Gas-Phase Collisions with Trimethylamine-N-Oxide Enable Activation-Controlled Protein Ion Charge Reduction.

Kaldmäe M, Österlund N, Lianoudaki D, Sahin C, Bergman P, Nyman T, Kronqvist N, Ilag LL, Allison TM, Marklund EG, Landreh M

J. Am. Soc. Mass Spectrom. 30 (8) 1385-1388 [2019-08-00; online 2019-07-08]

Modulating protein ion charge is a useful tool for the study of protein folding and interactions by electrospray ionization mass spectrometry. Here, we investigate activation-dependent charge reduction of protein ions with the chemical chaperone trimethylamine-N-oxide (TMAO). Based on experiments carried out on proteins ranging from 4.5 to 35 kDa, we find that when combined with collisional activation, TMAO removes approximately 60% of the charges acquired under native conditions. Ion mobility measurements furthermore show that TMAO-mediated charge reduction produces the same end charge state and arrival time distributions for native-like and denatured protein ions. Our results suggest that gas-phase collisions between the protein ions and TMAO result in proton transfer, in line with previous findings for dimethyl- and trimethylamine. By adjusting the energy of the collisions experienced by the ions, it is possible to control the degree of charge reduction, making TMAO a highly dynamic charge reducer that opens new avenues for manipulating protein charge states in ESI-MS and for investigating the relationship between protein charge and conformation. ᅟ.

Protein Science Facility (PSF) [Service]

PubMed 31286443

DOI 10.1007/s13361-019-02177-8

Crossref 10.1007/s13361-019-02177-8

pmc: PMC6669196
pii: 10.1007/s13361-019-02177-8