Document Detail

Influence of droplet size, capillary-cone distance and selected instrumental parameters for the analysis of noncovalent protein-ligand complexes by nano-electrospray ionization mass spectrometry.
MedLine Citation:
PMID:  15386746     Owner:  NLM     Status:  MEDLINE    
It has been suggested in the literature that nano-electrospray ionization (nano-ESI) mass spectrometry better reflects the equilibrium between complex and free protein in solution than pneumatically assisted electrospray ionization (ESI) in noncovalent interaction studies. However, no systematic studies of the effects of ionization conditions have been performed to support this statement. In the present work, different instrumental and sample-derived parameters affecting the stability of noncovalent complexes during analysis by nano-ESI were investigated. In general, increased values of parameters such as drying gas flow-rate, ion-source temperature, capillary tip voltage and buffer concentration lead to a dissociation of ribonuclease A (RNAse)-cytidine 2'-monophosphate (CMP) and cytidine 5'-triphosphate (CTP) complexes. The size of the electrosprayed droplets was shown to be an important issue. Increasing the capillary to cone distance yielded an increased complex to free protein ratio when a hydrophilic ligand was present and the reverse effect was obtained with a hydrophobic ligand. Important in this regard is the degree of sampling of ions originating from late-generation residue droplets, that is, ions present in the droplet bulk. Sampling of these ions increases with longer capillary-cone distance (flight time). Furthermore, when the sample flow-rate was increased by increasing the capillary internal tip i.d. from 4 to 30 microm, a decreased complex to free protein ratio for the RNAse-CTP system was observed. This behavior was consistent with the change in surface to volume ratio for flow-rates between 2 and 100 nl min(-1). Finally, polarity switching between positive and negative ion modes gave a higher complex to free protein ratio when the ligand and the protein had the same polarity.
Kurt Benkestock; Gustav Sundqvist; Per-Olof Edlund; Johan Roeraade
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of mass spectrometry : JMS     Volume:  39     ISSN:  1076-5174     ISO Abbreviation:  J Mass Spectrom     Publication Date:  2004 Sep 
Date Detail:
Created Date:  2004-09-30     Completed Date:  2005-02-10     Revised Date:  2005-11-17    
Medline Journal Info:
Nlm Unique ID:  9504818     Medline TA:  J Mass Spectrom     Country:  England    
Other Details:
Languages:  eng     Pagination:  1059-67     Citation Subset:  IM    
Department of Structural Chemistry, Biovitrum AB, SE-112 76 Stockholm, Sweden.
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MeSH Terms
Carrier Proteins / chemistry,  metabolism
Fatty Acid-Binding Proteins
Ions / chemistry
Myoglobin / chemistry,  metabolism
Particle Size
Proteins / chemistry*,  metabolism*
Ribonuclease, Pancreatic / chemistry,  metabolism
Spectrometry, Mass, Electrospray Ionization / instrumentation*,  methods*
Reg. No./Substance:
0/Carrier Proteins; 0/Electrolytes; 0/Fatty Acid-Binding Proteins; 0/Ions; 0/Ligands; 0/Myoglobin; 0/Proteins; EC, Pancreatic

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