Modeling the interactions between peptide functions and Sr2+: formamide–Sr2+ reactions in the gas phase

Abstract

The interactions between formamide, which can be considered a prototype of a peptide function, and Sr(2+) have been investigated by combining nanoelectrospray ionization/mass spectrometry techniques and G96LYP DFT calculations. For Sr an extended LANL2DZ basis set was employed, together with a 6-311+G(3df,2p) basis set expansion for the remaining atoms of the system. The observed reactivity seems to be dominated by the Coulomb explosion process yielding [SrOH](+) + [HNCH](+), which are the most intense peaks in the MS/MS spectra. Nevertheless, additional peaks corresponding to the loss of HNC and CO indicate that the association of Sr(2+) to water or to ammonia leads to long-lived doubly charged species detectable in the timescale of these experimental techniques. The topology of the calculated potential energy surface permits us to establish the mechanisms behind these processes. Although the interaction between the neutral base and Sr(2+) is essentially electrostatic, the polarization triggered by the doubly charged metal ion results in the activation of several bonds, and favors different proton transfer mechanisms required for the formation of the [SrOH](+), [SrOH(2)](2+) and [SrNH(3)](2+) products.

Gas‐phase interactions of organotin compounds with cysteine

“…The collisionally activated dissociation (CAD) parameter, which roughly controls the amount of N 2 introduced into Q2, was set to its minimum value (1) in order to limit multiple ion–molecule collisions. This resulted in pressure values of 1–2 × 10−5 Torr as measured by the ion gauge located at vicinity but outside the collision cell, but it has been reported that the pressure inside the collision cell is in fact in the order of 10 mTorr. Consequently at this pressure, even with the minimum amount of N 2 inside the collision cell, and as we already discussed in previous papers, we are certainly under a multiple collision regime.…”

Gas‐Phase Interactions between Lead(II) Ions and Cytosine: Tandem Mass Spectrometry and Infrared Multiple‐Photon Dissociation Spectroscopy Study

“…[15] Notably, as discussed in previous papers, MS/MS spectra are very likely obtained under a multiple-collision regime, and this will increase the internal energy content of the precursor ion. [16,17] MS/MS spectra were recorded at different collision energies ranging from 0 to 35 eV in the laboratory frame (E lab ; the kinetic energy of ions is given by the difference of potentials between the focusing quadrupole Q0 preceding Q1 and the collision cell Q2).…”

Atomic decomposition of conceptual DFT descriptors: application to proton transfer reactions

“…[22][23][24][25][26][27][28][29] In addition, both molecules possess an amide functional group, which is the basic building block of proteins and enzymes, and they can also be considered as models for nucleic bases. [22][23][24][25][26][27][28][29] In addition, both molecules possess an amide functional group, which is the basic building block of proteins and enzymes, and they can also be considered as models for nucleic bases.…”