945 research outputs found
Investigating the chemistry of lipoyl synthase
No full textThe radical SAM protein lipoyl synthase (LipA) is essential for lipoic acid biosynthesis via sulfur insertions into the unactivated C6 and C8 centres of a protein-bound octanoyl group. Using an in vitro assay which makes use of a small peptide mimic of the protein substrate, it has now been shown at which carbon centre sulfur insertion first occurs. LCMS analysis of reactions using labeled substrates and proton NMR characterization of an isolated monothiolated adduct have been used to show that sulfur insertion proceeds in a stepwise manner, with sulfur insertion occurring preferentially at the C6 centre. The associated kinetic isotope effects (KIE’s) for hydrogen atom abstraction from the C6 and C8 centres have been calculated and found to equal 2 and 15 respectively. The inhibition of LipA by methionine and AdoH, which are products from reactions involving radical SAM proteins, was investigated. Methionine offered no clear inhibition whilst AdoH had a slight inhibitionary effect (IC50 = 990 ± 83 ?M). When both methionine and AdoH were used together, a strong synergistic inhibition was present (IC50 = 327 ± 22 ?M). However, when an enzyme (Pfs) which cleaves the glycosidic bond in AdoH was added to the reaction, this inhibition was removed and a 1.4 fold increase in activity was observed.The ability of LipA to accept larger substrates was also tested using a nonanoyl peptide analogue. LCMS analysis of these reactions identified that as well as the expected single and double sulfur inserted products there were two further unexpected products formed in the reaction mixture. Proton NMR characterized these as a trans-alkene and a thietane. Mechanisms for their formations have been proposed.<br/
Is scuba sampling a relevant method to study microhabitat in lakes? Examples and comparisons for three European species
No full textWe compared fish microhabitat use patterns in the littoral zone of a lake using a new direct method (i.e. Point Abundance Sampling by Scuba, PASS) and the widely used Point Abundance Sampling by Electrofishing technique (PASE). We collected microhabitat data for age 0+ roach (Rutilus rutilus L.), perch (Perca fluviatilis L.), and pike (Esox lucius L.). The two methods yelded different results for fish assemblage structure and microhabitat patterns. Using PASE, fish were mainly found in "shelter habitats" such as shallow waters and dense vegetation. It is likely that this behaviour is caused by the disturbance of the observer stamping around. Using PASS, fish escapement behaviour was rarely observed. Therefore, we concluded that this direct and non-destructive sampling technique is able to provide an accurate microhabitat estimation of a fish community and is assumed to be more suitable than PASE for fish habitat studies
Strontium isotopes as an indicator of the source of calcium for regolith carbonates
No full textRobert C. Dart, Paul D. Wittwer, Karin M. Barovich, David Chittleborough & S.M. Hil
Figure 10. Pocillopora verrucosa. A in With eyes wide open: a revision of species within and closely related to the Pocillopora damicornis species complex (Scleractinia; Pocilloporidae) using morphology and genetics
No full textFigure 10. Pocillopora verrucosa. A, in situ. B, skeleton of branch. C and D, scanning electron micrographs (photos: Paul Muir). E, Madrepora damicornis Esper, 1791. F, specimen identified by Ehrenberg (1834) as P. verrucosa. G, sorallum of neotype (side view). H and I, scanning electron micrographs of neotype (MTQ-G65923).Published as part of Schmidt-Roach, Sebastian, Miller, Karen J., Lundgren, Petra & Andreakis, Nikos, 2014, With eyes wide open: a revision of species within and closely related to the Pocillopora damicornis species complex (Scleractinia; Pocilloporidae) using morphology and genetics, pp. 1-33 in Zoological Journal of the Linnean Society 170 (1) on page 22, DOI: 10.1111/zoj.12092, http://zenodo.org/record/530055
A green tea extract lowers plasma cholesterol by inhibiting cholesterol synthesis and upregulating the LDL receptor in the cholesterol-fed rabbit
No full textCopyright © 2006 Elsevier Ireland Ltd All rights reserved.Christina A. Bursill, Mavis Abbey and Paul D. Roachhttp://www.elsevier.com/wps/find/journaldescription.cws_home/522790/description#descriptio
Comparison of ovarian cycles of Hungarian riverine fish species representing different spawning strategies
No full textInvestigations on the ovarian cycle of fish species that inhabit Hungarian rivers are necessitated by both environmental and economic reasons. The objective of our research was to explore new fundamental knowledge concerning the ovarian cycle of the white bream (Blicca bjoerkna, Linnaeus, 1758), barbel (Barbus barbus, Linnaeus, 1758), orfe (Leuciscus idus, Linnaeus, 1758) and nase (Chondrostoma nasus, Linnaeus, 1758). Histological investigation of ovaries and determination of proportions of oocytes in different stages of development is an appropriate method for the description of spawning characteristics of these species. Our results show that the GSI value for all four investigated species starts to increase at the end of summer and reaches its maximum before spawning. In the barbel and white bream, the presence of oocytes in the stage of cortical alveoli and the heterogeneous size of oocytes in the stage of vitellogenesis in the pre-spawning period indicate that barbel and white bream are multiple spawners. In contrast, in the orfe and nase, the absence of oocytes in the stage of cortical alveoli and the homogeneous size of cells in the stage of vitellogenesis indicate that orfe and nase are single spawners
Inhibition of low-density lipoprotein oxidation and up-regulation of low-density lipoprotein receptor in HepG2 cells by tropical plant extracts
No full textTwelve edible plant extracts rich in polyphenols were screened for their potential to inhibit oxidation of low-density lipoprotein (LDL) in vitro and to modulate LDL receptor (LDLr) activity in cultured HepG2 cells. The antioxidant activity (inhibition of LDL oxidation) was determined by measuring the formation of conjugated dienes (lag time) and thiobarbituric acid reagent substances (TBARS). Betel leaf (94%), cashew shoot (63%), Japanese mint (52%), semambu leaf (50%), palm frond (41%), sweet potato shoot, chilli fruit, papaya shoot, roselle calyx, and maman showed significantly increased lag time (>55 min, P < 0.05) and inhibition of TBARS formation (P < 0.05) compared to control. LDLr was significantly up-regulated (P < 0.05) by Japanese mint (67%), semambu (51%), cashew (50%), and noni (49%). Except for noni and betel leaf, most plant extracts studied demonstrated a positive association between antioxidant activity and the ability to up-regulate LDL receptor. Findings suggest that reported protective actions of plant polyphenols on lipoprotein metabolism might be exerted at different biochemical mechanisms.Mohd. Nizar Salleh, Irine Runnie, Paul D. Roach, Suhaila Mohamed and Mahinda Y. Abeywarden
Figure 8. Pocillopora acuta. A in With eyes wide open: a revision of species within and closely related to the Pocillopora damicornis species complex (Scleractinia; Pocilloporidae) using morphology and genetics
No full textFigure 8. Pocillopora acuta. A, in situ appearance. B, skeleton of specimen. C and D, scanning electron micrographs of specimen (photos: Paul Muir). E, side view of corallum of holotype of Pocillopora acuta Lamarck, 1816 (photo: Michel Pichon). F, drawing by Esper (1791). G, P. acuta morph in situ. H, holotype of Pocillopora apiculata Ehrenberg, 1834. I, skeleton of compact morphology of P. acuta (MTQ-G66112).Published as part of Schmidt-Roach, Sebastian, Miller, Karen J., Lundgren, Petra & Andreakis, Nikos, 2014, With eyes wide open: a revision of species within and closely related to the Pocillopora damicornis species complex (Scleractinia; Pocilloporidae) using morphology and genetics, pp. 1-33 in Zoological Journal of the Linnean Society 170 (1) on page 18, DOI: 10.1111/zoj.12092, http://zenodo.org/record/530055
Remotely triggered scaffolds for controlled release of pharmaceuticals
No full textFe3O4-Au hybrid nanoparticles (HNPs) have shown increasing potential for biomedical applications such as image guided stimuli responsive drug delivery. Incorporation of the unique properties of HNPs into thermally responsive scaffolds holds great potential for future biomedical applications. Here we successfully fabricated smart scaffolds based on thermo-responsive poly(N-isopropylacrylamide) (pNiPAM). Nanoparticles providing localized trigger of heating when irradiated with a short laser burst were found to give rise to remote control of bulk polymer shrinkage. Gold-coated iron oxide nanoparticles were synthesized using wet chemical precipitation methods followed by electrochemical coating. After subsequent functionalization of particles with allyl methyl sulfide, mercaptodecane, cysteamine and poly(ethylene glycol) thiol to enhance stability, detailed biological safety was determined using live/dead staining and cell membrane integrity studies through lactate dehydrogenase (LDH) quantification. The PEG coated HNPs did not show significant cytotoxic effect or adverse cellular response on exposure to 7F2 cells (p < 0.05) and were carried forward for scaffold incorporation. The pNiPAM-HNP composite scaffolds were investigated for their potential as thermally triggered systems using a Q-switched Nd:YAG laser. These studies show that incorporation of HNPs resulted in scaffold deformation after very short irradiation times (seconds) due to internal structural heating. Our data highlights the potential of these hybrid-scaffold constructs for exploitation in drug delivery, using methylene blue as a model drug being released during remote structural change of the scaffold
Temporal rate is not a distinct perceptual metric.
No full textYesSensory adaptation experiments have revealed the existence of ‘rate after-effects’ - adapting to a relatively fast rate makes an intermediate test rate feel slow, and adapting to a slow rate makes the same moderate test rate feel fast. The present work aims to deconstruct the concept of rate and clarify how exactly the brain processes a regular sequence of sensory signals. We ask whether rate forms a distinct perceptual metric, or whether it is simply the perceptual aggregate of the intervals between its component signals. Subjects were exposed to auditory or visual temporal rates (a ‘slow’ rate of 1.5 Hz and a ‘fast’ rate of 6 Hz), before being tested with single unfilled intervals of varying durations. Results show adapting to a given rate strongly influences the perceived duration of a single empty interval. This effect is robust across both interval reproduction and duration discrimination judgments. These findings challenge our understanding of rate perception. Specifically, they suggest that contrary to some previous assertions, the perception of sequence rate is strongly influenced by the perception of the sequence’s component duration intervals.This work was supported by a Wellcome Trust [WT097387] grant to NW
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