Already, Coon and Hebert have performed six simultaneous analyses using the new technique; but it could actually do batches of 20, Coon says.
Key to the original doubling-up process was inserting a "tag" into the amino acids that gives the proteins a slightly different mass. The tags are isotopes chemically identical atoms that have different masses.
To prepare two samples, one would receive an amino acid containing common isotopes, and the other special, heavier isotopes. The result proteins that are chemically identical but have different masses can easily be identified in a mass spectrometer.
The new journal report by Coon and Hebert describes a way to use amino acids built from a broader range of isotopes that would be expected to have identical mass, but do not because some of their mass has been converted to energy to hold the atomic nuclei together. Without this energy, the positively charged proteins would repel each other and the atomic nucleus would be destroyed. The tiny loss of mass due to this conversion to binding energy can be detected in the new, ultra-precise mass spectrometers that are now installed in several labs on campus.
The mass difference in the new technique is more than 1,000 times below the mass differences in the existing doubled-up technique, but it is enough to count and identify proteins from six and, theoretically, 20 samples at once. The researchers applied for a patent last fall and assigned the rights to the Wisconsin Alumni Research Foundation.
|Contact: Joshua Coon|
University of Wisconsin-Madison