Roya Zandi

The same set of parts can assemble into different shapes, just as magnetic beads can form a small cube or a large sphere. That's how hepatitis B virus proteins behave: they build two capsids of different sizes. One is made of 90 protein pairs, the other of 120. Both are stable and appear both in living cells and in the test tube.

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.