Generation of aurachin derivatives by whole-cell biotransformation and evaluation of their antiprotozoal properties

The natural product aurachin D is a farnesylated quinolone alkaloid, which is known to possess activity against the causative agent of malaria, Plasmodium spp. In this study, we show that aurachin D inhibits other parasitic protozoa as well. While aurachin D had only a modest effect on Trypanosoma brucei rhodesiense, two other trypanosomatids, T. cruzi and Leishmania donovani, were killed at low micromolar and nanomolar concentrations, respectively, in an in vitro assay. The determined IC50 values of aurachin D were even lower than those of the reference drugs benznidazole and miltefosine. Due to these promising results, we set out to explore the impact of structural modifications on the bioactivity of this natural product. In order to generate aurachin D derivatives with varying substituents at the C-2, C-6 and C-7 position of the quinolone ring system, we resorted to whole-cell biotransformation using a recombinant Escherichia coli strain capable of aurachin-type prenylations. Quinolone precursor molecules featuring methyl, methoxy and halogen groups were fed to this E. coli strain, which converted the substrates into the desired analogs. None of the generated derivatives exhibited improved antiprotozoal properties in comparison to aurachin D. Obviously, the naturally occurring aurachin D features already a privileged structure, especially for the inhibition of the causative agent of visceral leishmaniasis

Climate change adaptation as a development challenge to small Island states: A case study from the Solomon Islands

© 2020 Elsevier Ltd Small Island Developing States (SIDS) are known to be particularly vulnerable to climate change, which poses a challenge to their economic and social development. This vulnerability is expressed in several ways, from exposure to sea level rises, to salt intrusion, and extensive droughts in some areas. Despite this rather negative trend, there are examples of initiatives where the vulnerability of SIDS can be reduced, and their resilience may be increased. Based on the paucity of the literature on concrete examples of successful climate change adaptation initiatives on SIDS, this paper presents an overview of pertinent challenges faced, and introduces two case studies from the Solomon Islands, which illustrate how much can be achieved by systematically pursuing adaptation strategies. The lessons learned from these case studies are outlined and some useful insights are provided, which may help SIDS to better foster the development opportunities with climate change adaptation offers to them

Quark Model Estimates of the Structure of the Meson-N-N*(1535,1/2-) Transition Vertices

We address an actual problem of baryon-resonance dominated meson-exchange processes in the low GeV regime, i.e. the phase and the structure of meson-NN* transition vertices. Our starting point is a quark-diquark model for the baryons (obeying approximate covariance; the mesons are kept as elementary objects), together with the relative phases for the NN vertices, as determined from low energy NN scattering. From the explicit representation of the N and N* baryons, we exemplify the derivation of the coupling constants and form factors of the NN*(1535,1/2-)transition vertices for pseudo-scalar, scalar and vector mesons.Comment: 17 pages, 5 figures, 1 tabl

Kaon Energies in Dense Matter

We discuss the role of kaon-nucleon and nucleon-nucleon correlations in kaon condensation in dense matter. Correlations raise the threshold density for kaon condensation, possibly to densities higher than those encountered in stable neutron stars.Comment: RevTeX, 11 pages, 2 PostScript figures; manuscript also available, in PostScript form, at http://www.nordita.dk/locinfo/preprints.htm

Analyses and localization of pectin-like carbohydrates in cell wall and mucilage of the green alga Netrium digitus

The unicellular, simply shaped desmid Netrium digitus inhabiting acid bog ponds grows in two phases. Prior to division, the cell elongates at its central zone, whereas in a second phase, polar tip growth occurs. Electron microscopy demonstrates that Netrium is surrounded by a morphologically homogeneous cell wall, which lacks pores. Immunocytochemical and biochemical analyses give insight into physical wall properties and, thus, into adaptation to the extreme environment. The monoclonal antibodies JIM5 and JIM7 directed against pectic epitopes with different degrees of esterification label preferentially growing wall zones in Netrium. In contrast, 2F4 marks the cell wall only after experimental de-esterification. Electron energy loss spectroscopy reveals Ca-binding capacities of pectins and gives indirect evidence for the degree of their esterification. An antibody raised against Netrium mucilage is not only specific to mucilage but also recognizes wall components in transmission electron microscopy and dot blots. These results indicate a smooth transition between mucilage and the cell wall in Netrium

The impacts of the early outset of the COVID-19 pandemic on climate change research: implications for policy-making

Since January 2020, the COVID-19 pandemic has dominated the media and exercises pressure on governments worldwide. Apart from its effects on economies, education systems and societies, the pandemic has also influenced climate change research. This paper examines the extent to which COVID-19 has influenced climate change research worldwide during the first wave at the beginning of 2020 and how it is perceived to exploit it in the future. This study utilised an international survey involving those dedicated to climate change science and management research from Academia, Government, NGOs, and international agencies in 83 countries. The analysis of responses encompasses four independent variables: Institutions, Regions, Scientific Areas, and the level of economic development represented by the Human Development Index (HDI). Results show that: (1) COVID-19 modified the way the surveyed researchers work, (2) there are indicators that COVID-19 has already influenced the direction of climate change and adaptation policy implementation, and (3) respondents perceived (explicitly concerning the COVID-19 lockdowns of March-April 2020), that the pandemic has drawn attention away from climate policy. COVID- 19 has influenced the agenda of climate change research for more than half of the respondents and is likely to continue in the future, suggesting that the impacts on their research will still be felt for many years. The paper concludes by outlining critical implications for policy-making

Impacts of climate change to African indigenous communities and examples of adaptation responses

Climate change negatively impacts the livelihoods of indigenous communities across the world, including those located on the African continent. This Comment reports on how five African indigenous communities have been impacted by climate change and the adopted adaptation mechanisms

What difference does Euro membership make to stabilization? The political economy of international monetary systems revisited

For many political economists, the loss of monetary sovereignty is the major reason why the Southern periphery fared so badly in the Euro area crisis. Monetary sovereignty here means the ability of the central bank to devalue the exchange rate or to buy government debt by printing the domestic currency. We explore this diagnosis by comparing three countries - Hungary, Latvia and Greece – that received considerable amounts of external assistance under different monetary regimes. The evidence does not suggest that monetary sovereignty helped Hungary and Latvia to stabilize their economies. Rather, cooperation and external assistance made foreign banks share in the costs of stabilization. By contrast, the provision of liquidity by the ECB inadvertently facilitated the reduction of foreign banks’ exposure to Greece which left the Greek sovereign even more exposed. By viewing the Euro area as a monetary system rather than an incomplete state, we see that what is needed for Euro area stabilization is cooperation over banking union, rather than a fully-fledged federal budget