Liquid Chromatography-mass Spectrometric Analysis Research Articles

Efficiency and mechanistic insights of photocatalytic degradation and sterilization utilizing g-C3N4/WO3-x Z-scheme heterojunction under full-spectrum light

Designing highly efficient full-spectrum responsive Z-scheme heterojunction for wastewater decontamination and disinfection is urgently essential. Herein, a novel Z-scheme g-C3N4/WO3-x heterojunction was successfully synthesized by a facile wet impregnation method for the highly efficient photocatalytic degradation and sterilization. Benefiting from the accelerated charge separation, broadened light absorption to near infrared region, and appropriate band energy, optimized g-C3N4/WO3-x heterojunction exhibited photocatalytic degradation of 86.3 % and 97.4 % tetracycline in 2 h under visible light and full-spectrum light, respectively. Meanwhile, 6.5-log of Escherichia coli strains could also be inactivated by optimized g-C3N4/WO3-x heterojunction within 45 min and 15 min under visible light and full-spectrum light, respectively. Impressively, it also exhibited desirable anti-interference ability and satisfying photocatalytic degradation capacity with various key experimental parameters. The plausible degradation pathways of TC and the main active species involved in the photocatalysis were investigated based on liquid chromatography-mass spectrometer (LC-MS) and electron paramagnetic resonance (EPR) analysis. Mineralization process of TC was further confirmed by three-dimensional fluorescence spectra (3D EMMs). Besides, Toxicity Estimation Software Tool (T.E.S.T.) and Ecological Structure-Activity Relationships (ECOSAR) program were applied to predict the noxiousness of TC and its potential intermediates. The results suggested that the excitotoxicity of intermediates generally decreased relative to the pristine TC. Finally, we propose a plausible enhancement mechanism of photocatalytic degradation and sterilization. This work sheds a new light on the design of novel full-spectrum responsive Z-scheme heterojunction for environmental remediation.

Unbalanced Expression of Structural Genes in Carotenoid Pathway Contributes to the Flower Color Formation of the Osmanthus Cultivar 'Yanzhi Hong'.

Carotenoids are important natural pigments that are responsible for the fruit and flower colors of many plants. The composition and content of carotenoid can greatly influence the color phenotype of plants. However, the regulatory mechanism underling the divergent behaviors of carotenoid accumulation, especially in flower, remains unclear. In this study, a new cultivar Osmanthus fragrans 'Yanzhi Hong' was used to study the regulation of carotenoid pigmentation in flower. Liquid chromatograph-mass spectrometer (LC-MS) analysis showed that β-carotene, phytoene, lycopene, γ-carotene, and lutein were the top five pigments enriched in the petals of 'Yanzhi Hong'. Through transcriptome analysis, we found that the expression of the structural genes in carotenoid pathway was imbalanced: most of the structural genes responsible for lycopene biosynthesis were highly expressed throughout the flower developmental stages, while those for lycopene metabolism kept at a relatively lower level. The downregulation of LYCE, especially at the late developmental stages, suppressed the conversion from lycopene to α-carotene but promoted the accumulation of β-carotene, which had great effect on the carotenoid composition of 'Yanzhi Hong'. Ethylene response factor (ERF), WRKY, basic helix-loop-helix (bHLH), v-myb avian myeloblastosis viral oncogene homolog (MYB), N-Acetylcysteine (NAC), auxin response factor (ARF), and other transcription factors (TFs) have participated in the flower color regulation of 'Yanzhi Hong', which formed co-expression networks with the structural genes and functioned in multiple links of the carotenoid pathway. The results suggested that the cyclization of lycopene is a key link in determining flower color. The modification of the related TFs will break the expression balance between the upstream and downstream genes and greatly influence the carotenoid profile in flowers, which can be further used for creating colorful plant germplasms.

Qualitative and quantitative characterization of elastin-like polypeptides combining low-PH/low-temperature bottom-up and intact protein liquid chromatography mass spectrometric analysis.

Elastin-like polypeptides (ELPs) are elastic and thermoresponsive biopolymers composed of VPGXG repeats (X can be any amino acid except proline), used in biomedical applications, for example, tissue engineering and drug delivery. As different variants of ELP are mostly produced fermentatively, there is a need for the development of analysis methods that allow for absolute protein quantification in both complex matrices and purified samples and MW determination of the final products. ELPs were intracellularly expressed in Escherichia coli quantified after cell lysis and enzymatic digestion using a proline-specific protease ProAlanase (Promega) at acidic conditions. Resulting peptides were separated by liquid chromatography, and mass spectrometry analysis was conducted by electrospray ionization high-resolution mass spectrometry using an Orbitrap mass spectrometer. The addition of a stable isotopically labeled internal standard enabled quantification in complex matrices. Prior to intact mass analysis, ELPs were purified from fermentation broth by inverse temperature cycling. Intact protein analysis was performed using reversed-phase liquid chromatography, and mass spectrometry analysis was conducted by electrospray ionization high-resolution mass spectrometry using a time-of-flight mass spectrometer. Absolute quantification of ELPs was achieved by utilizing ELP-specific properties, that is, proline-rich, soluble at low pH and low temperature. The repetitive nature of ELPs allows for sensitivity increase and use of higher dilution factors to minimize the matrix effects. Despite the lack of amino acids with charged side chains (Arg, His, Lys, Asp, and Glu) in ELP, we demonstrated successful intact protein analysis using reversed-phase LC coupled to electrospray ionization TOF MS. Moreover, truncated protein forms could be chromatographically separated and characterized as well as N-terminal modifications. Both methods combined enabled quantitative and qualitative characterization of fermentatively produced ELPs.

Mechanistic investigation of azo dye removal from carbon-deficient dyeing wastewater using horizontal-vertical constructed wetlands

Azo dye degradation can be achieved by simulating a series of anaerobic and aerobic conditions within the constructed wetland (CW) system. The current investigation evaluated the effectiveness of a baffled horizontal-vertical CW system, planted with Typha angustifolia, simulating anaerobic-aerobic conditions to treat carbon-deficient synthetic dyeing wastewater containing 100 mg/L Reactive Yellow 145 (RY145) azo dye. In the absence of an available carbon source in dyeing wastewater, an optimum quantity of sodium acetate was supplemented as the substrate for microbial degradation of RY145. Influent dyeing wastewater characteristics were 5555 ADMI colour, 461 mg/L chemical oxygen demand (COD) and 39 mg/L total nitrogen (TN). During the operation period, the CW system achieved 97% colour, 87% COD, 95% ammonium nitrogen (NH4+-N) and 71% TN removals at 4 d hydraulic retention time (HRT). Favourable environmental conditions, such as low redox conditions and substrate availability in horizontal CW, contributed to a significant reduction in colour (96%). Most TN reduction (67%) happened in horizontal CW by denitrification and plant assimilation. The metagenomic study revealed that Proteobacteria, Bacteroidetes, Chloroflexi and Firmicutes were responsible for pollutant degradation within horizontal CW. The UV–visible spectra and high-resolution liquid chromatograph mass spectrometer (HR-LCMS) analysis confirmed that dye degradation intermediates generated from the breakage of azo bonds were eliminated in vertical CW with high redox conditions. The results of the phytotoxicity and fish toxicity experiments demonstrated a substantial toxicity reduction in the CW system-treated effluent.

Boosted antibiotic elimination over 2D/2D mesoporous CeO2/BiOCl S-scheme photocatalyst

Exploring efficient photocatalysts holds significant importance for the prevention and treatment of antibiotic pollution. This research reports a 2D/2D CeO2/BiOCl S-scheme photocatalyst constructed by mesoporous CeO2 and BiOCl nanosheets (NSs). Efficient charge separation and transfer was achieved by the synergistic effect of large-area contact and S-scheme charge transfer mechanism, which significantly enhanced the photocatalytic performance of CeO2/BiOCl. Experimental results demonstrated that the CeO2/BiOCl photocatalyst displayed superior photocatalytic activity to the individual components, which could efficiently eliminate four types of antibiotics, namely tetracycline (TC), chlortetracycline (CTC), doxycycline (DOC), and oxytetracycline (OTC) under UV light irradiation. Particularly, the sample of 0.4CeO2/BiOCl exhibited the highest catalytic efficiency, with a TC degradation rate constant of 0.01524 min−1, which was 1.85 and 22.74 times higher than that of single CeO2 and BiOCl, respectively. Moreover, liquid chromatograph-mass spectrometer (LC-MS) analysis is employed to reveal the degradation pathways of TC. This work offers an insightful idea for the fabrication of novel S-scheme photocatalysts applied in environmental purification.

Flavonoids with lipase inhibitory activity from lemon squeezing waste: isolation, multispectroscopic and in silico studies.

Obesity is recognized as a lifestyle-related disease and the main risk factor for a series of pathological conditions, including cardiovascular diseases, hypertension and type 2 diabetes. Citrus limon is an important medicinal plant, and its fruits are rich in flavonoids investigated for their potential in managing obesity. In the present work, a green extraction applied to lemon squeezing waste (LSW) was optimized to recover pancreatic lipase (PL) inhibitors. The microwave-assisted procedure yielded an extract with higher lipase inhibitory activity than those obtained by maceration and ultrasound. The main compounds present in the extract were identified by high-performance liquid chromatographic-mass spectrometric analysis, and hesperidin, eriocitrin and 4'-methyllucenin II were isolated. The three compounds were evaluated for in vitro PL inhibitory activity, and 4'-methyllucenin II resulted in the most promising inhibitor (IC50 = 12.1 μmol L-1; Ki = 62.2 μmol L-1). Multispectroscopic approaches suggested the three flavonoids act as competitive inhibitors and the binding studies indicated a greater interaction between PL and 4'-methyllucenin II. Docking analysis indicated the significant interactions of the three flavonoids with the PL catalytic site. The present work highlights flavonoid glycosides as promising PL inhibitors and proposes LSW as a safe ingredient for the preparation of food supplements for managing obesity. © 2024 Society of Chemical Industry.

Serratiomycins D1-D3, Antibacterial Cyclic Peptides from a Serratia sp. and Structure Revision of Serratiomycin.

Serratiomycin (1) is an antibacterial cyclic depsipeptide, first discovered from a Eubacterium culture in 1998. This compound was initially reported to contain l-Leu, l-Ser, l-allo-Thr, d-Phe, d-Ile, and hydroxydecanoic acid. In the present study, 1 and three new derivatives, serratiomycin D1-D3 (2-4), were isolated from a Serratia sp. strain isolated from the exoskeleton of a long-horned beetle. The planar structures of 1-4 were elucidated by using mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy. Comparison of the NMR chemical shifts and the physicochemical data of 1 to those of previously reported serratiomycin indeed identified 1 as serratiomycin. The absolute configurations of the amino units in compounds 1-4 were determined by the advanced Marfey's method, 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl isothiocyanate derivatization, and liquid chromatography-mass spectrometric (LC-MS) analysis. Additionally, methanolysis and the modified Mosher's method were used to determine the absolute configuration of (3R)-hydroxydecanoic acid in 1. Consequently, the revised structure of 1 was found to possess d-Leu, l-Ser, l-Thr, d-Phe, l-allo-Ile, and d-hydroxydecanoic acid. In comparison with the previously published structure of serratiomycin, l-Leu, l-allo-Thr, and d-Ile in serratiomycin were revised to d-Leu, l-Thr, and l-allo-Ile. The new members of the serratiomycin family, compounds 2 and 3, showed considerably higher antibacterial activities against Staphylococcus aureus and Salmonella enterica than compound 1.

Mesoporous cobalt-manganese layered double hydroxides promote the activation of calcium sulfite for degradation and detoxification of metronidazole

Metronidazole (MNZ), a commonly used antibiotic, poses risks to water bodies and human health due to its potential carcinogenic, mutagenic, and genotoxic effects. In this study, mesoporous cobalt-manganese layered double hydroxides (CoxMny-LDH) with abundant oxygen vacancies (Ov) were successfully synthesized using the co-precipitation method and used to activate calcium sulfite (CaSO3) with slight soluble in water for MNZ degradation. The characterization results revealed that Co2Mn-LDH had higher specific areas and exhibited good crystallinity. Co2Mn-LDH/CaSO3 exhibited the best catalytic performance under optimal conditions, achieving a remarkable MNZ degradation efficiency of up to 98.1 % in only 8 min. Quenching experiments and electron paramagnetic resonance (EPR) tests showed that SO4•− and 1O2 played pivotal roles in the MNZ degradation process by activated CaSO3, while the redox cycles of Co2+/Co3+ and Mn3+/Mn4+ on the catalyst surface accelerated electron transfer, promoting radical generation. Three MNZ degradation routes were put forward based on the density functional theory (DFT) and liquid chromatography-mass spectrometer (LC-MS) analysis. Meanwhile, the toxicity analysis result demonstrated that the toxicity of intermediates post-catalytic reaction was decreased. Furthermore, the Co2Mn-LDH/CaSO3 system displayed excellent stability, reusability, and anti-interference capability, and achieved a comparably high removal efficiency across various organic pollutant water bodies. This study provides valuable insights into the development and optimization of effective heterogeneous catalysts for treating antibiotic-contaminated wastewater.

Simultaneous removal of perfluorooctanoic acid and thiocyanate by modified activated carbon fiber/persulfate system

In this study, NaOH-modified activated carbon fiber (NaOH-ACF) was used as a catalyst to activate persulfate (PS) for the removal of perfluorooctanoic acid (PFOA) and thiocyanate (SCN−) from wastewater. The effects of the crucial parameters in the NaOH-ACF/PS process, including NaOH-ACF dosage, PS concentration and initial pH, were investigated and optimized using response surface methodology. The experimental results indicated showed that under the optimal reaction conditions of NaOH-ACF dosage (0.40 g/L), PS concentration (2.0 mmol/L), pH (3.0), and temperature (25 °C), the removal efficiencies for PFOA and SCN− reached 93.63 % and 95.17 %, respectively, within 60 min of reaction. When PFOA and SCN− coexisted in the reaction system, it was observed that PFOA had minimal effect on the removal of SCN−, while SCN− actually enhanced the removal of PFOA. Free radical identification experiments demonstrated that the NaOH-ACF/PS system generated free radicals (O2−, SO4−, OH) and non-free radicals (1O2), which cooperatively facilitated the degradation of PFOA and SCN−. Furthermore, Liquid Chromatograph-Mass Spectrometer (LC-MS) analysis results have been used to speculate on the possible degradation pathways and intermediates of PFOA. The material characterization results indicated that NaOH-ACF possesses abundant surface functional groups with excellent adsorption and catalytic properties. Thus, the NaOH-ACF-activated PS advanced oxidation process offered a promising approach for the simultaneous removal of Perfluorinated compounds and thiocyanates.

Uremic Toxins and Inflammation: Metabolic Pathways Affected in Non-Dialysis-Dependent Stage 5 Chronic Kidney Disease.

Chronic kidney disease (CKD) affects approximately 12% of the global population, posing a significant health threat. Inflammation plays a crucial role in the uremic phenotype of non-dialysis-dependent (NDD) stage 5 CKD, contributing to elevated cardiovascular and overall mortality in affected individuals. This study aimed to explore novel metabolic pathways in this population using semi-targeted metabolomics, which allowed us to quantify numerous metabolites with known identities before data acquisition through an in-house polar compound library. In a prospective observational design with 50 patients, blood samples collected before the initial hemodialysis session underwent liquid chromatography and high-resolution mass spectrometer analysis. Univariate (Mann-Whitney test) and multivariate (logistic regression with LASSO regularization) methods identified metabolomic variables associated with inflammation. Notably, adenosine-5'-phosphosulfate (APS), dimethylglycine, pyruvate, lactate, and 2-ketobutyric acid exhibited significant differences in the presence of inflammation. Cholic acid, homogentisic acid, and 2-phenylpropionic acid displayed opposing patterns. Multivariate analysis indicated increased inflammation risk with certain metabolites (N-Butyrylglycine, dimethylglycine, 2-Oxoisopentanoic acid, and pyruvate), while others (homogentisic acid, 2-Phenylpropionic acid, and 2-Methylglutaric acid) suggested decreased probability. These findings unveil potential inflammation-associated biomarkers related to defective mitochondrial fatty acid beta oxidation and branched-chain amino acid breakdown in NDD stage 5 CKD, shedding light on cellular energy production and offering insights for further clinical validation.

Effects of solution chemistry on dielectric barrier atmospheric non-thermal plasma for operative degradation of antiretroviral drug nevirapine

The global prevalence of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) has been an environmental menace. Tons of drug wastes from antiretroviral therapy are released into the environment annually. We, for the first time, employed the novel dielectric barrier atmospheric non-thermal plasma (DBANP) discharge, to mitigate the inadvertent pollution arising from the antiretroviral therapy. A 40-min treatment of nevirapine achieved >94 % (0.075 min−1) removal efficiency at discharge power of 63.5 W and plasma working gas of atmospheric air. Chemical probes confirmed •OH, ONOO− and eaq− as the dominant reactive species whilst further revealing the reaction acceleration role of NaNO3 and CCl4 which are known reaction terminators. The commonly coexisting inorganic anions potentiated nevirapine removal with over 98 % efficiency, achieving the highest rate constant of 0.148 min−1 in this study. Moreover, the initial solution pH (1.5–11.1) was no limiting factor either. The insensitivity of the DBANP discharge to actual water matrices was an eminent inference of its potential applicability in practical conditions. With reference to data obtained from the liquid chromatography-mass spectrometer analysis, nevirapine degradation pathway was proposed. A nucleophilic attack by ONOO− at the cyclopropyl group and •OH attack at the carbonyl carbon of the amide group, respectively, initiated nevirapine degradation process. It is anticipated that the findings herein, will provide new insights into antiretroviral drug waste management in environmental waters using the innovative and green non-thermal plasma process.

HPLC Fingerprint Analysis of Cibotii rhizoma from Different Regions and Identification of Common Peaks by LC-MS.

To establish the fingerprint of Cibotii rhizoma using high-performance liquid chromatography (HPLC) and evaluate the quality of Cibotii rhizoma from different regions using chemometrics to identify the potential quality markers, thirteen batches of Cibotii rhizoma samples were analyzed. the similarity evaluation system of TCM chromatographic fingerprint similarity evaluation was used to confirm common peaks. The SPSS 27 software was used for hierarchical cluster analysis (HCA), and SIMCA 14.1 software was used for principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). Moreover, a batch of Cibotii rhizoma was selected for LC-MS analysis and speculated on 15 common components. HPLC fingerprint were established, 15 common peaks were matched, two chromatographic peaks were identified using standard substances (protocatechuic acid and protocatechuic aldehyde), and 13 common components were inferred through liquid chromatograph-mass spectrometer (LC-MS). The 13 batches of the samples showed good similarities (>0.910). The results of HCA, PCA and OPLS-DA showed that 13 batches of samples were divided into three groups, and different markers were selected. The method is simple, rapid and reproducible, and can provide a reference for the overall quality evaluation of Cibotii rhizoma.

Comparative Proteomic Analysis of Aqueous Humor Reveals Biochemical Disparities in the Eyes of High Myopic Patients.

Myopia accounts for a significant proportion of visual lesions worldwide and has the potential to progress toward pathological myopia. This study aims to reveal the difference in protein content in aqueous humor between high myopic and nonhigh myopic patients, as well as better understand the dysregulation of proteins in myopic eyes. Aqueous humor was collected for liquid chromatograph mass spectrometer (LC/MS) analysis from 30 individual eyes that underwent phacoemulsification and intraocular lens (IOL) implantation. Results showed that a total of 190 differentially expressed proteins were identified, which revealed their involvement in cell metabolism, immune and inflammatory response, and system and anatomical structure. Further analysis focused on 15 intensively interacted hub proteins, encompassing functions related to complement cascades, lipoprotein metabolism, and fibrin biological function. Subsequent validations demonstrated elevated levels of APOE (apolipoprotein E), C3 (complement 3), and AHSG (α-2-HS-glycoprotein) in the high myopia group (31 eyes of cataracts and 45 eyes of high myopia with cataracts). AHSG had a significant positive correlation with axial length in high myopic patients, with good efficacy in distinguishing between myopic and nonmyopic groups. AHSG may be a potential indicator of the pathological severity and participator in the pathological progress of high myopia. This study depicted differential expression characteristics of aqueous humor in patients with high myopia and provided optional information for further experimental research on exploring the molecular mechanisms and potential therapeutic targets for high myopia. Data are available via ProteomeXchange with the identifier PXD047584.

Changes in vaginal secretion lipidom as a result of therapy in patients with vulvovaginal atrophy

Introduction. Vulvovaginal atrophy is a chronic progressive disease that includes physiological and anatomical changes as a result of a decrease in the level of sex hormones. VVA affects approximately 50% of middle-aged and older women and has a detrimental effect on interpersonal relationships, sexual health, and overall quality of life. Dynamic quadripolar radiofrequency (DRF) is a non-invasive procedure that may be a potential treatment for vulvar diseases.Aim. To study the metabolites of vaginal swabs in postmenopausal women treated with DRF.Materials and methods. The study included 180 women divided into 3 groups: treatment with DRF; treatment with a combination of DRF and estradiol, and estradiol treatment. In all patients, vaginal swabs were taken before the start of treatment and a month after treatment, and clinical parameters were assessed at 6 time points. Lipids were extracted from the cervico-vaginal fluid by the Folch method followed by liquid chromatography-mass spectrometric analysis. A comparative analysis of the clinical data of each of the groups and lipid profiles after treatment with a zero time point and their changes and a correlation analysis of changes in lipid levels and changes in clinical parameters before treatment and after 1 month was carried out.Results. There was a statistically significant reduction in the severity of VVA symptoms one month after treatment in all groups. The most pronounced effect of the therapy was observed in groups with the use of DRF with the preservation of the effect up to 12 months. In the first and second groups, a statistically significant difference was found in the levels of 2 lipids, in the third – in 4. In the first group, a correlation was found with lipids related with pain and lubrication, in the second – with vaginal pH, in the third – with the index of vaginal health, orgasm, satisfaction and pain.Conclusions. VVA therapy by DRF and local hormonal treatment triggers an inflammatory cascade in tissues. The use of the strategy of treatment with physical methods of influence has a mechanism of influence similar to the local application of estrogen in VVA. DRF therapy leads to the normalization of the vaginal microbiota and can compete with the use of estrogen in this therapeutic effect.

Ultra-fast degradation of ciprofloxacin by the peroxymonosulfate activation using a Co/Al-LDH decorated magnetic hydrochar: Structural design, catalytic performance and synergistic effects

CoFe2O4/BHC-LDH3 catalyst was constructed by decoration of Co/Al layered double hydroxides (Co/Al-LDH) on bamboo hydrochar (BHC) loaded with magnetic CoFe2O4 to activate peroxymonosulfate (PMS) for ciprofloxacin (CIP) degradation. Taking advantage of structural modulation and synergistic effects between the multi-components, CoFe2O4/BHC-LDH3 demonstrated high efficient PMS activation and ultra-fast CIP removal (91.50 % within 10 min), compared with BHC (6.26 %), CoFe2O4 (26.32 %), and Co/Al-LDH (40.10 %). Both free radical (SO4–) and non-radical (1O2) were crucial during the degradation process, and a substantial decrease in aquatic toxicity of the intermediates was observed. Additionally, the stability of CoFe2O4/BHC-LDH3 in actual water environment was tested using a fixed-bed reactor, illustrating the CoFe2O4/BHC-LDH3 has good stability and anti-interference ability in long-term operation. Possible degradation pathways of CIP in the CoFe2O4/BHC-LDH3 + PMS system were proposed based on liquid chromatography-mass spectrometer analysis and density functional theory calculation. This work provides new strategies for hydrochar-supported catalyst synthesis for organic pollutants decomposition.

Fe3N sites anchored reduced graphene oxide activate peroxymonosulfate via singlet oxygen dominated process: Performance and mechanisms

Advanced oxidation processes (AOPs) have attracted much attention due to their adaptability to complex water environments. In this study, new catalysts (Fe/N-rGOs) with three dimensional (3D) interpenetrating structure were fabricated from the iron phthalocyanine (FePc) anchoring on reduced graphene oxide (rGO) for tetracycline (TC) degradation by activating peroxymonosulfate (PMS). Among them, the Fe/N-rGO-4 catalysts with high Fe-Nx center density exhibited the best degradation efficiency and the highest value of pseudo-first-order degradation reaction kinetic (k = 0.185 min−1), which was approximately 18.5, 4.2, and 2.9 times higher than the rates achieved by the pristine PMS, rGO/PMS, and calcining FePc nanoclusters without rGO (Fe/N NPs/PMS) systems, respectively. Besides, Fe/N-rGO-4 exhibited satisfactory catalytic activity over a wide pH range (3.0–9.5) and remarkable stability of degradation performance after four consecutive cycles. Quenching experiments and electrochemical analysis demonstrated that 1O2 was the primary reactive species, which was facilitated by the mediated electron transfer originating from the C-N group with graphitic N at the defective edges of rGO. The π-conjugated region resulting from π-π stacking interaction between rGO and FePc is the pathway of electron transfer. Furthermore, Fe3N sites were proved as the primary catalytic active sites, which dominated the catalytic performance. Three degradation pathways of TC including twelve intermediates were proposed based on the Liquid Chromatograph Mass Spectrometer (LC-MS) analysis. Generally, this work highlighted the great potential of Fe/N-rGOs catalysts and provided a new insight into the synthesis of high-performance carbon-based catalysts for environmental remediation.

Enhanced degradation performance and mineralization of ciprofloxacin by ionizing radiation combined with g-C3N4/CDs

In this study, the degradation of ciprofloxacin (CIP) was investigated in the synergetic system of electron beam irradiation (EBI) combined with graphite carbon nitride/carbon nanodots (g-C3N4/CDs). The results suggested that the presence of g-C3N4/CDs could not only promote the degradation of CIP but also significantly enhanced the mineralization ratio. At 25 kGy, the mineralization ratio increased from 18.1% to 69.0% while g-C3N4/CDs was added. Regeneration experiments revealed that the g-C3N4/CDs composite possessed good reusability. In addition to finding that the presence of CO32−, HCO3−, NO3− and NO2− obviously restrained the radiolysis process of CIP, the adding of Cl− and SO42− could also have slight inhibitory effects. The effect of various water matrices in EBI&g-C3N4/CDs systems suggested that the degradation efficiency decreased in lake and tap water. Moreover, the studies in the presence of different radical scavengers suggested that ·OH was the main reactive species in the degradation process. The possible degradation pathway of CIP was proposed in the light of intermediate products using Liquid chromatograph-mass spectrometer (LC–MS) analysis coupled with DFT calculations.

Liquid chromatography-mass spectrometry analyses of polyprenyl phosphates in Escherichia coli cells in which genes for isoprenoid synthesis are amplified

Overproduction of isopentenyl diphosphate by the amplification of the genes for the methylerythritol 4-phosphate pathway, dxs and dxr, is known to be deleterious for the growth of Escherichia coli. We hypothesized that overproduction of one of the endogenous isoprenoids, in addition to isopentenyl diphosphate itself, might be the cause of the reported reduced growth rate and attempted to identify the causative agent. In order to analyze polyprenyl phosphates, they were methylated by the reaction with diazomethane. The resulting dimethyl esters of polyprenyl phosphates with carbon numbers from 40 to 60 were quantitated by high-performance liquid chromatography-mass spectrometric analysis detecting ion peaks of the sodium ion adducts. The E.coli was transformed by a multi-copy plasmid carrying both the dxs and dxr genes. Amplification of dxs and dxr significantly increased the levels of polyprenyl phosphates and 2-octaprenylphenol. The levels of Z,E-mixed polyprenyl phosphates with carbon numbers of 50-60 in the strain in which ispB was co-amplified with dxs and dxr were lower than those in the control strain where only dxs and dxr were amplified. The levels of (all-E)-octaprenyl phosphate and 2-octaprenylphenol in the strains in which ispU/rth or crtE was co-amplified with dxs and dxr were lower than those in the control strain. Although the increase in the level of each isoprenoid intermediate was blocked, the growth rates of these strains were not restored. Neither polyprenyl phosphates nor 2-octaprenylphenol can be determined to be the cause of the growth rate reduction seen with dxs and dxr amplification.

Enhanced catalysis for degradation of rhodamine B by amino-functionalized Fe-MOFs with high adsorption capacity

Activation of peroxydisulfate (PDS) by iron-based metal organic frameworks (Fe-MOFs) presents a promising method to degrade various environmental contaminants. Herein, a series of environmentally friendly Fe-MOFs with different topological structures were synthesized and compared as catalysts for rhodamine B (RhB) removal process. The results indicated that amino-functionalized Fe-MOFs possessed large specific surface area and high affinity for RhB, which significantly improved the high adsorption capacity of RhB and PDS. It is found that NH2-MIL-101(Fe), containing Fe3-μ3-oxo clusters, showed high adsorption ability and excellent catalytic degradation of RhB. The efficient charge transfer from -NH2 to Fe-O clusters could efficiently accelerate Fe(II)/Fe(III) cycle. That is, NH2-MIL-101(Fe) was proved to be the most effective catalyst for removing RhB with a removal rate of 93%. The first-order kinetic constant (0.016 min−1) of NH2-MIL-101(Fe) was 2 times that of MIL-101(Fe). Singlet oxygen (1O2) was the main active species. Additionally, according to liquid chromatograph mass spectrometer (LC-MS) analysis, the degradation of RhB was mainly related to chromophore cleavage. This study guides for designing high-performance catalysts by introducing electron donating groups in organic dyes wastewater treatment.

Photocatalysis Combined with Microalgae to Promote the Degradation and Detoxification of Tetracycline Hydrochloride

The continuous discharge of antibiotics into the environment poses a serious threat to the ecological environment and human health. In this study, photocatalysis and microalgae were combined to study the removal of tetracycline hydrochloride (TCH) and its photodegradation intermediates in water. The results showed that after photocatalytic treatment, the removal rate of TCH reached 80%, but the mineralization rate was only 17.7%. While Chlorella sp. alone had poor tolerance to high concentrations of TCH, the combined treatment of photocatalysis and microalgae completely removed TCH and increased the mineralization efficiency to 35.0%. Increased cell density was observed, indicating that TCH and the intermediates produced in the photocatalysis process could be utilized by algae for growth. Meanwhile, TCH degradation pathways were proposed based on Liquid Chromatograph Mass Spectrometer analysis, and the toxicity of intermediates detected was predicted using ECOSAR software, which showed that the type and quantity of highly toxic intermediates decreased significantly after subsequent algal treatment. The results demonstrate that photocatalysis and microalgae combined treatment is an efficient and eco-friendly method for the removal of antibiotics in water.