User:
John Yates III, professor of chemical physiology, The Scripps Research Institute, La Jolla, Calif.
Project:
Identifying insulin-signaling targets in Caenorhabditis elegans
Problem:
Yates needed a rapid and accurate way to measure the change in abundance of three specific targets over time and growth temperature.
Solution:
Yates uses single-reaction monitoring (SRM). "You can do this with other methods but it takes longer, and SRM also provides the most accurate measures," he says. SRM measures the abundance of a given parent ion based on the abundance of its specific collision-induced fragmentation products. Such transitions of parent ion to fragment are unique. For example, several peptides might weigh 2,326.6 Da, but only one will produce a fragment ion of 1,242.3 Da. Then, quantify by comparing the number of diagnostic fragmentation ions to a labeled reference protein extract.
SRM's precision, Yates says, stems from its two levels of filtration. Only one selected ion ...
