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

• Published in: Heliyon Vol. 6; no. 9; p. e04938
• Main Authors: Martins, V.S., Triboni, E.R., Bonilha, J.B.S., Gonçalves, L.M., Mortara, L., Carvalho, L.A.C., Manda, B.R., Lacerda, C.D., Meotti, F.C., Politi, M.J., Chaimovich, H., Cuccovia, I.M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2020; Elsevier
• Subjects: Analytical chemistry; Fluorescence assay; Micellar solutions; Organic chemistry; Protein thiols; Thiol levels; Analytical chemistry; Organic chemistry; Micellar solutions; Thiol levels; Fluorescence assay; Protein thiols
• ISSN: 2405-8440; 2405-8440
• DOI: 10.1016/j.heliyon.2020.e04938

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