15N Chemically Induced Dynamic Nuclear Polarization (15N-CIDNP) Investigations of the Peroxynitrite Decay and Nitration of N-Acetyl-L-tyrosine
✍ Scribed by Manfred Lehnig; Michael Kirsch
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- German
- Weight
- 270 KB
- Volume
- 89
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
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.