Probing the Interaction of Mutiwalled Carbon Nanotubes and Catalase: Mutispectroscopic Approach: CATALASE AND CARBON NANOTUBE INTERACTION

Experimental and Theoretical Approaches to Monitor the Behavior of Bovine Liver Catalase in Interaction with a Binuclear Bismuth Complex

Here, the antioxidant potency of a binuclear Bi(III) complex {[Bi2(μ-ox)(dipic)2(H2O)2 (taa)2].H2O, where ox2- = oxalato, dipic2- = pyridine 2,6-dicarboxylato, and taa = thiourea} was evaluated using the •DPPH assay. It was demonstrated that the Bi complex exhibited a high ability to inhibit DPPH free radicals. The binding mechanism of the complex with bovine liver catalase (BLC) was also investigated, revealing structural and activity changes in the enzyme in the presence of the complex. The catalase activity in the decomposition of hydrogen peroxide increased in the presence of the Bi complex, reaching 39.8% higher than its initial activity at a concentration of 7.77 × 10-6 M. The complex exhibited a relatively high affinity for BLC, with K b values of 3.98, 0.13, and 0.09 × 105 M-1 at 303, 310, and 317 K, respectively. The mechanisms involved in the interaction were hydrogen bonding and van der Waals interactions, as validated through molecular docking simulations. Synchronous fluorescence showed that tryptophan was more affected by enzyme-complex interactions than tyrosine. In addition, a cell viability test using the MTT method revealed that at its highest concentration, the Bi complex caused a decrease in the number of cells below 50% compared to the control, while cisplatin showed negative effects at all concentrations. These findings suggest that the Bi complex has the potential to be developed as a promising candidate for BLC-related therapeutic target therapy.

In vitro comparative cytotoxic assessment of pristine and carboxylic functionalized multiwalled carbon nanotubes on LN18 cells

Multiwalled carbon nanotubes (MWCNTs) have been used in biomedical applications due to their ability to enter the cells. Carboxylic functionalization of MWCNT (MWCNT-COOH) is used to mitigate the toxicity of MWCNTs. Our study focuses on comparing the toxicity of MWCNT and MWCNT-COOH on the neuronal cells, LN18. Concentrations of 5, 10, 20, and 40 µg ml-1 were used for the study, and cytotoxicity was determined at 0, 1, 3, 6, 12, 24, and 48 h of incubation. Cell viability was assessed by Trypan Blue, MTT, and Live dead cell assays, and the oxidative stress produced was determined by reactive oxygen species (ROS) and Lipid peroxidation assays. MWCNT-COOH showed higher cell viability than MWCNT for 20 and 40 µg ml-1 at 24 and 48 h. This was also visually observed in the live dead cell imaging. However, at 48 h, the morphology of the cells appeared more stretched for all the concentrations of MWCNT and MWCNT-COOH in comparison to the control. A significant amount of ROS production can also be observed at the same concentration and time. Viability and oxidative stress results together revealed that MWCNT-COOH is less toxic when compared to MWCNT at longer incubation periods and higher concentrations. However, otherwise, the effect of both are comparable. A concentration of 5-10 µg ml-1 is ideal while using MWCNT and MWCNT-COOH as the toxicity is negligible. These findings can further be extended to various functionalizations of MWCNT for wider applications.

Investigation of the effect for bisphenol A on oxidative stress in human hepatocytes and its interaction with catalase

Bisphenol A (BPA) as a chemical raw material, is widely used in the manufacturing process of daily necessities. It was reported that BPA could induce oxidative stress, and catalase (CAT) can protect the body from oxidative stress. In this paper, the effect of BPA on CAT was carried out in vitro and in vivo. Firstly, we studied the effects of BPA on oxidative stress, cell viability and CAT activity in human hepatocytes, and the results of vitro experiments show that the survival rate of hepatocytes significant decreased along with the increase of BPA concentration. And when the BPA concentration was 100 μM, the hepatocyte survival decreased by 13.2%, ROS levels in the cells increased by 85%. However, the activity of intracellular CAT increased with the increasing concentration of BPA in 24 h. The results of vivo experiments showed that the activity of CAT in the high-dose group decreased by 29.1% compared with the control group. The long-term effects of BPA on rats reduced the CAT activity in liver, which reduced the resistance to oxidative stress. Meanwhile, the interaction mechanism between BPA and CAT at the molecule level was performed via multiple spectra methods and molecular docking, and the results illustrated that the structural change of CAT is mainly due to the strong combination of BPA with the residues of Trp185. In addition, the interaction mechanism between BPA and CAT were hydrophobic and electrostatic effect. This study provided experimental evidence for better understanding the toxicity of BPA.

Binding of paeonol to human serum albumin: a hybrid spectroscopic approach and conformational study

The purpose of this study was to elucidate the binding of paeonol to human serum albumin (HSA) through spectroscopic methods. The fluorescence quenching of HSA by paeonol was a result of the formation of the HSA-paeonol complex with low binding affinity (K = 4.45 × 10(3) M(-1) at 298 K). Thermodynamic parameters (ΔG(°) = -2.08 × 10(4) J · mol(-1), ΔS(°) = 77.9 J · mol(-1) · K(-1), ΔH(°) = 2.41 × 10(3) J · mol(-1), kq = 9.67 × 10(12) M(-1) · s(-1)) revealed that paeonol mainly binds HSA through hydrophobic force following a static quenching mode. The binding distance was estimated to be 1.91 nm by fluorescence resonant energy transfer. The conformation of HSA was changed and aggregates were formed in the presence of paeonol, revealed by synchronous fluorescence, circular dichroism, Fourier transform infrared spectroscopy, three-dimensional fluorescence spectroscopy, and resonance light scattering results.

Insights into the selective binding and toxic mechanism of microcystin to catalase

Microcystin is a sort of cyclic nonribosomal peptides produced by cyanobacteria. It is cyanotoxin, which can be very toxic for plants and animals including humans. The present study evaluated the interaction of microcystin and catalase, under physiological conditions by means of fluorescence, three-dimensional (3D) fluorescence, circular dichroism (CD), Fourier Transform infrared (FT-IR) spectroscopy, and enzymatic reactionkinetic techniques. The fluorescence data showed that microcystin could bind to catalase to form a complex. The binding process was a spontaneous molecular interaction procedure, in which electrostatic interactions played a major role. Energy transfer and fluorescence studies proved the existence of a static binding process. Additionally, as shown by the three-dimensional fluorescence, CD and FT-IR results, microcystin could lead to conformational and microenvironmental changes of the protein, which may affect the physiological functions of catalase. The work provides important insights into the toxicity mechanism of microcystin in vivo.

Underlying the mechanism of vancomycin and human serum albumin interaction: a biophysical study

In the present study, the binding mechanism of vancomycin with human serum albumin (HSA) was determined. Upon addition of vancomycin to HSA, the fluorescence emission was quenched and the binding constant of vancomycin with HSA was found to be 6.05 × 10(3) M(-1) at 295 K, which corresponds to -2.16 × 10(4) J·mol(-1) of free energy. The conformation of HSA was altered upon binding of vancomycin with a decrease in α helix and an increase in β sheets and random coils, suggesting partial unfolding of the secondary structure. Molecular docking experiments found that vancomycin binds strongly with HSA at the hydrophobic pocket through hydrogen bonding and van der Waals interactions. An average binding distance of 4.71 nm has been determined on the basis of the Förster resonance energy theory. It was demonstrated that vancomycin binding to HSA causes protein structural changes.