Maldi tof

LEU acetate was used as a drug purchased from Anygen (Kwangju, Korea). Stearic acid, oleic acid, linoleic acid were used as fatty acids purchased from Sigma-Aldrich (Saint Louis, MO, USA). Benzoyl chloride was used as a chemical intermediate, triethylamine as a catalyst and acid neutralizer, and 4-Dimethylaminopyridine (DMAP) as a coupling reaction agent (Sigma-Aldrich). Phosphate-buffered saline tablets and sodium hexanesulfonate used in the degradation studies were purchased from Sigma-Aldrich. A dialysis membrane (MWCO: 1000 Da) was purchased from Spectrum Labs (San Francisco, CA, USA) and used for purification. 2,5-Dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid were used as matrices for MALDI-TOF (Sigma-Aldrich). Peptide calibration standard II was used for matrix-assisted laser desorption and ionization (Bruker, Billerica, MA, USA). A PB-M membrane was used as a permeation barrier membrane (UMC Science, Goyang, Korea). Isopropyl myristate was used as a membrane activator (Sigma-Aldrich Saint Louis, USA). Tetrahydrofuran (THF), 99.5% absolute ethanol, HPLC-grade methanol, and trifluoroacetic acid (TFA) were purchased from Samchundang (Seoul, Korea).