Repulsion, interactions between polymer-bearing

The force-distance profiles Al, A2 appear to show the relaxed, or quasi-equilibrium limit for the interaction between the mica plates bearing the PEO in the good solvent conditions of the present study. The adsorbed layer thicknesses 6 are then about half the value of D at which onset of repulsion (A curves) is first noted. 6 thus corresponds to some 3Rg for both polymers in the present investigation, a value comparable to that obtained for hydrodynamic layer thickness of PEO absorbed on latex particles in water, for similar molecular weights, from light scattering studies. 

Polymers made of identical units often adopt helical structures for symmetry reasons Each monomer then has the same orientation and undergoes the same interactions. However, the protein backbone bears different side chains which have their own requirements forming hydrogen bonds with others, shuiming the aqueous environment or, conversely, seeking water, and so forth. By interacting with each other or with the solvent, they limit the free rotation of the single bonds of the polypeptide backbone. Steric or electrostatic repulsions between side chains may hinder the helical structure formation. 

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