Analysis and purification of acyl coenzyme A thioesters by reversed-phase ion-pair liquid chromatography.

A rapid method is described for the analysis of mixtures of short-chain acyl coenzyme A thioesters by reversed-phase ion-pair chromatography on LiChrosorb RP-8 and μBondapak C₁₈ columns. The technique is applicable to separation of CoASH, acetyl-CoA propionyl-CoA, and 3-hydroxy-3-methylglutaryl-CoA, as well as dicarboxylic acids and several nucleotides commonly used as cofactors for biosynthetic reactions. The method was utilized on a preparative scale for purification of 3-hydroxy-3-ethylglutaryl-CoA from CoASH and 3-hydroxy-3-ethylglutaric acid. The counterion employed was tetrabutylammonium (phosphate), pH 5.5, in various methanol:water mixtures. Elution profiles and retention values of compounds were influenced by the concentration of counterion and mass of injected sample. Tetrabutylammonium ions could be removed from effluent by ionexchange chromatography on Amberlite IR-120 resin.     

Tourism’s nitrogen footprint on a Mesoamerican coral reef

Globally, the eutrophication of coastal marine environments is a worsening problem that is accelerating the loss of biodiversity and ecosystem services. Coral reefs are among the most sensitive to this change, as chronic inputs of agricultural and wastewater effluents and atmospheric deposition disrupt their naturally oligotrophic state. Often, anthropogenic alteration of the coastal nitrogen pool can proceed undetected as rapid mixing with ocean waters can mask chronic and ephemeral nitrogen inputs. Monitoring nitrogen stable isotope values (δ ¹⁵N) of benthic organisms provides a useful solution to this problem. Through a 7-yr monitoring effort in Quintana Roo, Mexico, we show that δ ¹⁵N values of the common sea fan Gorgonia ventalina were more variable near a developed (Akumal) site than at an undeveloped (Mahahual) site. Beginning in 2007, the global recession decreased tourist visitations to Akumal, which corresponded with a pronounced 1.6 ‰ decline in sea fan δ ¹⁵N through 2009, at which time δ ¹⁵N values were similar to those from Mahahual. With the recovery of tourism, δ ¹⁵N values increased to previous levels. Overall, 84 % of the observed variation in δ ¹⁵N was explained by tourist visitations in the preceding year alone, indicating that variable nitrogen source contributions are correlated with sea fan δ ¹⁵N values. We also found that annual precipitation accounted for some variation in δ ¹⁵N, likely due to its role in groundwater flushing into the sea. Together, these factors accounted for 96 % of the variation in δ ¹⁵N. Using a mixing model, we estimate that sewage can account for up to 42 % of nitrogen in sea fan biomass. These findings illustrate the high connectivity between land-based activities and coral reef productivity and the measurable impact of the tourism industry on the ecosystem it relies on.     

Outgassing Losses of Toluene and m-Xylene Evaluated by 14C-Based Mass Balances for Laboratory Bioventing Simulations

Mixtures of toluene, ethylbenzene, and the xylenes spiked with ¹⁴C-labeled toluene or m-xylene were added to bench-scale bioventing simulation columns filled with hydrocarbon-contaminated subsurface soils. After 2 to 4 weeks of incubation during which air was pumped through the column at rates of at least 2?ml·min^?1·kg^?1 between 54 and 84% of the radiolabel was recovered in traps as outgassed parent compound from four columns sterilized with gamma-irradiation. In contrast, seven nonsterilized but otherwise identically treated (except for inorganic nitrogen addition) columns lost less than 0.4% (and one column lost 0.7%) of the radiolabel through outgassing of the parent compound. Nonsterilized columns lost 40 to 61% of the radiolabel as ¹⁴CO₂, whereas gamma-irradiated columns usually lost only trace amounts of ¹⁴C in this form. Biologically active columns also retained much larger fractions than sterilized columns of the radiolabel in the subsoil in forms, possibly microbial biomass, from which it could be recovered by wet oxidation. Addition of 10 or 40?mg/kg of mineral nitrogen had no consistent effect on bioventing performance.     

Ds excision from extrachromosomal geminivirus vector DNA is coupled to vector DNA replication in maize

Analysis of transposition products generated after Activator (Ac) excision from the P locus in maize suggest that Ac excises either during or after replication of the P locus. The frequency of excision of the non-autonomous Ac derivative, Dissociation ( Ds ), from extrachromosomal replicating and nonreplicating vector DNAs in transfected black mexican sweet maize protoplasts was compared to assess directly a role of extrachromosomal vector DNA replication in Ds excision. Replicating (rep⁺) and non-replicating (rep⁻) vector DNAs comprised a Ds element that harbored a geminivirus, wheat dwarf virus (WDV), origin of replication and WDV genes required for viral DNA replication (rep⁺) or mutant, inactive derivatives of these genes (rep⁻). Excision of Ds was detected only in those cell nuclei co-transfected with the replicating Ds -vector DNA and a transposase expression vector. Quantitative reconstruction experiments showed that Ds excised at least 3 × 10⁵-fold more frequently from replicating vector DNA as compared with nonreplicating vector DNA. Therefore, these results provide direct evidence for a coupling of Ds excision from extrachromosomal vector DNA to vector DNA replication in maize.     

Branched-chain constituents of Brussels sprout wax

The presence of a substantial proportion of branched, in addition to normal compounds, was confirmed in the alkyl ester and primary alcohol components