Color coherence in a heavy quark antenna radiating gluons inside a QCD medium

We compute the color coherence effects for soft gluon radiation off antennas containing heavy quarks in the presence of a QCD medium - in color singlet, triplet or octet global states. This work completes the studies of antenna radiation inside a medium which provide a useful picture of the relevance of interference effects in jet parton showers for the jet quenching phenomenon observed in high-energy nuclear collisions. The analysis is performed resumming the multiple scatterings of the partonic system with the medium. The main conclusion is that decorrelation due to color rotation is more effective in the case in which at least one of the emitters of the antenna is a heavy quark. This effect, present both for a heavy-quark-antiquark or a heavy-quark-gluon antenna is more relevant for the later or for the case in which the energies of the quark and antiquark are very different. The parameter controlling these effects involves the dead-cone angle. We find that interferences are cancelled, spoiling the color correlation of the pair, when $\theta_{ DC}=M/E >>1/\sqrt{\omega L}$ where E and {\omega} are the energies of the heavy quark and the radiated gluon and L is the medium length. In the case of a heavy-quark-antiquark antenna $t_{form}$ appears instead of L if the original splitting is symmetric. The presence or absence of interferences modifies the energy loss pattern.Comment: 12 page

ACRATA: a novel electron transfer domain associated to apoptosis and cancer

BACKGROUND: Recently, several members of a vertebrate protein family containing a six trans-membrane (6TM) domain and involved in apoptosis and cancer (e.g. STEAP, STAMP1, TSAP6), have been identified in Golgi and cytoplasmic membranes. The exact function of these proteins remains unknown. METHODS: We related this 6TM domain to distant protein families using intermediate sequences and methods of iterative profile sequence similarity search. RESULTS: Here we show for the first time that this 6TM domain is homolog to the 6TM heme binding domain of both the NADPH oxidase (Nox) family and the YedZ family of bacterial oxidoreductases. CONCLUSIONS: This finding gives novel insights about the existence of a previously undetected electron transfer system involved in apoptosis and cancer, and suggests further steps in the experimental characterization of these evolutionarily related families

Antioxidant metabolism of coffee cell suspension cultures in response to cadmium.

The antioxidant responses of coffee (Coffea arabica L.) cell suspension cultures to cadmium (Cd) were investigated. Cd accumulated very rapidly in the cells and this accumulation was directly correlated with an increase in applied CdCl2 concentration in the external medium. At 0.05 mM CdCl2, growth was stimulated, but at 0.5 mM CdCl2, the growth rate was reduced. An alteration in activated oxygen metabolism was detected by visual analysis as well as by an increase in lipid peroxidation at the higher CdCl2 concentration. Catalase (CAT; EC 1.11.1.6), glutathione reductase (GR; EC 1.6.4.2) and superoxide dismutase (SOD; EC 1.15.1.1) activity increased, particularly at the higher concentration of CdCl2. Ascorbate peroxidase (APX; EC 1.11.1.11) activity was increased at the lower CdCl2 concentration used, but could not be detected in cells growing in the higher CdCl2 concentration after 24 h of growth, whilst guaiacol peroxidase (GOPX; EC 1.11.1.7) did not show a clear response to Cd treatment. An analysis by non-denaturing PAGE followed by staining for enzyme activity, revealed one CAT isoenzyme, nine SOD isoenzymes and four GR isoenzymes. The SOD isoenzymes were differently affected by CdCl2 treatment and one GR isoenzyme was shown to specifically respond to CdCl2. The results suggest that the higher concentrations of CdCl2 may lead to oxidative stress. The main response appears to be via the induction of SOD and CAT activities for the removal of reactive oxygen species (ROS), and by the induction of GR to ensure the availability of reduced glutathione for the synthesis of Cd-binding peptides, which may also be related to the inhibition of APX activity probably due to glutathione and ascorbate depletion

Modulating the DNA cleavage ability of copper(ii) Schiff bases through ternary complex formation

Copper(II) complexes with the potentially tridentate Schiff bases N-[(3-ethoxy-2-hydroxyphenyl)methylidene]-N′-tosylbenzene-1,2-diamine (H2L1) and N-[(2-hydroxynaphthanyl)methylidene]-N′-tosylbenzene-1,2-diamine (H2L2) have been synthesized by electrochemical oxidation of the metal in an electrochemical cell containing a solution of the corresponding ligand in acetonitrile. Adducts of these compounds with 2,2′-bipyridine (2,2′-bpy), 4,4′-bipyridine (4,4′-bpy) or 1,10-phenanthroline (phen) were also obtained. The complexes have been characterized by microanalysis, mass spectrometry, EPR, IR and UV-Vis spectroscopies, as well as DFT calculations. The ligand H2L1 and the compounds [CuL1(H2O)]·H2O (1), [Cu2L12(4,4′-bpy)] (3), [CuL1(phen)] (4), [CuL2(2,2′-bpy)] (6), and [Cu2L22(4,4′-bpy)3] (7) have also been characterized by X-ray diffraction. The copper compounds 1, 4 and 6 are mononuclear with a square planar geometry around the metal for 1 and square pyramidal for 4 and 6. However, 3 and 7 are dinuclear complexes with a 4,4′-bpy ligand bridging two copper atoms with square planar (3) or square pyramidal (7) coordination. The supramolecular structures were studied by means of Hirshfeld surface analysis. The adducts of phen and 2,2′-bpy exhibit enhanced DNA cleavage ability compared to the [CuL(H2O)] complexes (L = L1 or L2), while the binuclear entities formed by 4,4′-bpy coordination present reduced nuclease efficiency

A new family of intrinsically disordered proteins: structural characterization of the major phasin PhaF from Pseudomonas putida KT2440

Contains fulltext : 118281.pdf (publisher's version ) (Open Access)Phasins are intracellular polyhydroxyalkanoat4e (PHA)-associated proteins involved in the stabilization of these bacterial carbon storage granules. Despite its importance in PHA metabolism and regulation, only few reports have focused so far on the structure of these proteins. In this work we have investigated the structure and stability of the PhaF phasin from Pseudomonas putida KT2440, a protein that is involved in PHA granule stabilization and distribution to daughter cells upon cell division. A structural, three-dimensional model of the protein was built from homology modeling procedures and consensus secondary structure predictions. The model predicts that PhaF is an elongated protein, with a long, amphipathic N-terminal helix with PHA binding capacity, followed by a short leucine zipper involved in protein oligomerization and a superhelical C-terminal domain wrapped around the chromosomal DNA. Hydrodynamic, spectroscopical and thermodynamic experiments validated the model and confirmed both that free PhaF is a tetramer in solution and that most part of the protein is intrinsically disordered in the absence of its ligands. The results lay a molecular basis for the explanation of the biological role of PhaF and, along with an exhaustive analysis of phasin sequence databases, suggest that intrinsic disorder and oligomerization through coiled-coils may be a widespread mechanism among these proteins