Whole virus capsids weighed for first time


Rebecca Pool

Thursday, November 29, 2018 - 13:45
Electron microscopy images of T5 virus capsids on a nanomechanical resonator. [CEA-Leti]
France-based researchers have demonstrated mass-spectrometry based on nanomechanical resonators that measures the mass of particles previously beyond the reach of commercial technology.
The 'nano-weighing' system - called neutral mass spectroscopy - has measured the mass of a whole bacteriophage virus capsid.
"To our knowledge, this is the highest molecular mass ever determined by mass spectrometry," highlights Sebastien Hentz, Director of Research at CEA-Leti.
Viruses and many large biomolecule complexes, including biomarkers for cancer and degenerative diseases, are in a mass range that is difficult to measure using conventional mass spectrometry methods.
While nanomechanical resonators can determine masses of impacting molecules, separation methods often lose too much of a sample to be efficient.
Given this, Hentz and colleagues set out to develop a new nanomechanical mass-spectrometry system to analyse particles in this mass range.
‘Neutral Mass Spectrometry’ fills the gap in existing weighing technologies
The system uses a surface acoustic wave device to nebulize nanoparticles in solution into a mist of small droplets, which are then aspirated into a vacuum system.
A carrier gas is then used to focus these particles into a very narrow beam, which is guided towards a detector, comprising an array of nanomechanical resonators.
This detector then detects the mass of the incoming particles, one after the other.
As Hentz and colleagues highlights in Science, the system was used to determine the mass distribution of ~30-megadalton polystyrene nanoparticles with high detection efficiency.
It also effectively performed molecular mass measurements of empty or DNA-filled bacteriophage T5 capsids with masses up to 105 megadaltons, using less than 1 picomole of sample.
Until now, the mass of the virus capsid - the bacteriophage T5 - had only been estimated, but results indicate that with a size of 93nm, the capsid actually weighs around 105 megadaltons.
Hentz believes the system opens prospects for many nanoparticles of biomedical interest, because no commercial instrument can efficiently analyse particles in this MDa-to-GDa mass range today.
Research is published in Science.
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