Real-time risk analysis for hybrid earthquake early warning systems

Earthquake Early Warning Systems (EEWS), based on real-time prediction of ground motion or structural response measures, may play a role in reducing vulnerability and/or exposition of buildings and lifelines. In fact, recently seismologists developed efficient methods for rapid estimation of event features by means of limited information of the P-waves. Then, when an event is occurring, probabilistic distributions of magnitude and source-to-site distance are available and the prediction of the ground motion at the site, conditioned to the seismic network measures, may be performed in analogy with the Probabilistic Seismic Hazard Analysis (PSHA). Consequently the structural performance may be obtained by the Probabilistic Seismic Demand Analysis (PSDA), and used for real-time risk management purposes. However, such prediction is performed in very uncertain conditions which have to be taken into proper account to limit false and missed alarms. In the present study, real-time risk analysis for early warning purposes is discussed. The magnitude estimation is performed via the Bayesian approach, while the earthquake localization is based on the Voronoi cells. To test the procedure it was applied, by simulation, to the EEWS under development in the Campanian region (southern Italy). The results lead to the conclusion that the PSHA, conditioned to the EEWS, correctly predicts the hazard at the site and that the false/missed alarm probabilities may be controlled by set up of an appropriate decisional rule and alarm threshold

Effects of linker sequence modifications on the structure, stability, and biological activity of a cyclic α-conotoxin

The cyclic conotoxin analogue cVc1.1 is a promising lead molecule for the development of new treatments for neuropathic and chronic pain. The design of this peptide includes a linker sequence that joins the N and C termini together, improving peptide stability while maintaining the structure and activity of the original linear Vc1.1. The effect of linker length on the structure, activity and stability of cyclised conotoxins has been studied previously but the effect of altering the composition of the linker sequence has not been investigated. In this study, we designed three analogues of cVc1.1 with linker sequences that varied in charge, hydrophobicity and hydrogen bonding capacity and examined the effect on structure, stability, membrane permeability and biological activity. The three designed peptides were successfully synthesized using solid phase peptide synthesis approaches and had similar structures and stability compared with cVc1.1. Despite modifications in charge, hydrophobicity and hydrogen bonding potential, which are all factors that can affect membrane permeability, no changes in the ability of the peptides to pass through membranes in either PAMPA or Caco-2 cell assay were observed. Surprisingly, modification of the linker sequence was deleterious to biological activity. These results suggest the linker sequence might be a useful part of the molecule for optimization of bioactivity and not just the physiochemical properties of cVc1.1

Engineering of conotoxins for the treatment of pain

The peptides present in the venoms of marine snails are used by the snails to capture prey, but they have also attracted the interest of drug designers because of their potent activity against therapeutically important targets. These peptides are typically disulfiderich and target a wide range of ion channels, transporters and receptors with exquisite selectivity. In this article, we discuss structural and biological studies on several classes of conotoxins that have potential as drug leads for the treatment of pain. The chemical re-engineering of conotoxins via cyclization has been particularly valuable in improving their biopharmaceutical properties. An excellent example is the α-conotoxin Vc1.1, for which several cyclized analogs have been made. One of them was shown to be orally active in a rat pain model and this analog is currently undergoing pre-clinical development for the treatment of neuropathic pain. Several other α-conotoxins, including ImI, AuIB and MII, have proved amenable to cyclization and in all cases improvements in stability are obtained upon cyclization, suggesting that cyclization is a generally applicable approach to conotoxin stabilization. A variety of other chemical re-engineering approaches have also been used. Minor re-engineering of -conotoxin MrIa to convert its N-terminal residue to pyroglutamic acid proved particularly successful and the modified derivative, Xen2174, is currently in clinical trials for neuropathic pain

Structure-Activity Studies Reveal the Molecular Basis for GABA(B)-Receptor Mediated Inhibition of High Voltage-Activated Calcium Channels by α-Conotoxin Vc1.1

α-Conotoxins are disulfide-bonded peptides from cone snail venoms and are characterized by their affinity for nicotinic acetylcholine receptors (nAChR). Several α-conotoxins with distinct selectivity for nAChR subtypes have been identified as potent analgesics in animal models of chronic pain. However, a number of α-conotoxins have been shown to inhibit N-type calcium channel currents in rodent dissociated dorsal root ganglion (DRG) neurons via activation of G protein-coupled GABAB receptors (GABABR). Therefore, it is unclear whether activation of GABABR or inhibition of α9α10 nAChRs is the analgesic mechanism. To investigate the mechanisms by which α-conotoxins provide analgesia, we synthesized a suite of Vc1.1 analogues where all residues, except the conserved cysteines, in Vc1.1 were individually replaced by alanine (A), lysine (K), and aspartic acid (D). Our results show that the amino acids in the first loop play an important role in binding of the peptide to the receptor, whereas those in the second loop play an important role for the selectivity of the peptide for the GABABR over α9α10 nAChRs. We designed a cVc1.1 analogue that is \u3e8000-fold selective for GABABR-mediated inhibition of high voltage-activated (HVA) calcium channels over α9α10 nAChRs and show that it is analgesic in a mouse model of chronic visceral hypersensitivity (CVH). cVc1.1[D11A,E14A] caused dose-dependent inhibition of colonic nociceptors with greater efficacy in ex vivo CVH colonic nociceptors relative to healthy colonic nociceptors. These findings suggest that selectively targeting GABABR-mediated HVA calcium channel inhibition by α-conotoxins could be effective for the treatment of chronic visceral pain

Structure-activity studies of cysteine-rich α-Conotoxins that inhibit high voltage-activated calcium channels via GABA\u3csub\u3eB\u3c/sub\u3e receptor activation reveal a minimal functional motif

α-Conotoxins are disulfide-rich peptides that target nicotinic acetylcholine receptors. Recently we identified several α-conotoxins that also modulate voltage-gated calcium channels by acting as G protein-coupled GABAB receptor (GABABR) agonists. These α-conotoxins are promising drug leads for the treatment of chronic pain. To elucidate the diversity of α-conotoxins that act through this mechanism, we synthesized and characterized a set of peptides with homology to α-conotoxins known to inhibit high voltage-activated calcium channels via GABABR activation. Remarkably, all disulfide isomers of the active α-conotoxins Pu1.2 and Pn1.2, and the previously studied Vc1.1 showed similar levels of biological activity. Structure determination by NMR spectroscopy helped us identify a simplified biologically active eight residue peptide motif containing a single disulfide bond that is an excellent lead molecule for developing a new generation of analgesic peptide drugs

Althusser and the Critique of Political Economy

Two disulfide-containing peptides, barrettides A (<b>1</b>) and B (<b>2</b>), from the cold-water marine sponge <i>Geodia barretti</i> are described. Those 31 amino acid residue long peptides were sequenced using mass spectrometry methods and structurally characterized using NMR spectroscopy. The structure of <b>1</b> was confirmed by total synthesis using the solid-phase peptide synthesis approach that was developed. The two peptides were found to differ only at a single position in their sequence. The three-dimensional structure of <b>1</b> revealed that these peptides possess a unique fold consisting of a long β-hairpin structure that is cross-braced by two disulfide bonds in a ladder-like arrangement. The peptides are amphipathic in nature with the hydrophobic and charged residues clustered on separate faces of the molecule. The barrettides were found not to inhibit the growth of either <i>Escherichia coli</i> or <i>Staphylococcus aureus</i> but displayed antifouling activity against barnacle larvae (<i>Balanus improvisus</i>) without lethal effects in the concentrations tested

Structure–Activity Studies Reveal the Molecular Basis for GABA_B‑Receptor Mediated Inhibition of High Voltage-Activated Calcium Channels by α‑Conotoxin Vc1.1

α-Conotoxins are disulfide-bonded peptides from cone snail venoms and are characterized by their affinity for nicotinic acetylcholine receptors (nAChR). Several α-conotoxins with distinct selectivity for nAChR subtypes have been identified as potent analgesics in animal models of chronic pain. However, a number of α-conotoxins have been shown to inhibit N-type calcium channel currents in rodent dissociated dorsal root ganglion (DRG) neurons <i>via</i> activation of G protein-coupled GABA_B receptors (GABA_BR). Therefore, it is unclear whether activation of GABA_BR or inhibition of α9α10 nAChRs is the analgesic mechanism. To investigate the mechanisms by which α-conotoxins provide analgesia, we synthesized a suite of Vc1.1 analogues where all residues, except the conserved cysteines, in Vc1.1 were individually replaced by alanine (A), lysine (K), and aspartic acid (D). Our results show that the amino acids in the first loop play an important role in binding of the peptide to the receptor, whereas those in the second loop play an important role for the selectivity of the peptide for the GABA_BR over α9α10 nAChRs. We designed a cVc1.1 analogue that is >8000-fold selective for GABA_BR-mediated inhibition of high voltage-activated (HVA) calcium channels over α9α10 nAChRs and show that it is analgesic in a mouse model of chronic visceral hypersensitivity (CVH). cVc1.1­[D11A,E14A] caused dose-dependent inhibition of colonic nociceptors with greater efficacy in <i>ex vivo</i> CVH colonic nociceptors relative to healthy colonic nociceptors. These findings suggest that selectively targeting GABA_BR-mediated HVA calcium channel inhibition by α-conotoxins could be effective for the treatment of chronic visceral pain