Advancing liquid atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry toward ultra-high-throughput analysis

Label-free high-throughput screening using mass spectrometry has the potential to provide rapid large-scale sample analysis at a speed of more than one sample per second. Such speed is important for compound library, assay and future clinical screening of millions of samples within a reasonable time frame. Herein, we present a liquid atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) setup for high-throughput large-scale sample analysis (>5 samples per second) for three substance classes (peptides, antibiotics and lipids). Liquid support matrices (LSM) were used for the analysis of standard substances as well as complex biological fluids (milk). Throughput and analytical robustness were mainly dependent on the complexity of the sample composition and the current limitations of the commercial hardware. However, the ultimate limits of liquid AP-MALDI in sample throughput can be conservatively estimated to be beyond 10-20 samples per second. This level of analytical speed is highly competitive compared with other label-free MS methods, including electrospray ionization and solid state MALDI, as well as MS methods using multiplexing by labelling, which in principle can also be used in combination with liquid AP-MALDI MS

Ultrahigh-throughput sample analysis using liquid atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry

Mass spectrometry (MS) allows for automated analysis of complex samples at high resolution without the need for labeling/derivatization. Liquid atmospheric pressure matrix-assisted laser desorption/ionization (LAP-MALDI) enables rapid sample preparation and MS analysis using microtiter-plate formats and high-performing mass spectrometers. We present a step change in high-speed, large-scale MS sample analysis of peptides at 20 samples/s and an enzymatic assay at 40 samples/s, i.e., an order of magnitude faster than current MS platforms. LAP-MALDI requires only low amounts of sample volume (1 million samples per day

Dataset supporting 'The use of salts, buffers and surfactants in LAP-MALDI MS'

As part of the PhD project 'Advancing liquid MALDI ion source designs and applications in modern biological mass spectrometry' funded by the University of Reading and Waters Corporation the influence of salts, buffers, surfactants and other substances on the LAP-MALDI MS signal of a peptide mix was investigated. The peptide mix containing leucine enkephalin, angiotensin I, bradykinin, substance P and melittin was mixed with substances at different concentrations. Those were: 1) buffers (HEPES, MES, MOPS, tris, tricine, PBS), 2) salts (chlorides of calcium, potassium, magnesium, sodium, ammonium and acetates of magnesium, ammonium and sodium), 3) surfactants (sodium dodecyl sulphate, sodium deoxycholate, octyl-beta-D-glucopyranoside, CHAPS, amidosulfobetamine-14), 4) ammonium salts and serine (ammonium acetate, tartrate, citrate, phosphate, oxalate) and 5) other substances (EDTA, ammonium sulphate, urea, bovine serum albumin, formic acid, trifluoracetic acid and dimethyl sulfoxide). All samples were analysed at least in triplicate with a water-based sample as reference. For the LAP-MALDI analysis a CHCA-based liquid support matrix was used and samples were analysed on a Synapt G2-SI. The data archived here include the raw data and sample locations

Ultrahigh-throughput LAP-MALDI MS analysis of peptides and an enzyme assay

As part of the PhD project 'Advancing liquid MALDI Ion Source Designs and Applications in Modern Biological Mass Spectrometry' funded by the University of Reading and Waters Corporation the possiblity for high-throughput analysis of biomolecules was investigated. Raw and processed data for liquid atmospheric-pressure matrix-assisted laser desorption/ionisation (LAP-MALDI) mass spectrometry analysis of peptides and enzyme assay at speeds greater than 20 samples/s using a hardware and software-modified Synapt G2-Si with a UV laser are presented. The deposited data relate to the research article 'Ultrahigh-throughput sample analysis using liquid atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry', 2022, Krenkel et al., https://doi.org/10.1021/acs.analchem.1c05614

The use of salts, buffers and surfactants in LAP-MALDI MS

Biological samples such as tissue extracts and enzymatic assays typically have a complex composition, which can interfere with analyte ionisation and detection in mass spectrometry (MS). Ionisation techniques such as electrospray ionisation (ESI) are often coupled online to an upfront chromatographic separation, whereas sample preparations for techniques such as conventional matrix-assisted laser desorption/ionisation (MALDI) are performed offline and, in the case of MALDI, rely on sample clean-up owing to different crystallisation behaviour. Liquid atmospheric pressure matrix-assisted laser desorption/ionisation (LAP-MALDI) MS is a hybrid ionisation technique that has been previously used to analyse a wide range of biological samples at fast acquisition rates. Here we report data from a systematic investigation of the influence of various buffer compounds, salts, surfactants, and other compounds necessary for biological sample preparation reflected in the signal intensity of a standard peptide mixture. Tricine showed the least signal reduction from the buffer compounds tested as did octyl-β-D-glucopyranoside for the surfactants. It can be concluded that LAP-MALDI MS can be used to analyse biological samples directly without major sample clean-up if their content of additives is not too high