Surfactant effects on protein structure examined by electrospray ionization mass spectrometry

Abstract

Electrospray ionization mass spectrometry (ESI-MS) has proven to be a useful tool for examining noncovalent complexes between proteins and a variety of ligands. It has also been used to distinguish between denatured and refolded forms of proteins. Surfactants are frequently employed to enhance solubilization or to modify the tertiary or quaternary structure of proteins, but are usually considered incompatible with mass spectrometry. A broad range of ionic, nonionic, and zwitterionic surfactants was examined to characterize their effects on ESI-MS and on protein structure under ESI-MS conditions. Solution conditions studied include 4% acetic acid/50% acetonitrile/46% H 2 0 and 100% aqueous. Of the surfactants examined, the nonionic saccharides, such as n-dodecyl-P-D-glucopyranoside, at 0.1 Vo to 0.01% (w/v) concentrations, performed best, with limited interference from chemical background and adduct formation. Under the experimental conditions used, ESI-MS performance in the presence of surfactants was found to be unrelated to critical micelle concentration. It is demonstrated that surfactants can affect both the tertiary and quaternary structures of proteins under conditions used for ESI-MS. However, several of the surfactants caused significant shifts in the charge-state distributions, which appeared to be independent of conformational effects. These observations suggest that surfactants, used in conjunction with ESI-MS, can be useful for protein structure studies, if care is used in the interpretation of the results.Keywords: conformation; denaturation; detergent; electrospray; mass spectrometry; surfactant Surfactants play a significant role in protein chemistry with primary applications ranging from solubilization and stabilization of proteins to disaggregation of protein complexes and denaturation (Neugebauer, 1990(Neugebauer, , 1992Bollag & Edelstein, 1991). Some surfactants can disrupt protein higher order structure, whereas others are used as aids in protein refolding. They are employed in both gel and capillary electrophoresis and enhance protein and peptide recoveries from synthetic membranes employed in electroblotting and in electroelution of proteins from gels (Fernandez et al., 1994). Membrane-bound proteins, in particular, require surfactant treatment for solubilization. Abbreviotiom: CMC, critical micelle concentration; ESI, electrospray ionization; ESI-MS, electrospray ionization mass spectrometry; MALDI, matrix-assisted laser desorption/ionization; NP40, Nonidet P a , CHAPS, 3-(3-cholamidopropyl)dimethylammonio-I-propane sulfonate; CTAB, cetyl trimethylammonium bromide; LDAO, laurel dimethylamine oxide; n-dodecyl glucoside, n-dodecyl-0-D-glucopyranoside; n-hexylglucoside, n-hexyl-0-D-glucopyranoside; octyl glucoside, octyl-fl-D-glucopyranoside; octyl thioglucoside, I-S-octyl-fi-~-thioglucopyranoside.Matrix-assisted laser desorption/ionization or electrospray ionization have demonstrated molecular weight determinations for proteins greater than 100 kDa (Fenn et al., 1989;Smith et al., 19...

Sequential and Exhaustive Ionization of Analytes with Different Surface Activity by Probe Electrospray Ionization

“…For example, the nonionic detergent, Triton X100, is widely used for the solubilization and characterization of the proteins. As mentioned before, in normal ESI the presence of surfactants such as Triton X100 in a protein sample solution leads to severe suppression of less solvophobic proteins [4]. If the sequential electrospray of analytes from more-surface-active analytes to less active ones occurs, the suppression effect could be largely moderated in PESI.…”

“…Surfactants are frequently employed to enhance solubilization or to modify the tertiary or quaternary structure of proteins [4]. For example, the nonionic detergent, Triton X100, is widely used for the solubilization and characterization of the proteins.…”

“…; solvophobic) contaminants, as these compounds actively provide ions towards the droplet surface [3]. Nonionic-based surfactants such as Triton X100 always form adducts with proteins and also suppress the analyte ion signals [4]. Supramolecular system-based extraction/separations and HPLC techniques are successful in the removal of detergents [5] but they are time-consuming, tedious, and sometimes can produce carryover/memory effects [6].…”

Less is More: Membrane Protein Digestion Beyond Urea–Trypsin Solution for Next-level Proteomics

“…Inheriting industrial-grade detergents such as SDS and Triton X-100, historically applied for cheap price, proteomics has suffered huge penalties in quality and cost. Using ESI MS experiments of intact model protein solutions (infusion and flow injection), a pioneering 1994 study reported several nonionic, zwitterionic, and anionic detergents tolerable by ESI MS, in acetic acid/ acetonitrile/H 2 O spray (top 7: n-dodecyl glucoside, n-hexyl glucoside, CHAPS, cholate, and three equally scored DDM, OG, and octyl thioglucoside), and in H 2 O spray (top 5: ndodecyl glucoside, n-hexyl glucoside, OG, n-octyl sucrose, and n-dodecyl sucrose) (71).…”

Neuroproteomics tools in clinical practice

“…A C C E P T E D M A N U S C R I P T There is no universal detergent that can serve all the needs of proteomic research, and the choice of detergent selection is determined experimentally to suit the type of work to be carried out. However, the usage of detergents compromises with the MS analysis step to some extent due to-their interference in ionization step causing the shifts in charge-state distribution in ESI-MS [42]. Hence their removal prior to MS-analysis is essential, which can be achieved by different techniques such as dialysis, hydrophobic absorption, ultrafiltration, precipitation, gel filtration or solid phase extraction ( Table 1).…”