4 research outputs found
Abundance analysis of targets for the COROT / MONS asteroseimology missions I. Semi-automatic abundance analysis of the gamma Dor star HD 49434
One of the goals of the ground-based support program for the COROT and
MONS/Roemer satellite missions is to select and characterise suitable target
stars for the part of the missions dedicated to asteroseismology. While the
global atmospheric parameters may be determined with good accuracy from the
Stromgren indices, careful abundance analysis must be made for the proposed
main targets. This is a time consuming process considering the long list of
primary and secondary targets. We have therefore developed new software called
VWA for this task. The VWA automatically selects the least blended lines from
the atomic line database VALD, and consequently adjusts the abundance in order
to find the best match between the calculated and observed spectra. The
variability of HD 49434 was discovered as part of COROT ground-based support
observations. Here we present a detailed abundance analysis of HD 49434 using
VWA. For most elements we find abundances somewhat below the Solar values, in
particular we find [Fe/H] = -0.13(14). We also present the results from the
study of the variability that is seen in spectroscopic and photometric time
series observations. From the characteristics of the variation seen in
photometry and in the line profiles we propose that HD 49434 is a variable star
of the gamma Doradus type.Comment: 10 pages, 6 figure
Regenerative biosensor chips based on switchable mutants of avidin—A systematic study
Biotinylated bait molecules can be immobilized on biotinylated sensor chips by formation of biotin–avidin–biotin bridges which are very stable when using wild-type (strept)avidin. Stable immobilization of biotinylated baits is important for monitoring reversible binding and dissociation of prey molecules. For measurements with another bait molecule, however, it is desirable to replace all immobilized proteins by fresh (strept)avidin and new biotinylated bait. In this study, five avidin mutants have been characterized with respect to their ability to form switchable biotin–avidin–biotin bridges on biotinylated chip surfaces, as needed for complete chip regeneration. All five mutants formed stable biotin–avidin–biotin bridges at pH 7, were more or less stable at pH 2–3, and required the combination of pH 2 with SDS for quantitative removal from the chip surface. Mutant #3 (“switchavidin”) showed the best combination of properties, i.e., low nonspecific adsorption of protein and nucleic acids, high binding capacity, and good stability at pH 2–3, as typically used for quantitative removal of prey molecules in repeated measurement cycles