Macromolecules as a Dynamic Cooperative System

Long-chain macromolecules are dynamic systems consisting of many particles hence, a broad spectrum of motions is possible on various spatial and time scales. The parameters of these motions exhibit various dependences on the temperature and viscosity of the solvent and various sensitivities to conformational changes. 

rotatory and translational diffusion of the macromolecule as a whole occurs. Furthermore, a spectrum of intramolecular motions exists they may be divided into relatively large-scale motions accompanied by a change in the size and shape of the whole macromolecule and small-scale local motions localized within the range of one or several units. When the dependence of local relaxation properties of polymer homologs on the molecular mass (which is observed sometimes) is con- 

The parameters of the rotatory and translational diffusion of the macromolecule as a whole and those of intramolecular large-scale motions depend on the size and shape of the macromolecule, on its hydrodynamic permeability and on the possible solvation of the solvent. (It is known that the latter factor should be taken into account in the study of compact protein globules in water.) 

In contrast, the parameters of local motions are very sensitive to the local conformational microstructure of the polymer chain and to the interactions of units located at a large distance apart along the chain contour but close to each other in space (kinetic volume effects). The parameters of local motions also depend on the external viscosity of the solvent and internal viscosity of the polymer chain 

One of the major problems of the theory of intramolecular local mobility or kinetic flexibility lies in the establishment of the principal mechanism of mobility for the macromolecules of a given chemical structure and constitution and of local conformational microstructure. The question arises, which of the elementary acts leads to the ability of individual parts of the macromolecule for changing their shape during definite time intervals characteristic of a certain class of motions 38-148) 

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