Cleavage of the apoptosis inhibitor DIAP1 by the apical caspase DRONC in both normal and apoptotic drosophila cells

In Drosophila S2 cells, the apical caspase DRONC undergoes a low level of spontaneous autoprocessing. Unintended apoptosis is prevented by the inhibitor of apoptosis DIAP1, which targets the processed form of DRONC for degradation through its E3 ubiquitin protein ligase activity. Recent reports have demonstrated that shortly after the initiation of apoptosis in S2 cells, DIAP1 is cleaved following aspartate residue Asp-20 by the effector caspase DrICE. Here we report a novel caspase-mediated cleavage of DIAP1 in S2 cells. In both living and dying S2 cells, DIAP1 is cleaved by DRONC after glutamate residue Glu-205, located between the first and second BIR domains. The mutation of Glu-205 prevented the interaction of DIAP1 and processed DRONC but had no effect on the interaction with full-length DRONC. The mutation of Glu-205 also had a negative effect on the ability of overexpressed DIAP1 to prevent apoptosis stimulated by the proapoptotic protein Reaper or by UV light. These results expand our knowledge of the events that occur in the Drosophila apoptosome prior to and after receiving an apoptotic signal

Synchronization in interacting Scale Free Networks

We study the fluctuations of the interface, in the steady state, of the Surface Relaxation Model (SRM) in two scale free interacting networks where a fraction $q$ of nodes in both networks interact one to one through external connections. We find that as $q$ increases the fluctuations on both networks decrease and thus the synchronization reaches an improvement of nearly $40\%$ when $q=1$. The decrease of the fluctuations on both networks is due mainly to the diffusion through external connections which allows to reducing the load in nodes by sending their excess mostly to low-degree nodes, which we report have the lowest heights. This effect enhances the matching of the heights of low-and high-degree nodes as $q$ increases reducing the fluctuations. This effect is almost independent of the degree distribution of the networks which means that the interconnection governs the behavior of the process over its topology.Comment: 13 pages, 7 figures. Added a relevant reference.Typos fixe

Recovery of Interdependent Networks

Recent network research has focused on the cascading failures in a system of interdependent networks and the necessary preconditions for system collapse. An important question that has not been addressed is how to repair a failing system before it suffers total breakdown. Here we introduce a recovery strategy of nodes and develop an analytic and numerical framework for studying the concurrent failure and recovery of a system of interdependent networks based on an efficient and practically reasonable strategy. Our strategy consists of repairing a fraction of failed nodes, with probability of recovery $\gamma$, that are neighbors of the largest connected component of each constituent network. We find that, for a given initial failure of a fraction $1-p$ of nodes, there is a critical probability of recovery above which the cascade is halted and the system fully restores to its initial state and below which the system abruptly collapses. As a consequence we find in the plane $\gamma-p$ of the phase diagram three distinct phases. A phase in which the system never collapses without being restored, another phase in which the recovery strategy avoids the breakdown, and a phase in which even the repairing process cannot avoid the system collapse

Anisotropic Electronic Structure of the Kondo Semiconductor CeFe2Al10 Studied by Optical Conductivity

We report temperature-dependent polarized optical conductivity [$\sigma(\omega)$] spectra of CeFe$_2$Al$_{10}$, which is a reference material for CeRu$_2$Al$_{10}$ and CeOs$_2$Al$_{10}$ with an anomalous magnetic transition at 28 K. The $\sigma(\omega)$ spectrum along the b-axis differs greatly from that in the $ac$-plane, indicating that this material has an anisotropic electronic structure. At low temperatures, in all axes, a shoulder structure due to the optical transition across the hybridization gap between the conduction band and the localized $4f$ states, namely $c$-$f$ hybridization, appears at 55 meV. However, the gap opening temperature and the temperature of appearance of the quasiparticle Drude weight are strongly anisotropic indicating the anisotropic Kondo temperature. The strong anisotropic nature in both electronic structure and Kondo temperature is considered to be relevant the anomalous magnetic phase transition in CeRu$_2$Al$_{10}$ and CeOs$_2$Al$_{10}$.Comment: 5 pages, 4 figure

In vitro genome editing for testing potential gRNAs in CRISPR/Cas9 strategy

Motivation: CRISPR/Cas9 is a promising strategy that improves the efficacy of homology recombination, opening a wide number of possibilites for genome editing. The use of this technology on the reparation of single nucleotide mutations is being under investigation to recover the phenotype of a number of diseases, as the Crigler-Najjar syndrome. Methods: The genomic target sequence of the Ugt1a1 mouse gene was cloned into vectors that were designed to assess efficiency in the generation of double strand brakes (DSB) by engineered nucleases. We have designed different sgRNAs targeting this genomic region. The vectors were transfected into Hek293 together with a plasmid expressing the Cas9 nucelase and the sgRNA, generating a DSB in the target sequence. After recombination, the inactive luciferase gene recovers activity, which is proportional to the cutting efficiency of the nuclease. Then, luciferase and T7 assays were used to determine the activity of gRNAs to target the specific genome locus. Results: Depending on the DNA sequence where is located the gRNA and, specially, the PAM sequences, we have obtained different results on the activity of our gRNAs. However, different factors, as the type of cells transfected or the vectors used, can affect the final activity of the gRNAs and thus, the whole CRISPR/Cas9 activity.Conclusions: With this project, it has been demonstrated the importance of a good design and optimization of the protocols to choose the most efficient gRNAs for CRISPR/Cas9 machinery, as well as in the vectors used to synthetize all the components needed

Secondary homotopy groups

Secondary homotopy groups supplement the structure of classical homotopy groups. They yield a track functor on the track category of pointed spaces compatible with fiber sequences, suspensions and loop spaces. They also yield algebraic models of homotopy types with homotopy groups concentrated in two consecutive dimensions.Comment: We added further commets and references to make the paper more easily readabl

Electronic-Structure-Driven Magnetic Ordering in a Kondo Semiconductor CeOs2Al10

We report the anisotropic changes in the electronic structure of a Kondo semiconductor CeOs$_2$Al$_{10}$ across an anomalous antiferromagnetic ordering temperature ($T_0$) of 29 K, using optical conductivity spectra. The spectra along the $a$- and $c$-axes indicate that a $c$-$f$ hybridization gap emerges from a higher temperature continuously across $T_0$. Along the b-axis, on the other hand, a different energy gap with a peak at 20 meV appears below 39 K, which is higher temperature than $T_0$, because of structural distortion. The onset of the energy gap becomes visible below $T_0$. Our observation reveals that the electronic structure as well as the energy gap opening along the b-axis due to the structural distortion induces antiferromagnetic ordering below $T_0$.Comment: 4 pages, 4 figure

EFFECT OF TWO WHEAT CULTIVARS DIFFERING IN HYDROXAMIC ACID CONCENTRATION ON DETOXIFICATION METABOLISM IN THE APHID Sitobion avenae

Abstract—Hydroxamic acids (Hx) are wheat secondary metabolites conferring resistance for cereals against aphids. The activity of five enzymatic systems were evaluated in the aphid Sitobion avenae reared on the high-Hx wheat cultivar Chagual and the low-Hx wheat cultivar Huayún for 10 generations. Enzyme solutions were prepared from aphid homogenates and assayed for mixed function oxidases (including cytochrome P-450 monooxygenases and NADPH cytochrome c reductase), glutathione S-transferases, esterases, and catalase. Specific activities per aphid individual of cytochrome P-450 monooxygenases, NADPH cytochrome c reductase, glutathione S-transferases, and esterases were significantly increased in wheat cultivars relative to oat (only marginal increase of esterases in Chagual). Aphids fed on cv. Huayún showed an overall higher induction of enzymatic systems than those fed on cv. Chagual. Comparison of these results with reported effects of Hx on detoxifying enzymes in other insects, including aphids, support the hypothesis that these enzymatic pathways play an important role in the detoxification of toxic host-plant secondary metabolites. Key Words—Sitobion avenae, aphids, hydroxamic acids, DIMBOA, detoxification, cytochrome P-450 monooxygenases, NADPH cytochrome c reductase

Evolution of magnetism in Yb(Rh_(1-x)Co_x)2Si2

We present a study of the evolution of magnetism from the quantum critical system YbRh2Si2 to the stable trivalent Yb system YbCo2Si2. Single crystals of Yb(Rh_(1-x)Co_x)2Si2 were grown for 0 < x < 1 and studied by means of magnetic susceptibility, electrical resistivity, and specific heat measurements, as well as photoemission spectroscopy. The results evidence a complex magnetic phase diagram, with a non-monotonic evolution of T_N and two successive transitions for some compositions resulting in two tricritical points. The strong similarity with the phase diagram of YbRh2Si2 under pressure indicates that Co substitution basically corresponds to the application of positive chemical pressure. Analysis of the data proves a strong reduction of the Kondo temperature T_K with increasing Co content, T_K becoming smaller than T_N for x ~ 0.5, implying a strong localization of the 4f electrons. Furthermore, low-temperature susceptibility data confirm a competition between ferromagnetic and antiferromagnetic exchange. The series Yb(Rh_(1-x)Co_x)2Si2 provides an excellent experimental opportunity to gain a deeper understanding of the magnetism at the quantum critical point in the vicinity of YbRh2Si2 where the antiferromagnetic phase disappears (T_N=>0).Comment: 11 pages, 9 figure