naa a22 4500 510738257 CHVBK 20180411083018.0 cr unu---uuuuu 180411e20130301xx s 000 0 eng 10.1007/s12127-012-0114-0 doi (NATIONALLICENCE)springer-10.1007/s12127-012-0114-0 The effects of cation adduction upon the conformation of three-helix bundle protein domains [Elektronische Daten] [Kleitos Sokratous, Robert Layfield, Neil Oldham] The ubiquitin-binding, three-helix bundle domains of the proteins ubiquilin 1 (UQ1) and hHR23A both exhibited remarkably high, but discrete, ammonium ion adduction when electrosprayed from aqueous ammonium acetate. The degree of adduction was highly charge state dependent with, unusually, the lowest charge states (+3 for UQ1 and +4 for hHR23A) showing almost no adducts and the highest charge states (+5 for UQ1 and +6 for hHR23A) exhibiting adduction with two ammonium cations as the most abundant form. As the charge state of protein ions produced by electrospray ionisation (ESI) is related to solvent-accessible surface area we inferred that the ammonium-carrying ions were of a more open conformation than their protonated counterparts. This was confirmed by ESI-travelling wave ion mobility spectrometry-mass spectrometry (TWIMS-MS), which showed that, although the purely protonated ions were compact, their equivalents bearing one or two ammonium adducts exhibited populations of significantly larger collisional cross section (CCS). We postulate that complexation with the ammonium cation may disrupt a key salt bridge(s) in the compact structure. A similar effect is observed with mono-sodium ion adduction, but this is diminished with each additional sodium ion in the complex to produce more compact structures. Springer-Verlag Berlin Heidelberg, 2012 Travelling wave ion mobility spectrometry (TWIMS) nationallicence Electrospray ionization-mass spectrometry (ESI-MS) nationallicence Gas-phase protein conformation nationallicence Cation adduction nationallicence Sokratous Kleitos School of Chemistry, University of Nottingham, NG7 2RD, University Park, Nottingham, UK aut Layfield Robert School of Biomedical Sciences, University of Nottingham, Medical School, Queens Medical Centre, NG7 2UH, Nottingham, UK aut Oldham Neil School of Chemistry, University of Nottingham, NG7 2RD, University Park, Nottingham, UK aut International Journal for Ion Mobility Spectrometry Springer-Verlag 16/1(2013-03-01), 19-27 1435-6163 16:1<19 2013 16 12127 https://doi.org/10.1007/s12127-012-0114-0 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s12127-012-0114-0 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Sokratous Kleitos School of Chemistry, University of Nottingham, NG7 2RD, University Park, Nottingham, UK aut NATIONALLICENCE 700 1- Layfield Robert School of Biomedical Sciences, University of Nottingham, Medical School, Queens Medical Centre, NG7 2UH, Nottingham, UK aut NATIONALLICENCE 700 1- Oldham Neil School of Chemistry, University of Nottingham, NG7 2RD, University Park, Nottingham, UK aut NATIONALLICENCE 773 0- International Journal for Ion Mobility Spectrometry Springer-Verlag 16/1(2013-03-01), 19-27 1435-6163 16:1<19 2013 16 12127 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer