Topic overview

Start with the big picture

Phase transitions range from protein denaturation and helix–coil changes to lipid bilayer melting, reversible sol–gel transitions, and LCST or UCST phase separation. Their behavior reflects competing enthalpic and entropic effects, molecular interactions, and environmental conditions. Nucleic acid melting, for example, is associated with a hyperchromic effect, while the glass transition involves increased segmental mobility without the latent heat characteristic of first-order melting. Aggregation can include liquid–liquid phase separation before amyloid fibril growth. Techniques such as differential scanning calorimetry and light scattering help characterize these processes. The full lesson connects these concepts to phase diagrams, cooperativity, metastability, and cross-linking.