| gel diffusion precipitin tests in two dimensions | Precipitin test's made in a layer of agar that permits radial diffusion, in both of the horizontal dimensions, of one or both reactants. Double (gel) diffusion in two dimensions (Ouchterlony test, technique, or method) incorporates antigen and antibody solutions placed in separate wells in a sheet of plain agar, permitting radial diffusion of both reactants; this method is widely used to determine antigenic relationships; the bands of precipitate that form where the reactants meet in optimal concentration are of three patterns, referred to as reaction of identity, reaction of partial identity (cross-reaction), and reaction of nonidentity. (05 Mar 2000) |
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| gel diffusion reactions | Precipitin test's in which the immune precipitate forms in a gel medium (usually agar) into which one or both reactants have diffused; generally classified in two types, in one dimension, and in two dimensions. Synonym: gel diffusion reactions. (05 Mar 2000) |
| gel electrophoresis | <molecular biology> Electrophoresis using a gel supporting phase. Usually applied to systems where the gel is based on polyacrylamide. See: electrophoresis. (05 May 1997) |
| gel exclusion chromatography | <investigation> A lab technique, a type of column chromatography, used to separate the components of a mixture by molecular size and to collect the molecules which are larger than a certain size. It is similar to gel filtration, small molecules are slowed or trapped by the pores in the gel beads filling the column, while large molecules, too large to fit into the pores, slide past the beads and get to the bottom of the column first. at this point, the large molecules are collected. Gel exclusion refers to the maximum size of molecule which will fit into the gel bead pores, and this lab technique is used to collect the molecules in the mixture which are larger than, or excluded from, the pores. (09 Oct 1997) |
| gel filtration | <molecular biology> An important method for separating molecules according to molecular size by percolating the solution through beads of solvent permeated polymer that has pores of similar size to the solvent molecules. Unlike a continous filter that retards flow according to molecular size, separation is achieved because molecules that can enter the beads take a longer path (i.e. Are retarded) than those that cannot. Typical gels for protein separation are made from polyacrylamide or from flexible (Sephadex) or rigid (agarose, Sepharose) sugar polymers. The size separation range is determined by the degree of cross linking of the gel. (05 May 1997) |
| gel filtration chromatography | See: gel filtration. (05 Mar 2000) |
| gel retardation assay | A lab technique used to find out if there are proteins binding a fragment of DNA (in a DNA-protein complex) by watching how fast the DNA fragment moves through an electric field and seeing whether it moves slower when a particular protein is also present. (09 Oct 1997) |
| gel structure | Brush heap structure of fibrils giving firmness to hydrocolloids. (05 Mar 2000) |
| gel transfer | Any lab technique used to transfer substances which had been separated using gel electrophoresis from the gel to a membrane for further processing or analysis. For example: any type of blotting. (09 Oct 1997) |
| pharmacopeial gel | A suspension, in a water medium, of an insoluble drug in hydrated form wherein the particle size approaches or attains colloidal dimensions. (05 Mar 2000) |
| chromatography, gel | Chromatography on non-ionic gels without regard to the mechanism of solute discrimination. (12 Dec 1998) |
| colloidal gel | A colloid that has developed resistance to flow because of chemical or thermal change. (05 Mar 2000) |
| polyacrilamide gel | A white, water-soluble, solid gel used as a gel base for electrophoresisand as a thickening or adhesive additive in other industrialapplications. (09 Oct 1997) |
| polyacrylamide gel electrophoresis | Analytical and separative technique in which molecules, particularly proteins, are separated by their different electrophoretic mobilities in a hydrated gel. The gel suppresses convective mixing of the fluid phase through which the electrophoresis takes place and contributes molecular sieving. Commonly carried out in the presence of the anionic detergent sodium dodecylsulphate (SDS). SDS denatures proteins so that noncovalently associating sub unit polypeptides migrate independently and by binding to the proteins confers a net negative charge roughly proportional to the chain weight. See: SDS PAGE. (21 Jun 1999) |
| pulsed-field gel electrophoresis | Gel electrophoresis in which, after electrophoretic migration has begun, the current is briefly stopped and reapplied in a different orientation; allows for the purification of long DNA molecules. Synonym: pulsed-field gel electrophoresis. (05 Mar 2000) |