2,381 research outputs found
Crystal structure of the catalytic fragment of murine poly(ADP-ribose) polymerase-2.
Poly(ADP-ribose) polymerase-1 (PARP-1) has become an important pharmacological target in the treatment of cancer due to its cellular role as a 'DNA-strand break sensor', which leads in part to resistance to some existing chemo- and radiological treatments. Inhibitors have now been developed which prevent PARP-1 from synthesizing poly(ADP-ribose) in response to DNA-breaks and potentiate the cytotoxicity of DNA damaging agents. However, with the recent discoveries of PARP-2, which has a similar DNA-damage dependent catalytic activity, and additional members containing the 'PARP catalytic' signature, the isoform selectivity and resultant pharmacological effects of existing inhibitors are brought into question. We present here the crystal structure of the catalytic fragment of murine PARP-2, at 2.8 A resolution, and compare this to the catalytic fragment of PARP-1, with an emphasis on providing a possible framework for rational drug design in order to develop future isoform-specific inhibitors
Matter effects in the D0-D0bar system
We discuss the impact of matter effects in the D0-D0bar system. We show that
such effects could, in principle, be measured, but that they cannot be used to
probe the mass difference x_D or the lifetime difference y_D. This occurs
because the mixing effects and the matter effects decouple at short times. We
also comment briefly on the B systems.Comment: 6 pages, RevTe
Testing the Principle of Equivalence by Solar Neutrinos
We discuss the possibility of testing the principle of equivalence with solar
neutrinos. If there exists a violation of the equivalence principle quarks and
leptons with different flavors may not universally couple with gravity. The
method we discuss employs a quantum mechanical phenomenon of neutrino
oscillation to probe into the non-universality of the gravitational couplings
of neutrinos. We develop an appropriate formalism to deal with neutrino
propagation under the weak gravitational fields of the sun in the presence of
the flavor mixing. We point out that solar neutrino observation by the next
generation water Cherenkov detectors can improve the existing bound on
violation of the equivalence principle by 3-4 orders of magnitude if the
nonadiabatic Mikheyev-Smirnov-Wolfenstein mechanism is the solution to the
solar neutrino problem.Comment: Latex, 17 pages + 6 uuencoded postscript figures, KEK-TH-396,
TMUP-HEL-9402 (unnecessary one reference was removed
Dynamical derivation of Bode's law
In a planetary or satellite system, idealized as n small bodies in initially
coplanar, concentric orbits around a large central body, obeying Newtonian
point-particle mechanics, resonant perturbations will cause dynamical evolution
of the orbital radii except under highly specific mutual relationships, here
derived analytically apparently for the first time. In particular, the most
stable situation is achieved (in this idealized model) only when each planetary
orbit is roughly twice as far from the Sun as the preceding one, as observed
empirically already by Titius (1766) and Bode (1778) and used in both the
discoveries of Uranus (1781) and the Asteroid Belt (1801). ETC.Comment: 27 page
The subconvexity problem for \GL_{2}
Generalizing and unifying prior results, we solve the subconvexity problem
for the -functions of \GL_{1} and \GL_{2} automorphic representations
over a fixed number field, uniformly in all aspects. A novel feature of the
present method is the softness of our arguments; this is largely due to a
consistent use of canonically normalized period relations, such as those
supplied by the work of Waldspurger and Ichino--Ikeda.Comment: Almost final version to appear in Publ. Math IHES. References
updated
The Cross Section of 3He(3He,2p)4He measured at Solar Energies
We report on the results of the \hethet\ experiment at the underground
accelerator facility LUNA (Gran Sasso). For the first time the lowest
projectile energies utilized for the cross section measurement correspond to
energies below the center of the solar Gamow peak (=22 keV). The
data provide no evidence for the existence of a hypothetical resonance in the
energy range investigated. Although no extrapolation is needed anymore (except
for energies at the low-energy tail of the Gamow peak), the data must be
corrected for the effects of electron screening, clearly observed the first
time for the \hethet\ reaction. The effects are however larger than expected
and not understood, leading presently to the largest uncertainty on the quoted
value for bare nuclides (=5.40 MeV b).Comment: 18 pages, 10 postscript figures, Calculations concerning hypothetical
resonanz added, Submitted to Phys. Rev. C., available at this URL:
HTTP://www.lngs.infn.it/lngs/htexts/luna/luna.htm
Towards an unified description of total and diffractive structure functions at HERA in the QCD dipole picture
It is argued that the QCD dipole picture allows to build an unified
theoretical description -based on BFKL dynamics- of the total and diffractive
nucleon structure functions. This description is in qualitative agreement with
the present collection of data obtained by the H1 collaboration. More precise
theoretical estimates, in particular the determination of the normalizations
and proton transverse momentum behaviour of the diffractive components, are
shown to be required in order to reach definite conclusions.Comment: latex file with 5 encapsulated figures, 19 page
Wettability characteristics of an Al2O3/SiO2-based ceramic modified with CO2, Nd:YAG, excimer and high-power diode lasers
Interaction of CO2, Nd:YAG, excimer and high power diode laser (HPDL) radiation with the
surface of an Al2O3/SiO2 based ceramic was found to effect significant changes in the
wettability characteristics of the material. It was observed that interaction with CO2, Nd:YAG
and HPDL radiation reduced the enamel contact angle from 1180 to 310, 340 and 330
respectively. In contrast, interaction with excimer laser radiation resulted an increase in the
contact angle to 1210. Such changes were identified as being due to: (i) the melting and partial
vitrification of the Al2O3/SiO2 based ceramic surface as a result of interaction with CO2,
Nd:YAG HPDL radiation. (ii) the surface roughness of the Al2O3/SiO2 based ceramic
increasing after interaction with excimer laser radiation. (iii) the surface oxygen content of the
Al2O3/SiO2 based ceramic increasing after interaction with CO2, Nd:YAG and HPDL radiation.
The work has shown that the wettability characteristics of the Al2O3/SiO2 based ceramic could
be controlled and/or modified with laser surface treatment. In particular, whether the laser
radiation had the propensity to cause surface melting. However, a wavelength dependance of
the change of the wetting properties could not be deduced from the findings of this work
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