We have investigated the effects of brief, non-specific deuteration of Drosophila melanogaster by including varying percentages of ²H (D) in the H₂O used in the food mix consumed during initial ...development. Up to 22.5% deuterium oxide (D₂O) in H₂O was administered, with the result that a low percentage of D₂O in the water increased mean life span, whereas the highest percentage used (22.5%) reduced life span. After the one-time treatment period, adult flies were maintained ad libitum with food of normal isotopic distribution. At low deuterium levels, where life span extension was observed, there was no observed change in fecundity. Dead flies were assayed for deuterium incorporation by complete hydrolysis in hot 12 N HCl solution followed by subsequent high-performance liquid chromatography/mass spectrometry (HPLC/MS). Isoleucine and leucine residues showed a small, linear dose-dependent incorporation of deuterium at non-exchangeable sites. Although high levels of D₂O itself are toxic for other reasons, higher levels of deuterium incorporation, which can be achieved without toxicity by strategies that avoid direct use of D₂O, are clearly worth exploring.
Silicone wristbands are promising passive samplers to support epidemiology studies in characterizing exposure to organic contaminants; however, investigating associated health risks remains ...challenging due to the latency period for many chronic diseases that take years to manifest. Dogs provide valuable insights as sentinels for exposure-related human disease because they share similar exposures in the home, have shorter lifespans, share many clinical/biological features, and have closely related genomes. Here, we evaluated exposures among pet dogs and their owners using silicone dog tags and wristbands to determine if contaminant levels were correlated with validated exposure biomarkers. Significant correlations between measures on dog tags and wristbands were observed (r
s
= 0.38–0.90; p <0.05). Correlations with their respective urinary biomarkers were stronger in dog tags compared to human wristbands (r
s
= 0.50–0.71; p <0.01) for several organophosphate esters. This supports the value of using silicone bands with dogs to investigate health impacts on humans from shared exposures.
Cellulose, the main structural component of plant cell walls, is the most abundant carbohydrate polymer in nature. To break down plant cell walls, anaerobic microorganisms have evolved a large ...extracellular enzyme complex termed cellulosome. This megadalton catalytic machinery organizes an enzymatic assembly, tenaciously bound to a scaffolding protein via specialized intermodular “cohesin-dockerin” interactions that serve to enhance synergistic activity among the different catalytic subunits. Here, we report the solution structure properties of cellulosome-like assemblies analyzed by small angle x-ray scattering and molecular dynamics. The atomic models, generated by our strategy for the free chimeric scaffoldin and for binary and ternary complexes, reveal the existence of various conformations due to intrinsic structural flexibility with no, or only coincidental, inter-cohesin interactions. These results provide primary evidence concerning the mechanisms by which these protein assemblies attain their remarkable synergy. The data suggest that the motional freedom of the scaffoldin allows precise positioning of the complexed enzymes according to the topography of the substrate, whereas short-scale motions permitted by residual flexibility of the enzyme linkers allow “fine-tuning” of individual catalytic domains.
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