Thermodynamics of ligand binding on dilute polymer molecules in solution: Complementary monomers and oligomers on polynucleotides

Previous work on the thermodynamics of small systems is applied to the binding of ligands on dilute polymer molecules in solution, and especially to the binding of complementary monomers and oligomers on polynucleotides. Topics emphasized are: binding isotherms, optical melting curves, calorimetric melting and mixing studies, role of the activity of the ligand, quasi phase transitions, the polymer phase diagram, and interrelations between these subjects. The one‐dimensional Ising model (linear and circular) is used to illustrate some of the thermodynamics. An Appendix shows how the ligand activity in salt solution may be found from vapor pressure osmometry measurements.