Fractal nature of polymer conformations

Many biopolymers are heteropolymers. DNA is a heteropolymer consisting of four different types of monomers (nucleotides), while natural proteins are heteropolymers commonly consisting of 20 different types of monomers (amino acids). 

The polymer characteristics, described above— microstructure, architecture, degree of polymerization, chemical composition of heteropolymers— are all fixed during polymerization and cannot be changed without breaking covalent chemical bonds. However, after polymerization, a single flexible macromolecule can adopt many different conformations. A con- 

A polymer s conformation is dictated by its interactions, here illustrated using a chain with 10 ° monomers of size 1 cm and four types of interaction between monomers, (a) Attractive interaction— the chain fits in a classroom, (b) Zero effective interaction—the chain is the size of a campus, (c) Short-range------ 

Moon These astronomical variations of chain sizes make polymers a unique class of materials. 

Another special feature of polymer conformations is that most of them 

---