Synthesis and characterization of delta-atracotoxin-ar1a, the lethal neurotoxin from venom of the Sydney funnel-web spider (Atrax robustus)

delta-Atracotoxin-Ar1a (delta-ACTX-Ar1a) is the major polypeptide neurotoxin isolated from the venom of the male Sydney funnel-web spider, Atrax robustus. This neurotoxin targets both insect and mammalian voltage-gated sodium channels, where it competes with scorpion alpha-toxins for neurotoxin receptor site-3 to slow sodium-channel inactivation. Progress in characterizing the structure and mechanism of action of this toxin has been hampered by the limited supply of pure toxin from natural sources. In this paper, we describe the first successful chemical synthesis and oxidative refolding of the four-disulfide bond containing delta-ACTX-Ar1a. This synthesis involved solid-phase Boc chemistry using double coupling, followed by oxidative folding of purified peptide using a buffer of 2 M GdnHCl and glutathione/glutathiol in a 1:1 mixture of 2-propanol (pH 8.5). Successful oxidation and refolding was confirmed using both chemical and pharmacological characterization. Ion spray mass spectrometry was employed to confirm the molecular weight. H-1 NMR analysis showed identical chemical shifts for native and synthetic toxins, indicating that the synthetic toxin adopts the native fold. Pharmacological studies employing whole-cell patch clamp recordings from rat dorsal root ganglion neurons confirmed that synthetic delta-ACTX-Ar1a produced a slowing of the sodium current inactivation and hyperpolarizing shifts in the voltage-dependence of activation and inactivation similar to native toxin. Under current clamp conditions, we show for the first time that delta-ACTX-Ar1a produces spontaneous repetitive plateau potentials underlying the clinical symptoms seen during envenomation. This successful oxidative refolding of synthetic delta-ACTX-Ar1a paves the way for future structure-activity studies to determine the toxin pharmacophore.

An 18th century understanding of migraine - Samuel Tissot (1728-1797)

During the period 1778-1780 the Swiss physician Samuel A A D Tissot (1728-1797) published his Traite des nerfs et de leur maladies, a work which continued to be available and widely influential until at least the middle of the following century. It contained a long chapter dealing with migraine, based on the earlier literature on the topic and on Tissot's own clinical experience. The work appeared at the beginning of the modern era of interest in migraine, and provided the first reasonably adequate and systematic account of the disorder to become widely available. Its descriptions of migraine phenomena have an enduring validity, though Tissot's ideas on the pathogenesis of the disorder, viz. that it usually arose from stomach disturbance, were not founded on satisfactory evidence and are long since superseded. (C) 2003 Elsevier Science Ltd. All rights reserved.

Wired communities in the city: Sydney, Australia

Questions relating to the ability of particular groups in society to access information and communications technologies (ICTs) have become a growing part of the academic and policy literature. The issues raised in this literature have revolved around a number of themes, many of which can be subsumed under concerns about a growing digital divide whereby society is being divided into information rich and information poor sectors. This differentiation can be between particular social groups irrespective of place, or between people in particular places be these large regional areas (e.g. metropolitan versus non-metropolitan) or localities and communities within an urban area. This paper focuses on the existence of a 'digital divide' across the Sydney metropolitan area. Using ABS 2001 census data the paper presents an analysis of computer and internet access and use for clusters of local communities and focuses on how usage differs across communities as differentiated by socio-economic status, household and family status and ethnic background