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| 2. |
- Bremberg, U, et al.
(författare)
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Rapid and stereoselective C-C, C-O, C-N and C-S couplings via microwave accelerated palladium-catalyzed allylic substitutions
- 2000
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Ingår i: Synthesis (Stuttgart). - Uppsala Univ, Uppsala Biomed Ctr, Dept Organ Pharmaceut Chem, SE-75123 Uppsala, Sweden. Royal Inst Technol, Dept Chem, SE-10044 Stockholm, Sweden.. - 0039-7881 .- 1437-210X. ; :7, s. 1004-1008
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Tidskriftsartikel (refereegranskat)abstract
- Palladium-catalyzed substitution of cyclohex-2-en-1-yl ethyl carbonate with neutral C-, O-, and N-nucleophiles was achieved in 1-2 minutes using microwave flash hearing. Enantioselectivities up to 96% were observed. Ionic nucleophiles tended to result in lower ee. With S-nucleophiles problems with the stability of the nucleophile were encountered.
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| 6. |
- Hallberg, Eric, et al.
(författare)
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Non-visual sense organs
- 2004
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Ingår i: Treatise on Zoology, Crustacea vol 1. - 978 90 04 12918 4 ; , s. 301-380
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Hallberg, Martin, et al.
(författare)
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Crystal structure of the 270 kDa homotetrameric lignin-degrading enzyme pyranose 2-oxidase
- 2004
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 341:3, s. 781-796
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Tidskriftsartikel (refereegranskat)abstract
- Pyranose 2-oxidase (P2Ox) is a 270 kDa homotetramer localized preferentially in the hyphal periplasmic space of lignocellulolytic fungi and has a proposed role in lignocellulose degradation to produce the essential co-substrate, hydrogen peroxide, for lignin peroxidases. P2Ox oxidizes D-glucose and other aldopyranoses regioselectively at C2 to the corresponding 2-keto sugars; however, for some substrates, the enzyme also displays specificity for oxidation at C3. The crystal structure of P2Ox from Trametes multicolor has been determined using single anomalous dispersion with mercury as anomalous scatterer. The model was refined at 1.8 Angstrom resolution to R and R-free values of 0.134 and 0.171, respectively. The overall fold of the P2Ox subunit resembles that of members of the glucose-methanol-choline family of long-chain oxidoreductases, featuring a flavin-binding Rossmann domain of class alpha/beta and a substrate-binding subdomain with a six-stranded central beta sheet and three U helices. The homotetramer buries a large internal cavity of roughly 15,000 Angstrom(3), from which the four active sites are accessible. Four solvent channels lead from the surface into the cavity through which substrate must enter before accessing the active site. The present structure shows an acetate molecule bound in the active site with the carboxylate group positioned immediately below the flavin N5 atom, and with one carboxylate oxygen atom interacting with the catalytic residues His548 and Asn593. The entrance to the active site is blocked by a loop (residues 452 to 461) with excellent electron density but elevated temperature factors. We predict that this loop is dynamic and opens to allow substrate entry and exit. In silico docking of D-glucose in the P2Ox active site shows that with the active-site loop in the closed conformation, monosaccharides cannot be accommodated; however, after removing the loop from the model, a tentative set of protein-substrate interactions for beta-D-glucose have been outlined.
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| 8. |
- Hellström, Ulrika, 2000, et al.
(författare)
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Carbohydrates act as receptors for the periodontitis-associated bacterium Porphyromonas gingivalis: a study of bacterial binding to glycolipids.
- 2004
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Ingår i: Glycobiology. - : Oxford University Press (OUP). - 0959-6658 .- 1460-2423. ; 14:6, s. 511-9
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Tidskriftsartikel (refereegranskat)abstract
- In this study we show for the first time the use of carbohydrate chains on glycolipids as receptors for the periodontitis-associated bacterium Porphyromonas gingivalis. Previous studies have shown that this bacterium has the ability to adhere to and invade the epithelial lining of the dental pocket. Which receptor(s) the adhesin of P. gingivalis exploit in the adhesion to epithelial cells has not been shown. Therefore, the binding preferences of this specific bacterium to structures of carbohydrate origin from more than 120 different acid and nonacid glycolipid fractions were studied. The bacteria were labeled externally with (35)S and used in a chromatogram binding assay. To enable detection of carbohydrate receptor structures for P. gingivalis, the bacterium was exposed to a large number of purified total glycolipid fractions from a variety of organs from different species and different histo-blood groups. P. gingivalis showed a preference for fractions of human and pig origin for adhesion. Both nonacid and acid glycolipids were used by the bacterium, and a preference for shorter sugar chains was noticed. Bacterial binding to human acid glycolipid fractions was mainly obtained in the region of the chromatograms where sulfated carbohydrate chains usually are found. However, the binding pattern to nonacid glycolipid fractions suggests a core chain of lactose bound to the ceramide part as a tentative receptor structure. The carbohydrate binding of the bacterium might act as a first step in the bacterial invasion process of the dental pocket epithelium, subsequently leading to damage to periodontal tissue and tooth loss.
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| 11. |
- Larsson, Mattias C, et al.
(författare)
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Specialized olfactory receptor neurons mediating intra- and interspecific chemical communication in leafminer moths Eriocrania spp. (Lepidoptera: Eriocraniidae).
- 2002
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Ingår i: Journal of Experimental Biology. - 1477-9145. ; 205:7, s. 989-998
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Tidskriftsartikel (refereegranskat)abstract
- We performed a physiological and morphological characterization of sensilla auricillica in male Eriocrania semipurpurella moths. Each auricillic sensillum contained three olfactory receptor neurons. Responding neurons (87 of 139) could be grouped into five physiological types. Type 1 responded to (R,Z)-6-nonen-2-ol and type 2 to its enantiomer (S,Z)-6-nonen-2-ol, both of which are pheromone components of E. semipurpurella. Type 3 responded to both (R)-heptan-2-ol and (R,Z)-4-hepten-2-ol, which are pheromone components of the sympatric species E. cicatricella. Types 4 and 5 responded to the ketones (Z)-6-nonen-2-one and/or nonan-2-one, which are found in the pheromone glands of female E. semipurpurella. Field-trapping showed that type 3 receptor neurons mediate strongly antagonistic effects of (R)-heptan-2-ol and (R,Z)-4-hepten-2-ol on E. semipurpurella, while nonan-2-one should possibly be included as a synergist in the sex pheromone blend of this species. The attraction of E. cicatricella and E. sparrmannella to compounds mixed with the pheromone blend of E. semipurpurella shows that the pheromone components of E. semipurpurella have little or no antagonistic effects on these species. The morphology and physiology of eriocraniid pheromone sensilla are very similar to those found in the order Trichoptera (caddisflies), suggesting a homology between pheromone detection systems in the two sister orders Lepidoptera and Trichoptera.
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| 13. |
- Le Rouzic, E, et al.
(författare)
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Docking of HIV-1 Vpr to the nuclear envelope is mediated by the interaction with the nucleoporin hCG1
- 2002
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 277:47, s. 45091-45098
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Tidskriftsartikel (refereegranskat)abstract
- The HIV-1 genome contains several genes coding for auxiliary proteins, including the small Vpr protein. Vpr affects the integrity of the nuclear envelope and participates in the nuclear translocation of the preintegration complex containing the viral DNA. Here, we show by photobleaching experiments performed on living cells expressing a Vpr-green fluorescent protein fusion that the protein shuttles between the nucleus and the cytoplasm, but a significant fraction is concentrated at the nuclear envelope, supporting the hypothesis that Vpr interacts with components of the nuclear pore complex. An interaction between HIV-1 Vpr and the human nucleoporin CG1 (hCG1) was revealed in the yeast two-hybrid system, and then confirmed both in vitro and in transfected cells. This interaction does not involve the FG repeat domain of hCG1 but rather the N-terminal region of the protein. Using a nuclear import assay based on digitonin-permeabilized cells, we demonstrate that hCG1 participates in the docking of Vpr at the nuclear envelope. This association of Vpr with a component of the nuclear pore complex may contribute to the disruption of the nuclear envelope and to the nuclear import of the viral DNA.
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