blots

A blot is a dark or discolored spot left by a liquid on a surface. Blotting refers to the act of absorbing or removing liquid with an absorbent material, such as blotting paper, and is widely used in writing, printing, and cleaning.

In science, blotting describes a family of laboratory techniques that detect biomolecules after they are separated by size or charge. The most common blotting methods immobilize the target molecules on a membrane for later probing with labeled probes or antibodies. These techniques enable selective identification and, in some cases, quantification.

The major blotting types are named for the biomolecule they detect. Southern blotting detects DNA fragments; Northern blotting detects RNA; Western blotting detects proteins. Less common variants include Southwestern blotting for DNA-binding proteins and Eastern blotting for specific carbohydrate modifications.

The general workflow involves preparing a sample, separating its components by gel electrophoresis, transferring the separated molecules onto a solid membrane, and then incubating the membrane with a detector. The detector typically consists of a labeled nucleic acid probe or an antibody, which binds to the target. Visualization is achieved by enzymatic or chemiluminescent reactions that reveal the bound probe or antibody.

Applications include gene expression analysis, diagnostic testing, forensic analysis, and research into protein expression and modification. Blotting techniques require careful controls and interpretation, as results are often semiquantitative rather than absolute.