45,459 research outputs found
Mapping the Beta-Sheet Structure of the Yeast Prion Sup35 through Creation of Targeted Mutant Forms
Proteins with an aggregated form rich in beta-sheet structure are known as amyloids, of which a subset are infectious. These infectious proteins are known as prions and cause diseases including bovine spongiform encephalopathy (“Mad Cow” disease). Several prions have been identified in the baker’s yeast, Saccharomyces cerevisiae. One of the most well-studied yeast prions is the protein Sup35. To understand the fine protein structure of Sup35 better, we used PCR-based mutagenesis to introduce a lysine residue (a charged amino acid) at five defined places in the protein sequence of Sup35. We describe our process for creating these mutant versions and the results of DNA sequencing of each mutant version. The next step will be to assess prion formation and stability of clones with the correct sequences. Understanding the behavior of yeast prions has proven helpful in understanding human amyloid diseases and further studies on these yeast prions, including Sup35, will expand our knowledge further
Cohomology and Support Varieties for Lie Superalgebras II
In \cite{BKN} the authors initiated a study of the representation theory of
classical Lie superalgebras via a cohomological approach. Detecting subalgebras
were constructed and a theory of support varieties was developed. The dimension
of a detecting subalgebra coincides with the defect of the Lie superalgebra and
the dimension of the support variety for a simple supermodule was conjectured
to equal the atypicality of the supermodule. In this paper the authors compute
the support varieties for Kac supermodules for Type I Lie superalgebras and the
simple supermodules for . The latter result verifies our
earlier conjecture for . In our investigation we also
delineate several of the major differences between Type I versus Type II
classical Lie superalgebras. Finally, the connection between atypicality,
defect and superdimension is made more precise by using the theory of support
varieties and representations of Clifford superalgebras.Comment: 28 pages, the proof of Proposition 4.5.1 was corrected, several other
small errors were fixe
Global Hot Gas in and around the Galaxy
The hot interstellar medium traces the stellar feedback and its role in
regulating the eco-system of the Galaxy. I review recent progress in
understanding the medium, based largely on X-ray absorption line spectroscopy,
complemented by X-ray emission and far-UV OVI absorption measurements. These
observations enable us for the first time to characterize the global spatial,
thermal, chemical, and kinematic properties of the medium. The results are
generally consistent with what have been inferred from X-ray imaging of nearby
galaxies similar to the Galaxy. It is clear that diffuse soft X-ray
emitting/absorbing gas with a characteristic temperature of K
resides primarily in and around the Galactic disk and bulge. In the solar
neighborhood, for example, this gas has a characteristic vertical scale height
of kpc. This conclusion does not exclude the presence of a
larger-scale, probably much hotter, and lower density circum-Galactic hot
medium, which is required to explain observations of various high-velocity
clouds. This hot medium may be a natural product of the stellar feedback in the
context of the galaxy formation and evolution.Comment: 11 pages, invited talk in the workshop "The Local Bubble and Beyond
II
No confinement without Coulomb confinement
We compare the physical potential of an external quark-antiquark
pair in the representation of SU(N), to the color-Coulomb potential which is the instantaneous part of the 44-component of the gluon
propagator in Coulomb gauge, D_{44}(\vx,t) = V_{\rm coul}(|\vx|) \delta(t) +
(non-instantaneous). We show that if is confining, , then the inequality holds asymptotically at large , where is the Casimir in
the representation . This implies that is also
confining.Comment: 9 page
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