Accurate quantification of basal plasma levels of 3-nitrotyrosine and 3-nitrotyrosinoalbumin by gas chromatography-tandem mass spectrometry.

Measurement of 3-nitro-L-tyrosine (NO(2)Tyr) and protein-related 3-nitro-L-tyrosine in human plasma is associated with numerous methodological problems which result in highly divergent basal plasma levels often ranging within two orders of magnitude. Recently, we have described an interference-free GC-tandem MS-based method for NO(2)Tyr which yielded the lowest basal plasma NO(2)Tyr levels reported thus far. This method was extended to quantify protein-associated 3-nitrotyrosine and in particular 3-nitrotyrosinated albumin (NO(2)TyrALB) in human plasma.