877 research outputs found
Identification of T. gondii myosin light chain-1 as a direct target of TachypleginA-2, a small-molecule inhibitor of parasite motility and invasion
This work was supported by US Public Health Service grant AI054961 (GEW/NJW), a University Research Fellowship from the Royal Society (NJW) and funding for the mass spectrometry analysis was provided by the Vermont Genetics Network/NIH Grant 8P20GM103449 from the INBRE program of the NIGMS.Motility of the protozoan parasite Toxoplasma gondii plays an important role in the parasite's life cycle and virulence within animal and human hosts. Motility is driven by a myosin motor complex that is highly conserved across the Phylum Apicomplexa. Two key components of this complex are the class XIV unconventional myosin, TgMyoA, and its associated light chain, TgMLC1. We previously showed that treatment of parasites with a small-molecule inhibitor of T. gondii invasion and motility, tachypleginA, induces an electrophoretic mobility shift of TgMLC1 that is associated with decreased myosin motor activity. However, the direct target(s) of tachypleginA and the molecular basis of the compound-induced TgMLC1 modification were unknown. We show here by ''click'' chemistry labelling that TgMLC1 is a direct and covalent target of an alkyne-derivatized analogue of tachypleginA. We also show that this analogue can covalently bind to model thiol substrates. The electrophoretic mobility shift induced by another structural analogue, tachypleginA-2, was associated with the formation of a 225.118 Da adduct on S57 and/or C58, and treatment with deuterated tachypleginA-2 confirmed that the adduct was derived from the compound itself. Recombinant TgMLC1 containing a C58S mutation (but not S57A) was refractory to click labelling and no longer exhibited a mobility shift in response to compound treatment, identifying C58 as the site of compound binding on TgMLC1. Finally, a knock-in parasite line expressing the C58S mutation showed decreased sensitivity to compound treatment in a quantitative 3D motility assay. These data strongly support a model in which tachypleginA and its analogues inhibit the motility of T. gondii by binding directly and covalently to C58 of TgMLC1, thereby causing a decrease in the activity of the parasite's myosin motor. Publisher PDFPeer reviewe
Novel Phases and Finite-Size Scaling in Two-Species Asymmetric Diffusive Processes
We study a stochastic lattice gas of particles undergoing asymmetric
diffusion in two dimensions. Transitions between a low-density uniform phase
and high-density non-uniform phases characterized by localized or extended
structure are found. We develop a mean-field theory which relates
coarse-grained parameters to microscopic ones. Detailed predictions for
finite-size () scaling and density profiles agree excellently with
simulations. Unusual large- behavior of the transition point parallel to
that of self-organized sandpile models is found.Comment: 7 pages, plus 6 figures uuencoded, compressed and appended after
source code, LATeX, to be published as a Phys. Rev. Let
Androgen receptor phosphorylation status at serine 578 predicts poor outcome in prostate cancer patients
Purpose: Prostate cancer growth is dependent upon androgen receptor (AR) activation, regulated via phosphorylation. Protein kinase C (PKC) is one kinase that can mediate AR phosphorylation. This study aimed to establish if AR phosphorylation by PKC is of prognostic significance.
Methods: Immunohistochemistry for AR, AR phosphorylated at Ser-81 (pARS81), AR phosphorylated at Ser-578 (pARS578), PKC and phosphorylated PKC (pPKC) was performed on 90 hormone-naïve prostate cancer specimens. Protein expression was quantified using the weighted histoscore method and examined with regard to clinico-pathological factors and outcome measures; time to biochemical relapse, survival from biochemical relapse and disease-specific survival.
Results: Nuclear PKC expression strongly correlated with nuclear pARS578 (c.c. 0.469, p=0.001) and cytoplasmic pARS578 (c.c. 0.426 p=0.002). High cytoplasmic and nuclear pARS578 were associated with disease-specific survival (p<0.001 and p=0.036 respectively). High nuclear PKC was associated with lower disease-specific survival when combined with high pARS578 in the cytoplasm (p=0.001) and nucleus (p=0.038). Combined high total pARS81 and total pARS578 was associated with decreased disease-specific survival (p=0.005)
Conclusions: pARS578 expression is associated with poor outcome and is a potential independent prognostic marker in hormone-naïve prostate cancer. Furthermore, PKC driven AR phosphorylation may promote prostate cancer progression and provide a novel therapeutic target
Enhanced Bound State Formation in Two Dimensions via Stripe-Like Hopping Anisotropies
We have investigated two-electron bound state formation in a square
two-dimensional t-J-U model with hopping anisotropies for zero electron
density; these anisotropies are introduced to mimic the hopping energies
similar to those expected in stripe-like arrangements of holes and spins found
in various transition metal oxides. In this report we provide analytical
solutions to this problem, and thus demonstrate that bound-state formation
occurs at a critical exchange coupling, J_c, that decreases to zero in the
limit of extreme hopping anisotropy t_y/t_x -> 0. This result should be
contrasted with J_c/t = 2 for either a one-dimensional chain, or a
two-dimensional plane with isotropic hopping. Most importantly, this behaviour
is found to be qualitatively similar to that of two electrons on the two-leg
ladder problem in the limit of t_interchain/t_intrachain -> 0. Using the latter
result as guidance, we have evaluated the pair correlation function, thus
determining that the bound state corresponds to one electron moving along one
chain, with the second electron moving along the opposite chain, similar to two
electrons confined to move along parallel, neighbouring, metallic stripes. We
emphasize that the above results are not restricted to the zero density limit -
we have completed an exact diagonalization study of two holes in a 12 X 2
two-leg ladder described by the t-J model and have found that the
above-mentioned lowering of the binding energy with hopping anisotropy persists
near half filling.Comment: 6 pages, 3 eps figure
LEP1 vs. Future Colliders: Effective Operators And Extended Gauge Group
In an effective Lagrangian approach to physics beyond the Standard Model, it
has been argued that imposing invariance severely restricts
the discovery potential of future colliders. We exhibit a possible way out in
an extended gauge group context.Comment: 14 pages , CERN-TH.6573/92 ULB.TH.04/92 (phyzzx, 3 eps-figs incl.
Spring-block model for a single-lane highway traffic
A simple one-dimensional spring-block chain with asymmetric interactions is
considered to model an idealized single-lane highway traffic. The main elements
of the system are blocks (modeling cars), springs with unidirectional
interactions (modeling distance keeping interactions between neighbors), static
and kinetic friction (modeling inertia of drivers and cars) and spatiotemporal
disorder in the values of these friction forces (modeling differences in the
driving attitudes). The traveling chain of cars correspond to the dragged
spring-block system. Our statistical analysis for the spring-block chain
predicts a non-trivial and rich complex behavior. As a function of the disorder
level in the system a dynamic phase-transition is observed. For low disorder
levels uncorrelated slidings of blocks are revealed while for high disorder
levels correlated avalanches dominates.Comment: 6 pages, 7 figure
Spectral density for a hole in an antiferromagnetic stripe phase
Using variational trial wave function based on the string picture we study
the motion of a single mobile hole in the stripe phase of the doped
antiferromagnet. The holes within the stripes are taken to be static, the
undoped antiferromagnetic domains in between the hole stripes are assumed to
have alternating staggered magnetization, as is suggested by neutron scattering
experiments. The system is described by the t-t'-t''-J model with realistic
parameters and we compute the single particle spectral density.Comment: RevTex-file, 9 PRB pages with 15 .eps and .gif files. To appear in
PRB. Hardcopies of figures (or the entire manuscript) can be obtained by
e-mail request to: [email protected]
An Exact Diagonalization Demonstration of Incommensurability and Rigid Band Filling for N Holes in the t-J Model
We have calculated S(q) and the single particle distribution function
for N holes in the t - J model on a non--square sqrt{8} X sqrt{32} 16--site
lattice with periodic boundary conditions; we justify the use of this lattice
in compariosn to those of having the full square symmetry of the bulk. This new
cluster has a high density of vec k points along the diagonal of reciprocal
space, viz. along k = (k,k). The results clearly demonstrate that when the
single hole problem has a ground state with a system momentum of vec k =
(pi/2,pi/2), the resulting ground state for N holes involves a shift of the
peak of the system's structure factor away from the antiferromagnetic state.
This shift effectively increases continuously with N. When the single hole
problem has a ground state with a momentum that is not equal to k =
(pi/2,pi/2), then the above--mentioned incommensurability for N holes is not
found. The results for the incommensurate ground states can be understood in
terms of rigid--band filling: the effective occupation of the single hole k =
(pi/2,pi/2) states is demonstrated by the evaluation of the single particle
momentum distribution function . Unlike many previous studies, we show
that for the many hole ground state the occupied momentum states are indeed k =
(+/- pi/2,+/- pi/2) states.Comment: Revtex 3.0; 23 pages, 1 table, and 13 figures, all include
Quantum Deconstruction of a 5D SYM and its Moduli Space
We deconstruct the fifth dimension of the 5D SYM theory with SU(M) gauge
symmetry and Chern-Simons level k=M and show how the 5D moduli space follows
from the non-perturbative analysis of the 4D quiver theory. The 5D coupling
h=1/(g_5)^2 of the un-broken SU(M) is allowed to take any non-negative values,
but it cannot be continued to h<0 and there are no transitions to other phases
of the theory. The alternative UV completions of the same 5D SYM -- via M
theory on the C^3/Z_2M orbifold or via the dual five-brane web in type IIB
string theory -- have identical moduli spaces: h >= 0 only, and no flop
transitions. We claim these are intrinsic properties of the SU(M) SYM theory
with k=M.Comment: 46 Page
Wound healing and hyper-hydration - a counter intuitive model
Winters seminal work in the 1960s relating to providing an optimal level of moisture to aid wound healing (granulation and re-epithelialisation) has been the single most effective advance in wound care over many decades. As such the development of advanced wound dressings that manage the fluidic wound environment have provided significant benefits in terms of healing to both patient and clinician. Although moist wound healing provides the guiding management principle confusion may arise between what is deemed to be an adequate level of tissue hydration and the risk of developing maceration. In addition, the counter-intuitive model ‘hyper-hydration’ of tissue appears to frustrate the moist wound healing approach and advocate a course of intervention whereby tissue is hydrated beyond what is a normally acceptable therapeutic level. This paper discusses tissue hydration, the cause and effect of maceration and distinguishes these from hyper-hydration of tissue. The rationale is to provide the clinician with a knowledge base that allows optimisation of treatment and outcomes and explains the reasoning behind wound healing using hyper-hydration
- …