Search

The structure and functional properties of protein fibrils are closely related to environmental factors in fibrillation. Herein, soy protein isolate fibrils (SPIFs, 22 mg/mL) were prepared under acid-heating conditions in the presence of 100 mM metal ions (K+, Na+, Ca2+, Mg2+, and Fe3+). Except for Fe3+, fibrillation and subsequent larger fibril aggregates were promoted, ultimately leading to gel formation. Compared with K+ or Na+, the addition of Ca2+ or Mg2+ resulted in more organized SPIF structures with increased β-sheet contents and higher ThT fluorescence intensities. Furthermore, both of them resulted in longer fibrils with an average contour length of 700–800 nm, which significantly enhanced the storage modulus. However, the presence of Fe3+ accelerated protein hydrolysis and inhibited SPIF formation, resulting in samples consistently exhibited liquid behavior. These findings provide a foundation for understanding the influence of metal ions on regulating the fibrillation and gelling properties of SPIFs. [Display omitted] • Metal ions can modulate the morphology and gel properties of SPIF. • The presence of Ca2+ and Mg2+ facilitated the formation of elongated SPIF structures. • Fe3+ inhibited the formation of SPIF but accelerate the rate of hydrolysis. • The formation of fibrils enhanced the gel properties of SPI. [ABSTRACT FROM AUTHOR]

Biosensors show promising prospects in the assays of various targets due to their advantages of high sensitivity, good selectivity and rapid response. Molecular recognition is a key event of biosensors, which usually involves the interaction of antigen–antibody, aptamer–target, lectin–sugar, boronic acid–diol, metal chelation and DNA hybridization. Metal ions or complexes can specifically recognize phosphate groups in peptides or proteins, obviating the use of biorecognition elements. In this review, we summarized the design and applications of biosensors with metal ion–phosphate chelation interaction for molecular recognition. The sensing techniques include electrochemistry, fluorescence, colorimetry and so on.

[Display omitted] • Recent developments of chalcogen-based fluorescent probes for metal ion detection are reviewed. • Comparison of different chalcogens in the same detection system are discussed. • Design strategies of chalcogen-based fluorescent probes for metal ion detection are summarized. Metal ion detection is notably significant in fields such as the biological sciences, clinical medicine, environmental chemistry, and food safety. In this regard, fluorescent probes have represented an important technique for the rapid detection of metal ions in various areas. As Lewis bases, chalcogen elements with high electron-donating ability provide versatile detection targets for metal ion fluorescent probes. Such probes with chalcogens serving as recognition sites can be classified into coordination- and reaction-type devices. Notably, thiols; sulfides; thiocarbonyls; S-containing crown ethers, aromatic hydrocarbons, and peptides; and Se/Te-containing ligands can all serve as detection sites for these probes. O/N-containing ligands for coordination, fluorophores, and linkers all affect the electron-donating ability and selectivity of the coordination system. In this review, we discuss ongoing research efforts in this area and propose some design strategies for introducing chalcogen elements into metal ion fluorescent probes by integrating Lewis acid–base theory and comparative studies. [ABSTRACT FROM AUTHOR]

Medical implants have improved the quality of life of many patients. However, surgical intervention may eventually lead to implant microbial contamination. The aims of this research were to develop an easy, robust, quantitative assay to assess surface antimicrobial activities, especially the anti-nascent biofilm activity, and to identify control surfaces, allowing for international comparisons. Using new antimicrobial assays to assess the inhibition of nascent biofilm during persistent contact or after transient contact with bacteria, we show that the 5 cent Euro coin or other metal-based antibacterial coins can be used as positive controls, as more than 4 log reduction on bacterial survival was observed when using either S. aureus or P. aeruginosa as targets. The methods and controls described here could be useful to develop an easy, flexible and standardizable assay to assess relevant antimicrobial activities of new implant materials developed by industries and academics.

Caffeic acid phenylethyl ester (CAPE) is a natural polyphenol extracted from propolis, which is reported to have several pharmacological effects such as antibacterial, antitumor, antioxidant and anti-inflammatory activities. Hemoglobin (Hb) is closely related to the transport of drugs, and some drugs, including CAPE, can lead to a change in Hb concentration. Herein, the effects of temperature, metal ions and biosurfactants on the interaction between CAPE and Hb were studied using ultraviolet-visible spectroscopy (UV−Vis), fluorescence spectroscopy, circular dichroism (CD), dynamic light scattering (DLS) and molecular docking analysis. The results showed that the addition of CAPE led to changes in the microenvironment of Hb amino acid residues as well as the secondary structure of Hb. Hydrogen bonding and van der Waals force were found to be the main driving forces for the interaction between CAPE and Hb through fluorescence spectroscopy and thermodynamic parameter data. The results of fluorescence spectroscopy also showed that lowering the temperature, adding biosurfactants (sodium cholate (NaC) and sodium deoxycholate (NaDC)) and the presence of Cu2+ increased the binding force between CAPE and Hb. These results provide useful data for the targeted delivery and absorption of CAPE and other drugs.

Herein, a new type of Schiff base ligand, HSL2 (where HSL2=2,2,7,7‐tetramethyltetrahydro‐3aH‐bis[1,3]dioxolo[4,5‐b:4′,5′‐d]pyran‐5‐yl) methyl‐4‐(3,5‐dichloro‐2‐hydroxybenzylidene amino)benzoate) anchored with a monosaccharide unit have been synthesized and characterized by FT‐IR, 1H NMR, and ESI‐MS. The ligand are chelated to metal ions Zn(II) (1), Cu(II) (2), and Mn(II) (3) to from square planar/tetrahedral or octahedral complexes. The DFT studies are carried out to optimize the shapes of the compounds. Moreover, Cu(II) and Mn(II) complexes were also characterized by EPR spectroscopy. The cytotoxicity of the complexes was screened towards three different cell lines A549 (lung cancer), HeLa (cervical cancer), and HT29 (colorectal cancer). These complexes exhibited significant cytotoxicity against three aforementioned cell lines and IC50 values are found in the range of 19.77–23 μM on HeLa cells, 9.42–12.25 μM on A549 cells and 8.84–16 μM on HT29 cells. The cell death mechanism was also studied by employing DNA fragmentation, Hoechst 33342 nuclear staining, and Acridine orange/ Ethidium Bromide (AO/EB) assay. In addition, ROS generation was also evaluated with these metal complexes. [ABSTRACT FROM AUTHOR]

VVA2 (volvatoxin A chain 2) is a cardiotoxic protein purified from Volvariella volvacea. Its biological activities include hemolysis, writhing reaction, neurotoxicity, and ventricular systolic arresting activity. The cytotoxicity of VVA2 was mainly considered due to its pore-forming activity. Here we report a novel biological activity of its variants VVA2 I82E/K86K as a duplex-specific nuclease. Recombinant VVA2 variant I82E/L86K (Re-VVA2 I82E/L86K), deprived of the oligomerization property, shows increased nuclease activity compared to VVA2. Re-VVA2 I82E/L86K converts supercoiled DNA (Replicative form I, RF I) into nicked form (RF II) and linear form (RF III) in the presence of Mg2+ or Mn2+. Besides plasmid DNA, it also exhibits nuclease activity on E. coli genomic DNA rather than ssDNA or RNA. Re-VVA2 I82E/L86K preferentially cleaves dG-dC-rich dsDNA regions and shows the best performance at pH 6–9 and 55 °C. Our structure–function study has revealed amino acid E111 may take an active part in nuclease activity through interacting with metal ions. Based on the sequences of its cleavage sites, a "double-hit" mechanism was thereby proposed. Given that Re-VVA2 I82E/L86K did not exhibit the conserved nuclease structure and sequence, it is considered an atypical duplex-specific nuclease. [ABSTRACT FROM AUTHOR]

Development of economical, sensitive, selective and robust sensors for metal ion sensing is always fascinating for a chemist because traditional routs for their detection involve complicated instrumentation and critical sample preparation procedures. A large number of metal ion detectors including carbon dots (CDs) have been reported for sensitive and selective detection of metal ions. This review comprehensively explores the use of CDs as metallic cation sensors. CDs are being fabricated from variety of carbon sources by employing various synthetic channels. CDs are proved to be efficient colorimetric and fluorimetric detectors due to surface oxygen moieties which are responsible to co-ordinate with metal ions. Doping of CDs with hetero atom such as N, S, B etc. may further enhance their activity toward metal detection. Therefore, designing of CDs having selective sensing properties with low detection limits has gained significant interest. CDs have gained much attention as chemical sensors due to their dynamic features i.e. less toxicity, stability, solubility in various solvents, absorption in UV/Vis. region, fluorescence and tunable physico-chemical properties. These are coast effective, sensitive and selective colorimetric and fluorimetric metal ion sensors. Detection of metal ions by CDs involves different mechanisms such as complexation, aggregation, electron transfer, inner filter effect etc. LOD data is an evidence of their greater efficiency. [ABSTRACT FROM AUTHOR]

The spontaneous combustion of coal is one of the main disasters affecting safe production. In order to prevent and extinguish mine fires more efficiently, a new type of fire-suppression polymer gel with strong stability has been developed. The optimal formula was determined by testing the gelation time of different ratios of gel components. The measurement of water retention rate, viscosity and permeability of the gel were also carried out to verify the thermal stability and flowability. The effect of gel on the suppression of CO emission during coal oxidation was tested by the temperature-programming experiments. By the thermogravimetric experiments, the influence of gel on coal activation energy was calculated based on the ignition activation energy theory. FTIR was also introduced to analyze the effect of gel on active groups of coal during coal oxidation. Furthermore, the extinguishing mechanism of the gel was analyzed from forming characteristics. It is proven that the strong stable gel is an excellent fire extinguishing material with the advantages of controllable glue time, good water retention and the obvious effects of sealing. [ABSTRACT FROM AUTHOR]

D-Mannose has great value in the treatment of chronic diseases. D-Mannose isomerase can catalyze the bioconversion of D-fructose to D-mannose. Therefore, a novel D-mannose isomerase gene (Strh-MIase) from Stenotrophomonas rhizophila strain IS26 was expressed, purified, and characterized for the industrial production of D-mannose. The specific activities of the Strh-MIase for D-mannose and D-fructose were 437.5 ± 0.8 U/mg and 267.2 ± 0.7 U/mg. Its optimal temperature and pH were 50 °C and 7.0. The enzymatic bioconversion produced 25 g/L D-mannose from concentration D-fructose (100 g/L) in 6 h by recombinant Strh-MIase, resulting in a final yield of 25%. Sodium phosphate inhibition has little influence on D-mannose production when a high concentration of D-fructose is used as substrate. We demonstrate that the metal ions improve the efficiency of D-mannose isomerase because of the enhancement of its thermostability. Moreover, the possible catalytic residues of Strh-MIase were identified by site-directed mutagenesis. [ABSTRACT FROM AUTHOR]

Quinoline derivative, i.e. quinilone yellow with the scientific name [sodium 2‐(2,3‐dihydro‐1,3‐dioxo‐1H‐inden‐2‐yl)quinoline‐6,8‐disulphonate] (SQDS) is analysed for fluorescence resonance energy transfer (FRET). Fluorescence quenching mechanism is studied by employing steady state and transient state spectroscopic measurements. Cobalt chloride is used as quencher in the present study. Linearity was observed in Stern–Volmer plots for transient state as well as steady state. This was further attributed to a mechanism of collisional quenching. Efficiency in fluorescence quenching is observed as there is a correlation between quenching constants of both transient and steady state. A significant energy transfer is reported between metal ions and SQDS molecule, according to FRET theory. Characterization results are studied and analysed. Application in the field of non‐linear optics are predicted for SQDS. With Kurtz and Perry powder technique, SHG (second harmonic generation) efficiency was measured using Q‐switched mode locked Nd:YAG laser emitting 1064 nm the first time with this compound. [ABSTRACT FROM AUTHOR]

For the first time, a comprehensive review of the literature data on the use of apricot (Prunus armeniaca) biomass components as a sorption material for the treatment of wastewater and environmental water from various pollutants is carried out in the present study. In addition to a comprehensive analysis of contemporary studies, the current work carried out its own microstructural and energy dispersive studies. It shows that apricot kernel shell is a promising raw material for obtaining sorption materials that can be used to extract various pollutants from aqueous media. The parameters of sorption interaction are presented, at which the highest rate of removal of pollutants was achieved. It is shown that the sorption capacity of apricot biomass components can be increased by modifying it with various chemical reagents, as well as other physical and physicochemical methods. We reveal that most publications consider the use of the latter as a raw material for the production of activated carbons. It is established that the surface area and total pore space of activated carbons from apricot kernel shells depend on the modes of carbonization and activation. It is shown that activated carbons are effective adsorbents for removing various pollutants (metal ions, dyes, oil and oil products) from aqueous media. It was found that the adsorption isotherms of pollutants in most cases are best described by the Langmuir and Freundlich models, and the process kinetics is most often described by the pseudo-second-order model. The possibility of improving the sorption characteristics of apricot biomass during chemical or physicochemical treatment is also shown. [ABSTRACT FROM AUTHOR]

Various DNA structures, including specific metal ion complexes, have been designed based on the knowledge of canonical base pairing as well as general coordination chemistry. The role of metal ions in these studies is quite broad and diverse. Metal ions can be targets themselves in analytical applications, essential building blocks of certain DNA structures that one wishes to construct, or they can be responsible for signal generation, such as luminescence or redox. Using DNA conjugates with metal chelators, one can more freely design DNA complexes with diverse structures and functions by following the simple HSAB rule. In this short review, the authors summarize a part of their DNA chemistries involving specific metal ion coordination. It consists of three topics: (1) significant stabilization of DNA triple helix by silver ion; (2) metal ion-directed dynamic sequence edition through global conformational change by intramolecular complexation; and (3) reconstruction of luminescent lanthanide complexes on DNA and their analytical applications. [ABSTRACT FROM AUTHOR]

BACKGROUND Spent edible fungus substrates were identified as potential sources to produce cellulose derivatives, namely purified cellulose and dicarboxyl cellulose nanocrystal (DCNC). Purified celluloses were obtained via chemical treatments and then oxidized by sequential periodate‐chlorite without mechanical process. The structural properties of the DCNCs were characterized by transmission electron microscopy (TEM), Fourier‐transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD) and thermal gravimetric analysis (TGA). RESULTS: XRD results showed that the cellulose I structure was maintained, however, the crystallinity index decreased after oxidation process. The initial pyrolysis temperature of DCNCs ranged from 242 to 344 °C. TEM results revealed that DCNC was rod‐shaped with an average length and width of 130.88 nm and 7.3 nm, respectively. The average specific surface area (SSA) was 366.67 m2 g–1. The carboxyl content was around 3.485 mmol g–1. Finally, the adsorption capacity for contaminations was 76.98, 126.22, 64.44 and 9.63 mg g–1 for copper ion (Cu2+), lead ion (Pb2+), chromium (Cr3+) and amoxicillin (AMX), respectively. CONCLUSION: This work showed a sequentially chemical oxidation for preparing nanocellulose from secondary agricultural waste with many functional applications. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

With a decade of effort, significant progress has been achieved in the synthesis, processing, and applications of MXenes. Metal ions play many crucial roles, such as in MXene delamination, structure regulation, surface modification, MXene composite construction, and even some unique applications. The different roles of metal ions are attributed to their many interactions with MXenes and the unique nature of MXenes, including their layered structure, surface chemistry, and the existence of multi‐valent transition metals. Interactions with metal ions are crucial for the energy storage of MXene electrodes, especially in metal ion batteries and supercapacitors with neutral electrolytes. This review aims to provide a good understanding of the interactions between metal ions and MXenes, including the classification and fundamental chemistry of their interactions, in order to achieve their more effective utilization and rational design. It also provides new perspectives on MXene evolution and exfoliation, which may suggest optimized synthesis strategies. In this respect, the different effects of metal ions on MXene synthesis and processing are clarified, and the corresponding mechanisms are elaborated. Research progress on the roles metal ions have in MXene applications is also introduced. [ABSTRACT FROM AUTHOR]

To reveal mechanisms of day‐to‐day variations of the low‐latitude sporadic E (Es) layers, Es layer simulations were performed and compared to plasma layers observed by the Arecibo radar. Many studies have been conducted about the Es layers till now. However, few studies investigated the day‐to‐day variations of the Es layers especially at the low‐latitudes. Herein, for the first time, our numerical model generally succeeded in reproducing features of the day‐to‐day variations of the low‐latitude Es layers. We found that the day‐to‐day variations of the Es layers are created by a combination of day‐to‐day variations of zonal/meridional‐wind shears driven by the tides and the downward phase velocity of the tides. The wind‐driven mechanism generally explains the day‐to‐day variations of the low‐latitude Es layers. Plain Language Summary: The sporadic E (Es) layers are highly dense plasma layers appearing irregularly at altitudes 90–130 km. They cause unexpected reflections and abnormal propagations of radio waves used for broadcast communications and navigations. The Es layers exhibit day‐to‐day variations in their behaviors and structures, making it difficult to accurately predict their occurrence. In this study, our numerical ionospheric model, coupled with the neutral winds of a whole atmospheric model, reproduced day‐to‐day variations of the Es layers observed by the radar at Arecibo. This is the first time such a modeling has been performed at Arecibo after decades of research on Es layers. Our numerical model, which is based on the wind‐driven mechanism, can reproduce their daily behaviors. Day‐to‐day variations of the winds are crucial for behaviors of the low‐latitude Es layers. Key Points: Our numerical model generally reproduced day‐to‐day variations of the sporadic E (Es) layers observed at Arecibo for the first timeDay‐to‐day variations of the low‐latitude Es layers are generally created by those of the atmospheric diurnal/semi‐diurnal tidesBelow ∼100 km at the low‐latitudes, the zonal‐wind shears of the diurnal tides form the Es layers, and the vertical winds do not [ABSTRACT FROM AUTHOR]

The objectives of this study were twofold: developing lignosulfonate activated carbon fibers (LACFs) and determining the corresponding metal recovery mechanisms with batch experiments and non-linear modeling. LACFs were developed through electrospinning, followed by CO 2 -based physical activation. Physical and chemical characterizations revealed that the LACF sample that was activated for 60 min exhibited a higher specific surface area (376.54 m2/g), larger total pore volume (0.30 cm3/g), higher micropore ratio (32%), and more acidic and sulfur functional groups than did the other samples. Cu(II) and Au(III) adsorption behaviors on the LACF could be described with the Freundlich and Langmuir model, respectively. Both systems consist of physisorption and chemisorption, and the mechanisms include electrostatic forces, Van der Walls forces, cation exchange, surface complexation. In particular, Au(III) adsorption was faster, and LACF-Au bonds were stronger due to the additional microprecipitation. Furthermore, the LACF sample could regenerate after three adsorption-desorption cycles. Overall, this study provides the foundation for developing physically activated lignosulfonate carbon and its application in recovering valuable metal ions. [ABSTRACT FROM AUTHOR]

Abstract With a decade of effort, significant progress has been achieved in the synthesis, processing, and applications of MXenes. Metal ions play many crucial roles, such as in MXene delamination, structure regulation, surface modification, MXene composite construction, and even some unique applications. The different roles of metal ions are attributed to their many interactions with MXenes and the unique nature of MXenes, including their layered structure, surface chemistry, and the existence of multi‐valent transition metals. Interactions with metal ions are crucial for the energy storage of MXene electrodes, especially in metal ion batteries and supercapacitors with neutral electrolytes. This review aims to provide a good understanding of the interactions between metal ions and MXenes, including the classification and fundamental chemistry of their interactions, in order to achieve their more effective utilization and rational design. It also provides new perspectives on MXene evolution and exfoliation, which may suggest optimized synthesis strategies. In this respect, the different effects of metal ions on MXene synthesis and processing are clarified, and the corresponding mechanisms are elaborated. Research progress on the roles metal ions have in MXene applications is also introduced.

β‐CD‐NH2‐Fe3O4 magnetic nanomaterials were prepared and the electrochemical sensor was constructed using β‐CD‐NH2‐Fe3O4 magnetic nanomaterials modified GCE to determine toxic heavy metals(Pb2+, Cu2+) in river water. SEM, XRD and FTIR were used to characterize the structure and phase of β‐CD‐NH2‐Fe3O4. DPV results indicated that β‐CD‐NH2‐Fe3O4 modified GCE possessed large active area and excellent electron transfer. Under the optimum conditions, the peak current was proportional to the ion concentration in the range of 40 nM∼10 μM. LOD of Pb2+ and Cu2+ in this method was 1.71 nM and 1.57 nM, respectively. Compared with other similar results reported in the literature, the β‐CD‐NH2‐Fe3O4 modified electrode exhibited wider linear response range while with comparable lower LOD. It also exhibited excellent stability, reproducibility and anti‐interference ability. [ABSTRACT FROM AUTHOR]

Methicillin-resistant Staphylococcus aureus (MRSA) infections are a major global health problem, and novel and effective antimicrobial drugs are urgently required to combat this life-threatening pathogen. Prodigiosin (PG) is a bacterial secondary metabolite with excellent anticancer and antibacterial properties. However, little is known about the antibacterial function of PG against MRSA. Therefore, the antibacterial efficacy of PG alone and PG in combination with different metal ions against clinic isolates of MRSA and methicillin-sensitive S. aureus (MSSA) strain was evaluated in the present study. The minimum inhibitory concentration of PG against both MRSA and MSSA was 0.25 μg/mL. However, 0.1 μg/mL PG showed a stronger inhibitory effect on MSSA cell growth (47.12%) than on MRSA cell growth (35.87%). Surprisingly, we observed a significant difference (p < 0.01) in membrane integrity between PG-treated MRSA and MSSA using the propidium iodide staining assay. Further, we found that in combination with PG, Zn2+, Al3+, and Cu2+ showed synergistic antibacterial effects against MRSA and MSSA. Our results could increase the current knowledge regarding the efficacy of PG in inhibiting the growth of different types of S. aureus clinical isolates and also offer a novel strategy for developing efficient antibacterial agents. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the present work, various capping ligands [thioglycolic acid (TGA), glutathione reduced (L-GSH) and L-cysteine (L-Cyst.)] have been used to modify the surface chemistry of CdTe quantum dots (QDs). Different capped CdTe QDs are prepared by aqueous phase route and characterized by UV–visible, photo-luminescence and FTIR spectrometry. The structural properties of uncapped and capped CdTe QDs were investigated by the scanning electron microscopy and energy-dispersive X-ray spectroscopy. Optical signal of distinct capped CdTe QDs was observed to be pH, time and temperature dependent. In the presence of most of the metals ions (Xn+), capped CdTe has shown strong "Turn-Off" fluorescence responses due to 1:1 complexation between metal ions and QDs except for Cr3+ and Pb2+metal ions. In the presence of Cr3+ and Pb2+ metal ions "Turn-On" fluorescence response appeared for L-Cyst. + CdTe QDs due to fluorescence resonance energy transfer. The output of Benesi–Hildebrand relation and graphical Job's plots have established the existence of strong 1:1 complexation (Xn+: TGA + CdTe, L-GSH + CdTe, L-Cyst. + CdTe) between distinctly capped CdTe and metal ions. Further, strong appearance of relative fluorescence intensities (F − F0/F0) established the better sensing capability of L-Cyst. + CdTe and TGA + CdTe QDs for Cr3+, Pb2+ ions. The lower value of limit of detection for TGA + CdTe QDs for Pb2+ and L-Cyst. + CdTe QD for Cr3+ and Pb2+ metals have showed better results towards sensing. The performance of capped CdTe QD in the presence of real sample shows good recovery (66–109%), precision and accuracy(0.2–2%) with a sensitivity of 10–7 M. Our findings have shown a strong possibility of L-Cyst. and TGA capped CdTe QDs to be used as better metal ion sensors for Cr3+ and Pb2+. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The natural organic matter and the iron and manganese oxides are potential adsorbing agents of heavy metals in sediments and create a sink for them to control their bioavailability and mobility in the aquatic environment. The salinity and pH of the surrounding water highly affect the fixation of heavy metals on the river sediments. The adsorption of copper, lead, and zinc ions in the Brahmaputra river sediment is analyzed by batch techniques. The parameters controlling these metal ions adsorption are solution pH, contact time, adsorbent amount, and adsorbate concentration. The equilibrium adsorption capacities of the sediment particles of the various sizes (< 53, 53–73, and 74–149 μm) are measured for copper, lead, and zinc ions and extrapolated using linear Freundlich and Langmuir isotherms. The results provide strong evidence to support the hypothesis of adsorption mechanism. It is found that the extent of adsorption is increasing with decreasing particle size, and this may be attributed to the enhancement of the surface area available for adsorption to occur. The sediment is studied for metal speciation, for nine heavy metals, to explain their behavior in the five sequential extraction steps. This is an interesting study as zinc is present in the air, soil, water, and almost all food items, and industries naturally release zinc into the environment. [ABSTRACT FROM AUTHOR]

Ciprofloxacin hydrochloride (CPFH) is a very common antibiotic drug for the treatment of different types of bacterial infections. The activity of the drug depends on the complexation of the employed drug with different metals present in the body. In the current investigation, the complexation behavior of CPFH drug with numerous metal ions was explored by means of UV-Visible spectroscopic and density functional theory (DFT) techniques at various temperatures. The binding constants (Kf) of CPFH+metal ions complexes were determined from the Benesi-Hildebrand equation. The Kf values experience an alteration with the nature of metal ions employed and the change of temperature. The binding of CPFH with alkali earth metals decreases with the increase of metal size and increases with the increase of temperature, while the opposite effect of temperature was observed for transition metals. The Gibbs free energy of binding (ΔGo) for the complexation between CPFH and metal ions was negative in all cases, which reveals that the complexation phenomenon is spontaneous. The values of enthalpy and entropy connote the presence of both hydrophobic and electrostatic interactions. The complexation of CPFH was observed to be endothermic in the case of alkali earth metals while exothermic for transition metals. The intrinsic enthalpy gain (ΔIIo, *) values signify the higher stability of metal-drug complexes. The compensation temperature (TC) values were found to be comparable to the biological systems. DFT studies show the formulation of 1:1 complexes with transition metals as well as the square planar geometry of the complexes. HOMO and LUMO analyses reveal that the stability of CPFH-Ni complexes is higher than that of CPFH-Co/CPFH-Zn complexes. [ABSTRACT FROM AUTHOR]

In this research work, a new type of absorbent material was obtained using kaolin which is produced by clay of the "Tsogt-Ovoo" deposit in Umnogovi province. The kaolin was produced by removing its mechanical impurities from clay and treating it to acid and heat treatment. When producing a chitosan based new absorbent bead, pure chitosan and mixtures of chitosan and kaolin (8:1, 8:2 and 8:3) with certain ratios were subjected to chemical processing. It was determined that the absorption capacity of chromium ion (Cr(VI)) was the highest when chitosan and kaolin mass ratio was 8:2. The adsorption activity of Cr(VI) in chitosan-based adsorbent was studied depending on the pH of the solution, time, temperature, initial concentration of chromiu m ion solution and mass of adsorbent material. The degree of absorption was the highest (80.25%) when initial concentration of the chromium ion solution is 50 mg/l, temperature is 25˚C, contact time is 3h and the mass of the adsorbent material is 0.1 g. It shows that this chitosan based adsorbent bead can be used for the separation of chromium (Cr(VI)) from aqueous solutions [ABSTRACT FROM AUTHOR]

The catalytic characteristics of metal ions for glucose isomerization and dehydration were investigated with metal chloride as catalyst. The influences of metal ion category, content and temperature on reaction process were studied. The reaction kinetic model was applied to correlate experimental data to analyze catalytic characteristics quantitatively. The process of glucose to HMF was a tandem reaction, and the kinetic model based on this mechanism could simulate the reaction accurately. Ni2+, Cr3+ and Sn4+ possessed good catalytic activity for glucose conversion, among which the catalyst activity of Sn4+ was the highest, and that of Ni2+ was the lowest. The kinetic constant of side reaction of Sn4+ was about 20 times of that of Ni2+ . For Ni2+, reaction rate of glucose isomerization and side reaction increased, yet the catalytic activity for fructose dehydration to HMF was negligible with the increasing of Ni2+ content. Increasing of Cr3+ could enhance reaction rate of glucose isomerization significantly, and almost had no effect on other reactions. With the increasing of Sn4+ content, reaction rate of all steps increased, yet the intensity of side reaction would decrease. The influence of temperature on reaction constants followed the Arrhenius model. Higher temperature was beneficial to the side reaction, fructose dehydration and glucose isomerization respectively, when Ni2+, Cr3+ and Sn4+ were used, respectively. [ABSTRACT FROM AUTHOR]

In the present study, we characterized the involvement of Lon protease in bacterial virulence and intracellular survival in Salmonella under abiotic stress conditions resembling the conditions of a natural infection. Wild type (JOL401) and the lon mutant (JOL909) Salmonella Typhimurium were exposed to low temperature, pH, osmotic, and oxidative stress conditions and changes in gene expression profiles related to virulence and metal ion uptake were investigated. Expression of candidate genes invF and hilC of Salmonella Pathogenicity Island (SPI)-1 and sifA and sseJ of SPI-2 revealed that Lon protease controls SPI-1 genes and not SPI-2 genes under all stress conditions tested. The lon mutant exhibited increased accumulation of hydroxyl (OH·) ions that lead to cell damage due to oxidative stress. This oxidative damage can also be linked to an unregulated influx of iron due to the upregulation of ion channel genes such as fepA in the lon mutant. The deletion of lon from the Salmonella genome causes oxidative damage and increased expression of virulence genes. It also prompts the secretion of host pro-inflammatory cytokines leading to early clearance of the bacteria from host cells. We conclude that poor bacterial recovery from mice infected with the lon mutant is a result of disrupted bacterial intracellular equilibrium and rapid activation of cytokine expression leading to bacterial lysis.

Deinococcus radiodurans can survive under extreme conditions, including high doses of DNA damaging agents and ionizing radiation, desiccation, and oxidative stress. Both the efficient cellular DNA repair machinery and antioxidation systems contribute to the extreme resistance of this bacterium, making it an ideal organism for studying the cellular mechanisms of environmental adaptation. The number of stress-related proteins identified in this bacterium has mushroomed in the past two decades. The newly identified proteins reveal both commonalities and diversity of structure, mechanism, and function, which impact a wide range of cellular functions. Here, we review the unique and general structural features of these proteins and discuss how these studies improve our understanding of the environmental stress adaptation mechanisms of D. radiodurans.

G•U wobble base pair frequently occurs in RNA structures. The unique chemical, thermodynamic, and structural properties of the G•U pair are widely exploited in RNA biology. In several RNA molecules, the G•U pair plays key roles in folding, ribozyme catalysis, and interactions with proteins. G•U may occur as a single pair or in tandem motifs with different geometries, electrostatics, and thermodynamics, further extending its biological functions. The metal binding affinity, which is essential for RNA folding, catalysis, and other interactions, differs with respect to the tandem motif type due to the different electrostatic potentials of the major grooves. In this work, we present the crystal structure of an RNA 8-mer duplex r[UCGUGCGA]2, providing detailed structural insights into the tandem motif I (5′UG/3′GU) complexed with Ba2+ cation. We compare the electrostatic potential of the presented motif I major groove with previously published structures of tandem motifs I, II (5′GU/3′UG), and III (5′GG/3′UU). A local patch of a strongly negative electrostatic potential in the major groove of the presented structure forms the metal binding site with the contributions of three oxygen atoms from the tandem. These results give us a better understanding of the G•U tandem motif I as a divalent metal binder, a feature essential for RNA functions.

In this paper, the fluorescence properties of ZnOQD-GO-g-C3N4 composite materials (ZCGQDs) were studied. Firstly, the addition of a silane coupling agent (APTES) in the synthesis process was explored, and it was found that the addition of 0.04 g·mL−1 APTES had the largest relative fluorescence intensity and the highest quenching efficiency. The selectivity of ZCGQDs for metal ions was also investigated, and it was found that ZCGQDs showed good selectivity for Cu2+. ZCGQDs were optimally mixed with Cu2+ for 15 min. ZCGQDs also had good anti-interference capability toward Cu2+. There was a linear relationship between the concentration of Cu2+ and the fluorescence intensity of ZCGQDs in the range of 1~100 µM. The regression equation was found to be F0/F = 0.9687 + 0.12343C. The detection limit of Cu2+ was about 1.74 μM. The quenching mechanism was also analyzed.

To overcome major limiting factors of microbial processes in anaerobic digestion (AD), metal and metal ions have been extensively studied. However, there is confusion about the effects of metals and metal ions on biomethane productivity in previous research. In this study, Zn and Zn2+ were selected as representatives of metals and metal ions, respectively, to investigate the effects on biomethane productivity. After the metals and metal ions at different concentrations were added to the batch AD experiments under the same mesophilic conditions, a Zn dose of 1 g/L and a Zn2+ dose of 4 mg/L were found to cause the highest biomethane production, respectively. The results indicate that metal (Zn) and metal ion (Zn2+) have different mechanisms to improve AD performance. There may be two possible explanations. To act as conductive materials in interspecies electron transfer (IET), relatively high doses of metals (e.g., 1 g/L of Zn, 10 g/L of Fe) are needed to bridge the electron transfer from syntrophic bacteria to methanogenic archaea in the AD process. As essential mineral nutrients, the AD system requires relatively low doses of metal ions (e.g., 4 mg/L of Zn2+, 5 mg/L of Fe2+) to supplement the component of various enzymes that catalyze anaerobic reactions and transformations. This research will provide clear insight for selecting appropriate amounts of metals or metal ions to enhance biomethane productivity for industrial AD processes.

Antrodia cinnamomea is a precious edible and medicinal fungus with activities of antitumor, antivirus, and immunoregulation. Fe2+ was found to promote the asexual sporulation of A. cinnamomea markedly, but the molecular regulatory mechanism of the effect is unclear. In the present study, comparative transcriptomics analysis using RNA sequencing (RNA-seq) and real time quantitative PCR (RT-qPCR) were conducted on A. cinnamomea mycelia cultured in the presence or absence of Fe2+ to reveal the molecular regulatory mechanisms underlying iron-ion-promoted asexual sporulation. The obtained mechanism is as follows: A. cinnamomea acquires iron ions through reductive iron assimilation (RIA) and siderophore-mediated iron assimilation (SIA). In RIA, ferrous iron ions are directly transported into cells by the high-affinity protein complex formed by a ferroxidase (FetC) and an Fe transporter permease (FtrA). In SIA, siderophores are secreted externally to chelate the iron in the extracellular environment. Then, the chelates are transported into cells through the siderophore channels (Sit1/MirB) on the cell membrane and hydrolyzed by a hydrolase (EstB) in the cell to release iron ions. The O-methyltransferase TpcA and the regulatory protein URBS1 promote the synthesis of siderophores. HapX and SreA respond to and maintain the balance of the intercellular concentration of iron ions. Furthermore, HapX and SreA promote the expression of flbD and abaA, respectively. In addition, iron ions promote the expression of relevant genes in the cell wall integrity signaling pathway, thereby accelerating the cell wall synthesis and maturation of spores. This study contributes to the rational adjustment and control of the sporulation of A. cinnamomea and thereby improves the efficiency of the preparation of inoculum for submerged fermentation.

Novel 1,8-naphthalimide-based fluorescent probes NI-1 and NI-2 were designed and screened for use as chemosensors for detection of heavy metal ions. Two moieties, methylpyridine (NI-1) and hydroxyphenyl (NI-2), were attached via piperazine at the C-4 position of the napthalimide core resulting in a notable effect on their spectroscopic properties. NI-1 and NI-2 are pH sensitive and show an increase in fluorescence intensity at around 525 nm (switch “on”) in the acidic environment, with pKa values at 4.98 and 2.91, respectively. Amongst heavy metal ions only Cu2+ and Hg2+ had a significant effect on the spectroscopic properties. The fluorescence of NI-1 is quenched in the presence of either Cu2+ or Hg2+ which is attributed to the formation of 1:1 metal-ligand complexes with binding constants of 3.6 × 105 and 3.9 × 104, respectively. The NI-1 chemosensor can be used for the quantification of Cu2+ ions in sub-micromolar quantities, with a linear range from 250 nM to 4.0 μM and a detection limit of 1.5 × 10−8 M. The linear range for the determination of Hg2+ is from 2 μM to 10 μM, with a detection limit of 8.8 × 10−8 M. Conversely, NI-2 behaves like a typical photoinduced electron transfer (PET) sensor for Hg2+ ions. Here, the formation of a complex with Hg2+ (binding constant 8.3 × 103) turns the green fluorescence of NI-2 into the “on” state. NI-2 showed remarkable selectivity towards Hg2+ ions, allowing for determination of Hg2+ concentration over a linear range of 1.3 μM to 25 μM and a limit of detection of 4.1 × 10−7 M.

A significant amount of literature is available on biocorrosion, which makes manual extraction of crucial information such as genes and proteins a laborious task. Despite the fast growth of biology related corrosion studies, there is a limited number of gene collections relating to the corrosion process (biocorrosion). Text mining offers a potential solution by automatically extracting the essential information from unstructured text. We present a text mining workflow that extracts biocorrosion associated genes/proteins in sulfate-reducing bacteria (SRB) from literature databases (e.g., PubMed and PMC). This semi-automatic workflow is built with the Named Entity Recognition (NER) method and Convolutional Neural Network (CNN) model. With PubMed and PMCID as inputs, the workflow identified 227 genes belonging to several Desulfovibrio species. To validate their functions, Gene Ontology (GO) enrichment and biological network analysis was performed using UniprotKB and STRING-DB, respectively. The GO analysis showed that metal ion binding, sulfur binding, and electron transport were among the principal molecular functions. Furthermore, the biological network analysis generated three interlinked clusters containing genes involved in metal ion binding, cellular respiration, and electron transfer, which suggests the involvement of the extracted gene set in biocorrosion. Finally, the dataset was validated through manual curation, yielding a similar set of genes as our workflow; among these, hysB and hydA, and sat and dsrB were identified as the metal ion binding and sulfur metabolism genes, respectively. The identified genes were mapped with the pangenome of 63 SRB genomes that yielded the distribution of these genes across 63 SRB based on the amino acid sequence similarity and were further categorized as core and accessory gene families. SRB’s role in biocorrosion involves the transfer of electrons from the metal surface via a hydrogen medium to the sulfate reduction pathway. Therefore, genes encoding hydrogenases and cytochromes might be participating in removing hydrogen from the metals through electron transfer. Moreover, the production of corrosive sulfide from the sulfur metabolism indirectly contributes to the localized pitting of the metals. After the corroboration of text mining results with SRB biocorrosion mechanisms, we suggest that the text mining framework could be utilized for genes/proteins extraction and significantly reduce the manual curation time.

This article discusses the toxicity of metal oxide nanoparticles and proposes a solution for mitigating their harmful effects. The study focuses on the use of functional amyloid fibrils made from beta lactoglobulin, a whey protein, to sequester metal ions and reduce toxicity. The researchers conducted experiments and computer modeling to demonstrate the binding capabilities of the fibrils and their minimal toxicity. This study provides a potential strategy for making metal oxide nanoparticles safer for biological and environmental applications. [Extracted from the article]

CRISPR-Cas12a, an RNA-guided DNA targeting endonuclease, has been widely used for genome editing and nucleic acid detection. As part of the essential processes for both of these applications, the two strands of double-stranded DNA are sequentially cleaved by a single catalytic site of Cas12a, but the mechanistic details that govern the generation of complete breaks in double-stranded DNA remain to be elucidated. Here, using single-molecule fluorescence resonance energy transfer assay, we identified two conformational intermediates that form consecutively following the initial cleavage of the nontarget strand. Specifically, these two intermediates are the result of further unwinding of the target DNA in the protospacer-adjacent motif (PAM)-distal region and the subsequent binding of the target strand to the catalytic site. Notably, the PAM-distal DNA unwound conformation was stabilized by Mg2+ ions, thereby significantly promoting the binding and cleavage of the target strand. These findings enabled us to propose a Mg2+-dependent kinetic model for the mechanism whereby Cas12a achieves cleavage of the target DNA, highlighting the presence of conformational rearrangements for the complete cleavage of the double-stranded DNA target. [ABSTRACT FROM AUTHOR]

In this study, a novel fluorescent probe (graphene quantum dots functionalized d‐penicillamine [GQDs‐DPA]) was developed for the selective identification of Cu2+, V5+, and Fe3+ among 26 types of metal ions, which considerably quench the fluorescence intensity of GQD. So, GQDs‐DPA was applied as a simple fluorescent probe for facile metal ions recognition in standard solution. The proposed DPA‐GQD supported amino acids respond to Cu2+, V5+, and Fe3+, with high sensitivity. The intensity of the fluorescence histogram of this probe significantly diminished in exposure to metal ions such as Cu(II), V(V), and Fe(III). Moreover, a microfluidic paper‐based device (μPAD) was fabricated through a facile and cost‐effective protocol. Cu2+, V5+, and Fe3+ can be selectively recognized by GQDs‐DPA using μPAD by naked eye. Also, GQDs‐DPA exhibits a linear response for the detection of ions in concentrations ranging from 0.01 to 1 ppm, with a low limit of quantification of 0.01 ppm in standards samples. The boosted color uniformity, low instrumental needs of the stamp, and disposability of μPADs enable the application of the proposed device for commercial applications in environmental science and technology. [ABSTRACT FROM AUTHOR]

A silver ion high-speed counter-current chromatography ([Ag+]-HSCCC) was developed to separate and purify five sesquiterpenoids from germacrene A fermentation broth. The solvent system was consisted of n-hexane-methanol-silver nitrate (3 mol/L) solution (10:9.5:0.5, v/v). By employing this chromatographic protocol, five sesquiterpenoids named β-elemene (1; 54.1 mg), germacrene A (2; 28.5 mg), γ-selinene (3; 4.6 mg), β-selinene (4; 3.4 mg), and α-selinene (5; 1.3 mg) were obtained successfully from 500 mg extracted crude sample with purities of 97.1%, 95.2%, 98.2%, 96.3% and 98.5%, respectively, combined with preparative HPLC. The results reveal that the addition of metal ion in biphasic solvent system significantly improved the HSCCC separation factor of sesquiterpenoids. Meanwhile, our study also provided an alternate approach to separate the compounds with less polarity, also geometrical isomers and various natural product classes. [ABSTRACT FROM AUTHOR]

Biodegradability significantly impacts the bioapplication of mesoporous silica nanoparticles (MSN). In recent years, immense efforts have been made to understand and tailor the biodegradability of MSN. In this mini review, we overview the recent reports on the biodegradation of MSN, with a focus on the correlation between biodegradation and physicochemical properties including specific surface area, morphology, pore size, particle diameter and condensation degree of silicon-oxygen network. In addition, strategies for improving the biodegradability of MSN such as metal ions and organic species doping are also introduced. [ABSTRACT FROM AUTHOR]

Adsorption using natural compounds is an attractive separation technique for recovering heavy metals from aqueous media. Although chitosan, which is a natural polysaccharide, is an environmentally benign adsorbent, it dissolves in an acidic aqueous medium. In this study, we prepared adsorbents consisting of chitosan modified with amidoxime groups for improving metal adsorptivity, and cellulose for improving gel stability using an ionic liquid, and examined their adsorption characteristics for metal ions. The prepared amidoxime-chitosan/cellulose hydrogels had a mechanical strength without cross-linking. All the investigated metals were adsorbed on the amidoxime-chitosan/cellulose hydrogels in the following adsorptivity order: Cu Ag > Ni > Zn. The adsorptivity of the metal ions increased with pH due to a proton exchange reaction. From the Langmuir adsorption isotherm, the Langmuir constant for Cu exceeded those of other metals because amidoxime has higher Cu affinity. The pseudo-second-order reaction model best described the adsorption kinetics with metal chelate formation being the rate-determining step. Because amidoxime-chitosan/cellulose hydrogels had higher physical stability and higher Cu selectivity, they were found to be a promising, environmentally benign adsorbent. [ABSTRACT FROM AUTHOR]

A novel conjugated polymer PFCZ‐IM containing 2‐(thiophen‐2‐yl)‐1H‐benzo[d]imidazole units was synthesized and characterized. The basic photophysical properties of the polymer and its fluorescence recognition behaviors toward metal ions and amino acids were investigated. In the study of the response of metal ions, PFCZ‐IM had high sensitivity to Fe3+, Ag+ and Cu2+, which significantly quenched the fluorescence of the polymer. The binding of the 2‐(thiophen‐2‐yl)‐1H‐benzo[d]imidazole moiety to Cu2+ was investigated by density functional theory calculation. Interestingly, [PFCZ‐IM‐Cu2+] also exhibited outstanding characteristics of fluorescence 'turn on' in the presence of cysteine (Cys), as the interaction between Cu2+ and Cys caused the polymer to dissociate from the complex. In particular, addition of 30 μmol L–1 of Cys can increase the Cu2+‐quenching fluorescence of PFCZ‐IM by 34.8 times with short response time, demonstrating that [PFCZ‐IM‐Cu2+] has tremendous potential in the actual detection of Cys. This polymer is expected to be utilized for dual fluorescence detection of specific metal ions and Cys. © 2021 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

The effect of various metal ions, namely Mn2+, Al3+, Pb2+, Cr3+, and Zn2+, on the precipitation of gypsum was investigated in the present study. The structure, functional groups, morphology, and size of gypsum crystals precipitated with additives using the batch method were evaluated experimentally through X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA)-Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and particle size and morphological analysis. The results indicate that Pb2+ and Zn2+ ions, in particular, exerted significant effects on gypsum precipitation. When Al3+ ions were the additive, only needle-like gypsum formed, whereas compact plate-like gypsum was observed in the presence of Pb2+ ions. The addition of Zn2+ ions resulted in gypsum particles of larger sizes with agglomerated shapes, simultaneously achieving an increased filtration rate of the suspensions from 5.88×10−7–2.44 × 10−6 m3/s. A detailed analysis of the crystal shape showed that while the elongation values decreased, the circularity values increased as compared with the gypsum precipitated in pure medium. These results show how metal ions can be used to effectively modify gypsum size, shape, and crystal morphology. [ABSTRACT FROM AUTHOR]

Copyright of China Forest Products Industry is the property of China Forest Products Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: Cigarette smoking might accelerate cognitive impairment; however, this has never been investigated using human cerebrospinal fluid (CSF). We conducted this study to investigate the association between cigarette smoking and cognitive impairment through metal ions in CSF.Methods: We obtained 5-ml CSF samples from routine lumbar puncture procedures in patients undergoing anterior cruciate ligament reconstruction before surgery in China. A total of 180 Chinese males were recruited (80 active smokers and 100 non-smokers). We measured specific cigarette-related neurotoxic metal ions in CSF, including iron, copper, zinc, lead, aluminum, and manganese. Sociodemographic data and history of smoking were obtained. The Montreal Cognitive Assessment (MoCA) was applied.Results: Active smokers had fewer years of education (11.83 ± 3.13 vs. 13.17 ± 2.60, p = 0.01), and higher age (33.70 ± 10.20 vs. 29.76 ± 9.58, p = 0.01) and body mass index (25.84 ± 3.52 vs. 24.98 ± 4.06, p =0.03) than non-smokers. Compared to non-smokers, active smokers had significantly higher CSF levels of iron, zinc, lead, and aluminum and lower MoCA scores (all p < 0.05). Average daily numbers of cigarettes smoked negatively correlated with the MoCA scores (r = −0.244, p = 0.048). In young smokers, CSF manganese levels negatively correlated with MoCA scores (r = −0.373, p = 0.009).Conclusions and Relevance: Cigarette smoking might be associated with male cognitive impairment, as shown by lower MoCA scores and higher levels of CSF iron, zinc, lead, and aluminum in active smokers. This might be early evidence of cigarette smoking accelerating male cognitive impairment.

The large-scale fermentation of Pichia pastoris for recombinant protein production would be time consuming and produce a large amount of waste yeast. Here we introduce a novel semi-continuous fermentation process for P. pastoris GS115 that can separate vitality cells from broth and recycle the cells to produce high-secretory recombinant pectate lyase. It is based on differences in cell sedimentation coefficients with the formation of salt bridges between metal ions and various cell states. Compared to batch-fed cultivation and general semi-continuous culture, the novel process has significant advantages, such as consuming fewer resources, taking less time, and producing less waste yeast. Sedimentation with the addition of Fe3+ metal ions consumed 14.8 ± 0.0% glycerol, 97.8 ± 1.3% methanol, 55.0 ± 0.9 inorganic salts, 81.5 ± 0.0% time cost, and 77.0 ± 0.1% waste yeast versus batch-fed cultivation to produce an equal amount of protein; in addition, the cost of solid–liquid separation was lower for cells in the collected fermentation broth. The process is economically and environmentally efficient for producing recombinant proteins.

Amyloid fibrillation of α-synuclein is implicated in the pathogenesis of Parkinson’s disease and heavy metal ions such as Fe3+, Zn2+, and Cu2+ are known to be involved in the process. In this work, we explored the use of FTIR spectroscopy to look into the modulation effects of Fe3+, Zn2+, and Cu2+ on the amyloid fibrillation of α-synuclein. We performed a curve-fitting analysis on the FTIR amide I bands of these α-synuclein fibril systems, namely, the pristine fibril and the fibrils prepared in the presence of Fe3+, Zn2+, and Cu2+. We found that the α-synuclein fibrils under the influences of metal ions all possessed a parallel β-sheet structure, turn structure, and disordered structure, similar to that of pristine α-synuclein fibril. We also observed metal-induced increases in the proportions of the β-sheet secondary structure within the α-synuclein fibrils, with Fe3+ being the most effective inducer. We performed second derivative analysis of the side chain carboxylic groups of α-synuclein fibrils and found that the side chain microenvironment of the α-synuclein fibrils was more influenced by Fe3+ than Zn2+, and Cu2+. In addition, our atomic force microscopic study revealed that the morphologies of α-synuclein fibrils under the influence of Fe3+ was quite different from that of the Zn2+ and Cu2+ systems. Our FTIR results suggested that the modulation effects of Fe3+, Zn2+, and Cu2+ on α-synuclein fibrillation occurred at both secondary and quaternary structural levels. At last, we proposed a mechanistic hypothesis to interpret how metal ions could affect the morphology of α-synuclein amyloid fibril based on the conformational plasticity properties of intrinsically disordered proteins.