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- Gustafson, Inga, 1954-
(författare)
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Phospholipid membranes in biosensor applications : Stability, activity and kinetics of reconstituted proteins and glycolipids in supported membranes
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this study the formation of supported membranes onto planar solid supports has been investigated. The stability and activity of reconstituted membrane receptors has been studied. The potential use of such preparations in biosensor applications is discussed.The lipid films were made by the Langmuir Blodgett and by the liposome fusion techniques. These supported films were characterised by ellipsometry, atomic force microscopy, surface plasmon resonance (SPR) and resonant mirror techniques. The thickness of the films was in agreement with that of a cell membrane. The kinetics of formation of the lipid films was studied and discussed.The proteins, bacteriorhodopsin, cytochrome oxidase, acetylcholinesterase and the nicotinic acetylcholine receptor were reconstituted into the supported membrane. The subsequent analysis showed that the proteins were individually distributed and that the activity was retained, in some cases for several weeks after immobilisation.The glycolipids, GM1, GM2, GD1b, asialo-GM1, globotriaosylceramide, lactosylceramide and galactosylceramide, were also reconstituted into the supported membranes. Their specific interaction with the toxin ricin or with its B-chain was examined using SPR. The affinity of intact toxin and of its B-chain differed markedly and was pH dependent. The carbohydrate chain length and charge density of the glycolipids also influenced the affinity.
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| 2. |
- Koskinen, Lars-Owe D., Professor, 1955-, et al.
(författare)
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The neuropeptide TRH has a minor effect on the enzymatic activity of acetylcholinesterase in vitro.
- 1998
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Ingår i: Peptides. - : Elsevier BV. - 0196-9781 .- 1873-5169. ; 19:10, s. 1675-1677
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Tidskriftsartikel (refereegranskat)abstract
- The neuropeptide thyrotropin-releasing hormone (TRH) elicits a variety of physiological effects of which some are due to cholinergic mechanisms. TRH modulates in vivo the effects of compounds affecting acetylcholinesterase (AChE). In the present study the in vitro effects of TRH on the activity of AChE were explored. TRH has no effect at physiologically relevant concentrations. At unphysiologically high concentrations (>5 mM) a slight inhibition was found. This was noticed also when the enzyme was exposed to the amide-free tripeptide analog p-Glu-His-Pro. We conclude that any cholinergic effect of TRH observed in vivo is unlikely to be due to a direct interaction of the peptide with AChE.
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| 4. |
- Puu, Gertrud, 1945-
(författare)
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Oscillatory phenomena in chloroplasts from spinach cotyledons
- 1976
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A suspensionofchloroplasts, isolated from spinach cotyledons, was found to be an oscillatory system, i.e. a system in which one parameter (or more) varies over time in a fairly regular way.The oscillations, with a period of fifteen to twenty minutes,occured spontaneously in the light as well as in the dark and were self-sustained for several hours.Catalase activity was the parameter on which the oscillations in the chi oroplastic system were first observed and was also the parameter most intensely studied. Some other parameters investigated were the amount of glutathione, oxidation-reduction potential and activities of glucose-6-phosphate dehydrogenase and NADP-1inked malate dehydrogenase.Oscillations could be induced in previously non-oscillating systems (e.g. in dialysed chloroplast extracts) by addition of ascorbate and glutathione. A mechanism is suggested, built upon a respiratory chain in which the ascorbate and glutathione redox couples are involved and which is known to occur in young plants. The mechanism involves cyclic changes in the redox state of sulphur groups (-SH^^-SS- transitions) in some enzymes, causing changes in the activities of the enzyme. The proposed feed-back mechanism thus implies covalent modification of enzymes. The enzymes involved were found to be localized mainly in the stroma space of the chloroplast.
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