Figure 4From: Probing the stoichiometry of β2-adrenergic receptor phosphorylation by targeted mass spectrometry Targeted MS of phosphorylation sites S355 and S356 of β2AR. Relative abundance of m/z 769.7 (A) and m/z 949.5 (B) from mono-phospho-peptides, containing either pS355 or pS356. For protocol, see the Materials and methods section.Back to article page