1,945 research outputs found
Flow dependence of high parton energy loss in heavy-ion collisions
The measured transverse momentum spectra and HBT correlations of bulk (i.e.
low ) matter can be well explained by assuming that the soft sector of
particles produced in ultrarelativistic heavy-ion collisions is (approximately)
thermalized and undergoes collective accelerated expansion in both longitudinal
and transverse direction. However, this implies that bulk matter will have a
non-vanishing flow component transverse to the trajectory of a high
partonic jets. In general, this will increase the energy loss experienced by
the jet parton and modify the shape of the jet cone. In this paper, we present
a systematic study of the magnitude of the additional energy loss induced by
flow under realistic assumptions for the medium evolution. We argue that a
perturbative QGP description may be sufficient for the measured if
flow during the medium evolution is taken into account properly
Interferon y Stimulation Modulates the Proteolytic Activity and Cleavage Site Preference of 20S Mouse Proteasomes
The proteasome is a 700-kD multisubunit enzyme complex with several proteolytically active
sites. The enzyme complex is involved in both ubiquitin-dependent and -independent protein
degradation and may contribute to the processing of antigens presented by major histocompatibility
complex (MHC) class I molecules. Here we demonstrate that treatment of mouse fibroblast cells
with 20 U interferon qr (IFN-y) for 3 d induces a change in the proteasome subunit composition
and that the B-type subunit LMP2, which is encoded in the MHC class II region, is incorporated
into the enzyme complex. This is paralleled by reduction of the homologous 6-subunit. IFN-3'
stimulation results in a downregulation of the chymotrypsin-like Suc-LLVY-MCA peptide
hydrolyzing activity of 20S proteasomes whereas the trypsin-like activity remains unaffected.
When tested as a substrate a synthetic 25-mer polypeptide whose sequence covers the antigenic
nonapeptide YPHFMPTNL of the MCMV pp89, 20S proteasomes of IFN-3'-induced cells exhibit
altered chymotrypsin-like cleavage site preferences. In the absence of IFN-qr induction, the naturally
processed nonamer peptide that is presented by MHC class.I molecules appears as a minor cleavage
product. IFN-'y activation does not result in an increase of the final peptide but results in a
different set of peptides. We hypothesize that these peptides represent precursor peptides that
can be trimmed to final peptide size
Academic Supports Preferred by Academically Struggling African American Students at a Predominantly White University
Academic supports offered by Predominately White Institutions (PWIs) meet the needs of individuals who achieve standards such as high grade point averages and high standardized test scores, and who can negotiate traditional college institutions. Evidence indicates that retention and graduation rates for underrepresented minority students may be lower in comparison to White peers at the same institutions. Observations indicated that academic supports offered by a Midwestern PWI, may not provide the services preferred by African American students who struggle academically in two colleges, the College of Education and the College of Nursing.
A mixed-methods design was used to determine what academic supports were known and being used by academically struggling African American students at a PWI. Survey questions and interviews focused on gaining understandings of student preferences for academic supports in a population of academically struggling African American students.
These results may be used to design academic supports for struggling African American students and may be generalized to PWIs of similar demographics and socio-cultural settings. Application of the results to academic support design may improve retention and graduation rates for this student group. Students requested increased interaction with faculty, late night or 24-hour tutoring services, assistance with time management, more social media to assist with reminders about assignments and class projects, and assistance with technology and online classes. Some differences were noted between what was recorded in the literature and the results of this study in the areas of study groups, same ethnicity faculty, group membership and mentoring
Cytomegalovirus prevents antigen presentation by blocking the transport of peptide-loaded major histocompatibility complex class I molecules into the medial-Golgi compartment
Selective expression of murine cytomegalovirus (MCMV) immediate-early (IE) genes leads to
the presentation by the major histocompatibility complex (MHC) class I molecule L a of a
peptide derived from MCMV IE protein pp89 (Reddehase, M. J., J. B. Rothbard, and U. H.
Koszinowski. 1989. Nature (Lond.). 337:651). Characterization of endogenous antigenic peptides
identified the pp89 peptide as the nonapeptide msYPHFMFFNLt76 (del Val, M., H.-J. Schlicht,
T. Ruppert, M. J. Reddehase, and U. H. Koszinowski. 1991. Cell. 66:1145). Subsequent expression
of MCMV early genes prevents presentation of pp89 (del Val, M., K. Mfinch, M. J. Reddehase,
and U. H. Koszinowski. 1989. Cell. 58:305). We report on the mechanism by which MCMV
early genes interfere with antigen presentation. Expression of the IE promoter-driven bacterial
gene lacZ by recombinant MCMV subjected antigen presentation of B-galactosidase to the same
control and excluded antigen specificity. The La-dependent presence of naturally processed
antigenic peptides also in nonpresenting cells located the inhibitory function subsequent to the
step of antigen processing. The finding that during the E phase of MCMV gene expression the
MHC class I heavy chain glycosylation remained in an Endo H-sensitive form suggested a block
within the endoplasmic reticulum/c/s-Golgi compartment. The failure to present antigenic peptides
was explained by a general retention of nascent assembled trimolecular MHC class I complexes.
Accordingly, at later stages of infection a significant decrease of surface MHC class I expression
was seen, whereas other membrane glycoproteins remained unaffected. Thus, MCMV E genes
endow this virus with an effective immune evasion potential. These results also indicate that
the formation of the trimolecular complex of MHC dass I heavy chain, ~2-microglobulin, and
the finally trimmed peptide is completed before entering the medial-Golgi compartment
Linkage Evidence for a Two-Locus Inheritance of LQT-Associated Seizures in a Multigenerational LQT Family With a Novel KCNQ1 Loss-of-Function Mutation
Mutations in several genes encoding ion channels can cause the long-QT (LQT)
syndrome with cardiac arrhythmias, syncope and sudden death. Recently, mutations in
some of these genes were also identified to cause epileptic seizures in these patients, and
the sudden unexplained death in epilepsy (SUDEP) was considered to be the pathologic
overlap between the two clinical conditions. For LQT-associated KCNQ1 mutations, only
few investigations reported the coincidence of cardiac dysfunction and epileptic seizures.
Clinical, electrophysiological and genetic characterization of a large pedigree (n = 241
family members) with LQT syndrome caused by a 12-base-pair duplication in exon 8 of
the KCNQ1 gene duplicating four amino acids in the carboxyterminal KCNQ1 domain
(KCNQ1dup12; p.R360_Q361dupQKQR, NM_000218.2, hg19). Electrophysiological
recordings revealed no substantial KCNQ1-like currents. The mutation did not exhibit a
dominant negative effect on wild-type KCNQ1 channel function. Most likely, the mutant
protein was not functionally expressed and thus not incorporated into a heteromeric
channel tetramer. Many LQT family members suffered from syncopes or developed
sudden death, often after physical activity. Of 26 family members with LQT, seizures were
present in 14 (LQTplus seizure trait). Molecular genetic analyses confirmed a causative
role of the novel KCNQ1dup12 mutation for the LQT trait and revealed a strong link
also with the LQTplus seizure trait. Genome-wide parametric multipoint linkage analyses
identified a second strong genetic modifier locus for the LQTplus seizure trait in the
chromosomal region 10p14. The linkage results suggest a two-locus inheritance model
for the LQTplus seizure trait in which both the KCNQ1dup12 mutation and the 10p14
risk haplotype are necessary for the occurrence of LQT-associated seizures. The data
strongly support emerging concepts that KCNQ1 mutations may increase the risk of
epilepsy, but additional genetic modifiers are necessary for the clinical manifestation of
epileptic seizures
Protein O-Mannosylation in the Murine Brain: Occurrence of Mono-O-Mannosyl Glycans and Identification of New Substrates
Protein O-mannosylation is a post-translational modification essential for correct development of mammals. In humans, deficient O-mannosylation results in severe congenital muscular dystrophies often associated with impaired brain and eye development. Although various O-mannosylated proteins have been identified in the recent years, the distribution of O-mannosyl glycans in the mammalian brain and target proteins are still not well defined. In the present study, rabbit monoclonal antibodies directed against the O-mannosylated peptide YAT(α1-Man)AV were generated. Detailed characterization of clone RKU-1-3-5 revealed that this monoclonal antibody recognizes O-linked mannose also in different peptide and protein contexts. Using this tool, we observed that mono-O-mannosyl glycans occur ubiquitously throughout the murine brain but are especially enriched at inhibitory GABAergic neurons and at the perineural nets. Using a mass spectrometry-based approach, we further identified glycoproteins from the murine brain that bear single O-mannose residues. Among the candidates identified are members of the cadherin and plexin superfamilies and the perineural net protein neurocan. In addition, we identified neurexin 3, a cell adhesion protein involved in synaptic plasticity, and inter-alpha-trypsin inhibitor 5, a protease inhibitor important in stabilizing the extracellular matrix, as new O-mannosylated glycoproteins
What does the rho-meson do? In-medium mass shift scenarios versus hadronic model calculations
The NA60 experiment has studied low-mass muon pair production in In-In
collisions at with unprecedented precision. With these results
there is hope that the in-medium modifications of the vector meson spectral
function can be constrained more thoroughly than before. We investigate in
particular what can be learned about collisional broadening by a hot and dense
medium and what constrains the experimental results put on in-medium mass shift
scenarios. The data show a clear indication of considerable in-medium
broadening effects but disfavor mass shift scenarios where the -meson
mass scales with the square root of the chiral condensate. Scaling scenarios
which predict at finite density a dropping of the -meson mass that is
stronger than that of the quark condensate are clearly ruled out since they are
also accompanied by a sharpening of the spectral function.Comment: Proceeding contribution, Talk given by J. Ruppert at Workshop for
Young Scientists on the Physics of Ultrarelativistic Nucleus-Nucleus
Collisions (Hot Quarks 2006), Villasimius, Sardinia, Italy, 15-20 May 2006.
To appear in EPJ
- …