SimuLab 3: Polymers

The behavior of a polymer in the solvent is very important in biology and chemistry. All important biological molecules such as DNA, RNA, Proteins and Lipids are polymers which contain many small similar monomers: nucleotides in case of DNA and RNA, aminoacids in case of proteins and hydrocarbons in case of lipids. The polymers in the cell are surrounded by water which contains different ions and other small molecules. The monomers of the polymer can be hydrophobic or hydrophilic, they attract to water or repulse from them. Very small changes in temperature or quality of solvent can produce dramatic effects on the shape and size of the biological proteins. For example the proteins can fold into compact native state at which they can function as a nanoscale robots. Thus it is very important to understand the behavior of the polymers in the solvent.

The movie polymer shows the behavior of the polymer chain with the temperature.


You will be able to:

a) Study the behavior of polymers with respect to the temperature;

b) Find the similarities and differences between the behavior of a Gas and a polymer;

c) Characterize the polymer collapse by the size of the monomer.

Answers to the question

Simulab 3

A2.27: This graph has a step at temperature 0.537. The value of this step is the latent heat of crystallization which value is 1722. As the number of atoms is 1000, the latent heat per atom is 1.722. See Fig .2.7.

A2.28: For T > 2.5 the slope is 0.6. Below the q-point it is 1/3, above 0.6 and 1/2 at the q-point.

Figure 2.7: Radius of Gyration RG as function of the temperature. The q-point, that is the critical temperature from unfolding to folding state is marked with dashed line.