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  • Origin of supercharging in electrospray ionization of noncovalent complexes from aqueous solution.

Origin of supercharging in electrospray ionization of noncovalent complexes from aqueous solution.

Journal of the American Society for Mass Spectrometry (2009-08-18)
Harry J Sterling, Evan R Williams
ABSTRACT

The use of m-nitrobenzyl alcohol (m-NBA) to enhance charging of noncovalent complexes formed by electrospray ionization from aqueous solutions was investigated. Addition of up to 1% m-NBA can result in a significant increase in the average charging of complexes, ranging from approximately 13% for the homo-heptamer of NtrC4-RC (317 kDa; maximum charge state increases from 42+ to 44+) to approximately 49% for myoglobin (17.6 kDa; maximum charge state increases from 9+ to 16+). Charge state distributions of larger complexes obtained from heated solutions to which no m-NBA was added are remarkably similar to those containing small amounts of m-NBA. Dissociation of the complexes through identical channels both upon addition of higher concentrations of m-NBA and heating is observed. These results indicate that the enhanced charging upon addition of m-NBA to aqueous electrospray solutions is a result of droplet heating owing to the high boiling point of m-NBA, which results in a change in the higher-order structure and/or dissociation of the complexes. For monomeric proteins and small complexes, the enhancement of charging is lower for heated aqueous solutions than from solutions with m-NBA because rapid folding of proteins from heated solutions that do not contain m-NBA can occur after the electrospray droplet is formed and is evaporatively cooled.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
3-Nitrobenzyl alcohol, 98%
Supelco
3-Nitrobenzyl alcohol, suitable for mass spectrometry (MS), ≥99.5%