The effect of the source pressure on the abundance of ions of noncovalent protein assemblies in an electrospray ionization orthogonal time-of-flight instrument

The effect of elevating the pressure in the interface region of an electros pray ionization orthogonal time-of-flight mass spectrometer on the ion inte nsity of different noncovalent protein assemblies has been investigated. El evating the pressure in the interface region generally led to an enhanced d etection of high m/z ions. The optimum pressure was found to be dependent o n the m/z value of the ions. This pressure effect should be carefully addre ssed when relating ion abundance in the mass spectra to solution phase abun dance of noncovalent protein assemblies. Copyright (C) 2001 John Wiley & So ns, Ltd.