Vacuum Ultraviolet Postionization of Aromatic Groups Covalently Bound to Peptides

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• 作者：Praneeth D. Edirisinghe ; Jerry F. Moore ; Wallis F. Calaway ; Igor V. Veryovkin ; Michael J. Pellin ; Luke Hanley
• 刊名：Analytical Chemistry
• 出版年：2006
• 出版时间：August 15, 2006
• 年：2006
• 卷：78
• 期：16
• 页码：5876 - 5883
• 全文大小：154K
• 年卷期：v.78,no.16(August 15, 2006)
• ISSN：1520-6882

文摘

Experiments demonstrate that peptides with ionizationpotentials (IPs) above 7.87 eV can be single-photon-ionized in the gas phase with a molecular fluorine laserfollowing prior chemical derivatization with one of severalaromatic tags acting as chromophores. 4-(Dimethylamino)benzoic acid, 1-naphthylacetic acid, and 9-anthracenecarboxylic acid (denoted Benz, Naph and Anth, respectively) behave as chromophores, allowing single-photonionization for vacuum ultraviolet (VUV) laser light bylowering the IP of the tagged peptide. Anth-tagged peptides that are laser-desorbed from a substrate and subsequently postionized produce mass spectra dominatedby the intact radical cation, although protonated ions andfragmented species are also observed. Electronic structure calculations on Anth-tagged peptides indicate that inaddition to lowering the ionization potential, the presenceof the aromatic tag increases charge localization on anddelocalization across the ring structure, which presumablystabilizes the radical cation. Measurements on severaltagged peptides confirm this calculation and show that thestabilizing effect of the tag increases with the size of theconjugated system in the order Benz < Naph < Anth. Thetagged hexapeptide Anth-GAPKSC exhibits the parention, whereas the Benz- and Naph-tagged peptides do not.These results are supported by the experimental comparison of Anth-tagged vs untagged tryptophan, furthersuggesting that VUV postionization of tagged high-IPspecies is a promising method for expanding the capabilities of mass spectrometric analyses of molecular species.