Statistical Physics in Biology

Polymer Theory 2, Collapse, Random Energy Model

1. Interacting polymers:
   • Entropy; excluded volume; and solvent-mediated interactions
   • Mean-field estimate of the partition function
2. Swollen (coil) phase in good solvents
   • Flory exponent
   • Scaling behavior in other dimensions
3. Compact (globular) phase in poor solvents
   • Polymer collapse, theta-point
   • Thermodynamic behavior at the transition; reduction in entropy
4. Frozen (folded) state of heteropolymers
   • The Random Energy Model (REM)
   • The freezing transition and associated singularities
   • Designed REM as a model of protein folding

(Detailed Lecture Notes (PDF))