Conformational angles

Another simplified model is the freely jointed or random flight chain model. It assumes all bond and conformation angles can have any value with no energy penalty, and gives a simplified statistical description of elasticity and average end-to-end distance. 

The rotational isomeric state (RIS) model assumes that conformational angles can take only certain values. It can be used to generate trial conformations, for which energies can be computed using molecular mechanics. This assumption is physically reasonable while allowing statistical averages to be computed easily. This model is used to derive simple analytic equations that predict polymer properties based on a few values, such as the preferred angle... 

In this way each amino acid residue is associated with two conformational angles and y. Since these are the only degrees of freedom, the conformation of the whole main chain of the polypeptide is completely determined when the ([) and y angles for each amino acid are defined with high accuracy. 

The conformation of the whole main chain of a protein is determined by two conformational angles, phi (0) and psi (i(f), for each amino acid. Only certain combinations of these angles are allowed because of steric hindrance between main-chain atoms and side-chain atoms, except for glycine. 

The diameter D of lube (a, b) and the conformation angle 6 with equal dc-C given by. 

Helical Parameters and Conformation Angles in (1 — 4)-linked Polysaccharides... 

The side chains in the latter are flexible disaccharides on account of poor-quality diffraction patterns, their tentative molecular structures are known only from computer modeling.1" On the other hand, well-defined crystal structures are available for gellan and welan, and they can be correlated with the physical properties of the polysaccharides the details are presented here. Their conformation angles are listed in Table VI. 

---