Sarkosyl: A milder detergent than SDS for identifying proteins with moderately high hyperstability using gel...

Sodium dodecyl sulfate (SDS) is a detergent used as a strong denaturant of proteins in gel electrophoresis. It has previously been shown that certain hyperstable, also known as kinetically stable, proteins are resistant to SDS and thus require heating for their denaturation in the presence of SDS. Because of its high denaturing strength, relatively few proteins are resistant to SDS thereby limiting the current use of SDS-PAGE for identifying hyperstable degradation-resistant proteins. In this study, we show that sarkosyl, a milder detergent than SDS, is able to identify proteins with moderately high kinetic stability that lack SDS-resistance. Our assay involves running and subsequently comparing boiled and unheated protein samples containing sarkosyl, instead of SDS, on PAGE gels and identifying subsequent differences in protein migration. Our results also show that sarkosyl and SDS may be combined in PAGE experiments at varying relative percentages to obtain semi-quantitative information about a protein's kinetic stability in a range inaccessible by probing through native- or SDS-PAGE. Using protein extracts from various legumes as model systems, we detected proteins with a range of protein stability from nearly SDS-resistant to barely sarkosyl resistant.