Increasing charge while preserving noncovalent protein complexes for ESI-MS.
Increased multiple charging of native proteins and noncovalent protein complexes is observed in electrospray ionization (ESI) mass spectra obtained from nondenaturing protein solutions containing up to 1% (vol/vol) m-nitrobenzyl alcohol (m-NBA). The increases in charge ranged from 8% for the 690 kDa alpha(7)beta(7)beta(7)alpha(7) 20S proteasome complex to 48% additional charge for the zinc-bound 29 kDa carbonic anhydrase-II protein. No dissociation of the noncovalently bound ligands/subunits was observed upon the addition of m-NBA. It is not clear if the enhanced charging is related to altered surface tension as proposed in the "supercharging" model of Iavarone and Williams (Iavarone, A. T.; Williams, E. R. J. Am. Chem. Soc.2003, 125, 2319-2327). However, more highly charged noncovalent protein complexes have utility in relaxing slightly the mass-to-charge (m/z) requirements of the mass spectrometer for detection and will be effective for enhancing the efficiency for tandem mass spectrometry studies of protein complexes.
Lomeli
Shirley H
SH
Department of Chemistry and Biochemistry, University of California-Los Angeles, CA 90095, USA.
Yin
Sheng
S
Ogorzalek Loo
Rachel R
RR
Loo
Joseph A
JA
D000818:Animals; D001592:Benzyl Alcohols / Q000737:chemistry; D024402:Carbonic Anhydrase II / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization
D001592:Benzyl Alcohols; D011506:Proteins; D012997:Solvents; D024402:Carbonic Anhydrase II; C046886:3-nitrobenzyl alcohol