The target plate has 384 sample spots in standard micro-titer plate format plus 96 spots for mass calibration, one per every 4 sample spots. Every target plate comes with a unique ID number. This unique ID is automatically recognized when the plate is introduced into a mass spectrometer and stored with the mass spectrometric data.
The topographic effect of the matrix crystal leads to a difference of flight start position for the ions, which in turn affect the overall flight time of each ion. In a conventional ion optics system, this time difference degrades the mass resolving power and also the mass accuracy obtained using an external mass calibration. Because the SpiralTOF has such a large flight path, these problems are minimized, resulting in a highly reproducible mass resolving power and high mass accuracy using an external mass calibration.
A standard peptide mixture was applied to a calibration spot on the standard target plate, and a tryptic digest of bovine serum albumin equivalent to 25 fmol of the protein was applied to the four sample spots surrounding the calibration spot. After automatic spectral acquisition, peak picking (including de-isotoping) was carried out and then a database search was performed with the MASCOT (Matrix Science Ltd.) PMF method. Excellent mass accuracy of the JMS-S3000 is shown in the table, which summarizes the average mass error of all matched peptides at each spot.
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