Exceeding a resolving power of 50 for virus size determination by differential mobility analysis

Abstract

A recently described DMA designed for high resolution viral particle analysis ( Perez-DMA; Perez-Lorenzo et al, 2020) is modified to decrease the relative peak full width at half maximum ( FWHM) below previously achieved ≈3.3%. The electrode radii at the outlet slit ( R 1 = 1.01 cm; R 2 = 2 cm) and the working length are almost unchanged ( L = 114.9 vs. 116 mm). The laminarization trumpet and the radius of the curve merging the trumpet to the working section are both considerably widened to improve gas flow laminarization. DMA evaluation with salt clusters is improved by reducing the flow resistance at the gas outlet, to reach substantially larger sheath gas flow rates Q ˜ 1700 L/min. Tests with tetraheptylammonium bromide clusters with a center rod diverging at 3 o demonstrate FWHM<2.7%, without indications of performance loss due to turbulence even at 1700 L/min. Correcting these high flow rate data for diffusive broadening reveals a maximal DMA FWHM in the limit of non-diffusing particles and zero sample flow, FWHM ∞ = 1.8%. An uncorrected peak width approaching 2% is independently demonstrated at much lower flow rates of sheath gas with two recently described bee virus particle standards having singularly narrow size distributions at mean diameters of 38 and 17 nm. Correcting raw 38 nm particle peak widths for broadening due to diffusion and aerosol to sheath gas flow rate ratio q/Q shows an even more ideal response with FWHM ∞ <1%, where this value includes nonidealities in the DMA as well as possible lack of monodispersity in the viral particles.

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

“…The selected mobility Z is controlled by the flow rate Q and the voltage difference V applied across two DMA electrodes according to Z = k Q / V where k is the geometrical constant of the DMA. 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) .…”

“…Most of the experiments reported in this study relied on a Perez-LT-Thin, with k = 0.236 (cm 2 /s)/(L/min). 18 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). 17 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.…”

Singularly Narrow Viral Size and Mobility Standards from the 38.3 nm Chronic Bee Paralysis Virus and Its 17.5 nm Satellite

“…The group ZV / Q is a constant that depends only on geometry and is therefore fixed for a given DMA. V may be controlled with good resolution from 1 to 10 kV, while Q has been successfully controlled in the range from 9 to 1800 L/min . Control of V and Q then spans a range of mobilities of 2000.…”

“…The instrument used at Yale will be described in detail elsewhere . It is a variant of the viral DMA of Perez-Lorenzo et al, with a considerably wider laminarization trumpet and a larger transition radius in the section matching the conical trumpet (30° semiangle) to the outer electrode.…”

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

“…We have recently reported the characteristics of a differential mobility analyzer (DMA) termed here the Perez-LT-Thin DMA (Perez-Lorenzo et al, 2021). That instrument has a cylindrical outer electrode with radius R2= 2 cm, and a conical inner electrode diverging with a 3 o half-angle and achieving a maximal radius R1=1 cm at the outlet slit.…”