Carboxylate Oxygen Atoms Research Articles

The negative electrostatic potential of the coordination between calcium and carboxyl/oxygen group in calcium-peptide complexes contributes to calcium utilization

The coordination electrostatic potential has significantly influenced the binding energy of calcium-peptide coordination complexes. However, its impact on calcium bioavailability is unclear. A calcium-binding peptide (CBP) DEDEQIPSHPPR, purified from soybean yogurt was selected. The study selected tetrapeptide residues of acidic amino acids that play an important role in CBP and designed sixteen tetrapeptides rich in carboxyl oxygen atoms to investigate the influence of electrostatic potential on calcium-peptide binding. The results indicated that DEDE exhibited the strongest binding energy (−375.27 kcal/mol) and binding capacity (464.11 ± 2.14 mg/g) with calcium ions compared to other peptides. Moreover, DEDE also increased intracellular calcium concentration the most, being 2.04 times higher than CaCl2. Calcium ions coordinated with carboxyl oxygen atoms possessing negative electrostatic potential, which correlated positively with the bioavailability of calcium ions. This electrostatic potential analysis provides a theoretical basis for developing and screening bioactive peptides with high calcium bioavailability.

A Meso Butterfly-Like Ce(III)-Containing Antimonotungstate with Catalytic Activity for Synthesizing Isoindolinones.

A unique meso Ce(III)-containing antimonotungstate, {Na(OAc)(H2O)2[Ce4(tar)(Htar)2(Sb2W21O72)2(H2O)7]}244- (Ce4tar3; H4tar = tartaric acid), consisting of two enantiomeric parts with a butterfly-like configuration, was successfully synthesized by a one-pot in situ method and characterized. The coordination of d- or l-tar ligands induced the formation of Dawson-like {Ce2Sb2W21} with right or left configurations, thereby determining the d/l configurations of {Na(OAc)(H2O)2[Ce4(tar)(Htar)2(Sb2W21O72)2(H2O)7]}22-. Carboxyl groups link these two enantiomeric parts with Ce(III) ions from each other around the symmetric center of the P1̅ space group. The three types of tar ligands exhibit distinct coordination modes, and all coordinate with at least one W(VI) atom using one carboxylate oxygen atom and one α-OH. Ce4tar3 represents the largest case among those meso-dl-tar-functionalized polyoxometalates. Furthermore, Ce4tar3 exhibits excellent catalytic activity for synthesizing isoindolinones via the three-component reaction of 2-acetylbenzoic acids, amines, and phosphine oxides.

Multifunctional and Ultrastable Co-MOF Effectively Separates Various Different Component Gas Mixtures.

Developing low-cost and multifunctional adsorbents for adsorption separation to obtain high-purity (>99.9%) gases is intriguing yet challenging. Notably, the ongoing trade-off between adsorption capacity and selectivity in separating multicomponent mixed gases still persists as a pressing scientific challenge requiring urgent attention. Herein, the ultrastable TJT-100 exhibits unique structural characteristics including uncoordinated carboxylate oxygen atoms, coordinated water molecules directed toward the pore surface, and sufficient Me2NH2+ cations in channels. TJT-100 exhibits a high adsorption capacity and exceptional separation performance, particularly notable for its high C2H2 capacity of 127.7 cm3/g and remarkable C2H2 selectivity over CO2 (5.4) and CH4 (19.8), which makes it a standout material for various separation applications. In a breakthrough experiment with a C2H2/CO2 mixture (v/v = 50/50), TJT-100 achieved a record-high C2H2 productivity of 69.33 L/kg with a purity of 99.9%. Additionally, TJT-100 demonstrates its effectiveness in separating CO2 from natural gas and flue gas. Its exceptional selectivity for CO2/CH4 (10.7) and CO2/N2 (11.9) results in a high CO2 productivity of 21.23 and 22.93 L/kg with 99.9% purity from CO2/CH4 (v/v = 50/50) and CO2/N2 (v/v = 15/85) mixtures, respectively.

Chitosan encapsulation soy peptide–calcium promotes calcium absorption and bone health of rats fed a low calcium diet

Calcium deficiency is considered widespread globally, and discovering calcium with high bioavailability is one of the keys to solving calcium deficiency. This study prepared a calcium delivery system with chitosan and soy peptide and investigated its characteristics, ability to promote calcium absorption, and effects on bone health. The experiment results reveal that chitosan encapsulates soybean peptide–calcium (COS–SPs–Ca) with carboxyl oxygen atoms, amino nitrogen atoms, and phosphate ions, which has a slow-release effect in simulated gastrointestinal digestion. In calcium-deficient rats, COS–SPs–Ca has beneficial effects on serum biochemical parameters, bone biomechanics, and bone microarchitecture, and significantly up-regulated the gene expression of TRPV5, TRPV6, PepT1, and Calbindin-D9k in the small intestine. These results suggest that COS–SPs–Ca is a promising calcium supplement.

Characterization, in vitro antioxidant activity and stability of cattle bone collagen peptides‑selenium chelate

In this study, cattle bone collagen peptides–selenium chelate (CCP-Se) was prepared and its structure, oxidation resistance and stability were characterized. The selenium binding capacity was 33.65 ± 0.13 mg/g by optimized preparation conditions. Structural analysis showed that selenium ions bound mainly to the amino nitrogen, carboxyl oxygen and hydroxyl oxygen atoms of the cattle bone collagen peptide (CCP). The microstructure and particle size analyses showed that the particle size of CCP-Se was increased and formed a regular and compact crystal structure compared with CCP. Additionally, CCP-Se exhibited excellent antioxidant activity. Stability analysis showed that CCP-Se was stable in thermal processing, simulated in vitro digestion and acid/alkali tolerance tests. The intestinal selenium permeability of CCP-Se was significantly better than sodium selenite (p < 0.05). This study provides reference for the high-value application of cattle bone and suggests the potential of CCP-Se as a new effective selenium supplement.

The analysis of sarcosine phosphate single crystal based on polarized IR and Raman spectra

For the first time, the room temperature polarized IR reflection and Raman spectra of sarcosine phosphate (sar)·H3PO4, in the form of an oriented single crystal have been measured. The polarized spectra are discussed with respect to the crystal structure (X-ray diffraction) data and the literature data on the normal coordinate analysis of the zwitterionic and cationic forms of the sarcosine molecule. Based on the analysis of the spectra and transition dipole moment calculations for each internal mode with respect to the experimental X(a), Y(b) and Z(c) axes, we have been able to determine the directionality and strength of the complicated hydrogen bonds network in the crystal. The A-B-C band structure of the OH stretching vibrations in the strongest hydrogen bonds (HBs) has been assigned. Independent interactions of each HB with light are confirmed based on their polarization properties. The differences within the band of carboxyl group components are ascribed to a rather strong Davydov-type interaction between the carboxyl groups in the title crystal, they may also be caused by participation of the carboxyl-oxygen atom in the medium-strong HB with phosphate-oxygen. These studies are interesting from the point of view of designing strategy for the molecular engineering of new compounds with strong hydrogen bonds, new phase-change materials, as well as crystals with improved optical, magnetic and nonlinear optical properties.

The molecular mechanisms underlying optical isomer arbutin permeating the skin: The molecular interaction between arbutin and skin components

Arbutin, a typical optical isomer, has garnered widespread acclaim in the whitening cosmetics for its favorable efficacy and safety. However, the molecular mechanisms underlying α-arbutin and β-arbutin permeating across the skin have not elucidated clearly yet. Herein we aimed to unveil how α-arbutin and β-arbutin interacted with keratin or SC lipids, further demonstrating their relationship with their drug permeability. We found that α-arbutin displayed significantly higher drug accumulation into the porcine skin than β-arbutin within 24 h through in vitro permeation test. Moreover, α-arbutin predominantly induced the alternations of secondary structure of amide II during the drug permeation, which was favorable for α-arbutin permeation. On the contrary, β-arbutin exhibited an observable effect on the stretching vibration of SC lipids, possessing a significantly stronger mixing energy, binding energy and compatibility with ceramide (Cer) than that of α-arbutin, which ultimately restricted its permeation. Interestingly, free fatty acids and ceramides of the SC lipids specifically utilized its oxygen atom of carboxyl group to dock the arbutin molecules, enhancing their affinity with β-arbutin, as confirmed by molecular simulation and 13Carbon Nuclear Magnetic Resonance. Nevertheless, a favorable compatibility between α-arbutin and keratin was observed. It was emphasized that the distinct spatial configuration and opposite optical rotation of arbutin was the leading factor impacting the intermolecular force between arbutin and the SC, and resulted in a diverse drug permeation. In cellular and in vivo skin pharmacokinetic studies, α-arbutin also possessed a higher cellular uptake and topical bioavailability than β-arbutin. This study revealed the transdermal permeation mechanisms of optical isomer arbutin at the molecular levels, providing methodological reference for the investigations of permeation behaviors of other isomers with similar spatial configuration.

Synthesis, spectral analysis, XRD, molecular docking simulation of dithranol and glycine mixed ligand complexes and their potential role in suppressing breast cancer cells via down‐regulating the expression of protein metalloproteinase‐9

Five novel complexes of nickel (II)(1), zinc (II)(2), zirconium (IV)(3), lanthanum (III)(4), thorium (IV)(5), with the dithranol (Dithr) ligand and glycine (Gly) were synthesized and characterized. Their structures were investigated using elemental analysis, molar conductance (Λ), magnetic studies (μeff), spectroscopic methods (FT‐IR, UV–Vis., 1H NMR, XRD), mass spectrometry, TG/DTG and DTA. Findings revealed that Dithr was chelated via two hydroxyl oxygen atoms and carbonyl group while, Gly chelated through carboxylic oxygen and nitrogen atom. All complexes appeared with molar ratio 1:1:1 (M:Dithr:Gly) and were electrolytes with 1:1 for (1), (2) and (3) complexes, 1:2 for (4) complex, and 1:3 for (5) complex according to elemental analysis and molar conductivity data. All metal‐chelates, except Th (IV)‐complex, were confirmed to have lattice water molecules based on their thermal behavior. Average crystalline size of all compounds was calculated using XRD analysis and found in the range 35.50–55.57 nm, indicating the compounds existed as nanocrystalline structure, except zirconium (IV) complex. Then, we studied cytotoxic effects of our synthetic drugs on the survival of an aggressive‐breast‐cancer‐histotype“66cl‐4.” Given its involvement in cancer‐metastasis, matrix‐metalloproteinase‐(MMP)‐9 protein expression was evaluated using western‐blotting‐assays. Th(IV)‐complex emerged as the most effective option in inhibiting cancer‐cells‐proliferation (IC50: 9.39 μM), and suppressed expression MMP‐9 levels by 86%, at 25 μM dose, and drug‐binding‐affinity was interpreted via molecular modeling.

Isolation, identification, and chelation mechanism of ferrous-chelating peptide from peanut protein hydrolysate.

Peanut peptides can chelate iron but their chelation mechanism remains unclear. The purpose of this study is to separate peanut ferrous-chelating peptides and explore the chelation mechanism of peanut peptides with iron. Peanut peptide component F-122, which had a higher chelation rate, was separated using ultrafiltration, gel filtration chromatography, and ion exchange chromatography, achieving a ferrous chelation rate of 90.7%. Six peptide segments were screened and their amino acid sequences were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Spectral analysis confirmed that the chelation between peanut peptides and ferrous ions occurred and a new substance was formed. Molecular docking simulation indicated that the amino acids in peanut peptides involved in the chelating reaction were glutamic acid, arginine, glycine, threonine, phenylalanine, and lysine. The binding sites included the main chain oxygen atom, side chain oxygen atom, and carboxyl oxygen atom of amino acid. The isolated peanut peptide had a higher ferrous-chelation rate. The chelating mechanism of peanut peptide with ferrous ion was elucidated. This study provides a theoretical basis for the development of new peptide-ferrous preparations. © 2024 Society of Chemical Industry.

Zn2+ chelating peptide GFLGSP: Characterization of structure/Zn2+ chelating mode and the potential mechanisms for promoting Zn2+ transport in Caco-2 cells

This study focused on exploring the Zn2+ chelating peptide GFLGSP: the characterization of structure/Zn2+ chelating mode and the potential mechanisms for promoting Zn2+ transport in Caco-2 cells. The findings revealed the bidentate chelating between Zn2+ and carboxyl oxygen atom in Pro6 residue. Thereafter, the secondary structure of GFLGSP remained unchanged, but there was an increase in zeta potential and particle size. Notably, the GFLGSP-Zn2+ complex enhanced the Zn2+ transport rate and modulated ZIP4 and ZNT1 expression in a Caco-2 cells monolayer model. As revealed by molecular docking analysis, GFLGSP interacted with ZIP4 through intermolecular hydrogen bonds as well as Van der Waals forces. The Zn2+ transport mechanisms of the GFLGSP-Zn2+ complex encompassed ZIP4 (vital channel), endocytosis (primary pathway) and paracellular transport (supplementary pathway). Based on these results, the tilapia skin collagen-derived GFLGSP hold promise as the potential dietary Zn2+ supplement.

Synthesis, characterization, and performance evaluation of AA/AMPS copolymers with different molecular weights and explanation of the inhibition mechanism of calcium carbonate and calcium sulfate

Polymeric scale inhibitors are widely acknowledged for their eco-friendliness, strong compatibility, and versatile nature. However, the impact of molecular weight variation on their inhibitory efficacy remains a relatively understudied aspect. In this investigation, AA/AMPS copolymers with distinct molecular weights (1000, 2000, 3000, 4000, 5000, 6000) were synthesized and probed for their influence on mineral scale inhibition across diverse water quality parameters (e.g., calcium ion concentration, pH) and process conditions (e.g., temperature, duration). Concurrently, the crystalline and morphological alterations of AA/AMPS during mineral scale inhibition were delved. By integrating molecular dynamics simulations and quantum chemical calculations, the effects of varying molecular weights of AA/AMPS on mineral scale inhibition were scrutinized. Moreover, the inhibition mechanism was thoroughly explored. Our findings revealed that AA/AMPS with molecular weights of 2000 and 3000 exhibited superior inhibition efficacy against calcium carbonate and calcium sulfate. This phenomenon was attributed to the movement velocity and binding energy of AA/AMPS with corresponding molecular weights towards the primary crystal growth surface. Additionally, the carboxyl oxygen atoms on the polymers facilitated chelation with calcium ions, thereby impeding further crystal formation and growth. Consequently, achieving heightened efficiency in scale inhibition.

Spectral, XRD, morphological, DFT, and molecular modeling investigations of newly prepared isatin Schiff base complexes

The new Schiff base ligand was designed from a condensation reaction of isatin with 5‐amino‐2‐hydroxy benzoic acid. Then, the metal complexes were prepared. The structures of the prepared compounds were framed from thermogravimetric analyses (TG–DTG), mass spectrometry, elemental analyses, 1H‐NMR, IR, electronic spectra, UV–vis, and conductivity measurements. Surface and size morphology have been studied by X‐ray powder diffraction and scanning electron microscope (SEM) analysis. The IR spectra suggested that the ligand acted as bidentate coordinated with metal ions through deprotonated carboxylate oxygen atom and oxygen of phenolic group. With the exception of the complexes of Cr (III), Fe (III), and Cd (II), which were non‐electrolytes, the molar conductivities demonstrated the electrolytic behavior of all the rest complexes. The X‐ray diffraction (XRD) analysis patterns for the Schiff base complexes indicated their crystalline nature except the Co (II) complex which had amorphous structure. The ligand and its metal complexes were screened for their antimicrobial activities against two G‐positive, two G‐negative bacteria and against Aspergillus fumigatus and Candida albicans fungi. Additionally, the compounds were evaluated against the MFC‐7 breast cancer cell line for their anticancer activity. The outcomes demonstrated their strong antitumor activity. [Fe(HL)Cl2(H2O)2]0.5H2O complex has the lowest IC50 value = 9 μg mL−1. Molecular modeling studies for the ligand and its Co (II) and Fe (III) complexes were accomplished from density functional theory (DFT) analysis. From molecular docking study, the electrophilic moieties in both complexes displayed good binding interactions with the CDK6, aminoglycoside phosphotransferase, and CYP51 targeted proteins.

Mechanistic deduction of gallium(III) extraction using halogenated secondary amides: Spectroscopic interpretation

Secondary amides act as bifunctional compounds to extract metal anionic species due to the presence of N–H hydrogen and protonated carbonyl oxygen atoms. To exclude the latter function with stronger interaction and less extraction selectivity for metal anionic species, two secondary amide compounds with halogen atoms, namely N-(2-ethylhexyl)-2,2,2-trichloroacetamide as TCAA and N-(2-ethylhexyl)-2,2,2-tribromoacetamide as TBAA, have been synthesised to investigate the efficiency and mechanism of Ga(III) extraction for comparison with N-(2-ethylhexyl)-2,2,2-trifluoroacetamide (TFAA). The 1H NMR spectroscopy results indicated the absence of proton extraction from the carboxylic oxygen atoms of both halogen-containing amides at sufficiently high concentrations of HCl. The three amides exhibited preferential extraction of Ga(III) compared to other metals in highly acidic media. A slope analysis was conducted to assess the stoichiometry for the extraction of Ga(III). The FT-IR and 1H NMR spectroscopies were employed to elucidate the extraction mechanism of GaCl4– using TCAA and TBAA. Therefore, the hydrogen atoms of the N–H group of both amides, with extremely weak δ+ nature, exhibited a distinct extractive preference for anionic GaCl4–. Following the forward extraction, Ga(III) was effectively separated from the organic phase through stripping with distilled water. The extraction efficiencies of GaCl4– among the three amides are not followed by the strength of electron-withdrawing nature of halogen atoms, but the strength of intra- or intermolecular interactions of the amides. This argument was substantiated by calculations using density functional theory (DFT).

Gallium(III) complexes with 1,3-pdta-type of ligands: The influence of an alkyl substituent in 1,3-propanediamine chain and the metal counter cation on the structural properties of the complex

The hexadentate 1,3-propanediamine-N,N,N’,N’-tetraacetate (1,3-pdta4−) and (±)-1,3-pentanediamine-N,N,N’,N’-tetraacetate (1,3-pndta4−) ligands were used for the synthesis of two new gallium(III) complexes, Na[Ga(1,3-pdta)]·3H2O (1) and Ba[Ga(1,3-pndta)]2·3H2O (2). Complexes 1 and 2 were characterized by IR and NMR (1H and 13C) spectroscopy and single crystal X-ray diffraction analysis. The obtained results have shown that both hexadentate 1,3-pdta4− and 1,3-pndta4− ligands are coordinated to gallium(III) ion through the two nitrogen and four carboxylate oxygen atoms. Both complexes show significant octahedral distortion since the mean angular deviation is nearly four degrees per angle. However, the octahedral distortion of complex 2 is lower than of 1, as indicated by the ΣΔ(Oh) values (48° and 49° versus 53°, respectively). The binding interactions of the complexes 1 and 2 with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) were studied by fluorescence emission spectroscopy. Both complexes can bind to the serum albumin reversibly, while their affinity to ct-DNA is rather low.

1H/17O Chemical Shift Waves in Carboxyl-Bridged Hydrogen Bond Networks in Organic Solids.

We report solid-state 1H and 17O NMR results for four 17O-labeled organic compounds each containing an extensive carboxyl-bridged hydrogen bond (CBHB) network in the crystal lattice: tetrabutylammonium hydrogen di-[17O2]salicylate (1), [17O4]quinolinic acid (2), [17O4]dinicotinic acid (3), and [17O2]Gly/[17O2]Gly·HCl cocrystal (4). The 1H isotropic chemical shifts found for protons involved in different CBHB networks are between 8.2 and 20.5 ppm, which reflect very different hydrogen-bonding environments. Similarly, the 17O isotropic chemical shifts found for the carboxylate oxygen atoms in CBHB networks, spanning a large range between 166 and 341 ppm, are also remarkably sensitive to the hydrogen-bonding environments. We introduced a simple graphical representation in which 1H and 17O chemical shifts are displayed along the H and O atomic chains that form the CBHB network. In such a depiction, because wavy patterns are often observed, we refer to these wavy patterns as 1H/17O chemical shift waves. Typical patterns of 1H/17O chemical shift waves in CBHB networks are discussed. The reported 1H and 17O NMR parameters for the CBHB network models examined in this study can serve as benchmarks to aid in spectral interpretation for CBHB networks in proteins.

Efficient regulation of cadmium accumulation by carboxymethylammonium chloride in rice: Correlation analysis and expression of transporter gene OsGLR3

The mechanism of carboxymethylammonium chloride (CC) regulating cadmium (Cd) accumulation in rice was studied in field and hydroponic experiments. Field experiments showed that 0.2–1.2 mmol L−1 CC spraying effectively reduced Cd accumulation by 44 %–77 % in early rice grains and 39 %–78 % in late rice grains, significantly increased calcium (Ca) content and amino acids content in grains, as well as alleviated Cd-induced oxidative damage in leaves. Hydroponic experiments further verified the inhibition effect of CC on Cd accumulation. 1.2 mmol L−1 CC made the highest decrease of Cd content in shoots and roots of hydroponic seedlings by 45 % and 53 %, respectively. Exogenous CC significantly increased glutamate (Glu), glycine (Gly) and glutathione (GSH) content, and improved the activities of catalase (CAT) and superoxide dismutase (SOD) by 41–131 % and 11–121 % in shoots of hydroponic seedlings, respectively. Exogenous CC also increased the relative expression of OsGLR3.1–3.5 in the shoots and roots of hydroponic seedlings. The quantum computational chemistry was used to clarify that the Gly radical provided by CC could form various complexes with Cd through carboxyl oxygen atoms. These results showed that exogenous application of CC improved the tolerance to Cd by enhancing the antioxidant capacity; inhibited the absorption, transport and accumulation of Cd in rice by (1) promoting chelation, (2) increasing the GLRs activity through upregulating the content of Glu, Gly, as well as the expression of OsGLR3.1–3.5.

Lactobacillus helveticus-Derived Whey-Calcium Chelate Promotes Calcium Absorption and Bone Health of Rats Fed a Low-Calcium Diet.

This study investigated the characteristics of Lactobacillus helveticus-derived whey-calcium chelate (LHWCC) and its effect on the calcium absorption and bone health of rats. Fourier-transform infrared spectroscopy showed that carboxyl oxygen atoms, amino nitrogen atoms, and phosphate ions were the major binding sites with calcium in LHWCC, which has a sustained release effect in simulated in vitro digestion. LHWCC had beneficial effects on serum biochemical parameters, bone biomechanics, and the morphological indexes of the bones of calcium-deficient rats when fed at a dose of 40 mg Ca/kg BW for 7 weeks. In contrast to the inorganic calcium supplement, LHWCC significantly upregulated the gene expression of transient receptor potential cation V5 (TRPV5), TRPV6, PepT1, calcium-binding protein-D9k (Calbindin-D9k), and a calcium pump (plasma membrane Ca-ATPase, PMCA1b), leading to promotion of the calcium absorption rate, whereas Ca3(PO4)2 only upregulated the TRPV6 channel in vivo. These findings illustrate the potential of LHWCC as an organic calcium supplement.

Unveiling the organic acids with auxiliary functional groups effect on α‐hemihydrate gypsum: Ab initio calculations

AbstractRegulating the crystal morphology of low aspect ratio, short columnar α‐hemihydrate gypsum (α‐HH) is crucial due to its distinctive physical and chemical properties, which make it widely applicable. In this work, succinic acid, malic acid, and maleic acid were selected as the research objects, among which the number and spacing of carboxyl groups were the same, while the auxiliary functional groups were different. The adsorption energy, Mulliken charge population, electronic state density, and charge density difference of the three organic acids on the surfaces of α‐HH were calculated by well‐defined ab initio calculations. The results showed that the synergistic effect of ‐COOH groups is necessary for the effective crystallization of α‐HH. Organic acids interact with the Ca atoms on the crystal surface, as evidenced by their preferential adsorption on the top surface of α‐HH crystals (002). This interaction occurs through a double‐dentate chelation between the carboxyl oxygen atoms at both ends of the organic acid and the Ca atoms on the crystal surface, resulting in the formation of a six‐membered cyclic organic acid calcium complex. This complex hinders ion diffusion and the stacking of crystal surfaces, leading to a decrease in the growth rate along the c‐axis and promoting more extensive crystal development and larger crystal sizes. The work provides insight into the preparation of short prismatic α‐HH using organic acid crystallizing agents.

Glycated Walnut Meal Peptide-Calcium Chelates: Preparation, Characterization, and Stability.

Finding stable and bioavailable calcium supplements is crucial for addressing calcium deficiency. In this study, glycated peptide-calcium chelates (WMPHs-COS-Ca) were prepared from walnut meal protein hydrolysates (WMPHs) and chitosan oligosaccharides (COSs) through the Maillard reaction, and the structural properties and stability of the WMPHs-COS-Ca were characterized. The results showed that WMPHs and COSs exhibited high binding affinities, with a glycation degree of 64.82%. After glycation, Asp, Lys, and Arg decreased by 2.07%, 0.46%, and 1.06%, respectively, which indicated that these three amino acids are involved in the Maillard reaction. In addition, compared with the WMPHs, the emulsifying ability and emulsion stability of the WMPHs-COS increased by 10.16 mg2/g and 52.73 min, respectively, suggesting that WMPHs-COS have better processing characteristics. After chelation with calcium ions, the calcium chelation rate of peptides with molecular weights less than 1 kDa was the highest (64.88%), and the optimized preparation conditions were 5:1 w/w for WMPH-COS/CaCl2s, with a temperature of 50 °C, a chelation time of 50 min, and a pH of 7.0. Scanning electron microscopy showed that the "bridging role" of WMPHs-COS changed to a loose structure. UV-vis spectroscopy and Fourier transform infrared spectrometry results indicated that the amino nitrogen atoms, carboxyl oxygen atoms, and carbon oxygen atoms in WMPHs-COS chelated with calcium ions, forming WMPHs-COS-Ca. Moreover, WMPHs-COS-Ca was relatively stable at high temperatures and under acidic and alkaline environmental and digestion conditions in the gastrointestinal tract, indicating that WMPHs-COS-Ca have a greater degree of bioavailability.

Room‐Temperature Phosphorescence Hydrogel with Multiple Color Based on Salt‐Induced Aggregation

AbstractOrganic photoluminescent materials with room‐temperature phosphorescence (RTP) are of great interest, yet achieving RTP in hydrogels faces challenges due to water‐quenching effects. In this study, a straightforward method is presented to achieve RTP hydrogel using a self‐healing and salt‐hardening hydrogel. The hydrogel is synthesized by polymerizing acrylic acid (AA) with diethylenetriamine (DETA) as the dynamic crosslinker. The poly(acrylic acid)/DETA hydrogel could achieve an afterglow lasting 1.6 s after soaking with NaBr solution. The salt‐enhanced hydrophobic aggregation of the hydrogel network promotes the clustering of carboxyl groups and oxygen atoms, resulting in a rigid environment that suppresses nonradioactive transitions and leads to the manifestation of RTP. Additionally, the dynamic association of AA‐DETA allows the freeze‐dried hydrogel powder to be blended with various hydrophobic dyes, leading to a remodelable hydrogel with delayed emission of multiple colors. In general, by combining salt‐hardening property with self‐healing property together, a RTP hydrogel platform that can be facilely loaded with various organic dyes is proposed.