39 research outputs found
Development of a large area gas photomultiplier with GEM/PIC
We are developing a new photon detector with micro pattern gaseous detectors.
A semitransparent CsI photocathode is combined with 10cm10cm
GEM/PIC for the first prototype which is aimed for the large liquid Xe
detectors. Using Ar+CH (10%) gas, we achieved the gas gain of
which is enough to detect single photoelectron. We, then, irradiated UV photons
from a newly developed solid scintillator, LaF(Nd), to the detector and
successfully detected single photoelectron.Comment: Poster presentation at ICHEP08 Philadelphia, USA, July 2008. 3 pages,
LaTeX, 4 eps figure
Real-time observation of X-ray-induced intramolecular and interatomic electronic decay in CH2I2
The increasing availability of X-ray free-electron lasers (XFELs) has catalyzed the development of single-object structural determination and of structural dynamics tracking in realtime. Disentangling the molecular-level reactions triggered by the interaction with an XFEL pulse is a fundamental step towards developing such applications. Here we report real-time observations of XFEL-induced electronic decay via short-lived transient electronic states in the diiodomethane molecule, using a femtosecond near-infrared probe laser. We determine the lifetimes of the transient states populated during the XFEL-induced Auger cascades and find that multiply charged iodine ions are issued from short-lived (similar to 20 fs) transient states, whereas the singly charged ones originate from significantly longer-lived states (similar to 100 fs). We identify the mechanisms behind these different time scales: contrary to the short-lived transient states which relax by molecular Auger decay, the long-lived ones decay by an interatomic Coulombic decay between two iodine atoms, during the molecular fragmentation
Experimental Evaluation of the Density of Water in a Cell by Raman Microscopy
We report direct observation of a
spatial distribution of water
molecules inside of a living cell using Raman images of the OâH
stretching band of water. The OâH Raman intensity of the nucleus
was higher than that of the cytoplasm, indicating that the water density
is higher in the nucleus than that in the cytoplasm. The shape of
the OâH stretching band of the nucleus differed from that of
the cytoplasm but was similar to that of the balanced salt solution
surrounding cells, indicating less crowded environments in the nucleus.
The concentration of biomolecules having CâH bonds was also
estimated to be lower in the nucleus than that in the cytoplasm. These
results indicate that the nucleus is less crowded with biomolecules
than the cytoplasm
Embedding a Metal-Binding Motif for Copper Transporter into a Lipid Bilayer by Cu(I) Binding
Peptideâlipid
interactions are widely involved with biologically
significant phenomena, including the pathogenic mechanisms of protein
misfolding diseases and transmembrane protein folding. In this paper,
the interaction of the cysteine/tryptophan (Cys/Trp) motif, which
is a metal-binding motif of copper transporter (Ctr) proteins, with
a lipid bilayer was studied using fluorescence and circular dichroism
(CD) spectroscopy. The binding of CuÂ(I) to the Cys/Trp motif induced
a large red-edge excitation shift in the Trp fluorescence, indicating
that the Trp residue is located inside the lipid bilayer following
complexation of CuÂ(I) with the Cys/Trp motif. The SternâVolmer
quenching of the Trp fluorescence also supported the CuÂ(I) binding
peptide embedding in the lipid bilayer. The measurement of the CD
spectra indicated the increase in ÎČ-sheet content of the Cys/Trp
motif peptide as a result of CuÂ(I) binding. These results lead to
the conclusion that complexation with CuÂ(I) induces the change in
the secondary structure of the Cys/Trp motif, which results in the
peptide embedding in the lipid bilayer. CuÂ(I)-induced enhancement
of the lipid affinity is discussed in terms of the mechanism for copper
transport by Ctr
Time-Resolved Structured Illumination Microscopy for Phase Separation Dynamics of Water and 2-Butoxyethanol Mixtures: Interpretation of "Early Stage" Involving Micelle-Like Structures
Phase separation dynamics of a water/2-butoxyethanol (2BE) mixture was studied with newly developed time-resolved structured illumination microscopy (SIM). Interestingly, an employed hydrophobic fluorescent probe for SIM showed spectral shifts up to 500 ns after a laser-induced temperature jump, which suggests 2BE micellar-like aggregates become more hydrophobic at the initial stage of phase separation. This hydrophobic environment in 2BE aggregates, probably due to the ejection of water molecules, continued up to at least 10 ÎŒs. Time-resolved SIM and previously reported light scattering data clearly showed that the size of a periodic structure remained constant (ca. 300 nm) from 3 to 10 ÎŒs, and then the growth of periodic structures having the self-similarity started. We think that the former and the latter processes correspond to "early stage" (concentration growth) and "late stage" (size growth), respectively, in phase separation dynamics. Here we suggest that, in the early stage, the entity to bear 2BE phase be water-poor 2BE aggregates, and the number density of these aggregates would simply increase in time.status: publishe