290 research outputs found
Die Wiederansiedlung von FlĆ¼chtlingen in der Schweiz: Eine Analyse der bisherigen Praxis und Diskussion von Handlungsoptionen
We
report herein an iron-catalyzed azidotrifluoromethylation method
for expedient vicinal trifluoromethyl primary-amine synthesis. This
method is effective for a broad range of olefins and N-heterocycles,
and it facilitates efficient synthesis of a wide variety of vicinal
trifluoromethyl primary amines, including those that prove difficult
to synthesize with existing approaches. Our preliminary mechanistic
studies revealed that the catalyst-promoted azido-group transfer proceeds
through a carbo-radical instead of a carbocation species. Characterization
of an active iron catalyst through X-ray crystallographic studies
suggests that in situ generated, structurally novel iron-azide complexes
promote the oxidant activation and selective azido-group transfer
<b>Associations between cyberbullying and school bullying victimization and suicidal ideation, plans and attempts.</b>
<p><b>Associations between cyberbullying and school bullying victimization and suicidal ideation, plans and attempts.</b></p
Photon Reabsorption and Nonradiative Energy-Transfer-Induced Quenching of Blue Photoluminescence from Aggregated Graphene Quantum Dots
A deep
understanding of the photoluminescence (PL) from aggregated graphene
quantum dots (GQDs) is very important for their practical applications.
Here the PL spectra from GQDs solutions at different concentrations
are studied. We find that the intensity of the green emission (ca.
530ā560 nm) linearly relies on the concentration of GQDs, whereas
the blue PL (ca. 425 nm) intensity is below the linear relationship,
indicating a concentration-induced partial quenching of blue PL. Confocal
fluorescence images explicitly demonstrate the aggregation of GQDs
at high concentration. The concentration-induced PL quenching is successfully
interpreted by a model of photon reabsorption and nonradiative energy
transfer, indicating that, at the aggregated states, the excited electrons
of GQDs may nonradiatively relax to ground states through couplings
with neighboring ones. Simulated fluorescence decay results show that
the energy transfer between neighboring GQDs results in a prolonged
dwell time of electron on high-energy state and thus increases the
decay time of 425 nm emission, while 550 nm emission remains unaffected,
which is consistent with the experimental results. This work will
contribute to a deep understanding on PL of GQDs and is also of huge
importance to extend GQDsā applications
Mediational model for study of the relationship between cyberbullying and school bullying victimization and suicidal ideation, plans and attempts.
<p>Mediational model for study of the relationship between cyberbullying and school bullying victimization and suicidal ideation, plans and attempts.</p
Differential Effects of Munc18s on Multiple Degranulation-Relevant Trans-SNARE Complexes
<div><p>Mast cell exocytosis, which includes compound degranulation and vesicle-associated piecemeal degranulation, requires multiple Q- and R- SNAREs. It is not clear how these SNAREs pair to form functional trans-SNARE complexes and how these trans-SNARE complexes are selectively regulated for fusion. Here we undertake a comprehensive examination of the capacity of two Q-SNARE subcomplexes (syntaxin3/SNAP-23 and syntaxin4/SNAP-23) to form fusogenic trans-SNARE complexes with each of the four granule-borne R-SNAREs (VAMP2, 3, 7, 8). We report the identification of at least six distinct trans-SNARE complexes under enhanced tethering conditions: i) VAMP2/syntaxin3/SNAP-23, ii) VAMP2/syntaxin4/SNAP-23, iii) VAMP3/syntaxin3/SNAP-23, iv) VAMP3/syntaxin4/SNAP-23, v) VAMP8/syntaxin3/SNAP-23, and vi) VAMP8/syntaxin4/SNAP-23. We show for the first time that Munc18a operates synergistically with SNAP-23-based non-neuronal SNARE complexes (i to iv) in lipid mixing, in contrast to Munc18b and c, which exhibit no positive effect on any SNARE combination tested. Pre-incubation with Munc18a renders the SNARE-dependent fusion reactions insensitive to the otherwise inhibitory R-SNARE cytoplasmic domains, suggesting a protective role of Munc18a for its cognate SNAREs. Our findings substantiate the recently discovered but unexpected requirement for Munc18a in mast cell exocytosis, and implicate post-translational modifications in Munc18b/c activation.</p></div
<b>Sample Characteristics.</b>
<p>Data are shown as n (%).</p><p>*Time usually spent on the computer, including playing computer games and accessing the Internet on a typical day.</p>ā <p>Time usually spent on sedentary activities including playing video games, such as XBOX, Nintendo and/or PlayStation, watching television or movies, and reading, not counting reading at school or at work.</p>ā”<p>Ever had at least one drink of alcohol, other than a few sips.</p>Ā§<p>Ever smoked a whole cigarette.</p>||<p>Type of marijuana user.</p>Ā¶<p><i>p</i> value of association with cyberbullying victimization.</p
<b>Prevalence of suicidal ideation and suicide-related behaviour among Canadian middle and high school students.</b>
<p>Data are shown as n (%).</p><p>*<i>p</i> value of difference between boys and girls.</p
Ī±SNAP/NSF-dependent inhibition of SNARE-mediated lipid mixing.
<p>(A and B) VAMP2-bearing donor RPLs were incubated with specified acceptor RPLs in fusion reactions containing 0.5mM ATP, 0.5mM MgCl<sub>2</sub>, and 4% PEG6000. Also included in the reactions are specified amounts of NSF along with 0.5Ī¼M Ī±SNAP (A) or 0.15Ī¼M Ī±SNAP (B). (C and D) VAMP3-bearing donor RPLs were incubated with specified acceptor RPLs in fusion reactions containing 1mM ATP, 1mM MgCl<sub>2</sub>, and 4% PEG6000. Also included in the reactions are specified amounts of NSF along with 0.15Ī¼M Ī±SNAP. (E and F) VAMP8-bearing donor RPLs were incubated with specified acceptor RPLs in standard reactions containing 0.5mM ATP and 0.5mM MgCl<sub>2</sub>. Also included in the reactions are specified amounts of NSF along with 0.1Ī¼M Ī±SNAP (E) or 0.02Ī¼M Ī±SNAP (F). All samples contained the same amounts of Ī±SNAP buffer and NSF buffer. The maximal early rates of lipid mixing for the SNARE-only reactions were used to generate the āstandardā value (the lipid-mixing rate from SNARE-free RPLs was treated as a background and subtracted) and set as 100%. The values for other conditions were adjusted relative to the āstandardā value. Error bars represent standard deviations from three independent experiments.</p
Munc18a selectively regulates different trans-SNARE complexes.
<p>Various combinations of donor and acceptor RPLs as specified were incubated overnight at 4Ā°C with Munc18a (2Ī¼M) or control buffer, before transferring to 37Ā°C. Error bars represent standard deviations from three independent experiments. p values were calculated using Studentās t test. ** indicates p < 0.01.</p
Munc18a-dependent stimulation is sensitive to inhibitory proteins at an early stage of the fusion reaction.
<p>(A). Acceptor RPLs bearing untagged syntaxin4/His<sub>6</sub>-SNAP-23 and VAMP2-bearing donor RPLs were incubated with inhibitory proteins VAMP2cd (2Ī¼M) or VAMP8cd (2Ī¼M) or buffer on ice overnight and then received 5Ī¼M Munc18a or MBP (control). The incubation was continued on ice for another 90 min before shifting to 37Ā°C. Fold increases in the initial lipid-mixing rates of the fusion reactions are shown. In (B), the same RPLs were incubated first with 5Ī¼M Munc18a on ice for 90 min before the addition of VAMP2cd (2Ī¼M) or VAMP8cd (2Ī¼M). Following overnight incubation on ice, samples were transferred to 37Ā°C to monitor NBD fluorescence. The maximal early rates of lipid mixing for the Munc18a-only reactions were used to generate the āstandardā value and set as 100%. The values for other conditions were adjusted relative to the āstandardā value. Error bars represent standard deviations from three independent experiments.</p
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