Mass spectrometry

Electrospray mass spectrometry

An PE Sciex API365 LC/MS/MS instrument (PE Sciex, Concord, Canada) was used to record electrospray mass spectra. The instrument is equipped with an IonSpray ion source. The nitrogen required for turbo pumps and as curtain- and nebuliser gas was obtained from a Whatman Nitrogen Generator (Whatman, Havervill, MA, USA). The API365 is a triple quadrupole instrument and has a mass range from 30 to 3,000 $m/z$. The instrument could be controlled using the software Mass Chrom 1.2 provided by the manufacturer.

MALDI mass spectrometry

MALDI-TOF-MS has been performed using a PerSeptive Biosystems Voyager-DE RP BioSpectrometry Workstation (PerSeptive Biosystems, Framigham, MA, USA) MALDI-TOF-MS instrument. The instrument is capable of delayed extraction and has a flight path of 1.3 m in linear mode and 2.0 m in reflectron mode. The instrument is equipped with a nitrogen laser ($\lambda$ = 337 nm, pulse: 3 ns) and could be controlled using the software provided by the manufacturer.