【Abstract】 In this work, the change of gas-phase proton affinity of alkyl-alanine through the phosphorylation reaction was studied by the electrospray ionization mass spectrometry with kinetic method. It was proved that the phosphorylation could increase the proton affinity of small peptide. A proposal that proton affinity increase might be responsible for the sensitivity improvement of small peptide in mass spectrometry has been provided.更多还原