Figure 1 of Allison, Mol Vis 2006; 12:655-672.


Figure 1. Methodology for identifying peptides and determining their relative abundance

Peptides are isolated from control and thyroid hormone (TH)-treated retinas. Control and treated peptide pools are separately labeled with isotope-coded affinity tag (ICAT) reagents. The ICAT reagents contain biotin, which allows the peptides to be isolated via avidin affinity. The peptides from TH-treated retinas are labeled with ICAT reagents that are 9 Da heavier than the reagents used to label peptides from control retina. The heavy and light isotopes of the ICAT label differ only in that the heavy isotope contains 9 deuterium ions while the light isotope contains hydrogen atoms. This allows the peptides to be identified in mass spectrometry, where their peaks appear 9 Da apart. Identification of these doublets also allows the relative abundance of each peptide to be determined (Figure 2 is an example of this type of spectrum). Concurrently, the peptides are sequenced by mass spectrometry (Figure 2) and searched against protein databases to determine the protein the peptide came from.

(197 K)

Allison, Mol Vis 2006; 12:655-672 <http://www.molvis.org/molvis/v12/a74/>
©2006 Molecular Vision <http://www.molvis.org/molvis/>
ISSN 1090-0535