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- Abrahamsson, Jonas, 1954, et al.
(författare)
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Cholesteryl sulphate and phosphate in the solid state and in aqueous systems.
- 1977
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Ingår i: Chemistry and physics of lipids. - 0009-3084. ; 19:3, s. 213-22
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Tidskriftsartikel (refereegranskat)abstract
- Cholesteryl sodium sulphate (CS) crystallizes as the dihydrate, the crystal structure of which is known. On heating the dihydrate, solid state phase transitions are observed at 65 degrees C and 95 degrees C and melting occurs at 165 degrees C. The structure of the high temperature phase has not been determined. Cholesteryl dihydrogen phosphate (CP) is not isostructural with any phases of CS. It undergoes a phase transition at 50 degrees C and melts at 190 degrees C. In systems with water CS is unstable whereas it was possible to determine the phase diagram of CP. In most of the composition range a crystalline hydrate is in equilibrium with a gel-phase. The latter has remarkable properties in that lamellar order exists with the 46 A lipid bilayer interleaved with water layers up to 1000 A. The monofilm behaviour of CS and CP at different pH levels is also reported.
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- Hagström, Åke, et al.
(författare)
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Frequency of dividing cells a new approach to the determination of bacterial growth rates in aquatic environments
- 1979
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Ingår i: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 37:5, s. 805-812
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Tidskriftsartikel (refereegranskat)abstract
- Frequency of dividing cells is suggested to be an indirect measureof the mean growth rate of an aquatic bacterial community. Seasonalchanges in frequency of dividing cells were found which covariatedwith the bacterial uptake of 14C-labeled phytoplankton exudates.Batch and continuous culture growth experiments, using brackishwater bacteria in pure and mixed enrichment cultures, were performedto establish a relationship between frequency of dividing cellsand growth rate. An improved technique for bacterial directcounts, using fluorescent staining and epifluorescence microscopy,is presented. Based on a 6-month survey in a coastal area ofthe Baltic Sea, the bacterial production in the photic zoneis estimated. Compared to the total primary production in thearea, the bacterial population during this period utilized approximately25% of the amount of carbon originally fixed by the primaryproducers.
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