### Gas phase self-association of Eudistomin U controlled by gas phase acidity and origin of its interaction with nucleobases.

Electrospray ionization mass spectrometry was used to investigate the intrinsic chem. properties of $\beta$-carbolines: Eudistomin U (as EU) and 5-Br-Eudistomin U (as BrEU) yielding self-assocn. in neg. ion mode. It was obsd. that the deprotonated homodimer of EU was more stable in the gas phase than BrEU. Indeed, BrEU presents a higher polarizability that could influence the dimerization energy. On the contrary, the stability energies calcd. at B3LYP/6-31+G*//AM1 level showed a small difference for these two dimers. To understand the exptl. stability variation, the exptl. and theor. gas phase acidities of these two $\beta$-carbolines have been estd. It has been shown that EU is less acidic than BrEU in the gas phase, which could explain the lower stability of the [2BrEU-H]- dimer. In addn., the investigation of non-covalent interaction of $\beta$-carbolines and nucleobases has been carried out. It was exptl. demonstrated that the deprotonated heterodimer's relative stability scale was [Gua + M-H]- » [Thy + M-H]- {\textgreater} [Ade + M-H]-, but the Cyt/$\beta$-carboline complexes were not obsd. However, the absence of Cyt/$\beta$-carboline complexes could be explained by the great acidity difference between Cyt and $\beta$-carbolines, yielding unstable non-covalent complexes. The studied $\beta$-carbolines showed a particular affinity with guanine which suggested a strong interaction, from a structural and reactivity point of view. Calcd. reaction pathways rationalize the set of exptl. results concerning the heterodimer stabilization reflected by the V1/2 value of breakdown curves of deprotonated heterodimers. [on SciFinder(R)]

### Références

Titre
Gas phase self-association of Eudistomin U controlled by gas phase acidity and origin of its interaction with nucleobases.
Type de publication
Article de revue
Année de publication
2009
Revue
Int. J. Mass Spectrom.
Volume
286
Pagination
43–52
ISSN
1387-3806
Soumis le 12 avril 2018