Biomolecular Mass Spectrometry: Applications to Proteins and Peptides - Molecules: Nucleation, Aggregation and Crystallization - page 61

Fig. 3. (a) Fragmentation of a peptide along the backbone with corresponding nomen-
clature of fragments generated. (b) b and y ions are obtained when the charge is retained
on the amino or carboxy terminus fragment, respectively. (Figure used with permission
from Matrix Science Ltd., www.matrixscience.com.)
are around 300 known post-translational modifications (PTMs) found in
proteins, some of which are listed in the Table 1. For more detailed lists,
the reader is referred to other resources (see footnote in Table 1).
MALDI Imaging
In recent times, the application of MS has moved into the realm of MS-
imaging. This is typically based on MALDI-ToF or MALDI-ToF/ToF
instrumentation wherein the laser is used to raster over a whole tissue
sample (Caprioli et al ., 1997; Chaurand et al ., 2006; Andersson et al .,
2008). Each spectrum collected over time not only encodes the chemical
entities present but also the spatial distribution of those entities over the
tissue sample. Through a simple algorithm, it becomes possible to display
the distribution of specific molecules of a particular m / z , e.g. peptides,
thus monitoring fluctuations that may be correlated with disease or any