PubMed · 7917624
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G J Re, J B Summit. 1994-10-08. Detector dyes.. https://doi.org/10.1038/sj.bdj.4808568
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Pretreatment of human serum with 5-sulfosalicylic acid (SSA) as used in the Abbott TDx digoxin assay produces deglycosylated congeners of digoxin (DIG) and of endogenous digoxin-like immunoreactive factor (DLIF). Using high-performance liquid chromatography analysis, we observed differences in the degree and pattern of DIG breakdown products among five patients. The aglycone digoxigenin was the major product in several samples. Smaller amounts of the bis- and mono-digitoxosides and unidentified products less polar than DIG were sometimes present. Treatment of DLIF-containing plasma with SSA produced similar patterns of DLIF-breakdown products. Incubation of normal plasma containing DIG with SSA for up to 30 min caused little change in measured DIG by TDx and radioimmunoassay (RIA) but decreased to 50% in the ACS DIG assay. These results are consistent with the near 100% cross-reactivities of deglycosylated DIG congeners in the TDx and RIA assays compared to their lower cross-reactivities in the ACS assay. We conclude that the breakdown of DIG and DLIF during treatment of serum with SSA may compromise the accuracy of TDx DIG assays and may explain discrepancies observed in other studies between digoxin immunoassays. This study underscores the importance of understanding the effects of pretreatment strategies used for analytes measured by immunoassay.
The biodegradation of undecylbenzenesulphonate (C11LAS) was studied in shake flasks at 21 degrees C using two mixed bacterial cultures. The first culture, MM1, contained a type II methanotroph and four heterotrophs, and was enriched from a groundwater aquifer. The second culture, MC, consisted of five heterotrophic strains, most of them belonging to the genus Pseudomonas, and was isolated from the wastewater of a detergent plant. Methane, carbon dioxide and oxygen concentrations were determined by gas chromatography. Concentrations of C11LAS and the aromatic intermediates were determined by reversed-phase HPLC. In spite of faster transformation of the alkyl side-chain by the culture MC, the culture MM1 containing type II methanotroph was capable of further degradation of C11LAS aromatic intermediates (sulphophenylalkanoates). The most probable mechanism for the degradation of the alkyl part of the C11LAS molecule by both cultures was omega-oxidation of the terminal methyl group followed by beta-oxidation. Studies of methane utilization demonstrated an approximately three times higher second-order rate coefficient for methane consumption (kmax/Ks) in the absence of C11LAS. This indicates a possible metabolic activity of methanotrophs in the transformation of the complex LAS molecule due to the methane monooxygenase enzyme system.