3,608 research outputs found
Identification of Epstein-Barr virus replication proteins in Burkitt’s lymphoma cells
The working model to describe the mechanisms used to replicate the cancer-associated virus Epstein-Barr virus (EBV) is partly derived from comparisons with other members of the Herpes virus family. Many genes within the EBV genome are homologous across the herpes virus family. Published transcriptome data for the EBV genome during its lytic replication cycle show extensive transcription, but the identification of the proteins is limited. We have taken a global proteomics approach to identify viral proteins that are expressed during the EBV lytic replication cycle. We combined an enrichment method to isolate cells undergoing EBV lytic replication with SILAC-labeling coupled to mass-spectrometry and identified viral and host proteins expressed during the OPEN ACCESS Pathogens 2015, 4 740 EBV lytic replication cycle. Amongst the most frequently identified viral proteins are two components of the DNA replication machinery, the single strand DNA binding protein BALF2, DNA polymerase accessory protein BMRF1 and both subunits of the viral ribonucleoside-diphosphate reductase enzyme (BORF2 and BaRF1). An additional 42 EBV lytic cycle proteins were also detected. This provides proteomic identification for many EBV lytic replication cycle proteins and also identifies post-translational modifications
Suppressed dependence of polarization on epitaxial strain in highly polar ferroelectrics
A combined experimental and computational investigation of coupling between
polarization and epitaxial strain in highly polar ferroelectric
PbZr_0.2Ti_0.8O_3 (PZT) thin films is reported. A comparison of the properties
of relaxed (tetragonality c/a = 1.05) and highly-strained (c/a = 1.09)
epitaxial films shows that polarization, while being amongst the highest
reported for PZT or PbTiO_3 in either film or bulk forms (P_r = 82
microC/cm^2), is almost independent of the epitaxial strain. We attribute this
behavior to a suppressed sensitivity of the A-site cations to epitaxial strain
in these Pb-based perovskites, where the ferroelectric displacements are
already large, contrary to the case of less polar perovskites, such as BaTiO_3.
In the latter case, the A-site cation (Ba) and equatorial oxygen displacements
can lead to substantial polarization increases.Comment: 4 pages, 3 figure
Using MOST to reveal the secrets of the mischievous Wolf-Rayet binary CV Ser
The WR binary CV Serpentis (= WR113, WC8d + O8-9IV) has been a source of
mystery since it was shown that its atmospheric eclipses change with time over
decades, in addition to its sporadic dust production. The first high-precision
time-dependent photometric observations obtained with the MOST space telescope
in 2009 show two consecutive eclipses over the 29d orbit, with varying depths.
A subsequent MOST run in 2010 showed a seemingly asymmetric eclipse profile. In
order to help make sense of these observations, parallel optical spectroscopy
was obtained from the Mont Megantic Observatory (2009, 2010) and from the
Dominion Astrophysical Observatory (2009). Assuming these depth variations are
entirely due to electron scattering in a beta-law wind, an unprecedented 62%
increase in mass-loss rate is observed over one orbital period. Alternatively,
no change in mass-loss rate would be required if a relatively small fraction of
the carbon ions in the wind globally recombined and coaggulated to form carbon
dust grains. However, it remains a mystery as to how this could occur. There
also seems to be evidence for the presence of corotating interaction regions
(CIR) in the WR wind: a CIR-like signature is found in the light curves,
implying a potential rotation period for the WR star of 1.6 d. Finally, a new
circular orbit is derived, along with constraints for the wind collision.Comment: 11 pages, 11 figures, 5 table
Examination of the role of methylenetetrahydrofolate reductase in incorporation of methyltetrahydrofolate into cellular metabolism
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154338/1/fsb2002001005.pd
A Five-coordinate Metal Center in Co(II)-substituted VanX
In an effort to structurally probe the metal binding site in VanX, electronic absorption, EPR, and extended x-ray absorption fine structure (EXAFS) spectroscopic studies were conducted on Co(II)-substituted VanX. Electronic spectroscopy revealed the presence of Co(II) ligand field transitions that had molar absorptivities of ∼100 m–1 cm–1, which suggests that Co(II) is five-coordinate in Co(II)-substituted VanX. Low temperature EPR spectra of Co(II)-substituted VanX were simulated using spin Hamiltonian parameters of M = |±½〉, E/D = 0.14, greal(x,y) = 2.37, and grealS(z) = 2.03. These parameters lead to the prediction that Co(II) in the enzyme is five-coordinate and that there may be at least one solvent-derived ligand. Single scattering fits of EXAFS data indicate that the metal ions in both native Zn(II)-containing and Co(II)-substituted VanX have the same coordination number and that the metal ions are coordinated by 5 nitrogen/oxygen ligands at ∼ 2.0 Å. These data demonstrate that Co(II) (and Zn(II) from EXAFS studies) is five-coordinate in VanX in contrast to previous crystallographic studies (Bussiere, D. E., Pratt, S. D., Katz, L., Severin, J. M., Holzman, T., and Park, C. H. (1998) Mol. Cell 2, 75–84). These spectroscopic studies also demonstrate that the metal ion in Co(II)-substituted VanX when complexed with a phosphinate analog of substrate d-Ala-d-Ala is also five-coordinate
A stable quasi-periodic 4.18 d oscillation and mysterious occultations in the 2011 MOST light curve of TWHya
We present an analysis of the 2011 photometric observations of TW Hya by the
MOST satellite; this is the fourth continuous series of this type. The
large-scale light variations are dominated by a strong, quasi-periodic 4.18 d
oscillation with superimposed, apparently chaotic flaring activity; the former
is most likely produced by stellar rotation with one large hot spot created by
a stable accretion funnel in the stable regime of accretion while the latter
may be produced by small hot spots, created at moderate latitudes by unstable
accretion tongues. A new, previously unnoticed feature is a series of
semi-periodic, well defined brightness dips of unknown nature of which 19 were
observed during 43 days of our nearly-continuous observations. Re-analysis of
the 2009 MOST light curve revealed the presence of 3 similar dips. On the basis
of recent theoretical results, we tentatively conclude that the dips may
represent occultations of the small hot spots created by unstable accretion
tongues by hypothetical optically thick clumps.Comment: Printed in MNRA
Photometric variability in FU Ori and Z CMa as observed by MOST
Photometric observations obtained by the MOST satellite were used to
characterize optical small scale variability of the young stars FU Ori and Z
CMa. Wavelet analysis for FU Ori reveals the possible existence of several 2-9
d quasi-periodic features occurring nearly simultaneously; they may be
interpreted as plasma parcels or other localized disc heterogeneities revolving
at different Keplerian radii in the accretion disc. Their periods may shorten
slowly which may be due to spiralling in of individual parcels toward the inner
disc radius, estimated at 4.8+/-0.2 R_sun. Analysis of additional multicolour
data confirms the previously obtained relation between variations in the B-V
colour index and the V magnitude. In contrast to the FU Ori results, the
oscillation spectrum of Z CMa does not reveal any periodicities with the
wavelet spectrum possibly dominated by outburst of the Herbig Be component.Comment: Accepted by MNRA
- …