Aperture-controllable nano-electrospray emitter and its application in cardiac proteome analysis

Label-Free Direct Identification of MicroRNAs Based on a Narrow Constant-Inner-Diameter Emitter Mass Spectrometry Analysis

MicroRNAs (miRNAs) are a class of endogenous noncoding small RNAs that play important roles in various biological processes and diseases. Direct determination of miRNAs is a cost-efficient and accurate method for analysis. Herein, we established a novel method for the analysis of miRNAs based on a narrow constant-inner-diameter mass spectrometry emitter. We utilized the gravity-assisted sleeving etching method to prepare a constant-inner-diameter mass spectrometry emitter with a capillary inner diameter of 5.5 μm, coupled it with a high-voltage power supply and a high-resolution mass spectrometer, and used it for miRNA direct detection. The method showed high sensitivity and reproducibility for the analysis of four miRNAs, with a limit of detection of 100 nmol/L (170 amol) for the Hsa-miR-1290 analysis. Compared with commercial ion sources, our method achieved higher sensitivity for miRNA detection. In addition, we analyzed the total miRNAs in the A549 cells. The result indicated that both spiked and endogenous miRNAs could be quantified with high accuracy. As a result, this method offers a promising platform for highly sensitive and accurate miRNA analysis. Furthermore, this approach can be extended to the analysis of other small oligonucleotides and holds the potential for studying clinical samples and facilitating disease diagnosis.

Modern Electrospray Ionization Mass Spectrometry Techniques for the Characterization of Supramolecules and Coordination Compounds

Mass spectrometry is routinely used for myriad applications in clinical, industrial, and research laboratories worldwide. Developments in the areas of ionization sources, high-resolution mass analyzers, tandem mass spectrometry, and ion mobility have significantly extended the repertoire of mass spectrometrists; however, for coordination compounds and supramolecules, mass spectrometry remains underexplored and arguably underappreciated. Here, the reader is guided through different tools of modern electrospray ionization mass spectrometry that are suitable for larger inorganic complexes. All steps, from sample preparation and technical details to data analysis and interpretation are discussed. The main target audience of this tutorial is synthetic chemists as well as technicians/mass spectrometrists with little experience in characterizing labile inorganic compounds.

Surface charge-induced electrospray for high-throughput analysis of complex samples and electrochemical reaction intermediates using mass spectrometry

Electrospray-related ion sources are promising for direct mass spectrometric analysis of complex samples, but current protocols suffer from complicated components and low analytical sensitivity. Here, we propose a surface charge-induced electrospray ionization (SCIESI) inspired by flashover on an insulator surface under high voltage. This protocol not only effectively avoids contact between the sample solution and metal electrode, but also allows completion of the entire analytical process in less than 40 seconds and limits of detection in the pictogram per milliliter range. SCIESI coupled to mass spectrometry can also be used to monitor electro-chemical processes, and a number of oxidation and reduction reactions have been studied, demonstrating that it is a powerful tool for understanding electrochemical reaction mechanisms.