Enrichment, isolation and characterisation of ruminal bacteria that degrade non-protein amino acids from the tropical legume Acacia angustissima

Acacia angustissima has been proposed as a protein supplement in countries where low quality forages predominate. A number of non-protein amino acids have been identified in the leaves of A. angustissima and these have been linked to toxicity in ruminants. The non-protein amino acid 4-n-acetyl-2,4-diaminobutyric acid (ADAB) has been shown to be the major amino acid in the leaves of A. angustissima. The current study aimed to identify micro-organisms from the rumen environment capable of degrading ADAB by using a defined rumen-simulating media with an amino acid extract from A. angustissima. A mixed enrichment culture was obtained that exhibited substantial ADAB-degrading ability. Attempts to isolate an ADAB-degrading micro-organism were carried out, however no isolates were able to degrade ADAB in pure culture. This enrichment culture was also able to degrade the non-protein amino acids diaminobutyric acid (DABA) and diaminopropionic acid (DAPA) which have structural similarities to ADAB. Two isolates were obtained which could degrade DAPA. One isolate is a novel Grain-positive rod (strain LPLR3) which belongs to the Firmicutes and is not closely related to any previously isolated bacterium. The other isolate is strain LPSR1 which belongs to the Gammaproteobacteria and is closely related (99.93% similar) to Klebsiella pneumoniae subsp. ozaenae. The studies demonstrate that the rumen is a potential rich source of undiscovered micro-organisms which have novel capacities to degrade plant secondary compounds. (c) 2005 Elsevier B.V. All rights reserved.

Synthesis and characterization of mesoporous nickel oxide and its application to electrochemical capacitor

Mesoporous Ni(OH)(2) was synthesized using cationic surfactant as template and urea as hydrolysis-controlling agent. Mesoporous NiO with centralized pore size distribution was obtained by calcining Ni(OH)(2) at different temperatures. The BET specific surface area reaches 477.7 m(2).g(-1) for NiO calcined at 523 K. Structure characterizations indicate the polycrystalline pore wall of mesoporous nickel oxide. The pore-formation mechanism is also deduced to be quasi-reverse micelle mechanism. Cyclic voltammetry shows the good capacitive behavior of these NiO samples due to its unique mesoporous structure when using large amount of NiO to fabricate electrode. Compared with NiO prepared by dip-coating and cathodic precipitation methods, this mesoporous NiO with controlled pore structure can be used in much larger amount to fabricate the electrode and still maintains high specific capacitance and good capacitive behavior.

Synthesis and characterization of turbostratic carbons prepared by catalytic chemical vapour decomposition of acetylene

The turbostratic mesoporous carbon blacks were prepared by catalytic chemical vapour decomposition (CCVD) of acetylene using Ni/MgO catalysts prepared by co-precipitation. The relationship between deposition conditions and the nanostructures of resultant carbon black materials was investigated. It was found that the turbostratic and textural structures of carbon blacks are dependent on the deposition temperature and nickel catalyst loading. Higher deposition temperature increases the carbon crystallite unit volume V-nano and reduces the surface area of carbon samples. Moreover, a smaller V-nano is produced by a higher Ni loading at the same deposition temperature. In addition of the pore structure and the active metal surface area of the catalyst, the graphitic degree or electronic conductivity of the carbon support is also a key issue to the activity of the supported catalyst. V-nano is a very useful parameter to describe the effect of the crystalline structure of carbon blacks on the reactivity of carbon blacks in oxygen-carbon reaction and the catalytic activity of carbon-supported catalyst in ammonia decomposition semi-quantitatively. (C) 2006 Elsevier B.V. All rights reserved.

Chemical synthesis and biosynthesis of the cyclotide family of circular proteins

Cyclotides are a recently discovered class of proteins that have a characteristic head-to-tail cyclized backbone stabilized by a knotted arrangement of three disulfide bonds. They are exceptionally resistant to chemical, enzymatic and thermal treatments because of their unique structural scaffold. Cyclotides have a range of bio-activities, including uterotonic, anti-HIV, anti-bacterial and cytotoxic activity but their insecticidal properties suggest that their natural physiological role is in plant defense. They are genetically encoded as linear precursors and subsequently processed to produce mature cyclic peptides but the mechanism by which this occurs remains unknown. Currently most cyclotides are obtained via direct extraction from plants in the Rubiaceae and Violaceae families. To facilitate the screening of cyclotides for structure-activity studies and to exploit them in drug design or agricultural applications a convenient route for the synthesis of cyclotides is vital. In this review the current chemical, recombinant and biosynthetic routes to the production of cyclotides are discussed.

Isolation and characterisation of conomap-Vt, a D-amino acid containing excitatory peptide from the venom of a vermivorous cone snail

Cone snail venom is a rich source of bioactives, in particular small disulfide rich peptides that disrupt synaptic transmission. Here, we report the discovery of conomap-Vt (Conp-Vt), an unusual linear tetradecapeptide isolated from Conus vitulinus venom. The sequence displays no homology to known conopeptides, but displays significant homology to peptides of the MATP (myoactive tetradecapeptide) family, which are important endogenous neuromodulators in molluscs, annelids and insects. Conp-Vt showed potent excitatory activity in several snail isolated tissue preparations. Similar to ACh, repeated doses of Conp-Vt were tachyphylactic. Since nicotinic and muscarinic antagonists failed to block its effect and Conp-Vt desensitised tissue remained responsive to ACh, it appears that Conp-Vt contractions were non-cholinergic in origin. Finally, biochemical studies revealed that Conp-Vt is the first member of the MATP family with a D-amino acid. Interestingly, the isomerization of L-Phe to D-Phe enhanced biological activity, suggesting that this post-translational modified conopeptide may have evolved for prey capture. (c) 2006 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.

Resolution and characterisation of multiple isoforms of bovine kappa-casein by 2-DE following a reversible cysteine-tagging enrichment strategy

Visualisation of multiple isoforms of kappa-casein on 2-D gels is restricted by the abundant alpha- and beta-caseins that not only limit gel loading but also migrate to similar regions as the more acidic kappa-casein isoforms. To overcome this problem, we took advantage of the absence of cysteine residues in alpha(S1)- and beta-casein by devising an affinity enrichment procedure based on reversible biotinylation of cysteine residues. Affinity capture of cysteine-containing proteins on avidin allowed the removal of the vast majority of alpha(S1)- and beta-casein, and on subsequent 2-D gel analysis 16 gel spots were identified as kappa-casein by PMF. Further analysis of the C-terminal tryptic peptide along with structural predictions based on mobility on the 2-D gel allowed us to assign identities to each spot in terms of genetic variant (A or B), phosphorylation status (1, 2 or 3) and glycosylation status (from 0 to 6). Eight isoforms of the A and B variants with the same PTMs were observed. When the casein fraction of milk from a single cow, homozygous for the B variant of kappa-casein, was used as the starting material, 17 isoforms from 13 gel spots were characterised. Analysis of isoforms of low abundance proved challenging due to the low amount of material that could be extracted from the gels as well as the lability of the PTMs during MS analysis. However, we were able to identify a previously unrecognised site, T-166, that could be phosphorylated or glycosylated. Despite many decades of analysis of milk proteins, the reasons for this high level of heterogeneity are still not clear.

Synthesis and characterization of Pd(II) and Pt(II) complexes with triazolopyrimidine derivatives: The crystal structure of [Pd2L2Cl4] where L=5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine

The Pd(II) and Pt(II) complexes with triazolopyrimidine C-nucleosides L-1 (5,7-dimethyl-3-(2',3',5'-tri-O-benzoyl-beta-D-ribofuranosyl-s-triazolo)[4,3-a]pyrimidine), L-2 (5,7-dimethyl-3-beta-D-ribofuranosyl-s-triazolo [4,3-a]pyrimidine) and L-3 (5,7-dimethyl[1,5-a]-s-triazolopyrimidine), [Pd(en)(L-1)](NO3)(2), (Pd(bpy)(L-1)](NO3)(2), cis-Pd(L-3)(2)Cl-2, [Pd-2(L-3)(2)Cl-4]center dot H2O, cis-Pd(L-2)(2)Cl-2 and [Pt-3(L-1)(2)Cl-6] were synthesized and characterized by elemental analysis and NMR spectroscopy. The structure of the [Pd-2(L-3)(2)Cl-4]center dot H2O complex was established by Xray crystallography. The two L-3 ligands are found in a head to tail orientation, with a (PdPd)-Pd-... distance of 3.1254(17) angstrom.L-1 coordinates to Pd(II) through N8 and N1 forming polymeric structures. L-2 coordinates to Pd(II) through N8 in acidic solutions (0.1 M HCl) forming complexes of cis-geometry. The Pd(II) coordination to L-2 does not affect the sugar conformation probably due to the high stability of the C-C glycoside bond. (c) 2006 Elsevier B.V. All rights reserved.