Blotting is a common laboratory procedure in which biological molecules in a gel matrix are transferred onto nitrocellulose paper for further scientific analysis. The biological molecules transferred in this process are DNA fragments, RNA fragments, or proteins.
All blotting procedures begin with a standard process called gel electrophoresis. During this step, DNA, RNA, or proteins are loaded on to an agarose or acrylamide gel (that functions like a molecular sieve) and are then run through an electric field.
Gels are loaded with a mixture of many differently sized molecules. When pulled through the gel, they will separate into separate pools on the basis of their size. After the molecules have been fractionated on the gel, they are ready for transfer to the nitrocellulose paper.
Transfer is initiated when the gel is retrieved from the electrophoresis apparatus and the nitrocellulose paper is carefully laid on top of the gel. The objective now is to transfer the bands of molecules found in the gel over to the nitrocellulose paper.
There are two basic ways the actual transfer, or blotting, is carried out. One method takes a "sandwich" of gel and nitrocellulose paper and places it in a special apparatus that sets up an electric field running perpendicular to the band as preserved in the gel. This pulls the bands of molecules out of the gel, and they are immediately absorbed onto the nitrocellulose paper.
Millpore's Immobilon-P Blotting Sandwiches consist of one sheet of Immobilon-P transfer membrane with two sheets of chromatography-grade blotting filter paper.
Immobilon-P transfer membrane is a 0.45-µm polyvinylidene fluoride (PVDF) membrane for binding proteins transferred from a variety of gel matrices.
The pre-cut blotting filter paper used in the blotting sandwiches is also available separately for laboratories using transfer methods that require more than two sheets of filter paper.