| 1. |
- Björck, Lars, et al.
(författare)
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Bacterial growth inhibited by a synthetic inhibitor based upon the structure of a human proteinase inhibitor
- 1989
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 337:6205, s. 385-386
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Tidskriftsartikel (refereegranskat)abstract
- Cysteine proteinases are important not only in the intracellular catabolism of peptides and proteins1 and in the processing of prohormones and proenzymes2,3, but also in the penetration of normal human tissue by malignant cells4 and possibly microorganisms5, including viruses. Cystatin C is a human cysteine proteinase inhibitor present in extracellular fluids6. We have synthesized peptide derivatives mimicking the proposed proteinase-binding centre of cystatin C7 and find that they irreversibly inhibit cysteine proteinases. Several bacteria produce proteinases, so we tested a tripeptide derivative (Z-LVG-CHN2) for in vitro anti-bacterial activity against a large number of bacterial strains belonging to thirteen different species. It was found to inhibit specifically the growth of all strains of group A streptococci. The susceptibility of these human pathogens to the peptide was compared with that to well-established anti-streptococcal antibiotics such as tetracy-cline and bacitracin. Moreover, the peptide was active in vivo against group A streptococci: mice injected with lethal doses of these bacteria were cured by a single injection of Z-LVG-CHN2. The cysteine proteinase produced by group A streptococci was isolated and found to be inhibited by Z-LVG-CHN2; moreover, excess proteinase relieved the growth inhibition caused by the peptide derivative, suggesting that the antibacterial activity of Z-LVG-CHN2 is due to inhibition of this cysteine proteinase. This strategy of blocking proteinases with peptide derivatives that mimic naturally occurring inhibitors could be useful in the construction of new agents against other microorganisms, including viruses.
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| 2. |
- Bovin, JO, et al.
(författare)
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Imaging of atomic clouds outside the surfaces of gold crystals by electron microscopy
- 1985
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 317, s. 47-49
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Tidskriftsartikel (refereegranskat)abstract
- The structure of small metal crystals has been intensively examined by high-resolution electron microscopy (HREM). In particular, multiply-twinned gold and silver crystals have been characterized using the profile-imaging method1,2 at atomic resolution, and reconstructed metal surfaces observed2. Crystal structure images of large gold clusters consisting of 55 gold atoms arranged in a cubeoctahedron have been recorded3 using 2.5 Å resolution, and crystal growth, row by row, on a {111} surface has been documented4 using a low-light-level silicon-intensified target television (TV) camera and video system with an on-line image processor. Direct imaging of rearrangements of atomic columns on extended gold surface5 established that profile imaging can provide information about surface self-diffusion. The motion of surface atoms, recorded with a real-time video tape-recorder (VTR) system, and the formation of surface atom steps on {100} surfaces, although not {111}, has also been reported recently6. Dynamic HREM observations at TV rate showing defect motion in gold7 and CdTe (refs. 8, 9) has given information on ‘in-lattice’ rearrangements of columns of atoms. We report here surface profile images recorded with the electron beam along the 〈110〉 direction with spatial resolution of ∼2.0 Å which reveal changes in occupancy of the atom columns often within periods of less than 0.1 s. Surfaces with several adjacent atom columns involved in rapid structural changes frequently interacted with a cloud of atoms extending out to 9 Å off the crystal and changes in shape and density of the clouds were recorded. Although these clouds have already been described6,10, the present work is the first to analyse these events properly and to describe them in detail. The motion of atomic columns and the existence of atom clouds revealed here may have important consequences for crystal growth, surface science and catalysis studies.
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| 3. |
- Hansen, Staffan, et al.
(författare)
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Oxidation Catalysis on YBa2Cu3O6 + x
- 1988
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 334:6178, s. 143-145
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Tidskriftsartikel (refereegranskat)abstract
- Mild oxidation catalysts are used to product a wide range industrial chemicals from hydrocarbons, whereas deep oxidation catalysts yield CO2 and are becoming important in the cleaning of emissions from combustion of carbonaceous fuels. Here we report on a catalyst1 that facilitates both mild and deep oxidation of toluene in the presence of molecular oxygen and ammonia. At low partial pressures of O2a YBa2Cu3O6+x catalyst is very active in the formation of benzonitrile, but at higher O2 partial pressures it preferentially catalyses formation of CO2. This sharp transition in product selectivity is reversible and occurs at a defined partial pressure of O2. At transition the bulk compostition of the catalyst is close to YBa2Cu3O6 (x≈0). Increasing the content of lattice oxygen (x > 0) makes the catalyst selective for CO2 formation
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| 4. |
- Löfstedt, Christer, et al.
(författare)
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Evolution of the ermine moth pheromone tetradecyl acetate
- 1986
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 323:6089, s. 621-623
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Tidskriftsartikel (refereegranskat)abstract
- The nine sympatric forms of small ermine moths of the genus Yponomeuta (Lepidoptere; Yponomeutidae) in the west palaearctic region show various degrees of differentiation1,2, including among other characteristics, differences in their sexual pheromones3. As is the case for many other moths4, the ermine moths so far analysed use delta 11-unsaturated acetates ((Z)-11-tetradecenyl, (E)-11-tetradecenyl and (Z)-11-hexadecenyl acetate) as primary pheromone components. Here for the first time in Lepidoptera we report that a saturated acetate, tetradecyl acetate, is the primary pheromone component5 of Y. rorellus (Hübner). Y. rorellus is almost monomorphic with respect to isoenzyme variation6 and has fewer chromosomes than its relatives7,8. We suggest that it has evolved through loss of unsaturated pheromone components in a 'genetic revolution' at a population bottleneck, and by the founders of the new species filling an empty communication niche, separated from that of the ancestral species.
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| 5. |
- von Schantz, Torbjörn, et al.
(författare)
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Female choice - Reply
- 1989
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 339:6224, s. 432-433
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Tidskriftsartikel (refereegranskat)
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| 6. |
- von Schantz, Torbjörn, et al.
(författare)
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Female choice selects for a viability-based male trait in pheasants
- 1989
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 337, s. 166-169
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Tidskriftsartikel (refereegranskat)abstract
- Recent theory on sexual selection1–4 suggests that females in species without paternal care choose mates by their secondary sexual characters because these indicate genotypic quality which will be transmitted to the offspring. These ideas are not yet empiri-cally supported as data quantifying the relationship between female mate choice and female reproductive success are lacking. Only in one case, in Colias butterflies, has it been demonstrated unequivo-cally that females choose 'good genotypes' as mates5 and there is only one study, on Drosophila, demonstrating that mate choice increases one component of offspring fitness6. Spur length of male pheasants (Phasianus colchicus) correlates with various fitness-related properties7. We here present the first experimental field data showing that female pheasants select mates on the basis of male spur length and that female mate choice correlates with female reproductive success.
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| 7. |
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