Non-adiabatic conformation distortion charge transfer enables dual emission of thermally activated delayed fluorescence and room temperature phosphorescence.

In this work, we report for the first time that thiophenol-substituted naphthalimide can achieve thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) simultaneously through non-conjugated flexible connection. Herein, we explain that the enhancement of intersystem crossing (ISC) between the singlet excited state and triplet excited states in NISPh is mainly caused by the non-adiabatic conformation distortion charge transfer (CDCT) of the excited states. More precisely, CDCT results in the conformation matching and energy barrier decrease between the excited states. In addition, the electronic and vibration coupling is further enhanced in NISPh. Our work substantiates a rational design strategy for the development of simple purely organic materials to achieve dual emission of TADF and RTP.

Aqueous-phase dual-functional chiral perovskites for hydrogen sulfide (H2S) detection and antibacterial applications in Escherichia coli.

Perovskite nanocrystals (PNCs) have attracted extensive attention for their potential applications in biology. However, only a handful of PNCs have been scrutinized in the biological domain due to issues such as instability, poor dispersion, and size inhomogeneity in polar solvents. The development of dual-functional perovskite nanomaterials with hydrogen sulfide (H2S) sensing and antibacterial capabilities is particularly intriguing. In this study, we prepared chiral quasi-two-dimensional (quasi-2D) perovskite nanomaterials, Bio(S-PEA)2CsPb2Br7 and Bio(R-PEA)2CsPb2Br7, that were uniformly dispersed in aqueous media. The effective encapsulation of methoxypolyethylene glycol amine (mPEG-NH2) improved water stability and uniformity of particle size. Circular dichroism (CD) signals were created by the successful insertion of chiral cations. These perovskites as probes showed a rapid and sensitive fluorescence quenching response to H2S, and the effect of imaging detection was observed at the Escherichia coli (E. coli) level. As antibacterial agents, their pronounced positive charge properties facilitated membrane lysis and subsequent E. coli death, indicating a significant antibacterial effect. This work has preliminary explored the application of chiral perovskites in biology and provides insight into the development of bifunctional perovskite nanomaterials for biological applications.

Thinned young apple powder prevents obesity-induced neuronal apoptosis via improving mitochondrial function of cerebral cortex in mice.

Mitochondrial dysfunction is one of the triggers for obesity-induced neuron apoptosis. Thinned young apple is getting more attention on account of the extensive biological activities because of rich polyphenols and polysaccharides. However, the neuroprotective effect of thinned young apple powder (YAP) is still unclear. The aim of the present study was to investigate the preventive effect of YAP on obesity-induced neuronal apoptosis. C57BL/6J male mice were divided into 5 groups, control (CON), high fat diet (HFD), HFD + orlistat (ORL), HFD + low-dose young apple powder (LYAP) and HFD + high-dose young apple powder (HYAP) groups and intervened for 12 weeks. It was found that the YAP effectively reduced body weight gain. Importantly, the levels of pro-apoptosis protein were lower in LYAP and HYAP groups than the HFD group, such as Bak/Bcl2 and cleaved caspase3/caspase3. Pathway analysis based on untargeted metabolomics suggested that YAP alleviated obesity-induced neuronal apoptosis by three main metabolic pathway including arginine metabolism, citrate cycle (TCA cycle) and glutathione metabolism. Meanwhile, YAP improved the protein expression of mitochondrial respiratory chain complex, maintained the homeostasis of TCA cycle intermediates, protected the balance of mitochondrial dynamics and alleviated lipid accumulation. In addition, the levels of several antioxidants in cerebral cortex were higher in HYAP group than the HFD group like superoxide dismutase (SOD) and catalase (CAT). In summary, YAP supplementation suppressed neuronal apoptosis in the cerebral cortex of HFD-induced obesity mice by improving mitochondrial function and inhibiting oxidative stress.

Strong gelation capacity of a pectin-like polysaccharide in the presence of K+ ion.

In the present study, a pectin-like apple polysaccharide (AP) obtained by metal precipitation technique was demonstrated to show strong gelling capacity in the presence of K+ ion upon cooling. Increasing amount of K+ addition monotonically promoted the gelation of AP, as characterized by the increased gelation temperature (Tgel), gel melting temperature (Tmelt) and the gel strength. Compared with K+ ion, Na+ was unable to induce AP gelation even at high ionic concentrations, but other monovalent cations (Rb+, Cs+) can induce the gelation as in the case of K+ addition. At room temperature, the minimum cationic concentration as required to induce AP gelation followed the order of K+ ≈ Cr+ (8 mM) > Rb+ (3.5 mM), indicating that cationic radius (Na+ < K+ < Rb+ < Cs+) played a dominant role in inducing AP gelation, but other factors may also be involved. Finally, the gelation behavior of AP in the presence of K+ was explained as the suppressed intermolecular electrostatic repulsion between AP chains due to the strong electrostatic shielding effect of K+, which led to the formation of a gel network mediated by intermolecular hydrogen bonding. This reported gelation property may allow AP to find application as a new gelling polysaccharide.

Discovery of novel cMET-targeting antibody Fab drug conjugates as potential treatment for solid tumors with highly expressed cMET.

BACKGROUND: Solid tumors are becoming prevalent affecting both old and young populations. Numerous solid tumors are associated with high cMET expression. The complexity of solid tumors combined with the highly interconnected nature of the cMET/HGF pathway with other cellular pathways make the pursuit of finding an effective treatment extremely challenging. The current standard of care for these malignancies is mostly small molecule-based chemotherapy. Antibody-based therapeutics as well as antibody drug conjugates are promising emerging classes against cMET-overexpressing solid tumors. RESEARCH DESIGN AND METHODS: In this study, we described the design, synthesis, in vitro and in vivo characterization of cMET-targeting Fab drug conjugates (FDCs) as an alternative therapeutic strategy. The format is comprised of a Fab conjugated to a potent cytotoxic drug via a cleavable linker employing lysine-based and cysteine-based conjugation chemistries. RESULTS: We found that the FDCs have potent anti-tumor efficacies in cancer cells with elevated overexpression of cMET. Moreover, they demonstrated a remarkable anti-tumor effect in a human gastric xenograft mouse model. CONCLUSIONS: The FDC format has the potential to overcome some of the challenges presented by the other classes of therapeutics. This study highlights the promise of antibody fragment-based drug conjugate formats for the treatment of solid tumors.

Exploring the Biomedical Applications of Biosynthesized Silver Nanoparticles Using Perilla frutescens Flavonoid Extract: Antibacterial, Antioxidant, and Cell Toxicity Properties against Colon Cancer Cells.

The present study reports the biomimetic synthesis of silver nanoparticles (AgNPs) using a simple, cost effective and eco-friendly method. In this method, the flavonoid extract of Perilla frutescens (PFFE) was used as a bioreduction agent for the reduction of metallic silver into nanosilver, called P. frutescens flavonoid extract silver nanoparticles (PFFE-AgNPs). The Ultraviolet-Visible (UV-Vis) spectrum showed a characteristic absorption peak at 440 nm that confirmed the synthesis of PFFE-AgNPs. A Fourier transform infrared spectroscopic (FTIR) analysis of the PFFE-AgNPs revealed that flavonoids are involved in the bioreduction and capping processes. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns confirmed the face-centered cubic (FCC) crystal structure of PFFE-AgNPs. A transmission electron microscopic (TEM) analysis indicated that the synthesized PFFE-AgNPs are 20 to 70 nm in size with spherical morphology and without any aggregation. Dynamic light scattering (DLS) studies showed that the average hydrodynamic size was 44 nm. A polydispersity index (PDI) of 0.321 denotes the monodispersed nature of PFFE-AgNPs. Further, a highly negative surface charge or zeta potential value (-30 mV) indicates the repulsion, non-aggregation, and stability of PFFE-AgNPs. PFFE-AgNPs showed cytotoxic effects against cancer cell lines, including human colon carcinoma (COLO205) and mouse melanoma (B16F10), with IC50 concentrations of 59.57 and 69.33 µg/mL, respectively. PFFE-AgNPs showed a significant inhibition of both Gram-positive (Listeria monocytogens and Enterococcus faecalis) and Gram-negative (Salmonella typhi and Acinetobacter baumannii) bacteria pathogens. PFFE-AgNPs exhibited in vitro antioxidant activity by quenching 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2) free radicals with IC50 values of 72.81 and 92.48 µg/mL, respectively. In this study, we also explained the plausible mechanisms of the biosynthesis, anticancer, and antibacterial effects of PFFE-AgNPs. Overall, these findings suggest that PFFE-AgNPs have potential as a multi-functional nanomaterial for biomedical applications, particularly in cancer therapy and infection control. However, it is important to note that further research is needed to determine the safety and efficacy of these nanoparticles in vivo, as well as to explore their potential in other areas of medicine.

Room-temperature efficient photoluminescence mechanism of indium doping lead-free colloidal MA3Bi2Br9 quantum dots solution.

Lead halide perovskite quantum dots (QDs) are promising candidates for future optoelectronic devices due to their excellent photonic and electronic properties. However, poor stability and toxicity problems limit their further development. This work demonstrates the doping tactics to boost the optical properties of lead-free colloidal MA3Bi2Br9 QDs, the indium ion (In3+) doping presented herein is found to be effective in improving the photoluminescence (PL) properties of MA3Bi2Br9 (CH3NH2 = MA) QDs without alerting their favorable electronic structure. It has been elucidated by microscopy and diffraction results that the In3+ doping optimizes the QDs solution octahedron structure, and the PL red-shifted phenomenon coincides well with the analogous red-shifted obtained in the ultraviolet/visible (UV-Vis) absorption spectroscopy, which is due to the quantum confinement effect. And the nanosecond transient absorption (ns-TA) spectroscopy elucidates that the enhanced radiative recombination process contributes to enhanced stability and luminescence. The photoluminescence quantum yield (PLQY) of MA3Bi2Br9 QDs is increased by 60.7%. This work offers a valid strategy for improving the quality of the lead-free perovskite QDs.

Gelation behaviors and mechanism of a new pectic polysaccharide from apple pomace as a potential gelatin substitute.

In this study, we reported a pectic polysaccharide industrially obtained from apple pomace by metal ion precipitation technique showing an unexpected gelation behavior. Structurally, this apple pectin (AP) is a macromolecular polymer with a weight-average molecular weight (Mw) of 361.7 kDa, and DM (degree of methoxylation) of 12.5 %, comprising 60.38 % glucose, 19.41 % mannose, 17.60 % galactose and 1.00 % rhamnose and 1.61 % glucuronic acid. The low acidic sugar percentage relative to the total monosaccharide amount indicated a high branching structure of AP. On addition of Ca2+ ions, AP exhibited a remarkable gelling ability upon cooling its heat solution to low temperature (e.g., 4 °C). However, at room temperature (e.g., 25 °C) or in the absence of Ca2+, no gel was formed. At a fixed pectin concentration (0.5 %, w/v), AP showed increasing gel hardness and gelation temperature (Tgel) with CaCl2 concentration increasing to 0.05 % (w/v); however, further addition of CaCl2 weakened AP gels and even abolished the gelation. On reheating, all gels melted below 35 °C, which suggests the potential use of AP as a gelatin substitute. The gelation mechanism was explained as an intricate balance of the synchronous formation of hydrogen bond and Ca2+ crosslinks between AP molecules during cooling.

Ultrafast non-adiabatic dynamics of stilbene-based plant-derived sunscreens with cis-trans isomerization structures.

In this work, we investigated the potential UV protection mechanism of the natural compounds hydroxy resveratrol and pterostilbene by combining theoretical calculations and femtosecond transient absorption spectra (FTAS). The UV absorption spectra showed that the two compounds exhibited strong absorption properties and high photostability. We found two molecules will reach the S1 state or an even higher excited state after UV exposure and molecules in S1 will cross a lower energy barrier to reach the conical intersection. The adiabatic trans-cis isomerization process happened and finally return to the ground. Meanwhile, FTAS clarified the time scale of trans-cis isomerization of two molecules was âˆ¼ 10 ps, which also met the requirement of fast energy relaxation. This work also provides theoretical guidance for developing new sunscreen molecules from natural stilbene.

SiMYBS3, Encoding a Setaria italica Heterosis-Related MYB Transcription Factor, Confers Drought Tolerance in Arabidopsis.

Drought is a major limiting factor affecting grain production. Drought-tolerant crop varieties are required to ensure future grain production. Here, 5597 DEGs were identified using transcriptome data before and after drought stress in foxtail millet (Setaria italica) hybrid Zhangza 19 and its parents. A total of 607 drought-tolerant genes were screened through WGCNA, and 286 heterotic genes were screened according to the expression level. Among them, 18 genes overlapped. One gene, Seita.9G321800, encoded MYBS3 transcription factor and showed upregulated expression after drought stress. It is highly homologous with MYBS3 in maize, rice, and sorghum and was named SiMYBS3. Subcellular localization analysis showed that the SiMYBS3 protein was located in the nucleus and cytoplasm, and transactivation assay showed SiMYBS3 had transcriptional activation activity in yeast cells. Overexpression of SiMYBS3 in Arabidopsis thaliana conferred drought tolerance, insensitivity to ABA, and earlier flowering. Our results demonstrate that SiMYBS3 is a drought-related heterotic gene and it can be used for enhancing drought resistance in agricultural crop breeding.

Physicochemical and functional properties of RG-I enriched pectin extracted from thinned-young apples.

The demand for obtaining pectin from new sources has been continuously increasing. The abundant but underutilized thinned-young apple is a potential source of pectin. In this study, an organic acid (i.e., citric acid) and two inorganic acids (i.e., hydrochloric acid and nitric acid) commonly used in commercial pectin production were applied to extract pectin from three varieties of thinned-young apples. The physicochemical and functional properties of the thinned-young apple pectin were comprehensively characterized. The highest pectin yield (8.88 %) was obtained from Fuji apple using citric acid extraction. All pectin was high methoxy pectin (HMP) and rich in RG-I regions (>56 %). The citric acid extracted pectin had the highest molecular weight (Mw) and lowest degree of esterification (DE) values, and exhibited great thermal stability and shear-thinning property. Furthermore, Fuji-apple pectin possessed significantly better emulsifying properties compared to pectin obtained from the other two varieties of apples. Thus, pectin extracted with citric acid from Fuji thinned-young apples has great potential to be applied in the food industry as a natural thickener and emulsifier.

Visualization of the Lenticulostriate artery with 3-dimensional time-of-flight magnetic resonance angiography combined with the compressed sensing technique using a 3-T magnetic resonance imaging system.

The lenticulostriate artery (LSA) is a vital perforating cerebral artery, whose occlusion often leads to lacunar infarction. Currently, digital subtraction angiography is mainly used to visualize the LSA in the clinical setting; however, its invasiveness is an important limiting factor. Studies have shown that time-of-flight (TOF) sequencing using a high-field magnetic resonance system (7 T) can better image the LSA. However, the diameter of the LSA is extremely small (approximately 0.3-0.7 mm) with relatively slow blood flow velocity; therefore, imaging the LSA with a 3-T magnetic resonance imaging (MRI) scanner remains challenging. This study aimed to visualize the LSA using 3-dimensional-TOF magnetic resonance angiography (MRA) with compressed sensing using a 3-T system and compare the length and number of the LSAs between patients with infarction and normal controls. The scan times of 3D-TOF MRA with and without compressed sensing were 7 min, and 8 min 44 s, respectively. VR displayed the LSA clearly under both conditions. The total number (p > 0.05) and length (p > 0.05) of the LSAs did not differ significantly between 3D-TOF MRA with and without compressed sensing. However, the total length and number of visualized LSAs was significantly lower (p < 0.05) in the infarction group compared to the control group for both TOF MRA and TOF MRA with compressed sensing. TOF MRA combined with compressed sensing is clinically valuable for analyzing the morphological characteristics of the LSA, and shortens the imaging time to 7 min. This combined technique can meet the requirements of shorter scanning times in clinical settings.

Dendrobium officinale polysaccharide prevents neuronal apoptosis via TET2-dependent DNA demethylation in high-fat diet-induced diabetic mice.

Dendrobium officinale polysaccharide (DP) has the potential function to prevent diabetes-induced neuronal apoptosis, whereas the mechanism is not completely clear. Ten eleven translocation dioxygenase 2 (TET2) is one of the most important therapeutic target for repairing neuronal damage in diabetic mice. The aim of the present study was to investigate whether DP could prevent neuronal apoptosis by regulating TET2 in the brain of HFD-induced diabetic mice. C57BL/6J mice were randomly divided into four groups (n = 12), control group (CON), high-fat diet group (HFD, negative control), metformin group (MET, positive control), and DP group (DP). Compared with HFD group, the neuronal apoptosis of brain was significantly lower in the DP group. The levels of TET2 protein, 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC) were significantly lower in the HFD group than in both the DP and CON groups in the cerebral cortex of mice. The ratio of p-AMPK/AMPK and α-KG/(fumaric acid + succinic acid) were significantly lower in the HFD group than in the other groups. The present study suggests that DP has a preventive effect on diabetes-induced neuronal apoptosis by regulating TET2 function through improving phosphorylate AMPK and mitochondrial function, thus remodeling DNA epigenetics profile of mice brain.

A highly selective red-emitting fluorescent probe and its micro-nano-assembly for imaging endogenous peroxynitrite (ONOO-) in living cells.

Endogenous peroxynitrite plays a very important role in the regulation of life activities. However, validated tools for ONOO- tests are currently insufficient. We designed a fluorescent probe TPA-F-NO2 with a low fluorescence background in water based on the D-π-A structure for the imaging of endogenous ONOO- in living cells. TPA-F-NO2 can realize the naked eye detection of ONOO- due to the obvious color change. TPA-F-NO2 has the advantages of large stokes shift, high signal-to-noise ratio, high selectivity and sensitivity. The quantitative detection can be achieved in the range of 0-14 µM ONOO-. Due to its solvatochromic characteristics, TPA-F-NO2 has the potential to be used in OLEDs and other fields. In addition, 4-methylumbelliferone has a wide range of anticancer effects as an inhibitor of hyaluronic acid. We prepared TPA-MU-NPs by assembling TPA-F-NO2 and 4-methylumbelliferone. It also endows TPA-MU-NPs with ONOO- imaging function and anti-proliferation effect on breast cancer cells and other cells. This 'probe-drug' assembly strategy provides ideas for the design and optimization of dual-functional probes.

Learning Calibrated Class Centers for Few-Shot Classification by Pair-Wise Similarity.

Metric-based methods achieve promising performance on few-shot classification by learning clusters on support samples and generating shared decision boundaries for query samples. However, existing methods ignore the inaccurate class center approximation introduced by the limited number of support samples, which consequently leads to biased inference. Therefore, in this paper, we propose to reduce the approximation error by class center calibration. Specifically, we introduce the so-called Pair-wise Similarity Module (PSM) to generate calibrated class centers adapted to the query sample by capturing the semantic correlations between the support and the query samples, as well as enhancing the discriminative regions on support representation. It is worth noting that the proposed PSM is a simple plug-and-play module and can be inserted into most metric-based few-shot learning models. Through extensive experiments in metric-based models, we demonstrate that the module significantly improves the performance of conventional few-shot classification methods on four few-shot image classification benchmark datasets. Codes are available at: https://github.com/PRIS-CV/Pair-wise-Similarity-module.

Auto-fluorescence of cellulose paper with spatial solid phrase dispersion-induced fluorescence enhancement behavior for three heavy metal ions detection.

Auto-fluorescence of cellulose paper is often considered as an interfering fluorescence, which directly impedes the cellulose paper as a substrate material. This paper creatively explored the composition and properties of auto-fluorescence, and lignosulfonate was primarily speculated as the main source of auto-fluorescence. Surprisingly, its spatial solid phrase dispersion-induced fluorescence enhancement behavior was found. Then, cellulose paper was modified with Mn-doped ZnS quantum dots, and the prepared ratiometric fluorescent paper chip has good performances on morphology, stability, and fluorescence properties. Besides, the paper chip exhibited different fluorescence responses to three heavy metal ions in water sample. The limit of detection for Cd2+, Hg2+ and Pb2+ reached 1.61 nM, 0.01 nM, and 0.02 nM, respectively. In short, the molecular simulation results theoretically proved that heavy metal ions owned substitution affinity with lignosulfonate. Ultimately, this study was the first attempt to utilize paper-based auto-fluorescence, which could better accelerate the development of paper-based chips.

Punicalagin Attenuates Neuronal Apoptosis by Upregulating 5-Hydroxymethylcytosine in the Diabetic Mouse Brain.

Punicalagin exerts neuroprotective activity by improving AMP-activated kinase (AMPK) and mitochondrial Krebs cycle. AMPK and Krebs cycle metabolites regulate 5-hydroxymethylcytosine (5hmC) via acting on ten-eleven translocation (TET) enzymes. Therefore, we hypothesized that punicalagin inhibits diabetes-related neuronal apoptosis by upregulating 5hmC in the diabetic mouse brain. C57BL/6J mice aged 8 weeks were randomly separated into five groups (n = 10), normal control (NC), diabetes mellitus (DM), resveratrol (RES), low-dose punicalagin (LPU), and high-dose punicalagin (HPU). Compared with other groups, the neuronal apoptosis rate was significantly higher and the 5hmC level of the cerebral cortex was significantly lower in the DM group. The levels of TET2 and P-AMPKα/AMPKα were significantly lower in the DM group than in both LPU and HPU groups. The ratio of (succinic acid + fumaric acid)/α-ketoglutarate was significantly higher in the DM group than in other groups. The present results suggest that punicalagin upregulates 5hmC via activating AMPK and maintaining Krebs cycle homeostasis, thus inhibiting neuronal apoptosis in the diabetic mouse brain.

The Impacts of Early-life Adversity on Striatal and Hippocampal Memory Functions.

The impacts of early-life adversity (ELA) on cognitive functions including striatal-dependent habit memory and hippocampal-dependent spatial memory were investigated in male mice. The ELA mouse model was generated via an altered cage environment with limited nesting and bedding materials during postnatal days 2-9 (P2-9). The altered cage environment affected the nesting behaviors of dams, creating a stressful condition for their offspring. The ELA mice had biased decision making and poor spatial memory when they grew into young adults (4-month-old). To explore the underlying synaptic basis of these effects, excitatory synapses represented by postsynaptic density protein-95 (PSD-95) were immunolabelled on a series of brain sections and stereologically quantified in the dorsomedial striatum (DMS) and dorsolateral striatum (DLS), as well as in area CA1 of the dorsal hippocampus. Increased PSD-95-immunoreactive synapses were observed in DLS but not DMS, whereas selective loss of PSD-95 synapses was detected in the stratum radiatum of area CA1. The spine data supported the selective effects of ELA on PSD-95 synapses. Specifically, both thin and mushroom-type spines were increased in DLS, while loss of thin spines was apparent in CA1 radiatum in ELA mice versus controls. The correlation between PSD-95 synapses and memory performances was further analyzed, and the data suggested that increased small (<0.20 µm3) and large (>0.40 µm3) synapses in DLS might drive ELA mice to make decisions largely relying on habit memory, while loss of small synapses in hippocampal CA1 damage the spatial memory of ELA mice.

Enhanced bioavailability and anti-hyperglycemic activity of young apple polyphenols by complexation with whey protein isolates.

This study aims to evaluate the effects of complexation of whey protein isolate (WPI) and young apple polyphenols (YAP) on the bioavailability and anti-hyperglycemic activity of YAP. Two types of WPI-YAP complexes were fabricated by mixing WPI with YAP at 25℃ (WPI-YAP) and 90℃ (WPI-YAP-H), respectively. The intermolecular interactions between WPI and YAP were investigated by fluorescence spectroscopy and circular dichroism analyses. The in vitro bioaccessibility and bioavailability of YAP were determined using a simulated gastrointestinal digestion and human Caco-2 cells model. It was found that the total polyphenols transport efficiency was improved from 39.8% (YAP) to 48.2% (WPI-YAP) and 56.1% (WPI-YAP-H), indicating that the bioavailability of YAP was improved by complexation with WPI. Besides, after complexation with WPI, YAP displayed an improved in vivo effect on alleviating the increase in postprandial blood glucose level than the pure YAP, with WPI-YAP-H showing a better effect. This finding indicates that co-complexation of YAP with WPI is an effective way to improve the functionality of YAP, and the WPI-YAP complexes are also expected to have potential application in designing YAP-containing functional foods. PRACTICAL APPLICATION: The research provided a method to improve the bioavavibility of polyphenols, and the WPI-YAP complex can be developed in designing polyphenols related functional foods.

Rheological and gelling properties of Nicandra physalodes (Linn.) Gaertn. pectin in acidic media.

Nicandra physalodes (Linn.) Gaertn. polysaccharide (NPGP) was previously recognized as a pectic polysaccharide, with a high galacturonic acid content (87.8%) and a low methoxylation degree (28%). In the present study, it was found that NPGP can form self-supporting gels when cooling its heated solutions (2.0%, w/v) acidified by citric acid. It was demonstrated that the decrease in pH led to the suppression in electrostatic repulsions between the pectin chains, thereby promoting pectin chain-chain association mainly through hydrogen bonding. As the pH decreased from 3.2 to 2.4, the gel strength and gel thermal stability were continuously increased. Moreover, it was shown that sucrose addition slightly promoted the gelation and gel thermal stability of NPGP, but the effect of monovalent ions (Na+) and divalent ions (Ca2+) was not significant. Conclusively, our results indicate that NPGP is a new gelling polysaccharide that shows great potential in formulation of acidic gel foods.