(a) Schematic view of MALDI TOF MS equipment (Bruker Saxonia), and (b) mass spectrogram of dopamine. Note the background signal generated by the matrix (4-hydroxy--cyanocinnamic acid).
(a) Principle of desorption/ionization of a biosample for the MALDI method (hydrophobic spot on the target plate), the DIOS method (porous silicon spot on a silicon wafer), and the DIOSD method (porous silicon dioxide spot on a silicon wafer) in comparison with (b) the DIOSTA method.
Cross-sectional view of the gated silicon tips.
Step-by-step fabrication process of the array of gated silicon tips.
Scanning electron microscopy pictures of silicon wafer: (a) after plasma etching of silicon to form tips; (b) after deposition of plasma-enhanced chemical-vapor deposition layer, Cr–Au bilayer and photoresist (AZ); and (c) after opening windows in photoresist layer.
(a) DIOSTA platform with three spots and (b) a few gated silicon tips not covered with the biosample.
Mass spectrogram of dopamine 65 pmol per spot: (a) DIOSTA method, spectrogram was obtained for 100 laser-light pulses and (b) DIOSD method, spectrogram was obtained for 165 laser-light pulses. Positive (protonized) molecular ion at a m/z of 154.1 and its fragment at 137.03, as well as signals at m/z’s of 176.0 and 192.0, which are sodium and potassium adducts of dopamine, may be seen.
Mass spectrogram of LGG tripetide 40 pmol per spot: (a) DIOSTA method, spectrogram was obtained for 15 laser-light pulses; (b) DIOS method; and (c) DIOSD method. Spectrograms (b) and (c) were obtained for 165 laser-light pulses. Positive (protonized) molecular ion at a m/z of 246.2 and signals at m/z’s of 268.2 and 284.2, which are sodium and potassium adducts of tripeptide, may be seen.
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