Blotting

Blotting is a group of laboratory techniques used to transfer and immobilize biomolecules onto a solid support for detection and analysis. The most common targets are DNA, RNA, and proteins. The methods share a general workflow: separate the molecules by size or charge, transfer them from a gel onto a membrane, and probe the immobilized material with labeled probes or antibodies to reveal the presence of specific sequences or proteins.

The best-known blotting variants are Southern blotting for DNA (developed by E. M. Southern in 1975), Northern blotting for RNA (developed in 1977 by Alwine, Kemp, and Weinstock), and Western blotting for proteins (developed by Towbin and colleagues in 1979). There are additional specialized blotting techniques for other biomolecules or interactions, such as methods targeting DNA-binding proteins or specific carbohydrate patterns, but Southern, Northern, and Western blotting remain the foundational forms. Transfers can be accomplished by capillary action (capillary blotting) or by applying an electric field across the gel (electroblotting) onto membranes such as nitrocellulose or PVDF.

Typical workflow begins with sample preparation and separation by gel electrophoresis, followed by transfer to the membrane. The membrane is then blocked to prevent nonspecific binding and probed with a labeled nucleic acid or antibody that binds the target. Detection methods include autoradiography, chemiluminescence, or fluorescence, enabling visualization and, in some cases, quantification of the biomolecule of interest.

Applications include gene mapping, expression analysis, diagnostics, and research in genetics and proteomics. Limitations include that blotting is often semi-quantitative, relatively time-consuming, and requires substantial material; more sensitive or high-throughput methods may be preferred for some modern analyses.