Multiply-Charged Negative Clusters of Adenosine-5′-Monophosphate in the Gas Phase

Multiply-charged noncovalent cluster anions of adenosine-5′-monophosphate (AMP) were formed by electrospray ionization (ESI). Ions in higher charge states were observed when the ions were accumulated in an ion trap with helium buffer gas before detection. We determined the smallest size (na) or appearance size as a function of charge state (q), i.e., na = 4 for q = 2, na = 8 for q = 3, and na = 13 for q = 4. The relation between na and q can be described by a charged droplet model. When the size is larger than na for a given q, the fragmentation pathway of an anion cluster is dominated by loss of neutral fragments. In contrast, when the size approaches the appearance size, only charged fragments are formed

Electron capture induced dissociation of peptide ions: Identification of neutral fragments from secondary collisions with cesium vapor

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Photodissociation of dinucleotide ions in a storage ring

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On the hydrogen loss from protonated nucleobases after electronic excitation or collisional electron capture

International audienceIn this work, we have subjected protonated nucleobases MH+ (M = guanine, adenine, thymine, uracil and cytosine) to a range of experiments that involve high-energy (50 keV) collision-induced dissociation (CID) and electron capture-induced dissociation. In the tatter case, both neutralisation reionisation and charge reversal were done. For the CID experiments, the ions interacted with O-2. In neutral reionisation, caesium atoms were used as the target gas and the protonated nucleobases captured electrons to give neutrals. These were reionised to cations a microsecond later in collisions with O-2. In choosing Cs as the target gas, we have ensured that the first electron transfer process is favourable (by about 0.1-0.8 eV depending on the base). In the case of protonated adenine, charge reversal experiments (two Cs collisions) were also carried out, with the results corroborating those from the neutralisation-reionisation experiments. We find that white collisional excitation of protonated nucleobases in O-2 may lead to hydrogen loss with limited probabilities, this channel becomes dominant for electron capture events. Indeed, when sampling reionised neutrals on a microsecond timescale, we see that the ratio between MH+ and M+ is 0.2-0.4 when one electron is captured from Cs. There are differences in these ratios between the bases but no obvious correlation with recombination energies was found