Figure 3. LC/MS total ion chromatogram of CNBr-cleaved AQP0

The urea-washed membrane pellets were dissolved in 75% TFA and chemically cleaved by CNBr in the dark for 24 h. After reaction termination with water dilution and lyophilization, the cleavage products were loaded onto a 1 mm ID C4 column and isolated using gradient elution. Major LC fractions were postcolumn collected. The C-terminal 184-263 residues showed abundant signal while the N-terminal and transmembrane residues only displayed weak signal indicating their hydrophobicity and low electrospray ionization efficiency.