5‑Diethylamino-naphthalene-1-sulfonyl Chloride
(DensCl): A Novel Triplex Isotope Labeling Reagent for Quantitative
Metabolome Analysis by Liquid Chromatography Mass Spectrometry
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Abstract
We
describe a new set of isotope reagents, <sup>12</sup>C<sub>4</sub>-, <sup>12</sup>C<sub>2</sub><sup>13</sup>C<sub>2</sub>-, and <sup>13</sup>C<sub>4</sub>-5-diethylamino-naphthalene-1-sulfonyl chloride
(DensCl), in combination with liquid chromatography Fourier-transform
ion cyclotron resonance mass spectrometry (LC-FTICR-MS), for improved
analysis of the amine- and phenol-containing submetabolome. The synthesis
of the reagents is reported, and an optimized derivatization protocol
for labeling amines and phenols is described. To demonstrate the utility
of the triplex reagents for metabolome profiling of biological samples,
urine samples collected daily from a healthy volunteer over a period
of 14 days were analyzed. The overall workflow is straightforward,
including differential isotope labeling of individual samples and
a pooled sample that serves a global internal standard, mixing of
the isotope differentially labeled samples and LC-MS analysis for
relative metabolome quantification. Comparing to the dansyl chloride
(DnsCl) duplex isotope reagents, the new triplex DensCl reagents offer
the advantages of improved metabolite detectability due to enhanced
sensitivity (i.e., about 1000 peak pairs detected by DensCl labeling
vs about 600 peak pairs detected by DnsCl labeling) and analysis speed
(i.e., simultaneous analysis of two comparative samples by DensCl
vs only one comparative sample analyzed by DnsCl)