LSD1 Histone Demethylase Assays and Inhibition.

The lysine-specific demethylase (LSD1) is a flavin-dependent amine oxidase that selectively removes one or two methyl groups from histone H3 at the Lys4 position. Along with histone deacetylases 1 and 2, LSD1 is involved in epigenetically silencing gene expression. LSD1 has been implicated as a potential therapeutic target in cancer and other diseases. In this chapter, we discuss several approaches to measure LSD1 demethylase activity and their relative strengths and limitations for inhibitor discovery and mechanistic characterization. In addition, we review the principal established chemical functional groups derived from monoamine oxidase inhibitors that have been investigated in the context of LSD1 as demethylase inhibitors. Finally, we highlight a few examples of recently developed LSD1 mechanism-based inactivators and their biomedical applications.

Tandem-in-time mass spectrometry method for the sub-parts-per-trillion determination of 2,3,7,8-chlorine-substituted dibenzo-p-dioxins and -furans in high-fat foods.

Limits of quantitation (LOQs) for a quadrupole ion storage tandem-in-time mass spectrometry (QISTMS) method were evaluated through replicate analysis of unfortified peanut oil, shortening, lamb fat, and butter for all 2,3,7,8-chlorine-substituted polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs). Ten congeners were measurable in butter (0.27-2.5 pg/g) and nine congeners were measurable in lamb fat (0.09-2.6 pg/g) with good precision. LOQs for high-fat foods were estimated by triplicate analysis of peanut oil fortified at two levels. Accurate and reproducible results were achieved at 0.5 pg/g for most PCDD/Fs (1.0 pg/g for heptachlorodibenzo-p-dioxin and heptachlorodibenzofuran and 2.0 pg/g for octachlorodibenzofuran) and at 0.2 pg/g for 2,3,7,8-tetrachlorodibenzofuran (TCDF) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). QISTMS distinguished between catfish and chicken eggs with elevated TCDD levels from background samples collected from the most regions of the continental United States. QISTMS determined the extent of TCDD contamination in butter, lamb fat, and cottonseed oil collected from rural villages in Kazakhstan. Replicate analysis of catfish and chicken eggs by the QISTMS method produced comparable results to high-resolution mass spectrometry (HRMS). Lower limits of detection will be needed if QISTMS is to fully complement HRMS in the measurement of TCDD levels in food.