HIGH-RESOLUTION ONE-DIMENSIONAL ELECTROPHORETIC SEPARATION AND PARTIAL CHARACTERIZATION OF HUMAN HEAD HAIR PROTEINS

A reproducible, rapid procedure for the extraction, labelling and sepa ration of human hair proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) has been developed. Hair proteins were extracted in 8 M urea, containing 0.2 M mercaptoethanol, followed by sonication. Extracts were neutralised with Tris and incubated with eit her labelled (C-14) or unlabelled iodoacetic acid to S-carboxymethylat e cysteine groups. Proteins were separated on 12.5% SDS-polyacrylamide gels and gels stained with Coomassie Brilliant Blue and/or silver nit rate to reveal major protein bands. Gels were then treated with a fluo rographic agent, dried and autoradiographed to reveal major sites of S -carboxymethylation. A given gel was scanned by laser densitometry aft er Coomassie and/or silver stain to quantitate the protein content of each major protein zone. An autoradiogram of the same gel was scanned to estimate the cysteine content of each major zone. In this way it wa s possible to partially characterise rapidly and reproducibly many dif ferent protein zones in different individual samples on one gel at the same time. By calculating the ratio of autoradiograph absorbance to C oomassie Blue absorbance, protein zones could be assigned to four diff erent categories, viz: very high cysteine (VHC) proteins, high cystein e (HC) proteins, low cysteine (LC) proteins and very low cysteine (VLC ) proteins. The method described is reproducible, rapid and inexpensiv e enough to be suitable for mass screening. Overall the results were m ore informative than previously reported one-dimensional separations a nd indeed this technique may well be more suited to forensic and/or po pulation investigations than the much more laborious and time-consumin g two dimensional techniques.