Humic substances mediated superior photochemical pollutant conversion on defective TiO2 in environmentally relevant matrices: The key roles of oxygen vacancy in surface interactions, oxidant activation and radical generation.

Ubiquitous humic substances usually exhibit strong interfering effects on target pollutant removal in advanced water purification. This work aims to develop a photochemical conversion system on the nonstoichiometric TiO2 for pollutant removal in environmentally relevant matrices. In this synergistic reaction system, the redox-reactive humic substances and defective oxygen vacancies can serve as the organic electron transfer mediator and the key surface reactive sites, respectively. This system achieves a superior pollutant degradation in real surface water at low oxidant concentrations. Reactive oxygen vacancies on the TiO2 surface and sub-surface are of considerable interest for this photochemical reaction system. By engineering defective oxygen vacancies on high-energy {001} polar facet, the surface and electronic interactions between tailored TiO2 and humic substances are greatly strengthened for the promoted electron transfer and oxidant activation. Rendered by the strong surface affinity and molecular activation, defective oxygen vacancies thermodynamically and dynamically promote reactive chain reactions for free radical formation, including the selective O2 reduction to ·O2- and the H2O2 activation to ·OH. Our findings take new insights into environmental geochemistry, and provide an effective strategy to in-situ boost the humic substances-mediated water purification without secondary pollution. ENVIRONMENTAL IMPLICATION: Humic substances are widely distributed in aquatic environment, thus playing important roles in environmental geochemistry. For example, humic substances can achieve good surface adsorption through electrostatic adsorption, ligand exchange and electronic interactions with typical TiO2 to form reactive ligand-metal charge transfer complexes for pollutant degradation. Inspired by the unique properties of surface and sub-surface oxygen vacancies, the defective TiO2 was designed to refine the humic substances-mediated photochemical reactions. A superior reactivity was measured for pollutant degradation. Our findings provide an effective strategy to boost naturally photochemical decontamination in environmentally relevant matrices.

Self-Assembled Multienzyme Nanostructures for Biocatalysis in Cellulo.

Multienzyme complexes naturally exist in cells to catalyze cascade reactions in metabolic pathways. By clustering the enzymes in close proximity, these nanomachineries achieve effective conversion of metabolites. Bioengineers are working on the development of synthetic versions of multienzyme complexes in cells to synergize heterologous biosynthesis. Assembling enzymes on protein scaffolds through protein-protein interactions is a viable and facile way to form synthetic multienzyme complexes. Here, we describe the general methods to construct self-assembled multienzyme nanostructures in Escherichia coli for biosynthesis of valuable chemicals.

Phase-Separated Multienzyme Compartmentalization for Terpene Biosynthesis in a Prokaryote.

Liquid-liquid phase separation (LLPS) forms biomolecular condensates or coacervates in cells. Metabolic enzymes can form phase-separated subcellular compartments that enrich enzymes, cofactors, and substrates. Herein, we report the construction of synthetic multienzyme condensates that catalyze the biosynthesis of a terpene, α-farnesene, in the prokaryote E. coli. RGGRGG derived from LAF-1 was used as the scaffold protein to form the condensates by LLPS. Multienzyme condensates were then formed by assembling two enzymes Idi and IspA through an RIAD/RIDD interaction. Multienzyme condensates constructed inside E. coli cells compartmentalized the cytosolic space into regions of high and low enzyme density and led to a significant enhancement of α-farnesene production. This work demonstrates LLPS-driven compartmentalization of the cytosolic space of prokaryotic cells, condensation of a biosynthetic pathway, and enhancement of the biosynthesis of α-farnesene.

Synthetic Multienzyme Complexes Assembled on Virus-like Particles for Cascade Biosynthesis In Cellulo.

Multienzyme complexes, or metabolons, are natural assemblies or clusters of sequential enzymes in biosynthesis. Spatial proximity of the enzyme active sites results in a substrate channeling effect, streamlines the cascade reaction, and increases the overall efficiency of the metabolic pathway. Engineers have constructed synthetic multienzyme complexes to acquire better control of the metabolic flux and a higher titer of the target product. As most of these complexes are assembled through orthogonal interactions or bioconjugation reactions, the number of enzymes to be assembled is limited by the number of orthogonal interaction or reaction pairs. Here, we utilized the Tobacco mosaic virus (TMV) virus-like particle (VLP) as protein scaffold and orthogonal reactive protein pairs (SpyCatcher/SpyTag and SnoopCatcher/SnoopTag) as linker modules to assemble three terpene biosynthetic enzymes in Escherichia coli. The enzyme assembly switched on the production of amorpha-4,11-diene, whereas the product was undetectable in all the controls without assembly. This work demonstrates a facile strategy for constructing scaffolded catalytic nanomachineries to biosynthesize valuable metabolites in bacterial cells, and a unique assembly induced the switch-on mechanism in biosynthesis for the first time.

Synthetic Multienzyme Complexes, Catalytic Nanomachineries for Cascade Biosynthesis In Vivo.

Multienzyme complexes, or metabolons, are assemblies or clusters of sequential enzymes that naturally exist in metabolic pathways. These nanomachineries catalyze the conversion of metabolites more effectively than the freely floating enzymes by minimizing the diffusion of intermediates in vivo. Bioengineers have devised synthetic versions of multienzyme complexes in cells to synergize heterologous biosynthesis, to improve intracellular metabolic flux, and to achieve higher titer of valuable chemical products. Here, we utilized orthogonal protein reactions (SpyCatcher/SpyTag and SnoopCatcher/SnoopTag pairs) to covalently assemble three key enzymes in the mevalonate biosynthesis pathway and showed 5-fold increase of lycopene and 2-fold increase of astaxanthin production in Escherichia coli. The multienzyme complexes are ellipsoidal nanostructures with hollow interior space and uniform thickness and shapes. Intracellular covalent enzyme assembly has yielded catalytic nanomachineries that drastically enlarged the flux of carotenoid biosynthesis in vivo. These studies also deepened our understanding on the complexity of hierarchical enzyme assembly in vivo.

Epidemiological survey of dyslipidemia in civil aviators in china from 2006 to 2011.

Aim. This study aimed to analyze blood lipid levels, temporal trend, and age distribution of dyslipidemia in civil aviators in China. Methods. The 305 Chinese aviators were selected randomly and followed up from 2006 to 2011. Their total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) levels were evaluated annually. Mean values for each parameter by year were compared using a linear mixed-effects model. The temporal trend of borderline high, high, and low status for each index and of overall borderline high, hyperlipidemia, and dyslipidemia by year was tested using a generalized linear mixed model. Results. The aviators' TC (F = 4.33, P < 0.01), HDL-C (F = 23.25, P < 0.01), and LDL-C (F = 6.13, P < 0.01) values differed across years. The prevalence of dyslipidemia (F = 5.53, P < 0.01), borderline high (F = 6.52, P < 0.01), and hyperlipidemia (F = 3.90, P < 0.01) also differed across years. The prevalence rates for hyperlipidemia and dyslipidemia were the highest in the 41-50-year-old and 31-40-year-old groups. Conclusions. Civil aviators in China were in high dyslipidemia and borderline high level and presented with dyslipidemia younger than other Chinese populations.