Photosynthesis and calcification in the calcifying algae Halimeda discoidea studied with microsensors

With microsensors, we measured the steady‐state microprofiles of O2, pH and Ca2+ on the topside of young segments of Halimeda discoidea, as well as the surface dynamics upon light–dark shifts. The effect of several inhibitors was studied. The steady‐state measurements showed that under high light intensity, calcium and protons were taken up, while O2 was produced. In the dark, O2 was consumed, the pH decreased to below seawater level and Ca2+ uptake was reduced to 50%. At low light intensity (12 mmol photons m‐2 s‐1), Ca2+ efflux was observed. Upon light–dark shifts, a complicated pattern of both the pH and calcium surface dynamics was observed. Illumination caused an initial pH decrease, followed by a gradual pH increase: this indicated that the surface pH of H. discoidea is determined by more than one light‐induced process. When photosynthesis was inhibited by dichlorophenyl dimethyl urea (DCMU), a strong acidification was observed upon illumination. The nature and physiological function of this putative pump is not known. The calcium dynamics followed all pH dynamics closely, both in the presence and absence of DCMU. The Ca‐channel blockers verapamil and nifedipine had no effect on the Ca2+ dynamics and steady‐state profiles. Thus, in H. discoidea, calcification is not regulated by the alga, but is a consequence of pH increase during photosynthesis. Acetazolamide had no effect on photosynthesis, whereas ethoxyzolamide inhibited photosynthesis at higher light intensities. Therefore, all carbonic anhydrase activity is intracellular. Carbonic anhydrase is required to alleviate the CO2 limitation. Calcification cannot supply sufficient protons and CO2 to sustain photosynthesis

Demoprints hands-on exercise: aide memoire

Handout for hands-on training exercise on the use of Demoprints http://demoprints.eprints.org For use during Western Cape Higher Education Libraries Interest Group (WCHELIG) Winter workshop, 14 June 2005, Bellville (Cape Town), South Africa

Making the innovation case in Open Access scholarly communication

It seems almost unnecessary to have to elaborate additional reasons for the adoption of Open Access scholarly communication (OA sc) as manifested through Open Access journals and self-archiving practices. To those active within the OA arena, the case has been convincingly made, and current arguments merely need to be disseminated beyond the Library and Information Science (LIS) sphere. However, it is my contention that a convincing argument for OA sc needs to be launched from the Science Policy perspective if any government mandated pro-OA policy changes are to be effected. This paper, then, is an attempt at taking the OA discussion beyond the LIS arena and into the realm of Science and Innovation Policy. Using Innovation Theory as its theoretical framework, it is argued that Open Access scholarly communication can only serve to bolster Innovation Systems, be they national, regional, or sectoral. The case of South Africa is taken as an illustrative example, though the case can and will be generalised to beyond the South African science system. Making the case for OA within the context of Innovation is also of strategic import, since government policymakers frequently heed the advice of Science- and Innovation Policy researchers

Making the innovation case in Open Access scholarly communication

It seems almost unnecessary to have to elaborate additional reasons for the adoption of Open Access scholarly communication (OA sc) as manifested through Open Access journals and self-archiving practices. To those active within the OA arena, the case has been convincingly made, and current arguments merely need to be disseminated beyond the Library and Information Science (LIS) sphere. However, it is my contention that a convincing argument for OA sc needs to be launched from the Science Policy perspective if any government mandated pro-OA policy changes are to be effected. This paper, then, is an attempt at taking the OA discussion beyond the LIS arena and into the realm of Science and Innovation Policy. Using Innovation Theory as its theoretical framework, it is argued that Open Access scholarly communication can only serve to bolster Innovation Systems, be they national, regional, or sectoral. The case of South Africa is taken as an illustrative example, though the case can and will be generalised to beyond the South African science system. Making the case for OA within the context of Innovation is also of strategic import, since government policymakers frequently heed the advice of Science- and Innovation Policy researchers

Demoprints hands-on exercise: aide memoire

Handout for hands-on training exercise on the use of Demoprints http://demoprints.eprints.org For use during Western Cape Higher Education Libraries Interest Group (WCHELIG) Winter workshop, 14 June 2005, Bellville (Cape Town), South Africa

Open Access in South Africa: progress report

As scientific actor on the African continent, South Africa has a role to play in promoting and facilitating the roll-out of Open Access (OA) scholarly communication practices, in southern Africa, in sub-Saharan Africa, and across the continent. A 2004 study revealed the progress made in the Open Access arena in South Africa, and the present talk, taking the 2004 study as its base, provides an update on and overview of the more recent South African OA initiatives

Open Access in South Africa: progress report

As scientific actor on the African continent, South Africa has a role to play in promoting and facilitating the roll-out of Open Access (OA) scholarly communication practices, in southern Africa, in sub-Saharan Africa, and across the continent. A 2004 study revealed the progress made in the Open Access arena in South Africa, and the present talk, taking the 2004 study as its base, provides an update on and overview of the more recent South African OA initiatives

Electrostatic Fields Stimulate Absorption of Small Neutral Molecules in Gradient Polyelectrolyte Brushes

Molecules can partition from a solution into a polymer coating, leading to a local enrichment. If one can control this enrichment via external stimuli, one can implement such coatings in novel separation technologies. Unfortunately, these coatings are often resource intensive as they require stimuli in the form changes of bulk solvent conditions such as acidity, temperature, or ionic strength. Electrically driven separation technology may provide an appealing alternative, as this will allow local, surface-bound stimuli instead of system-wide bulk stimuli to induce responsiveness. Therefore, we investigate via coarse grained molecular dynamics simulations the possibility of using coatings with charged moieties, specifically gradient polyelectrolyte brushes, to control the enrichment of the neutral target molecules near the surface with applied electric fields. We find that targets which interact more strongly with the brush show both more absorption and a larger modulation by electric fields. For the strongest interactions evaluated in this work, we obtained absorption changes of over 300 % between the collapsed and extended state of the coating.</p

Vv-AMP1, a ripening induced peptide from Vitis vinifera shows strong antifungal activity

Includes bibliography.Background: Latest research shows that small antimicrobial peptides play a role in the innate defense system of plants. These peptides typically contribute to preformed defense by developing protective barriers around germinating seeds or between different tissue layers within plant organs. The encoding genes could also be upregulated by abiotic and biotic stimuli during active defense processes. The peptides display a broad spectrum of antimicrobial activities. Their potent anti-pathogenic characteristics have ensured that they are promising targets in the medical and agricultural biotechnology sectors. Results: A berry specific cDNA sequence designated Vv-AMP1, Vitis vinifera antimicrobial peptide 1, was isolated from Vitis vinifera. Vv-AMP1 encodes for a 77 amino acid peptide that shows sequence homology to the family of plant defensins. Vv-AMP1 is expressed in a tissue specific, developmentally regulated manner, being only expressed in berry tissue at the onset of berry ripening and onwards. Treatment of leaf and berry tissue with biotic or abiotic factors did not lead to increased expression of Vv-AMP1 under the conditions tested. The predicted signal peptide of Vv-AMP1, fused to the green fluorescent protein (GFP), showed that the signal peptide allowed accumulation of its product in the apoplast. Vv-AMP1 peptide, produced in Escherichia coli, had a molecular mass of 5.495 kDa as determined by mass spectrometry. Recombinant Vv-AMP1 was extremely heat-stable and showed strong antifungal activity against a broad spectrum of plant pathogenic fungi, with very high levels of activity against the wilting disease causing pathogens Fusarium oxysporum and Verticillium dahliae. The Vv-AMP1 peptide did not induce morphological changes on the treated fungal hyphae, but instead strongly inhibited hyphal elongation. A propidium iodide uptake assay suggested that the inhibitory activity of Vv-AMP1 might be associated with altering the membrane permeability of the fungal membranes. Conclusion: A berry specific cDNA clone, Vv-AMP1, was isolated and characterized and shown to encode a plant defensin. Recombinant Vv-AMP1 displayed non-morphogenic antifungal activity against a broad spectrum of fungi, probably altering the membrane permeability of the fungal pathogens. The expression of this peptide is highly regulated in Vitis vinifera, hinting at an important defense role during berry-ripening.Peer reviewe