Potential Protein Toxicity of Synthetic Pigments: Binding of Poncean S to Human Serum Albumin

Abstract

Using various methods, e.g., spectrophotometry, circular dichroism, and isothermal titration calorimetry, the interaction of poncean S (PS) with human serum albumin (HSA) was characterized at pH 1.81, 3.56, and 7.40 using the spectral correction technique, and Langmuir and Temkin isothermal models. The consistency among results concerning, e.g., binding number, binding energy, and type of binding, showed that ion pair electrostatic attraction fixed the position of PS in HSA and subsequently induced a combination of multiple noncovalent bonds such as H-bonds, hydrophobic interactions, and van der Waals forces. Ion pair attraction and H-bonds produced a stable PS-HSA complex and led to a marked change in the secondary structure of HSA in acidic media. The PS-HSA binding pattern and the process of change in HSA conformation were also investigated. The potentially toxic effect of PS on the transport function of HSA in a normal physiological environment was analyzed. This work provides a useful experimental strategy for studying the interaction of organic substances with biomacromolecules, helping us to understand the activity or mechanism of toxicity of an organic compound.

Interaction Between Nanoparticulate Anatase TiO2 and Lactate Dehydrogenase

“…It can be seen from Fig. 1 we also speculate that the changes of enzyme activity might be due to the interaction of nanoparticulate anatase TiO 2 with the enzymes, i.e., nanoparticulate anatase TiO 2 either might bind to the enzymes or compete with essential metal ions, or LDH might be absorbed on nanoparticulate anatase TiO 2 from the interaction force/bond such as electric charge attraction, hydrogen bond, and van der Waals force between LDH and TiO 2 [20,21], resulting in the changes of the enzyme structure and its function. On the other hand, nanoparticulate anatase TiO 2 entering the body might cause the changes of gene expression and regulation of LDH, resulting in the changes of enzyme activities, which need further research.…”

“…Apparently, the addition of nanoparticulate anatase TiO 2 to LDH led to a significant reduction in the fluorescence intensity, indicating that the binding of nanoparticulate anatase TiO 2 to LDH quenched the intrinsic fluorescence of LDH. On the other hand, the consequent quenching of LDH fluorescence intensity might be related to the structure change of Trp residue that touch on nanoparticulate anatase TiO 2 surface via hydrogen bond, and then resulting from the structural twist of Trp residue side group [20,21]. It was clear that nanoparticulate anatase TiO 2 could linearly quench the fluorescence emission spectra in a low concentration, which made it clear that nanoparticulate anatase TiO 2 could entirely integrate into LDH in a low concentration.…”

The effects of copper ions on the catalytic degradation of azo dye acid chrome dark blue

“…The solutions were measured at 541 and 569 nm against water, respectively. By means of spectra correction technique [18], the binding number (J) of ACDB on Cu 2+ and the effective fraction (K) of ACDB to Cu 2+ were calculated. The solutions in the optical cell were returned completely into the flasks.…”

“…The spectra correction technique was a new spectral method to study the interaction of ligands and some metal ions or proteins [18,25]. In this work, it was used to study the interaction of ACDB and Cu 2+ .…”

“…In this work, it was used to study the interaction of ACDB and Cu 2+ . The effective fraction (K) of ACDB bound to Cu 2+ and its binding ratio (J) were calculated [18], as shown in Fig. 8.…”