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  1. Abstract Rationale

    Charge transfer dissociation (CTD) is a novel fragmentation technique that demonstrates enhanced structural characterization for a wide variety of molecules compared to standard fragmentation techniques like collision‐induced dissociation (CID). Alternative fragmentation techniques, such as electron transfer dissociation, electron capture dissociation, and ultraviolet photodissociation, also overcome many of the shortfalls of CID, but none of them are a silver bullet that can adequately characterize a wide variety of structures and charge states of target compounds. Given the diversity of structural classes and their occasional obstinance towards certain activation techniques, alternative fragmentation techniques are required that rely on novel or alternative modes of activation.

    Methods

    Herein, we present a step‐by‐step protocol for the installation of CTD on a quadrupole ion trap mass spectrometer and best practices for optimizing the signal‐to‐noise ratio and acquisition times for CTD mass spectra.

    Results

    In addition to two CTD installations in the Jackson laboratory, CTD has also been installed, and is currently in operation, on two 3D ion trap mass spectrometers in France: one in the laboratory of Dr. David Ropartz and Dr. Hélène Rogneaux at INRAE in Nantes, and the other in the laboratory of Dr. Jean‐Yves Salpin at Université d'Évry Val‐d'Essonne, part of the Paris‐Saclay University system.

    Conclusions

    Here, we provide a visual protocol to help others accomplish the instrument modification.

     
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  5. Abstract

    Alkali and alkaline earth metal adducts of a branched glycan, XXXG, were analyzed with helium charge transfer dissociation (He‐CTD) and low‐energy collision‐induced dissociation (LE‐CID) to investigate if metalation would impact the type of fragments generated and the structural characterization of the analyte. The studied adducts included 1+ and 2+ precursors involving one or more of the cations: H+, Na+, K+, Ca2+, and Mg2+. Regardless of the metal adduct, He‐CTD generated abundant and numerous glycosidic and cross‐ring cleavages that were structurally informative and able to identify the 1,4‐linkage and 1,6‐branching patterns. In contrast, the LE‐CID spectra mainly contained glycosidic cleavages, consecutive fragments, and numerous neutral losses, which complicated spectral interpretation. LE‐CID of [M + K + H]2+and [M + Na]+precursors generated a few cross‐ring cleavages, but they were not sufficient to identify the 1,4‐linkage and 1,6‐branching pattern of the XXXG xyloglucan. He‐CTD predominantly generated 1+ fragments from 1+ precursors and 2+ product ions from 2+ precursors, although both LE‐CID and He‐CTD were able to generate 1+ product ions from 2+ adducts of magnesium and calcium. The singly charged fragments derive from the loss of H+from the metalated product ions and the formation of a protonated complementary product ion; such observations are similar to previous reports for magnesium and calcium salts undergoing electron capture dissociation (ECD) activation. However, during He‐CTD, the [M + Mg]2+precursor generated more singly charged product ions than [M + Ca]2+, either because Mg has a higher second ionization potential than Ca or because of conformational differences and the locations of the charging adducts during fragmentation. He‐CTD of the [M + 2Na]2+and the [M + 2 K]2+precursors generated singly charged product ions from the loss of a sodium ion and potassium ion, respectively. In summary, although the metal ions influence the mass and charge state of the observed product ions, the metal ions had a negligible effect on the types of cross‐ring cleavages observed.

     
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