title: 3-Nitrotyrosine quantification methods: Current concepts and future challenges.
abstract: BACKGROUND
  Measurement of 3-nitrotyrosine (3-NT) in biological samples can be used as a biomarker of nitrosative stress, since it is very stable and suitable for analysis. Increased 3-NT levels in biological samples have been associated with several physiological and pathological conditions. Different methods have been described for the detection and quantification of this molecule, such as (i) immunological methods; (ii) liquid chromatography, namely high-pressure liquid chromatography (HPLC)-based methods that use ultraviolet-visible (UV/VIS) absorption, electrochemical (ECD) and diode array (DAD) detection, liquid chromatography-mass spectrometry (LC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS); (iii) gas chromatography, such as gas chromatography-mass spectrometry (GC-MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS).
  
  
  METHODS
  A literature review on nitrosative stress, protein nitration, as well as 3-NT quantification methods was carried out.
  
  
  RESULTS
  This review covers the different methods for analysis of 3-NT that have been developed during the last years as well as the latest advances in this field. Overall, all methods present positive and negative aspects, although it is clear that chromatography-based methods present good sensitivity and specificity. Regarding this, GC-based methods exhibit the highest sensibility in the quantification of 3-NT, although it requires a prior time consuming derivatization step. Conversely, HPLC does not require such derivatization step, despite being not as accurate as GC.
  
  
  CONCLUSIONS
  It becomes clear that all the methods described during this literature review, although accurate for 3-NT quantification, need to be improved regarding both sensitivity and specificity. Moreover, optimization of the protocols that have been described is clearly needed.
authors.affiliation: Ciências Químicas e das Biomoléculas, Centro de Investigação em Saúde e Ambiente, Escola Superior de Tecnologia da Saúde do Porto, Instituto Politécnico do Porto, Portugal.
authors.forename: Dulce
authors.initials: D
authors.lastname: Teixeira
authors.affiliation: Ciências Químicas e das Biomoléculas, Centro de Investigação em Saúde e Ambiente, Escola Superior de Tecnologia da Saúde do Porto, Instituto Politécnico do Porto, Portugal; I3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal.
authors.forename: Rúben
authors.initials: R
authors.lastname: Fernandes
authors.affiliation: Ciências Químicas e das Biomoléculas, Centro de Investigação em Saúde e Ambiente, Escola Superior de Tecnologia da Saúde do Porto, Instituto Politécnico do Porto, Portugal; I3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal.
authors.forename: Cristina
authors.initials: C
authors.lastname: Prudêncio
authors.affiliation: Ciências Químicas e das Biomoléculas, Centro de Investigação em Saúde e Ambiente, Escola Superior de Tecnologia da Saúde do Porto, Instituto Politécnico do Porto, Portugal; I3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal. Electronic address: mav@estsp.ipp.pt.
authors.forename: Mónica
authors.initials: M
authors.lastname: Vieira
mesh_terms: D000818:Animals; D006801:Humans; D011499:Protein Processing, Post-Translational; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis
chemical_list: C002744:3-nitrotyrosine; D014443:Tyrosine
keywords: 3-Nitrotyrosine; Chromatographic method; Immunochemical method; Nitrosative stress; Quantification methods