Tartrazine [HSA]

Interaction of the food colorant tartrazine with human hemoglobin was studied using multispectroscopic and microcalorimetric techniques to gain insights into the binding mechanism and thereby the toxicity aspects. Hemoglobin spectrum showed hypochromic changes in the presence of tartrazine. Quenching of the fluorescence of hemoglobin occurred and the quenching mechanism was through a static mode as revealed from temperature dependent and time-resolved fluorescence studies. According to the FRET theory the distance between beta-Trp37 of hemoglobin and bound tartrazine was evaluated to be 3.44 nm. Synchronous fluorescence studies showed that tartrazine binding led to alteration of the microenvironment around the tryptophans more in comparison to tyrosines. 3D fluorescence and FTIR data provided evidence for conformational changes in the protein on binding. Circular dichroism studies revealed that the binding led to significant loss in the helicity of hemoglobin. The esterase activity assay further complemented the circular dichroism data. Microcalorimetric study using isothermal titration calorimetry revealed the binding to be exothermic and driven largely by positive entropic contribution. Dissection of the Gibbs energy change proposed the protein-dye complexation to be dominated by non-polyelectrolytic forces. Negative heat capacity change also corroborated the involvement of hydrophobic forces in the binding process. (C) 2016 Elsevier B.V. All rights reserved.

This work presents a study of the removal of leaf green dye by photocatalysis using TiO2 in suspension and immobilized on polyethylene terephthalate (PET) plates. SEM, diffuse reflectance and XRD analyses confirmed the presence of the catalyst on the PET support and FTIR analyses proved that the catalyst remained on the support after treatment. Preliminary tests with UV-C/TiO2(susp.)/H2O2 system showed a degradation of 97% of dyes in 360min. In the kinetic study, 98% degradation was obtained for the UV-C/TiO2(susp.)/H2O2 system and 90% for the UV-C/TiO2 (PET)/H2O2 system in 240min. This result demonstrated the efficiency of employing TiO2 (PET) in the process of the contaminant when compared with TiO2(susp.). The reaction kinetics was fitted to a pseudo-first-order model, obtaining a kinetic constant of 0.0164 in the UV-C/TiO2(susp.)/H2O2 treatment and 0.0094min(-1) in the UV-C/TiO2(PET)/H2O2 treatment. Kinetic data for the dye solution for the UV-C/TiO2(susp.)/H2O2 and UV-C/TiO2 (PET)/H2O2 systems were modeled using neural networks to predict contaminant concentration over time. In the phytotoxicity assays, the IC50 of the treated samples increased in the UV-C/TiO2(PET)/H2O2 and UV-C/TiO2(susp.)/H2O2 systems compared to the initial dye solution, suggesting a decrease in dye toxicity. The UV-C/TiO2(PET)/H2O2 system exhibited more than 70% of organic matter (COD) removal and 52% of mineralization (TOC). TiO2 immobilization exhibited degradation rates close to those of the TiO2 suspension system.