Polyethylene glycol (PEG) is a versatile and widely utilized polymer that has found extensive applications in various scientific, industrial, and medical fields. Comprising repeating ethylene glycol units, PEG possesses unique properties that make it valuable for a diverse range of applications.

Chemical Structure and Characteristics: Polyethylene glycol is a polyether compound with the general formula H-(O-CH₂-CH₂)ₙ-OH, where "n" represents the number of ethylene glycol units. Its structure imparts water solubility and a lack of toxicity, contributing to its widespread use in biological and pharmaceutical applications. The molecular weight of PEG can vary significantly, influencing its physical and chemical properties.

Applications in Biomolecular Research: In biomolecular research, PEG is commonly employed for protein crystallization, where it acts as a precipitant, aiding in the formation of well-ordered crystals suitable for X-ray diffraction analysis. Additionally, PEG is utilized in the purification of biomolecules through a process known as PEG precipitation or PEG fractionation. In this context, PEG induces the precipitation of proteins, nucleic acids, or other biomolecules, facilitating their separation from solution.

Medical and Pharmaceutical Applications: PEG's biocompatibility and low toxicity have led to its use in various pharmaceutical formulations. It is a key ingredient in certain drug delivery systems, enhancing the solubility and stability of drugs. PEGylation, the covalent attachment of PEG to therapeutic molecules, has been employed to extend circulation times, reduce immunogenicity, and improve the overall pharmacokinetics of drugs.