A VERTICAL MICROSYSTEM FOR DISCONTINUOUS ELECTROPHORESIS OF INSECT TISSUE PROTEINS USING THIN SHEETS OF POLYACRYLAMIDE GEL

Proteins extracted from individual pairs of salivary glands or other larval tissues of Sciara coprophila (Diptera) were separated in a vertical microsystem for discontinuous electrophoresis using thin sheets of polyacrylamide gel cast in multiple layers of varying pore size. After electrophoresis at 150 volts for 40 min, gels were stained ( a) for total proteins with Coomassie brilliant blue, ( b) for glycoproteins with the periodic acid-Schiff reaction, ( c) for lipoproteins with Sudan black B or ( d) for nonspecific esterases with fast blue RR as coupler and α-naphthol acetate as substrate. Sequential application of these reactions to individual gel sectors permitted direct comparisons of protein profiles for 15-20 different samples of tissue extracts carried on a single gel sheet in adjacent lanes and thus subjected to identical conditions of electrophoresis. Representative photographs and densitometric scans are presented to show the suitability of thin gel sheets for autoradiography and for both qualitative and quantitative evaluation of tissue-specific differences in patterns of protein banding found for salivary gland cells, the gastric ceca, or the hemolymph of individual Sciara larvae sacrificed at particular stages of fourth instar development. Innovative details of methodology are presented, including the use of a microspectrophotometer to scan electropherograms of insect proteins and several types of human blood serum.