Biophysical influence of isocarbophos on bovine serum albumin: spectroscopic probing

Boosting one-step degradation of shrimp shell waste to produce chitin oligosaccharides at smart nanoscale enzyme reactor with liquid-solid system

Chitin oligosaccharides (CTOS) possess potential applications in food, medicine, and agriculture. However, lower mass transfer and catalytic efficiency are the main kinetic limitations for the production of CTOS from shrimp shell waste (SSW) and crystalline chitin. Chemical or physical methods are usually used for pretreatment to improve chitinase hydrolysis efficiency, but this is not eco-friendly and cost-effective. To address this challenge, a chitinase nanoreactor with the liquid-solid system (BcChiA1@ZIF-8) was manufactured to boost the one-step degradation of SSW and crystalline chitin. Compared with free enzyme, the catalytic efficiency of BcChiA1@ZIF-8 on colloidal chitin was significantly improved to 142 %. SSW and crystalline chitin can be directly degraded by BcChiA1@ZIF-8 without any pretreatments. The yield of N, N'-diacetylchitobiose [(GlcNAc)2] from SSW and N-acetyl-D-glucosamine (GlcNAc) from crystalline chitin was 2 times and 3.1 times than that of free enzyme, respectively. The reason was that BcChiA1@ZIF-8 with a liquid-solid system enlarged the interface area, increased the collision frequency between enzyme and substrate, and improved the large-substrates binding activity of chitinase. Moreover, the biphasic system exhibited excellent stability, and the design showed universal applicability. This strategy provided novel guidance for other polysaccharide biosynthesis and the conversion of environmental waste into carbohydrates.

Revealing the mechanistic interactions of profenofos and captan pesticides with serum protein via biophysical and computational investigations

Profenofos (PF) and captan (CT) are among the most utilized organophosphorus insecticides and phthalimide fungicides, respectively. To elucidate the physicochemical and influential toxicokinetic factors, the mechanistic interactions of serum albumin and either PF or CT were carried out in the current study using a series of spectroscopy and computational analyses. Both PF and CT could bind to bovine serum albumin (BSA), a representative serum protein, with moderate binding constants in a range of 103-104 M-1. The bindings of PF and CT did not induce noticeable BSA's structural changes. Both pesticides bound preferentially to the site I pocket of BSA, where the hydrophobic interaction was the main binding mode of PF, and the electrostatic interaction drove the binding of CT. As a result, PF and CT may not only induce direct toxicity by themselves, but also compete with therapeutic drugs and essential substances to sit in the Sudlow site I of serum albumin, which may interfere with the pharmacokinetics and equilibrium of drugs and other substances causing consequent adverse effects.

Spectroscopic demonstration of sinapic acid methyl ester complexes with serum albumins

The methyl ester of sinapic acid (MESA) is a molecule with confirmed antioxidant properties. It is important to establish whether it can be transported across humans and animals. Therefore, we investigated MESA interactions with serum albumins, namely, human serum albumin (HSA), bovine serum albumin (BSA), rabbit serum albumin (RSA), and sheep serum albumin (SSA). Experiments were performed in a pH range from 5.9 to 10.7 using absorption and fluorescence techniques. It was found that MESA formed complexes with every albumin in the entire pH range under examination, which was confirmed by the appearances of new absorption and fluorescence complex bands. Fluorescence intensities were much higher (up to 20 times) and lifetimes were up to 340 times as compared to those for unbound MESA. The quenching experiments at pH 7.4 showed that the stoichiometry for every albumin was 1 : 1; the binding constant was the highest for HSA, which reached 52 000 M⁻¹. The obtained results suggested that MESA preferred the hydrophobic binding sites in albumins. The analysis of the fluorescence spectra and fluorescence lifetimes showed two possibly different binding sites in BSA, RSA, and SSA as well as three binding sites in HSA.

Known antioxidant, methyl ester of sinapic acid (MESA) can interact with serum albumins.

Biochemical and toxicological investigation of karanjin, a bio-pesticide isolated from Pongamia seed oil

Karanjin, a furanoflavonol from Pongamia pinnata L is used in agricultural practices for its pesticidal, insecticidal and acaricidal activities. It is commercially available as a bio-pesticide targeting a wide variety of pests. The present study was intended to evaluate the biochemical interactions of karanjin with bovine serum albumin (BSA) and study its toxicological effects on mammalian and bacterial cell lines. Karanjin bound to BSA at a single site with a dissociation constant of 19.7 μM. Evaluation of BSA-karanjin interactions at three different temperatures indicated the involvement of static mode of quenching. Binding experiments in the presence of warfarin and computational docking analysis indicated that karanjin bound closer to the warfarin binding site located in the Subdomain IIA of BSA. Using Förster resonance energy transfer analysis the distance between TRP 213 of BSA and karanjin was found to be 20 Å. Collective results from synchronous fluorescence spectra analysis, differential scanning calorimetry, and circular dichroism analysis indicated that binding of karanjin induced conformational changes in the secondary structure of BSA. Karanjin exhibited low toxicity against human cervical cancer cells and normal mouse fibroblast L929 cells and modestly inhibited the growth of B. subtilis and E. coli cells. The data presented in this study provides insights for understanding the binding interactions of karanjin with BSA and its possible toxicological effects on mammalian cell lines and bacteria.

Enantioselective analysis and degradation of isofenphos-methyl in vegetables by liquid chromatography-tandem mass spectrometry

The enantioselective degradation of isofenphos-methyl in cowpea, cucumber, and pepper under field conditions was investigated to elucidate the enantioselective environmental behaviors of this pesticide. The concentrations of the enantiomers were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The degradation rates of isofenphos-methyl enantiomers were the fastest in cowpea, followed by cucumber and pepper, with half-lives ranging from 1.48 to 8.06 days. The enantioselective degradation of isofenphos-methyl was characterized by calculating and comparing the values of enantiomer fraction (EF) and enantiomeric selectivity (ES). The degradation rates and enantioselectivities of isofenphos-methyl were different for the three vegetables. (R)-(-)-isofenphos-methyl was degraded faster than (S)-(+)-isofenphos-methyl in cowpea and cucumber, whereas (S)-(+)-isofenphos-methyl underwent preferential degradation in pepper. These results could serve as a reference for the study of enantioselective behavior of isofenphos-methyl in plants and further food safety evaluation, where the enantiomeric differences should be considered in the risk assessment.

In vitroinhibition ofHelicobacter pyloriand interaction studies of lichen natural products with jack bean urease

The interaction between lichen metabolites and jack bean urease was investigated by molecular spectroscopy at pH 7.4 and kinetics assay.