File Download
There are no files associated with this item.
Supplementary
-
Citations:
- Appears in Collections:
Conference Paper: Radical-Mediated Peptide Tyrosine Nitration In Vacuo: Experimental Evidence and Theoretical Examination
Title | Radical-Mediated Peptide Tyrosine Nitration In Vacuo: Experimental Evidence and Theoretical Examination |
---|---|
Authors | |
Issue Date | 2016 |
Citation | The 23rd IUPAC Conference on Physical Organic Chemistry (ICPOC-23), Sydney, Australia, 3-8 July 2016 How to Cite? |
Abstract | Protein tyrosine nitration (PTN)—a hallmark of post-translational modification of proteins under nitrative stress in vivo—modification is believed to occur regioselectively and site-specifically at diverse local sequences with no observed consensus modification motif.1 The mechanistic details governing the site-specificity of the ortho-tyrosine nitration are largely unknown. Herein, the mechanism of radical-mediated PTN has been elucidated in detail at the molecular level using an integrated approach combining gas phase synthesis of prototypical tyrosine-containing peptide radical cations, ion–molecule reactions with nitrogen dioxide, isotopic labelling MS experiments, and DFT calculations at the B3LYP/6-31++G** level of theory. First, π-centered molecular radical cationic tyrosine-containing peptides were generated in situ through collision-induced intramolecular one-electron transfer oxidation of copper(II)–peptide complexes In Vacuo.2,3 The representative radical cationic tyrosine-containing tetrapeptide was mass-selected, trapped, and reacted with •NO2. Recombination of •NO2 with radical cationic peptide led to a substantial yield of a stable closed-shell nitrated product. Our experimental and theoretical investigations into radical-mediated tyrosine nitration revealed the necessity for phenoxyl radical formation prior to the production of distinct 3-nitrotyrosine (3-NT) products, which are influenced by the location of the radical site and the tautomerization barriers for radical and proton mobility; 3,4 a two-step mechanism, involving the generation of phenoxyl radical intermediates with viable isomerization
barriers (<10 kcal mol–1) and concerted proton rearrangement prior to the formation of the stable
closed-shell ortho-nitration product of the tyrosyl residue, has been determined unambiguously. The
spin state of the phenoxyl radical governs the regioselectivity of the ortho-tyrosine nitration (3-NT).
To better understand the site-specific formation of endogenous PTNs, the fundamental factors
governing the site-specificity of the 3-NT have been investigated using computationally tractable
prototypical dityrosyl-containing peptides that mimic the local topological characteristics of peptides found in PTNs in vitro from a M. fascicularis model of cerebral ischemia; 5 these nitrated peptides have been validated and shortlisted as potential selectivity determinants for the model peptides in their subsequent gas phase PTN reactions; selective tyrosine nitrations have been verified in several other instances of prototypical dityrosyl-containing peptides. A crucial aspect of the formation of the site-specific nitrated product ions is that they are likely preceded by favorable interconversion barrier(s) to generate phenoxyl radical intermediate structures prior to the formation of distinct 3-NT products; the exact site of tyrosyl nitration also depends on the local sequence; the types and locations of the essential neighboring residues and their proximity to the tyrosyl residue appear to significantly influence the competition between the isomerization and the site-specific phenoxyl radical formation.
References:
1. Radi, R. Acc. Chem. Res. 2013, 46, 550-559.
2. Turecek, F.; Julian, R. R. Chem. Rev. 2013, 113, 6691-6733.
3. Laskin J. ; Yang Z.; Chu I. K. J. Am. Chem. Soc. 2008, 130, 3218-3230.
4. Chu I. K.; Zhao J.; Xu M.; Siu S. O.; Hopkinson A. C.; Siu K. W. M. J. Am. Chem. Soc. 2008, 130, 7862-7872.
5. Quan Q., Szeto S. S. W.; Law C. H.; Zhang Z.; Wang Y.; Chu I. K. Anal. Chem. 2015, 87, 10015- 10024 |
Persistent Identifier | http://hdl.handle.net/10722/296285 |
DC Field | Value | Language |
---|---|---|
dc.contributor.author | Chu, IK | - |
dc.contributor.author | Lai, CK | - |
dc.contributor.author | Mu, X | - |
dc.contributor.author | Tang, WK | - |
dc.contributor.author | Siu, CK | - |
dc.date.accessioned | 2021-02-19T07:27:24Z | - |
dc.date.available | 2021-02-19T07:27:24Z | - |
dc.date.issued | 2016 | - |
dc.identifier.citation | The 23rd IUPAC Conference on Physical Organic Chemistry (ICPOC-23), Sydney, Australia, 3-8 July 2016 | - |
dc.identifier.uri | http://hdl.handle.net/10722/296285 | - |
dc.description.abstract | Protein tyrosine nitration (PTN)—a hallmark of post-translational modification of proteins under nitrative stress in vivo—modification is believed to occur regioselectively and site-specifically at diverse local sequences with no observed consensus modification motif.1 The mechanistic details governing the site-specificity of the ortho-tyrosine nitration are largely unknown. Herein, the mechanism of radical-mediated PTN has been elucidated in detail at the molecular level using an integrated approach combining gas phase synthesis of prototypical tyrosine-containing peptide radical cations, ion–molecule reactions with nitrogen dioxide, isotopic labelling MS experiments, and DFT calculations at the B3LYP/6-31++G** level of theory. First, π-centered molecular radical cationic tyrosine-containing peptides were generated in situ through collision-induced intramolecular one-electron transfer oxidation of copper(II)–peptide complexes In Vacuo.2,3 The representative radical cationic tyrosine-containing tetrapeptide was mass-selected, trapped, and reacted with •NO2. Recombination of •NO2 with radical cationic peptide led to a substantial yield of a stable closed-shell nitrated product. Our experimental and theoretical investigations into radical-mediated tyrosine nitration revealed the necessity for phenoxyl radical formation prior to the production of distinct 3-nitrotyrosine (3-NT) products, which are influenced by the location of the radical site and the tautomerization barriers for radical and proton mobility; 3,4 a two-step mechanism, involving the generation of phenoxyl radical intermediates with viable isomerization barriers (<10 kcal mol–1) and concerted proton rearrangement prior to the formation of the stable closed-shell ortho-nitration product of the tyrosyl residue, has been determined unambiguously. The spin state of the phenoxyl radical governs the regioselectivity of the ortho-tyrosine nitration (3-NT). To better understand the site-specific formation of endogenous PTNs, the fundamental factors governing the site-specificity of the 3-NT have been investigated using computationally tractable prototypical dityrosyl-containing peptides that mimic the local topological characteristics of peptides found in PTNs in vitro from a M. fascicularis model of cerebral ischemia; 5 these nitrated peptides have been validated and shortlisted as potential selectivity determinants for the model peptides in their subsequent gas phase PTN reactions; selective tyrosine nitrations have been verified in several other instances of prototypical dityrosyl-containing peptides. A crucial aspect of the formation of the site-specific nitrated product ions is that they are likely preceded by favorable interconversion barrier(s) to generate phenoxyl radical intermediate structures prior to the formation of distinct 3-NT products; the exact site of tyrosyl nitration also depends on the local sequence; the types and locations of the essential neighboring residues and their proximity to the tyrosyl residue appear to significantly influence the competition between the isomerization and the site-specific phenoxyl radical formation. References: 1. Radi, R. Acc. Chem. Res. 2013, 46, 550-559. 2. Turecek, F.; Julian, R. R. Chem. Rev. 2013, 113, 6691-6733. 3. Laskin J. ; Yang Z.; Chu I. K. J. Am. Chem. Soc. 2008, 130, 3218-3230. 4. Chu I. K.; Zhao J.; Xu M.; Siu S. O.; Hopkinson A. C.; Siu K. W. M. J. Am. Chem. Soc. 2008, 130, 7862-7872. 5. Quan Q., Szeto S. S. W.; Law C. H.; Zhang Z.; Wang Y.; Chu I. K. Anal. Chem. 2015, 87, 10015- 10024 | - |
dc.language | eng | - |
dc.relation.ispartof | The 23rd IUPAC Conference on Physical Organic Chemistry (ICPOC-23), 2016 | - |
dc.title | Radical-Mediated Peptide Tyrosine Nitration In Vacuo: Experimental Evidence and Theoretical Examination | - |
dc.type | Conference_Paper | - |
dc.identifier.email | Chu, IK: ivankchu@hkucc.hku.hk | - |
dc.identifier.authority | Chu, IK=rp00683 | - |
dc.identifier.hkuros | 261921 | - |