Micellar effects and analytical applications of nitro substitution in 4-Nitro- N-alkyl-1,8-naphthalimide by cysteine derivatives

V S Martins; E R Triboni; J B S Bonilha; L M Gonçalves; L Mortara; L A C Carvalho; B R Manda; C D Lacerda; F C Meotti; M J Politi; H Chaimovich; I M Cuccovia

doi:10.1016/j.heliyon.2020.e04938

Micellar effects and analytical applications of nitro substitution in 4-Nitro- N-alkyl-1,8-naphthalimide by cysteine derivatives

Heliyon. 2020 Sep 16;6(9):e04938. doi: 10.1016/j.heliyon.2020.e04938. eCollection 2020 Sep.

Authors

Affiliations

¹ Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Brazil.
² Escola de Engenharia de Lorena da Universidade de São Paulo, Departamento de Engenharia Química (DEQUI), Lorena, SP, Brazil.
³ Faculdade de Filosofia Ciências e Letras da Universidade de São Paulo, FFCLRP, Ribeirão Preto, SP, Brazil.

Abstract

The aromatic nucleophilic substitution reactions of the nitro group of 4-Nitro-N-alkyl-1,8-naphthalimides by thiolate anions produce fluorescent derivatives and their rates are strongly accelerated by micelles of hexadecyltrimethylammonium chloride even at low pH. Acceleration factors of this reactions can reach million-fold. As the products are oxidant-insensible, this reaction allows the determination of SH- containing compounds such as cysteine, glutathione or proteins even in oxidative conditions. Limits of detection are as low as 5 × 10^-7 M, ten times lower than the limit for the classic 5,5'-dithiobis-(2-nitrobenzoic) acid method. Moreover, this reaction can be developed at pHs between 6.5 and 7.5 thereby diminishing the rate of spontaneous oxidation of the thiols. In addition, we demonstrated that 4-Nitro-N-alkyl-1,8-naphthalimides can be used to evidence SH groups in peptides, proteins and living cells.

Keywords: Analytical chemistry; Fluorescence assay; Micellar solutions; Organic chemistry; Protein thiols; Thiol levels.