Inter-cultivar variation in soil-to-plant transfer of radiocaesium and radiostrontium in Brassica oleracea

Radiocaesium and radiostrontium enter the human food chain primarily via soil-plant transfer. However, uptake of these radionuclides can differ significantly within species (between cultivars). The aim of this study was to assess inter-cultivar variation in soil-to-plant transfer of radiocaesium and radiostrontium in a leafy crop species, Brassica oleracea. This study comprised four independent experiments: two pot experiments in a controlled environment artificially contaminated with radiocaesium, and two field experiments in an area contaminated with radiocaesium and radiostrontium in the Chernobyl Exclusion Zone. Radiocaesium concentration ratios varied 35-fold among 27 cultivars grown in pots in a controlled environment. These 27 cultivars were then grown with a further 44 and 43 other cultivars in the Chernobyl Exclusion Zone in 2003 and 2004, respectively. In the field-grown cultivars radiocaesium concentration ratios varied by up to 35-fold and radiostrontium concentration ratios varied by up to 23-fold.In three of these experiments (one pot experiment, two field experiments) one out of the 27 cultivars was found to have a consistently lower radiocaesium concentration ratio than the other cultivars. The two field experiments showed that, five out of the 66 cultivars common to both experiments had consistently lower radiocaesium concentration ratios, and two cultivars had consistently lower radiostrontium concentration ratios. One cultivar had consistently lower radiocaesium and radiostrontium concentration ratios.The identification of cultivars that have consistently lower radiocaesium and/or radiostrontium concentration ratios suggests that cultivar selection or substitution may be an effective remediation strategy in radiologically contaminated areas. Future research should focus on plant species that are known to be the largest contributors to human dose

SNi from SN2: a front-face mechanism ‘synthase’ engineered from a retaining hydrolase

SNi or SNi-like mechanisms, in which leaving group departure and nucleophile approach occur on the same ‘front’ face, have been observed previously experimentally and computationally in both the chemical and enzymatic (glycosyltransferase) substitution reactions of α-glycosyl electrophiles. Given the availability of often energetically comparable competing pathways for substitution (SNi vs SN1 vs SN2) the precise modulation of this archetypal reaction type should be feasible. Here, we show that the drastic engineering of a protein that catalyzes substitution, a retaining β-glycosidase (from Sulfolobus solfataricus SSβG), apparently changes the mode of reaction from “SN2” to “SNi”. Destruction of the nucleophilic Glu387 of SSβG-WT through Glu387Tyr mutation (E387Y) created a catalyst (SSβG-E387Y) with lowered but clear transglycosylation substitution activity with activated substrates, altered substrate and reaction preferences and hence useful synthetic (‘synthase’) utility by virtue of its low hydrolytic activity with unactivated substrates. Strikingly, the catalyst still displayed retaining β stereoselectivity, despite lacking a suitable nucleophile; pH-activity profile, mechanism-based inactivators and mutational analyses suggest that SSβG-E387Y operates without either the use of nucleophile or general acid/base residues, consistent with a SNi or SNi-like mechanism. An x-ray structure of SSβG-E387Y and subsequent metadynamics simulation suggest recruitment of substrates aided by a π-sugar interaction with the introduced Tyr387 and reveal a QM/MM free energy landscape for the substitution reaction catalyzed by this unnatural enzyme similar to those of known natural, SNi-like glycosyltransferase (GT) enzymes. Proton flight from the putative hydroxyl nucleophile to the developing p-nitrophenoxide leaving group of the substituted molecule in the reactant complex creates a hydrogen bond that appears to crucially facilitate the mechanism, mimicking the natural mechanism of SNi-GTs. An oxocarbenium ion-pair minimum along the reaction pathway suggests a step-wise SNi-like DN*ANss rather than a concerted SNi DNAN mechanism. This first observation of a front face mechanism in a β-retaining glycosyl transfer enzyme highlights, not only that unusual SNi reaction pathways may be accessed through direct engineering of catalysts with suitable environments, but also suggests that ‘β-SNi’ reactions are also feasible for glycosyl transfer enzymes and the more widespread existence of SNi or SNi-like mechanism in nature

Measuring alcohol consumption for genomic meta-analyses of alcohol intake: opportunities and challenges

Whereas moderate drinking may have health benefits, excessive alcohol consumption causes many important acute and chronic diseases and is the third leading contributor to preventable death in the United States. Twin studies suggest that alcohol-consumption patterns are heritable (50%); however, multiple genetic variants of modest effect size are likely to contribute to this heritable variation. Genome-wide association studies provide a tool for discovering genetic loci that contribute to variations in alcohol consumption. Opportunities exist to identify susceptibility loci with modest effect by meta-analyzing together multiple studies. However, existing studies assessed many different aspects of alcohol use, such as typical compared with heavy drinking, and these different assessments can be difficult to reconcile. In addition, many studies lack the ability to distinguish between lifetime and recent abstention or to assess the pattern of drinking during the week, and a variety of such concerns surround the appropriateness of developing a common summary measure of alcohol intake. Combining such measures of alcohol intake can cause heterogeneity and exposure misclassification, cause a reduction in power, and affect the magnitude of genetic association signals. In this review, we discuss the challenges associated with harmonizing alcohol-consumption data from studies with widely different assessment instruments, with a particular focus on large-scale genetic studies

Transfer of cadmium and mercury to sheep tissues

Toxic heavy metals such as cadmium and mercury can enter the diet of farm animals by a variety of environmental exposure routes and, hence, contaminate food products derived from those animals. Therefore, there is a need to be able to predict the likely levels of contamination in animal tissues if exposed to a contaminated diet and also to estimate how rapidly an animal will decontaminate once the source of contamination is removed from the diet. Data on the transfer and excretion rates of Cd and Hg from tissues have previously been inadequate to allow the development of dynamic models to predict changes in the degree of contamination of different tissues of ruminants. A study is described during which a group of sheep were given a single oral administration of 109Cd and 203Hg. Measurements of the concentrations of the radioisotopes in tissue samples were subsequently made over a period of 1 year. The resultant data were used to develop compartment models to describe the behavior of the two metals in sheep tissues. To our knowledge the models developed are the first to allow the time-dependent prediction of the potential Cd and Hg contamination of animal-derived food products. Previously only advised transfer coefficients were available; we demonstrate that these are of little value for cadmium and mercury due to their slow rates of accumulation and excretion

e-Science from the Antarctic to the GRID

Monitoring life-processes in a frozen lake in the Antarctic raises many practical challenges. To supplement manual monitoring we have designed, built and successfully deployed a remote monitoring device on one of the lakes of interest. This returns data to the Antarctic base over the Iridium satellite phone network. This provides us with a new and uniquely detailed view of the lifeprocesses in that environment, and is allowing us to understand that environment in new ways, for example exploring diurnal effects, and detailed energy flow models. We have integrated this sensing device into a common Grid-based software infrastructure; this makes the device and its sensors visible on the Grid as services, and also maintains an archive of sensor measurements. A desktop user interface allows non-programmers to work with this data in a flexible way. The experience of creating and deploying this device has given us a rich view of the many elements and processes that must be brought together to make possible this kind of e-Science

Measuring alcohol consumption for genomic meta-analyses of alcohol intake: opportunities and challenges

Whereas moderate drinking may have health benefits, excessive alco-hol consumption causes many important acute and chronic diseases and is the third leading contributor to preventable death in the United States. Twin studies suggest that alcohol-consumption patterns are her-itable (50%); however, multiple genetic variants of modest effect size are likely to contribute to this heritable variation. Genome-wide asso-ciation studies provide a tool for discovering genetic loci that contrib-ute to variations in alcohol consumption. Opportunities exist to identify susceptibility loci with modest effect by meta-analyzing to-gether multiple studies. However, existing studies assessed many dif-ferent aspects of alcohol use, such as typical compared with heavy drinking, and these different assessments can be difficult to reconcile. In addition, many studies lack the ability to distinguish between life-time and recent abstention or to assess the pattern of drinking during the week, and a variety of such concerns surround the appropriateness of developing a common summary measure of alcohol intake. Com-bining such measures of alcohol intake can cause heterogeneity and exposure misclassification, cause a reduction in power, and affect the magnitude of genetic association signals. In this review, we discuss the challenges associated with harmonizing alcohol-consumption data from studies with widely different assessment instruments, with a par-ticular focus on large-scale genetic studies. Am J Clin Nutr 2012;95:539–47