SYNTHESIS OF 3-NITRO-L-[H-2(3)]TYROSINE FOR USE AS AN INTERNAL STANDARD FOR QUANTIFICATION OF 3-NITRO-L-TYROSINE BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

3-Nitro-L-tyrosine is produced in vitro and in vivo by the nitration o f tyrosine and tyrosine residues in proteins. Plasma 3-nitro-L-tyrosin e has been suggested as an index of oxidative damage in living organis ms that depend on nitrating species. For use in the quantitative deter mination of 3-nitro-L-tyrosine in biological fluids by gas chromatogra phy-mass spectrometry (GC-MS) we describe the chemical synthesis of 3- nitro-L-[H-2(3)]tyrosine by nitration of commercially available L-[H-2 (4)]tyrosine by nitrate and sulphuric acid. GC-MS analysis revealed a H-2 isotopic purity of about 9%. The isolated reaction product did not contain any detectable amounts of L-[H-2(4)]tyrosine. The utility of 3-nitro-L-[H-2(3)]tyrosine as an internal standard for the quantitativ e analysis of 3-nitro-L-tyrosine by CC-MS is shown.