Figure 2.

Schematic of PEG Impact on Crystallization Space

(A) PEGs are long-chain polymers where the number of ethylene oxide units typically varies but yields an average molecular weight for a specific PEG (for instance, PEG 4000 is a mixture of PEGs with an average MW of 4,000 g/mol). PEGs have many degrees of freedom of rotation.

(B) The effect of PEGs (represented by red ovoids) on two macromolecules (represented by two purple spheres) is to enhance the interaction between the molecules through an excluded volume effect. PEGs affect macromolecular solubility, increasing the potential for crystallization to occur.