A Tandem Enzymatic sp2‐C‐Methylation Process: Coupling in Situ S‐Adenosyl‐l‐Methionine Formation with Methyl Transfer

A one‐pot, two‐step biocatalytic platform for the regiospecfic C‐methylation and C‐ethylation of aromatic substrates is described. The tandem process utilises SalL (Salinospora tropica) for in situ synthesis of S‐adenosyl‐l ‐methionine (SAM), followed by alkylation of aromatic substrates by the C‐methyltransferase NovO (Streptomyces spheroides). The application of this methodology is demonstrated for the regiospecific labelling of aromatic substrates by the transfer of methyl, ethyl and isotopically labelled ¹³CH_3, ¹³CD₃ and CD₃ groups from their corresponding SAM analogues formed in situ.     

Photo-induced growth of DNA-capped silver nanoparticles

We report the photo-induced nucleation and growth of silver nanoparticles in aqueous solution in the presence of DNA oligomers. An organic dye (Cy5) was used as a photosensitizer to initiate the nanoparticle growth upon illumination with 647 nm light. The formation of nanoparticles and growth kinetics were observed by extinction spectroscopy, dynamic light scattering, and transmission electron microscopy. Irradiation of the precursor solutions with light at the Cy5 absorption maximum triggered the instantaneous formation of spherical particles with a metallic core ~15 nm in diameter. Remarkably, the particles feature significantly larger effective hydrodynamic diameters (35 nm) in solution, indicative of a DNA ad-layer on the nanoparticle surface. Centrifugation experiments confirmed that DNA was inseparably associated with the nanoparticles and indicated that DNA oligomers adsorb onto the nanoparticle surface during growth, playing the role of a capping agent. The introduced method is a fast and facile way to prepare DNA-capped silver nanoparticles in a single growth step.     

Extending the use of zinc‐containing biocides in PVC

While zinc is a crucial element in the formulation of many PVC stabilizers, high levels negatively affect heat and shear stabilities of PVC formulations. Thus, the use of zinc‐containing biocides in PVC has been limited to plastisol formulations, which are not subjected to the heat and shear histories of calendered and extruded formulations. Patented technology has been developed that overcomes many of the stability issues raised by the addition of zinc‐containing biocides to PVC. Specifically, the use of hydrotalcites in combination with zinc pyrithione improves sensitivity to heat and shear as well as retention of the antimicrobial activity of the zinc additive. J. Vinyl Addit. Technol. 10:95–98, 2004. © 2004 Society of Plastics Engineers.     

Familial distal renal tubular acidosis is associated with mutations in the red cell anion exchanger (Band 3, AE1) gene

All affected patients in four families with autosomal dominant familial renal tubular acidosis (dRTA) were heterozygous for mutations in their red cell HCO3-/Cl- exchanger, band 3 (AE1, SLC4A1) genes, and these mutations were not found in any of the nine normal family members studied. The mutation Arg589--> His was present in two families, while Arg589--> Cys and Ser613--> Phe changes were found in the other families. Linkage studies confirmed the co-segregation of the disease with a genetic marker close to AE1. The affected individuals with the Arg589 mutations had reduced red cell sulfate transport and altered glycosylation of the red cell band 3 N-glycan chain. The red cells of individuals with the Ser613--> Phe mutation had markedly increased red cell sulfate transport but almost normal red cell iodide transport. The erythroid and kidney isoforms of the mutant band 3 proteins were expressed in Xenopus oocytes and all showed significant chloride transport activity. We conclude that dominantly inherited dRTA is associated with mutations in band 3; but both the disease and its autosomal dominant inheritance are not related simply to the anion transport activity of the mutant proteins.     

Fat substitution and food intake: effect of replacing fat with sucrose polyester at lunch or evening meals

The objective of the present study was to determine the effect of replacement of fat by sucrose polyester (SPE) within a lunch or evening meal on subsequent energy intake and appetite control. The 2 x 2 design was intended to examine the effect on appetite of reducing the total energy and fat content of a meal (lunch or dinner) by replacement of natural fat with 55 g SPE. The effects were monitored by measuring motivation to eat or actual food consumption during the remainder of the test day (day 1) and throughout the following day (day 2). The 2 x 2 design yielded four conditions which were a control meal (5192 kJ, 73.2 g fat) and a fat-replaced meal (3305 kJ, 54.6 g SPE, 24 g fat) at midday (lunch) or in the early evening (dinner). No significant differences were seen in ad lib. energy intake after the test meals on day 1 or day 2. Certain differences were detected in fat intake on day 2 but these did not suggest nutrient compensation in response to the fat replacement. Subjective assessment of motivation to eat did not indicate that the fat-reduced meal had a weaker satiating efficiency than the control meal. A reduction in fat content, using fat replacement, did not reduce the satiating efficiency of a test meal given at lunch or dinner. No energy or macronutrient compensation occurred following the reduction in energy or fat intake during the rest of the test day or during the whole of the next day.     

Deoxynivalenol: rationale for development and application of a urinary biomarker

Mycotoxins are common dietary contaminants in most regions of the world. The frequency of exposure to the various families of mycotoxins is often dependent on geographic location, national wealth and related agricultural and regulatory infrastructure, combined with diversity of diet and degree of food sufficiency. Deoxynivalenol (DON) is a Fusarium mycotoxin that frequently contaminates wheat, corn and barley in temperate regions. A number of acute poisoning incidences have been linked to DON-contaminated foods and chronic exposure to lower levels of DON has been predicted in many regions. DON is a potent animal toxin and exposure in humans may cause gastroenteritis, growth faltering and immune toxicity. An ability to conduct accurate exposure assessment at the individual level is required to fully understand the potential health consequences for humans. To date, such exposure biomarkers have been lacking for many important mycotoxins, including DON. To better assess exposure to DON at the individual level, we have developed a robust urinary assay, incorporating immunoaffinity column (IAC) enrichment and LC-MS detection. Further refinement of this urinary assay, by inclusion of (13)C-DON as an internal standard, was then undertaken and tested within the UK. DON was frequently observed in urine and was significantly associated with cereal intake. A dietary intervention study demonstrated that avoiding wheat in the diet markedly reduced urinary levels of DON. This biomarker requires further validation but our initial data suggest it may provide a useful tool in epidemiological investigations of the potential health consequences of this common environmental toxin.