An improved assay for the determination of phospholipase C activity

Phospholipases C (PLC, EC 3.1.4.3) are enzymes that specifically hydrolyze the C‐O‐P bond in phospholipids, yielding sn‐1,2(2,3)‐diacylglycerides and the phosphate residue bearing the corresponding headgroup. The biochemical characterization of PLC requires methods for the reliable determination of their activity. Here, an assay is described in which the phosphate residue released by the PLC is cleaved with an alkaline phosphatase. The phosphate formed is then extracted with n‐butanol and quantified as phosphomolybate complex. The applicability of this method is demonstrated for a concentration range from 10 nM to 10 mM for a range of phospholipids bearing different headgroups in an aqueous and a two‐phase system. The method has the additional advantage that the crude enzyme can be used without the need for purification.     

Crystallization of S-layer protein lattices on surfaces and interfaces

A review is given on the structure, chemistry, and assembly of crystalline bacterial cell surface layers (S-layers). S-layers composed of single protein or glycoprotein species represent the most common cell surface structures observed in prokaryotic organisms. Isolated S-layer proteins possess the intrinsic property for recrystallization into isoporous monomolecular arrays in suspension and at a broad spectrum of surfaces (e.g. silicon, metals, polymers) and interfaces (e.g. air–liquid interface or lipid films). The well-defined arrangement of functional groups on S-layer lattices allows the binding of functional molecules (e.g. enzymes, antibodies, ligands) and particles in defined regular arrays. S-layers also represent templates for the formation of inorganic nanocrystal superlattices (e.g. Au, CdS, Pt) as required for molecular electronics and non-linear optics. Finally, S-layers can be used as the structural basis for a biomolecular construction kit involving all major species of biological molecules for applications in molecular nanotechnology, nanobiotechnology and biomimetics.     

Ozonation of Cycloalkenes Dissolved in Ethanol

The ozonation of cyclooctene and cyclododecene in ethanol was studied at 278 K in a stirred reactor with a flat gas/liquid interface. The parallel reactions with ethanol in the gas and the liquid phase had to be accounted for. At high cyclooctene concentrations, ozone transfer into the liquid phase was enhanced by up to a factor of E = 325. Due to the high ozone solubility and the high enhancement factors, up to half of the mass transfer resistance was on the gas-side. The reaction rate constant k₂ is more than threefold higher for cyclooctene as compared to cyclododecene.     

The fracture behaviour of a welded tubular joint—an ESIS TC1.3 round robin on failure assessment methods: Part VI: application of WES 2805-1997

The Japanese flaw assessment method WES 2805-1997 is applied to the fracture tests on welded tubular T-joints presented in Engineering Fracture Mechanics (2002;69). The approach is shown to yield conservative results for small amounts of stable crack growth but it overestimates the load carrying capacity for larger amounts of stable crack growth. As a consequence it is proposed to restrict the application to ductile crack initiation and to brittle fracture below or at stable crack initiation.     

Automatic Roundtrip Engineering

A systematic method for roundtrip engineering of systems, automatic roundtrip engineering (ARE), is presented. It relies on the automatic derivation of inverses for domain transformations. While roundtrip engineering is a well known system engineering method, systematic conditions for its deployment have not yet been formalized, and this is done in the paper. Secondly, ARE is a generic architectural style for different architectural scenarios. To show this, the paper gives a first classification, defining several subclasses of ARE systems: sequenced ARE systems, automatic Model-View-Controller engineering (MVARE), and bidirectional aspect systems (Beavers). Sequenced ARE systems extend the ARE principle to chains of transformations. MVARE systems project a domain into a set of simpler ones, simplifying system understanding. Beaving systems generalize aspect-oriented programming to roundtrip engineering. All ARE classes describe different generic application architectures and have a great potential to simplify the construction of roundtrip engineering tools and applications.     

A method for correction of cosine errors in measurements of spectral UV irradiance

One of the sources contributing to the overall uncertainty of spectral UV radiation measurements is the cosine error of the spectroradiometer. It leads to measurement errors that depend on atmospheric conditions and on solar zenith angle, and thus time of the day and season. Though the foreoptics of modern instruments are designed such as to minimize cosine errors, there remain deviations from the ideal cosine response. We have worked out a method to further reduce that remaining cosine error in global spectral irradiance. This method was applied to spectra of global UV radiation taken with a Brewer spectroradiometer. The only additional input data needed to apply the method of cosine correction to spectral irradiance data are concurrent broad-band UV-B radiation measurements of diffuse and global radiation recorded with filter UV instruments, which are used to estimate the optical thickness referred to global UV radiation for the time when the spectral scan is taken. The method takes account of the variable conditions of cloudiness and turbidity. In the case of measurements taken with Brewer instrument No. 30, the cosine corrected global UV-B radiation was higher than the measured irradiance by 9–20%, and even its daily totals turned out to be higher than the uncorrected radiation by 13–18%. An estimate of the uncertainty of ±4 to ±8% was derived from a theoretical approach as well as from model calculations using a radiative transfer model.