The adsorption of tetracycline (TC) on a Na-montmorillonite was studied as a function of five background electrolyte cations (Li+, Na+, K+, Mg2+ and Ca2+), one transitional metal cation (Cu2+) and ...humic acid (HA) over a pH range from 3 to 9 using batch experiments combined with XRD and FTIR measurement. Results showed that pH had great effect on the TC adsorption and acidic condition is more favored. Monovalent (Li+, Na+ and K+) and divalent (Mg2+, Ca2+ and Cu2+) cations showed very different effects on the TC adsorption onto montmorillonite. In the presence of monovalent cations, the adsorption edge curves were little affected by the types of cations. They presented a great decrease at pH<6, then an increase to a local maximum at about pH 8, followed by a gradual decrease (8<pH<9), which might resulted from cation exchange at the interlayer surface sites and surface complexation at the basal or edge sites. In the presence of divalent cations, the adsorption of TC was enhanced compared to the ones in the presence of monovalent cations, indicating other mechanism might involve. The enhanced TC adsorption has an order: Cu2+≫Ca2+>Mg2+, which might be due to the capability of “bridge” effect of divalent cations. The difference of enhancing TC adsorption in the presence of Ca2+ and Mg2+ might be a result of different ionic radii and different interacting groups in TC molecular. XRD results showed that TC was intercalated into interlayers of montmorillonite since the interlayer expansion was observed. The band changes of amide carbonyl and amino groups in tricarbonyl methane group and the carbonyl group in phenolic deketone group in the FTIR spectra of TC equilibrated with montmorillonite confirmed that TC was adsorbed to the clay via cation exchange and surface complexation. It was also found that the effect of HA on the TC adsorption was pH-dependent and the presence of HA significantly reduced the mobility of TC in solution especially under acidic condition due to the complexation between cationic or zwitterionic TC species and the deprotonated sites on HA (mainly carboxylic groups) via electrostatic attraction. These results suggested that coexistence of divalent cations and HA would reduce TC's mobility in soil environment, especially at acidic condition.
► Tetracycline adsorption to montmorillonite by ion exchange and surface complexation. ► Divalent cations improved adsorption via ion bridging: Cu2+≫Ca2+>Mg2+. ► Humic acid reduced the mobility of tetracycline in solution under acidic condition. ► Cations and humic acid have great effects on tetracycline mobility in soils.
Tetracycline (TC), a common antibiotic, can behave as an efficient ligand with cations, but the effect of its interaction with heavy metal cations on the mobility of both species in soils has not ...been well evaluated. In this study, the complexation affinities of TC with Cd (II), Cu (II) and Pb (II) were examined using potentiometric titration and spectroscopic methods. The cosorption behavior of TC and metal ions onto three selected Chinese soils was evaluated using batch adsorption experiments. The presence of metal cations promoted TC adsorption through an ion bridging effect in the order Cu (II) > Pb (II) > Cd (II), which is in accordance with their complexation ability with TC. The addition of TC affects metal adsorption differently depending on the solution pH and metal type. Therefore, it is necessary to consider the complexation ability of TC and divalent metal cations when evaluating their mobility in soils.
•The complex affinity with TC has an order of Cu(II) > Pb(II) > Cd(II).•The complexation constants of TC with the three metals are obtained.•The cosorption behavior in soils greatly depends on the complexation affinity.
The interaction between tetracycline and metal cations can influence the adsorption behavior of these species in soils, depending on their complexation ability.
A polyaniline (PAN) prepared by chemical oxidation method was studied for Hg(II) removal from aqueous solutions. Batch adsorption results showed solution pH values had a major impact on mercury ...adsorption by this sorbent with optimal removal observed around pH 4-6. At both acidic and alkaline solutions beyond this optimal pH window, sorption capacity of PAN was substantially lowered, with the impact less pronounced at pH above 6. Among the water constituents tested, only chloride and humic acid had significant inhibition on mercury removal due to competitive complexation. In the range of 0.02-0.2 M, ionic strength had less impact on Hg(II) removal by PAN while further increase in background electrolyte concentration to 1.0 M substantially decreased mercury removal. An adsorption mechanism was proposed by analyzing the XPS spectra of the key elements (N(1s), Cl(2p) and Hg(4f)) on polyaniline surfaces and the change of its electrokinetic properties, both before and after Hg(II) adsorption. Specifically, at pH 5.5, it is likely that all the nitrogen-containing functional groups on the polymer matrix including imine, protonated imine and amine could be responsible for mercury adsorption, with imine having the highest affinity while the remaining two having similar strength to complex mercury.
Copper (II) significantly enhanced tetracycline adsorption via acting as a bridge ion to form goethite–Cu2+–tetracycline complex because Cu2+ could form strong and specific inner-sphere surface ...complexes. Display omitted
► Background electrolyte cations showed almost no effect on tetracycline adsorption onto goethite. ► Copper (II) and humic acid enhanced the adsorption to different extent. ► Tetracycline was adsorbed by goethite through inner-sphere complextion. ► Copper (II) and humic acid have great effects on tetracycline mobility in soils.
Adsorption of tetracycline, one of the most widely used antibiotics, onto goethite was studied as a function of pH, metal cations, and humic acid (HA) over a pH range 3–10. Five background electrolyte cations (Li+, Na+, K+, Ca2+, and Mg2+) with a concentration of 0.01M showed little effect on the tetracycline adsorption at the studied pH range. While the divalent heavy metal cation, Cu2+, could significantly enhance the adsorption and higher concentration of Cu2+, stronger adsorption was found. The results indicated that different adsorption mechanisms might be involved for the two types of cations. Background electrolyte cations hardly interfere with the interaction between tetracycline and goethite surfaces because they only form weak outer-sphere surface complexes. On the contrary, Cu2+ could enhance the adsorption via acting as a bridge ion to form goethite–Cu2+–tetracycline surface complex because Cu2+ could form strong and specific inner-sphere surface complexes. HA showed different effect on the tetracycline sorption under different pH condition. The presence of HA increased tetracycline sorption dramatically under acidic condition. Results indicated that heavy metal cations and soil organic matters have great effects on the tetracycline mobility in the soil environment and eventually affect its exposure concentration and toxicity to organisms.
Dynamically interacting proteins associate and dissociate with their binding partners at high on/off rates. Although their identification is of great significance to proteomics research, lack of an ...efficient strategy to distinguish stable and dynamic interactors has hampered the efforts toward this goal. In this work, we developed a new method, MAP (mixing after purification)-SILAC (stable isotope labeling of amino acids in cell culture), to quantitatively investigate the interactions of protein complexes by mass spectrometry. In combination with the original SILAC approach, stable and dynamic components were effectively distinguished by the differences in their relative abundance ratio changes. We applied the newly developed strategies to decipher the dynamics of the human 26 S proteasome-interacting proteins. A total of 67 putative human proteasome-interacting proteins were identified by the MAP-SILAC method among which 14 proteins would have been misidentified as background proteins due to low relative abundance ratios in standard SILAC experiments and 57 proteins have not been reported previously. In addition, 35 of the 67 proteins were classified as stable interactors of the proteasome complex, whereas 16 of them were identified as dynamic interactors. The methods reported here provide a valuable expansion of proteomics technologies for identification of important but previously unidentifiable interacting proteins.
Despite the fundamental importance of proteasomal degradation in cells, little is known about whether and how the 26S proteasome itself is regulated in coordination with various physiological ...processes. Here we show that the proteasome is dynamically phosphorylated during the cell cycle at Thr 25 of the 19S subunit Rpt3. CRISPR/Cas9-mediated genome editing, RNA interference and biochemical studies demonstrate that blocking Rpt3-Thr25 phosphorylation markedly impairs proteasome activity and impedes cell proliferation. Through a kinome-wide screen, we have identified dual-specificity tyrosine-regulated kinase 2 (DYRK2) as the primary kinase that phosphorylates Rpt3-Thr25, leading to enhanced substrate translocation and degradation. Importantly, loss of the single phosphorylation of Rpt3-Thr25 or knockout of DYRK2 significantly inhibits tumour formation by proteasome-addicted human breast cancer cells in mice. These findings define an important mechanism for proteasome regulation and demonstrate the biological significance of proteasome phosphorylation in regulating cell proliferation and tumorigenesis.
With China's socioeconomic development, especially in the educational sector, foreign advanced education experience might not be omnipotent for the innovation and entrepreneurship education (IEE) in ...Chinese colleges. In response to such a difficult context, firstly, this study was conducted to analyze the applied innovative talent cultivation status quo in Chinese colleges under innovation and entrepreneurship. Then, the authors dug into the current situation and the development of IEE-related courses in College S through Questionnaire Survey (QS) and unveiled the efficacy of entrepreneurship environment and conditions, IEE courses, teaching methods, and policy system on the college applied innovative talents cultivation. Finally, the experiment discovered that three problems are prominent when training applied innovative talents in College S: unreasonable talent training process, imperfect education system, and emphasizing theory over practice. The main reason is that the IEE courses are not systematically set up, and teachers are in severely short supply. According to the research outcomes, the corresponding countermeasures and suggestions were proposed for applied innovative talents cultivation in College S. It is concluded that the cultivation of applied innovative talents under innovation and entrepreneurship should be reformed from four aspects: educational concept, educational model, educational policy, and social support, laying a foundation for improving the quality of IEE in Chinese colleges and universities and strengthening the cultivation of applied innovative talents.
Oxidative stress has been implicated in aging and many human diseases, notably neurodegenerative disorders and various cancers. The reactive oxygen species that are generated by aerobic metabolism ...and environmental stressors can chemically modify proteins and alter their biological functions. Cells possess protein repair pathways to rescue oxidized proteins and restore their functions. If these repair processes fail, oxidized proteins may become cytotoxic. Cell homeostasis and viability are therefore dependent on the removal of oxidatively damaged proteins. Numerous studies have demonstrated that the proteasome plays a pivotal role in the selective recognition and degradation of oxidized proteins. Despite extensive research, oxidative stress-triggered regulation of proteasome complexes remains poorly defined. Better understanding of molecular mechanisms underlying proteasome function in response to oxidative stress will provide a basis for developing new strategies aimed at improving cell viability and recovery as well as attenuating oxidation-induced cytotoxicity associated with aging and disease. Here we highlight recent advances in the understanding of proteasome structure and function during oxidative stress and describe how cells cope with oxidative stress through proteasome-dependent degradation pathways.
Several follow-up studies have found that COVID-19 (coronavirus disease 2019) patients had persistent symptoms after discharge. Gut microbiota play an important role in human health and immune ...responses. Therefore, this study investigated the gut microbiota of recovered COVID-19 patients and the correlations between gut microbiota and persistent symptoms after discharge. Stool samples were collected from 15 recovered healthcare workers (HCWs) with COVID-19 at three months after discharge, in addition, stool samples were collected from 14 healthy controls (HCs) to perform 16S rRNA gene sequencing between May and July 2020. Compared with HCs, recovered HCWs had reduced bacterial diversity at three months after discharge, with a significantly higher relative abundance of opportunistic pathogens, and a significantly lower relative abundance of beneficial bacteria. In addition,
Escherichia unclassified
was positively correlated with persistent symptoms at three months after discharge, including fatigue (r = 0.567, p = 0.028), chest tightness after activity (r = 0.687, p = 0.005), and myalgia (r = 0.523, p = 0.045).
Intestinibacter bartlettii
was positively correlated with anorexia (r = 0.629, p = 0.012) and fatigue (r = 0.545, p = 0.036). However,
Faecalibacterium prausnitzii
was negatively correlated with chest tightness after activity (r = -0.591, p = 0.02), and
Intestinimonas butyriciproducens
was negatively correlated with cough (r = -0.635, p = 0.011). In conclusion, the gut microbiota of recovered HCWs with COVID-19 at three months after discharge was different from that of HCs, and altered gut microbiota was correlated with persistent symptoms after discharge, highlighting that gut microbiota may play an important role in the recovery of patients with COVID-19.
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