5,030 research outputs found
Parallel Imaging with RASER using Multiband Frequency-modulated Excitation Pulses
The many advantages of the recently proposed RASER sequence have been demonstrated. Hence, RASER holds great promises for functional MRI (fMRI), particularly for studies of the orbital-frontal cortex and other brain regions near air cavities, which cause distortion and signal loss in conventional EPI methods. However, the single-shot RASER sequence implemented so far inherently presents a set of temporal and spatial limitations that hinders it feasibility and full potential for fMRI applications. It is believed that parallel imaging will help overcome such restrictions. In this work, the RASER acquisition and reconstruction scheme is extended for parallel imaging using tailored pulses for simultaneous multi-band excitation
Studie zur untertaegigen Entsorgung und Verwertung bergbaufremder Stoffe in der Bundesrepublik Deutschland
Doubly resonant optical nanoantenna arrays for polarization resolved measurements of surface-enhanced Raman scattering
We report that rhomb-shaped metal nanoantenna arrays support multiple
plasmonic resonances, making them favorable bio-sensing substrates. Besides the
two localized plasmonic dipole modes associated with the two principle axes of
the rhombi, the sample supports an additional grating-induced surface plasmon
polariton resonance. The plasmonic properties of all modes are carefully
studied by far-field measurements together with numerical and analytical
calculations. The sample is then applied to surface-enhanced Raman scattering
measurements. It is shown to be highly efficient since two plasmonic resonances
of the structure were simultaneously tuned to coincide with the excitation and
the emission wave- length in the SERS experiment. The analysis is completed by
measuring the impact of the polarization angle on the SERS signal.Comment: 13 pages, 5 figure
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The influence of shock pressure, pre-shock temperature, and host rock composition on the survival rate of endolithic microorganisms during impact ejection from Mars
Petrographic and biological analysis of shock recovery experiments confirms the possible life transport due to an impact from Mars to Earth
D-Foam Phenomenology: Dark Energy, the Velocity of Light and a Possible D-Void
In a D-brane model of space-time foam, there are contributions to the dark
energy that depend on the D-brane velocities and on the density of D-particle
defects. The latter may also reduce the speeds of photons linearly with their
energies, establishing a phenomenological connection with astrophysical probes
of the universality of the velocity of light. Specifically, the cosmological
dark energy density measured at the present epoch may be linked to the apparent
retardation of energetic photons propagating from nearby AGNs. However, this
nascent field of `D-foam phenomenology' may be complicated by a dependence of
the D-particle density on the cosmological epoch. A reduced density of
D-particles at redshifts z ~ 1 - a `D-void' - would increase the dark energy
while suppressing the vacuum refractive index, and thereby might reconcile the
AGN measurements with the relatively small retardation seen for the energetic
photons propagating from GRB 090510, as measured by the Fermi satellite.Comment: 10 pages, 3 figure
Visualization of class A GPCR oligomerization by image-based fluorescence fluctuation spectroscopy
G protein-coupled receptors (GPCRs) represent the largest class of cell surface receptors conveying extracellular information into intracellular signals. Many GPCRs have been shown to be able to oligomerize and it is firmly established that Class C GPCRs (e.g. metabotropic glutamate receptors) function as obligate dimers. However, the oligomerization capability of the larger Class A GPCRs (e.g. comprising the β-adrenergic receptors (β-ARs)) is still, despite decades of research, highly debated. Here we assess the oligomerization behavior of three prototypical Class A GPCRs, the β1-ARs, β2-ARs, and muscarinic M2Rs in single, intact cells. We combine two image correlation spectroscopy methods based on molecular brightness, i.e. the analysis of fluorescence fluctuations over space and over time, and thereby provide an assay able to robustly and precisely quantify the degree of oligomerization of GPCRs. In addition, we provide a comparison between two labelling strategies, namely C-terminally-attached fluorescent proteins and N-terminally-attached SNAP-tags, in order to rule out effects arising from potential fluorescent protein-driven oligomerization. The degree of GPCR oligomerization is expressed with respect to a set of previously reported as well as newly established monomeric or dimeric control constructs. Our data reveal that all three prototypical GPRCs studied display, under unstimulated conditions, a prevalently monomeric fingerprint. Only the β2-AR shows a slight degree of oligomerization. From a methodological point of view, our study suggests three key aspects. First, the combination of two image correlation spectroscopy methods allows addressing cells transiently expressing high concentrations of membrane receptors, far from the single molecule regime, at a density where the kinetic equilibrium should favor dimers and higher-order oligomers. Second, our methodological approach, allows to selectively target cell membrane regions devoid of artificial oligomerization hot-spots (such as vesicles). Third, our data suggest that the β1-AR appears to be a superior monomeric control than the widely used membrane protein CD86. Taken together, we suggest that our combined image correlation spectroscopy method is a powerful approach to assess the oligomerization behavior of GPCRs in intact cells at high expression levels
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