Development and application of immobilized surfactant in mass spectrometry-based proteomics

In “bottom-up” proteomics, proteins are first digested into peptides and then characterized by chromatographic separation and mass spectrometry analysis, in which proteolysis has an appreciable influence on the repeatability and reliability of analytical results. To improve recovery and enzymatic efficiency, proteins are often denatured and solubilized with chemical agents such as sodium dodecyl sulphate (SDS), urea (UA), etc. However, surfactant like SDS is difficult to remove from the reacting system and may interfere with protease activity, chromatographic separation of peptides and mass spectrometry analysis. To this end, we have prepared an immobilized surfactant which can preserve the solubilization and denaturation abilities of a surfactant and has the advantage of being easily separated from samples. The denaturation and solubilization capabilities of the newly developed immobilized surfactant were evaluated by comparing the enzymatic hydrolysis efficiencies in the pretreatment of protein samples treated with immobilized surfactant and other common methods. The results showed that the average protein sequence coverage was 42.1% (digested for 1 h), which was 76.89% higher than that of a control experiment (23.8%) in the digestion of a standard protein (BSA) and reached the same denaturation ability as that of heating at 95 °C. Moreover, the immobilized surfactant was further tested in the extraction and digestion of the total protein of HeLa cells. The number of identified proteins resulted in similar levels to those exploited with 0.1% SDS and 8 M UA, both of which are frequently used in lysis buffer, indicating that the immobilized surfactant had a good ability to denature and solubilize proteins. In brief, the immobilized surfactant avoids the shortcomings of UA and SDS and can be utilized in the pretreatment of complex biological samples.