Scale-free topology, hubs, and robustness in biological networks
Protein–protein interaction (PPI) networks follow a scale-free degree distribution P(k) ~ k⁻ᵞ (γ ≈ 2–3), arising from preferential attachment: new proteins preferentially interact with highly-connected hubs. This topology confers robustness to random failures (80% of random knockouts cause minimal disruption) but extreme vulnerability to targeted hub removal, a key insight for drug target identification.