Detection of trace amounts of molecules empowers the molecular characterization of a systems’ state during health and stress, such as exposure to toxins or drug molecules. Liquid chromatography (LC) mass spectrometry (MS) is the technology of choice for the measurement of metabolites and proteins from large amounts of starting materials. Here, we describe a custom-designed microanalytical capillary electrophoresis (CE) interface for electrospray ionization (ESI) tandem MS to also enable metabolic and proteomic characterization in trace amounts of samples. Our microanalytical CE-ESI-MS platform is compatible with 1–100 nL sample volume and is able to detect low attomoles of metabolite or hundreds of zeptomoles of protein standards, providing sufficient sensitivity to detect endogenous molecules in biological systems. As an example, we demonstrate the utility of the platform for characterizing the metabolic and proteomic activity state of identified single cells in the vertebrate embryo of the South African clawed frog (<i>Xenopus laevis</i>), which is a powerful cell/developmental biological model and has been used in toxicological studies. We detected hundreds of metabolite signals and ~2,000 protein groups in cells that are fated to give rise to nervous, epidermal, and hindgut tissues in the embryo. Furthermore, CE-ESI-MS was found quantitative over 3–5 log-order dynamic range, raising a potential to also quantify a system’s molecular activity state. As a proof-of-principle experiment, we manually dissected and capillary-sampled identified cells in the embryo and quantified the abundance of glutathione (GSH) and oxidized glutathione (GSSG). Dissected cells were found to yield significantly lower GSH/GSSG ratios, which suggests that these cells were exposed to higher oxidative stress. With label-free and ultrasensitive detection, CE-ESI-MS presents attractive alternative to traditional LC-MS in toxicological studies.

Capillary electrophoresis for trace-level detection: Metabolites and proteins

254th National Meeting (2017)

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