Controlled enzymatic removal of damaging casein layers on medieval wall paintings

A new, gentle enzymatic method was developed for a controlled removal of casein layers from medieval wall paintings. These casein layers were applied over the last 60 years on wall paintings in order to decrease substantial damage due to a peeling off of the frescoes from the roughcast surface due to environmental effects. However, due to the aging of the casein layers (at 40-50 years), a more drastic peeling occurred and the danger of total destruction of the wall paintings is severe. Thus, screening was performed to find the most suitable enzyme for casein digestion. Alcalase 2.5 DX L was the most appropriate enzyme for an effective proteolysis reaction. The enzyme was immobilized on functionalized cellulose membrane. A membrane pad system with immobilized enzymes was developed which could be pressed on the casein layers on the wall painting. A controlled removal of the casein layers by proteolytic digestion was observed and it was possible to continuously wash off the hydrolyzed casein fragments from the wall painting surface by an aqueous carbonate buffer flowing through the membrane pad. The removal and the digestion was monitored by reverse HPLC. Additionally, an on-line monitoring system was set up in order to continuously follow the casein layer removal and the digestion procedure directly on the wall painting. This technique is based on noninvasive 2D-fluorescence monitoring. Optical fiber systems were used to continuously monitor the fluorescence intensity of casein-bound tryptophan. The off-line data were verified with the on-line 2D-fluorescence data. Based on the scientific result an appropriate technique for the controlled enzymatic removal of damaging casein layers on the surface of medieval wall paintings using immobilized enzyme is now available. It is now applied to remove such casein layers from medieval wall paintings in the Allerheiligen-Kapelle Cloister, Wienhausen, Germany, and the St. Alexander Kirche, Wildeshausen, Germany.     

Searching for allelopathic effects of submerged macrophytes on phytoplankton—state of the art and open questions

Allelopathy, here defined as biochemical interactions between aquatic primary producers, has always been intriguing as a process explaining the dominance of certain plant or algal species over others. Negative chemical interference has been invoked as one of the steering mechanisms behind mutual dominance of either submerged macrophytes or phytoplankton in shallow eutrophic lakes. Yet, despite much effort, convincing evidence for allelopathic interactions in situ is still missing. Also, laboratory approaches often lack reality. Inspired by a series of talks at the Shallow Lakes 2005 meeting in Dalfsen, the Netherlands, we argue that there is circumstantial but strong evidence that allelopathic interference between submerged macrophytes and phytoplankton may indeed exist in aquatic ecosystems despite the problems associated with research in this field. We first discuss experimental approaches combining laboratory and field studies, based on examples presented at this meeting. We then discuss the impact of nutrient status of both producing and target organism and biotic factors such as herbivory or pathogens that might affect allelopathy. Further topics are the potential seasonality of effects and the species-specificity of certain allelochemicals. We conclude with some thoughts why a final proof for allelopathy in situ might remain difficult or even inaccessible in some cases, and why we nevertheless should not abandon this idea.     

Metabolic syndrome is associated to high-sensitivity cardiac troponin T elevation

Introduction: Metabolic syndrome (MetS) and high-sensitivity cardiac troponin T (hs-TnT) are associated with higher risk for cardiovascular diseases (CVD). Our aim was to assess the relation between hs-TnT elevation and MetS in a general population sample.

Materials and methods: Individuals participating in an annual health survey program between 2010 and 2016 were included in the study. Blood samples including hs-TnT levels were collected. The study population was divided into three groups based on hs-TnT levels – undetectable (<5?ng/L), intermediate (5–14?ng/L) and elevated (>14?ng/L).

Results: A total of 5994 subjects were included in the study, the mean age was 48.5 and 4336 (72%) were males. Compared with subjects with undetectable hs-TnT the prevalence of MetS was higher in those with detectable and elevated levels – 392 (10%) vs. 270 (15%) and 51 (33%), respectively (p?<?0.001). In a multivariate model adjusted for age, gender and multiple co-morbidities, the number of MetS components and presence of MetS were significantly associated with an increased risk for detectable hs-TnT levels (OR?=?1.02 {for each component}; 95% CI [1.00–1.05], p?=?0.04) and (OR?=?1.13; 95% CI [1.07–1.2], p?<?0.001) respectively. Only the waist, glucose and hypertension components of the MetS were significantly associated with elevated troponin.

Conclusions: The MetS and its distinct components have a cumulative impact on hs-TnT levels in apparently healthy subjects.     

Cycles and the Qualitative Evolution of Chemical Systems

Cycles are abundant in most kinds of networks, especially in biological ones. Here, we investigate their role in the evolution of a chemical reaction system from one self-sustaining composition of molecular species to another and their influence on the stability of these compositions. While it is accepted that, from a topological standpoint, they enhance network robustness, the consequence of cycles to the dynamics are not well understood. In a former study, we developed a necessary criterion for the existence of a fixed point, which is purely based on topological properties of the network. The structures of interest we identified were a generalization of closed autocatalytic sets, called chemical organizations. Here, we show that the existence of these chemical organizations and therefore steady states is linked to the existence of cycles. Importantly, we provide a criterion for a qualitative transition, namely a transition from one self-sustaining set of molecular species to another via the introduction of a cycle. Because results purely based on topology do not yield sufficient conditions for dynamic properties, e.g. stability, other tools must be employed, such as analysis via ordinary differential equations. Hence, we study a special case, namely a particular type of reflexive autocatalytic network. Applications for this can be found in nature, and we give a detailed account of the mitotic spindle assembly and spindle position checkpoints. From our analysis, we conclude that the positive feedback provided by these networks'' cycles ensures the existence of a stable positive fixed point. Additionally, we use a genome-scale network model of the Escherichia coli sugar metabolism to illustrate our findings. In summary, our results suggest that the qualitative evolution of chemical systems requires the addition and elimination of cycles.     

Introduced weed richness across altitudinal gradients in Hawai’i: humps,humans and water-energy dynamics

Native species richness commonly declines with increasing altitude, but patterns of introduced species richness across altitudinal gradients have been less frequently studied. We surveyed introduced roadside weeds along altitudinal transects ranging from 30 to 4,100 m in Hawai’i, with the objectives of (1) testing the hypothesis that a mass effect due to mixing of tropical and temperate species at mid-elevation promotes a hump-shaped pattern of introduced species richness with altitude, and (2) testing the potential roles of anthropogenic activity, energy (temperature) and water-energy dynamics (productivity-diversity hypothesis) in determining introduced weed richness. A total of 178 introduced weeds were recorded. Introduced weed richness does not decline monotonically with altitude. Rather, mixing of tropical and temperate species helps to maintain high mean richness up to 2,000 m, suggesting a mass effect, but without a distinct richness peak. Patchy occurrence of a transformer species, Pennisetum clandestinum, introduced high variance in richness at mid-elevations. General linear models considering estimated actual evapotranspiration (AET, a measure of energy-water dynamics) together with an index of human activity (distance from urban area or length of major roads) accounted for more variance in introduced weed richness than models with energy alone (temperature) and human activity. Native Hawaiian species richness along roadsides was also weakly correlated with AET but negatively associated with human activity. Our observed association between introduced species richness and AET mirrors patterns reported for native species richness around the world, indicating that AET-richness patterns can develop on a short time scale (on the order of 100 years). To test the generality of introduced weed richness patterns, we tried using the Hawai’i island model to predict weed richness on the neighboring island of Maui. Although weed richness on Maui was under-predicted, the same predictors (human activity and AET) were important on Maui. Scaling for differences in regional human population density or economic activity (both higher on Maui) may allow more accurate and transferable quantitative predictions of introduced weed richness patterns.     

Comparative analysis of plasma metabolomics response to metabolic challenge tests in healthy subjects and influence of the FTO obesity risk allele

The measurement of metabolites during intravenous or nutritional challenges may improve the identification of novel metabolic signatures which are not detectable in the fasting state. Here, we comprehensively characterized the plasma metabolomics response to five defined challenge tests and explored their use to identify interactions with the FTO rs9939609 obesity risk genotype. Fifty-six non-diabetic male participants of the KORA S4/F4 cohort, including 25 homozygous carriers of the FTO risk allele (AA genotype) and 31 carriers of the TT genotype were recruited. Challenges comprised an oral glucose tolerance test, a standardized high-fat high-carbohydrate meal and a lipid tolerance test, as well as an intravenous glucose tolerance test and a euglycemic hyperinsulinemic clamp. Blood was sampled for biochemical and metabolomics measurement before and during the challenges. Plasma samples were analyzed using a mass spectrometry-based metabolomics approach targeting 163 metabolites. Linear mixed-effects models and cluster analysis were performed. In both genotype groups, we observed significant challenge-induced changes for all major metabolite classes (amino acids, hexose, acylcarnitines, phosphatidylcholines, lysophosphatidylcholines and sphingomyelins, with corrected p-values ranging from 0.05 to 6.7E?37), which clustered in five distinct metabolic response profiles. Our data contribute to the understanding of plasma metabolomics response to diverse metabolic challenges, including previously unreported metabolite changes in response to intravenous challenges. The FTO genotype had only minor effects on the metabolite fluxes after standardized metabolic challenges.