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15 N Chemically Induced Dynamic Nuclear Polarization ( 15 N‐CIDNP) Investigations of the Peroxynitrite Decay and Nitration of N ‐Acetyl‐ L ‐tyrosine
Author(s) -
Lehnig Manfred,
Kirsch Michael
Publication year - 2006
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200690203
Subject(s) - cidnp , chemistry , peroxynitrite , nitration , radical , adduct , tyrosine , stereochemistry , photochemistry , superoxide , organic chemistry , enzyme , biochemistry
Abstract During the decay of ( 15 N)peroxynitrite (O 15 NOO − ) in the presence of N ‐acetyl‐ L ‐tyrosine (Tyrac) in neutral solution and at 268 K, the 15 N‐NMR signals of 15 NO $\rm{_2^ - }$ and 15 NO $\rm{_3^ - }$ show emission ( E ) and enhanced absorption ( A ) as it has already been observed by Butler and co‐workers in the presence of L ‐tyrosine (Tyr). The effects are built up in radical pairs [CO $\rm{_3^{\bullet - } }$ , 15 NO $\rm{_2^\bullet }$ ] S formed by OO bond scission of the ( 15 N)peroxynitriteCO 2 adduct (O 15 NOOCO $\rm{_2^ - }$ ). In the absence of Tyrac and Tyr, the peroxynitrite decay rate is enhanced, and 15 N‐CIDNP does not occur. This is explained by a chain reaction during the peroxynitrite decay involving N 2 O 3 and radicals NO . and NO $\rm{_2^\bullet }$ . The interpretation is supported by 15 N‐CIDNP observed with ( 15 N)peroxynitrite generated in situ during reaction of H 2 O 2 with N ‐acetyl‐ N ‐( 15 N)nitroso‐ dl ‐tryptophan (( 15 N)NANT) at 298 K and pH 7.5. In the presence of Na 15 NO 2 at pH 7.5 and in acidic solution, 15 N‐CIDNP appears in the nitration products of Tyrac, 1‐( 15 N)nitro‐ N ‐acetyl‐ L ‐tyrosine (1‐ 15 NO 2 ‐Tyrac) and 3‐( 15 N)nitro‐ N ‐acetyl‐ L ‐tyrosine (3‐ 15 NO 2 ‐Tyrac). The effects are built up in radical pairs [Tyrac . , 15 NO $\rm{_2^\bullet }$ ] F formed by encounters of independently generated radicals Tyrac . and 15 NO $\rm{_2^\bullet }$ . Quantitative 15 N‐CIDNP studies show that nitrogen dioxide dependent reactions are the main if not the only pathways for yielding both nitrate and nitrated products.