title: [Application of aspartic acid as a non-specific binding inhibitor in the enrichment of phosphopeptides with titanium dioxide].
abstract: Titanium dioxide (TiO2) is one of metal oxides widely used for phosphopeptide enrichment in phosphoproteomic research nowadays. However it can bind to some non-phosphorylated peptides containing one or more aspartic acid residues and/or glutamic acid residues. These non-phosphorylated peptides can be eluted along with phosphorylated peptides and cause the reduction of the selectivity. Conventional inhibitors for the non-specific binding of non-phosphorylated peptides can often contaminate the ion source of mass spectrometry and therefore their applications are limited in liquid chromatography-mass spectrometry (LC-MS). In this study, aspartic acid was reported as a novel non-specific binding inhibitor for phosphopeptide enrichment by titanium dioxide. Firstly, the tryptic peptide mixtures of 3 and 9 standard proteins were used for the comparison of the enrichment efficiency of titanium dioxide. The effects with the presence of aspartic acid, glutamic acid and no-inhibitor in the enrichment systems were compared separately. The results showed that aspartic acid can greatly improve the selectivity of titanium dioxide for phosphopeptide enrichment. Then, aspartic acid was used for the enrichment of tryptic peptide mixture of C57BL/6J mouse liver lysate and good results were also obtained which demonstrated that aspartic acid was a promising non-specific binding inhibitor for complex biological samples. Besides, no contamination in the ion source occurred during the mass spectrometric analysis.
authors.affiliation: State Key Laboratory of Proteomics, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing 102206, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Chi
authors.forename: Wei
authors.initials: W
authors.lastname: Bi
authors.forename: Zhuang
authors.initials: Z
authors.lastname: Lu
authors.forename: Lina
authors.initials: L
authors.lastname: Song
authors.forename: Wei
authors.initials: W
authors.lastname: Jia
authors.forename: Yangjun
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Qian
authors.forename: Yun
authors.initials: Y
authors.lastname: Cai
mesh_terms: D000327:Adsorption; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry*; D002853:Chromatography, Liquid / Q000379:methods*; D008099:Liver / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D051379:Mice; D008810:Mice, Inbred C57BL; D010748:Phosphopeptides / Q000737:chemistry*; D010766:Phosphorylation; D040901:Proteomics / Q000379:methods; D014025:Titanium / Q000737:chemistry*
chemical_list: D010748:Phosphopeptides; C009495:titanium dioxide; D001224:Aspartic Acid; D014025:Titanium