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| 2. |
- Hedbys, Lars, et al.
(författare)
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Synthesis of Galβ1-3GlcNAc and Galβ1-3GlcNAcβ-SEt by an enzymatic method comprising the sequential use of β-galactosidases from bovine testes and Escherichia coli
- 1989
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Ingår i: Glycoconjugate Journal. - 1573-4986. ; 6, s. 161-168
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Tidskriftsartikel (refereegranskat)abstract
- Galβ1-3GlcNAc (1) and Galβ1-3GlcNAcβ-SEt (2) were synthesized on a 100 mg scale by the transgalactosylation reaction of bovine testes β-galactosidase with lactose as donor andN-acetylglucosamine and GlcNAcβ-SEt as acceptors. In both cases the product mixtures contained unwanted isomers and were treated with β-galactosidase from Escherichia coli which has a different specificity, under conditions favouring hydrolysis, yielding besides the desired products, monosaccharides and traces of trisaccharides. The products were purified to >95% by gel filtration, with a final yield of 12% of 1 and 17% of 2, based on added acceptor. In a separate experiment Galβ1-6GlcNAcβ-SEt (3) was synthesized by the transglycosylation reaction using β-galactosidase from Escherichia coli. No other isomers were detected. Compound 3 was purified by HPLC.
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| 3. |
- Johansson, Elisabet, et al.
(författare)
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Studies of the reversed α-mannosidase reaction in high concentrations of mannose
- 1989
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Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 11:6, s. 347-352
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Tidskriftsartikel (refereegranskat)abstract
- The reversal of the hydrolytic activity of α-mannosidase from jack bean has been studied in high concentrations of mannose. From an initial concentration of 85% mannose (w/w), a maximum yield of 70% (w/w) di- and oligosaccharides was obtained. The products were separated by gel chromatography and high-performance liquid chromatography, and characterized by gas-liquid chromatographymass spectrometry and 1H-nuclear magnetic resonance spectroscopy. The equilibrium for the formation of di- and oligosaccharides was investigated, and the equilibrium constant for the formation of disaccharides was calculated to be 5.5 ± 0.9. The stability of the enzyme and the rate of formation of disaccharides were studied as functions of temperature, pH, and starting concentration of mannose. It was shown that the enzyme was not inhibited by a total sugar concentration of 83% (w/w), compared with 40%.
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| 4. |
- Johansson, Elisabet, et al.
(författare)
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Synthesis of mannose oligosaccharides via reversal of the α-mannosidase reaction
- 1986
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Ingår i: Biotechnology Letters. - 0951-208X. ; 8, s. 421-424
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Tidskriftsartikel (refereegranskat)abstract
- Three naturally occurring isomers of the disaccharideO-α-D-mannosyl-D-mannoside were synthesized by reversing the hydrolytic activity of jack bean α-mannosidase at 75°C in a very high concentration of mannose. Higher oligosaccharides were also obtained at the later stages of the reaction. The maximum total yield of disaccharides was 37% (w/w) based on the total amount of saccharides.
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| 5. |
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| 6. |
- Svensson, Nils-Olof
(författare)
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Late Weichselian and early Holocene shore displacement in the central Baltic, based on stratigraphical and morphological records from eastern Småland and Gotland, Sweden
- 1989
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The glacial unloading and resulting isostatic land uplift have together with hydro-isostasy, eustatic rise of sea-level and geoidal changes, ruled the shore displacement of Fennoscandia. Within the Baltic basin, periods of damming and shifts of outlet further complicated the shore displacement during the period studied, c. 12,200-8400 BP. Information on the Baltic history was derived from shoreline observations and studies on sediment cores from lakes formerly directly affected by the Baltic. These cores were analysed with respect to pollen, diatoms, and lithology to determine sequences of Baltic sediments, and dated by a combination of radiocarbon dates and biostratigraphy. The studied areas of southeastern Sweden, mainly central Gotland and the Oskarshamn area, eastern Småland, display a similar course of shore displacement. The Late Weichselian period shows a regression of a slightly decreasing rate between c. 12,200 and 10,300 BP. Then followed a fast drop (25 m) of the Baltic's water level; the final drainage of the Baltic Ice Lake. During the next c. 700 yr, the Yoldia stage, a regression of c. 17 m occurred. This period is mainly characterized by fresh-water diatoms in the Baltic, but at c. 10,000 BP there is evidence of a shortlasting (100-150 yr) period with brackish water. The Ancylus transgression, of c. 11 m, began c. 9600 BP and culminated c. 9300 BP. It was followed by a fast regression of 5-10 m, thereafter the rate of regression decreased. Shoreline gradients shows that the fastest shoreline tilting occurred around 10,000 BP, thus c. 2000 years after deglaciation.
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