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A novel compensation method for Zirconium dioxide gated Ion Sensitive Field Effect Transistors (ISFETs) to improve pH-dependent drift was demonstrated. Through the sequential measurements for both the n-channel and p-channel ISFETs, 75–100% pH-dependent drift could be successfully suppressed for the first seven hours. As a result, a nearly constant drift rate versus pH value was obtained, which increases the accuracy of pH measurements. Meanwhile, the drawback of the hyperbolic-like change with time of the common drift behavior for ISFETs was improved. A state-of-the-art integrated scheme adopting this method was also illustrated.

[Display omitted] • The recombinant BT GAD possessed high catalytic efficiency of 614.94 mM−1·min−1. • Crystal structures of BT GAD in different states were determined for the first time. • NTS, CTS, and β-hairpin coordinately regulated BT GAD activity at different pH. Glutamate decarboxylase catalyzes the conversion of glutamate to γ-aminobutyric acid, which plays a vital role in the gut-brain axis. Herein, a novel glutamate decarboxylase from Bacteroides thetaiotaomicron (BT GAD) was heterologously expressed. BT GAD possessed high catalytic efficiency at 60℃ and pH 3.6. As pH response, N-terminal sequence (NTS), C-terminal sequence (CTS), and β-hairpin in BT GAD coordinately regulated its activity under different pH. NTS folded into a loop under acidic pH, and the truncation of NTS severely reduced its activity to 4.2%. While CTS occupied the active site under neutral pH and became disordered to release the inhibition effect under acidic conditions. The β-hairpin, located near the active site, swung and formed open and closed conformations, which acted as an activity switch. This study provides the molecular basis for the coordinated regulation mechanism of BT GAD and lays a theoretical foundation for understanding the metabolism of dietary glutamate and its interaction relationships with the gut-brain axis. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel fluorescence probe assisted by Fe-doped metal deep eutectic solvent was developed to monitor nitrite and pH value. • High sensitivity and selectivity to nitrite and has good stability. • The method is green and environmentally friendly. • With excellent pH sensitivity, it is considered a new promising candidate for pH sensor in water environment. Nitrite is a widely used food additive that has been shown to be carcinogenic and can cause health damage when consumed in excess. Therefore, developing a detection method is in demand. Here, we prepared a novel Fe-doped carbon dots (Fe-CDs) using metallic deep eutectic solvent (MDES) which showed high sensitivity and selectivity. Besides, it also showed excellent pH-dependent luminescence characteristics, which proved the feasibility as a pH sensor. Under the optimal conditions, the detection linear of nitrite ranged from 0.2 to 80 µM, and the detection limit was 50 nM. The recovery rate was between 98.8 % and 104.1 % in food and water samples. For pH monitoring, its fluorescence intensity was linearly correlated in the pH range from 2 to 7, accompanying a unique differential solution color change of colorless-yellow-green. Therefore, it can be used as an excellent fluorescent probe for detection of nitrite and pH in food and water environment. [ABSTRACT FROM AUTHOR]

A pH-dependent red fluorescent N, P co-doped carbon dots (N, P-CDs) was firstly developed for rapid, sensitive and visual detection of the toxic dye malachite green (MG). The synthesis of N, P-CDs was carried out by hydrothermal treatment of o-phenylenediamine and phosphoric acid, and the low cytotoxicity of N, P-CDs was verified by Cell Counting Kit-8 (CCK-8) method. The linear decrease of N, P-CDs fluorescence in the pH range of 3.8–5.6 was attributed to the reduction of protonation of nitrogen-containing groups on the surface. And the sensing mechanism for MG was constructed based on the inner filter effect (IFE). The obtained linear ranges were 0.08–1 and 1–50 µmol·L−1 with limit of detections (LODs) of 0.07 and 0.74 µmol·L−1. The proposed method has been successfully applied to the determination of MG in water and fish samples. In addition, a kind of N, P-CDs fluorescent hydrogel kit was prepared for the visual analysis of MG. This method is not only simple, rapid and accurate, but also the prepared fluorescent hydrogel has potential application prospects for on-site qualitative identification and semi-quantitative analysis of MG, which also provides a new idea for monitoring MG in water environment and fish products. [Display omitted] • Red emitting N, P co-doped carbon dots with quantum yield of 17.28% were synthesized. • The N, P co-doped carbon dots exhibited pH-dependent property and low toxicity. • The fluorescence of N, P-doped carbon dots was quenched rapidly by malachite green. • This sensing strategy showed good linearity and low detection limit. • The fluorescent hydrogel kit was used for the visual detection of malachite green. [ABSTRACT FROM AUTHOR]

2-Thenoyltrifluoroacetone (Tta) and 1,10-Phenanthroline hydrate (Phen) were used as ligands for Eu 3+ ions to prepare graphene oxide (GO)/rare-earth (RE) complex hybrid luminescent materials by a new method. The as-prepared products are characterized via fluorescence microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, UV–Vis absorption spectroscopy, X-ray diffraction, fluorescence spectroscopy, and thermogravimetric analysis. The hybrid materials exhibit good solubility, long luminescent lifetime, high fluorescence quantum yield, good thermal and photo stability. Moreover, their fluorescence properties in sodium acetate/acetic acid buffer solution over the pH range from 3.6 to 5.4 are also studied. These properties of hybrid materials provide an important basis for their application in medicine, as potential biological markers, and as drug delivery vehicles. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) studies of acid-induced conformational switching ( trans / cis isomerization) of N , N -diarylamides bearing a pyridine moiety indicated that the trans / cis conformational preference of these amides is dependent on the relative π-electron densities of the two N -aromatic parts, and can be controlled by protonation or deprotonation of pyridine. [ABSTRACT FROM AUTHOR]

The neonatal Fc receptor for IgG (FcRn) is considered critical for the regulation of endogenous IgG and serum albumin (SA) and their circulation half-life in vivo. Both IgG and SA can bind to FcRn tightly at acidic pH but not so much at neutral pH. Here we reported a few novel single chain antibody fragments (scFv) obtained based on screening of a phage library. FnAb-8 and FnAb-12 can bind to human FcRn with higher affinities than IgG at acidic pH but similar or lower affinities than IgG at pH 7.4. Fusion proteins consisted of the therapeutic peptide, GLP-1 (Glucagon-like peptide-1) connected to the N-terminus of FnAb-8 and FnAb-12, named as G8 and G12, were shown to retain the pH-dependent binding capabilities to FcRn while also bound to the GLP-1 receptor. In vivo efficacy studies in diet induced diabetes mice confirmed the GLP-1 receptor (GLP-1R) agonist activities and sustained blood sugar lowering effect. In vivo pharmacokinetics (PK) studies were performed in nonhuman primates and FnAb-8 was found to have circulation half-life several folds longer than what have been reported for scFvs. G8 may be developed into long acting GLP-1R agonists with great potentials in clinical applications. [ABSTRACT FROM AUTHOR]

Highly-efficient photocatalyst based on Bi 2 WO 6 /SnS heterostructure was prepared via a surface functionalization method using 3-mercaptopropionic (MPA) as the surface functionalizing agent. Compared to bare Bi 2 WO 6 and SnS nanoparticles, the as-formed Bi 2 WO 6 /SnS heterostructure exhibits enhanced photocatalytic activity for the degradation of Rhodamine B (Rh B). Photoluminescence and photocurrent measurements demonstrate that the enhanced photocatalytic activity during the photocatalytic process is closely related to the enhanced electron–hole separation efficiency. The photocatalytic activity of the as-formed Bi 2 WO 6 /SnS heterostructure can be perfectly remained even after being used for five times, showing excellent durability during the photocatalytic process. The influence of pH and inorganic ions are systematically investigated. And the optimum pH for the photocatalytic process is determined to be 6. The addition of chloride ion will exert negative effect on the photodegradation process of Rh B. The mechanism of photodegradation process was investigated by exploring the quenching effects of different scavengers and the results suggest that the reactive holes play the major role in the photodegradation process of Rh B. [ABSTRACT FROM AUTHOR]

Hydrophilic monomer methacrylic acid was copolymerized with hydrophobic monomer butylmethacrylate in different molar ratio, using AIBNfree radical initiator. Successful polymerization was confirmed by FTIR and1H NMR, while DSC and XRD revealed the amorphous nature of the polymers. Copolymers were highly hemocompatible. The polymers showed pH-dependent swelling and erosion which increased with increase in pH. As the amount of methacrylic acid increased, the swelling and erosion also increased. Polymers were used for the microencapsulation of a model anti-inflammatory drug, aceclofenac by an oil-in-oil solvent evaporation method. Microparticles were characterized using FTIR, XRD, DSC, and SEM analysis. The negatively charged particles were almost spherical in shape. The drug release was best explained by zero-order kinetics with anomalous release mechanism. Less than 1% of drug was released at pH 1.2 while the bulk of the drug load was released at pH 6.8 or above, confirming the colon-targeting nature. The microparticles showed significant lowering in myeloperoxidase activity in trinitrobenzene sulfonic acid-induced colitis rat model. There was a significant lowering in the severity of disease symptoms and colon-to-body weight ratio. The histopathological studies also confirmed successful treatment with microparticle formulation. [ABSTRACT FROM PUBLISHER]

We have investigated acid- and base-induced conformational alterations of N -aryl- N -troponyl amides containing an electron-donating group on the phenyl ring. NMR spectral studies indicated that the E / Z conformational preferences of these amides can be reversibly controlled by pH-dependent protonation or deprotonation of the tropolone moiety. Thus, these compounds have potential applications as acid/base-controllable molecular switches. [ABSTRACT FROM AUTHOR]

Plasmon-driven chemical reaction of 4-nitrobenzenethiol (4-NBT) dimerizing to p,p′-dimercaptoazobenzene (DMAB) has been successfully monitored under different pH solutions. The experimental results indicated that the chemical reactions were dependent on the pH values, and they proceeded more completely under acidic conditions than those under neutral and alkaline conditions. Furthermore, the rate of the chemical reactions was effectively controlled by exposure time and incident laser power. The stable pH dependence demonstrated the plasmon-driven chemical reactions of 4-NBT to DMAB are sensitive to the surrounding environment, and have wider applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrasound improves the mass transfer of the MSWI FA carbonation reaction. • Carbonation efficiency of FA by ultrasonic physical/chemical excitation increased. • Ultrasonic carbonation inhibits the release of Pb and Zn into the liquid phase. • The solidification efficiency of Pb and Zn in UC FA is above 99.9%. • The content of heavy metal carbonates in UC FA increased by ORCHESTRA modelling. The current carbonation technology of municipal solid waste incineration fly ash (FA) has disadvantages such as low carbon sequestration efficiency, harsh conditions, and complicated equipment. An ultrasonic chemical method coupled with wet-carbonization technology is proposed. The effects of the FA ultrasonic carbonation (UC) method on CO 2 capture, heavy metals (HMs) release and solidification were investigated, and geochemical model of FA was explored. The results showed that UC improved the CO 2 capture capacity, and the carbonation efficiency increased from 14.1 % to 18.8 % because the ultrasonic physical and chemical excitation improved the mass transfer efficiency and strengthened the gas–liquid-solid three-phase carbonation reaction. UC inhibited the release of Pb and Zn into the liquid phase (0.002 mg/L and 0.004 mg/L) and increased the solidification efficiency of Pb and Zn in FA (99.99 % and 100 %) because free Pb and Zn converted carbonates completely. UC FA had a single component, small particle size, high degree of homogenization, and contained slender nano-CaCO 3 crystals. The acid neutralization capacities of original FA, FA4, and FA9 were 10, 8, and 3 meq/g because the carbonation reaction neutralized the alkaline substance. The content of carbonate minerals was the highest in UC FA and the pH of carbonate-minerals controlled dissolution/precipitation was mainly between 6 and 10. The HMs were in a soluble state (pH < 6) and the amphoteric HMs were affected by soluble hydroxides, the leaching concentration increasing (pH > 10). Therefore, UC FA had the potential of economical, environmentally friendly, and resource-based applications when avoiding strong acid and alkali application scenarios. [ABSTRACT FROM AUTHOR]

• FT-IR, 1H NMR and zeta-potential analysis are potent techniques for reaction tracking. • Formation of browning color products followed a zero-order kinetic regression. • Browning indicators exhibited large positive correlations with antioxidant activities. • Antioxidant activities of MRPs were dependent on initial solution pH. • MRPs have dual function with forming protective layer and delaying fish oil oxidation. Maillard reaction products (MRPs) between chitosan and various sugars with enhanced antioxidant activity were previously produced. However, few reports address the chitosan and corn syrup solids system that has been successfully used to encapsulate nutraceutical oils. Maillard reaction is pH-responsive, the influence of solution pH on the formation kinetic and antioxidant activity of MRPs was therefore evaluated in this work. FT-IR and zeta-potential results confirmed the formation of MRPs between chitosan and corn syrup solids. Possible Amadori compounds signals were observed clearly in the 1H NMR spectrum. Brown color development depended on initial solution pH, following a zero-order kinetic regression. Antioxidant activity of reaction products was higher than the native system and increased with an increase in the initial pH of the solution. Developed MRPs with a dual function as antioxidant and encapsulant can possibly be used to protect emulsified oil from oxidation. [ABSTRACT FROM AUTHOR]

In this study, a pH-dependent thermo-responsive polymer (poly ( N -isopropyl acrylamide- co -methacrylic acid -co- ethyl methacrylate, P(NIPAAm- co -MAA- co -EMA)), which was used as a masking functional module was designed and prepared. Its LCST was pH-dependent, leading to a sensitive isothermal phase transition between the blood and the extracellular environment of solid tumours. This masking polymer had a LCST of 36.4 °C at pH 6.5, and remained hydrophilic at pH 7.4 even when the temperature was increased to 50 °C. The liver-targeted nanoparticles (NPs) were then obtained by co-grafting the masking functional module and the targeting ligands glycyrrhetinic acid (GA) onto the gold nanoparticles (Au NPs). Their surface properties and targeting ability could be switched based on the expanding or shrinking behaviour of the polymers. The shielding/deshielding effect of GA was confirmed by the bovine serum albumin adsorption and cellular uptake. The results indicated that GA could be shielded by the hydrophilic P(NIPAAm- co -MAA- co -EMA) in the normal physiological environment (pH 7.4, 37 °C) and deshielded in the tumour microenvironment of pH 6.5, 40 °C, leading to an increase in cellular uptake as high as 2.3-fold compared with that observed at pH 7.4, 37 °C. More importantly, the ultrasensitive phase transition of the polymer was reversible, which means that the targeting ability of the deshielded Au NPs could be reshielded if they come back to the blood circulation. [ABSTRACT FROM AUTHOR]

The use of naturally derived excipients to develop enteric coatings offers significant advantages over conventional synthetic polymers. Unlike synthetic polymers, they are biodegradable, relatively abundant, have no daily intake limits or restrictions on use for dietary and nutraceutical products. However, little information is available on their dissolution properties under different gastrointestinal conditions and in comparison to each other. This work investigated the gastric resistance properties of commercially available GRAS-based coating technologies. Three coating systems were evaluated: ethyl cellulose + carboxymethyl cellulose (EC-CMC), ethyl cellulose + sodium alginate (EC-Alg) and shellac + sodium alginate (Sh-Alg) combinations. The minimum coating levels were optimized to meet USP pharmacopoeial criteria for delayed release formulations (<10% release after 2 h in pH 1.2 followed by >80% release after 45 min of pH change). Theophylline 150 mg tablets were coated with 6.5%, 7%, and 2.75% coating levels of formulations EC-CMC, EC-Alg and Sh-Alg, respectively. In vitro dissolution test revealed a fast release in pH 6.8 for ethyl cellulose based coatings: t80% value of 65 and 45 min for EC-CMC and EC-Alg respectively, while a prolonged drug release from Sh-Alg coating was observed in both pH 6.8 and 7.4 phosphate buffers. However, when more biologically relevant bicarbonate buffer was used, all coatings showed slower drug release. Disintegration test, carried out in both simulated gastric and intestinal fluid, confirmed good mechanical resistance of EC-CMC and EC-Alg coating, and revealed poor durability of the thinner Sh-Alg. Under elevated gastric pH conditions (pH 2, 3 and 4), EC-CMC and EC-Alg coatings were broken after 70, 30, 55 min and after 30, 15, 15 min, respectively, while Sh-Alg coated tablets demonstrated gastric resistance at all pH values. In conclusion, none of the GRAS-grade coatings fully complied with the different biological demands of delayed release coating systems. [ABSTRACT FROM AUTHOR]

TiO 2 thin films with different wettability were fabricated on the wood surfaces by a simple low-temperature hydrothermal method with the precursor solution pH adjusted by hydrochloric acid/sodium hydroxide. The morphologies of TiO 2 films have been changed from sphere species to filmy ones by adjusting pH of precursor solution. The TiO 2 films synthesized at the precursor solution pH of 1~10 were mainly primary existed in anatase phase without other structure, and the TiO 2 -treated wood surfaces presented different wettability with the water contact angles ranged from 9.6° to 132.7°, when the precursor solution pH were controlled to the range of 1~14. Such a wood surface with the desirable wettability shows great potential, as it may be selectively used in the various environments with different humidity. [ABSTRACT FROM AUTHOR]

To obtain ultrafiltration (UF) membranes with multi-functions in permeation, macromolecule sieving and specific heavy metal removal by adsorption, tertiary amine groups containing amphiphilic block copolymers (poly(methyl methacrylate- b -dimethylamino-2-ethyl methacrylate) (P(MMA- b -DMAEMA))) were designed and synthesized. Then the block copolymers were used to fabricate the tertiary amine block copolymer containing blend membranes with poly(vinylidene fluoride) (PVDF) via a non-solvent induced phase separation (NIPS) process. Hydrogen nuclear magnetic resonance ( 1 H NMR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the bulk and the surface layer compositions of the prepared membranes. It was found that P(MMA- b -DMAEMA) stably retained in the blend membranes and greatly enriched onto the surface layers. The pH-dependent performances of the membranes were investigated in details. With the change of pH values, the surface hydrophilicity, water permeation, dextran sieving behaviors and hexavalent chromium (Cr(VI)) adsorption properties varied greatly. And the membrane performed obviously reversible pH-dependent property. From the results, a feasible method could be inferred for fabricating UF membranes with tunable filtration, macromolecule sieving and anion adsorption properties under different pH conditions. [ABSTRACT FROM AUTHOR]

Four CoII/NiII coordination polymers, namely, [ M(H3L)2(H2O)2] n ( 1, 2) and [ M(H2L)(H2O)3] n ( 3, 4), ( M = Co for 1 and 3, M = Ni for 2 and 4, H4L = terphenyl-2,2′,4,4′-tetracarboxylic acid) were synthesized through hydrothermal reactions at different pH values and structurally characterized. Single crystal X-ray crystallographic analysis reveals that compounds 1 and 2 are isostructural and exhibit a 1D [ M2(H3L)2] n loop-like infinite chain, whereas compounds 3 and 4 are also isostructural and show a 1D pendant H2L attached [ M(H2O)] n chain motif. Additionally, variable-temperature magnetic susceptibility measurement shows weak antiferromagnetic coupling among the adjacent central CoII atoms in 1 and 3. [ABSTRACT FROM AUTHOR]

Sindbis virus pathogenesis can be affected by mutations at residues 75 and 237, individually or in combination, of the E1 domain of the viral glycoprotein. To understand the changes in fusion properties driven by these mutations, we constructed three new fusogen molecules (FMs) derived from the Sindbis virus glycoprotein (G75D, S237A and G75DS237A), and investigated their fusion activity using lentiviral nanovectors. The co-expression of FMs and antibodies on the viral particles, were shown to mediate viral transduction on targeted cells. We found that the G75D mutation enhances the transduction efficiency by broadening the pH range required for fusion. Conversely, the S237A mutation impairs infectivity; however, adding the G75D site mutation to this molecule (G75DS237A) was able to partially restore infectivity. We further demonstrate that G75D can initiate virus fusion in both the early and the late endosomes, while S237A requires that the virus be functionally transported to the late endosomes for fusion to occur. This study sheds light on the mechanism by which mutations in FMs can affect viral fusion and transduction, and explores the use of our FM-bound lentiviral nanovector platform as tool to elucidate the mechanisms of viral membrane fusion. [ABSTRACT FROM AUTHOR]

Abstract: Poly(β,L-malic acid) (PMLA) was made to interact with the cationic anticancer drug Doxorubicin (DOX) in aqueous solution to form ionic complexes with different compositions and an efficiency near to 100%. The PMLA/DOX complexes were characterized by spectroscopy, thermal analysis, and scanning electron microscopy. According to their composition, the PMLA/DOX complexes spontaneously self-assembled into spherical micro or nanoparticles with negative surface charge. Hydrolytic degradation of PMLA/DOX complexes took place by cleavage of the main chain ester bond and simultaneous release of the drug. In vitro drug release studies revealed that DOX delivery from the complexes was favored by acidic pH and high ionic strength. [Copyright &y& Elsevier]

The real-time distribution of anticancer 1403C in fermentation broth of marine fungus Halorosellinia sp. was investigated. It was closely related with pH variations, which was, 1403C in the supernatant decreased while that in the mycelia increased with pH rising. There was only 0.5 % of the total 1403C left in the supernatant when pH reached 7.0. The scanning electron microscope then provided information that compounds precipitated on the mycelia when pH rose. Then, the pH-regulation experiments proved that 1403C mainly secreted extracellular and easily dissolved in acidic condition but precipitated and absorbed on the mycelia with the increase of broth pH. Thereby, a pH-regulation strategy was proposed and applied to accumulate 1403C on the mycelia before draw-off of fermentation broth. It significantly simplified purification process and is critical for 1403C preparation of industrial scale. [ABSTRACT FROM AUTHOR]

Several near-infrared (NIR) fluorescent dyes based on aminocyanine have been designed, synthesized, and used for preparation of NIR fluorescent microspheres. Their spectral properties and pH-dependent optical characteristics were investigated. It was found that different substitution at the central position of the dyes led to diverse optical properties, with especially large effects on their spectroscopic properties. Spectroscopic responses of the fluorescent dyes to changes of pH were different. Under acidic conditions, the wavelengths of maximum absorption of the N-substituted cyanine dyes were clearly red shifted. Dyes with an N-substituted piperazidine ring were the most sensitive. The fluorescent microspheres retained the properties of the parent dyes, making them suitable for applications in biological studies. [ABSTRACT FROM AUTHOR]

Abstract: Minimizing the background signal is crucial for developing tumor-imaging techniques with sufficient specificity and sensitivity. Here we use pH difference between healthy tissues and tumor and tumor targeting delivery to achieve this goal. We synthesize fluorophore-dopamine conjugate as pH-dependent electron donor-acceptor fluorescence system. Fluorophores are highly sensitive to electron-transfer processes, which can alter their optical properties. The intrinsic redox properties of dopamine are oxidation of hydroquinone to quinone at basic pH and reduction of quinone to hydroquinone at acidic pH. Quinone can accept electron then quench fluorescence. We design tumor cell membrane-targeting carrier for delivery. We demonstrate quenched fluorophore-quinone can be specially transferred to tumor extracellular environment and tumor-accumulated fluorophore can be activated by acidic pH. These tumor-targeting pH-dependent electron donor-acceptor fluorescence systems may offer new opportunity for developing tumor-imaging techniques. [Copyright &y& Elsevier]

The clinical use of anti-EGFR antibody-based cancer therapy has been limited by antibody-EGFR binding in normal tissues, so developing pH-dependent anti-EGFR antibodies that selectively bind with EGFR in tumors-by taking advantage of the acidity of tumor microenvironment relative to normal tissues-may overcome these limitations. Here, we generated pH-dependent anti-EGFR antibodies with cross-species reactivity for human and mouse EGFR, and we demonstrate that pH-dependent antibodies exhibit tumor-selective binding by binding strongly to EGFR under acidic conditions (pH 6.5) but binding weakly under neutral (pH 7.4) conditions. Based on screening a non-immune human antibody library and antibody affinity maturation, we initially generated antibodies with cross-species reactivity for human and mouse EGFR. A structure model was subsequently constructed and interrogated for hotspots affecting pH-dependent binding, which supported development of a cross-reactive pH-dependent anti-EGFR antibody, G532. Compared with its non-pH-dependent antibody variant, G532 exhibits improved tumor selectivity, tumor penetration, and antitumor activity. Thus, beyond showing that pH-dependent anti-EGFR antibodies can overcome multiple limitations with antibody-based cancer therapies targeting EGFR, our study illustrates a structure-guided antibody-antigen binding pH-dependency engineering strategy to enhance antibody tumor selectivity and tumor penetration, which can inform the future development of antibody-based cancer therapies targeting other ubiquitously expressed molecules., Competing Interests: The authors declare no competing interests., (© 2022 The Authors.)

The Gram-negative bacterium Sideroxydans lithotrophicus ES-1 (ES-1) grows on FeCO3 or FeS at oxic-anoxic interfaces at circumneutral pH, and the ES-1-mediated Fe(II) oxidation occurs extracellularly. However, the molecular mechanisms underlying ES-1’s ability to oxidize Fe(II) remain unknown. Survey of the ES-1 genome for candidate genes for microbial extracellular Fe(II) oxidation revealed that it contained a three-gene cluster encoding homologues of MtrA, MtrB and CymA of Shewanella oneidensis MR-1 (MR-1) that are involved in extracellular Fe(III) reduction. Homologues of MtrA and MtrB were also involved in extracellular Fe(II) oxidation by Rhodopseudomonas palustris TIE-1. To distinguish them from those found in MR-1, the identified homologues were named MtoAB and CymAES-1. Cloned mtoA partially complemented an MR-1 mutant without MtrA with regards to ferrihydrite reduction. Characterization of purified MtoA showed that it was a decaheme c-type cytochrome and oxidized soluble Fe(II). Oxidation of Fe(II) by MtoA was pH- and Fe(II)-complexing ligand-dependent. Under conditions tested, MtoA oxidized Fe(II) from pH 7-9 with the optimal rate at pH 9. MtoA oxidized Fe(II) complexed with different ligands at different rates. The reaction rates followed the order Fe(II)Cl2 > Fe(II)-citrate > Fe(II)-NTA > Fe(II)-EDTA with the second-order rate constants ranging from 6.3 × 10-3 μM-1s-1 for oxidation of Fe(II)Cl2 to 1.0 × 10-3 μM-1s-1 for oxidation of Fe(II)-EDTA. Thermodynamic modeling shows that redox reaction rates for the different Fe(II)-complexes correlated with their respective estimated reaction-free energies. Collectively, these results demonstrate that MtoA is a functional Fe(II)-oxidizing protein and, by working in concert with MtoB and CymAES 1, may oxidize Fe(II) at the bacterial surface and transfer released electrons across the bacterial cell envelope to the quinone pool in the inner membrane during extracellular Fe(II) oxidation by ES-1.

[Display omitted] • Chondroitin sulfate (ChS) coated fucoxanthin- gliadin nanoparticles (FUC-Gli NPs). • The driving forces of the Gli-ChS NPs formation were related to pH. • Gli-ChS NPs generally increased the stability of FUC against UV irradiation. • Adding ChS to FUC-Gli NPs enhanced their stabilities to ionic strength and heat. • The system has the potential for sustained and targeted release of FUC in the body. In this study, the fucoxanthin (FUC)-loaded gliadin nanoparticles (Gli NPs) stabilized by chondroitin sulfate (ChS) were fabricated. Results showed that the particle size and turbidity of Gli-ChS NPs were highly pH-dependent. Hydrogen bond, electrostatic interaction and hydrophobic interaction were involved in the formation of Gli-ChS NPs. The surface hydrophobicity of Gli NPs decreased remarkably after coating with ChS. FUC-Gli-ChS NPs increased the stability of FUC against heating and ultraviolet (UV) irradiation. Adding ChS to FUC-Gli NPs enhanced their stabilities to ionic strength and thermal treatment, especially in an acidic environment. Furthermore, FUC-loaded Gli-ChS NPs inhibited the FUC release in simulated gastric fluid (SGF), while enhanced the release of FUC in simulated intestinal fluid (SIF) and simulated colonic fluid (SCF). In summary, this work has important practical significance for the development of Gli NPs as nano-delivery systems for FUC or other hydrophobic compounds. [ABSTRACT FROM AUTHOR]

Highlights: [•] pH had an effect on the microstructure and photochromic properties of composite films. [•] The intensity of absorbance was decreased with increase of pH after UV irradiated. [•] Responsiveness was related to microstructure’s change generated by different pH. [ABSTRACT FROM AUTHOR]

Highlights: [•] ZVI-mediated advanced oxidation was applied to degrade acid orange II (AOII). [•] Lower pH in aqueous media was favorable for AOII degradation in ZVI/O2 system. [•] The measurement of H2O2 and Fe2+ demonstrated role of Fenton reaction in ZVI/O2 system at low pH. [•] OH produced via Fenton reaction was reactive species to degrade AOII in ZVI/O2 system. [ABSTRACT FROM AUTHOR]

The well-defined block polyampholyte poly(acrylic acid)-b-poly(2-dimethylamino)ethyl methacrylate (PAA-b-PDMAEMA) was synthesized by sequential atom transfer radical polymerization (ATRP) using protected group chemisty. The block polyampholyte exhibited so-called “schizophrenic” micellization behavior at different pH values. The PAA-core micelles, PDMAEMA-core micelles, and a kind of polyeletrolyte complex were formed in acidic pH (pH < 4.5), basic pH (pH > 9.0), and neutral pH region (5.5–8.5), respectively. The temperature responsive behaviors of the micelles and the complex formed in neutral environment were studied in detail via dynamic light scattering (DLS) and UV-vis transmittance. Salt effect on the temperature responsive behavior was also discussed. [Supplementary materials are available for this article. Go to the publisher's online edition of Soft Materials orhttp://pubs.acs.orgfor the following free supplemental resource(s): Synthesis of PtBA-b-PDMAEMA,1H NMR spectra of block copolymer and TEM image of block copolymer at aqueous solution with NaCl]” [ABSTRACT FROM AUTHOR]

Some high-affinity functional groups or resonant molecules were often used as probe molecules adsorbed on silver nanoparticles for Surface-enhanced Raman scattering (SERS). However, it is still unclear how the attached molecules interact with the silver nanoparticles' surface, and how the anchoring groups affect the optical and electronic properties of molecules. Here, we report that surface-enhanced Raman studies of two organic compounds; rhodamine 6G (R6G) and its aminated derivative (R-NH2) have very different functional groups for surface binding but nearly identical SERS spectroscopic properties at pH = 7 and UV-vis at pH = 3, respectively. A surprise was found that under the same experimental conditions, the SERS signal intensity for R6G is nearly 50-fold higher than that of R-NH2. Furthermore, the pH-dependent study reveals that the structure of R6G is irreversibly stabilized or 'locked' in its form and no longer responsive to pH changes. In contrast, R-NH2 is still sensitive to pH, and can be switched between its open-ring and closed-ring structures. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

By controlling the pH of the reaction system, a dilacunaryγ-Keggin silicotungstate [Cu(en)2(H2O)][H2en]{γ-SiW10O36[Cu(en)2(H2O)]2}·7.5H2O (1) (en = ethylenediamine) has been hydrothermally synthesized by the reaction of CuCl2withα-H4SiW12O40and characterized by IR spectra, thermogravimetric analysis, and single-crystal X-ray diffraction. The product is prepared in the pH range 7.9–8.2, which reveals that pH plays a key role in the assembly of saturatedα-H4SiW12O40to dilacunary [γ-SiW10O36]8−polyoxometalate. The polyoxoanion {γ-SiW10O36[Cu(en)2(H2O)]2]}4−of1presents a rare [γ-SiW10O36]8−-retaining structure, in which two lacunary sites of [γ-SiW10O36]8−are unoccupied, meanwhile, two [Cu(en)2(H2O)]2+groups are grafted on either side of the [γ-SiW10O36]8−unit by Cu–O–W bond. [ABSTRACT FROM AUTHOR]

By controlling the pH of the reaction system, a dilacunary γ-Keggin silicotungstate [Cu (en)2(H2O)][H2en]{γ-SiW10O36[Cu(en)2(H2O)]2}-7.5H2O (1) (en = ethylenediamine) has been hydrothermally synthesized by the reaction of CuCl2 with α-H4SiW12O40to and characterized by 1R spectra, thermogravimetric analysis, and single-crystal X-ray diffraction. The product is prepared in the pH range 7.9-8.2, which reveals that pH plays a key role in the assembly of saturated α-H4SiW12O40to dilacunary [γ-SiW10O36]8- polyoxometalate. The polyoxoanion {γ-SiW10O36[Cu (en)2(H2O)]2]}4- of 1 presents a rare [γ-SiW10O36]8--retaining structure, in which two lacunary sites of [γ-SiW10O36]8- are unoccupied, meanwhile, two [Cu(en)2(H2O)]2+ groups are grafted on either side of the [γ-SiW10O36]8- unit by Cu-O-W bond. [ABSTRACT FROM AUTHOR]

Developing efficient and recyclable membranes for water contaminant removal still remains a challenge in terms of practical applications. Herein, a recyclable membrane constituted of polyacrylonitrile-graphene and oxide-polydopamine was fabricated and demonstrated efficient adsorption capacities with respect to heavy metal ions (62.9 mg g -1 of Cu 2+ ion, CuSO 4 50 mg L -1 ) and organic dye molecules (306.7 mg g -1 of methylene blue and 339.6 mg g -1 of eriochrome black T, MB/EBT 50 mg L -1 ). The polyacrylonitrile fibers provide the skeleton of the membrane, while the graphene oxide and polydopamine endow the membrane with hydrophilicity, which is favorable for the adsorption of pollutants in water. Benefitting from the protonation and deprotonation effects of graphene oxide and polydopamine, the obtained membrane demonstrated promotion of the selective adsorption or desorption of pollutant molecules. This guarantees that the adsorbed pollutant molecules can be desorbed promptly from the membrane through simple pH adjustment, ensuring the reusability of the membrane. After ten adsorption-desorption cycles, the membrane could still maintain a desirable adsorption capacity. In addition, compared with other, similar membranes reported, this composite membrane displays the highest mechanical stability. This work puts forward an alternative strategy for recyclable membrane design and expects to promote the utilization of membrane techniques in practical wastewater treatment.

Abstract: This study examined the reaction of methylene blue (MB) with tunneled manganese oxide pyrolusite regarding pH and reaction time. MB was cleaved through N-demethylation, in which reaction azure B (AB), azure A (AA), azure C (AC), and thionin (TH) were stepwise generated at all tested pH. Pyrolusite predominantly serves as the oxidant in the oxidative degradation of MB at a pH under the pHiep of pyrolusite (4.70) while playing the role of the catalyst at pH higher than pHiep. Among all oxidative products and original MB molecule, TH is the alone compound adsorbed onto the pyrolusite surface at all tested pH. However, the quantity of adsorbed TH increases with pH because of the stronger affinity between the cationic TH molecule and the more negatively charged surface of pyrolusite with pH increasing. Because the lattice oxygen and surface hydroxyl groups form excited oxygen firstly to cause the oxidation of MB, the tunneled pyrolusite with less constrained corner and edge oxygen catalytically promote the oxidation reaction at pH beyond pHiep. The vacancy of the consumed lattice oxygen forms the active sites for the other oxidation and could be replenished by molecular oxygen to complete a catalytic cycle. [Copyright &y& Elsevier]

Abstract: This work investigated the capability of a new nanoparticulate system, based on terpolymer of starch, polymethacrylic acid and polysorbate 80, to load and release doxorubicin (Dox) as a function of pH and to evaluate the anticancer activity of Dox-loaded nanoparticles (Dox-NPs) to overcome multidrug resistance (MDR) in human breast cancer cells in vitro. The Dox-NPs were characterized by Fourier transform infrared spectroscopy (FTIR), isothermal titration calorimetry (ITC), transmission electron microscopy (TEM), and dynamic light scattering (DLS). The cellular uptake and cytotoxicity of the Dox-loaded nanoparticles were investigated using fluorescence microscopy, flow cytometry, and a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay. The nanoparticles were able to load up to 49.7±0.3% of Dox with a high loading efficiency of 99.9±0.1%, while maintaining good colloidal stability. The nanoparticles released Dox at a higher rate at acidic pH attributable to weaker Dox–polymer molecular interactions evidenced by ITC. The Dox-NPs were taken up by the cancer cells in vitro and significantly enhanced the cytotoxicity of Dox against human MDR1 cells with up to a 20-fold decrease in the IC50 values. The results suggest that the new terpolymeric nanoparticles are a promising vehicle for the controlled delivery of Dox for treatment of drug resistant breast cancer. [Copyright &y& Elsevier]

Abstract: A layer of PEG (poly(ethylene glycol))-galactose was successfully grafted onto the external surface of mesoporous silica nanoparticles (MSNs) via a new silane-free approach, while the internal surface of MSNs was preserved for the encapsulation of the widely used anti-cancer drug of doxorubicin (DOX). The nanosized morphology and ordered structure of the synthesized drug delivery vehicles were verified by XRD and TEM observations. The successful grafting of PEG layer and peripherally exposed galactose ligands on the external surface of MSNs (abbreviated as MSNs-P/G) was confirmed by FT-IR and solid 13C NMR. The high-density PEG layer effectively reduced the human serum protein (HSP) adsorbance to the surface of MSNs. The maximum DOX loading amount reached as high as 900mg/g and the loaded drug released in a pH-dependent way. Both confocal laser scanning microscopy (CLSM) observation and flow cytometry measurements supported the facts that cellular uptake of MSNs-P/G was significantly higher than that of the pristine MSNs benefitting from the galactose-receptor-mediated endocytosis process. This was consistent with the higher cytotoxicity observed with the DOX@MSNs-P/G against the HepG2 cell line by MTT measurements. [Copyright &y& Elsevier]

A Pluronic®-based pH-sensitive multiblock co-polymer thermogel has been proposed for sustained release of therapeutic agents. Hydrophobic small-molecule drugs (paclitaxel and camptothecin) and model hy-drophilic macromolecules (fluorescein-labeled dextrans of molecular mass 10, 20, 40, 150 and 250 kDa) were successfully loaded into and released from the thermogels. Drug-loaded polymer solutions were characterized for gelation behavior and micelle size. Drug loading increased the size of the multiblock co-polymer micelles from 20 to 100 nm. The co-polymer improved paclitaxel and camptothecin loading in an aqueous solution by 6900- and 1050-fold, respectively, compared to their solubility in water. The ther-mogels released loaded drugs in a pH-dependent fashion, regardless of their properties. At pH 5.0 and 6.5, paclitaxel and camptothecin completely released in 4 and 15 days, respectively, by a combined mechanism of diffusion and erosion. At neutral pH, diffusion predominated gel erosion to sustain the drug release up to 40 days. Fluorescein-labeled dextran release from the thermogels showed a similar pH-dependent trend as the hydrophobic small molecule drugs. However, dextran release at neutral pH was entirely dependent on the molecular mass of the dextran. Low-molecular-mass (10 and 20 kDa) dextrans were completely re-leased in 12 and 21 days, respectively, while high-molecular-mass (≥40 kDa) dextrans being continuously released over 36 days, indicating that the threshold of molecular weight necessary for sustained release of a hydrophilic macromolecule from this thermogel (e.g., enzymes, monoclonal antibodies and immunotoxins) is 40 kDa. Taken together, the MBCP thermogel showed potential as a controlled drug-delivery system that showed sustained release of both hydrophilic and lipophilic molecules. [ABSTRACT FROM AUTHOR]

Four-arm star block polymers consisting of hydrophobic poly(ϵ-caprolactone) (PCL) block and hydrophilic poly(2-(diethylamino) ethyl methacrylate)) (PDEAEMA) block were successfully synthesized by ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Chain lengths of PDEAEMA segments were varied to obtain a series of star copolymers with different hydrophilic/hydrophobic ratio, which were desired for self-assembly study. Dynamic light scattering (DLS) and transmission electron microscopic (TEM) were used to study their self-assembly behavior. In the PBS solution with different pH value, the star polymers formed micelles or nanoparticles. Furthermore, the morphologies of the micelles were also pH-dependent. Critical micelle concentrations of star copolymers changed from 5.0 to 17.5 mg/L with the increase of hydrophilic block length or the pH decrease. Moreover, a steady increase was found on the micelles diameters when the pH decreased from 7.0 to 3.0. The low CMC value and slight changes on micelle diameter indicated that the micelle remained stable under the changing external stimulus. [ABSTRACT FROM PUBLISHER]

Abstract: Six complexes based on a flexible tripodal ligand H3TTTA (2,2′,2″-[1,3,5-triazine-2,4,6-triyltris(thio)]tris-acetic acid) have been hydrothermally synthesized and structurally characterized. X-ray single-crystal diffractions reveal that they have rich structural chemistry: mononuclear, [Zn(HTTTA)(2,2′-bpy)(H2O)3] n (1); dimeric metallamacrocycle, [Zn(HTTTA)(2,2′-bipy)(H2O)] n (2) and [Cd(HTTTA)(2,2′-bipy)(H2O)·H2O] n (3); two-dimensional networks with binodal (3,6)-connected CdI2 topology based on linear trinuclear M 3(μ 2–CO2)4(μ 2–CO2)2 SBUs (Secondary Building Units), [M 3(TTTA)2(2,2′-bipy)2(H2O)m·nH2O] n (M=Zn·4, m=0, n=4; Cd·5 and Mn·6, m=2; n=2). The value of pH and the metal ions has large influences on the resulting structures. The flexible tricarboxylic acid exhibits four coordination modes from monodentate to μ 6-bridge. Fluorescence and magnetic properties of the complexes have also been investigated in details. [Copyright &y& Elsevier]

Abstract: Shell cross-linked (SCL) micelles were constructed based on the diblock copolymer poly(t-butyl acrylate)-b-poly(2-dimethylamino)ethyl methacrylate (PtBA-b-PDMAEMA) which was synthesized by sequential atom transfer radical polymerization (ATRP). Using trifluoroacetic acid (TFA) to hydrolyze the SCL micelles, zwitterionic SCL micelles were prepared. The hydrophilicity, size, and softness of the core and the shell of the micelles can be tuned independently by adjusting the pH. At low pH (3.4), the micelles turned into nanoparticles with compact cores and swollen shells; at neutral medium (6.8), the SCL micelles were entirely hydrophilic; at pH 11.6, a double-layer cage-like nanostructure was observed. Moreover, the inner and outer layers of the nanocage had opposite behaviors to the pH stimulus. The existence of tunable nanostructures of these zwitterionic SCL micelles could be proved by the ratio of gyration radius (R g) to hydrodynamic radius (R h) and SEM micrographs. [Copyright &y& Elsevier]

The crystal structures of BB2672 and SPO0826 were determined to resolutions of 1.7 and 2.1 Å by single-wavelength anomalous dispersion and multiple-wavelength anomalous dispersion, respectively, using the semi-automated high-throughput pipeline of the Joint Center for Structural Genomics (JCSG) as part of the NIGMS Protein Structure Initiative (PSI). These proteins are the first structural representatives of the PF06684 (DUF1185) Pfam family. Structural analysis revealed that both structures adopt a variant of the Bacillus chorismate mutase fold (BCM). The biological unit of both proteins is a hexamer and analysis of homologs indicates that the oligomer interface residues are highly conserved. The conformation of the critical regions for oligomerization appears to be dependent on pH or salt concentration, suggesting that this protein might be subject to environmental regulation. Structural similarities to BCM and genome-context analysis suggest a function in amino-acid synthesis. [ABSTRACT FROM AUTHOR]

Abstract: Raman and SERS spectra of homodipeptide Gly-Gly and Gly were recorded and compared in this paper, and band assignment for the functional groups contained in these molecules was analyzed in detail. Time-dependent and pH-dependent SERS spectra of Gly-Gly molecule adsorbed on nano-colloidal silver surface were also studied. The time-dependent SERS spectra of Gly-Gly are characterized by the increase in intensity of bands primarily representing the vibrational signatures emanating from the amino and amide moiety of Gly-Gly molecule. It is found that the adsorption style of Gly-Gly on the silver colloid changes as time goes on; at 5min after adding the sample to the silver colloid, Gly-Gly adsorbs on silver surface firstly through the carboxylate, amino and amide groups, and then the carboxylate group is far away from the silver surface at 10min to 3days. The SERS variation of Gly-Gly with the change of pH suggests that the adsorption style is pH-dependent, the different adsorption behavior of the Gly-Gly occurs on silver surface at different pH values. [Copyright &y& Elsevier]

Two novel organic–inorganic hybrid vanadoantimonate compounds, [Zn2(dien)3][{Zn(dien)}2V16Sb4O42(H2O)]·4H2O ( 1) and [Zn(dien)2]2 [{Zn(dien)}2(V14Sb8O42)2(H2O)]·4H2O ( 2) (dien = Diethylenetriamine), have been synthesized hydrothermally at different pH value, and structurally characterized by elemental analyses, FT-IR, XPS, TGA and single crystal X-ray diffraction analysis. Compound 1 is composed of the rare [V16Sb4O42]8− cluster covalently linked by two [Zn(dien)]2+ coordination cations to yield a novel one-dimensional linear chain. Compound 2 exhibits a one-dimensional zigzag chain constructed from the [V14Sb8O42]4− cluster and [Zn(dien)]2+ coordination polymer. The two examples represent the first one-dimensional assemblies based on vanadoantimonate cluster and the metal–organic complex moieties. [ABSTRACT FROM AUTHOR]

Synthetic collagen model peptides containing carboxylate-modified hydroxyproline residues (PE) have been shown to form a collagen triple helix at low pH ( 1 ). Based on the fact that PE-containing peptides unfold on demand by altering the pH, we investigated the folding kinetics of a series of these collagen-based peptides. Refolding data indicated that the introduction of PE residues within a peptide affects the stability and refolding of the collagen peptides through electrostatic interactions and steric hindrance. Moreover, the specific placement of the PE residues within the collagen peptides allowed for selective testing for possible nucleation sites at the termini or the center of the peptides. Specifically, the data demonstrated that collagen peptides may nucleate from either terminally or internally located repeating sequences of Pro-Hyp-Gly. These studies indicate that the PE residue may play a useful role as a tool for studying the folding mechanism of synthetic collagen peptides. [ABSTRACT FROM AUTHOR]

We hypothesize that bacterially synthesized nutrients in the large intestine may significantly influence the nutritional status of humans and, specifically, that of the colonocytes. In vivo research with human subjects in this area has been extremely limited because of the absence of a noninvasive means to quantitatively deliver test doses of nutrients, or their precursors, to the colon. The purpose of this study was to design and test the effectiveness of a pH-dependent coating in delivering intact placebo caplets to the large intestine. Barium sulphate caplet cores (19.1 mm × 9.7 mm) were coated with 2 different pH-dependent acrylic copolymer products, Eudragit L100 and S100, in either a 1:0 ratio (100% Eudragit L100) or 3:1 ratio (75% Eudragit L100 and 25% S100). The disintegration profile of each formulation was determined through in vitro testing, then caplets were sequentially administered to 10 healthy volunteers, and monitored in vivo via serial abdominal fluoroscopic images. Test caplets with the 3:1 coating formulation had a 40% higher colon-targeting specificity compared with the 1:0-coated caplets, and tended to begin disintegrating at a later time after administration (p = 0.09). The total time from administration to complete disintegration was also significantly longer for the 3:1-coated caplets (p = 0.003). These results suggest that barium sulphate caplets with a 3:1 acrylic copolymer coating formulation ratio (Eudragit L100 and S100) may be a suitable delivery system for quantifying the biosynthesis of nutrients in the human large intestine and measuring their absorption across the colonic epithelium. [ABSTRACT FROM AUTHOR]