X-ray photoabsorption-induced processes within protonated rifamycin sodium salts in the gas phase

Abstract

Up to now, the response of antibiotics upon ionizing radiation has been very scarcely reported. Here, we present the results of X-ray photoabsorption experiments on isolated rifamycin, a broad-range antibiotic against Gram-positive and Gram-negative bacteria. A mass spectrometer has been coupled to a synchrotron beamline to analyze cationic products of photoabsorption on protonated rifamycin dimer and monomer sodium salts. Absorption of a single photon in the 100-300eV energy range leads to ionization of the molecular system, followed by vibrational energy deposition and subsequent inter-and/or intramolecular fragmentation. Interestingly, we observe a proton transfer from sodiated rifamycin to rifamycin, a widely observed process in ionized molecular systems in the gas phase. Moreover, we show that another charge-transfer process occurs in both dimer and monomer: intramolecular sodium transfer, which has not been reported yet, to the best of our knowledge.

Radiation‐Induced Transfer of Charge, Atoms, and Energy within Isolated Biomolecular Systems

“…Studying the consequences of VUV photoelectron detachment from [V+R‐2H] 2− , in which [V−H] − is bound to [R−H] − , allowed us to show that vibrational energy can be transferred from V to R if the electron is detached from V, but also from R to V if the electron is detached from R [50] . In another article, we reported that intermolecular proton transfer also occurs within a noncovalent dimer of rifamycin, another antibiotic, as a result of X‐ray photoabsorption [53] . Thanks to collision‐induced dissociation experiments, we also demonstrated that the cations of rifamycin including one sodium atom that are formed by electrospray ionization are protonated salts, i. e .…”

“…In addition to hydrogen/proton, also other atoms such as sodium can in principle be transferred. To our knowledge, we were the first to show that sodium transfer can occur as a result of ionization of gas‐phase molecular systems [53] . When a proton or a sodium ion is transferred, not only mass but also charge moves, and we will discuss ionization‐induced charge transfer in the next section.…”

Ionizing radiation induces cross-linking of two noncovalently bound collagen mimetic peptide triple helices in the absence of a molecular environment

“…Consistently, the ionization of noncovalent complexes by X-ray photoabsorption leads to their extensive dissociation. [15][16][17] To date, the irradiation of higherorder assemblies of collagen mimetic peptides has not been investigated in the gas phase.…”