Interaction of anionic azo dye and TTAB: cationic surfactant

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Abstract

Interaction between three anionic azo dyes, C.I. Acid Red 14 (AR14), C.I. Acid Red 1 (AR1), C.I. Acid Orange 7 (AO7) and a cationic surfactant tetradecyltrimethylammonium bromide (TTAB) has been investigated using surfactant selective electrode technique. The TTAB selective electrode was constructed and used to determine the concentration of TTAB monomers and also surfactant ions bounded to dyes by electromotive force data. The dye-surfactant complex formation constant, K1, and the standard free energy change, ΔG1º, could be obtained from the experimental data. The results indicate that in the TTAB/AO7 system, where the more hydrophobic dye AO7 is used, the dye-surfactant interactions are stronger than in other systems. The results also indicate that both the electrostatic attractive and the hydrophobic interactions are very important for the formation of the complex between the oppositely-charged dyes and the surfactant. Maximum binding capacities of the dyes and also the degree of binding of the surfactant to the dyes were calculated from the experimental data.

Translated abstract

A interação entre três corantes aniônicos azo: C.I. Vermelho Ácido 14 (AR14), C.I. Vermelho Ácido 1 (AR1), C.I. Laranja Ácido 7 (AO7) e um surfactante catiônico, o brometo de tetradeciltrimetilamônio (TTAB), foi investigada por meio da técnica de eletrodo seletivo para surfactante. O eletrodo seletivo para TTAB foi construído e usado para determinar a concentração de monômeros TTAB e, também, de íons surfactantes ligados aos corantes por medidas de força eletromotriz. A constante de formação do complexo corante-surfactante, K1, e a variação da energia livre de Gibbs, ΔG1º, foram obtidas a partir dos dados experimentais. Os resultados indicaram que no sistema TTAB/AO7, no qual o corante AO7, mais hidrofóbico, é usado, as interações corante-surfactante são mais fortes do que em outros sistemas. Os resultados também indicaram que ambas interações, hidrofóbica e atração eletrostática, são muito importantes para a formação do complexo entre os corantes e o surfactante. A capacidade máxima de ligação dos corantes de cargas opostas e também o grau de ligação do surfactante aos corantes foram calculados a partir dos dados experimentais.

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Reconstitution of respiratory complex I on a biomimetic membrane supported on gold electrodes.

Oscar Gutiérrez-Sanz, David Olea, Marcos Pita … (2014)

For the first time, respiratory complex I has been reconstituted on an electrode preserving its structure and activity. Respiratory complex I is a membrane-bound enzyme that has an essential function in cellular energy production. It couples NADH:quinone oxidoreduction to translocation of ions across the cellular (in prokaryotes) or mitochondrial membranes. Therefore, complex I contributes to the establishment and maintenance of the transmembrane difference of electrochemical potential required for adenosine triphosphate synthesis, transport, and motility. Our new strategy has been applied for reconstituting the bacterial complex I from Rhodothermus marinus onto a biomimetic membrane supported on gold electrodes modified with a thiol self-assembled monolayer (SAM). Atomic force microscopy and faradaic impedance measurements give evidence of the biomimetic construction, whereas electrochemical measurements show its functionality. Both electron transfer and proton translocation by respiratory complex I were monitored, simulating in vivo conditions.