A high resolution differential mobility analyzer for the study of large virus particles

Abstract

The conical inner electrode of a recently described differential mobility analyzer (DMA), covering at resolution >50 the size range up to 60 nm, has been modified by increasing its radius at the outlet slit from 1 cm to 1.6 cm, and decreasing its convergence angle from 3 o to 0.5 o . The cylindrical outer electrode radius is maintained at 2 cm, while other critical dimensions are only slightly modified. The classification voltage for fixed flow rate of sheath gas and particle diameter decreases almost fourfold, extending the size range theoretically spanned at high resolution well beyond 120 nm. Tests with multiply charged polystyrene latex spheres 200 nm in diameter confirm the actual ability to cover this wide size range. A resolution above 100 (with no corrections for instrument or particle nonidealities) is demonstrated with rotavirus double-layered particles (DLP) whose mobility diameter is found to be near 60 nm. The DLP has several configurations that complicate its use for DMA characterization, but occasionally presents mainly one conformer, with singularly narrow relative mobility width FWHM<1/150. Two broad range instruments with slightly different axial lengths have been developed and tested, both reaching resolving powers of 100.

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

“…(a) Mobility spectra. After figure 8a of ref . (b) Resolution (1/FWHM) of selected main peaks from (a) inferred by Gaussian fitting with two Gaussian curves.…”

“…Following this approach, highly concentrated DLPs (>1 mg/mL) were obtained. Some peculiarities of the mobility spectra obtained by these DLPs have been recently described …”

“…The experimental approach has been previously reported in more detail. , Briefly, the DLPs were transferred by dialysis (ThermoFisher Slide-A-Lyzer MINI device, 10 kDa molecular weight cutoff) from their original saline suspensions into 10 mM aqueous ammonium acetate, such that the electrolyte included as few involatile salts as possible. This volatile electrolyte was electrosprayed in positive mode from the tip of a silica capillary pulled under a flame to a diameter of about 30–50 μm.…”

“…Most of the experiments reported in this study relied on a Perez-LT-Thin, with k = 0.236 (cm 2 /s)/(L/min) . However, a few measurements on SA11 DLPs to be specifically indicated were carried out with another DMA referred to as the Perez-MT-Fat, for which k = 0.0546 (cm 2 /s)/(L/min) . The raw mobility spectra to be reported will be in the form of a detector signal in counts/s versus either V or Z , inferred via (1) from the experimentally controlled quantities Q and V .…”

“…Some peculiarities of the mobility spectra obtained by these DLPs have been recently described. 17 Mobility Analysis. The experimental approach has been previously reported in more detail.…”