Mtp 384 polished steel

The evaluation of Cu₂O PS as an ionization-assisting material was performed on a MALDI-TOF–MS instrument (UltrafleXtreme, Bruker Daltonics, Bremen, Germany) with a Smart-beam TM II laser (Nd:YAG) operated at 355 nm, and working in positive mode. DHB solution (20 mg mL⁻¹) was prepared in ACN:0.1% TFA (30:70 v/v) mixture. A hybrid matrix (Cu₂O PS@DHB) was prepared by mixing equal volumes of freshly prepared Cu₂O PS aqueous suspensions and DHB solutions to get a final concentration of 2.5 mg mL⁻¹ and 10 mg mL⁻¹, respectively. This mixture was sonicated for 2 min. Then, 0.5 µL of Cu₂O PS@DHB matrix was dropped on the target plate (MTP 384 polished steel, Bruker Daltonics) with a micropipette. After the sample plate was air dried, 0.5 µL of a protein standard solution (or protein digest) was added and left to dry prior to analysis. Intact proteins were analyzed using linear detection mode, while peptides were analyzed using reflector mode. The laser intensity was set to 80% of the total intensity and spots were irradiated with 7000 shots in a random walk pattern. For each analysis, 5 replicates were used. Data were acquired with the FlexControl software and processed with the Flex Analysis version 3.4 (Bruker Daltonics).