Factors Influencing the Adhesion of Microorganisms to Surfaces

Starvation, growth phase, and carbon source influenced bacterial cell surface hydrophobicity. Both the number and kind of microorganisms that colonized metal surfaces depended on the type of metal and the presence of an imposed electrical potential. No significant differences in attachment and growth of a pure culture were observed when metal surfaces were dipped in an exogenous energy source. The chemical composition of naturally occurring adsorbed organic films on metal surfaces was shown to be independent of surface composition and polarization.     

Development and validation of an analytical method for total amitraz in fruit and honey with quantification by gas chromatography-mass spectrometry

The EU maximum residue limit (MRL) definition for amitraz is 'the sum of amitraz plus all its metabolites containing the 2,4-aniline moiety, expressed as amitraz'. A rapid and sensitive method has been developed and validated in-house for the determination of total amitraz in pears, strawberries, oranges and honey. Samples were hydrolysed (under acidic followed by alkaline conditions) to convert amitraz to 2,4-dimethyaniline, which was then partitioned into 2,2,4-trimethylpentane prior to quantification by gas chromatography-mass spectrometry. The method was validated at 0.02 and 0.1 mg kg^-1 amitraz (well below MRL requirements) with a lowest calibrated level (LCL) for 2,4-dimethylaniline of 0.002 mg kg^-1 (equivalent to 0.0024 mg kg^-1 amitraz). A single partition step yielded recoveries of ∼60% (with % CV values in the range 3.3-8.2), which is satisfactory for screening purposes. A second partition increased recoveries by 10-20%, making the method suitable for the quantification of residues.     

Site‐specific and Spatially Controlled Addressability of a New Viral Nanobuilding Block: Sulfolobus islandicus Rod‐shaped Virus 2

Nanotechnology seeks to mimic what nature has achieved: self‐assembly at the nanometer scale. Viral nanoparticles (VNPs) provide natural examples of self‐assembled architectures with unique structural and chemical properties. Here, the utilization of an archaeal virus, Sulfolobus islandicus rod‐shaped virus 2 (SIRV2), as a template for site‐selective and spatially controlled bioconjugation is described. SIRV2 is a virus of a hyperthermophilic and acidophilic host, the archaeon S. islandicus growing optimally at 80 °C and pH 3, and is thus, by its nature, an extremely stable VNP. The stability of SIRV2 in different solvent/water mixtures is monitored, and it is found that in other, non‐natural harsh conditions the VNPs also remained intact. Further, the question of whether the particles offer attachment sites allowing for selective chemical modification and decoration with functional ligands using biotin as a probe is addressed. It is found that carboxylate‐, carbohydrate‐ and amine‐selective chemistries are applicable and various biotinylated SIRV2 formulations can be fabricated. Depending on the chemistry and hence attachment site used, the display of the biotin labels can be spatially controlled at the virus body and at the ends. Labeling studies also provide novel insights into the structural properties of SIRV2, indicating that the major coat protein (CP) forms the virus body while the minor CP is located in the tail fibers at the end of the particles. Overall, SIRV2 represents an extremely stable and structurally interesting VNP with the potential for novel nanobiotechnological applications.     

Molecular Mechanism of the Hydration of Candida antarctica Lipase B in the Gas Phase: Water Adsorption Isotherms and Molecular Dynamics Simulations

Hydration is a major determinant of activity and selectivity of enzymes in organic solvents or in gas phase. The molecular mechanism of the hydration of Candida antarctica lipase B (CALB) and its dependence on the thermodynamic activity of water (a_w) was studied by molecular dynamics simulations and compared to experimentally determined water sorption isotherms. Hydration occurred in two phases. At low water activity, single water molecules bound to specific water binding sites at the protein surface. As the water activity increased, water networks gradually developed. The number of protein‐bound water molecules increased linearly with a_w, until at a_w=0.5 a spanning water network was formed consisting of 311 water molecules, which covered the hydrophilic surface of CALB, with the exception of the hydrophobic substrate‐binding site. At higher water activity, the thickness of the hydration shell increased up to 10 Å close to a_w=1. Above a limit of 1600 protein‐bound water molecules the hydration shell becomes unstable and the formation of pure water droplets occurs in these oversaturated simulation conditions. While the structure and the overall flexibility of CALB was independent of the hydration state, the flexibility of individual loops was sensitive to hydration: some loops, such as those part of the substrate‐binding site, became more flexible, while other parts of the protein became more rigid upon hydration. However, the molecular mechanism of how flexibility is related to activity and selectivity is still elusive.     

Long-term human exposure to lead from different media and intake pathways

Lead (Pb) is well known as an environmental pollutant: it can accumulate in various media, so actual lead exposure reflects both historical and present contaminations. Two main challenges then emerge: obtaining updated information to gain an overall picture of the sources of exposure, and predicting the resulting internal body exposure levels and effects that occur under long-term exposure conditions. In this paper, a modeling approach is used to meet these challenges with reference to Danish exposure conditions. Levels of lead content in various media have been coupled with data for lead intake and absorption in the human body, for both children and adults. An age-dependent biokinetic model allows then for determination of the blood lead levels resulting from chronic exposure. The study shows that the actual intake of lead is up to 27% of the Provisional Tolerable Daily Intake (PTDI) for children and around 8% for adults. It is confirmed that the critical route of exposure is via ingestion, accounting for 99% of total lead intake, while inhalation contributes only to 1% of total lead intake. The resulting lead levels in the blood after 2 years of exposure to actual contamination conditions have been estimated as up to 2.2 μg/dl in children and almost 1 μg/dl in adults. Impacts from lead can occur even at such levels. The role of historical and present sources to lead in the environment is discussed, and, for specific child and adult exposure scenarios, external-internal concentration relationships for the direct linkage between lead in environmental media and resulting concentrations of lead in blood are then presented.     

Suppression of Water as a Nucleophile in Candida antarctica Lipase B Catalysis

A water tunnel in Candida antarctica lipase B that provides the active site with substrate water is hypothesized. A small, focused library created in order to prevent water from entering the active site through the tunnel was screened for increased transacylation over hydrolysis activity. A single mutant, S47L, in which the inner part of the tunnel was blocked, catalysed the transacylation of vinyl butyrate to 20 mM butanol 14 times faster than hydrolysis. The single mutant Q46A, which has a more open outer end of the tunnel, showed an increased hydrolysis rate and a decreased hydrolysis to transacylation ratio compared to the wild‐type lipase. Mutants with a blocked tunnel could be very useful in applications in which hydrolysis is unwanted, such as the acylation of highly hydrophilic compounds in the presence of water.     

Dry-pasteurization of egg albumen powder in a fluidized bed. II. Effect on functional properties: gelation and foaming

Dry‐pasteurization of egg albumen (EA) powder in a fluidized bed was studied in two experiments. Experiment 1 consisted of two different temperatures (90 and 130 °C) and experiment 2 of two air moisture levels (high and low). Powders were processed from 10 min to 3 h. The reference treatment was traditional pasteurization at 90 °C for 21 h. The fluidized bed treatment effects on gel texture, water‐holding capacity (WHC), protein binding, gel colour, foaming capacity, foam stability and surface pressure were evaluated. Gels of EA powders treated at high temperature and high air moisture levels exhibited higher stress, strain and WHC values than gels of untreated EA powder. The gel colour became significantly darker, greener and less yellow by fluidized bed treatment. Foaming and surface activity properties were un‐affected by the treatments, however, foam stability against liquid drainage correlated positively with surface pressure.     

European Bronze Age Sheet Metal Objects: 3,000 Years of High-Level Bronze Manufacture

This article focuses on the manufacture and usage of selected sheet metal objects from helmets, a vessel, and two shields from the European Bronze Age and Early Iron Age, which date from the thirteenth to seventh centuries BC. Manufacturing traces on the surface, as well as metallographic investigations and the analyses of the alloy composition with scanning electron microscope–energy-dispersive x-ray spectroscopy, provided an insight into the manufacturing techniques and the production of valuable, high-status objects, and highlighted the potential changes in manufacturing techniques and alloys used during different time periods.     

Prediction of Temperature Profiles in Tumors and Surrounding Normal Tissues During Magnetic Induction Heating

The development and preliminary verification of a simple two-compartment model describing the thermal response of adjacent normal and cancerous tissues subjected to magnetic induction heating is presented. Analytical expressions were found for estimating the spatial temperature distributions in the system composed of a spherical tumor mass imbedded in a cylindrical normal tissue as a function of the field intensity and the tissue's physical, geometrical, and physiological characteristics. The conditions leading to preferential heating of the tumor are described.