Catalytic Stability of S-1-(4-Hydroxyphenyl)-Ethanol Dehydrogenase from Aromatoleum aromaticum.

Derived from the denitrifying bacterium Aromatoleum aromaticum EbN1 (Azoarcus sp.), the enzyme S-1-(4-hydroxyphenyl)-ethanol dehydrogenase (S-HPED) belongs to the short-chain dehydrogenase/reductase family. Using research techniques like UV-Vis spectroscopy, dynamic light scattering, thermal-shift assay and HPLC, we investigated the catalytic and structural stability of S-HPED over a wide temperature range and within the pH range of 5.5 to 9.0 under storage and reaction conditions. The relationship between aggregation and inactivation of the enzyme in various pH environments was also examined and interpreted. At pH 9.0, where the enzyme exhibited no aggregation, we characterized thermally induced enzyme inactivation. Through isothermal and multitemperature analysis of inactivation data, we identified and confirmed the first-order inactivation mechanism under these pH conditions and determined the kinetic parameters of the inactivation process. Additionally, we report the positive impact of glucose as an enzyme stabilizer, which slows down the dynamics of S-HPED inactivation over a wide range of pH and temperature and limits enzyme aggregation. Besides characterizing the stability of S-HPED, the enzyme's catalytic activity and high stereospecificity for 10 prochiral carbonyl compounds were positively verified, thus expanding the spectrum of substrates reduced by S-HPED. Our research contributes to advancing knowledge about the biocatalytic potential of this catalyst.

Plasma-activated liquids for mitigating biofilms on food and food contact surfaces.

Plasma-activated liquids (PALs) are emerging and promising alternatives to traditional decontamination technologies and have evolved as a new technology for applications in food, agriculture, and medicine. Contamination caused by foodborne pathogens and their biofilms has posed challenges and concerns to the food industry in terms of safety and quality. The nature of the food and the food processing environment are major factors that contribute to the growth of various microorganisms, followed by the biofilm characteristics that ensure their survival in severe environmental conditions and against traditional chemical disinfectants. PALs show an efficient impact against microorganisms and their biofilms, with various reactive species (short- and long-lived ones), physiochemical properties, and plasma processing factors playing a crucial role in mitigating biofilms. Moreover, there is potential to improve and optimize disinfection strategies using a combination of PALs with other technologies for the inactivation of biofilms. The overarching aim of this study is to build a better understanding of the parameters that govern the liquid chemistry generated in a liquid exposed to plasma and how these translate into biological effects on biofilms. This review provides a current understanding of PALs-mediated mechanisms of action on biofilms; however, the precise inactivation mechanism is still not clear and is an important part of the research. Implementation of PALs in the food industry could help overcome the disinfection hurdles and can enhance biofilm inactivation efficacy. Future perspectives in this field to expand existing state of the art to seek breakthroughs for scale-up and implementation of PALs technology in the food industry are also discussed.

Inactivation mechanism of slightly acidic electrolyzed water on Bacillus cereus spores.

This study aimed to investigate the inactivation mechanism of Bacillus cereus spores by slightly acidic electrolyzed water (SAEW). Spore inactivation efficacy of SAEW at different available chlorine concentrations (ACC, 20, 60 and 100 mg/L), as well as spore structures change, coat damage, mutagenesis, and inner membrane (IM) properties were examined. The viability of treated spores with lysozyme addition and spore germination induced by germinant was also examined. The results showed that SAEW could reach maximal 5.81 CFU/mL log reduction with ACC of 100 mg/L for 20 min treatment. Scanning and transmission electron photomicrographs indicated that SAEW treatment rendered spore surface ruptured, IM damage and core contents loss. No mutants were generated in survivors of SAEW treated-spores. SAEW significantly weakened spore viability in high salt medium, losing its ability to retain pyridine-2,6-dicarboxylic acid (DPA) at 85 °C. SAEW-treated spores germinated with l-alanine or inosine induction were mostly stained with propidium iodide (PI) but could not recover via lysozyme addition. Furthermore, SAEW treatment inhibited spore germination in the induction of germinant (mixture of l-alanine and inosine or dodecylamine). These findings indicated that SAEW inactivated spore primarily by damaging the spore IM.

L. monocytogens exhibited less cell membrane damage, lipid peroxidation, and intracellular reactive oxygen species accumulation after plasma-activated water treatment compared to E. coli O157:H7 and S. Typhimurium.

This study investigated the bactericidal activity of plasma-activated water (PAW) generated with a remote discharge reactor against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes. PAW-40, -80, and -120, prepared by activating distilled water for 40, 80, and 120 min, respectively, showed inactivation activity against pathogenic bacteria, which increased as the activation time increased due to decrease in pH and increase in oxidation-reduction potential and reactive oxygen/nitrogen species (RONS) of PAW. In addition, Gram-positive bacteria L. monocytogenes showed superior resistance to PAW than Gram-negative bacteria E. coli O157:H7 and S. Typhimurium. Compared with E. coli O157:H7 and S. Typhimurium, L. monocytogens exhibited less cell membrane damage, lipid peroxidation, and intracellular ROS accumulation after PAW treatment, which indicated that L. monocytogenes exhibited greater resistance because the thick cell wall buffered RONS diffusion into the cell. PAW also showed a control effect on the pathogenic bacteria on cherry tomato, and the effect was maintained throughout five repeated applications; thus, proposing high reusability of PAW. The results of this study propose that PAW generated with a remote discharge reactor can be utilized for pathogen control and provides basic data for related research and practical industrial applications.

Antibacterial Activity of Caffeic Acid Combined with UV-A Light against Escherichia coli O157:H7, Salmonella enterica Serovar Typhimurium, and Listeria monocytogenes.

The aim of this study was to evaluate the antibacterial activity of caffeic acid (CA), which is a natural polyphenol, combined with UV-A light against the representative foodborne bacteria Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes. Data regarding the inactivation of these bacteria and its dependence on CA concentration, light wavelength, and light dose were obtained. E. coli O157:H7 and Salmonella Typhimurium were reduced to the detection limit when treated with 3 mM CA and UV-A for 3 J/cm2 and 4 J/cm2, respectively, and 5 J/cm2 treatment induced 3.10 log reduction in L. monocytogenes. To investigate the mechanism for inactivation of Salmonella Typhimurium and L. monocytogenes, measurement of polyphenol uptake, membrane damage assessment, enzymatic activity assay, and transmission electron microscopy (TEM) were conducted. It was revealed that CA was significantly (P < 0.05) absorbed by bacterial cells, and UV-A light allowed a higher uptake of CA for both pathogens. Additionally, CA plus UV-A treatment induced significant (P < 0.05) cell membrane damage. In the enzymatic activity assay, the activities of both pathogens were reduced by CA, and a greater reduction occurred by use of CA plus UV-A. Moreover, transmission electron microscopy (TEM) images indicated that CA plus UV-A treatment notably destroyed the intercellular structure. In addition, antibacterial activity was also observed in commercial apple juice, which showed results similar to those obtained from phosphate-buffered saline (PBS), resulting in a significant (P < 0.05) reduction for all three pathogens without any changes in color parameters (L*, a*, and b*), total phenolic compounds, and DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging activity. IMPORTANCE Photodynamic inactivation (PDI), which involves photoactivation of a photosensitizer (PS), is an emerging field of study, as it effectively reduces various kinds of microorganisms. Although there are several PSs that have been used for PDI, there is a need to find naturally occurring PSs for safer application in the food industry. Caffeic acid, a natural polyphenol found in most fruits and vegetables, has recently been studied for its potential to act as a novel photosensitizer. However, no studies have been conducted regarding its antibacterial activity depending on treatment conditions and its antibacterial mechanism. In this study, we closely examined the effectiveness of caffeic acid in combination with UV-A light for inactivating representative foodborne bacteria in liquid medium. Therefore, the results of this research are expected to be utilized as basic data for future application of caffeic acid in PDI, especially when controlling pathogens in liquid food processing.

Glycerol as a Substrate and Inactivator of Coenzyme B12 -Dependent Diol Dehydratase.

Diol dehydratase, dependent on coenzyme B12 (B12 -dDDH), displays a peculiar feature of being inactivated by its native substrate glycerol (GOL). Surprisingly, the isofunctional enzyme, B12 -independent glycerol dehydratase (B12 -iGDH), does not undergo suicide inactivation by GOL. Herein we present a series of QM/MM and MD calculations aimed at understanding the mechanisms of substrate-induced suicide inactivation in B12 -dDDH and that of resistance of B12 -iGDH to inactivation. We show that the first step in the enzymatic transformation of GOL, hydrogen abstraction, can occur from both ends of the substrate (either C1 or C3 of GOL). Whereas C1 abstraction in both enzymes leads to product formation, C3 abstraction in B12 -dDDH results in the formation of a low energy radical intermediate, which is effectively trapped within a deep well on the potential energy surface. The long lifetime of this radical intermediate likely enables its side reactions, leading to inactivation. In B12 -iGDH, by comparison, C3 abstraction is an endothermic step; consequently, the resultant radical intermediate is not of low energy, and the reverse process of reforming the reactant is possible.

Impact of the Heterogeneity in Free Chlorine, UV254, and Ozone Susceptibilities Among Coxsackievirus B5 on the Prediction of the Overall Inactivation Efficiency.

The disinfection susceptibilities of viruses vary even among variants, yet the inactivation efficiency of a certain virus genotype, species, or genus was determined based on the susceptibility of its laboratory strain. The objectives were to evaluate the variability in susceptibilities to free chlorine, UV254, and ozone among 13 variants of coxsackievirus B5 (CVB5) and develop the model allowing for predicting the overall inactivation of heterogeneous CVB5. Our results showed that the susceptibilities differed by up to 3.4-fold, 1.3-fold, and 1.8-fold in free chlorine, UV254, and ozone, respectively. CVB5 in genogroup B exhibited significantly lower susceptibility to free chlorine and ozone than genogroup A, where the laboratory strain, Faulkner, belongs. The capsid protein in genogroup B contained a lower number of sulfur-containing amino acids, readily reactive to oxidants. We reformulated the Chick-Watson model by incorporating the probability distributions of inactivation rate constants to capture the heterogeneity. This expanded Chick-Watson model indicated that up to 4.2-fold larger free chlorine CT is required to achieve 6-log inactivation of CVB5 than the prediction by the Faulkner strain. Therefore, it is recommended to incorporate the variation in disinfection susceptibilities for predicting the overall inactivation of a certain type of viruses.

Photocatalytic inactivation and destruction of harmful microalgae Karenia mikimotoi under visible-light irradiation: Insights into physiological response and toxicity assessment.

Harmful algal blooms (HABs) caused by Karenia mikimotoi have frequently happened in coastal waters worldwide, causing serious damages to marine ecosystems and economic losses. Photocatalysis has potential to in-situ inhibit algal growth using sustainable sunlight. However, the inactivation and detoxification mechanisms of microalgae in marine environment have not been systematically investigated. In this work, for the first time, visible-light-driven photocatalytic inactivation of K. mikimotoi was attempted using g-C3N4/TiO2 immobilized films as a model photocatalyst. The inactivation efficiency could reach 64% within 60 min, evaluated by real-time in vivo chlorophyll-a fluorometric method. The immobilized photocatalyst films also exhibited excellent photo-stability and recyclability. Mechanisms study indicated photo-generated h+ and 1O2 were the dominant reactive species. Algal cell rupture process was monitored by fluorescent microscope combined with SEM observation, which confirmed the damage of cell membrane followed by the leakage of the intracellular components including the entire cell nucleus. The physiological responses regarding up-regulation of antioxidant enzyme activity (i.e. CAT and SOD), intracellular ROSs level and lipid peroxidation were all observed. Moreover, the intracellular release profile and acute toxicity assessment indicated the toxic K. mikimotoi was successfully detoxified, and the released organic matter had no cytotoxicity. This work not only provides a potential new strategy for in-situ treatment of K. mikimotoi using sunlight at sea environments, but also creates avenue for understanding the inactivation and destruction mechanisms of marine microalgae treated by photocatalysis and the toxicity impacts on the marine environments.

Application of a Krypton-Chlorine Excilamp To Control Alicyclobacillus acidoterrestris Spores in Apple Juice and Identification of Its Sporicidal Mechanism.

The aim of this study was to investigate the sporicidal effect of a krypton-chlorine (KrCl) excilamp against Alicyclobacillus acidoterrestris spores and to compare its inactivation mechanism to that of a conventional UV lamp containing mercury (Hg). The inactivation effect of the KrCl excilamp was not significantly different from that of the Hg UV lamp for A. acidoterrestris spores in apple juice despite the 222-nm wavelength of the KrCl excilamp having a higher absorption coefficient in apple juice than the 254-nm wavelength of the Hg UV lamp; this is because KrCl excilamps have a fundamentally greater inactivation effect than Hg UV lamps, which is confirmed under ideal conditions (phosphate-buffered saline). The inactivation mechanism analysis revealed that the DNA damage induced by the KrCl excilamp was not significantly different (P > 0.05) from that induced by the Hg UV lamp, while the KrCl excilamp caused significantly higher (P < 0.05) lipid peroxidation incidence and permeability change in the inner membrane of A. acidoterrestris spores than did the Hg UV lamp. Meanwhile, the KrCl excilamp did not generate significant (P > 0.05) intracellular reactive oxygen species, indicating that the KrCl excilamp causes damage only through the direct absorption of UV light. In addition, after KrCl excilamp treatment with a dose of 2,011 mJ/cm2 to reduce A. acidoterrestris spores in apple juice by 5 logs, there were no significant (P > 0.05) changes in quality parameters such as color (L*, a*, and b*), total phenolic compounds, and DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging activity.IMPORTANCEAlicyclobacillus acidoterrestris spores, which have high resistance to thermal treatment and can germinate even at low pH, are very troublesome in the juice industry. UV technology, a nonthermal treatment, can be an excellent means to control heat-resistant A. acidoterrestris spores in place of thermal treatment. However, the traditionally applied UV sources are lamps that contain mercury (Hg), which is harmful to humans and the environment; thus, there is a need to apply novel UV technology without the use of Hg. In response to this issue, excilamps, an Hg-free UV source, have been actively studied. However, no studies have been conducted applying this technique to control A. acidoterrestris spores. Therefore, the results of this study, which applied a KrCl excilamp for the control of A. acidoterrestris spores and elucidated the inactivation principle, are expected to be utilized as important basic data for application to actual industry or conducting further studies.

A novel application of In2S3 for visible-light-driven photocatalytic inactivation of bacteria: Kinetics, stability, toxicity and mechanism.

Photocatalytic bacterial inactivation under visible light emerges as a new alternative to control microbial contamination by utilizing free and renewable sunlight. However, the exploration of highly effective and safe visible-light-driven (VLD) photocatalysts remains an important step toward accessing this new technology. Herein, an eco-friendly photocatalyst, namely Indium Sulfide (In2S3), was fabricated through a facile hydrothermal method for VLD photocatalytic inactivation of bacteria. The energy band gap of the as-prepared In2S3 was measured as 2.25 eV. As expected, the obtained In2S3 photocatalyst showed remarkable inactivation efficiency toward E. coli under fluorescent tubes irradiation. The photocatalytic inactivation kinetic was perfectly fitted by a mathematical model for bacteria inactivation. In addition, In2S3 exhibited high stability and could be reused. The leakage of In3+ was not significant and showed no toxic effect to the bacteria. Based on the results of scavenger study and ESR technology, the dominant reactive species causing In2S3 VLD photocatalytic bacterial inactivation were proposed as O2-, h+, H2O2 and e-, rather than OH. The SEM study suggested that the damages to the intracellular components occurred prior to the destruction of cell wall. This study provides novel application of In2S3 for VLD photocatalytic inactivation of bacteria as well as comprehensive insight into the inactivation mechanism.

An interplay of structure and intrinsic disorder in the functionality of peptidylarginine deiminases, a family of key autoimmunity-related enzymes.

Citrullination is a post-translation modification of proteins, where the proteinaceous arginine residues are converted to non-coded citrulline residues. The immune tolerance to such citrullinated protein can be lost, leading to inflammatory and autoimmune diseases. Citrullination is a chemical reaction mediated by peptidylarginine deiminase enzymes (PADs), which are a family of calcium-dependent cysteine hydrolase enzymes that includes five isotypes: PAD1, PAD2, PAD3, PAD4, and PAD6. Each PAD has specific substrates and tissue distribution, where it modifies the arginine to produce a citrullinated protein with altered structure and function. All mammalian PADs have a sequence similarity of about 70-95%, whereas in humans, they are 50-55% homologous in their structure and amino acid sequences. Being calcium-dependent hydrolases, PADs are inactive under the physiological level of calcium, but could be activated due to distortions in calcium homeostasis, or when the cellular calcium levels are increased. In this article, we analyze some of the currently available data on the structural properties of human PADs, the mechanisms of their calcium-induced activation, and show that these proteins contain functionally important regions of intrinsic disorder. Citrullination represents an important trigger of multiple physiological and pathological processes, and as a result, PADs are recognized to play a number of important roles in autoimmune diseases, cancer, and neurodegeneration. Therefore, we also review the current state of the art in the development of PAD inhibitors with good potency and selectivity.

Role of DNA repair in Bacillus subtilis spore resistance to high energy and low energy electron beam treatments.

Bacillus subtilis spore inactivation mechanisms under low energy electron beam (LEEB) and high energy electron beam (HEEB) treatment were investigated using seven mutants lacking specific DNA repair mechanisms. The results showed that most of the DNA repair-deficient mutants, including ΔrecA, ΔKu ΔligD, Δexo Δnfo, ΔuvrAB and ΔsbcDC, had reduced resistances towards electron beam (EB) treatments at all investigated energy levels (80 keV, 200 keV and 10 MeV) compared to their wild type. This result suggested DNA damage was induced during EB treatments. The mutant lacking recA showed the lowest resistance, followed by the mutant lacking Ku and ligD. These findings indicated that recA, Ku and ligD and their associated DNA repair mechanisms, namely, homologous recombination and non-homologous end joining, play important roles in spore survival under EB treatment. Furthermore, exoA, nfo, uvrAB, splB, polY1 and polY2, which are involved in nucleotide damage repair/removal, showed different levels of effects on spore resistance under EB treatment. Finally, the results suggested that HEEB and LEEB inactivate B. subtilis spores through similar mechanisms. This research will provide a better understanding of how EB technologies inactivate B. subtilis spores and will contribute to the application of these technologies as a non-thermal, gentle spore control approach.

Inactivation and structural changes of polyphenol oxidase in quince (Cydonia oblonga Miller) juice subjected to ultrasonic treatment.

BACKGROUND: Polyphenol oxidase (PPO) is considered a problem in the food industry because it starts browning reactions during fruit and vegetable processing. Ultrasonic treatment is a technology used to inactivate the enzyme; however, the mechanism behind PPO inactivation is still unclear. For this reason, the inactivation, aggregation, and structural changes in PPO from quince juice subjected to ultrasonic treatments were investigated. Different intensities and times of ultrasonic treatment were used. Changes in the activity, aggregation, conformation, and structure of PPO were investigated through different structural analyses. RESULTS: Compared to untreated juice, the PPO activity in treated juice was reduced to 35% at a high ultrasonic intensity of 400 W for 20 min. The structure of PPO determined from particle size distribution (PSD) analysis showed that ultrasound treatment caused initial dissociation and subsequent aggregation leading to structural modification. The spectra of circular dichroism (CD) analysis of ultrasonic treated PPO protein showed a significant loss of α-helix, and reorganization of secondary structure. Fluorescence analysis showed a significant increase in fluorescence intensity of PPO after ultrasound treatment with evident blue shift, revealing disruption in the tertiary structure. CONCLUSION: In summary, ultrasonic treatment triggered protein aggregation, distortion of tertiary structure, and loss of α-helix conformation of secondary structure causing inactivation of the PPO enzyme. Hence, ultrasound processing at high intensity and duration could cause the inactivation of the PPO enzyme by inducing aggregation and structural modifications. © 2019 Society of Chemical Industry.

Airborne disinfection using microwave-based technology: Energy efficient and distinct inactivation mechanism compared with waterborne disinfection.

Microwave has been extensively applied to inactivate microorganisms in liquids, food, and surfaces. However, energy efficiency is a limiting factor for the environmental application. The utilization pathway and energy efficiency of the microwave in different media have not been investigated. In this study, the inactivation performance, energy utilization, and bactericidal mechanisms for microwave-irradiated airborne and waterborne Escherichia coli were compared. A Beer-Lambert law-based model was also developed and validated to compare the inactivation performance in different phases. Microwave had greater inactivation effect on airborne bacteria than waterborne bacteria. The inactivation rate constant for airborne E. coli (0.29 s-1) was nearly 20 times higher than that of waterborne species (0.014 s-1). Most of the absorbed microwave energy (92.3%) was converted to increase water temperature instead of inactivating the waterborne bacteria, because the microwave photons were easily absorbed by water molecules. By contrast, 45.4% of the absorbed energy could disinfect the airborne bacteria. Finally, the required energies for 1-log inactivation were calculated as 2.3 J and 116.9 J per log-inactivation for airborne and waterborne E. coli, respectively. The airborne and waterborne E. coli samples showed distinct microwave inactivation mechanisms. Waterborne E. coli disinfection was primarily due to thermal effect, while the non-thermal effect was the major mechanism for airborne E. coli inactivation.

Structural Analysis of the Histamine H1 Receptor.

The crystal structure of the human histamine H1 receptor (H1R) has been determined in complex with its inverse agonist doxepin, a first-generation antihistamine. The crystal structure showed that doxepin sits deeply inside the ligand-binding pocket and predominantly interacts with residues highly conserved among other aminergic receptors. This binding mode is considered to result in the low selectivity of the first-generation antihistamines for H1R. The crystal structure also revealed the mechanism of receptor inactivation by the inverse agonist doxepin. On the other hand, the crystal structure elucidated the anion-binding site near the extracellular portion of the receptor. This site consists of residues not conserved among other aminergic receptors, which are specific for H1R. Docking simulation and biochemical experimentation demonstrated that a carboxyl group on the second-generation antihistamines interacts with the anion-binding site. These results imply that the anion-binding site is a key site for the development of highly selective antihistamine drugs.

Effect of High-pressure CO2 Processing on Bacterial Spores.

High-pressure CO2 (HPCD) is a nonthermal technology that can effectively inactivate the vegetative forms of pathogenic and spoilage bacteria, yeasts, and molds at pressures less than 30 MPa and temperatures in the range of 20°C to 40°C. However, HPCD alone at moderate temperatures (20-40°C) is often insufficient to obtain a substantial reduction in bacterial spore counts because their structures are more complex than those of vegetative cells. In this review, we first thoroughly summarized and discussed the inactivation effect of HPCD treatment on bacterial spores. We then presented and discussed the kinetics by which bacterial spores are inactivated by HPCD treatment. We also summarized hypotheses drawn by different researchers to explain the mechanisms of spore inactivation by HPCD treatment. We then summarized the current research status and future challenges of spore inactivation by HPCD treatment.

Potential application of high pressure carbon dioxide in treated wastewater and water disinfection: Recent overview and further trends.

Recently emerging disadvantages in conventional disinfection have heightened the need for finding a new solution. Developments in the use of high pressure carbon dioxide for food preservation and sterilization have led to a renewed interest in its applicability in wastewater treatment and water disinfection. Pressurized CO2 is one of the most investigated methods of antibacterial treatment and has been used extensively for decades to inhibit pathogens in dried food and liquid products. This study reviews the literature concerning the utility of CO2 as a disinfecting agent, and the pathogen inactivation mechanism of CO2 treatment is evaluated based on all available research. In this paper, it will be argued that the successful application and high effectiveness of CO2 treatment in liquid foods open a potential opportunity for its use in wastewater treatment and water disinfection. The findings from models with different operating conditions (pressure, temperature, microorganism, water content, media …) suggest that most microorganisms are successfully inhibited under CO2 treatment. It will also be shown that the bacterial deaths under CO2 treatment can be explained by many different mechanisms. Moreover, the findings in this study can help to address the recently emerging problems in water disinfection, such as disinfection by-products (resulting from chlorination or ozone treatment).

Promoter hypermethylation along with LOH, but not mutation, contributes to inactivation of DLC-1 in nasopharyngeal carcinoma.

Previous studies have shown that promoter hypermethylation plays a key role in DLC-1 inactivation in nasopharyngeal carcinoma (NPC). However, DLC-1 mutation in NPC has not been reported, and there remain some discrepancies in methods and results between different groups. Here, we examined the mRNA and protein expression of DLC-1 in chronic nasopharyngitis (CN) and NPC tissues by reverse transcription-polymerase chain reaction/qPCR and immunohistochemistry, respectively. DLC-1 mRNA was undetectable in all the seven widely used NPC cell lines and absent or significantly down-regulated in 70% of NPC tissues. DLC-1 protein level was reduced in 74.3% of NPCs when compared with CN tissues, and significantly lower in NPC samples at advanced clinical stages than that at early stages. Then, we purified the same batch of specimens by microdissection and analyzed the possible mechanisms of DLC-1 downregulation with mutation and allelic loss analysis, methylation-specific PCR and bisulfite genomic sequencing. Only one mutation was detected at codon 693 of exon 8 in 3.3% of NPCs and five single nucleotide polymorphisms (SNPs) were identified. Loss of DLC-1 was detected in 23.3% of NPC tissues. The 100% of NPC cell lines, 80% of primary NPC and 22.2% of CN tissues showed methylation in DLC-1 promoter, while DLC-1 expression was recovered in seven NPC cell lines after 5-aza-dC treatment. Patched methylation assay confirmed that promoter methylation could repress DLC-1 expression. This report demonstrates that DLC-1 is negatively associated with NPC carcinogenesis, and promoter hypermethylation along with loss of heterozygosity, but not mutation, contributes to inactivation of DLC-1 in NPC.

Recent progress and prospect of graphitic carbon nitride-based photocatalytic materials for inactivation of Microcystis aeruginosa.

The proliferation of harmful algal blooms is a global concern due to the risk they pose to the environment and human health. Algal toxins which are hazardous compounds produced by dangerous algae, can potentially kill humans. Researchers have been drawn to photocatalysis because of its clean and energy-saving properties. Graphite carbon nitride (g-C3N4) photocatalysts have been extensively studied for their ability to eliminate algae. These photocatalysts have attracted notice because of their cost-effectiveness, appropriate electronic structure, and exceptional chemical stability. This paper reviews the progress of photocatalytic inactivation of harmful algae by g-C3N4-based materials in recent years. A brief overview is given of a number of the modification techniques on g-C3N4-based photocatalytic materials, as well as the process of inactivating algal cells and destroying their toxins. Additionally, it provides a theoretical framework for future research on the eradication of algae using g-C3N4-based photocatalytic materials.

Novel Ag3PO4/ZnWO4-modified graphite felt electrode for photoelectrocatalytic removal of harmful algae: Performance and mechanism.

A novel Ag3PO4/ZnWO4-modified graphite felt electrode (AZW@GF) was prepared by drop coating method and applied to photoelectrocatalytic removal of harmful algae. Results showed that approximately 99.21% of chlorophyll a and 91.57% of Microcystin-LR (MCLR) were degraded by the AZW@GF-Pt photoelectrocatalytic system under the optimal operating conditions with a rate constant of 0.02617 min-1 and 0.01416 min-1, respectively. The calculated synergistic coefficient of photoelectrocatalytic algal removal and MC-LR degradation by the AZW@GF-Pt system was both larger than 1.9. In addition, the experiments of quenching experiments and electron spin resonance (ESR) revealed that the photoelectrocatalytic reaction mainly generated •OH and •O2- for algal removal and MC-LR degradation. Furthermore, the potential pathway for photoelectrocatalytic degradation of MC-LR was proposed. Finally, the photoelectrocatalytic cycle algae removal experiments were carried out on AZW@GF electrode, which was found to maintain the algae removal efficiency at about 91% after three cycles of use, indicating that the photoelectrocatalysis of AZW@GF electrode is an effective emergency algae removal technology.