Methanol is a fundamental polar protic solvent in biochemistry and molecular biology, prized for its ability to dissolve polar and some non-polar biomolecules while enabling key extraction and precipitation protocols.
Chemical Properties
Methanol (CH3OH) features a tetrahedral structure with sp3 hybridization at carbon and oxygen, yielding a C-O-H bond angle of approximately 108.5° due to oxygen’s lone pair electron repulsion. It boils at 64.7°C, freezes at -97.6°C, and has a density of 0.792 g/mL. Its high water miscibility and dielectric constant of 32.6 support efficient hydrogen bonding interactions in aqueous-organic solvent systems.
As a primary alcohol, methanol can undergo enzymatic oxidation to formaldehyde and formate via alcohol dehydrogenase and aldehyde dehydrogenase pathways. However, laboratory-grade methanol (such as HPLC-grade or ACS-grade solvent) is purified to minimize contaminating by-products that could interfere with sensitive analytical assays.
Biochemical Applications
In lipid biochemistry, methanol is commonly used in the Folch extraction method (chloroform:methanol mixtures such as 2:1 v/v) to disrupt biological membranes and facilitate the isolation of phospholipids and glycolipids for thin-layer chromatography or mass spectrometry analysis.
Methanol is also employed in molecular biology protocols for nucleic acid precipitation, often following ethanol treatment (e.g., 70–80% v/v solutions) to improve DNA and RNA purification prior to next-generation sequencing workflows.
In protein analysis workflows, methanol assists in sample preparation for SDS-PAGE by promoting protein resolubilization and can be used in ELISA buffer formulations to help stabilize antigenic structures without causing significant denaturation.