1. Physics 414: Introduction to Biophysics Professor Henry Greenside September 14, 2017

2. Search YouTube also for “dialysis tubing”
Egg Osmosis (Hypertonic vs. Hypotonic Solution)
Search YouTube also for “dialysis tubing”

3. Steps in applying statistical mechanics

4. Study binding of ligands in solution to bound receptor

5. Use lattice approximation for solvent to simplify calculating microstates

6. First step: identify microstates, identify their energies Ei, count their multiplicities

7. Work out details at blackboard

8. Langmuir adsorption isotherm p=p(c) average fraction of receptors bound with ligand
Assume V_box = (1 nm)^3, leads to effective concentration 10/6 ~ 1.7 M.

9. Langmuir isotherm rare in biology, reason is cooperativity (related to allostery)

10. Holds for ideal gas or dilute solution
More efficient and general to derive Langmuir isotherm using chemical potentials and Gibbs factor
Assume V_box = (1 nm)^3, leads to effective concentration 10/6 ~ 1.7 M.
Holds for ideal gas or dilute solution

11. Model gene expression by probability of RNA polymerase binding to promoter on DNA

12. Opportunities for cells to control cellular processes in the “central dogma”

13. Identify microstates of RNAP on DNA

14. Determine energies, multiplicities, calculate Z

15. When dust clears, same Langmuir profile
= “binding energy to specific (S) promoter domain (pd)”
minus the “binding energy to a non-specific
(NS) promoter domain”

16. Statistical physics can include activators and repressors for gene regulation (Chapter 19)

17. Partition function that includes activators and repressors for gene regulation

18. Group quiz, time to work on homework

19. One-minute End-of-class Question