1,802 research outputs found
Benzene formation in the inner regions of protostellar disks
Benzene (c-C6H6) formation in the inner 3 AU of a protostellar disk can be
efficient, resulting in high abundances of benzene in the midplane region. The
formation mechanism is different to that found in interstellar clouds and in
protoplanetary nebulae, and proceeds mainly through the reaction between allene
(C3H4) and its ion. This has implications for PAH formation, in that some
fraction of PAHs seen in the solar system could be native rather than inherited
from the interstellar medium.Comment: 9 pages, 2 colour figures, to be published in the Astrophysical
Journal Letter
NMR structure of the three quasi RNA recognition motifs (qRRMs) of human hnRNP F and interaction studies with Bcl-x G-tract RNA: a novel mode of RNA recognition
The heterogeneous nuclear ribonucleoprotein (hnRNP) F belongs to the hnRNP H family involved in the regulation of alternative splicing and polyadenylation and specifically recognizes poly(G) sequences (G-tracts). In particular, hnRNP F binds a G-tract of the Bcl-x RNA and regulates its alternative splicing, leading to two isoforms, Bcl-xS and Bcl-xL, with antagonist functions. In order to gain insight into G-tract recognition by hnRNP H members, we initiated an NMR study of human hnRNP F. We present the solution structure of the three quasi RNA recognition motifs (qRRMs) of hnRNP F and identify the residues that are important for the interaction with the Bcl-x RNA by NMR chemical shift perturbation and mutagenesis experiments. The three qRRMs exhibit the canonical βαββαβ RRM fold but additional secondary structure elements are present in the two N-terminal qRRMs of hnRNP F. We show that qRRM1 and qRRM2 but not qRRM3 are responsible for G-tract recognition and that the residues of qRRM1 and qRRM2 involved in G-tract interaction are not on the β-sheet surface as observed for the classical RRM but are part of a short β-hairpin and two adjacent loops. These regions define a novel interaction surface for RNA recognition by RRM
NMR structure of the three quasi RNA recognition motifs (qRRMs) of human hnRNP F and interaction studies with Bcl-x G-tract RNA: a novel mode of RNA recognition
The heterogeneous nuclear ribonucleoprotein (hnRNP) F belongs to the hnRNP H family involved in the regulation of alternative splicing and polyadenylation and specifically recognizes poly(G) sequences (G-tracts). In particular, hnRNP F binds a G-tract of the Bcl-x RNA and regulates its alternative splicing, leading to two isoforms, Bcl-x(S) and Bcl-x(L), with antagonist functions. In order to gain insight into G-tract recognition by hnRNP H members, we initiated an NMR study of human hnRNP F. We present the solution structure of the three quasi RNA recognition motifs (qRRMs) of hnRNP F and identify the residues that are important for the interaction with the Bcl-x RNA by NMR chemical shift perturbation and mutagenesis experiments. The three qRRMs exhibit the canonical βαββαβ RRM fold but additional secondary structure elements are present in the two N-terminal qRRMs of hnRNP F. We show that qRRM1 and qRRM2 but not qRRM3 are responsible for G-tract recognition and that the residues of qRRM1 and qRRM2 involved in G-tract interaction are not on the β-sheet surface as observed for the classical RRM but are part of a short β-hairpin and two adjacent loops. These regions define a novel interaction surface for RNA recognition by RRMs
Acute confusion and ataxia in the emergency department with an unexpected underlying diagnosis
No Abstrac
Emotion regulation after traumatic brain injury: distinct patterns of sympathetic activity during anger expression and recognition
Abstract
OBJECTIVE:
To assess psychological and psychophysiological correlates of emotion recognition and anger experience in participants with traumatic brain injury (TBI).
PARTICIPANTS:
Twenty participants with TBI presenting with anger problems and 22 healthy controls.
PROCEDURES:
Participants were administered tasks assessing emotion recognition (The French Evaluation Task) and anger expression (Anger regulation task). The latter, designed to elicit and modulate anger feelings through verbal recall of a self-experienced event, involved 4 recall conditions that followed a resting period: neutral, uninstructed anger recall, anger rumination, and anger reappraisal.
MEASURES:
Skin conductance levels during recall and a self-report anger questionnaire between each condition.
RESULTS:
In the TBI and control groups, self-reported anger was similarly modulated across emotion regulation conditions. However, only in the TBI group did skin conductance levels significantly increase between neutral and uninstructed anger recall conditions.
CONCLUSIONS:
Impaired emotion regulation in TBI participants could be related to increased levels of autonomic system activity during emotional experience. However, anger feelings in these participants can also be modulated with the use of emotion regulation strategies, including adaptive strategies such as reappraisal. Thus, promoting awareness and management of physiological activation and encouraging cognitive restructuring can be recommended as a component of interventions targeting emotion regulation in TBI patients
Mid-Infrared Emission Features in the ISM: Feature-to-Feature Flux Ratios
Using a limited, but representative sample of sources in the ISM of our
Galaxy with published spectra from the Infrared Space Observatory, we analyze
flux ratios between the major mid-IR emission features (EFs) centered around
6.2, 7.7, 8.6 and 11.3 microns, respectively. In a flux ratio-to-flux ratio
plot of EF(6.2)/EF(7.7) as a function of EF(11.3)/EF(7.7), the sample sources
form roughly a -shaped locus which appear to trace, on an overall
basis, the hardness of a local heating radiation field. But some driving
parameters other than the radiation field may also be required for a full
interpretation of this trend. On the other hand, the flux ratio of
EF(8.6)/EF(7.7) shows little variation over the sample sources, except for two
HII regions which have much higher values for this ratio due to an ``EF(8.6\um)
anomaly,'' a phenomenon clearly associated with environments of an intense
far-UV radiation field. If further confirmed on a larger database, these trends
should provide crucial information on how the EF carriers collectively respond
to a changing environment.Comment: 16 pages, 1 figure, 1 table; accepted for publication in ApJ Letter
NMR Spectroscopy: An Excellent Tool to Understand RNA and Carbohydrate Recognition by Proteins
Structural biology plays a key role in understanding how networks of protein interactions with their partners are organized at the atomic level. In this review, we show that NMR is a very efficient method to solve 3D structures of protein – RNA and protein–carbohydrate complexes
of high quality. We explain the importance of studying such interactions and describe the main steps that are required to determine structures of these types of complexes by NMR. Finally, we show that X-ray crystallography and NMR are complementary methods and briefly report on advantages
and disadvantages of each approach
Falls and other geriatric syndromes in Blantyre, Malawi: A community survey of older adults
Background: The prevalence of geriatric syndromes (falls, immobility,intellectual or memory impairment, and incontinence) is unknown inmany resource-poor countries. With an aging population such knowledgeis essential to develop national policies on the health and social needs ofolder people. The aim of this study was to provide a preliminary surveyto explore the prevalence of falls and other geriatric syndromes and theirassociation with known risk factors in people aged > 60 years in urbanBlantyre, Malawi.Methods: This was a cross-sectional, community survey of adults aged > 60 years. Subjects were recruited at home or in the waiting areas of chronic care clinics. They were interviewed to complete a questionnaire on ageassociated syndromes and comorbid problems. The Abbreviated MentalTest (AMT) and Timed Up and Go (TUG) tests were carried out.Results: Ninety-eight subjects were studied; 41% reported falling in the past 12 months, 33% of whom (13% of all subjects) were recurrent fallers.Twenty-five percent reported urine incontinence, 66% self-reported memory difficulties, and 11% had an AMT score < 7. A history of falling was significantly associated with urine incontinence (p=0.01), selfreportedmemory problems (p=0.004) and AMT score < 7 (p=0.02).Conclusions: Geriatric syndromes, including falls, appear to be prevalent in older people in Blantyre, Malawi. Falling is associated with cognitive impairment and urinary incontinence. There is an urgent need for more understanding of geriatric problems in this setting to develop national policies on health and social needs of older people. It is likely that many of the contributory factors to falls would be amenable to multifactorial interventions similar to those found to be effective in developed countries
Internal Dust Correction Factors for Star Formation Rates Derived for Dusty \HII Regions and Starburst Galaxies
Star formation rates in galaxies are frequently estimated using the Balmer
line fluxes. However, these can be systematically underestimated because dust
competes for the absorption of Lyman continuum photons in the ionized gas. Here
we present theoretical correction factors in a simple analytic form. T These
factors scale as the product of the ionization parameter, , and the
nebular O/H abundance ratio, both of which can now be derived from the
observation of bright nebular line ratios. The correction factors are only
somewhat dependent upon the photoelectron production by grains, but are very
sensitive to the presence of complex PAH-like carbonaceous molecules in the
ionized gas, providing that these can survive in such an environment.Comment: 13 pages, 1 figures, Accepted for publication in ApJ. (Feb 1, 2003
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