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Abstract

Under electrospray ionization (ESI) conditions, several ions are observed from a 1.5 × 10⁻⁶ M solution of [Pt(terpy)Cl]Cl in water including: [Pt(terpy)Cl]⁺ (base peak), [Pt(terpy)HO]⁺ and [Pt(terpy)H₂O]²⁺. When a 30- to 40-fold excess of glycine or its N- or O-methyl derivatives was added, the ESI mass spectrum was still dominated by the [Pt(terpy)Cl]⁺ ion, although a number of new ions were observed including [Pt(terpy)M]²⁺, [Pt(terpy)M – H]⁺, [M + H]⁺ and [2M + H]⁺ ions (where M = the amino acid). In contrast, when a 10-fold excess of cysteine was used, the [Pt(terpy)Cl]⁺ ion virtually disappeared and the dominant ion became the [Pt(terpy)M – H]⁺ ion. These results are consistent with the known solution chemistry of [Pt(terpy)Cl]Cl, which shows a preference for binding via the thiolate of cysteine residues. In addition, collision-induced dissociation was performed on both the [Pt(terpy)M]²⁺ and [Pt(terpy)M – H]⁺ ions of glycine and cysteine. Isotopic labeling and methyl derivatives were used to elucidate the mechanisms of their fragmentation reactions.

Keywords

Electrospray ionization tandem mass spectrometry platinum terpyridine complexes glycine cysteine ion trap mass spectrometer

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References

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Letter: Formation and Fragmentation Reactions of Platinum-Terpyridine Complexes of Glycine and Cysteine and Their Methyl Derivatives via Electrospray Ionization Mass Spectrometry

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