Influence of ultrasound-assisted alkali treatment on the structural properties and functionalities of rice protein

peer-reviewedThe poor solubility of rice protein (RP) limits its applications in food industry. In this study, the effects of ultrasound-assisted alkali (UAA) treatment on the solubility, structure and functional properties of RP were investigated. Using UAA treatment, the solubility of RP increased with increasing alkali concentration, reaching a maximum value of 19.79 mg/mL at an alkali concentration of 0.08 M. The solubility was improved by 230-fold compared to un-treated samples. In addition, a reduction in particle size and degradation of the protein subunit were observed. UAA seemed to unfold the protein internal structural conformation and expose buried functional groups, which are linked to good emulsifying properties and foaming properties. A decrease in zeta potential was also observed after UAA treatment, which could be the reason for the decreased stability of the emulsion. UAA treatment modified the protein structure and significantly improved solubility

Influence of ultrasound-assisted alkali treatment on the structural properties and functionalities of rice protein

The poor solubility of rice protein (RP) limits its applications in food industry. In this study, the effects of ultrasound-assisted alkali (UAA) treatment on the solubility, structure and functional properties of RP were investigated. Using UAA treatment, the solubility of RP increased with increasing alkali concentration, reaching a maximum value of 19.79 mg/mL at an alkali concentration of 0.08 M. The solubility was improved by 230-fold compared to un-treated samples. In addition, a reduction in particle size and degradation of the protein subunit were observed. UAA seemed to unfold the protein internal structural conformation and expose buried functional groups, which are linked to good emulsifying properties and foaming properties. A decrease in zeta potential was also observed after UAA treatment, which could be the reason for the decreased stability of the emulsion. UAA treatment modified the protein structure and significantly improved solubility

Regulating Reactive Oxygen Intermediates of SAzyme via Second-Shell coordination for Selective Aerobic Oxidation

Reactive oxygen species (ROS) regulation for artificial oxidoreductase is a key scientific issue that determines the activity, selectivity, and stability of aerobic reaction. However, the poor understanding of ROS formation mechanism greatly hampers their wider deployment. Herein, inspired by cytochromes P450 affording bound ROS intermediates in O2 activation, we report single-atom FeN4 site with tunable second-shell anion could regulate ROS generating pathways. Remarkably, the second-shell S anion coordinated FeN4 (denoted as FeNSC) delivers 2.4-fold higher oxidase-like activity and only 17% free ROS generation compared to FeNC. The detailed XANES analysis and DFT calculations reveal that the second shell S-doping significantly altered the electronic structure of FeN4 sites, leading to an increase of electron density at Fermi level and the enhanced electron transfer from active sites to the key intermediate *OOH, thereby determining the type of ROS in aerobic oxidation process. FeNC with different second-shell anion were further applied to drive aerobic oxidation reaction with enhanced activity, selectivity, and stability

Elucidating Electrocatalytic Oxygen Reduction Kinetics via Intermediates by Time-Dependent Electrochemiluminescence

Facile evaluation of oxygen reduction reaction (ORR) kinetics for massive electrocatalysts is critical for sustainable fuel cells development and industrial H2O2 production. Despite great success in ORR studies by mainstream strategies, such as membrane electrode assembly, rotation electrode technique and advanced surface-sensitive spectroscopy, the time/spatial distribution of reactive oxygen species (ROS) intermediates in the diffusion layer is still unknown. By time-dependent electrochemiluminescence (Td-ECL), here we report an intermediate-oriented methodology for ORR kinetics analysis. Thanks to multiple ultra-sensitive stoichiometric reactions between ROS and the ECL emitter, except for electron transfer numbers and rate constants, the potential-dependent time/spatial distribution of ROS was successfully obtained for the first time. Such uncovered exclusive information would guide fuel cells and H2O2 production with maximized activity and durability, for instance, a larger overpotential would be beneficial to electrocatalysts of 2e reduction for H2O2 production, because of the high yield of H2O2 and low concentration of attackable O2•. This work would pave the exploration of not only the fundamentals of unambiguous ORR mechanism but also the durability of electrocatalysts for practical applications

Lighting up Electrochemiluminescent Inactive Dyes by Intramolecular Resonance Energy Transfer

By virtue of near-zero optical background and photobleaching, electrochemiluminescence (ECL), an optical phenomenon excited by electrochemical reactions, has drawn extensive attention in both fundamental studies and wide applications especially of ultrasensitive bioassay. Developing diverse ECL emitters is crucial to unlock their multiformity and performances, but remains a formidable challenge, due to the rigorous requirements for ECL. Herein, we report a general intramolecular ECL resonance energy transfer (iECL-RET) strategy to light up ECL-inactive dyes in aqueous solutions using an existing high-performance ECL initiators. As a proof-of-concept, a series of luminol donor-dye acceptor based ECL emitters with near unity RET efficiency and coarse/fine tunable emission wavelengths were demonstrated. Different to previous exploitation of new molecule single-handedly to address all the prerequisites of ECL, each unit in the proposed ECL ensemble performed maximally its own functions. The iECL-RET strategy would greatly expand the family members of ECL emitters for more demanding future applications

Free-standing film based on dissolution and homogeneous compounding of carbon nitride for photocatalytic sterilization

Polymeric carbon nitride (p-CN) has attracted increasing interest as a metal-free photocatalyst in energy conversion and bacterial disinfection. However, due to its particulate and insoluble nature, compounding p-CN at the molecular level into a functional composite of high performance remains a grand challenge. Here, we report the dissolution of p-CN in polyphosphoric acid (PPA) and the homogeneous compounding with carbon nanotubes (CNTs) into a free-standing film simply by co-dissolution, precipitation, and filtration. Interestingly, the as-prepared p-CN-CNTs film exhibited superior film strength than the pristine CNTs and nearly complete inactivation of E. coli and S. aureus under simulated solar irradiation with superoxide radicals as the dominant intermediates. Mechanistic studies indicated that the acidity and viscosity of PPA play crucial roles in the dissolution. The universality of this finding was supported by the further successful discovery of a new type of solvent for p-CN using task-specific ionic liquids. This work would provide a general way to address the dissolution difficulties of p-CN, and pave the prospective application of p-CN in nanocomposites at the molecular level

Multiformity of Photoelectron Storages in Functionalized Carbon Nitrides Enabling Reversible and Adaptable Colorimetric Sensing

Colorimetric sensing has been widely used for centuries across diverse fields, thanks to easy operation with no electricity and uncompromised high sensitivity. However, the limited number of chromogenic systems hampers its broader applications. Here, we reported that carbon nitride (CN), the raw materials-abundant and cheap semiconductors with photoelectron storage capability, can be developed as a new chromogenic platform for colorimetric sensing. Beyond most photoelectron storage materials that only demonstrated blue color in the excited state, CN could also exhibit brown color by terminal group functionalization. The experiments and DFT theoretical calculation revealed the origin of the unusual two types of color switches. Cyano and carbonyl terminal groups in CN elongated the centroids distance of electron/hole and stabilized the excited states through a physical and electrochemical pathway, respectively; meanwhile, the counter cations strengthened these processes. As a result, the CN-derived colorimetric O2 sensors demonstrated excellent reversibility in recycling hundreds of times for detection, and exhibited adaptable limit of detection and linear detection range, which was superior to commercial O2 sensors, especially for complex systems with broad variable concentrations

Graphitic C6N6-supported Dual Cu/Zn Single-Atom Catalyst Mimicking Allosteric Regulation for Intelligent Switching Biosensing

Self-adaptability is highly envisioned for artificial devices such as robots with chemical noses. To this end, seeking catalysts with reversibly switchable functions is promising but generally hampered by mismatched initial valence state of transition metal active centers and electronic structures. Herein, we report a graphitic C6N6-supported dual Cu/Zn single-atom catalyst with a synergistic effect (Cu/Zn-C6N6). It could not only rely on the Cu(I)/Cu(II) redox reaction with promotion from Zn to exhibit a remarkable superoxide dismutase-like (SOD) performance, but also activate Cu(I)/Cu(0) redox reaction to highly switch a marginable peroxidase-like (POD) activity, in which the initial oxidation state was transformed by a photoreduction. The multiformity of the cycles between different valence states for the same catalytic active center makes the reaction activity capable of being reversible switch, the switch efficiency can reach more than 90%. As a proof-of-concept application, Cu/Zn-C6N6 was further confined to a microfluidic chip and applied to a single-interface biosensor with reversibly switched ability in detecting xanthine and glucose in vitro