DMSO (dimethyl sulfoxide) stands out as a versatile polar aprotic solvent in biochemistry, widely recognized for its ability to solubilize hydrophobic compounds and enable cryopreservation without disrupting hydrogen bonding networks. Its unique physicochemical profile makes it indispensable in molecular biology, protein chemistry, and pharmaceutical research applications.
Chemical Properties
DMSO, with the molecular formula (CH₃)₂SO, is a colorless, odorless liquid characterized by a melting point of 18.5°C, a boiling point of 189°C, and a density of 1.10 g/mL. The highly polar S=O functional group (dielectric constant ~47) allows DMSO to act as a hydrogen bond acceptor while lacking proton donor capacity.
It is hygroscopic and fully miscible with water as well as most organic solvents. DMSO rapidly penetrates biological membranes, enhancing intracellular delivery of dissolved compounds, while maintaining relatively low nucleophilicity, making it suitable for SN2 reactions and enzymatic assays. Laboratory-grade DMSO (>99.9% purity, molecular biology grade) typically contains less than 0.1% water, minimizing interference in moisture-sensitive experimental protocols.
Biochemical Applications
In molecular biology, DMSO is routinely used at concentrations of 5–10% for cryopreservation of cells, including stem cells and bacteria. By integrating into water networks, it reduces ice crystal formation and limits reactive oxygen species (ROS)-induced damage during freeze–thaw cycles.
In cell culture applications, DMSO solubilizes hydrophobic molecules such as lipids, steroids, and antibiotics, typically at final concentrations ≤0.1–0.5% to avoid cytotoxic effects. It also enhances PCR amplification of GC-rich templates and facilitates the extraction of membrane proteins while preserving structural integrity.
Within protein biochemistry workflows, DMSO supports protein refolding from aggregates and contributes to antibody stabilization in ELISA assays. In metabolic research, it serves as an efficient solvent for hydrophobic intermediates, including cholesterol esters and other lipid-derived molecules.
