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Poster Presentations
Day 2, June 23（Mon.）
Room P (Maesato East, Foyer, Ocean Wing)
- 2P-AM-29
The Relative Affinities of Amino Acids towards Divalent Metal Ions in the Gas Phase
(1PolyU SZRI, 2PolyU)
oXuewei Lin1,2, Qi Yi1,2, Zhong-Ping Yao1,2
Metal ions play critical roles in biological processes, and their conjunction to proteins has emerged as a key determinant for many protein functions. Determination of affinities of divalent transition metal ions with protein residues, i.e., amino acids (AAs), has been challenging due to issues such as dissociation and oxidation. In this study, the affinities of Cu2+ and Zn2+ with 20 canonical AAs in the gas phase have been investigated by tandem mass spectrometry. Dipeptide TrpHis was found to allow Cu(II) not to be reduced during the dissociation, and the formed metal-bound dimeric complexes [(TrpHis)(Cu2+/Zn2+)(AA)–H]+ would lose an intact AA to form [(TrpHis)(Cu2+/Zn2+)–H]+ during the collision-induced dissociation (CID). The relative affinity order of AAs was determined based on their CID spectral results, which is related to the properties of metal ions and AAs (e.g., side chains). AAs with higher affinities were also the preferential binding sites for the metal ions in proteins. The structures of the complexes were investigated by CID and density functional theory calculations, which showed a geometry with Cu2+/Zn2+ having three coordination sites to TrpHis and one to AA. The results provide new insights into the intrinsic properties of metal ion interactions with AAs and proteins.