467 research outputs found
Proteome-level display by 2-dimensional chromatography of extracellular matrix-dependent modulation of the phenotype of bladder cancer cells
BACKGROUND: The extracellular matrix can have a profound effect upon the phenotype of cancer cells. Previous work has shown that growth of bladder cancer cells on a matrix derived from normal basement membrane suppresses many malignant features that are displayed when the cells are grown on a matrix that has been modified by malignant tumors. This work was undertaken to investigate proteome-level changes as determined by a new commercially available proteome display involving 2-dimensional chromatography for bladder cancer cells grown on different extracellular matrix preparations that modulate the expression of the malignant phenotype. RESULTS: Depending on the matrix, between 1300 and 2000 distinct peaks were detected by two-dimensional chromatographic fractionation of 2.1 â 4.4 mg of total cellular protein. The fractions eluting from the reversed-phase fractionation were suitable for mass spectrometric identification following only lyophilization and trypsin digestion and achieved approximately 10-fold higher sensitivity than was obtained with gel-based separations. Abundant proteins that were unique to cells grown on one of the matrices were identified by mass spectrometry. Following concentration, peaks of 0.03 AU provided unambiguous identification of protein components when 10% of the sample was analyzed, whereas peaks of 0.05 AU was approximately the lower limit of detection when the entire sample was separated on a gel and in-gel digestion was used. Although some fractions were homogeneous, others were not, and up to 3 proteins per fraction were identified. Strong evidence for post-translational modification of the unique proteins was noted. All 13 of the unique proteins from cells grown on Matrigel were related to MYC pathway. CONCLUSION: The system provides a viable alternative to 2-dimensional gel electrophoresis for proteomic display of biological systems. The findings suggest the importance of MYC to the malignant phenotype of bladder cancer cells
Fast algorithm for calculating two-photon absorption spectra
We report a numerical calculation of the two-photon absorption coefficient of
electrons in a binding potential using the real-time real-space higher-order
difference method. By introducing random vector averaging for the intermediate
state, the task of evaluating the two-dimensional time integral is reduced to
calculating two one-dimensional integrals. This allows the reduction of the
computation load down to the same order as that for the linear response
function. The relative advantage of the method compared to the straightforward
multi-dimensional time integration is greater for the calculation of non-linear
response functions of higher order at higher energy resolution.Comment: 4 pages, 2 figures. It will be published in Phys. Rev. E on 1, March,
199
Observation of the east-west anisotropy of the atmospheric neutrino flux
The east-west anisotropy, caused by the deflection of primary cosmic rays in
the Earth's magnetic field, is observed for the first time in the flux of
atmospheric neutrinos. Using a 45 kt-year exposure of the
Super-Kamiokande detector, 552 e-like and 633 mu-like horizontally-going
events are selected in the momentum range between 400 and 3000 MeV/c.
The azimuthal distribution of e-like and mu-like events agrees with the
expectation from atmospheric neutrino flux calculations that account for the
geomagnetic field, verifying that the geomagnetic field effects in the
production of atmospheric neutrinos in the GeV energy range are well
understood.Comment: 8 pages,3 figures revtex, submitted to PR
Light emission from a scanning tunneling microscope: Fully retarded calculation
The light emission rate from a scanning tunneling microscope (STM) scanning a
noble metal surface is calculated taking retardation effects into account. As
in our previous, non-retarded theory [Johansson, Monreal, and Apell, Phys. Rev.
B 42, 9210 (1990)], the STM tip is modeled by a sphere, and the dielectric
properties of tip and sample are described by experimentally measured
dielectric functions. The calculations are based on exact diffraction theory
through the vector equivalent of the Kirchoff integral. The present results are
qualitatively similar to those of the non-retarded calculations. The light
emission spectra have pronounced resonance peaks due to the formation of a
tip-induced plasmon mode localized to the cavity between the tip and the
sample. At a quantitative level, the effects of retardation are rather small as
long as the sample material is Au or Cu, and the tip consists of W or Ir.
However, for Ag samples, in which the resistive losses are smaller, the
inclusion of retardation effects in the calculation leads to larger changes:
the resonance energy decreases by 0.2-0.3 eV, and the resonance broadens. These
changes improve the agreement with experiment. For a Ag sample and an Ir tip,
the quantum efficiency is 10 emitted photons in the visible
frequency range per tunneling electron. A study of the energy dissipation into
the tip and sample shows that in total about 1 % of the electrons undergo
inelastic processes while tunneling.Comment: 16 pages, 10 figures (1 ps, 9 tex, automatically included); To appear
in Phys. Rev. B (15 October 1998
Measurement of radon concentrations at Super-Kamiokande
Radioactivity from radon is a major background for observing solar neutrinos
at Super-Kamiokande. In this paper, we describe the measurement of radon
concentrations at Super-Kamiokande, the method of radon reduction, and the
radon monitoring system. The measurement shows that the current low-energy
event rate between 5.0 MeV and 6.5 MeV implies a radon concentration in the
Super-Kamiokande water of less than 1.4 mBq/m.Comment: 11 pages, 4 figure
Evidence for an oscillatory signature in atmospheric neutrino oscillation
Muon neutrino disappearance probability as a function of neutrino flight
length L over neutrino energy E was studied. A dip in the L/E distribution was
observed in the data, as predicted from the sinusoidal flavor transition
probability of neutrino oscillation. The observed L/E distribution constrained
nu_mu nu_tau neutrino oscillation parameters; 1.9x10^-3 < Delta m^2 <
3.0x10^-3 eV^2 and \sin^2(2theta) > 0.90 at 90% confidence level.Comment: 5 pages, 5 figures, submitted to PR
Search for Supernova Relic Neutrinos at Super-Kamiokande
A search for the relic neutrinos from all past core-collapse supernovae was
conducted using 1496 days of data from the Super-Kamiokande detector. This
analysis looked for electron-type anti-neutrinos that had produced a positron
with an energy greater than 18 MeV. In the absence of a signal, 90% C.L. upper
limits on the total flux were set for several theoretical models; these limits
ranged from 20 to 130 nu_e bar cm^-2 s^-1. Additionally, an upper bound of 1.2
nu_e bar cm^-2 s^-1 was set for the supernova relic neutrino flux in the energy
region E_nu > 19.3 MeV.Comment: 4 pages, 2 figures. Submitted to Physical Review Letters. New version
includes corrections to Figure 1. Also, text has been shortened to conform
with the space limitations of PR
Search for nucleon decay via modes favored by supersymmetric grand unification models in Super-Kamiokande-I
We report the results for nucleon decay searches via modes favored by
supersymmetric grand unified models in Super-Kamiokande. Using 1489 days of
full Super-Kamiokande-I data, we searched for , , and modes. We found no
evidence for nucleon decay in any of these modes. We set lower limits of
partial nucleon lifetime 2.3, 1.3,
1.3 and 1.0 years at 90% confidence level for , , and modes, respectively. These results give a strong constraint on
supersymmetric grand unification models.Comment: 14 pages, 13 figure
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