Functional studies on oligotropha carboxidovorans molybdenum–copper CO dehydrogenase produced in escherichia coli

The Mo/Cu-dependent CO dehydrogenase (CODH) from Oligotropha carboxidovorans is an enzyme that is able to catalyze both the oxidation of CO to CO2 and the oxidation of H2 to protons and electrons. Despite the close to atomic resolution structure (1.1 Å), significant uncertainties have remained with regard to the reaction mechanism of substrate oxidation at the unique Mo/Cu center, as well as the nature of intermediates formed during the catalytic cycle. So far, the investigation of the role of amino acids at the active site was hampered by the lack of a suitable expression system that allowed for detailed site-directed mutagenesis studies at the active site. Here, we report on the establishment of a functional heterologous expression system of O. carboxidovorans CODH in Escherichia coli. We characterize the purified enzyme in detail by a combination of kinetic and spectroscopic studies and show that it was purified in a form with characteristics comparable to those of the native enzyme purified from O. carboxidovorans. With this expression system in hand, we were for the first time able to generate active-site variants of this enzyme. Our work presents the basis for more detailed studies of the reaction mechanism for CO and H2 oxidation of Mo/Cu-dependent CODHs in the future

Investors care about risk, but can't cope with volatility

Following the classical portfolio theory all an investor has to do for an optimal investment is to determine his risk attitude. This allows him to find his point on the capital market line by combining a risk-free asset with the market portfolio. We investigate the following research questions in an experimental set-up: Do private investors see a relationship between risk attitude and the amount invested risky at all and do they adjust their investments if provided with different risk levels of the risky asset? To answer these questions we ask subjects in a between subject design to allocate a certain amount between a risky and a risk-free asset. Risky assets differ between conditions, but can be transformed into each other by combining them with the risk-free asset. We find that mainly investors risk attitude, but also their risk perception, and the investment horizon are strong predictors for risk taking. Indeed, investors do not appear to be naïve, but they do something sensitive. Nevertheless, we observe a strong framing effect: investors choose almost the same allocation to the risky asset independently of changes in its risk-return profile thus ending up with significantly different volatilities. Feedback does not mitigate the framing effect. The effect is somewhat smaller for investors with a high financial literacy. Overall, people seem to use two mental accounts, one for the risk-free and one for the risky investment with the risk attitude determining the percentage allocation to the risky asset and not the chosen portfolio volatility

The mother and her ancestral face. A commentary on Iatmul iconography

Visually effective symbolization in Iatmul society is reviewed, starting from observations by Bernard Juillerat on the role of the mother in real as well as in symbolic relationships. Ceremonial acts of women and men in the context of naven rituals, and iconological representation anchored in initiatory knowledge are shown to be linked. Performing renders knowledge, services, material objects such as valuables or masks, i.e. cultural entities with a symbolic value, openly accessible for all parties concerned. They become the issue of exchange at specific occasions, enhancing the gendered roles of mother or elder sibling and their complementing actors, child or younger sibling.L’expression visuelle des valeurs symboliques dans la société iatmul est reconsidérée en partant d’observations de Bernard Juillerat sur le rôle de la mère. Sont mis en évidence les  liens entre la façon d’agir, les rôles réels et symboliques de mère, oncle maternel et neveu, aîné et cadet, à travers les rituels naven et les représentations ancestrales matérialisées par des œuvres fondées dans le savoir initiatique des hommes. Les rites publics rendent accessibles à tous les savoir-faire, les prestations ainsi que des objets spécifiques y compris des masques, c’est-à-dire des entités culturelles à valeur symbolique. Leur présentation généralise l’importance des acteurs et de leurs partenaires complémentaires