Measuring the Radius of Gyration and Intrinsic Flexibility of Viral Proteins in Buffer Solution Using Small-Angle X-ray Scattering

Riccardo Funari, Nikhil Bhalla, Luigi Gentile

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3 Citations (Scopus)
21 Downloads (Pure)


Measuring structural features of proteins dispersed in buffer solution, in contrast to crystal form, is indispensable in understanding morphological characteristics of the biomolecule in a native environment. We report on the structure and apparent viscosity of unfolded α and β variants of SARS-CoV-2 spike proteins dispersed in buffer solutions. The radius of gyration of the β variant is found to be larger than that of the α variant, while the ab initio computation of one of the possible particle-like bodies is consistent with the small-angle X-ray scattering (SAXS) profiles resembling a conformation similar to the three-dimensional structure of the folded state of the corresponding α and β spike variant. However, a smaller radius of gyration with respect to the predicted folded state of 2.4 and 2.7 is observed for both α and β variants, respectively. Our work complements the structural characterization of spike proteins using cryo-electron microscopy techniques. The measurement/analysis discussed here might be useful for quick and cost-effective evaluation of several protein structures, let alone mutated viral proteins, which is useful for drug discovery/development applications.
Original languageEnglish
Pages (from-to)547-552
Number of pages6
JournalACS Measurement Science Au
Issue number6
Early online date12 Sept 2022
Publication statusPublished online - 12 Sept 2022

Bibliographical note

Funding Information:
L.G. is thankful to the European Soft Matter Infrastructure (EUSMI). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 731019 (EUSMI). N.B. would like to thank the internal support of Nanotechnology and Integrated Bioengineering Centre (NIBEC), School of Engineering, Ulster University for providing COVID recovery funds to support this project.

Publisher Copyright:
© 2022 American Chemical Society.


  • SAXS
  • spike proteins
  • rheology
  • viscosity
  • viruses


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