Inhibition of the norepinephrine transporter by χ-conotoxin dendrimers.

Peptide dendrimers are a novel class of macromolecules of emerging interest with the potential of delayed renal clearance due to their molecular size and enhanced activity due to the multivalency effect. In this work, an active analogue of the disulfide-rich χ-conotoxin χ-MrIA (χ-MrIA), a norepinephrine reuptake (norepinephrine transporter) inhibitor, was grafted onto a polylysine dendron. Dendron decoration was achieved by employing copper-catalyzed alkyne-azide cycloaddition with azido-PEG chain-modified χ-MrIA analogues, leading to homogenous 4-mer and 8-mer χ-MrIA dendrimers with molecular weights ranging from 8 to 22 kDa. These dendrimers were investigated for their impact on peptide secondary structure, in vitro functional activity, and potential anti-allodynia in vivo. NMR studies showed that the χ-MrIA tertiary structure was maintained in the χ-MrIA dendrimers. In a functional norepinephrine transporter reuptake assay, χ-MrIA dendrimers showed slightly increased potency relative to the azido-PEGylated χ-MrIA analogues with similar potency to the parent peptide. In contrast to χ-MrIA, no anti-allodynic action was observed when the χ-MrIA dendrimers were administered intrathecally in a rat model of neuropathic pain, suggesting that the larger dendrimer structures are unable to diffuse through the spinal column tissue and reach the norepinephrine transporter.NHMRC Grants: 1045964 & 107211

Synthesis of the simple peptide model ac-abu(po3H2)-NHMe

The simple model substrate AC-L-Abu(POH)- NHMewas prepared by the use of the protected 4(diethylphosphono) butanoic acid derivative Boc -Abu(POEt)-OH in the Boc mode of solution phase peptide synthesis. The protected peptide model Ac-Abu(P0Et)- NHMe was prepared by initial reaction of the isobutoxycarbonyl mixed anhydride of Boc-Abu(POEt)-OH with N-methylamine followed by cleavage of the Boc group from Boc -Abu(POEt)- NHMe with 4 M HCl/dioxan and N- acetylation of H-Abu(POEt)-NHMe. HCl with the isobutoxycarbonyl mixed anhydride of acetic acid. Cleavage of the phosphonate ethyl groups was effected with 33% hydrogen bromidelacetic acid or 10% bromotrimethylsilane/acetonitrile to give AC-L-Abu(POH)-NHMe in near-quantitative yield

The solid phase synthesis of dihydro- and tetrahydroisoquinolines

Tetrahydroisoquinolines have been synthesised on Merrifield resin in good yields and high purity via the Bischler-Napieralski approach. A one pot multiple synthesis was developed and the reaction sequence monitored using ionspray mass spectrometry

Fascinating Funnel-web findings

Australian Funnel-web spiders can lay claim to being the world's most venomous spider. Surprisingly few studies on the lethal cocktail of venom peptides have been undertaken. New investigations reveal that the venom of these spiders contains toxins with novel pharmacology and potential as natural insecticide or pharmaceutical leads

Rapid chemical protein synthesis-meeting the future demands of biotechnology

The human genome project has provided scientists with a vast multitude of peptide sequences to investigate. The challenge in the post genomic era is to develop methods to synthesise these peptides rapidly and inexpensively

Australian funnel-web spider venom analyzed with on-line RP-HPLC techniques

[Extract] Venoms have attracted significant study in recent years as a reservoir of complex libraries of natural products possessing a wide range of biological activities. Moreover, venoms contain specific and potent molecules that may be utilized in pharmaceutical development and in the production of environmentally friendly insecticides. The compositions of venoms are typically highly complex and contain a variety of molecules including proteins, peptides, and numerous types of small molecules. This complexity requires highly sensitive techniques to allow separation of these components for study. The techniques should also be able to accommodate large variations in sample size to account for the differences in venom available from different creatures (e.g., some snakes can supply up to 500 mg of crude venom from a single milking, whereas some small insects, such as ants, supply submicrogram amounts [1] ). These qualities have been found and continue to be advanced in the technique high performance liquid chromatography (HPLC), in particular reversed-phase HPLC (RP-HPLC). This technique combined with a variety of detection methods can allow the collection of a significant amount of data from very small venom samples

A novel thioether linker: Chemical synthesis of a HIV-1 protease analogue by thioether ligation

Using the novel thioether linker 4-[N-Boc-2-aminoethylmercapto] methyl phenoxyacetic acid, peptides bearing a C-terminal thiol functionality were synthesieed. Reaction of the thiol functionalised peptide with an N-terminal bromoacetylated peptide led to ligation of the two peptides via a thioether bond. The strategy was used to synthesise an enzymatically active analogue of HIV-1 Protease

Drugs from the peptide venoms of marine cone shells.

Australian cone shell venoms are being investigated as an exciting new source of bioactive peptides as part of a new collaborative project between the 3D Centre and AMRAD. Initial studies have already revealed a number of new and novel acting peptides amongst the hundred or so small, heavily constrained peptides present in the venom of each cone shell. The aim of the project is to develop peptidomimetic drugs based on a selection of these native peptides