The assembly of a virus shell is like fastening a button: protein blocks must interlock in the correct order, and thermal fluctuations act like trembling fingers. With weak binding, the trembling helps find the right position — the shell closes faster. With strong binding, the fluctuations hinder: completing assembly is as tough as buttoning a button on stiff fabric with shaky hands.
Previously, this process was described like crystal growth, neglecting the 'trembling fingers.' But the edge trembling isn't just a nuisance: it's a tool: it increases entropy, the measure of disorder, and changes the edge tension. Amazingly, the amplitude of this trembling can reach the size of an entire protein block, as if a button were dancing in front of the buttonhole, tracing circles several centimeters wide. That's what controls the assembly speed.
The discovered mechanism explains the error-free assembly of viruses and hints at how to create nanocontainers for targeted drug delivery.
Thermal fluctuations at the virus scale are so strong that an incomplete shell can bend by an amount comparable to the size of a single protein block.