The Elimination of the Yeast [PSI+] Prion by Guanidine Hydrochloride is the result of Hsp104 Inactivation

In the yeast Saccharomyces cerevisiae, Sup35p (eRF3), a subunit of the translation termination complex, can take up a prion-like, self-propagating conformation giving rise to the non-Mendelian [PSI+] determinant. The replication of [PSI+] prion seeds can be readily blocked by growth in the presence of low concentrations of guanidine hydrochloride (GdnHCl), leading to the generation of prion-free [psi-] cells. Here, we provide evidence that GdnHCl blocks seed replication in vivo by inactivation of the molecular chaperone Hsp104. Although growth in the presence of GdnHCl causes a modest increase in HSP104 expression (20-90%), this is not sufficient to explain prion curing. Rather, we show that GdnHCl inhibits two different Hsp104-dependent cellular processes, namely the acquisition of thermotolerance and the refolding of thermally denatured luciferase. The inhibitory effects of GdnHCl protein refolding are partially suppressed by elevating the endogenous cellular levels of Hsp104 using a constitutive promoter. The kinetics of GdnHCl-induced [PSI+] curing could be mimicked by co-expression of an ATPase-negative dominant HSP104 mutant in an otherwise wild-type [PSI+] strain. We suggest that GdnHCl inactivates the ATPase activity of Hsp104, leading to a block in the replication of [PSI+] seeds

Asymptotic Error Rates in Quantum Hypothesis Testing

We consider the problem of discriminating between two different states of a finite quantum system in the setting of large numbers of copies, and find a closed form expression for the asymptotic exponential rate at which the specified error probability tends to zero. This leads to the identification of the quantum generalisation of the classical Chernoff distance. The proof relies on two new techniques that have been introduced in [quant-ph/0610027] and [quant-ph/0607216], respectively, and that are also well suited to prove the quantum generalisation of the Hoeffding bound, which is a modification of the Chernoff distance and specifies the optimal achievable asymptotic error rate in the context of asymmetric hypothesis testing. This has been done subsequently by Hayashi [quant-ph/0611013] and Nagaoka [quant-ph/0611289] for the special case where both hypotheses have full support. Moreover, quantum Stein's Lemma and quantum Sanov's theorem may be derived directly from the quantum Hoeffding bound combining it with a result obtained recently in [math/0703772]. The goal of this paper is to present the proofs of the above mentioned results in a unified way and in full generality (allowing hypothetic states with different supports). Additionally, we give an in-depth treatment of the properties of the quantum Chernoff distance. We argue that, although it is not a metric, it is a natural distance measure on the set of density operators, due to its clear operational meaning

Radial Glia in Echinoderms

Radial glial cells are crucial in vertebrate neural development and regeneration. It has been recently proposed that this neurogenic cell type might be older than the chordate lineage itself and might have been present in the last common deuterostome ancestor. Here, we summarize the results of recent studies on radial glia in echinoderms, a highly regenerative phylum of marine invertebrates with shared ancestry to chordates. We discuss the involvement of these cells in both homeostatic neurogenesis and post-traumatic neural regeneration, compare the features of radial glia in echinoderms and chordates to each other, and review the molecular mechanisms that control differentiation and plasticity of the echinoderm radial glia. Overall, studies on echinoderm radial glia provide a unique opportunity to understand the fundamental biology of this cell type from evolutionary and comparative perspectives

Waveform Modelling for the Laser Interferometer Space Antenna

International audienceLISA, the Laser Interferometer Space Antenna, will usher in a new era in gravitational-wave astronomy. As the first anticipated space-based gravitational-wave detector, it will expand our view to the millihertz gravitational-wave sky, where a spectacular variety of interesting new sources abound: from millions of ultra-compact binaries in our Galaxy, to mergers of massive black holes at cosmological distances; from the beginnings of inspirals that will venture into the ground-based detectors' view to the death spiral of compact objects into massive black holes, and many sources in between. Central to realising LISA's discovery potential are waveform models, the theoretical and phenomenological predictions of the pattern of gravitational waves that these sources emit. This white paper is presented on behalf of the Waveform Working Group for the LISA Consortium. It provides a review of the current state of waveform models for LISA sources, and describes the significant challenges that must yet be overcome