9780521516358book.pdf

or collision cells are required. The limitation is sensitivity, which decreases with each MS experiment, although the claimed re ...

of the ions is through a sector of the circular poles of the magnet, hence the term magnetic sector. Figure 9.9 shows several po ...

9.3.7 Plasma desorption ionisation Plasma desorption ionisation mass spectrometry(PDMS) was the first mass spectrom- eter to be ...

Sample concentration for MALDI Maximum sensitivity is achieved in MALDI–TOF if samples are diluted to a particular concentration ...

(b) Laser beam +20 kV Sample plate Variable grid (a) Plume of matrix and sample ions 337 nm Ground grid Fig. 9.10MALDI ionisatio ...

9.3.9 Delayed extraction In the first MALDI–TOF instruments, the ions in the plume of material generated by the laser pulse were ...

places could have different energies. This energy spread (and fragmentation occurring during this initial extraction period) usu ...

Example 2PEPTIDE MASS DETERMINATION (I) Question A peptide metabolite and an enzyme digest of it were analysed by a combination ...

The reflector Areflector(orreflectron) is a type ofion mirrorthat provides higher resolution in MALDI–TOF. The reflector increas ...

instrument that includes the facility for both linear and reflectron modes of ion collection. The reflectron improves resolution ...

Linear detector Reflector detector Ion gate (b) In the linear mode Reflector + (^0) + Ion gate 0 (c) In the PSD mode 0 + + ( ...

Sequencing peptides by PSD analysis in MALDI–TOF is less straightforward (and in a large percentage of experiments is unsuccessf ...

mass resolution;> 106 is observable with most instruments. The instrument also allows tandem MS to be carried out. The ions c ...

9.4 Detectors 9.4.1 Introduction The ions from the mass analyser impinge on a surface of a detector where the charge is neutrali ...

(a) Orbitrap High vacuum Fourier Mass transform spectrum ESI Linear ion trap C-trap Quadrupoles (and octopoles) (b) Central and ...

9.4.2 Electron multiplier and conversion dynode Electron multipliersare used as detectors for many types of mass spectrometers. ...

gels, it can be used to identify positions of modified or labelled bases that might not be picked up by the Sanger dideoxy seque ...

analyser where an ion of a particularm/zis selected (but not detected). This ion then enters thecollision celland collides with ...

9.5.3 Comparison of MS and Edman sequencing Edman degradation (Section 8.4.3) to obtain the complete sequence of a protein is un ...

residue and post-translational modification to N-terminal trimethylalanine and dimethylproline also occur. In the case of recomb ...