The invention relates to an apparatus for processing planar gel layers or slab gels and, more particularly, to an apparatus for staining and destaining electrophoresis slab gels and for examining the destained slab gels.
Electrophoresis is a technique for separating charged molecules of a sample such as protein or DNA on the basis of differences in electrical charge or molecular weight under the influence of an electric field. In general, a polymer material such as polyacrylamide, agar, agarose, or cellulose acetate is used to contain and support the sample. The ionic components of the sample separate or migrate through the support medium (gel) under the influence of the electric field until the elements reach equilibrium. The ionic component separation is not visible to the eye. Consequently, the gel must be stained and fixed with an appropriate stain. The stain permeates the entire gel rendering it a dense opaque color and the surplus stain which is not held by the ionic hands must be removed before the bands themselves become visible. Destaining may be done electrophoretically by passing direct current through the gel or by diffusion. The subsequently destained gel is examined by optical densitometry or other methods, such as photography and can be shrunk and dried for permanent record.
U.S. Pat. No. 4,357,174 issued to Rushbrook et al, on Nov. 2, 1982 discloses a diffusion destainer having a stain absorbing material contained in a hollow housing and disposed within an open, that is topless, destaining container. A drawback of the destaining container is that only a single slab gel can be destained therein. Additionally, the slab is unsupported in the container making handling of the slab difficult during the staining and destaining process. Furthermore, some components of the staining and destaining solutions, such as acetic acid, methanol, ethanol, butanol or isopropanol form vapors which can readily escape from the open container causing an unpleasant and possibly harmful odor.
U.S. Pat. No. 4,391,689 issued to Golias on July 5, 1983 shows an automated electrophoresis and staining apparatus for processing a gel attached to a MYLAR (trademark) sample plate. The sample plate with the gel attached is frictionally supported within a plate holder rack. Gels used in such an apparatus are extremely thin, of the order of a few microns. Such an apparatus is unsuitable for processing gels having a thickness of the order of about 0.4 mm to about 3.0 mm which are not bound to a supportive backing.
U.S. Pat. No. 3,930,880 issued to Hoefer on Jan. 6, 1976 discloses a slab gel diffusion destainer for gels having a thickness in the millimeter range. Subsequent to electrophoresis and staining, the slab gel is supported on a flexible mesh which contacts the slab gel on both sides. The mesh is rolled into a cylindrical form and inserted into a slab holding tube and confined therein by placing end caps on each end of the tube. The tube is disposed within a cylindrical container and a suitable washing liquid is circulated through the interior of the destainer. A problem with this apparatus is that rolling the slab gel in the mesh tends to damage or distort the slab gel. Furthermore, diffusion of the stain into the overlapped portion of the gel can be non-uniform.
With the exception of the destainer described in the above-referenced U.S. Pat. No. 4,357,174, the apparatus described herein are expensive and not well suited for the handling of slab gels.