Assessing Weak Anion Binding to Small Peptides.

Since Hofmeister's seminal studies in the late 19th century, it has been known that salts and buffers can drastically affect the properties of peptides and proteins. These Hofmeister effects can be conceived of in terms of three distinct phenomena/mechanisms: water-salt interactions that indirectly induce the salting-out of a protein by water sequestration by the salt, and direct salt-protein interactions that can either salt-in or salt-out the protein. Unfortunately, direct salt-protein interactions responsible for Hofmeister effects are weak and difficult to quantify. As such, they are frequently construed of as being nonspecific. Nevertheless, there has been considerable effort to better specify these interactions. Here, we use pentapeptides to demonstrate the utility of the H-dimension of nuclear magnetic resonance (NMR) spectroscopy to assess anion binding using N-H signal shifts. We qualify binding using these, demonstrating the upfield shifts induced by anion association and revealing how they are much larger than the corresponding downfield shifts induced by magnetic susceptibility and other ionic strength change effects. We also qualify binding in terms of how the pattern of signal shifts changes with point mutations. In general, we find that the observed upfield shifts are small compared with those induced by anion binding to amide-based hosts, and MD simulations suggest that this is so. Thus, charge-diffuse anions associate mostly with the nonpolar regions of the peptide rather than directly interacting with the amide N-H groups. These findings reveal the utility of 1H NMR spectroscopy for qualifying affinity to peptides─even when affinity constants are very low─and serve as a benchmark for using NMR spectroscopy to study anion binding to more complex systems.

A mixed-mode reversed-phase/strong-anion-exchange stationary phase: Analyte-retention stability and application in the analysis of nonsteroidal anti-inflammatory drugs.

Mixed-mode reversed-phase/anion-exchange chromatography (RP/AEX) is an effective method for the chromatographic analysis of acidic drugs because it combines reversed-phase chromatography (RP) with anion-exchange chromatography (AEX). However, the result repeatability for the RP/AEX analysis of acidic drugs is frequently compromised by the detrimental effects of residual silanol groups in an RP/AEX stationary phase on peak separation and analyte retention. In this study, an RP/weak-AEX stationary phase with amino anion-exchange groups, Sil-AA, was prepared. Subsequently, an RP/strong-AEX stationary phase, Sil-PBQA, was prepared by replacing the amino groups in Sil-AA with a benzene ring and a benzyl-containing quaternary ammonium salt. The chromatographic behaviors of Sil-PBQA and Sil-AA were compared, and the effect of residual silanol groups on the chromatographic behavior of an RP/AEX stationary phase was evaluated. Residual silanol groups not only caused additional electrostatic interactions for acidic analytes, but also competed with the analytes for the anion-exchange sites in an RP/AEX stationary phase. The effects of different salt-containing mobile-phase systems on the analyte-retention behavior of Sil-PBQA were investigated to develop a method that enhanced the repeatability of the RP/AEX acidic-analyte-analysis results obtained using Sil-PBQA and facilitated the separation of nonsteroidal anti-inflammatory drugs on Sil-PBQA. The ideas presented in this paper can improve the separation of peaks and repeatability of results in the RP/AEX analysis of acidic drugs.

Separation of inorganic anions on reversed-phase C18 columns with a phosphomolybdate mobile phase.

Reversed-phase high performance liquid chromatography (RP-HPLC) is the most widely used chromatographic method. In addition to hydrophobic interactions, additional interactions such as electrostatic interactions may participate in the retention behaviour of an analyte. This makes it possible to use RP-HPLC for many types of analyte. We describe a simple method for separating inorganic anions on a C18 column, in which retention of inorganic anions is almost entirely due to electrostatic interactions. This leads to rapid separations as well as higher theoretical plate numbers. We used 2 mM phosphoric acid containing a low concentration of disodium molybdate as the mobile phase, which allows UV detection of non-UV-absorbing anions. With this method, we determined eight inorganic anions including several non-UV-absorbing anions photometrically at 220 nm. The detection limits of the examined eight inorganic anions calculated at a signal-to-noise ratio of 3 were between 0.3 and 10 µM. The detector response was linear over three orders of magnitude of inorganic anion concentration. The proposed RP-HPLC/UV method was successfully applied to determine inorganic anions in some water samples.

[Preparation of a macroporous anion exchange chromatographic medium by polyamine grafting and evaluation of its protein-adsorption behavior].

The macroporous anion exchange chromatographic medium (FastSep-PAA) was prepared through grafting polyallylamine (PAA) onto polyacrylate macroporous microspheres (FastSep-epoxy). The effects of the synthesis conditions, including the PAA concentration, reaction time, and reaction solution pH, on the ion exchange (IC) of the medium were investigated in detail. When the PAA concentration, reaction time, and reaction solution pH were increased, the IC of the medium increased, and optimal synthesis conditions were then selected in combination with changes of protein binding capacity. A scanning electron microscope was used to examine the surface morphology of the medium. The medium possessed high pore connectivity. Furthermore, the pore structure of the medium was preserved after the grafting of PAA onto the macroporous microspheres. This finding demonstrates that the density of the PAA ligands does not appear to have any discernible impact on the structure of the medium; that is, no difference in the structure of the medium is observed before and after the grafting of PAA onto the microspheres. The pore size and pore-size distribution of the medium before and after grafting were determined by mercury intrusion porosimetry and the nitrogen adsorption method to investigate the relationship between pore size (measured in the range of 300-1000 nm) and protein adsorption. When the pore size of the medium was increased, its protein binding capacity did not exhibit any substantial decrease. An increase in pore size may hasten the mass transfer of proteins within the medium. Among the media prepared, that with a pore size of 400 nm exhibited the highest dynamic-binding capacity (DBC: 70.3 g/L at 126 cm/h). The large specific surface area of the medium and its increased number of protein adsorption sites appeared to positively influence its DBC. When the flow rate was increased, the protein DBC decreased in media with original pore sizes of less than 700 nm. In the case of the medium with an original pore size of 1000 nm, the protein DBC was independent of the flow rate. The protein DBC decreased by 3.5% when the flow rate was increased from 126 to 628 cm/h. In addition, the protein DBC was maintained at 57.7 g/L even when the flow velocity was 628 cm/h. This finding reveals that the diffusion rate of protein molecules at this pore size is less restricted and that the prepared medium has excellent mass-transfer performance. These results confirm that the macroporous polymer anion exchange chromatographic medium developed in this study has great potential for the high-throughput separation of proteins.

Singlet Oxygen and Superoxide Anion Radical Detection by EPR Spin Trapping in Thylakoid Preparations.

Reactive oxygen species (ROS) are produced by energy transfer and electron transport in plant chloroplast thylakoids at non-toxic levels under normal growth conditions, but at threatening levels under adverse or fluctuating environmental conditions. Among chloroplast ROS, singlet oxygen and superoxide anion radical, respectively, produced by photosystem II (PSII) and PSI, are known to be the major ROS under several stress conditions. Both are very unlikely to diffuse out of chloroplasts, but they are instead capable of triggering ROS-mediated chloroplast operational retrograde signalling to activate defence gene expression in concert with hormones and other molecular compounds. Therefore, their detection, identification and localization in vivo or in biological preparations is a priority for a deeper understanding of their role in (concurrent) regulation of plant growth and defence responses. Here, we present two EPR spin traps, abbreviated as TEMPD-HCl and DEPMPO, to detect and identify ROS in complex systems, such as isolated thylakoids, together with some hints and cautions to perform reliable spin trapping experiments.

Development of a chromatographic method for optimizing the thiol-maleimide coupling of polyoxometalate-polymer hybrids.

The covalent attachment of polyoxometalates (POMs) to polymers has been developed as a strategic approach for the advancement of POM-based hybrid materials with versatile applications. In this study, we utilized thiol-maleimide Michael addition to investigate the kinetics and efficacy of the "one-to-one" conjugation between Keggin type POM and polystyrene. We explored the effects of solvent polarity, catalyst, molecular weight of PS and synthetic strategies on the reaction kinetics and efficiency, by means of reverse-phase high-performance liquid chromatography (RP-HPLC). A series of comparative analysis affirmed the superior efficiency of the one-pot method, particularly when facilitated by the addition of a high-polarity solvent and an excess of maleimide. These findings offer valuable insights into the intricate interplay between reaction conditions, kinetics, and selectivity in thiol-maleimide reactions of POMs and polymers. They hold profound implications for advancing the study of POM-based multifunctional materials and the synthesis of complex hybrid molecules.

Chemical, biochemical, and bioactivity studies on some soda lakes, Wadi El-Natrun, Egypt.

Wadi El-Natrun is one of the most observable geomorphological features in the North-Western Desert of Egypt; it contains several old saline and saline soda lakes. This study investigates physicochemical and biochemical characteristics and estimates the total phenolic content (TPC), total flavonoid content (TVC), and bioactivities of sediment, cyanobacteria, and brine shrimp (Artemia salina) in soda lakes, i.e., El-Hamra Lake 1 (H1) and El-Hamra Lake 2 (H2). These soda lakes are unique extreme ecosystems characterized by high pH (> 9.3), high alkalinity, and salinity. Some extremophilic microorganisms are hosted in this ecosystem. The results revealed that the chemical water type of studied lakes is soda-saline lakes according to the calculated percentage sequence of major cations and anions. Sodium ranked first among major cations with an abundance ratio of e% 58, while chloride came first among anions with an abundance ratio of e% 71, and bicarbonate and carbonate occupied the last rank with an abundance of 6%. The biochemical investigations showed that TPC and TVC are present in concern contents of sediment, cyanobacteria, and brine shrimp (A. salina) which contribute 89% of antioxidant capacity and antimicrobial activities. Thus, this study helps better understand the chemical and biochemical adaptations in soda lake ecosystems and explores natural sources with potential applications in antioxidant-rich products and environmental conservation efforts.

Improving the sensing sensitivity of silver nanoparticle-based colorimetric biosensors from the point of salt.

The sensing sensitivity was improved for silver nanoparticles (AgNPs)-based colorimetric biosensors by using the most suitable salt to induce AgNPs aggregation. As for the salt composed of low-affinity anion and monovalent cation, the cation-dependent charge screening effect was the driving force for AgNPs aggregation. Apart from the charge screening effect, both the bridging of multivalent cation to the surface ligand of AgNP and the interaction between anion and Ag contributed to inducing AgNPs aggregation. Considering the higher aggregation efficiency of AgNPs resulted in a narrower sensing range, salt composed of low-affinity anion and monovalent cation was recommended for AgNPs-based colorimetric analysis, which was confirmed by fourfold higher sensitivity of DNA-21 detection using NaF than NaCl. This work inspires further thinking on improving the sensing performance of metal nanomaterials-based sensors from the point of colloidal surface science.

Ionized acrylamide-based copolymer / terpolymer hydrogels for recovery of positive and negative heavy metal ions.

In this study, we explored the effective capture of both cations and anions onto a single adsorbent. Acrylamide (AAm) served as the polymer backbone, onto which co-monomers sodium p-styrenesulfonate (SS) and N,N-dimethylaminopropyl acrylamide (DMAPAA) were grafted, creating ionized polymer hydrogel adsorbents. These adsorbents were engineered for the synergistic separation and recovery of heavy metal cations and anions from concentrated solutions, focusing specifically on industrially significant ions such as Ni2+-, Cu2+, Zn2+ and (Cr2O7)2-. The adsorption and desorption behaviors of the AAm terpolymer hydrogels were investigated across various pH solutions, considering the competition and concentrations of these specific metal ions. Moreover, the study delved into the effects of the internal pH environment within the hydrogel adsorbents, determining its impact on the type of metal adsorbed and the adsorption capacity. Our findings indicated that the adsorption of cations was enhanced with a higher proportion of SS relative to DMAPAA in the hydrogel. In contrast, significant anion capture occurred when the concentration of DMAPAA exceeded that of SS. However, equal ratios of SS and DMAPAA led to a noticeable reduction in the adsorption of both types of substrates, attributed to the counteractive nature of these co-monomers. To enhance the adsorption efficiency, it may be necessary to consider methods for micro-scale separation of the two types of monomers. Additionally, the adsorption capacity was observed to be directly proportional to the swelling capacity of the hydrogels. For complete desorption and separation of the cations and anions from the adsorbent, the application of concentrated NaOH solutions followed by HNO3 was found to be essential. Given the varying concentrations of cation and anion pollutants, often present in heavy metal factory effluents, it is crucial to fine-tune the ratios of DMAPAA and SS during the synthesis process. This adjustment ensures optimized efficiency in the decontamination and recovery of these significant heavy metal ions.

The open channel state in anion channelrhodopsin GtACR1 is a red-absorbing intermediate.

Anion channelrhodopsin GtACR1 is a powerful optogenetic tool to inhibit nerve activity. Its kinetic mechanism was interpreted in terms of the bacteriorhodopsin photocycle, and the L intermediate was assigned to the open channel state. Here, we report the results of the comparison between the time dependence of the channel currents and the time evolutions of the K-like and L-like spectral forms. Based on the results, we question the current view on GtACR1 kinetics and the assignment of the L intermediate to the open channel state. We report evidence for a red-absorbing intermediate being responsible for channel opening.

Mechanical energy triggered piezo-catalyzation of Bi2WO6 nanoplates on ferrate (Fe(VI)) oxidation in alkaline media: Performance and mechanism.

Piezo-electricity, as a unique physical phenomenon, demonstrates high effectiveness in capturing the environmental mechanical energy into polarization charges, offering the possibility to activate the advanced oxidation processes via the electron pathway. However, information regarding the intensification of Fe(VI) through piezo-catalysis is limited. Therefore, our study is the first to apply Bi2WO6 nanoplates for piezo-catalyzation of Fe(VI) to enhance bisphenol A (BPA) degradation. Compared to Fe(VI) alone, the Fe(VI)/piezo/Bi2WO6 system exhibited excellent BPA removal ability, with the degradation rate increased by 32.6% at pH 9.0. Based on the experimental and theoretical results, Fe(VI), Fe(V), Fe(IV) and •OH were confirmed as reaction active species in the reaction, and the increased BPA removal mainly resulted from the enhanced formation of Fe(IV)/Fe(V) species. Additionally, effects of coexisting anions (e.g., Cl-, NO3-, SO42- and HCO3-), humic acid and different water matrixes (e.g., deionized water, tap water and lake water) on BPA degradation were studied. Results showed the Fe(VI)/piezo/Bi2WO6 system still maintained satisfactory BPA degradation efficiencies under these conditions, guaranteeing future practical applications in surface water treatment. Furthermore, the results of intermediates identification, ECOSAR calculation and cytotoxicity demonstrated that BPA degradation by Fe(VI)/piezo/Bi2WO6 posed a diminishing ecological risk. Overall, these findings provide a novel mechanical energy-driven piezo-catalytic approach for Fe(VI) activation, enabling highly efficient pollutant removal under alkaline condition.

Effects of common dissolved anions on the efficiency of Fe0-based remediation systems.

Quiescent batch experiments were conducted to evaluate the influences of Cl-, F-, HCO3-, HPO42-, and SO42- on the reactivity of metallic iron (Fe0) for water remediation using the methylene blue (MB) method. Strong discoloration of MB indicates high availability of solid iron corrosion products (FeCPs). Tap water was used as an operational reference. Experiments were carried out in graduated test tubes (22 mL) for up to 45 d, using 0.1 g of Fe0 and 0.5 g of sand. Operational parameters investigated were (i) equilibration time (0-45 d), (ii) 4 different types of Fe0, (iii) anion concentration (10 values), and (iv) use of MB and Orange II (O-II). The degree of dye discoloration, the pH, and the iron concentration were monitored in each system. Relative to the reference system, HCO3- enhanced the extent of MB discoloration, while Cl-, F-, HPO42-, and SO42- inhibited it. A different behavior was observed for O-II discoloration: in particular, HCO3- inhibited O-II discoloration. The increased MB discoloration in the HCO3- system was justified by considering the availability of FeCPs as contaminant scavengers, pH increase, and contact time. The addition of any other anion initially delays the availability of FeCPs. Conflicting results in the literature can be attributed to the use of inappropriate experimental conditions. The results indicate that the application of Fe0-based systems for water remediation is a highly site-specific issue which has to include the anion chemistry of the water.

Salt-Bridged Peptide Anion Gaseous Structures Enable Efficient Negative Ion Electron Capture Dissociation.

We previously discovered that electron attachment to gaseous peptide anions can occur within a relatively narrow electron energy range. The resulting charge-increased radical ions undergo dissociation analogous to conventional cation electron capture/transfer dissociation (ECD/ETD), thus enabling a novel tandem mass spectrometry (MS/MS) technique that we termed negative ion electron capture dissociation (niECD). We proposed that gaseous zwitterionic structures are required for niECD with electron capture either occurring at or being directed by a positively charged site. Here, we further evaluate this zwitterion mechanism by performing niECD of peptides derivatized to alter their ability to form zwitterionic gaseous structures. Introduction of a fixed positive charge tag, a highly basic guanidino group, or a highly acidic sulfonate group to promote zwitterionic structures in singly charged anions, rescued the niECD ability of a peptide refractory to niECD in its unmodified form. We also performed a systematic study of five sets of synthetic peptides with decreasing zwitterion propensity and found that niECD efficiency decreased accordingly, further supporting the zwitterion mechanism. However, traveling-wave ion mobility-mass spectrometry experiments, performed to gain further insight into the gas-phase structures of peptides showing high niECD efficiency, exhibited an inverse correlation between the orientationally averaged collision cross sections and niECD efficiency. These results indicate that compact salt-bridged structures are also a requirement for effective niECD.

A Novel Bisquaternary Ammonium Compound as an Anion Sensor-ESI-MS and Fluorescence Study.

Electrospray ionization mass spectrometry (ESI-MS) analysis is frequently associated with noncovalent adduct formation, both in positive and negative modes. Anion binding and sensing by mass spectrometry, notably more challenging compared to cation binding, will have major research potential with the development of appropriate sensors. Here, we demonstrated identification of stable bisquaternary dication adducts with trifluoroacetate (TFA-), Cl- and HSO4- in positive-mode ESI-MS analysis. The observed adducts were stable in MS/MS mode, leading to the formation of characteristic fragment ions containing a covalently bound anion, which requires bond reorganization. This phenomenon was confirmed by computational methods. Furthermore, given that anion detection and anion sensor chemistry have gained significant prominence in chemistry, we conducted an analysis of the fluorescent properties of bisquaternary ammonium compound as a potential anion sensor.

Bioactivity of human dental pulp-derived stem cells with boron-controlled S-PRG filler eluate by anion exchange.

Surface pre-reacted glass-ionomer (S-PRG) filler is a bioactive glass filler capable of releasing various ions. A culture medium to which was added an S-PRG filler eluate rich in boron was reported to enhance alkaline phosphatase (ALP) activity in human dental pulp-derived stem cells (hDPSC). To clarify the role of boron eluted from S-PRG fillers, the modified S-PRG filler eluate with different boron concentrations was prepared by using an anion exchange material. Therefore, elemental mapping analysis of anion exchange material, adsorption ratio, hDPSCs proliferation and ALP activity were evaluated. For statistical analysis, Kruskal-Wallis test was used, with statistical significance determined at p<0.05. ALP activity enhancement was not observed in hDPSC cultured in the medium that contained the S-PRG filler eluate from which boron had been removed. The result suggested the possibility that an S-PRG filler eluate with controlled boron release could be useful for the development of novel dental materials.

Negative Electron Transfer Collision-Induced Dissociation of G-Quadruplexes: Uncovering the Guanine Radical Anion Loss Pathway.

G-quadruplex (G4) DNA can form highly stable secondary structures in the presence of metal cations, and research has shown its potential as a transcriptional regulator for oncogenes in the human genome. In order to explore the interactions of DNA with metal cations using mass spectrometry, employing complementary fragmentation methods can enhance structural information. This study explores the use of ion-ion reactions for sequential negative electron transfer collision-induced dissociation (nET-CID) as a complement to traditional ion-trap CID (IT-CID). The resulting nET-CID data for G4 anions with and without metal cations show an increase in fragment ion type diversity and yield of structurally informative ions relative to IT-CID. The nET-CID yields greater sequence coverage by virtue of fragmentation at the 3'-side of thymine residues, which is lacking with IT-CID. Potassium adductions to backbone fragments in IT-CID and nET-CID spectra were nearly identical. Of note is a prominent fragment resulting from a loss of a 149 Da anion seen in nET-CID of large, G-rich sequences, proposed to be radical anion guanine loss. Neutral loss of neutral guanine (151 Da) and deprotonated nucleobase loss (150 Da) have been previously reported, but this is the first report of radical anion guanine loss (149 Da). Confirmation of the identity of the 149 Da anion results from the examination of the homonucleobase sequence 5'-GGGGGGGG-3'. Loss of a charged adenine radical anion at much lower relative abundance was also noted for the sequence 5'-AAAAAAAA-3'. DFT modeling indicates that the loss of a nucleobase as a radical anion from odd-electron nucleic acid anions is a thermodynamically favorable fragmentation pathway for G.

Separation of the diastereomers of phosphorothioated siRNAs by anion-exchange chromatography under non-denaturing conditions.

In recent years, several small interfering RNA (siRNA) therapeutics have been approved, and most of them are phosphorothioate (PS)-modified for improving nuclease resistance. This chemical modification induces chirality in the phosphorus atom, leading to the formation of diastereomers. Recent studies have revealed that Sp and Rp configurations of PS modifications of siRNAs have different biological properties, such as nuclease resistance and RNA-induced silencing complex (RISC) loading. These results highlight the importance of determining diastereomeric distribution in quality control. Although various analytical approaches have been used to separate diastereomers (mainly single-stranded oligonucleotides), it becomes more difficult to separate all of them as the number of PS modifications increases. Despite siRNA exhibits efficacy in the double-stranded form, few reports have examined the separation of diastereomers in the double-stranded form. In this study, we investigated the applicability of non-denaturing anion-exchange chromatography (AEX) for the separation of PS-modified siRNA diastereomers. Separation of the four isomers of the two PS bonds tended to improve in the double-stranded form compared to the single-stranded form. In addition, the effects of the analytical conditions and PS-modified position on the separation were evaluated. Moreover, the elution order of the Sp and Rp configurations was confirmed, and the steric difference between them, i.e., the direction of the anionic sulfur atom, appeared to be important for the separation mechanism in non-denaturing AEX. Consequently, all 16 peak tops of the four PS modifications were detected in one sequence, and approximately 30 peak tops were detected out of 64 isomers of six PS bonds, indicating that non-denaturing AEX is a useful technique for the quality control of PS-modified siRNA therapeutics.

Functional Studies of Deafness-Associated Pendrin and Prestin Variants.

Pendrin and prestin are evolutionary-conserved membrane proteins that are essential for normal hearing. Dysfunction of these proteins results in hearing loss in humans, and numerous deafness-associated pendrin and prestin variants have been identified in patients. However, the pathogenic impacts of many of these variants are ambiguous. Here, we report results from our ongoing efforts to experimentally characterize pendrin and prestin variants using in vitro functional assays. With previously established fluorometric anion transport assays, we determined that many of the pendrin variants identified on transmembrane (TM) 10, which contains the essential anion binding site, and on the neighboring TM9 within the core domain resulted in impaired anion transport activity. We also determined the range of functional impairment in three deafness-associated prestin variants by measuring nonlinear capacitance (NLC), a proxy for motor function. Using the results from our functional analyses, we also evaluated the performance of AlphaMissense (AM), a computational tool for predicting the pathogenicity of missense variants. AM prediction scores correlated well with our experimental results; however, some variants were misclassified, underscoring the necessity of experimentally assessing the effects of variants. Together, our experimental efforts provide invaluable information regarding the pathogenicity of deafness-associated pendrin and prestin variants.

[Characteristics of anion and cation in rhizosphere soil of saline grassland in North China under different nitrogen addition levels]. / ä¸åŒæ°´å¹³æ°®æ·»åŠ ä¸‹åŽåŒ—ç›æ¸åŒ–è‰åœ°æ ¹é™ åœŸå£¤é˜´é˜³ç¦»å­ç‰¹å¾.

We investigated the effects and mechanisms of nitrogen additions (0, 1, 2, 4, 8, 16, 24, 32 g N·m-2·a-1) on contents of anion and cation in rhizosphere soil, bulk soil, and mixed rhizosphere and bulk soil in the heavily salinized grassland in the agro-pastoral ecotone of North China. The results showed that pH of rhizosphere, mixed and bulk soils decreased significantly with the increases of nitrogen addition levels. Moreover, pH of three soil types under the 32 g N·m-2·a-1 treatment decreased by 1.2, 0.9, and 0.6, respectively, while pH of rhizosphere soil decreased by 0.44 compared with the bulk soil. Na+ content of rhizosphere, mixed and bulk soils significantly decreased, while the NO3- content significantly increased. The proportion of Na+ content in total soluble salt content in rhizosphere soil decreased by 14% and that in bulk soil decreased by 12% after the 32 g N·m-2·a-1 addition. NO3- content increased by 29% in rhizosphere soil and by 26% in bulk soil. There was significant negative correlation between pH and NO3- content, and significant positive correlation between pH and Na+ content. The total soluble salt content of rhizosphere soil under the 32 g N·m-2·a-1 treatment was significantly reduced by 31.5%. Collectedly, nitrogen deposition could reduce soil pH and total soluble salt content of rhizosphere soil and alleviate saline-alkali stress.

Visual Gustation via Regulable Elastic Photonic Crystals.

The unique structural sensitivity of photonic crystals (PCs) endows them with stretchable or elastic tunability for light propagation and spontaneous emission modulation. Hydrogel PCs have been demonstrated to have biocompatibility and flexibility for potential human health detection and environmental security monitoring. However, current elastic PCs still possess a fixed elastic modulus and uncontrollable structural colors based on a tunable elastic modulus, posing considerable challenges for in situ detection, particularly in wearable or portable sensing devices. In this work, we introduced a novel chemo-mechanical transduction mechanism embedded within a photonic crystal nanomatrix, leading to the creation of structural colors and giving rise to a visual gustation sensing experience. By utilizing the captivating structural colors generated by the hydrogel PC, we employ abundant optical information to identify various analytes. The finite element analysis proved the electric field distribution in the PC matrix during stretch operations. The elastic-optical behaviors with various chemical cosolvents, including cations, anions, saccharides, or organic acids, were investigated. The mechanism of the Hofmeister effect regulating the elasticity of hydrogels was demonstrated with the network nanostructure of the hydrogels. The hydrogel PC matrix demonstrates remarkable capability in efficiently distinguishing a wide range of cations, anions, saccharides, and organic acids across various concentrations, mixtures, and even real food samples, such as tastes and soups. Through comprehensive research, a precise relationship between the structural colors and the elastic modulus of hydrogel PCs has been established, contributing to the biomatching elastic-optics platform for wearable devices, a dynamic environment, and clinical or health monitoring auxiliary.