Electrospray Ionization Mass Spectrometry of Non-Covalent Complexes Formed between N-Alkylimidazolium-Containing Zwitterionic Sulfonates and Protonated Bases

Abstract

This paper describes non-covalent complexes between zwitterionic 3-(1-alkyl-3N-imidazolio)-propane-1-sulfonates and different amines. Electrospray ionization (ESI) mass spectrometry and collision-induced dissociation were used to measure the stability of such complexes in solution and in the gas phase. Generally, zwitterionic sulfonates formed more abundant complexes with protonated 5-methylcytosine (5-MCH) than with aliphatic amines. The results show that the association constants and half-dissociation threshold energies of these complexes nonlinearly depend on the alkyl chain length of the zwitterion. It is shown that the complexes with the lowest stability exist in acetonitrile solution or in the gas phase. The factors responsible for this complicated behavior are discussed.The structure of the complexes was investigated by quantum chemical calculations using molecular mechanics and density functional theory. Hydrogen bonding is proposed as the main type of interaction responsible for the stability of ion-zwitterion complexes. In summary, the information obtained in this study could be used for the development of the new derivatization reagents for some compounds containing amidinium groups, like 5-MCH, to increase selectivity of ESI-based methods.

Determination of Conditional Stability Constants for Phytic Acid Complexes with Mg2+, Ca2+ and Zn2+ Ions Using Electrospray Ionization Mass Spectrometry

“…18 Electrospray ionization-mass spectrometry (ESI-MS) has been widely used to examine the structure and interactions that occur in various complexes. [19][20][21][22][23] Moreover, ESI-MS has been used to determine conditional stability constants. [24][25][26] One of the most popular methods for the determination of conditional stability constants involves monitoring of the intensities of the bound and unbound guests during a titration experiment.…”

Zwitterionic Sulfonates as m/z Shift Reagents for 5-Methylcytosine Detection in Deoxyribonucleic Acids (DNA) Using Flow Injection Analysis and Electrospray Ionisation Mass spectrometry

“…Recently, we reported that several zwitterions containing a sulfonate group and an N-alkylimidazolium ring associate in methanol or acetonitrile with 5-methylcytosine (5-MC). 12 Quantum chemical calculations have shown that the SO 3 group forms hydrogen bonds with the protonated amidine group of 5-MC (see Scheme 1 and Table 1). Taking into account that the determination of 5-MC is often performed to assess the global DNA methylation, 13,14 we were interested in exploring the effect of complex formation between 5-MC and zwitterionic sulfonates for the analysis of DNA samples.…”