5,290 research outputs found
Autophagosome formation is initiated at phosphatidylinositol synthaseâenriched ER subdomains
The autophagosome, a doubleâmembrane structure mediating degradation of cytoplasmic materials by macroautophagy, is formed in close proximity to the endoplasmic reticulum (ER). However, how the ER membrane is involved in autophagy initiation and to which membrane structures the autophagyâinitiation complex is localized have not been fully characterized. Here, we were able to biochemically analyze autophagic intermediate membranes and show that the autophagyâinitiation complex containing ULK and FIP200 first associates with the ER membrane. To further characterize the ER subdomain, we screened phospholipid biosynthetic enzymes and found that the autophagyâinitiation complex localizes to phosphatidylinositol synthase (PIS)âenriched ER subdomains. Then, the initiation complex translocates to the ATG9Aâpositive autophagosome precursors in a PI3Pâdependent manner. Depletion of phosphatidylinositol (PI) by targeting bacterial PIâspecific phospholipase C to the PIS domain impairs recruitment of downstream autophagy factors and autophagosome formation. These findings suggest that the autophagyâinitiation complex, the PISâenriched ER subdomain, and ATG9A vesicles together initiate autophagosome formation
Stability of 1-D Excitons in Carbon Nanotubes under High Laser Excitations
Through ultrafast pump-probe spectroscopy with intense pump pulses and a wide
continuum probe, we show that interband exciton peaks in single-walled carbon
nanotubes (SWNTs) are extremely stable under high laser excitations. Estimates
of the initial densities of excitons from the excitation conditions, combined
with recent theoretical calculations of exciton Bohr radii for SWNTs, suggest
that their positions do not change at all even near the Mott density. In
addition, we found that the presence of lowest-subband excitons broadens all
absorption peaks, including those in the second-subband range, which provides a
consistent explanation for the complex spectral dependence of pump-probe
signals reported for SWNTs.Comment: 4 pages, 4 figure
The dissipative effect of thermal radiation loss in high-temperature dense plasmas
A dynamical model based on the two-fluid dynamical equations with energy
generation and loss is obtained and used to investigate the self-generated
magnetic fields in high-temperature dense plasmas such as the solar core. The
self-generation of magnetic fields might be looked at as a
self-organization-type behavior of stochastic thermal radiation fields, as
expected for an open dissipative system according to Prigogine's theory of
dissipative structures.Comment: 4 pages, 1 postscript figure included; RevTeX3.0, epsf.tex neede
Effects of Unilateral Compound-Eye Removal on the Photoperiodic Responses of Nymphal Development in the Cricket Modicogryllus siamensis
The cricket, Modicogryllus siamensis, shows clear photoperiodic responses at 25 degrees C in nymphal development. Under long-day conditions (LD16:8), nymphs became adults about 50 days after hatching, while under short-day conditions (LD8:16) the duration of nymphal stage extended to more than 130 days. Under constant dark conditions, two developmental patterns were observed: about 60% of crickets became adults slightly slower than under the long-day conditions, and the rest at later than 100 days after hatching, like those under the short-day conditions. When the compound eye was unilaterally removed on the 2nd day of hatching, an increase of molting and an extension of the nymphal period were observed under the long-day conditions, while under the short-day conditions, some crickets developed faster and others slower than intact crickets. These results suggest that this cricket receives photoperiodic information through the compound eye, that a pair of the compound eyes is required for a complete photoperiodic response, and that interaction between bilateral circadian clocks may be also involved in the response
Chirality-Selective Excitation of Coherent Phonons in Carbon Nanotubes
Using pre-designed trains of femtosecond optical pulses, we have selectively
excited coherent phonons of the radial breathing mode of specific-chirality
single-walled carbon nanotubes within an ensemble sample. By analyzing the
initial phase of the phonon oscillations, we prove that the tube diameter
initially increases in response to ultrafast photoexcitation. Furthermore, from
excitation profiles, we demonstrate that an excitonic absorption peak of carbon
nanotubes periodically oscillates as a function of time when the tube diameter
undergoes radial breathing mode oscillations.Comment: 4 pages, 4 figure
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