483 research outputs found
Octopamine underlies the counter-regulatory response to a glucose deficit in honeybees (Apis mellifera)
An animalâs internal state is a critical parameter required for adaptation to
a given environment. An important aspect of an animalâs internal state is the
energy state that is adjusted to the needs of an animal by energy homeostasis.
Glucose is one essential source of energy, especially for the brain. A
shortage of glucose therefore triggers a complex response to restore the
animalâs glucose supply. This counter-regulatory response to a glucose deficit
includes metabolic responses like the mobilization of glucose from internal
glucose stores and behavioral responses like increased foraging and a rapid
intake of food. In mammals, the catecholamines adrenalin and noradrenalin take
part in mediating these counter-regulatory responses to a glucose deficit. One
candidate molecule that might play a role in these processes in insects is
octopamine (OA). It is an invertebrate biogenic amine and has been suggested
to derive from an ancestral pathway shared with adrenalin and noradrenalin.
Thus, it could be hypothesized that OA plays a role in the insectâs counter-
regulatory response to a glucose deficit. Here we tested this hypothesis in
the honeybee (Apis mellifera), an insect that, as an adult, mainly feeds on
carbohydrates and uses these as its main source of energy. We investigated
alterations of the hemolymph glucose concentration, survival, and feeding
behavior after starvation and examined the impact of OA on these processes in
pharmacological experiments. We demonstrate an involvement of OA in these
three processes in honeybees and conclude there is an involvement of OA in
regulating a beeâs metabolic, physiological, and behavioral response following
a phase of prolonged glucose deficit. Thus, OA in honeybees acts similarly to
adrenalin and noradrenalin in mammals in regulating an animalâs counter-
regulatory response
Nanometer precise adjustment of the silver shell thickness during automated Au-Ag core-shell nanoparticle synthesis in micro fluid segment sequences
In this work, a wet-chemical synthesis method for goldâsilver coreâshell particles with nanometer precise adjustable silver shell thicknesses is presented. Typically wet-chemical syntheses lead to relatively large diameter size distributions and losses in the yield of the desired particle structure due to thermodynamical effects. With the here explained synthesis method in micro fluidic segment sequences, a combinatorial in situ parameter screening of the reactant concentration ratios by programmed flow rate shifts in conjunction with efficient segment internal mixing conditions is possible. The highly increased mixing rates ensure a homogeneous shell deposition on all presented gold core particles while the amount of available silver ions was adjusted by automated flow rate courses, from which the synthesis conditions for exactly tunable shell thicknesses between 1.1 and 6.1 nm could be derived. The findings according to the homogeneity of size and particle structure were confirmed by differential centrifugal sedimentation (DCS), scanning and transmission electron microscopy (SEM, TEM) and X-ray photoelectron spectroscopy (XPS) measurements. In UV-Vis measurements, a significant contribution of the core metal was found in the shape of the extinction spectra in the case of thin shells. These results were confirmed by theoretical calculations
Strong negative feedback from Erk to Raf confers robustness to MAPK signalling
This study shows that MAPK signalling is robust against protein level changes due to a strong negative feedback from Erk to Raf. Surprisingly, robustness is provided through a fast post-translational mechanism although variation of Erk levels occurs on a timescale of days
Phospho-proteomic analyses of B-Raf protein complexes reveal new regulatory principles
B-Raf represents a critical physiological regulator of the Ras/RAF/MEK/ERK-pathway and a pharmacological target of growing clinical relevance, in particular in oncology. To understand how B-Raf itself is regulated, we combined mass spectrometry with genetic approaches to map its interactome in MCF-10A cells as well as in B-Raf deficient murine embryonic fibroblasts (MEFs) and B-Raf/Raf-1 double deficient DT40 lymphoma cells complemented with wildtype or mutant B-Raf expression vectors. Using a multi-protease digestion approach, we identified a novel ubiquitination site and provide a detailed B-Raf phospho-map. Importantly, we identify two evolutionary conserved phosphorylation clusters around T401 and S419 in the B-Raf hinge region. SILAC labelling and genetic/biochemical follow-up revealed that these clusters are phosphorylated in the contexts of oncogenic Ras, sorafenib induced Raf dimerization and in the background of the V600E mutation. We further show that the vemurafenib sensitive phosphorylation of the T401 cluster occurs in trans within a Raf dimer. Substitution of the Ser/Thr-residues of this cluster by alanine residues enhances the transforming potential of B-Raf, indicating that these phosphorylation sites suppress its signaling output. Moreover, several B-Raf phosphorylation sites, including T401 and S419, are somatically mutated in tumors, further illustrating the importance of phosphorylation for the regulation of this kinase
Multidifferential study of identified charged hadron distributions in -tagged jets in proton-proton collisions at 13 TeV
Jet fragmentation functions are measured for the first time in proton-proton
collisions for charged pions, kaons, and protons within jets recoiling against
a boson. The charged-hadron distributions are studied longitudinally and
transversely to the jet direction for jets with transverse momentum 20 GeV and in the pseudorapidity range . The
data sample was collected with the LHCb experiment at a center-of-mass energy
of 13 TeV, corresponding to an integrated luminosity of 1.64 fb. Triple
differential distributions as a function of the hadron longitudinal momentum
fraction, hadron transverse momentum, and jet transverse momentum are also
measured for the first time. This helps constrain transverse-momentum-dependent
fragmentation functions. Differences in the shapes and magnitudes of the
measured distributions for the different hadron species provide insights into
the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb
public pages
Study of the decay
The decay is studied
in proton-proton collisions at a center-of-mass energy of TeV
using data corresponding to an integrated luminosity of 5
collected by the LHCb experiment. In the system, the
state observed at the BaBar and Belle experiments is
resolved into two narrower states, and ,
whose masses and widths are measured to be where the first uncertainties are statistical and the second
systematic. The results are consistent with a previous LHCb measurement using a
prompt sample. Evidence of a new
state is found with a local significance of , whose mass and width
are measured to be and , respectively. In addition, evidence of a new decay mode
is found with a significance of
. The relative branching fraction of with respect to the
decay is measured to be , where the first
uncertainty is statistical, the second systematic and the third originates from
the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb
public pages
Measurement of the ratios of branching fractions and
The ratios of branching fractions
and are measured, assuming isospin symmetry, using a
sample of proton-proton collision data corresponding to 3.0 fb of
integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The
tau lepton is identified in the decay mode
. The measured values are
and
, where the first uncertainty is
statistical and the second is systematic. The correlation between these
measurements is . Results are consistent with the current average
of these quantities and are at a combined 1.9 standard deviations from the
predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb
public pages
Characterisation of the electronic and chemical properties of as-grown polar InN surfaces and their changes during the interaction with adsorbates
ï»żIndium nitride (InN) is a III-V semiconductor and due to its low band gap
and good electron transport properties a promising candidate for
applications in ultrafast transistor and optoelectronic devices. In this
context, not only the bulk but also the surface properties of the material
are of major interest.This thesis is devoted to the investigation of the
electronic and chemical surface properties of as-grown as well as adsorbate
covered, polar InN. The InN layers were grown by plasma-assisted molecular
beam epitaxy (MBE) and in-situ characterised by Reflection High Energy
Electron Diffraction (RHEED) as well as X-ray and Ultraviolet Photoelectron
Spectroscopy (XPS, UPS). The experimental results imply clear differences
in the electronic properties of the polar surfaces due to differences of
the atomic structure. At the In-polar InN surface, a 2Ă2 reconstruction,
connected with surface states at the Fermi level is responsible for a
strong electron accumulation at these InN(0001)- 2Ă2 surfaces. In contrast,
N-polar InN shows a 1Ă1 surface with occupied surface states at the valence
band maximum (at ~ 1,6 eV), connected with a considerably reduced surface
downward band bending. Furthermore, changes of the InN surface properties
due to adsorbate interaction were systematically studied using UPS and XPS
with a special focus on the influence of oxygen and water as important
components of the ambient air. The experimental results were discussed with
regard to adsorbate bonding, dipole layer formation as well as changes in
the surface band bending.Thereby, oxygen atomically bonds to the InN
surfaces, acting as electron acceptor and reducing the surface downward
band bending of the In-polar InN, while almost no change of the already
reduced band bending at N-polar InN is observed. However, the interaction
with water results in a strong downward band bending and electron
accumulation for both polarities.Indiumnitrid (InN) gehört zu den III-V Halbleitern und ist durch seine
geringe BandlĂŒcke sowie seine guten Elektronentransporteigenschaften ein
vielversprechender Kandidat fĂŒr den Einsatz in ultraschnellen Transistoren
und optoelektronischen Bauelementen. Dabei spielen neben den
Volumeneigenschaften des Materials vor allem auch die
OberflÀcheneigenschaften eine entscheidende Rolle. Die vorliegende Arbeit
beschÀftigt sich mit der Charakterisierung der elektronischen und
chemischen OberflÀcheneigenschaften von reinem sowie adsorbatbedecktem,
polarem InN. Die InN-Schichten wurden mittels plasmaunterstĂŒtzter
Molekularstrahlepitaxie (MBE) abgeschieden und in-situ anhand der Beugung
hochenergetischer Elektronen (RHEED) sowie mittels Röntgen- und
Ultraviolett-Photoelektronenspektroskopie (XPS, UPS) untersucht. Hierbei
zeigten sich deutliche Unterschiede in den elektronischen Eigenschaften der
polaren OberflÀchen, die vor allem auf die unterschiedlichen atomaren
Strukturen zurĂŒckgefĂŒhrt werden konnten. So kommt es an der In-polaren
InN-OberflĂ€che zur Ausbildung einer 2Ă2 OberflĂ€chenrekonstruktion, die zu
OberflĂ€chenzustĂ€nden nahe des Ferminiveaus fĂŒhren, welche zur Ausbildung
einer starken Elektronenakkumulationsschicht an den InN(0001)-2Ă2
OberflÀchen beitragen. Beim reinen N-polaren InN beobachtet man im
Gegensatz dazu eine 1Ă1-OberflĂ€che mit besetzten OberflĂ€chenzustĂ€nden nahe
des Valenzbandminimums (bei ~ 1,6 eV), verbunden mit einer deutlich
reduzierten OberflÀchenabwÀrtsbandverbiegung. Weiterhin wurden
VerÀnderungen der InN-OberflÀchen durch Adsorbatwechselwirkungen
systematisch mittels UPS und XPS untersucht und dabei der Einfluss des
Sauerstoffs und des Wassers als wichtige Bestandteile der Luft detailliert
betrachtet. Die experimentellen Ergebnisse werden im Hinblick auf
Informationen zur Anbindung der Adsorbatspezies, zur Dipolbildung sowie zur
Beeinflussung der OberflÀchenelektronen und damit der
OberflÀchenbandverbiegung der InN-Proben diskutiert. Dabei zeigt sich, dass
Sauerstoff in atomarer Form an die InN-OberflÀchen bindet und als
Elektronenakzeptor zur Reduzierung der AbwÀrtsbandverbiegung an den
In-polaren InN-Proben beitrÀgt bzw. kaum einen Einfluss auf die bereits
reduzierte Bandverbiegung des N-polaren InN hat. Die Wechselwirkung mit
Wasser fĂŒhrt dagegen bei beiden PolaritĂ€ten zu einer deutlich ausgeprĂ€gten
Elektronenakkumulation
- âŠ