Trifluoroacetic acid (TFA) (99.0%) was obtained from Acros Organics (New Jersey, USA). Cytochrome C (CytC), trypsin, 2,5dihydroxybenzoic acid (DHB), α-cyano-4-hydroxycinnamic acid (HCCA) and sinapic acid (SA) were purchased from Sigma-Aldrich (St Gallen, Switzerland). Methanol, acetone, ethanol and acetonitrile were obtained from Merck (Dietikon, Switzerland) and formaldehyde solution (4% in PBS) was from Alfa-Aesar (Karlsruhe, Germany). Deionized water was produced by the Alpha Q Millipore system (Zug, Switzerland).
The matrices containing 10 mg per mL of SA, 10 mg per mL of DHB or 10 mg per mL of HCCA were prepared in the solution containing 70% of acetonitrile, 29.9% of water and 0.1% of TFA in terms of v/v. WM-239, WM-115 and Sbcl2 human melanoma cell lines were purchased from the American Type Culture Collection (ATCC).
The matrices containing 10 mg per mL of SA, 10 mg per mL of DHB or 10 mg per mL of HCCA were prepared in the solution containing 70% of acetonitrile, 29.9% of water and 0.1% of TFA in terms of v/v. WM-239, WM-115 and Sbcl2 human melanoma cell lines were purchased from the American Type Culture Collection (ATCC).