Séminaire d'Institut

Mardi 18 Novembre 2025 à 10h30.

From viruses to nanoparticles: the universal language of icosahedra

Riccardo Ferrando
(Department of Physics, University of Genoa)

Salle de convivialité (1ère partie, 10h30 - 11h30) puis Amphi Gouy (11h30 - 12h)

Invité(e) par
Olivier Pierre-Louis

présentera en 2 heures :

''Résumé / Abstract :
The icosahedron is the most symmetric and compact polyhedron. This structure recurs in many contexts: viral capsids frequently adopt icosahedral shapes, as they provide both mechanical stability and genetic economy by assembling identical protein subunits into a highly efficient shell. Beyond viruses, proteins, DNA, colloidal particles, and even inorganic atoms and molecules can spontaneously self-assemble into icosahedral configurations due to their energetic and entropic advantages. Similarly, metallic nanoparticles and nanoalloys often exhibit icosahedral order at sizes of just a few nanometers. Like viruses, these systems can realize a wide variety of icosahedral motifs, both achiral and chiral, with potential relevance for applications in nanoscience and technology.
In the first part of the seminar, we will survey examples of icosahedral structures in both natural and synthetic systems, and we will explain how the geometry of viral capsids can be rationalized using the well-known Caspar–Klug (CK) construction [1].

In the second part, we will extend this framework: inspired by the CK construction, we will present a general theory for assembling multiple icosahedral shells into compact clusters, and we will demonstrate how this theory can be applied to predict stable configurations of nanoalloys composed of up to four different alkali or transition-metal species [2].

Bibliography:
[1] Caspar, D. L. D. & Klug, A. Physical principles in the construction of regular viruses. Cold Spring Harb. Symp. Quant. Biol. 27, 1–24 (1962).
[2] Canestrari, N., Nelli, D. & Ferrando, R. General theory for packing icosahedral shells into multi-component aggregates. Nat Commun 16, 1655 (2025).
''