Platinum(II) phosphine and orotate complexes with aminopyridine co-ligands, and their molecular recognition via hydrogen bonding

The new complexes [Pt(dppp)(py)(2)][OTf](2), 1, [Pt(dppp)(2-ap)(2)][OTf](2), 2, [(dppp)Pt(mu -OH){mu -NH(C5H3N)NH2}Pt(dppp)][OTf](2), 3 (py=pyridine, 2-ap=2-aminopyridine, NH(C5H3N)NH2=2,6-diaminopyridine anion, dppp = 1,3-bis(diphenylphosphino)propane, OTf=O3SCF3) have been prepared via reactions between [Pt(dppp)(OTf)(2)] and pyridine, 2-aminopyridine or 2,6-diaminopyridine (2,6-dap) respectively. The amines exhibit a range of co-ordination modes. Pyridine and 2-aminopyridine co-ordinate to platinum through endo-nitrogen atoms in complexes 1 and 2, the latter existing as a pair of rotomers due to the steric hindrance introduced by the 2-substituent. However, 2,6-diaminopyridine co-ordinates to platinum through the exo-nitrogen of one amino group, to give the unusual mu -amido complex 3. Reaction of the known orotate chelate complex [Pt(PEt3)(2)(N,O-HL)] [HL=orotate, the dianion of 2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid (orotic acid)] with 2,6-dap gave [Pt(PEt3)(2)(2,6-dap)(N-HL)] 4, which contains an unconventional monodentate orotate ligand. In this co-ordination mode the orotate retains an ADA hydrogen bonding site and was found to co-crystallise with 2,6-dap via complementary ADA:DAD triple hydrogen bonds to give [Pt(PEt3)(2)(N-HL)(2,6-dap)].2,6-dap, 5. Complex 5 exhibits a helical chain structure of associated [1+1] adducts in the solid state.

New insight into mechanisms in water-gas-shift reaction on Au/CeO2(111): A density functional theory and kinetic study

Using density functional theory (DFT) and kinetic analyses, a new carboxyl mechanism for the water-gas-shift reaction (WGSR) on Au/CeO2(111) is proposed. Many elementary steps in the WGSR are studied using an Au cluster supported on CeO2(111). It is found that (i) water can readily dissociate at the interface between Au and CeO2; (ii) CO2 can be produced via two steps: adsorbed CO on the Au cluster reacts with active OH on ceria to form the carboxyl (COOH) species and then COOH reacts with OH to release CO2; and (iii) two adsorbed H atoms recombine to form molecular H-2 on the Au cluster. Our kinetic analyses show that the turnover frequency of the carboxyl mechanism is consistent with the experimental one while the rates of redox and formate mechanisms are much slower than that of carboxyl mechanism. It is suggested that the carboxyl pathway is likely to be responsible for WGSR on Au/CeO2.

A Robust Co-Localisation Measurement Utilising Z-Stack Image Intensity Similarities for Biological Studies

Background: Co-localisation is a widely used measurement in immunohistochemical analysis to determine if fluorescently labelled biological entities, such as cells, proteins or molecules share a same location. However the measurement of co-localisation is challenging due to the complex nature of such fluorescent images, especially when multiple focal planes are captured. The current state-of-art co-localisation measurements of 3-dimensional (3D) image stacks are biased by noise and cross-overs from non-consecutive planes.

Method: In this study, we have developed Co-localisation Intensity Coefficients (CICs) and Co-localisation Binary Coefficients (CBCs), which uses rich z-stack data from neighbouring focal planes to identify similarities between image intensities of two and potentially more fluorescently-labelled biological entities. This was developed using z-stack images from murine organotypic slice cultures from central nervous system tissue, and two sets of pseudo-data. A large amount of non-specific cross-over situations are excluded using this method. This proposed method is also proven to be robust in recognising co-localisations even when images are polluted with a range of noises.

Results: The proposed CBCs and CICs produce robust co-localisation measurements which are easy to interpret, resilient to noise and capable of removing a large amount of false positivity, such as non-specific cross-overs. Performance of this method of measurement is significantly more accurate than existing measurements, as determined statistically using pseudo datasets of known values. This method provides an important and reliable tool for fluorescent 3D neurobiological studies, and will benefit other biological studies which measure fluorescence co-localisation in 3D.

Acid-catalyzed hydrolysis of cellulose and cellulosic waste using a microwave reactor system

A microwave reactor system was investigated as a potential technique to maximize sugar yield for the hydrolysis of municipal solid waste for ethanol production. Specifically, dilute acid hydrolysis of a-cellulose and waste cellulosic biomass (grass clippings) with phosphoric acid was undertaken within the microwave reactor system. The experimental data and reaction kinetic analysis indicate that the use of a microwave reactor system can successfully facilitate dilute acid hydrolysis of cellulose and waste cellulosic biomass, producing high yields of total sugars in short reaction times. The maximum yield of reducing sugars was obtained at 7.5% (w/v) phosphoric acid and 160 degrees C, corresponding to 60% of the theoretical total sugars, with a reaction time of 5 min. When using a very low acid concentration (0.4% w/v) for the hydrolysis in the microwave reactor, it was found that 10 g of total sugars/100 g dry mass was produced, which is significant considering the low acid concentration. When hydrolyzing grass clippings using the microwave reactor, the optimum conditions were an acid concentration of 2.5% (w/v), 175 degrees C with a 15 min reaction time, giving 18 g/100 g dry mass of total sugars, with xylose being the sugar with the highest yield. It was observed that pentose sugars were more easily formed but also more easily degraded, these being significantly affected by increases in acid concentration and temperature. Kinetic modeling of the data indicated that the use of microwave heating may account for an increase in reaction rate constant, k(1), found in this study in comparison with conventional systems described in the literature.

Catalytic Mo2C coatings for the water gas shift reaction: Electrosynthesis in molten salts

Electrosynthesis methods using molten salts are suggested for obtaining a new catalytic system based on the Mo2C/Mo composition for the water gas shift reaction. The coatings obtained by the discharge of the carbonate ion on a molybdenum substrate and by the simultaneous reduction of the electroactive species MoO42 and CO32- are catalytically more active than bulk Mo2C or the commercial catalyst Cu-ZnO-Al2O3 by one and three orders of magnitude, respectively.

Photobleaching of methylene blue sensitised by TiO2: an ambiguous system?

The photobleaching of methylene blue MB, sensitised by TiO2, in an aqueous solution is studied in the absence and presence of oxygen, in the absence of oxygen and in the presence of a sacrificial electron acceptor (SED), MB is photoreduced to its colourless leuco form, LMB, by the TiO2 photocatalyst. This same photoreduction process is observed even if an SED is not present, indicating that MB itself can act as an SED. The oxidation of LMB by oxygen to regenerate MB is significantly slower if the aqueous solution is acidified (0.01 mol dm(-3) HClO4) and, at low partial pressures, the rate of reaction depends directly upon the concentration of dissolved oxygen. The TiO2-sensitised photobleaching of MB is irreversible in an oxygen-saturated aqueous solution, as expected, since the bleaching was due to an oxidative process. However, in an acidified solution (0.01 mol dm(-3) HClO4), the photobleaching process, in an oxygen-saturated solution, generates LMB initially. The latter situation arises because, under acidic conditions, LMB reacts only very slowly with oxygen to form MB. The significance of these findings with respect to the popular use of photobleaching of MB as a demonstration of semiconductor photomineralisation is discussed. (C) 1999 Elsevier Science S.A. All rights reserved.

Path-selective photoinduced electron transfer (PET) in a membrane-associated system studied by pH-dependent fluorescence

The pH-dependent fluorescence behavior of two regioisomeric 'receptor(1)-spacer(1)-fluorophore-spacer(2)-receptor(2)' systems 1 and 2 in micellar solutions of sodium dodecyl sulfate show that photoinduced electron transfer (PET) only occurs from the amine group connected to the 4-amino position of the aminonaphthalimide fluorophore in both cases. This demonstrates the directing influence of the photogenerated electric field within the aminonaphthalimide excited state on the electron transfer process. Since path-selectivity of PET is also known within the membrane-bound photosynthetic reaction center in bacteria, its origins may be illuminated by the simple experiments described here. (C) 2011 Elsevier B. V. All rights reserved.

A role for the enteric nervous system in the response to helminth infections

The enteric nervous system (ENS) in the gut contains a particularly high concentration of nerve cells, and effectively functions as an independent 'minibrain'. Interactions between nerve, endocrine, immune and other cell types allow the sophisticated regulation of normal gut physiology. They can also bring about a co-ordinated response to parasitic infection, possibly leading to expulsion of the parasite. In this review, Derek McKay and Ian Fairweather will consider, in brief, data pertaining to changes in the ENS following intestinal helminth infections and speculate on the role that these alterations may have in the expulsion of the parasite burden and the putative ability of the parasite to modulate these events.

Cellular and subcellular localization of SALMFamide (S1)-like immunoreactivity within the central nervous system of the nematode Ascaris suum (Nematoda, Ascaroidea)

The localization and distribution of SALMFamide (S1)-like immunoreactivity (IR), was determined at both the cellular and subcellular level in the central nervous system (CNS) of the nematode roundworm Ascaris suum. The techniques of indirect immunofluorescence in conjunction with confocal scanning laser microscopy and post-embedding, IgG-conjugated colloidal gold immunostaining were used, respectively. Immunostaining was widespread in the CNS of adult A. suum, with immunoreactivity (IR) being localized in nerve cells and fibres in the ganglia associated with the anterior nerve ring and in the main nerve cords and their commissures. At the subcellular level, gold labeling of peptide was localized exclusively over dense-cored vesicles within nerve cell bodies, nerve axons and nerve terminals of the neuropile of the anterior nerve ring, main ganglia and nerve cords in the CNS. Double-labeling demonstrated an apparent co-localization of S1- and FMRFamide-IR-together IR-together with S1- and pancreatic polypeptide (PP)-IR in the same dense-cored vesicles. Antigen preabsorption experiments indicated little cross-reactivity, if any, between the three antisera; indeed, neither FMRFamide nor PP antigens abolished S1 immunostaining.

ULTRASTRUCTURAL-LOCALIZATION OF PANCREATIC POLYPEPTIDE AND FMRFAMIDE IMMUNOREACTIVITIES WITHIN THE CENTRAL-NERVOUS-SYSTEM OF THE NEMATODE, ASCARIS-SUUM (NEMATODA, ASCAROIDEA)

A post-embedding immunogold technique has been used to examine the subcellular distribution of immunoreactivities to vertebrate pancreatic polypeptide (PP) and to the invertebrate peptide, FMRFamide within the central nervous system (CNS) of the nematode, Ascaris suum. Gold labelling of peptide was localized exclusively over dense-cored vesicles within nerve cell bodies, nerve axons and nerve terminals of the main ganglia and nerve cords in the CNS. Double-labelling of peptides demonstrated an apparent co-localization of PP and FMRFamide immunoreactivities in the same dense-cored vesicles, although populations of dense-cored vesicles that labelled solely for FMRFamide were also evident. Antigen preabsorption studies indicated little or no cross-reactivity between the two antisera.

ULTRASTRUCTURAL-LOCALIZATION OF FMRFAMIDE-IMMUNOREACTIVITY AND PANCREATIC POLYPEPTIDE-IMMUNOREACTIVITY WITHIN THE CENTRAL-NERVOUS-SYSTEM OF THE LIVER FLUKE, FASCIOLA-HEPATICA (TREMATODA, DIGENEA)

A post-embedding immunogold technique was used to examine the subcellular distribution of immunoreactivities to the invertebrate peptide, FMRFamide, and to vertebrate pancreatic polypeptide (PP) within the central nervous system of the trematode, Fasciola hepatica. Gold labeling of peptide was localised exclusively over both dense-cored and ellipsoidal electron-dense vesicles (with a homogeneous matrix) present within nerve cell bodies, small and 'giant' nerve processes of the neuropile in the cerebral ganglia and transverse commissure, as well as in the main longitudinal nerve cords. Double labeling demonstrated an apparent co-localisation of FMRFamide and PP immunoreactivities in the same dense-cored vesicles, although populations of ellipsoidal electron-dense vesicles that labeled solely for FMRFamide were also evident. Antigen pre-absorption studies indicated little, if any, cross-reactivity of the two antisera.

IMMUNOELECTRON MICROSCOPIC STUDIES OF REGULATORY PEPTIDES IN THE NERVOUS-SYSTEM OF THE MONOGENEAN PARASITE, DICLIDOPHORA-MERLANGI

Specific antisera, directed against the highly conserved C-terminal hexapeptide amide of mammalian pancreatic polypeptide (PP) and the invertebrate peptide FMRFamide, have been used in conjunction with post-embedding, IgG-conjugated colloidal gold immunostaining to demonstrate peptide immunoreactivity at subcellular level in the nervous system of adult Diclidophora merlangi. Gold labelling revealed that immunoreactivity for PP and FMRFamide was localized exclusively in dense-cored vesicles occupying the majority of axons in the central nervous system. Double-labelling demonstrated an apparent co-localization of PP and FMRFamide in the same dense-cored vesicles. Antigen preabsorption experiments indicated cross-reactivity of the two antisera as unlikely, and that some if not all of the PP/FMRFamide immunostaining in the parasite was due to a neuropeptide F-like peptide.

ELECTRON IMMUNOGOLD LABELING OF REGULATORY PEPTIDE IMMUNOREACTIVITY IN THE NERVOUS-SYSTEM OF MONIEZIA-EXPANSA (CESTODA, CYCLOPHYLLIDEA)

An electron immunogold-labeling technique was used in conjunction with a post-embedding procedure to demonstrate for the first time the ultrastructural distribution of the parasitic platyhelminth neuropeptide, neuropeptide F (NPF), in the nervous system of the cestode Moniezia expansa. Two axon types, distinguished by their populations of different-sized electron-dense vesicles, were identified. Immunogold labeling demonstrated an apparent homogeneity of PP, FMRFamide and NPF (M. expansa) antigenic sites throughout the larger dense-cored vesicles within the central nervous system. Triple labeling clearly demonstrated the co-localisation of immunoreactivities (IR) for NPF, PP and FMRFamide within the same dense-cored vesicles. The presence of NPF-IR within the vesicles occupying the perikaryon of the neuronal cell body indicated that the peptides had undergone post-translational C-terminal amidation prior to entering the axon. Antigen pre-absorption experiments using NPF prevented labeling with either PP or FMRFamide antisera, and the failure of these antisera to block NPF-IR supports the view that some, if not all, of the PP/FMRFamide-IR is due to NPF-like peptides.

THE CHOLINERGIC, SEROTONINERGIC AND PEPTIDERGIC COMPONENTS OF THE NERVOUS-SYSTEM OF MONIEZIA-EXPANSA (CESTODA, CYCLOPHYLLIDEA)

The central (CNS) and peripheral (PNS) nervous systems of the cyclophyllidean tapeworm, Moniezia expansa, were examined for the presence of cholinergic, serotoninergic and peptidergic elements using enzyme cytochemical and immunocytochemical techniques in conjunction with light and confocal scanning laser microscopy. Cholinesterase activity and 5-hydroxytryptamine- and regulatory peptide-immunoreactivities (IRs) were localized to the nerve fibres and cell bodies of all of the major neuronal components in the CNS of the worm, including the cerebral ganglia and connecting commissure, the 10 longitudinal nerve cords and associated transverse ring commissures. Although each of the 3 systems appeared well developed and comprised a significant portion of the nervous system, the serotoninergic constituent was the most highly developed, consisting of a vast array of nerve fibres and cell bodies distributed throughout the strobila of the worm. A close association of cholinesterase reactivity and peptide-IRs was evident throughout the CNS, indicating the possible co-localization of acetylcholine and neuropeptides. Within the PNS, cholinergic activity and serotoninergic- and peptidergic-IRs occurred in the subtegumental network of nerve fibres and somatic musculature. Although all 3 neurochemical elements were present in the acetabula, they were found in different nerve fibres; only cholinergic and peptidergic cell bodies were found. The common genital opening, vagina and ootype regions of the reproductive system displayed a rich innervation of all 3 types of neuronal populations. Within the peptidergic system, immunostaining with antisera raised to the C-terminus of the neuropeptide Y superfamily of peptides and the invertebrate peptides, neuropeptide F (M. expansa) and FMRFamide was the most prevalent. Limited positive-IR for substance P and neurokinin A were also recorded in the CNS of the worm.