Structural and biochemical characterization of active sites mutant in human inorganic pyrophosphatase.

Inorganic pyrophosphatases (PPases) are enzymes that catalyze the conversion of inorganic pyrophosphate (PPi) into phosphate (Pi). Human inorganic pyrophosphatase 1 (Hu-PPase) exhibits high expression levels in a variety of tumors and plays roles in cell proliferation, apoptosis, invasion and metastasis, making it a promising prognostic biomarker and a target for cancer therapy. Despite its widespread presence, the catalytic mechanism of Hu-PPase in humans remains inadequately understood. The signature motif amino acid sequence (DXDPXD) within the active sites of PPases is preserved across different species. In this research, an enzymatic activity assay revealed that mutations led to a notable reduction in enzymatic function, although the impact of the four amino acids on the activity of the pocket varied. To investigate the influence of these residues on the substrate binding and enzymatic function of PPase, the crystal structure of the Hu-PPase-ED quadruple mutant (D116A/D118A/P119A/D121A) was determined at 1.69 Å resolution. The resulting structure maintained a barrel-like shape similar to that of the wild-type, albeit lacking Mg2+ ions. Molecular docking analysis demonstrated a decreased ability of Hu-PPase-ED to bind to PPi. Further, molecular dynamics simulation analysis indicated that the mutation rendered the loop of Mg2+ ion-binding residues less stable. Therefore, the effect on enzyme activity did not result from a change in the gross protein structure but rather from a mutation that abolished the Mg2+-coordinating groups, thereby eliminating Mg2+ binding and leading to the loss of enzyme activity.

Dual mimic enzyme properties of Fe nanoparticles embedded in two-dimensional carbon nanosheets for colorimetric detection of biomolecules.

The development of novel nanozymes is of great importance for the efficient analysis of biomolecules such as H2O2, glucose, and antioxidants in the diagnosis of some diseases. Herein, novel nanozymes based on Fe nanoparticles (NPs) encapsulated in 2D carbon nanosheets (denoted as Fe@CNs) were constructed and employed in the field of biosensing. Notably, Fe@CNs have intrinsic dual mimic enzyme properties. The colorless colorimetric substrate 3,3',5,5'-tetramethylbenzidine (TMB) can be oxidized by Fe@CNs as oxidase- and peroxidase-like nanozymes, respectively. The generation of the oxidation state TMB (oxTMB) resulted from the presence of reactive oxygen species (ROS) which were produced by the catalytic decomposition of the dissolved oxygen or H2O2. Thus, a simple colorimetric biosensor was proposed to detect glutathione (GSH), H2O2, and glucose. In addition, the Fe@CN-based nanozymes also have excellent reusability in enzymatic catalysis. After separating from the sensing systems, Fe@CNs can be reused in other catalytic processes. This colorimetric method could be used as a universal sensing platform for the detection of antioxidants and H2O2-related bioanalysis. This work broadens the application of novel nanozymes in biosensing.

The pH-sensitive sorption governed reduction of Cr(VI) by sludge derived biochar and the accelerating effect of organic acids.

Reduction coupling immobilization is one of the most commonly adopted strategies for the remediation of Cr(VI) contamination. Biochar is a carbon-rich material with abundant active functional groups for sorption and reduction reactions. In previous reports, phytomass derived biochars and organic functional groups have been emphasized, while the performance of sludge derived biochar (SBC) has often been understated. In the present study, a 30 d kinetic study proved that the removal route involved the sorption of Cr(VI), reduction to Cr(III) and immobilization of Cr(III), and that the sorption process was the primary and rate determining step. As a result of the SBC alkalinity, the solution pH increased, and sorption was largely inhibited, which then governed the overall removal ratio. The FTIR spectra suggested the involvement of hydroxyls in these processes. Low molecular weight organic acids accelerated the removal process in the early phase and improved the reduction process.

Pigment analysis based on a line-scanning fluorescence hyperspectral imaging microscope combined with multivariate curve resolution.

A rapid and cost-effective system is vital for the detection of harmful algae that causes environmental problems in terms of water quality. The approach for algae detection was to capture images based on hyperspectral fluorescence imaging microscope by detecting specific fluorescence signatures. With the high degree of overlapping spectra of algae, the distribution of pigment in the region of interest was unknown according to a previous report. We propose an optimization method of multivariate curve resolution (MCR) to improve the performance of pigment analysis. The reconstruction image described location and concentration of the microalgae pigments. This result indicated the cyanobacterial pigment distribution and mapped the relative pigment content. In conclusion, with the advantage of acquiring two-dimensional images across a range of spectra, HSI conjoining spectral features with spatial information efficiently estimated specific features of harmful microalgae in MCR models.

Versatile Cascade Esterification Route to MQ Resins.

We describe a versatile cascade route for manufacturing MQ resins using alkoxysilanes (e.g., tetraethoxysilane (TEOS)) or equivalent oligomers (e.g., ethyl polysilicate (polyTEOS)), a carboxylic acid (typically acetic acid), and hexamethyldisiloxane (MM) as starting materials; a strong acid catalyst is also employed in the one-pot reaction. The siloxane resin synthesis is accompanied by esterification of the carboxylic acid to give ethyl acetate, which acts as an important solvent, making the process more controllable. Contrary to traditional sol-gel methods, no water is introduced in the experiments, but is generated in situ. The strategy offers several advantages, including reproducibility, high yields of siloxane resins with excellent batch-to-batch consistency and without gel formation, narrow dispersity, low Si-hydroxyl residues in the final products, and the ability of increasing the molecular weight by thermal treatment. The process utilizes the green chemistry concepts of lower pollutant formation and higher atom efficiency.