Diethylene glycol (DEG) is a colorless, hygroscopic polyether alcohol used sparingly in biochemistry as a solvent and humectant, particularly in stabilizing viscous formulations or cryopreserving sensitive biomolecules due to its low toxicity relative to other glycols.
Chemical Properties
Diethylene glycol ((HOCH₂CH₂)₂O) consists of two ethylene glycol units linked by an ether bond, yielding a molecular weight of 106.12 g/mol, a boiling point of 245°C, and a density of 1.118 g/mL at 20°C. Fully miscible with water, ethanol, and acetone (viscosity 35.7 cP, dielectric constant ~31.7), it exhibits low volatility (vapor pressure 0.01 mmHg) and a freezing point of -6.5°C. Its hydrogen-bonding capacity enhances the solubility of polar compounds without inducing aggressive dehydration.
Biochemical Applications
In protein biochemistry, 5–20% DEG stabilizes enzymes or antibodies during lyophilization by replacing water within hydrogen-bond networks, thereby preventing aggregation in storage buffers for ELISA kits. In molecular biology, low concentrations (<10%) act as a PCR enhancer for GC-rich templates, improving amplification yield by reducing secondary structure formation. DEG also facilitates the solubilization of lipids or detergents during membrane protein extraction without the phase separation issues associated with shorter-chain glycols. As an alternative cryoprotectant to glycerol, DEG can maintain >85% cell viability in bacterial stocks stored at -80°C by promoting cytoplasmic vitrification.
