Triple Helix Structure Research Articles

Strong inflammation is essential for expression of articular cartilage-specific citrullinated antigens

To investigate the expression of citrullinated epitopes in articular cartilage protein and whether its expression is sufficient to induce anti-citrullinated protein antibody (ACPA) response in mice. The experimental group was treated with different concentrations of lipopolysaccharide (LPS), heat-inactivated bacteria (Escherichia coli and Staphylococcus aureus) or specific monoclonal antibody against type Ⅱ collagen to induce citrullination of articular cartilage protein, with PBS as the control. Immunohistochemistry with the monoclonal antibody ACC4 (IgG1) that specifically binds to the citrullinated epitope of cartilage protein was performed for detecting the expression of citrullinated protein, with ACC1 (IgG2a) as a positive control antibody and L243 (IgG2a) and Hy2.15 (IgG1) as the negative isotype control. In the in vivo experiment, SD rats were subjected to injection of different doses of LPS in the right knee (with PBS as the controls in the left knee), and 3 days later frozen sections were prepared for immunohistochemical detection of the expression of citrullinated protein. Models of collagen-induced arthritis (CIA) established in different mouse strains were observed for incidence and severity of CIA. Serum samples collected from these models and the sera from rheumatoid arthritis patients were examined for anti-citrullinated protein antibody, and immunohistochemistry was performed to detect the expression of citrullinated protein in the cartilage of the mouse. The citrullinated CII epitope-specific antibody ACC4 did not bind to articular cartilage tissues with different treatments as compared with the positive control antibody ACC1. The ACC4 antibody and the antibodies from patients with rheumatoid arthritis with high titers of anti-citrullinated protein antibody were capable of binding to the synovial tissue around the articular cartilage of the CIA. Luminex analysis showed that the anti-citrullinated protein antibody was lowly expressed in mouse serum, but the anti-type Ⅱ collagen triple helix structure peptide antibody exhibited strong reactivity. Mild acute inflammatory response is not enough to cause citrullination of articular cartilage protein, and the expression of specific epitope requires a high-intensity inflammatory response. Inflammatory articular cartilage protein can express citrullinated epitopes in type Ⅱ collagen-induced arthritis in mice, but the expression of citrullinated epitopes is not sufficient to induce an immune response to anti-citrullinated antibodies. Stronger stimulation signals are required to induce an immune response for producing anti-citrullinated protein antibodies.

Physicochemical Properties, Antioxidant and Antidiabetic Activities of Polysaccharides from Quinoa (Chenopodium quinoa Willd.) Seeds.

Quinoa is known for its rich nutrients and bioactive compounds. In order to elucidate the preliminary structural characteristics and biological activity of polysaccharides from quinoa (QPs), five crude polysaccharides (QPE50, QPE60, QPE70, QPE80 and QPE90) were successively fractionated by gradient ethanol, and their physicochemical properties, antioxidant and antidiabetic activities were analyzed. The results implied that their total sugar contents were 52.82%, 63.69%, 67.15%, 44.56%, and 41.01%, and their weight-average molecular weights were 13,785 Da, 6489 Da, 4732 Da, 3318 Da, and 1960 Da, respectively. Glucose was a predominantly monosaccharide in these QPs, which together in QPE50, QPE60, QPE70, QPE80, and QPE90, respectively, made up 94.37%, 87.92%, 92.21%, 100%, and 100% of the total polysaccharide. Congo red test showed that all five QPs contained triple-helix structure. The Fourier transform-infrared spectroscopy (FT-IR) and X-ray diffractometry (XRD) results suggest that the QPs form a semi-crystalline polymer constituted typical functional groups of polysaccharide including CO, CH and OH. The thermogravimetric analysis (TGA) of QPs showed that weight loss was at about 200 °C and 320 °C. The observation from scanning electron microscope (SEM) and atomic force microscope (AFM) image indicated that the morphology of QPs exhibited spherical shape. Antioxidant and antidiabetic assay exhibited that all five QPs samples had certain antioxidant and antidiabetic activities, and QPE90 showed the best antioxidant and antidiabetic activity. Overall, QPs present a promising natural source of food antioxidants and antidiabetic agents.

Investigation of the Interaction between Epoxides and Collagen in Epoxy Tanning based on BDDGE Cross-linked Collagen Solution

To investigate further the interaction between epoxides and collagen in epoxy tanning, collagen solutions (3 mg/ml) cross-linked with various concentrations (0.5–4-wt%) of 1,4-butanediol diglycidyl ether (BDDGE) at low temperature (4ºC), alkaline conditions (pH = 10) were prepared. The sodium dodecyl sulfate–polyacrylamide gel electrophoresis and Fourier transform infrared spectroscopy confirmed the intact triple-helix structure of the cross-linked collagen. With the increasing concentration of BDDGE, the denaturation temperature measured using VP-DSC increased from 42.56 ºC to 44.25ºC and thermogravimetric analysis showed that the decomposition temperature increased from 333.0ºC to 351.8ºC. In addition, the rheology properties such as G¢, G² and ?* were measured with a rotary rheometer using dynamic frequency scanning. The trinitrobenzensulfonic acid method and atomic force microscopy were used to investigate the interaction between collagen and BDDGE. The results indicated that the changes in cross-linked collagen performance were attributed to the transition of collagen aggregation caused by cross-linking. In addition, the transition point of 2-wt% BDDGE was the key node for the formation of a mature cross-linked network and the cross-linking barely increased above that. It is hoped that these findings deepen the understanding of epoxy tanning and provide guidance for the practical use of epoxides in tanning and biomaterials.

Insights into the effect of artificial sweeteners on the structure, stability, and fibrillation of type I collagen

Artificial sweeteners (AS) are widely used as sugar substitutes because natural sweetener (sugar) leads to a number of health issues, including diabetes, obesity, and tooth decay. Since natural sugar (sucrose), diabetes and skin are highly interlinked, and also sucrose is known to inhibit the fibrillation of collagen, the major protein of the skin, a study on the impact of AS on collagen is important and essential. Herein, we have studied the influence of commonly used AS such as Sucralose (SUC), Aspartame (APM), and Saccharin (SAC) on the structure, stability, and fibrillation of collagen using various spectroscopic methods. The circular dichroism and turbidity results suggest that the AS does not disrupt the triple helix structure and also the fibrillar property of collagen, respectively. The fibrillar morphology was sustained, although there was a trivial difference in the entanglement of fibrils in the presence of SAC, compared to native collagen fibrils. The thermal stability of collagen is maintained in the presence of AS. Fluorescence and STD-NMR results indicate that the interaction between AS and collagen was weak, which supports the intact structure, stability, and fibrillation property of collagen. The current study thus suggests that the chosen AS does not influence collagen properties.

New Nanofibers Based on Protein By-Products with Bioactive Potential for Tissue Engineering.

Concentrated collagen hydrolysate (HC10CC), rabbit collagen glue (RCG), and keratin hydrolysate (KH) were investigated in terms of their extraction from mammalian by-products and processing by electrospinning. The electrospun nanofibers were characterized by scanning electron microscopy coupled with the energy dispersive X-ray spectroscopy (SEM/EDS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), and indentation tests. The cytotoxicity of the electrospun nanofibers was conducted on L929 fibroblast cells using MTT and LDH assays and cell morphology observations. The electrospun RCG and KH nanofibers morphology showed an average size of nanofibers ranging between 44 and 410 nm, while the electrospun HC10CC nanofibers exhibited higher sizes. The ATR-FTIR spectra performed both on extracted proteins and electrospun nanofibers showed that the triple helix structure of collagen is partially preserved. The results were in agreement with the circular dichroism analysis for protein extracts. Furthermore, the viscoelastic properties of electrospun KH nanofibers were superior to those of electrospun RCG nanofibers. Based on both in vitro quantitative and qualitative analysis, the electrospun nanofibers were not cytotoxic, inducing a healthy cellular response. The results of new electrospun protein-based nanofibers may be useful for further research on bioactive properties of these nanofibers for tissue engineering.

Quercetin loaded gelatin films with modulated release and tailored anti-oxidant, mechanical and swelling properties

Quercetin, a flavonoid widely diffused in fruits and vegetables, is known for its good pharmacological qualities, such as anti-oxidant and anti-inflammatory properties. In this work, we loaded quercetin on gelatin films with the aim to develop materials with tailored anti-oxidant, mechanical and stability properties. To this purpose, gelatin films at increasing flavonoid content were prepared using two different solvents, namely H2O/EtOH (EtOH films) and DMSO (DMSO films). Quercetin content increased up to about 3.8 and 1.8 wt% in DMSO and EtOH films, respectively. The use of DMSO as solvent prevents the partial regain of collagen triple helix structure during gelling of gelatin sols and results in remarkable extensibility of the films. At variance, EtOH films display X-ray diffraction patterns and DSC plots in agreement with the presence of triple helix structure, and exhibit reduced swelling and increasing mechanical properties on increasing quercetin content. Moreover, their values of denaturation enthalpy indicate the presence of chemical interaction between the flavonoid and gelatin, which can be responsible of their lower quercetin release in PBS in comparison to DMSO films. The flavonoid release is sustained for both series of films and occurs through anchorage to gelatin nanoparticles. Moreover, both DMSO and EtOH functionalized films exhibit relevant anti-oxidant properties, in agreement with their RSA levels, which are comparable to that of pure quercetin.

Research on the Training Mode of Postgraduate Based on the Triple Helix Structure of Subject Characteristics, Industry Characteristics and Regional Characteristics-Taking Environmental Engineering in XUST as an Example

Taking Xi'an University of science and technology as an example, this paper summarized the key problems existing in the cultivation of postgraduate majored environmental engineering. The training mode of postgraduate majored environmental engineering based on the Triple Helix structure of subject characteristics, industry characteristics, and regional characteristics was constructed on the basis of analyzing the characteristics of the university in subjects, industries and regions. It hopes to provide the same guidance for education reform of postgraduate majored environmental engineering in XUST and similar universities.

Immunomodulatory effects of the polysaccharide from Craterellus cornucopioides via activating the TLR4-NFκB signaling pathway in peritoneal macrophages of BALB/c mice

The immunoregulatory effect and immunologic response mechanism of Craterellus cornucopioides (L.) Pers. polysaccharide (CCP) with a triple-helix structure on peritoneal macrophages was investigated in vitro for the first time. These studies demonstrated that treatment of peritoneal macrophages with 80 μg/mL CCP for 48 h significantly strengthened their phagocytic function as well as increases the activities of lysozyme (LZM), acid phosphatase (ACP) and succinodehydrogenase (SDH) when compared with the untreated group. Furthermore, Western Blot and quantitative real-time polymerase chain reaction (qRT-PCR) assays demonstrated that 80 μg/mL CCP activated macrophages, significantly increased mRNA expression of cytokines (IL-8, IL-1β, IFN-α and TNF-α) and upregulated the protein expression of cell membrane receptor TLR4, as well as its downstream protein kinase products (MyD88, TAK1, P-IKKα/β and P-MEK) through activation of the TLR4-NFκB pathway in peritoneal macrophages. In conclusion, these results showed that the immunomodulatory mechanism of CCP in peritoneal macrophages was associated with the release of NO, related enzymes and cytokines by stimulating the NF-κB p50 pathway via TLR4-MyD88-TAK1 signaling.

Regulation of nano-encapsulated tea polyphenol release from gelatin films with different Bloom values

Active packaging is an emerging technology for food preservation in recent years, to effectively control the sustained release of antioxidants. Herein, antioxidant films were prepared by using gelatins (100, 150, 225 Bloom values) as film matrix and embedding tea polyphenol (TP)-loaded chitosan nanoparticles (CSNs). Gelatin with high Bloom value had more triple helix structures and more significant entanglements between molecular chains, resulting in more viscous film-forming solutions, which led to a more stable system with better dispersed CSNs. TP and CSNs remained chemically stable and formed new hydrogen bonds with gelatin molecules, but did not significantly affect the secondary structure of gelatin. There was a combined effect between the CSNs dispersion and the gelatin structure on film swelling in fatty food simulants, where the films prepared with the gelatin with lower Bloom value had lower swelling degree. This swelling degree was closely related to the release of TP, since the film prepared with the gelatin with Bloom 100 showed the lowest total release of TP in 50% and 95% ethanol simulants. Also, as expected, the antioxidant activity revealed that the CSNs could effectively control the release of TP from films by inhibiting the migration of TP.

Starch-Leather Waste Gelatin Films Cross-Linked with Glutaraldehyde

Gelatin extracted from chromium-tanned leather wastes (CTLW) has a lower molar mass because of the more aggressive extraction process needed to disrupt chromium-collagen bonds when compared to gelatin extracted from the bones, skin, and connective tissues of animals. As a consequence, CTLW gelatin is more hydrophilic, thus it is harder to apply in the production of polymers. To overcome this issue, in this study, films produced with starch, CTLW gelatin, commercial gelatin (as a comparative), and their blends were cross-linked with glutaraldehyde. The cross-linking reduced the crystallinity of the films, impairing the reorganization of gelatin chains into a triple helix structure, which balanced the effect of the higher molecular chain, while not altering the films’ tensile strength. It increased the elongation at break and reduced the solubility and the swelling degree by up to 53% and 69%, respectively. These results stand as a great advance for the practical use of starch-CTLW gelatin films.

Visualization of Long Noncoding RNA MEG3 in Living Cells by a Triple-Helix-Powered 3D Catcher.

Visual imaging of long noncoding RNA (lncRNA) MEG3, a newfound regulator of transactivation and tumor growth suppression, is conducive to unlock the secrets of MEG3 in some important biological processes. Here, for the first time, we designed a DNA tetrahedron-based three-dimensional (3D) catcher for imaging cytoplasmic lncRNA MEG3 in living cells. The 3D catcher is composed of a triple-helix-forming dsDNA with capacity to bind the 5'-end GA-rich domain of the lncRNA MEG3 and four hairpin-shaped antisense sequences toward contiguous domain on MEG3. Once ingested by the cell, the 3D catcher quickly captures lncRNA MEG3 via forming a DNA-RNA triple-helix structure and triggering the hybridization-based string disassembly of the catcher. Concomitantly, the quenched hairpin is opened and the fluorescent signal undergoes lighting on conversion. Ascribed to the triple-helix-induced "domino effect," the disassembly reaction time is greatly shorter than the reaction with the inability to form a triple helix. The 3D catcher allows detection of long-chain targets as long as 129 nucleotide (129 nt) with a detection limit of 0.36 nM and distinguishes endogenous lncRNA MEG3 fragments in living cells between hepatoma cells and normal hepatocytes, which provides a reliable strategy for monitoring endogenous long fragment nucleic acid biomarkers in early clinical lesion diagnoses.

Corrosion of Heritage Objects: Collagen-Like Triple Helix Found in the Calcium Acetate Hemihydrate Crystal Structure.

Helical motifs are common in nature, for example, the DNA double or the collagen triple helix. In the latter proteins, the helical motif originates from glycine, the smallest amino acid, whose molecular confirmation is closely related to acetic acid. The combination of acetic acid with calcium and water, which are also omnipresent in nature, materializing as calcium acetate hemihydrate, was now revealed to exhibit a collagen‐like triple helix structure. This calcium salt is observed as efflorescence phase on calcareous heritage objects, like historic Mollusca shells, pottery or marble reliefs. In a model experiment pure calcium acetate hemihydrate was crystallized on the surface of a terracotta vessel. Calcium acetate hemihydrate crystallizes in a surprisingly large unit cell with a volume of 11,794.5(3) Å3 at ambient conditions. Acetate ions bridge neighboring calcium cations forming spiral chains, which are arranged in a triple helix motif.

Correlation of proline, hydroxyproline and serine content, denaturation temperature and circular dichroism analysis of type I collagen with the physiological temperature of marine teleosts

Fish products are a promising source of collagen; however, these extracts are biochemically unstable. Acid-soluble collagen (ASC) was isolated from the skin of eleven fish species at various physiological temperatures (Tp). Structural features of these samples were analysed in detail using Circular Dichroism (CD) and compared to their biochemical characteristics. Positive correlation (r = 0.74, p < 0.01) between the Tp and ratio of positive peak intensity to negative peak intensity (Rpn) in CD analysis suggested a higher thermal stability of ASC from warm-water fish, owing to a higher content of cyclic imino acids, such as proline and hydroxyproline (Hyp). Conversely, cold-water fish ASCs contain significantly higher levels of acyclic, hydroxyl groups carrying Ser. These results indicated that CD spectrum techniques including Rpn measurement are concise and helpful for direct detection of the triple helix structure of fish collagens, and that this structure is tightly linked to thermostability of this molecule.

Analysis of Long‐noncoding RNA Structure‐Function Relationship in Prostate Cancer

The noncoding RNA (ncRNA) revolution has revealed myriad RNA species that play critical roles at all stages of life, including developmental biology and disease progression. For example, two long ncRNAs (lncRNA), Metastasis Associated Lung Adenocarcinoma Transcript‐1 (MALAT1; ~6.7 kb) and Second Chromosome Locus Associated with Prostate‐1 (SChLAP1; ~1.5 kb), are basally expressed in normal prostate tissue but are dysregulated in prostate cancer. MALAT1 acts in trans at nuclear speckles during mRNA post‐transcriptional processing while SChLAP1 acts in cis to influence oncogenic gene expression. There is compelling evidence that the 3′‐end of MALAT1 is a triple helix structure that acts as a molecular knot, driving transcript accumulation in cancer cells and furthering its metastatic potential, but we currently lack any biophysical data detailing the relationship between SChLAP1 structure and function. In general, the relationship among lncRNA structure, dynamics, and function is not well understood; for example, even with high‐resolution structures of the MALAT1 triple helix, questions remain regarding the role of intrinsic dynamics in transcript stability or protein binding. As lncRNA represent an underexplored therapeutic avenue, this work aims to investigate the role of lncRNA structure and dynamics in driving prostate cancer metastasis.Current work includes: 1) Understanding the role of the MALAT1 3′‐end triple helix structure and dynamics in global transcript stability and 2) Conducting the first biophysical analyses of SChLAP1 and identifying structural elements that are critical to metastasis. For the MALAT1 project, we have performed chemical probing experiments using both SHAPE‐ and DMS‐MaP chemical probing on the MALAT1 triple helix and 5′‐end extensions, revealing different conformations of the triple helix region. Additionally, we have performed exonuclease degradation assays on the triple helix and 5′‐end extensions in triplex de/stabilizing buffer conditions, showing that transcript stability is indeed tied to triple helix structural dynamic. For the SChLAP1 project, we have determined the first secondary structure model of full‐length SChLAP1 and have data supporting the formation of independent folding domains that when deleted from the full‐length transcript lower the invasive phenotype of prostate cells. We are currently working to investigate the tertiary structure of SChLAP1 and identify structure ensembles. Future work aims to design novel in‐cell mutational studies to identify regions of SChLAP1 that are critical for driving cell migration and invasion, two hallmarks of aggressive prostate cancer. This work will deepen our current understanding of the lncRNA MALAT1 triple helix dynamics in driving prostate cancer metastasis and provide the first biophysical and biochemical assessment of the lncRNA SChLAP1. Through this pursuit, we will provide the basis for assessing novel lncRNA structure‐function relationships and therapeutically targeting lncRNA in cancer.Support or Funding InformationEJM funded through grants award to AEH: Prostate Cancer Foundation YIA and NIH MIRA

Chemical structure and effects of antioxidation and against α-glucosidase of natural polysaccharide from Glycyrrhiza inflata Batalin

GIBP, a homogeneous polysaccharide extracted from Glycyrrhiza inflata Batalin with a molecular weight 1.96 × 103 kDa, had a triple helix structure, smooth and sheet-like structure. Comprehensive analysis showed that the main chain of GIBP was composed of α-D-1,4 linked glucose, branch points were composed of α-D-1,3,6 and α-D-1,2,3,6 linked glucoses, and side chains were composed of α-D-1,3 and β-D-1,6 linked galactose, β-L-1,2 linked arabinose, α-D-1,3 and β-D-1,3 mannose. The scavenging abilities of GIBP (3 mg/mL) against DPPH radical, OH radical, O2− radical and ABTS were 50.75 ± 0.13% and 52.32 ± 0.13, 25.84 ± 0.35% and 44.57 ± 0.15% and it also demonstrated an obvious dose-effect relationship. The inhibitory activity of α-glucosidase showed that the inhibitory effect of GIBP was enhanced with the increase of concentration. When the concentration reached 6 mg/mL, the inhibition rate of α-glucosidase activity reached 64.77%. And the ka, kd and KD were 6.472 × 104 1/Ms., 2.934 × 10−3 1/s and 4.534 × 10−8 M.

Comprehensive Assessment of Nile Tilapia Skin (Oreochromis niloticus) Collagen Hydrogels for Wound Dressings.

Collagen plays an important role in the formation of extracellular matrix (ECM) and development/migration of cells and tissues. Here we report the preparation of collagen and collagen hydrogel from the skin of tilapia and an evaluation of their potential as a wound dressing for the treatment of refractory wounds. The acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were extracted and characterized using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), differential scanning calorimetry (DSC), circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) analysis. Both ASC and PSC belong to type I collagen and have a complete triple helix structure, but PSC shows lower molecular weight and thermal stability, and has the inherent low antigenicity. Therefore, PSC was selected to prepare biomedical hydrogels using its self-aggregating properties. Rheological characterization showed that the mechanical strength of the hydrogels increased as the PSC content increased. Scanning electron microscope (SEM) analysis indicated that hydrogels could form a regular network structure at a suitable PSC content. Cytotoxicity experiments confirmed that hydrogels with different PSC content showed no significant toxicity to fibroblasts. Skin repair experiments and pathological analysis showed that the collagen hydrogels wound dressing could significantly accelerate the healing of deep second-degree burn wounds and the generation of new skin appendages, which can be used for treatment of various refractory wounds.

Synergized subcritical-ultrasound-assisted aqueous two-phase extraction, purification, and characterization of Lentinus edodes polysaccharides

The effect of a synergized two-step subcritical water extraction (SWE) and simultaneous multi-frequency ultrasound-assisted alcohol/salt aqueous two-phase extraction (MFu-AATPE) on the yield, physicochemical, structural characteristics, and antioxidant activities of Lentinus edodes polysaccharides (LEPs) was investigated. Crude LEP extracted under subcritical extraction (31.14%) was purified using dual and triple frequency ultrasound-assisted aqueous two-phase systems giving a yield of 94.57% and 97% respectively. Compared with the dual-frequency sonication (20/40 kHz), the triple frequency sonication (20/40/60 kHz) gave maximum yield and improved the desalination rate by 33.6%. Congo red analysis revealed triple helix structures. Gas Chromatography analysis showed the existence of mannose, glucose, arabinose, xylose, and galactose whilst spectral similarities were observed through Fourier Transform Infrared Spectroscopy. The average molecular weight (Mw) was 83.6170 Da, 2384 Da and 2387 Da for control, dual and triple frequency samples respectively. Ultrasound treated polysaccharides displayed stronger antioxidant activities against the 2.2-diphenyl;-1 picrylhydrazyl (DPPH), 2, 2ʹ-azino-bis 3-ethylbenzothiazoline-6 sulfonic acid (ABTS) and hydroxyl radicals, thus demonstrating their potency in reducing oxidation. However, the microstructure of the triple frequency treated sample was altered compared to the dual-frequency sample. Therefore, this study demonstrated the efficacy of SWE in crude LEPs extraction and illustrated MFu-AATPE as an efficient technique that selectively isolates polysaccharides and enhances extraction efficiencies.

A label-free resonance light scattering biosensor for nucleic acids using triple-helix molecular switch and G-quadruplex nanowires

In this work, a label-free resonance light scattering (RLS) biosensor based on triple-helix molecular switch (THMS) and G-quadruplex nanowires (G-wires) for HAV DNA and microRNA-31 detection was developed. The target can combine with the loop sequences of triple-helix, and opened the triple-helix structure as well as liberated the G-rich sequences which were self-assembled into G-wires in the presence of K+ and Mg2+, causing an obvious enhancement of RLS intensity. Meanwhile, the RLS signal at 304 nm was linear with the logarithm of target concentration in the range of 50 pM to 300 nM, and the limit of detection is as low as 7.1 pM for HAV DNA and microRNA-31, respectively. Moreover, qualitative analysis of HAV DNA and microRNA-31 was successfully achieved in human serum samples and cancer cell lysates. The biosensor holds a great promise for universal RLS sensing platform for sensitive detection of various targets just by changing the sequence of the THMS in the loop and be a biosensing platform for early clinical diagnosis and biomedical research.

Macromolecular behavior, structural characteristics and rheological properties of alkali-neutralization curdlan at different concentrations

Curdlan is insoluble in water at ambient temperatures due to its rigid triple helix structure, which greatly limits its applications in the food industry. Alkali-neutralization (AN) treatment is a promising strategy for curdlan dissolution. In this study, the changes in macromolecular behaviors, microstructures, structural characteristics and rheological properties of curdlan before and after AN treatment at different alkali and acid concentrations (0.1–1.0 M) were analyzed and evaluated. Results showed that the AN-treated curdlans in aqueous solutions underwent conformation transitions from ordered triple helices to loose triple helices and then random coils with increased water solubility and reduced intrinsic viscosity, molecular weight, and rheological property. These findings were attributed to the breakdown of intra-/inter-molecular hydrogen bonds. Compared with untreated commercial curdlan, AN treatment significantly affected the microstructure, crystallinity, and thermal property of the AN-treated curdlans but hardly changed their (1 → 3)-β-D-glucopyranosidic linkages. Therefore, this study would provide a theoretical basis for gaining insight into the AN treatment for curdlan and further give a feasible and effective way for improving solubility of water-insoluble curdlan to expand its potential applications in food industry and biomedicine.

An eco-friendly approach for leather manufacture based on P(POSS-MAA)-aluminum tanning agent combination tannage

In this work, a novel eco-friendly wet-white tanning approach based on aluminum sulfate and P(POSS-MAA) composite material has been developed to avoid environmental pollution caused by chromium as well as to improve leather performances. shrinkage temperature (Ts) of combination tanned leather was 73.5 °C higher than aluminum tanned leather, and its whiteness, mechanical properties, thermal stability were obviously higher than those of conventional chrome tanned leather. Scanning electron microscopy (SEM) showed that collagen fibers were dispersed and tanning agents were evenly distributed in collagen fibers. Fourier transform infrared spectroscopy (FT-IR) results revealed that P(POSS-MAA) and aluminum sulfate bonded between collagen bundles and did not enter into the procollagen molecule, destroying the triple helix structure of collagen, which was consistent with X-ray diffraction (XRD), X-ray photo-electron spectroscopy (XPS) and Molecular simulation (MS). Moreover, environmental impact assessment showed that the BOD5/CODCr of the combination tanning wastewater was more than 0.3, and its biodegradability was superior to that of aluminum tanning and conventional chrome tanning processes. These findings provide a potential application of P(POSS-MAA) to meet related technologies toward eco-friendly leather manufacture.