A novel method of comparing laser trim pattern geometries of thin film resistors

We present the results from stable isotope labeled precursor feeding studies combined with ultrahigh performance liquid chromatography-high resolution mass spectrometry for the identification of labeled polyketide (PK) end-products. Feeding experiments were performed with ¹³C₈-6-methylsalicylic acid (6-MSA) and ¹³C₁₄-YWA1, both produced in-house, as well as commercial ¹³C₇-benzoic acid and ²H₇-cinnamic acid, in species of <i>Fusarium, Byssochlamys, Aspergillus</i>, and <i>Penicillium</i>. Incorporation of 6-MSA into terreic acid or patulin was not observed in any of six evaluated species covering three genera, because the 6-MSA was shunted into (2<i>Z</i>,4<i>E</i>)-2-methyl-2,4-hexadienedioic acid. This indicates that patulin and terreic acid may be produced in a closed compartment of the cell and that (2<i>Z</i>,4<i>E</i>)-2-methyl-2,4-hexadienedioic acid is a detoxification product toward terreic acid and patulin. In <i>Fusarium</i> spp., YWA1 was shown to be incorporated into aurofusarin, rubrofusarin, and antibiotic Y. In <i>A. niger</i>, benzoic acid was shown to be incorporated into asperrubrol. Incorporation levels of 0.7–20% into the end-products were detected in wild-type strains. Thus, stable isotope labeling is a promising technique for investigation of polyketide biosynthesis and possible compartmentalization of toxic metabolites