2 are measured upon illumination through the transparent electrode chip with solar simulated irradiance (1000 W m–2).
|
|
| 9. |
- Moges, G, et al.
(författare)
-
Glutamate oxidase advances the selective bioanalytical detection of the neurotoxic amino acid beta-ODAP in grass pea: A decade of progress
- 2004
-
Ingår i: Pure and Applied Chemistry. - 0033-4545. ; 76:4, s. 765-775
-
Tidskriftsartikel (refereegranskat)abstract
- The search for an enzyme as a reagent for selective bioanalytical detection of the neurotoxic amino acid, beta-N-oxalyl-L-,alpha,beta-diaminopropionic acid, beta-ODAP (found in grass pea, Lathyrus sativus) led to its redox catalytic reaction by glutamate oxidase (GluOx). Homogeneous kinetic studies and an immobilized GluOx reactor-based flow-injection assay were initially made for beta-ODAP with small immobilized GluOx/catalase glutamate-destroying prereactors. The method was applied to examine the toxin content in processed grass pea. The kinetics and the equilibrium of the thermal isomerization of beta-ODAP to the nontoxic isomer alpha-ODAP established that GluOx is specific to the neurotoxin. The first ever GluOx-based amperometric biosensor for liquid chromatography (LC) detection was reported in 1997. This biosensor coupled with a refractive index detector improved LC performance. The most recent work with GluOx resulted in MnO2-based screen-printed amperometric biosensor, with offline elimination of glutamate interference by glutamate decarboxylase. A single-shot chemiluminescent sensor developed for hydrogen peroxide is also proposed for beta-ODAP with GluOx application. This decade of progress resulted from studies that included four Ph.D. (Ethiopia, Sweden, Austria), four M.Sc. (Ethiopia, Sweden) and Licentiate (Sweden) theses projects, plus one collaborative project in Sweden. The advances in grass pea research may be regarded as a model north-south cooperation for research and education.
|
|
| 10. |
- Tasić, Magdalena, et al.
(författare)
-
Electro-mechanically switchable hydrocarbons based on [8]annulenes
- 2022
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
-
Tidskriftsartikel (refereegranskat)abstract
- Pure hydrocarbons with shape and conjugation properties that can be switched by external stimuli is an intriguing prospect in the design of new responsive materials and single-molecule electronics. Here, we develop an oligomeric [8]annulene-based material that combines a remarkably efficient topological switching upon redox changes with structural simplicity, stability, and straightforward synthesis: 5,12-alkyne linked dibenzo[a,e]cyclooctatetraenes (dbCOTs). Upon reduction, the structures accommodate a reversible reorganization from a pseudo-conjugated tub-shape to a conjugated aromatic system. This switching in oligomeric structures gives rise to multiple defined states that are deconvoluted by electrochemical, NMR, and optical methods. The combination of stable electromechanical responsivity and ability to relay electrons stepwise through an extended (pseudo-conjugated) π-system in partially reduced structures validate alkyne linked dbCOTs as a practical platform for developing new responsive materials and switches based on [8]annulene cores.
|
|
