No abstract

The attractive potential of natural superoxide dismutase (SOD) in the fields of medicine and functional food is limited by its short half-life in circulation and poor permeability across the cell membrane. The nanoparticle form of SOD might overcome these limitations. However, most preparative methods have disadvantages, such as complicated operation, a variety of reagents—some of them even highly toxic—and low encapsulation efficiency or low release rate. The aim of this study is to present a simple and green approach for the preparation of SOD nanoparticles (NPs) by means of co-incubation of Cu/Zn SOD with glucose. This method was designed to prepare nanoscale aggregates based on the possible inhibitory effect of Maillard reaction on heating-induced aggregation during the co-incubation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results indicated that the Maillard reaction occurred during the co-incubation process. It was found that enzymatically active NPs of Cu/Zn SOD were simultaneously generated during the reaction, with an average particle size of 175.86 ± 0.71 nm, and a Zeta potential of −17.27 ± 0.59 mV, as established by the measurement of enzymatic activity, observations using field emission scanning electron microscope, and analysis of dynamic light scattering, respectively. The preparative conditions for the SOD NPs were optimized by response surface design to increase SOD activity 20.43 fold. These SOD NPs showed storage stability for 25 days and better cell uptake efficacy than natural SOD. Therefore, these NPs of SOD are expected to be a potential drug candidate or functional food factor. To our knowledge, this is the first report on the preparation of nanoparticles possessing the bioactivity of the graft component protein, using the simple and green approach of co-incubation with glucose, which occurs frequently in the food industry during thermal processing.

As a complex reaction, biological consequences of the Maillard reaction (MR) on dietary proteins need to be deciphered. Despite previous studies on the structural and antigenic properties of ovalbumin (OVA) by MR, associated changes induced by specific MR intermediates and their downstream products are largely unknown. This study focused on the impacts of glycation by α-dicarbonyl compounds (α-DCs), intermediates of MR and precursors of advanced glycation end-products (AGEs), on the structural and IgE-binding properties of ovalbumin (OVA) under simulated heating. Methylglyoxal (MGO), glyoxal (GO), and butanedione (BU) were selected as typical α-DCs to generate glycated OVA with different AGE-modifications (AGE-Ms). The results showed that reactions between OVA and α-DCs generated OVA-AGE with various degrees of modification and conformational unfolding, and the reactivity of α-DCs followed the order GO > MGO > BU. Depending on the precursor type, the levels of 10 specific AGEs were verified, and the amounts of total AGEs increased with heating temperature and α-DC dosage. Compared to native OVA, glycated OVA showed reduced IgE-binding levels but with sRAGE-binding ligands, the extent of which was associated with the contents of total AGEs and Nε-carboxymethyllysine, and changes in certain protein conformational structures. High-resolution mass spectrometry further identified different AGE-Ms on the Lys and Arg residues of OVA, confirming variations in the glycation sites and their associations with the immunoreactive epitopes of OVA under different conditions.

Mercury, as a highly poisonous pollutant, poses a severe threat to the global population. However, the removal of Hg 0 can only be carried out at below 100 °C due to the weak binding of the adsorbent. Herein, a series of carbon-based materials with different coordination environments and atomic dispersion of single-site manganese were prepared, and their elemental mercury removal performance was systematically investigated. It was demonstrated that the coordination environment around manganese determines its electronic structure and size, thus affecting its affinity with mercury. The obtained best adsorbents atomically dispersed Mn with atom size near 0.2 nm, achieves high Hg 0 removal efficiency and over 13 mg/g Hg 0 adsorption capacity at 200 °C. And the SO 2 resistance performance of single atoms (∼0.2 nm) is much better than clusters (∼1− 2 nm) because of its high selectivity, that the effect of SO 2 is only 3%. Density functional theory (DFT) reveals that Mn with four-nitrogen atoms (Mn−N 4 -CO) is more active than other number nitrogen coordination materials. Moreover, the presence of carboxyl groups around manganese also promotes affinity for Hg 0 . This work might shed new light on the enhancement of Hg 0 affinity in carbon-based materials and the rational design of the coordination structure of the tunable Hg 0 activities.

The difference of urine crystallites under 1000 nm in 10 patients with urolithiasis and 10 healthy subjects with no history of urolithiasis was comparatively studied with the nanoparticle size analyzer. By comparing the differences of intensity-autocorrelation curve, polydispersity index (PDI), Zeta potential, and relative error of average diameter of the two kinds of urine crystallites, it was concluded that the urine crystallites of healthy subjects were more stable than those of patients. The urine crystallites of healthy subjects had a narrower size distribution from 100 nm to 350 nm and a better dispersion (PDI < 0.3). However, the urine crystallites of patients with urolithiasis had a wider distribution from dozens of nanometers to 1000 nm and a worse dispersion (PDI > 0.5). The best processing method for urine crystallites detection was found: after antisepticising and protein-coagulating with formaldehyde, the urine was diluted with distilled water of the same volume, then filtrated through a micropore film of 3 microm, and the filtrate was centrifugalized at 4000 rpm for 15 minutes. This method can remove the cell fragments and macromolecular substances in the urine without affecting the detection of the urine crystallites under 1000 nm. The results were consistent with those obtained by transmission electron microscope (TEM).