Formation of mononuclear and chloro-bridged binuclear copper(II) complexes of patellamide D, a naturally occurring cyclic peptide: influence of anion and solvent

Patellamide D (patH(4)) is a cyclic octapeptide isolated from the ascidian Lissoclinum patella. The peptide possesses a 24-azacrown-8 macrocyclic structure containing two oxazoline and two thiazole rings, each separated by an amino acid. The present spectrophotometric, electron paramagnetic resonance (EPR) and mass spectral studies show that patellamide D reacts with CuCl, and triethylamine in acetonitrile to form mononuclear and binuclear copper(II) complexes containing chloride. Molecular modelling and EPR studies suggest that the chloride anion bridges the copper(II) ions in the binuclear complex [Cu-2(patH(2))(mu-Cl)](+). These results contrast with a previous study employing both base and methanol, the latter substituting for chloride in the copper(II) complexes en route to the stable mu-carbonato binuclear copper(II) complex [Cu-2 (patH(2))(mu-CO3)]. Solvent clearly plays an important role in both stabilising these metal ion complexes and influencing their chemical reactivities. (C) 2004 Elsevier Inc. All rights reserved.

Enzymatic characterization and homology model of a catalytically active recombinant West Nile virus NS3 protease

West Nile Virus (WNV) is a mosquito-borne flavivirus with a rapidly expanding global distribution. Infection causes severe neurological disease and fatalities in both human and animal hosts. The West Nile viral protease (NS2B-NS3) is essential for post-translational processing in host-infected cells of a viral polypeptide precursor into structural and functional viral proteins, and its inhibition could represent a potential treatment for viral infections. This article describes the design, expression, and enzymatic characterization of a catalytically active recombinant WNV protease, consisting of a 40-residue component of cofactor NS2B tethered via a noncleavable nonapeptide (G(4)SG(4)) to the N-terminal 184 residues of NS3. A chromogenic assay using synthetic para-nitroanilide (pNA) hexapeptide substrates was used to identify optimal enzyme-processing conditions (pH 9.5, I < 0.1 M, 30% glycerol, 1 mM CHAPS), preferred substrate cleavage sites, and the first competitive inhibitor (Ac-FASGKR- H, IC50 &SIM; 1 μM). A putative three-dimensional structure of WNV protease, created through homology modeling based on the crystal structures of Dengue-2 and Hepatitis C NS3 viral proteases, provides some valuable insights for structure-based design of potent and selective inhibitors of WNV protease.

Testing the energetic equivalence rule with helminth endoparasites of vertebrates

As a general test of the energetic equivalence rule, we examined macroecological relationships among abundance, density and host body mass in a comparative analysis of the assemblages of trophically transmitted endoparasitic helminths of 131 species of vertebrate hosts. Both the numbers and total volume of parasites per gram of host decreased allometrically with host body mass, with slopes roughly consistent with those expected from the allometric relationship between host basal metabolic rate and body mass. From an evolutionary perspective, large body size may therefore allow hosts to escape from the deleterious effects of parasitism.

Magnetosomal matrix: ultrafine structure may template biomineralization of magnetosomes

The organic matrix surrounding bullet-shaped, cubo-octahedral, D-shaped, irregular arrowhead-shaped, and truncated hexa-octahedral magnetosomes was analysed in a variety of uncultured magnetotactic bacteria. The matrix was examined using low- (80 kV) and intermediate- (400 kV) voltage TEM. It encapsulated magnetosomes in dehydrated cells, ultraviolet-B-irradiated dehydrated cells and stained resin-embedded fixed cells, so the apparent structure of the matrix does not appear to be an artefact of specimen preparation. High-resolution images revealed lattice fringes in the matrix surrounding magnetite and greigite magnetosomes that were aligned with lattice fringes in the encapsulated magnetosomes. In all except one case, the lattice fringes had widths equal to or twice the width of the corresponding lattice fringes in the magnetosomes. The lattice fringes in the matrix were aligned with the {311}, {220}, {331}, {111} and {391} related lattice planes of magnetite and the {222} lattice plane of greigite. An unidentified material, possibly an iron hydroxide, was detected in two immature magnetosomes containing magnetite. The unidentified phase had a structure similar to that of the matrix as it contained {311}, {220} and {111} lattice fringes, which indicates that the matrix acts as a template for the spatially controlled biomineralization of the unidentified phase, which itself transforms into magnetite. The unidentified phase was thus called pre-magnetite. The presence of the magnetosomal matrix explains all of the five properties of the biosignature of the magnetosomal chain proposed previously by Friedmann et al. and supports their claim that some of the magnetite particles in the carbonate globules in the Martian meteorite ALH84001 are biogenic. Two new morphologies of magnetite magnetosomes are also reported here (i.e. tooth-shaped and hexa-octahedral magnetosomes). Tooth-shaped magnetite magnetosomes elongated in the [110] direction are reported, and are distinct from arrowhead-shaped and bullet-shaped magnetosomes. Elongation of magnetite magnetosomes in the [110] direction has not been reported previously. A Martian hexa-octahedral magnetite particle was previously characterized by Thomas-Keptra et al. and compared with truncated hexa-octahedral magnetite magnetosomes. Hexa-octahedral magnetite magnetosomes with the same morphology and similar sizes and axial ratios as those reported by Thomas-Keptra et al. are characterized here. These observations support their claim that ALH84001 contains evidence for a past Martian biota.

Milk Proteomics

Milk proteins have been studied continuously for over 50 years. Knowledge of this complex protein system has evolved incrementally in recent decades, largely coinciding with advances in technology. Proteomics and associated technologies have the potential to facilitate further advances in our knowledge of milk proteins. Proteomics allows for the detection, identification and characterization of milk proteins. More importantly, proteomics facilitates the analysis of large numbers of milk proteins simultaneously. In the first part of this review we provide a description of the key techniques used within proteomic methodologies, with an emphasis on their general uses within proteomics. In the second part we summarize recent applications of proteomics to milk proteins and highlight the potential for new and rapid advances in the analysis of milk proteins. In particular, we emphasise the effectiveness of two-dimensional gel electrophoresis in combination with various mass spectrometry techniques for the detailed characterization of milk proteins. (C) 2004 Elsevier Ltd. All rights reserved.

Rare earth element geochemistry of Late Devonian reefal carbonates, canning basin, Western Australia: Confirmation of a seawater REE proxy in ancient limestones

Rare earth element and yttrium (REE+Y) concentrations were determined in 49 Late Devonian reefal carbonates from the Lennard Shelf, Canning Basin, Western Australia. Shale-normalized (SN) REE+Y patterns of the Late Devonian samples display features consistent with the geochemistry of well-oxygenated, shallow seawater. A variety of different ancient limestone components, including microbialites, some skeletal carbonates (stromatoporoids), and cements, record seawater-like REE+Y signatures. Contamination associated with phosphate, Fe-oxides and shale was tested quantitatively, and can be discounted as the source of the REE+Y patterns. Co-occurring carbonate components that presumably precipitated from the same seawater have different relative REE concentrations, but consistent REE+Y patterns. Clean Devonian early marine cements (n = 3) display REE+Y signatures most like that of modern open ocean seawater and the highest Y/Ho ratios (e.g., 59) and greatest light REE (LREE) depletion (average Nd-SN/Yb-SN = 0.413, SD = 0.076). However, synsedimentary cements have the lowest REE concentrations (e.g., 405 ppb). Non-contaminated Devonian microbialite samples containing a mixture of the calcimicrobe Renalcis and micritic thrombolite aggregates in early marine cement (n = 11) have the highest relative REE concentrations of tested carbonates (average total REE = 11.3 ppm). Stromatoporoid skeletons, unlike modern corals, algae and molluscs, also contain well-developed, seawater-like REE patterns. Samples from an estuarine fringing reef have very different REE+Y patterns with LREE enrichment (Nd-SN/Yb-SN > 1), possibly reflecting inclusion of estuarine colloidal material that contained preferentially scavenged LREE from a nearby riverine input source. Hence, Devonian limestones provide a proxy for marine REE geochemistry and allow the differentiation of co-occurring water masses on the ancient Lennard Shelf. Although appropriate partition coefficients for quantification of Devonian seawater REE concentrations from out data are unknown, hypothetical Devonian Canning Basin seawater REE patterns were obtained with coefficients derived from modern natural proxies and experimental values. Resulting Devonian seawater patterns are slightly enriched in LREE compared to most modem seawaters and suggest higher overall REE concentrations, but are very similar to seawaters from regions with high terrigenous inputs. Our results suggest that most limestones should record important aspects of the REE geochemistry of the waters in which they precipitated, provided they are relatively free of terrigenous contamination and major diagenetic alteration from fluids with high, non-seawater-like REE contents. Hence, we expect that many other ancient limestones will serve as seawater REE proxies, and thereby provide information on paleoceanography, paleogeography and geochemical evolution of the oceans. Copyright (C) 2004 Elsevier Ltd.

Small molecules that mimic components of bioactive protein surfaces

Small molecules designed to mimic specific structural components of a protein (peptide strands, sheets, turns, helices, or amino acids) can be expected to display agonist or antagonist biological responses by virtue of interacting with the same receptors that recognize the protein. Here we describe some minimalist approaches to structural mimetics of amino acids and of strand, turn, or helix segments of proteins. The designed molecules show potent and selective inhibition of protease, transferase, and phospholipase enzymes, or antagonism of G-protein coupled or transcriptional receptors, and have potent anti-tumour, anti-inflammatory, or antiviral activity.