5,394 research outputs found
The enzymes LSD1 and Set1A cooperate with the viral protein HBx to establish an active hepatitis B viral chromatin state
Indexación: Web of ScienceWith about 350 million people chronically infected around the world hepatitis B is a major health problem. Template for progeny HBV synthesis is the viral genome, organized as a minichromosome (cccDNA) inside the hepatocyte nucleus. How viral cccDNA gene expression is regulated by its chromatin structure; more importantly, how the modulation of this structure impacts on viral gene expression remains elusive. Here, we found that the enzyme SetDB1 contributes to setting up a repressed cccDNA chromatin state. This repressive state is activated by the histone lysine demethylase-1 (LSD1). Consistently, inhibiting or reducing LSD1 levels led to repression of viral gene expression. This correlates with the transcriptionally repressive mark H3K9 methylation and reduction on the activating marks H3 acetylation and H3K4 methylation on viral promoters. Investigating the importance of viral proteins we found that LSD1 recruitment to viral promoters was dependent on the viral transactivator protein HBx. Moreover, the histone methyltransferase Set1A and HBx are simultaneously bound to the core promoter, and Set1A expression correlates with cccDNA H3K4 methylation. Our results shed light on the mechanisms of HBV regulation mediated by the cccDNA chromatin structure, offering new therapeutic targets to develop drugs for the treatment of chronically infected HBV patients.http://www.nature.com/articles/srep2590
Oxygen insertion into metal carbon bonds: formation of methylperoxo Pd(II) and Pt(II) complexes via photogenerated dinuclear intermediates
Platinum(II) and palladium(II) complexes [M(CH₃)(L)]SbF₆ with substituted terpyridine ligands L undergo light-driven oxygen insertion reactions into metal methyl bonds resulting in methylperoxo complexes [M(OOCH₃)(L)]SbF₆. The oxygen insertion reactions occur readily for complexes with methyl ligands that are activated due to steric interaction with substituents (NH₂, NHMe or CH₃) at the 6,6″-positions on the terpyridine ligand. All complexes exhibit attractive intermolecular π···π or M···M interactions in the solid state and in solution, which lead to excited triplet dinuclear M–M complexes upon irradiation. A mechanism is proposed whereby a dinuclear intermediate is generated upon irradiation that has a weakened M–C bond in the excited state, resulting in the observed oxygen insertion reactions
On holographic three point functions for GKP strings from integrability
Adapting the powerful integrability-based formalism invented previously for
the calculation of gluon scattering amplitudes at strong coupling, we develop a
method for computing the holographic three point functions for the large spin
limit of Gubser-Klebanov- Polyakov (GKP) strings. Although many of the ideas
from the gluon scattering problem can be transplanted with minor modifications,
the fact that the information of the external states is now encoded in the
singularities at the vertex insertion points necessitates several new
techniques. Notably, we develop a new generalized Riemann bilinear identity,
which allows one to express the area integral in terms of appropriate contour
integrals in the presence of such singularities. We also give some general
discussions on how semiclassical vertex operators for heavy string states
should be constructed systematically from the solutions of the Hamilton-Jacobi
equation.Comment: 62 pages;v2 Typos and equation (3.7) corrected. Clarifying remarks
added in Section 4.1. Published version;v3 Minor errors found in version 2
are corrected. For explanation of the revision, see Erratum published in
http://www.springerlink.com/content/m67055235407vx67/?MUD=M
Wave functions and correlation functions for GKP strings from integrability
We develop a general method of computing the contribution of the vertex
operators to the semi-classical correlation functions of heavy string states,
based on the state-operator correspondence and the integrable structure of the
system. Our method requires only the knowledge of the local behavior of the
saddle point configuration around each vertex insertion point and can be
applied to cases where the precise forms of the vertex operators are not known.
As an important application, we compute the contributions of the vertex
operators to the three-point functions of the large spin limit of the
Gubser-Klebanov-Polyakov (GKP) strings in spacetime, left unevaluated
in our previous work [arXiv:1110.3949] which initiated such a study. Combining
with the finite part of the action already computed previously and with the
newly evaluated divergent part of the action, we obtain finite three-point
functions with the expected dependence of the target space boundary coordinates
on the dilatation charge and the spin.Comment: 80 pages, 7 figures, v2: typos and minor errors corrected, a
reference added, v3: typos and a reference corrected, published versio
Holographic three-point functions for short operators
We consider holographic three-point functions for operators dual to short
string states at strong coupling in N=4 super Yang-Mills. We treat the states
as point-like as they come in from the boundary but as strings in the
interaction region in the bulk. The interaction position is determined by
saddle point, which is equivalent to conservation of the canonical momentum for
the interacting particles, and leads to conservation of their conformal
charges. We further show that for large dimensions the rms size of the
interaction region is small compared to the radius of curvature of the AdS
space, but still large compared to the string Compton wave-length. Hence, one
can approximate the string vertex operators as flat-space vertex operators with
a definite momentum, which depends on the conformal and R-charges of the
operator. We then argue that the string vertex operator dual to a primary
operator is chosen by satisfying a twisted version of Q^L=Q^R, up to spurious
terms. This leads to a unique choice for a scalar vertex operator with the
appropriate charges at the first massive level. We then comment on some
features of the corresponding three-point functions, including the application
of these results to Konishi operators.Comment: 24 pages; v2: References added, typos fixed, minor change
More three-point correlators of giant magnons with finite size
In the framework of the semiclassical approach, we compute the normalized
structure constants in three-point correlation functions, when two of the
vertex operators correspond to heavy string states, while the third vertex
corresponds to a light state. This is done for the case when the heavy string
states are finite-size giant magnons with one or two angular momenta, and for
two different choices of the light state, corresponding to dilaton operator and
primary scalar operator. The relevant operators in the dual gauge theory are
Tr(F_{\mu\nu}^2 Z^j+...) and Tr(Z^j). We first consider the case of AdS_5 x S^5
and N = 4 super Yang-Mills. Then we extend the obtained results to the
gamma-deformed AdS_5 x S^5_\gamma, dual to N = 1 super Yang-Mills theory,
arising as an exactly marginal deformation of N = 4 super Yang-Mills.Comment: 14 pages, no figure
Tailoring Three-Point Functions and Integrability III. Classical Tunneling
We compute three-point functions between one large classical operator and two
large BPS operators at weak coupling. We consider operators made out of the
scalars of N=4 SYM, dual to strings moving in the sphere. The three-point
function exponentiates and can be thought of as a classical tunneling process
in which the classical string-like operator decays into two classical BPS
states. From an Integrability/Condensed Matter point of view, we simplified
inner products of spin chain Bethe states in a classical limit corresponding to
long wavelength excitations above the ferromagnetic vacuum. As a by-product we
solved a new long-range Ising model in the thermodynamic limit.Comment: 37 pages, 10 figure
Correlation functions of three heavy operators - the AdS contribution
We consider operators in N=4 SYM theory which are dual, at strong coupling,
to classical strings rotating in S^5. Three point correlation functions of such
operators factorize into a universal contribution coming from the AdS part of
the string sigma model and a state-dependent S^5 contribution. Consequently a
similar factorization arises for the OPE coefficients. In this paper we
evaluate the AdS universal factor of the OPE coefficients which is explicitly
expressed just in terms of the anomalous dimensions of the three operators.Comment: 49 pages, 3 figures; v.2 references corrected; v3: corrected
discussion in section 5, results unchange
Holographic 3-point function at one loop
We explore the recent weak/strong coupling match of three-point functions in
the AdS/CFT correspondence for two semi-classical operators and one light
chiral primary operator found by Escobedo et al. This match is between the
tree-level three-point function with the two semi-classical operators described
by coherent states while on the string side the three-point function is found
in the Frolov-Tseytlin limit. We compute the one-loop correction to the
three-point function on the gauge theory side and compare this to the
corresponding correction on the string theory side. We find that the
corrections do not match. Finally, we discuss the possibility of further
contributions on the gauge theory side that can alter our results.Comment: 24 pages, 2 figures. v2: Typos fixed, Ref. added, figure improved.
v3: Several typos and misprints fixed, Ref. updated, figures improved, new
section 2.3 added on correction from spin-flipped coherent state,
computations on string theory side improve
Ecology of Sleeping: The Microbial and Arthropod Associates of Chimpanzee Beds
The indoor environment created by the construction of homes and other buildings is often considered to be uniquely different from other environments. It is composed of organisms that are less diverse than those of the outdoors and strongly sourced by, or dependent upon, human bodies. Yet, no one has ever compared the composition of species found in contemporary human homes to that of other structures built by mammals, including those of non-human primates. Here we consider the microbes and arthropods found in chimpanzee beds, relative to the surrounding environment (n = 41 and 15 beds, respectively). Based on the study of human homes, we hypothesized that the microbes found in chimpanzee beds would be less diverse than those on nearby branches and leaves and that their beds would be primarily composed of body-associated organisms. However, we found that differences between wet and dry seasons and elevation above sea level explained nearly all of the observed variation in microbial diversity and community structure. While we can identify the presence of a chimpanzee based on the assemblage of bacteria, the dominant signal is that of environmental microbes. We found just four ectoparasitic arthropod specimens, none of which appears to be specialized on chimpanzees or their structures. These results suggest that the life to which chimpanzees are exposed while in their beds is predominately the same as that of the surrounding environment
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