Transglycosylation by Glycoside Hydrolases - Production and modification of alkyl glycosides

To enable the transition to a green, bio-based economy, an extensive enzymatic toolbox competitive to traditional chemical procedures is needed. One strong area for enzymes is carbohydrate chemistry, due to the over-functionalized nature of carbohydrates, difficult to handle in traditional chemistry. Glycosylation can be catalyzed by four main classes of enzymes, glycosyltransferases, glycoside phosphorylases, transglycosylases and glycoside hydrolases. For industrial implementation, transglycosylases are ideal catalysts that do not need the expensive activated donors associated with glycoside phosphorylases and glycosyltransferases. In addition, they completely lack the hydrolytic activity intrinsic in the closely related glycoside hydrolases. Unfortunately, very few transglycosylases with limited substrate specificities exist in nature, while a wide abundance of glycoside hydrolases are available. To expand the enzymatic toolbox for synthetic chemists it would be favorable to convert glycoside hydrolases into transglycosylases, by limiting their hydrolytic activity. This dissertation investigates the transglycosylation activity of glycoside hydrolases with synthesis and modification of alkyl glycosides, a widely applicable type of surfactants, as model reactions. Reduced hydrolysis for β-glycosidases from the thermophilic Thermotoga neapolitana was achieved through protein engineering, limiting water content and increasing pH. Complete elimination of the hydrolytic activity with maintained transglycosylation was achieved for synthesis of hexyl-β-D-glucoside and the factors resulting in the success are discussed. In addition, extension of the glycosidic part of alkyl glycosides through the coupling activity of cyclodextrin glucanotransferases is explored. An enzyme kinetics study was undertaken to deduce the optimal reaction conditions to promote coupling for a commercial enzyme. Moreover, a novel cyclodextrin glucanotransferase from Carboxydocella species was characterized, shown to have good coupling activity with γ-cyclodextrins as donor. This previously poorly studied donor can be used to extend the range of alkyl glycosides that can be produced and thereby the number of applications available

GLORIA Slope Approach - Monitoring Plant Community Changes in Mountain Ecosystems

The research described in this presentation is part of the Global Observation Research Initiative in Alpine Environments (GLORIA) whose purpose is to establish and maintain a global, long-term observation network in alpine environments. Despite changes in mountaintop-vegetation due to recent climate change being observed throughout the world, trends are not consistent. Moreover, as plant communities can be impacted by several different factors, it is important to be able to separate what is due to climate change and what is due to e.g. changes in grazing pressure (see additional file below)

"Railroad of Death": History and Archaeology of the German-built Second World War Hyrynsalmi-Kuusamo Railway 1942-1944

During the Second World War the frontal responsibility of northern Finland was held by German troops, who carried out large building projects to enhance the poor infrastructure of this peripheral region. This paper focuses on one of the biggest infrastructure projects performed by the Wehrmacht and Organisation Todt in Finland during the Second World War. The Hyrynsalmi-Kuusamo railway was to be built through a challenging landscape, by people who constantly overestimated their own abilities, and at the great expense and suffering of the workers who were mostly prisoners-of-war and forced labourers. Besides their own contemporary memories and experiences from this event, this construction project and its physical traces live in the local memories and have become part of the transgenerational heritage and remembrance of the war years. Using the wartime construction of the track as a starting point, this study goes on to map the heritage value, archaeological potential, and the state of research related to this German wartime project.Peer reviewe

Système politique et mobilité sociale

L'analyse des processus de mobilité sociale mobilise l'intérêt des sociologues depuis une trentaine d'années ; pourtant ni ce terme ni les concepts auxquels il fait appel ne font l'objet d'un consensus en sociologie. Le débat qui s'est développé autour de ce problème semble s'ordonner selon deux axes. D'une part, des discussions de type technique, de l'autre des oppositions plus radicales de nature théorique ou épistémologique. Le premier plan concerne tous les problèmes liés à la constitution et à l'interprétation des indicateurs de mobilité sociale : définition de critères permettant de constituer les classes ou groupes sociaux, mesure du flux de mobilité, problèmes liés à l'existence d'une mobilité structurelle, etc. Le second axe, d'une nature différente, met en question la légitimité du concept de mobilité sociale et, par conséquent, l'utilité de ce type de recherche quelles qu'en soient par ailleurs les modalités techniques (...)

Preparation of two glycoside hydrolases for use in micro-aqueous media

Enzymatic synthesis of alkyl glycosides using glycoside hydrolases is well studied, but has yet to reach industrial scale, primarily due to limited yields. Reduced water content should increase yields by limiting the unwanted hydrolytic side reaction. However, previous studies have shown that a reduction in water content surprisingly favors hydrolysis over transglycosylation. In addition, glycoside hydrolases normally require a high degree of hydration to function efficiently. This study compares six enzyme preparation methods to improve resilience and activity of two glycoside hydrolases from Thermotoga neapolitana (TnBgl3B and TnBgl1A) in micro-aqueous hexanol. Indeed, when adsorbed onto Accurel MP-1000 both enzymes increasingly favored transglycosylation over hydrolysis at low hydration, in contrast to freeze-dried or untreated enzyme. Additionally, they displayed 17–70× higher reaction rates compared to freeze-dried enzyme at low water activity, while displaying comparable or lower activity for fully hydrated systems. These results provide valuable information for use of enzymes under micro-aqueous conditions and build toward utilizing the full synthetic potential of glycoside hydrolases

Encountering/thinking mosquitos

The essay maps and reflects on some dimensions of human-mosquito interaction in the context of the Arctic and inspired by fieldwork in Finnish Lapland. Rather than developing any particular argument, we seek to document this thinking mosquito as a collection of glimpses, fragments and musings. This impressionistic approach was inspired by conversations among the authors and with environmental humanities scholarship about the roles non-humans play in human worlds, and about how one might engage with mosquitos in thinking about scientific fieldwork, about everyday life in various environments, and about the Arctic more generally. The essay does not provide answers but rather questions, hoping as it does to offer some insights into the complexity of issues that connect mosquito worlds to human worlds. As a mirror to these reflections, we dialogue with excerpts from our own creative written thoughts from the field and from the diaries of German soldiers based in Lapland during the Second World War.Peer reviewe

Detecting change points in remote sensing time series

We analyse methods for detecting change points in optical remote sensing lake drainage time series. Change points are points in a data set where the statistical properties of the data change. The data that we look at represent drained lakes in the Arctic hemisphere. It is generally noisy, with observations missing due to di!cult weather conditions. We evaluate a partitioning algorithm, with five di↵erent approaches to model the data, based on least-squares regression and an assumption of normally distributed measurement errors. We also evaluate two computer programs called DBEST and TIMESAT and a MATLAB function called findchangepts(). We find that TIMESAT, DBEST and the MATLAB function are not relevant for our purposes. We also find that the partitioning algorithm that models the data as normally distributed around a piecewise constant function, is best suited for finding change points in our data