Spontaneous Interconversion between Different Narrowly Defined Shapes of Rotavirus Double-Layered Particles Studied in Real Time by High-Resolution Mobility Analysis

Rotavirus double-layered particles(DLPs) are studiedin the gasphase with a high-resolution differential mobility analyzer (DMA).DLPs were transferred to 10 mM aqueous ammonium acetate, electrosprayedinto the gas phase, converted into primarily singly charged particles,and DMA-analyzed. Up to seven slightly different conformations wereresolved, whose apparently random, fast (minutes), and reversibleinterconversions were followed in real time. They sometimes evolvedinto just two distinct structures, with periods of one dominatingover the other and vice versa. Differences between the DLP structuresin solution and in the gas phase are clearly revealed by the smallerDLP diameter found here (60 versus 70 nm). Nevertheless, we arguethat the multiple gas-phase conformers observed originate in as manyconformations pre-existing in solution. We further hypothesize thatthese conformers correspond to incomplete DLPs having lost some ofthe VP6 trimer quintets surrounding each of the 12 5-fold axes. Instancesof this peculiar loss have been previously documented by cryoelectronmicroscopy for the rotavirus Wa strain, as well as via charge detectionmass spectrometry for five other rotavirus strains included in theRotaTec vaccine. Evidence of this loss systematically found for all7 rotavirus types so far studied in aqueous ammonium acetate may bea special feature of this electrolyte.