20.410J Lecture 19 Notes

BEN 410 04/25/2003 Lecture Schedule 04/15: Read 2.1 to 2.5 04/17: 2.2.1 to 2.2.6 04/20: Quiz 04/22: Lecture 04/25: Read 2.1.6 Work done by a non-covalent force: ΔL=∫ x 1 ​ x 2 ​ ​ F(x)dx F(x) = position of binding between two bases (distance b/w two bases) ∫ x 1 ​ x 2 ​ ​ F(x)dx = area under the force curve Typical numbers: Energy per base pair = -10 kcal/mol Number of base pairs = 5000 Total energy = -10 kcal/mol * 5000 = -50,000 kcal Concepts: Self-assembly: Molecules can self-assemble into complex structures. Non-covalent interactions: These are forces that hold molecules together without forming covalent bonds. Micelles: Spherical structures formed by amphiphilic molecules. Bilayers: Sheet-like structures formed by amphiphilic molecules. Questions: What forces contribute to the structural stability of micelles and bilayers? Critical micelle concentration (CMC)? Compelling forces: Attractive: Hydrophobic tails Repulsive: Hydrophilic heads CMC: Qualitatively, as hydrophobicity increases, CMC decreases. Examples: 1 head, 1 tail: CMC = 1 mM 1 head, 2 tails: CMC = 10 mM