On the "Fake" Inferred Entanglement Associated with the Maximum Entropy Inference of Quantum States

The inference of entangled quantum states by recourse to the maximum entropy principle is considered in connection with the recently pointed out problem of fake inferred entanglement [R. Horodecki, {\it et al.}, Phys. Rev. A {\it 59} (1999) 1799]. We show that there are operators $\hat A$, both diagonal and non diagonal in the Bell basis, such that when the expectation value $$ is taken as prior information the problem of fake entanglement is not solved by adding a new constraint associated with the mean value of $\hat A^2$ (unlike what happens when the partial information is given by the expectation value of a Bell operator). The fake entanglement generated by the maximum entropy principle is also studied quantitatively by comparing the entanglement of formation of the inferred state with that of the original one.Comment: 25 Revtex pages, 5 Postscript figures, submitted to J. Phys. A (Math. Gen.

Quantum cobwebs: Universal entangling of quantum states

Entangling an unknown qubit with one type of reference state is generally impossible. However, entangling an unknown qubit with two types of reference states is possible. To achieve this, we introduce a new class of states called zero sum amplitude (ZSA) multipartite, pure entangled states for qubits and study their salient features. Using shared-ZSA state, local operation and classical communication we give a protocol for creating multipartite entangled states of an unknown quantum state with two types of reference states at remote places. This provides a way of encoding an unknown pure qubit state into a multiqubit entangled state. We quantify the amount of classical and quantum resources required to create universal entangled states. This is possibly a strongest form of quantum bit hiding with multiparties.Comment: Invited talk in II Winter Institute on FQTQO: Quantum Information Processing, held at S. N. Bose Center for Basic Science, Kolkata, during Jan 2-11, 2002. (To appear in Pramana-J. of Physics, 2002.

Controlled assembly of SNAP-PNA-fluorophore systems on DNA templates to produce fluorescence resonance energy transfer

The SNAP protein is a widely used self-labeling tag that can be used for tracking protein localization and trafficking in living systems. A model system providing controlled alignment of SNAP-tag units can provide a new way to study clustering of fusion proteins. In this work, fluorescent SNAP-PNA conjugates were controllably assembled on DNA frameworks forming dimers, trimers, and tetramers. Modification of peptide nucleic acid (PNA) with the O6-benzyl guanine (BG) group allowed the generation of site-selective covalent links between PNA and the SNAP protein. The modified BG-PNAs were labeled with fluorescent Atto dyes and subsequently chemo-selectively conjugated to SNAP protein. Efficient assembly into dimer and oligomer forms was verified via size exclusion chromatography (SEC), electrophoresis (SDS-PAGE), and fluorescence spectroscopy. DNA directed assembly of homo- and hetero-dimers of SNAP-PNA constructs induced homo- and hetero-FRET, respectively. Longer DNA scaffolds controllably aligned similar fluorescent SNAP-PNA constructs into higher oligomers exhibiting homo-FRET. The combined SEC and homo-FRET studies indicated the 1:1 and saturated assemblies of SNAP-PNA-fluorophore:DNA formed preferentially in this system. This suggested a kinetic/stoichiometric model of assembly rather than binomially distributed products. These BG-PNA-fluorophore building blocks allow facile introduction of fluorophores and/or assembly directing moieties onto any protein containing SNAP. Template directed assembly of PNA modified SNAP proteins may be used to investigate clustering behavior both with and without fluorescent labels which may find use in the study of assembly processes in cells

The African swine fever virus dynein-binding protein p54 induces infected cell apoptosis

AbstractA specific interaction of ASFV p54 protein with 8 kDa light chain cytoplasmic dynein (DLC8) has been previously characterized and this interaction is critical during virus internalization and transport to factory sites. During early phases of infection, the virus induces the initiation of apoptosis triggering activation of caspase-9 and -3. To analyze the role of the structural protein p54 in apoptosis, transient expression experiments of p54 in Vero cells were carried out which resulted in effector caspase-3 activation and apoptosis. Interestingly, p54 mutants, lacking the 13 aa dynein-binding motif lose caspase activation ability and pro-death function of p54. This is the first reported ASFV protein which induces apoptosis

Improving the Performance of K-Means for Color Quantization

Color quantization is an important operation with many applications in graphics and image processing. Most quantization methods are essentially based on data clustering algorithms. However, despite its popularity as a general purpose clustering algorithm, k-means has not received much respect in the color quantization literature because of its high computational requirements and sensitivity to initialization. In this paper, we investigate the performance of k-means as a color quantizer. We implement fast and exact variants of k-means with several initialization schemes and then compare the resulting quantizers to some of the most popular quantizers in the literature. Experiments on a diverse set of images demonstrate that an efficient implementation of k-means with an appropriate initialization strategy can in fact serve as a very effective color quantizer.Comment: 26 pages, 4 figures, 13 table

Novel in vitro and in vivo data on the cellular localization of Hsp10 in smokers affected by COPD and in lung-derived cell lines exposed to cigarette smoke extract as stressor

Cigarette smoke is a potent stressor for the respiratory system, contributing to pathogenesis, for instance in chronic obstructive pulmonary disease (COPD), but its effects on the expression, function, and cellular localization of mitochondrial chaperonins are still largely unknown. We studied in vivo (airways biopsies) the localization of Hsp10 and Hsp60 in patients (smokers and non-smokers) affected by mild-moderate COPD, and characterized the effects of non-lethal doses of cigarette smoke extract (CSE) on the expression of these molecules in two human cell lines: lung fibroblasts (HFL-1) and bronchial epithelial (16HBE). We applied various in vitro methods: immunohistochemistry (IHC), subcellular fractionation analyses (SFA), Western blotting (WB), immunocytochemistry (ICC), and transmission electron microscopy (TEM) immunogold, and used bioinformatics and databases searches to gather structural in silico data for interpreting and complementing the in vitro results. IHC showed that in smokers and non-smokers COPD patients Hsp10 was localized in both, the cytoplasm and the nucleus of epithelial and lamina propria cells, while Hsp60 was present only in the cytosol. ICC, SFA, and WB on both CSE-exposed cell lines confirmed the presence of nuclear Hsp10, with an increasing trend in parallel to CSE concentration. TEM immunogold further confirmed Hsp10 in the nucleus, in addition to its presence in the cytoplasm and mitochondria, on both cell lines. Bioinformatics and in silico structural analyses indicated that Hsp10 can localize in extramitochondrial sites, such as the nucleus, even if Hsp10 lacks known DNA-binding motifs or nuclear import signals in its primary sequence. Our data suggest a link between exposure to exogenous oxidative stress and cell response, involving Hsp10, which would play roles different from its canonical functions. It is known that Hsp10 can display an array of functions depending on its location: cytoplasm, mitochondria, or extracellular. Here, we show for the first time the presence of Hsp10 in the nucleus of epithelial and stromal human-lung cell lines, paralleling the observations in vivo in COPD patients, and indicating that intranuclear Hsp10 levels are affected by oxidative stress due to an exogenous stressor like cigarette-smoke. The questions now are by what mechanism Hsp10 becomes a resident of the nucleus and what are its functions there.

Towards a classification strategy for complex nanostructures

The range of possible nanostructures is so large and continuously growing, that collating and unifying the knowledge connected to them, including their biological activity, is a major challenge. Here we discuss a conception that is based on connection of microscopic features of the nanomaterials to their biological impacts. We also consider what would be necessary to identify the features that control their biological interactions, and make them resemble each other in a biological context

Redox Signaling by the RNA Polymerase III TFIIB-Related Factor Brf2.

TFIIB-related factor 2 (Brf2) is a member of the family of TFIIB-like core transcription factors. Brf2 recruits RNA polymerase (Pol) III to type III gene-external promoters, including the U6 spliceosomal RNA and selenocysteine tRNA genes. Found only in vertebrates, Brf2 has been linked to tumorigenesis but the underlying mechanisms remain elusive. We have solved crystal structures of a human Brf2-TBP complex bound to natural promoters, obtaining a detailed view of the molecular interactions occurring at Brf2-dependent Pol III promoters and highlighting the general structural and functional conservation of human Pol II and Pol III pre-initiation complexes. Surprisingly, our structural and functional studies unravel a Brf2 redox-sensing module capable of specifically regulating Pol III transcriptional output in living cells. Furthermore, we establish Brf2 as a central redox-sensing transcription factor involved in the oxidative stress pathway and provide a mechanistic model for Brf2 genetic activation in lung and breast cancer

Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV

We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at 2.76 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in the central pseudorapidity region (|$\eta$|<0.8) and transverse momentum range 0.2< $p_{\rm T}$< 5.0 GeV/$c$. The elliptic flow signal v$_2$, measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is 0.087 $\pm$ 0.002 (stat) $\pm$ 0.004 (syst) in the 40-50% centrality class. The differential elliptic flow v$_2(p_{\rm T})$ reaches a maximum of 0.2 near $p_{\rm T}$ = 3 GeV/$c$. Compared to RHIC Au-Au collisions at 200 GeV, the elliptic flow increases by about 30%. Some hydrodynamic model predictions which include viscous corrections are in agreement with the observed increase.Comment: 10 pages, 4 captioned figures, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/389