Tandem mass spectra of modified human AQP0 peptides. Tandem mass spectrum of a) AQP0 234-263 modified by oleic acid ([M+3H]3+, m/z 1119.2, b) AQP0 234-263 modified by palmitic acid ([M+3H]3+, m/z 1110.5), c) AQP0 1-5 modified by oleic acid ([M+H]+, m/z 998.6, and d) AQP0 1-5 modified by palmitic acid ([M+H]+, m/z 973.2). Black diamonds (◆) indicate fragment ions shifted in mass by lipid modification. Asterisks indicate fragment ions shifted in mass by deamidation. AQP0 234-263 sequence: LSVLK◆ GAKPDVSN*GQPE-VTGEPVELN*TQAL, AQP0 1-5 sequence: ◆MWELR.