PhD Scientific Days 2025

Theoretical and Translational Medicine III.

Mechanical and Topographical Analysis of Viral Particles

Name of the presenter

Puskás Péter

Institute/workplace of the presenter

Department of Biophysics and Radiation Biology

Authors

Puskás Péter¹

1: Department of Biophysics and Radiation Biology

Text of the abstract

Tomato brown rugose fruit virus (ToBRFV) has been causing severe agricultural damage worldwide since its recent discovery. Even though ToBRFV is related not only to tobacco mosaic virus, but to other human pathogenic viruses, its structure and infection mechanisms are poorly understood to this day. The goals of our project were to perform a detailed topographical and mechanical analysis of the viral particles, and also to observe the inner structure of the virion. After carefully isolating more than a thousand independent viral particles, we performed topographic and nanomechanical analysis of ToBRFV with AFM. Measurements were peformed in both dry, and wet conditions. Virions are rod-shaped with a height and width of 9.03±0.21 and 31.24±1.27 nm, respectively, pointing at elastic deformation. Length is widely distributed (10-1500 nm) with a mode at 30.3 nm. The virion is thus a cylinder with an outer diameter of 22.1 nm. We detected a 22.7±8.6 nm axial periodicity likely related to structural units. In line with previously gathered data, deep indentations of the viral surface were visually observed. The appearance of these indentations might be linked to the medium that the viruses are observed in. The virion has a Young modulus of 8.7±4.3 MPa, a spring constant of 0.25±0.12 N/m, and a rupture force of 1.7±0.66 nN. The measured rupture force is unusually low for a viral capsid. In the force curves a step was seen at a height of 3.3±0.8 nm, which we assign to the virion wall thickness. We also estimated wall thickness by predicting coat-protein structure with AlphaFold3, which yielded a protein with a length of 7.3 nm. Accordingly, the structural element of ToBRFv is a right circular cylinder with a height and diameter of ~22 nm, and a wall thickness between 3.3-7.3 nm. At least 4-9 serially-linked units are required to form the capsid and encapsulate the helically organized RNA genome. Fragmentation of ToBRFV into structural elements may result in easy release of the genome and thus efficient infection.


SUPPORTED BY THE 2024-2.1.1-EKÖP-2024-00004 UNIVERSITY RESEARCH SCHOLARSHIP PROGRAMME OF THE MINISTRY FOR CULTURE AND INNOVATION FROM THE SOURCE OF THE NATIONAL RESEARCH, DEVELOPMENT AND INNOVATION FUND.