Mass spectrometric method for analyzing metabolites in yeast with single cell sensitivity

In situ metabolic profiling of single cells by laser ablation electrospray ionization mass spectrometry

Depending on age, phase in the cell cycle, nutrition, and environmental factors, individual cells exhibit large metabolic diversity. To explore metabolic variations in cell populations, laser ablation electrospray ionization (LAESI) mass spectrometry (MS) was used for the in situ analysis of individual cells at atmospheric pressure. Single cell ablation was achieved by delivering mid-IR laser pulses through the etched tip of a GeO(2)-based glass fiber. Metabolic analysis was performed from single cells and small cell populations of Allium cepa and Narcissus pseudonarcissus bulb epidermis, as well as single eggs of Lytechinus pictus. Of the 332 peaks detected for A. cepa, 35 were assigned to metabolites with the help of accurate ion masses and tandem MS. The metabolic profiles from single cells of the two plant species included a large variety of oligosaccharides including possibly fructans in A. cepa, and alkaloids, e.g., lycorine in N. pseudonarcissus. Analysis of adjacent individual cells with a difference in pigmentation showed that, in addition to essential metabolites found in both variants, the pigmented cells contained anthocyanidins, other flavonoids, and their glucosides. Analysis of single epidermal cells from different scale leaves in an A. cepa bulb showed metabolic differences corresponding to their age. Our results indicate the feasibility of using LAESI-MS for the in situ analysis of metabolites in single cells with potential applications in studying cell differentiation, changes due to disease states, and response to xenobiotics.

Single cell analytics: an overview

The research field of single cell analysis is rapidly expanding, driven by developments in flow cytometry, microscopy, lab-on-a-chip devices, and many other fields. The promises of these developments include deciphering cellular mechanisms and the quantification of cell-to-cell differences, ideally with spatio-temporal resolution. However, these promises are challenging as the analytical techniques have to cope with minute analyte amounts and concentrations. We formulate first these challenges and then present state-of-the-art analytical techniques available to investigate the different cellular hierarchies--from the genome to the phenome, i.e., the sum of all phenotypes.

High-throughput capillary-electrophoresis analysis of the contents of a single mitochondria

We present a technique for labeling the contents of acidic organelles and rapidly releasing, separating, and detecting their labeled contents with laser-induced fluorescence. We have performed solution-phase separation of the contents of single mitochondria and single 100 nm vesicles, which represents a demonstration of an analyzed volume of approximately 1 aL. Our strategy to label the acidic contents of the mitochondrion relies on the use of the membrane-permeable dye, Oregon Green diacetate succinimidyl ester, and a membrane-permeable base to raise intramitochondrial pH. In order to measure the contents, we utilized a glass microfluidic chip and high voltage gradient for millisecond capillary electrophoresis separation after single-mitochondrion photolysis. We observed heterogeneity among a population of mitochondria with respect to a constituent chemical component.

Facile analysis of metabolites by capillary electrophoresis coupled to matrix-assisted laser desorption/ionization mass spectrometry using target plates with polysilazane nanocoating and grooves

We present an inexpensive method and apparatus for the deposition of analytes separated by capillary electrophoresis (CE) onto a custom-designed matrix-assisted laser desorption/ionization (MALDI) target plate. This dedicated CE-MALDI plate is coated with an omniphobic polysilazane nanocoating and has an array of parallel grooves acting as recipients of the separation effluent. The 3-D pattern in the top layer of the coated plate greatly improves loading of the matrix solution prior to separation and facilitates deposition of the separated species. We demonstrate application of this straightforward protocol to the analysis of metabolites from the central metabolic pathway in a complex biological sample spiked with small molecule standards.