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| 2. |
- Larsson, Ted
(författare)
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Direct electron transfer between cellobiose dehydrogenase and solidmetal or graphite electrodes
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Direct electron transfer (ET) between the enzyme cellobiose dehydrogenase (CDH) and different metal and graphite electrodes has been investigated. The heme domain of the CDH has been shown to play a key-role in the direct ET. A mechanism for the ET between CDH and graphite electrodes was proposed. Based on this mechanism, a kinetic model was developed. The catalytic current was studied under different experimental conditions. Thus the pH, substrate concentration and electrode potential were varied. A satisfactory correlation between the experimental data and the kinetic model was obtained.The catalytic current for the CDH-modified electrodes was dependent on the ionic strength. An increase in the NaCl concentration increased the catalytic current. This effect was assigned to the screening of negative charges close to the heme iron in CDH.A new cell for spectroelectrochemistry was developed and investigated. The cell volume was only 1 µl allowing small samples to be studied. The pH dependence of the formal potential E0’, of the heme was investigated for dissolved CDH and compared to E0’ determined by cyclic voltammetry for CDH on thiol modified gold. The result showed that there was a difference in formal potential on the order of 50 mV between dissolved and surface adsorbed CDH. However, the slope of the pH dependence was the same in both cases.A biosensor, based on a dual-electrode cell was developed. The two electrodes were based on CDH and the enzyme oligosaccharide dehydrogenase (ODH) ‘wired’ with an osmium-based redox polymer on solid graphite. The electrode system was used as an end column detector for the detection of various sugars after their separation in a size exclusion chromatographic (SEC) system.
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| 3. |
- Larsson, Ted, et al.
(författare)
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Electron transfer between cellobiose dehydrogenase and graphite electrodes
- 1996
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 331:3, s. 207-215
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Tidskriftsartikel (refereegranskat)abstract
- Electron transfer between the enzyme cellobiose dehydrogenase (CDH) and a flavin adenine dinucleotide (FAD) containing a catalytic active fragment of CDH (FAD-fragment) and a graphite electrode, respectively, was established. The current response in the presence of the enzyme substrate for graphite electrodes with CDH or the FAD-fragment adsorbed on the freshly polished graphite surface were compared with that of electrodes where CDH or the FAD-fragment were crosslinked in a redox polymer at the electrode surface. The initial slope, dj/d[S](S=0), where j is the current density and [S](S=0) the zero substrate concentration, was taken as a measure of the substrate response. For the electrodes with enzymes adsorbed directly on the surface, dj/d[S](S=0), was a factor of 3 lower than for electrodes prepared with the polymer mixture. The redox polymer based electrodes, with CDH and with FAD-fragment, both showed a high and close to equal substrate response. In contrast the surface adsorbed CDH gave a much higher substrate response than the FAD-fragment.
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| 4. |
- Leinsköld, Ted, et al.
(författare)
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Effect of postoperative insulin-like growth factor I supplementation on protein metabolism in humans
- 1995
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Ingår i: British Journal of Surgery. - : Oxford University Press (OUP). - 0007-1323 .- 1365-2168. ; 82:7, s. 921-925
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Tidskriftsartikel (refereegranskat)abstract
- Insulin-like growth factor I (IGF-I) has been shown experimentally to exert a nitrogen-sparing effect in both animals and humans. Its effects on protein metabolism during the first 5 days after radical large bowel resection were investigated. Nineteen patients were randomly allocated to receive either human recombinant IGF-I (2 × 80 μ/kg body weight subcutaneously, n = 10) or placebo (n = 9) starting on the morning of the first day after operation. All patients received parenteral nutrition (glucose 3 g and nitrogen 0.1 g/kg/day). The mean(s.e.m.) urinary nitrogen: creatinine ratio was significantly reduced in patients who received IGF-I compared with those given placebo (275.0(17.1) compared with 386.3(23.6), P<0.01). The mean urinary 3-methylhistidine: creatinine ratio and nitrogen balance were lower in the IGF-I group, but not significantly so. Plasma IGF-I concentrations were four times higher in the treated group compared with those in the placebo group. Insulin-like growth factor binding protein 3 (IGFBP-3) increased significantly after the start of IGF-I treatment, compared with mean postoperative levels. The mean blood glucose concentration was significantly lower in the IGF-I group than the placebo group (P < 0.05) but no patient had a hypoglycaemic attack. The authors conclude that IGF-I does not significantly influence the nitrogen balance, but that results indicate a possible nitrogen-sparing effect in patients after major abdominal operations. IGF-I therapy is safe, and may be of value in catabolic patients after serious injury and major operations.
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