Biological and biochemical characterisation of rubella virus strains

In this thesis the biological and biochemical properties of 6 strains of rubella virus (vaccine strains RA27/3 and HPV77, laboratory strain Judith, and three wild type isolates) were compared. The growth characteristics of all virus strains were similar although they could be distinguished by neutralisation kinetics, foci morphology in RK13 cells and rate limiting ELISA. In neutralization kinetics the homologous reaction is, in general, faster than the heterologous reaction. The morphology of the foci of infection varies from strain to strain, some strains produce many small foci (0.1mm in diameter), resulting in extensive CPE whilst others produce large discrete foci (>0.5mm in diameter) with localised CPE (identified by histochemical staining). Rate limiting ELISA shows that the reaction of post vaccination sera with different rubella strains is more varied than that of acute sera or sera from a remote natural infection. These results suggest a degree of antigenic diversity in rubella virus strains. All virus strains show similar structural proteins by western blotting. However different antigenic peptides were identified by limited protease digestion of the virus followed by western blotting. This result suggests a difference in amino acid sequence between strains. The biological and chemical properties of the immunodominant rubella El protein (cloned from laboratory strain Judith and expressed in E. coli) were also studied. Its antigenicity was assessed using sera from individuals with natural or vaccine induced rubella immunity. The results obtained showed that the reaction of specific sera to the recombinant antigen distinguished between strains of virus and RA27/3. The reaction of RA27/3 was significantly slower at 20% of the reaction rate of other strains of virus. Overall the results presented in this thesis demonstrate a difference in antigenic specificity between strains of virus, particularly between RA27/3 and other strains, possibly explaining the high rate of reinfection after vaccination compared with naturally immune individuals

Direct evidence that maltose transport activity Is affected by the lipid composition of brewer’s yeast

A brewer’s yeast strain was grown with maltose as sole carbon source under strictly anaerobic conditions with and without ergosterol and /or unsaturated fatty acid (Tween 80) supplements. Under all these conditions the MALx1 genes for maltose transporters were strongly expressed during growth. The fatty acid unsaturation indices of growing and stationary phase yeast were increased from about 20% to 56–69% by supplementation with Tween 80. Ergosterol contents were increased up to at least 4- fold by supplementation with ergosterol and Tween 80. Maltose transport activity measured at 20°C was not increased by supplementation with Tween 80 alone, but was increased 2-fold and 3-fold, respectively, in growing and stationary phase yeast by supplementation with ergosterol together with Tween 80. The stimulation of maltose transport by ergosterol was greater when the transport was measured at temperatures (10°C and 0°C) lower than 20°C. The results show that proper function of maltose transporters requires adequate amounts of ergosterol in the yeast. This effect may partly explain the low maltose (and maltotriose) uptake rates both in the second half of brewery fermentations, when the sterol content of yeast has fallen, and when fresh wort is pitched with sterol-deficient cropped yeast.Finnish brewing and malting industry (PBL) ; Leonardo da Vinci programme ; Fundação para a Ciência e a Tecnologia (FCT

A borane laser

© 2015 Macmillan Publishers Limited. Emission from electronically excited species forms the basis for an important class of light sources-lasers. So far, commercially available solution-processed blue-emitting laser materials are based on organic compounds or semiconductor nanocrystals that have significant limitations: either low solubility, low chemical-and/or photo-stability and/or uncompetitive prices. Here we report a novel and competitive alternative to these existing laser materials that is based on boron hydrides, inorganic cluster compounds with a rich and diverse chemistry. We demonstrate that solutions of the borane anti-B 18 H 22 show, under pulsed excitation, blue laser emission at 406 nm with an efficiency (ratio of output/input energies) of 9.5%, and a photostability superior to many of the commercially available state-of-the-art blue laser dyes. This demonstration opens the doors for the development of a whole new class of laser materials based on a previously untapped resource for laser technology-the boranes.Peer Reviewe