An eels study of water, methanol, formaldehyde and formic acid adsorbed on clean and oxygen-covered zinc(0001) surfaces

Water adsorbs molecularly on a clean Zn(0001) surface; on a surface covered with atomic oxygen, however, hydroxyl species is produced due to proton abstraction by the surface oxygen atoms. Methanol, molecularly adsorbed on a clean surface at 80 K, transforms to methoxy species above 110 K. On an atomic oxygen-covered surface, adsorbed methanol gives rise to methoxy species and water, the latter arising from proton abstraction. HCHO adsorbs molecularly at 80 K on both clean as well as oxygen-covered surfaces and polymerizes at higher temperatures. Formic acid does not adsorb on a clean Zn surface, but on an oxygen-covered surface gives rise to formate and hydroxyl species.

A Radical Cyclization Route To +/-Andirolactone, A Spiro-Gamma-Butyrolactone

Synthesis of Andirolactone (Image ), starting from 4-methyl cyclohex-3-en-1-one (Image ), via the radical cyclisation of the bromoacetal (Image ), is described.

Enzyme-catalysed non-oxidative decarboxylation of aromatic acids: I.Purification and spectroscopic properties of 2,3 dihydroxybenzoic acid decarboxylase from Image Image

In order to understand the molecular mechanism of non-oxidative decarboxylation of aromatic acids observed in microbial systems, 2,3 dihydroxybenzoic acid (DHBA) decarboxylase from Image Image was purified to homogeneity by affinity chromatography. The enzyme (Mr 120 kDa) had four identical subunits (28 kDa each) and was specific for DHBA. It had a pH optimum of 5.2 and Km was 0.34mM. The decarboxylation did not require any cofactors, nor did the enzyme had any pyruvoyl group at the active site. The carboxyl group and hydroxyl group in the Image -position were required for activity. The preliminary spectroscopic properties of the enzyme are also reported.

Neuronal oscillations in gamma- and alpha-frequency bands: from object representations to sensory awareness

The synchronization of neuronal activity, especially in the beta- (14-30 Hz) /gamma- (30 80 Hz) frequency bands, is thought to provide a means for the integration of anatomically distributed processing and for the formation of transient neuronal assemblies. Thus non-stimulus locked (i.e. induced) gamma-band oscillations are believed to underlie feature binding and the formation of neuronal object representations. On the other hand, the functional roles of neuronal oscillations in slower theta- (4 8 Hz) and alpha- (8 14 Hz) frequency bands remain controversial. In addition, early stimulus-locked activity has been largely ignored, as it is believed to reflect merely the physical properties of sensory stimuli. With human neuromagnetic recordings, both the functional roles of gamma- and alpha-band oscillations and the significance of early stimulus-locked activity in neuronal processing were examined in this thesis. Study I of this thesis shows that even the stimulus-locked (evoked) gamma oscillations were sensitive to high-level stimulus features for speech and non-speech sounds, suggesting that they may underlie the formation of early neuronal object representations for stimuli with a behavioural relevance. Study II shows that neuronal processing for consciously perceived and unperceived stimuli differed as early as 30 ms after stimulus onset. This study also showed that the alpha band oscillations selectively correlated with conscious perception. Study III, in turn, shows that prestimulus alpha-band oscillations influence the subsequent detection and processing of sensory stimuli. Further, in Study IV, we asked whether phase synchronization between distinct frequency bands is present in cortical circuits. This study revealed prominent task-sensitive phase synchrony between alpha and beta/gamma oscillations. Finally, the implications of Studies II, III, and IV to the broader scientific context are analysed in the last study of this thesis (V). I suggest, in this thesis that neuronal processing may be extremely fast and that the evoked response is important for cognitive processes. I also propose that alpha oscillations define the global neuronal workspace of perception, action, and consciousness and, further, that cross-frequency synchronization is required for the integration of neuronal object representations into global neuronal workspace.

An EXAFS study of the cobalt-molybdenum/.gamma.-alumina hydrodesulfurization catalyst

While Mo in the Co-Mo/y-A1203 hydrodesulfurization catalyst is present as a sulfidic species similar to MoS2, Co shows two types of coordination, one with six sulfurs (but not a bulk sulfide) and the other with four oxygens. The significance of such species is discussed. In addition to an additive relation of the EXAFS function and the residual spectra, the ratio of amplitude terms of the catalyst and the model system has been employed in the analysis.

Complexes of lanthanide perchlorates with two new O,N,O ligands derived from antipyraldehyde and acetic and benzoic acid hydrazides

Antipyrine is a well known ligand for lanthanides (I). A forage through the organic literature of pyrazolones reveals that the 4-position of antipyrine is amenable to a wide variety of organic reactions. It should thus be possible to introduce suitable functional groups at this position and design new multidentate ligands for metal ions. It is also found that the coordination chemistry of lanthanides is much less well developed and far fewer ligands have been used for complexation with lanthanide ions compared to that of the d-transition metal ions. Keeping these points in view we have reported earlier, complexes of lanthanides with a bidentate ligand N,N-diethyl-antipyrine-4-carboxamide (2). In this communication we report the synthesis of two new ligands from Schiff base condensation of antipyraldehyde and the hydrazides of acetic and benzoic acids and the complexes formed by these hydrazones with lanthanide perchlorates.

Theoretical studies on the conformation of beta-D-N-acetyl neuraminic acid (sialic acid)

The possible conformations of sialic acid were analysed using semi-empirical potential functions. The solid state conformation has approx. 0.2 kcal/mol higher energy than the minimum energy conformation. These studies suggest that in solution sialic acid may exist preponderantly in two different conformations which differ in the orientation of the terminal hydroxymethyl group of glycerol side-chain. The present model is consistent with 1H- and 13C-NMR data, but differs from the earlier models.

Synthesis, Binding and Bioactivity of [gamma]-Methylene [gamma]-Lactam Ecdysone Receptor Ligands: Advantages of QSAR Models for Flexible Receptors

Nuclear hormone receptors, such as the ecdysone receptor, often display a large amount of induced fit to ligands. The size and shape of the binding pocket in the EcR subunit changes markedly on ligand binding, making modelling methods such as docking extremely challenging. It is, however, possible to generate excellent 3D QSAR models for a given type of ligand, suggesting that the receptor adopts a relatively restricted number of binding site configurations or [`]attractors'. We describe the synthesis, in vitro binding and selected in vivo toxicity data for [gamma]-methylene [gamma]-lactams, a new class of high-affinity ligands for ecdysone receptors from Bovicola ovis (Phthiraptera) and Lucilia cuprina (Diptera). The results of a 3D QSAR study of the binding of methylene lactams to recombinant ecdysone receptor protein suggest that this class of ligands is indeed recognized by a single conformation of the EcR binding pocket.

Oxidative and photooxidative degradation of poly(acrylic acid)

The oxidative degradation of poly(acrylic acid) (PAA), a water soluble polymer, was studied at various temperatures with different concentrations of persulfates, potassium persulfate (KPS), ammonium persulfate (APS) and sodium persulfate (SPS). The photodegradation of PAA was also examined with APS as oxidizer. The degraded samples were analyzed for the time evolution of molecular weight distribution by gel permeation chromatography. A theoretical model based on the continuous distribution kinetics was developed that accounted for the polymer degradation and the dissociation of persulfate. The rate coefficients for the oxidative and photooxidative degradation of PAA were determined from the parametric fit of the model with experimental data. The rate of degradation increased with increasing amount of persulfate in both oxidative and photooxidative degradation. The rate of degradation also increased with increasing temperature in the case of oxidative degradation.

Expression of functional GABAc receptors in the brain

γ-aminobutyric acid (GABA) is the main inhibitory transmitter in the nervous system and acts via three distinct receptor classes: A, B, and C. GABAC receptors are ionotropic receptors comprising ρ subunits. In this work, we aimed to elucidate the expression of ρ subunits in the postnatal brain, the characteristics of ρ2 homo-oligomeric receptors, and the function of GABAC receptors in the hippocampus. In situ hybridization on rat brain slices showed ρ2 mRNA expression from the newborn in the superficial grey layer of the superior colliculus, from the first postnatal week in the hippocampal CA1 region and the pretectal nucleus of the optic tract, and in the adult dorsal lateral geniculate nucleus. Quantitative RT-PCR revealed expression of all three ρ subunits in the hippocampus and superior colliculus from the first postnatal day. In the hippocampus, ρ2 mRNA expression clearly dominated over ρ1 and ρ3. GABAC receptor protein expression was confirmed in the adult hippocampus, superior colliculus, and dorsal lateral geniculate nucleus by immunohistochemistry. From the selective distribution of ρ subunits, GABAC receptors may be hypothesized to be specifically involved in aspects of visual image motion processing in the rat brain. Although previous data had indicated a much higher expression level for ρ2 subunit transcripts than for ρ1 or ρ3 in the brain, previous work done on Xenopus oocytes had suggested that rat ρ2 subunits do not form functional homo-oligomeric GABAC receptors but need ρ1 or ρ3 subunits to form hetero-oligomers. Our results demonstrated, for the first time, that HEK 293 cells transfected with ρ2 cDNA displayed currents in whole-cell patch-clamp recordings. Homomeric rat ρ2 receptors had a decreased sensitivity to, but a high affinity for picrotoxin and a marked sensitivity to the GABAC receptor agonist CACA. Our results suggest that ρ2 subunits may contribute to brain function, also in areas not expressing other ρ subunits. Using extracellular electrophysiological recordings, we aimed to study the effects of the GABAC receptor agonists and antagonists on responses of the hippocampal neurons to electrical stimulation. Activation of GABAC receptors with CACA suppressed postsynaptic excitability and the GABAC receptor antagonist TPMPA inhibited the effects of CACA. Next, we aimed to display the activation of the GABAC receptors by synaptically released GABA using intracellular recordings. GABA-mediated long-lasting depolarizing responses evoked by high-frequency stimulation were prolonged by TPMPA. For weaker stimulation, the effect of TPMPA was enhanced after GABA uptake was inhibited. Our data demonstrate that GABAC receptors can be activated by endogenous synaptic transmitter release following strong stimulation or under conditions of reduced GABA uptake. The lack of GABAC receptor activation by less intensive stimulation under control conditions suggests that these receptors are extrasynaptic and activated via spillover of synaptically released GABA. Taken together with the restricted expression pattern of GABAC receptors in the brain and their distinctive pharmacological and biophysical properties, our findings supporting extrasynaptic localization of these receptors raise interesting possibilities for novel pharmacological therapies in the treatment of, for example, epilepsy and sleep disorders.

Relationships between Indole-3-butyric Acid, Photoinhibition and Adventitious rooting of Corymbia torelliana, C. citriodora and F1 Hybrid Cuttings

Rooted cutting propagation is widely used for maximising tree yield, quality and uniformity in conjunction with clonal selection. Some eucalypt species are deployed as rooted cuttings but many are considered to difficult to root. This study examined IBA effects on photoinhibition, root formation, mortality and root and shoot development in cuttings of Corymbia torelliana, C. citriodora and their hybrids. IBA had little or no effect on photoinhibition but it had strong, dose-dependent effects on root formation and mortality. IBA frequently increases primary root number of rooted cutting but it did not increase total root weight, length, surface area or volume, possibly because the highest doe (8g IBA/kg IBA/kg powder) caused leaf abscission and sometimes reduced leaf area (by 55-79%)or shoot dry weight (by 40-58%). An intermediate dose (3g IBA/kg powder) most consistnely improved root formation with little or no effect on mortality or shoot development. Across the F1 hybrid families this treatment increased the number of rooted cuttings by 72-121% and more than ddoubled the number of primary roots per rooted cutting (from 1.1-1.7 roots to 3.5-4.1 roots). This simple treatment will facilitate commercial multiplication of superior individuals or selected families of C. torelliana x C. citriodora through a vegetative propagation system.

Transcriptional regulation by the orphan nuclear receptor ERRgamma

The nuclear receptor (NR) superfamily is comprised of receptors for small lipopfilic ligands such as steroid hormones, thyroid hormone, retinoids, and vitamin D. NRs are ligand-inducible transcription factors capable of both activating and repressing their target gene expression. They control a wide range of biological functions connected to growth, development, and homeostasis. In addition to the ligand-regulated receptors, the family includes a large group of receptors whose physiological ligands are unknown. These receptors are referred to as orphan NRs. Estrogen-related receptor gamma (ERRgamma) belongs to the ERR subfamily of orphan NRs together with the related ERRalpha and ERRbeta. ERRs share amino acid sequence homology with the classical estrogen receptors (ERs) but they are unable to bind natural estrogenic ligands. ERRgamma is expressed in several embryonic and adult tissues but its biological role is still largely unknown. ERRgamma activates reporter gene expression in transfected cells independently of added hormones implying that ERRgamma harbors constitutive activity. However, the intrinsic activity of ERRgamma can be inhibited by synthetic compounds such as the selective estrogen receptor modulator 4-hydroxytamoxifen (4-OHT). Ligands of NRs can act as agonists that activate transcription, as antagonists that prevent activation of transcription, or as inverse agonists that antagonize the constitutive transcriptional activity of receptor. Most of the synthetic ERRgamma ligands act as inverse agonists but recently, a synthetic ERRgamma agonist GSK4716 was identified. This demonstrates that it is possible to design and identify agonists for ERRgamma. Prior to this thesis work, the structural and functional characteristics of ERRgamma were largely unknown. The aim of this study was to define the functional requirements for ERRgamma-mediated transcriptional regulation and to examine the cross-talk between ERRgamma and other NRs. Due to the fact that natural physiological ligands of ERRgamma are unknown, another aim of this study was to seek new natural compounds that may affect transcriptional activity of ERRgamma. Plant-derived phytoestrogens have previously been shown to act as ligands for ERs and ERRalpha, and therefore the effects of these compounds were also studied on ERRgamma-mediated transcriptional regulation. This work demonstrated that ERRgamma-mediated transcriptional regulation was dependent on DNA-binding, dimerization and activation function-2. Heterodimerization with ERRalpha inhibited the transcriptional activity of ERRgamma. In addition to 4-OHT, another anti-estrogen, 4-hydroxytoremifene (4-OHtor), was identified as an inverse agonist of ERRgamma. Interestingly, ERRgamma activated transcription in the presence of 4-OHT and 4-OHtor on activator protein-1 binding sites. ERRgamma was found to interact with another orphan NR Nurr1 by repressing the ability of Nurr1 to activate transcription of the osteopontin gene. Transcriptional activity of ERRgamma was shown to be stimulated by the phytoestrogen equol. Structural model analysis and mutational experiments indicated that equol was able to bind to the ligand binding domain of ERRgamma. The growth inhibitory effect of ERRgamma on prostate cancer cells was found to be enhanced by equol. In summary, this study demonstrates that despite the absence of an endogenous physiological ligand, the activity of ERRgamma can be modulated in other ways such as dimerization with related receptors or by cross-talk with other transcription factors as well as by binding some synthetic or natural compounds.

Identification of amino acid residues essential for enzyme activity of sheep liver 5,10-methylenetetrahydrofolate reductase

Sheep liver 5,10-methylenetetrahydrofolate reductase was subjected to specific chemical modification with phenylglyoxal, diethyl pyrocarbonate and N-bromosuccinimide. The second-order rate constants for inactivation were calculated to be 54 M-1 X min-1, 103 M-1 X min-1 and 154 M-1 X min-1 respectively. This inactivation could be prevented by incubation with substrates or products, suggesting that the residues modified, namely arginine, histidine and tryptophan, are essential for enzyme activity.

Recovery of fish and crustacean communities during remediation of tidal wetlands affected by leachate from acid sulfate soils in north-eastern Australia.

In the 1970s, acid sulfate soils (ASS) distributed within about 720 ha of predominantly mangrove and salt pan wetlands at East Trinity in north Queensland were developed after the area was isolated from tidal flooding by a surrounding seawall and the installation of tidal gates on major drainage creeks. Following drainage and oxidation of these estuarine acidic sediments, resultant acid leachate caused considerable, ongoing environmental problems including regular fish kills. A rehabilitation program covering much of these former tidal wetlands commenced in 2000 using a lime-assisted tidal exchange management regime. Changes in the established populations of estuarine fish and crustaceans were monitored in the two creeks (Firewood and Hills Creeks) where tidal flows were reinstated. In Firewood Creek between 2001 and 2005, there was a progressive increase in fish species richness, diversity and abundance. The penaeid prawn Fenneropenaeus merguiensis was a major component of the cast net catches in the lower sections of both Firewood and Hills Creeks but its relative abundance decreased upstream of the tidal gates on the seawall. Well established stocks of predominantly juvenile, male Scylla serrata resident upstream of the tidal gates indicated suitable habitats with acceptable water and sediment quality and adequate availability of food. The regular fish kills that occurred prior to the management regime abated and, overall, the implementation of the rehabilitation program is yielding positive benefits for the local fisheries.