Anjun Liu

Transglutaminase-induced crosslinking of gelatin–calcium carbonate composite films

The effects of transglutaminase (TGase) on the rheological profiles and interactions of gelatin-calcium carbonate solutions were studied. In addition, mechanical properties, water vapour permeability and microstructures of gelatin-calcium carbonate films were also investigated and compared. Fluorescence data suggested that the interaction of TGase and gelation-calcium carbonate belonged to a static quenching mechanism, and merely one binding site between TGase and gelatin-calcium carbonate was identified. Moreover, differential scanning calorimetry (DSC), the mechanical properties and the water vapour permeability studies revealed that TGase favoured the strong intramolecular polymerisation of the peptides in gelatin. The microstructures of the surfaces and cross sections in gelatin-calcium carbonate films were shown by scanning electron microscope (SEM) micrographs. The results of the fourier transform infrared spectroscopy (FTIR) indicated that TGase caused conformational changes in the proteins films. Therefore, TGase successfully facilitated the formation of gelatin-calcium carbonate composite films.

Polysaccharides from Lycium barbarum leaves: Isolation, characterization and splenocyte proliferation activity

The polysaccharides from the fruits of Lycium barbarum have received considerable attention in previous publication, but the polysaccharides from the leaves were rarely reported. In the present work, four water-soluble polysaccharide fractions: LBP-I, LBP-II, LBP-III and LBP-IV isolated from L. barbarum leaves were purified through DEAE-Sephadex A-25. LBP-II and LBP-IV respectively showed one symmetrical peak on HPGPC with average molecular weight of 9.39 × 10⁴ Da and 4.18 × 10⁵ Da. UV and IR analysis of the two fractions showed the characteristics of acidic polysaccharides combined with polypeptides or proteins. GC analysis showed LBP-IV was mainly composed of rhamnose, arabinose, xylose, glucose and galactose with molar ratio of 1.61:3.82:3.44:7.54:1.00, and the uronic acid content was 47.68% (w/w) determined by sulfuric acid-carbazole method. ¹H and ¹³C NMR spectra of LBP-IV also showed the presence of carboxyl carbon and five anomeric carbons, and suggested there may be both α- and β-anomeric configurations in this fraction. Moreover, splenocyte proliferation activity assay showed that LBP-IV significantly enhanced the proliferation of splenocyte stimulated by ConA or LPS, indicating the fraction has the beneficial effect on immunostimulating activity.

Structural properties of polysaccharides from cultivated fruit bodies and mycelium of Cordyceps militaris.

The structural properties of polysaccharides, respectively, obtained from the fermented mycelium and cultivated fruiting bodies of the Cordyceps militaris were investigated and compared in this paper. First, the crude polysaccharides were extracted from the mycelium and the fruiting bodies, respectively. The polysaccharides were successively purified by Sevag and chromatography on Sephadex G-100 column to produce two polysaccharides fractions termed CMPS-II and CBPS-II, respectively. The average molecular weights of CMPS-II and CBPS-II were 1.402×10(3) kDa and 1.273×10(3) kDa, respectively, and they were mainly composed of mannose, glucose and galactose in the mole ratios of 1:28.63:1.41 and 1:12.41:0.74, respectively, for CMPS-II and CBPS-II. Afterward, the structural features of CMPS-II and CBPS-II were investigated by a combination of chemical and instrumental analysis, such as FT-IR, periodate oxidation-Smith degradation, GC-MS, NMR and methylation analysis. The results indicated that structurally, both CMPS-II and CBPS-II were 1,3-branched-galactomannoglucan that had a linear backbone of (1→4)-linked α-D-glucopyranose (Glcp). Congo-red test revealed that CMPS-II and CBPS-II existed as triple-helical chains in 0.05-0.15 M NaOH solution.

Sulfated modification of the polysaccharide from Cordyceps_gunnii mycelia and its biological activities

A chemically new sulfated polysaccharide (SPS50) was prepared from the water soluble polysaccharide (PS50), isolated from Cordyceps_gunnii mycelia, by concentrated sulfuric acid method. The yield of crude SPS50 was 62.34% and its specific rotation was [α](D)(20)=-36.75°. The structural characteristics of this chemically sulfated polysaccharide were determined based on the infrared analysis (IR), high performance liquid chromatography (HPLC) and sodium dodecyl sulfate polyacrylamide gel electropheresis (SDS-PAGE). Its biological properties including anti-oxidant and anti-tumor activities were also investigated. The results showed that the anti-oxidant capacity of SPS50 was not as good as SP50 and the anti-tumor activity of SPS50 was much better than PS50. SPS50 showed evident growth inhibition on K562 cells. The tumor inhibition ratio of SPS50 against K562 cells was 69.92%.

Cartilage polysaccharide induces apoptosis in human leukemia K562 cells

In this study, we extracted a polysaccharide (short-chain polysaccharide [PS]) from porcine cartilage and examined its function in chronic myeloid leukaemia by using human K562 cells and mouse L1210 cells. Results of cell proliferation assay indicated that PS inhibited cancer cell growth at different concentrations, while it had little effect on normal cells. The presence of morphological aspects of apoptosis, such as nuclear shrinkage, was shown in H&E stained sections. The occurrence of PS-induced apoptosis was confirmed by TUNEL assay and cell cycle analysis. The results of immunofluorescent staining indicated the molecular mechanism underlying. Through interfering with the cell cycle of tumor cells, PS may induce apoptosis by downregulating the expression level of cyclin D1 and upregulating the level of p21 protein. Correlation analysis of apoptosis and MAPK suggested that inactivation of ERK was crucial for PS induced apoptosis, while JNK phosphorylation had a small effect and p38 was not involved. In vivo assay showed that PS inhibited L1210 cell growth in vivo and prolonged the life span of L1210-bearing mice. We conclude that PS is a polysaccharide with anticancer effects and induced apoptosis in human K562 cells.

Performance of high amylose starch-composited gelatin films influenced by gelatinization and concentration.

In order to study the impact of starch in film performance, high amylose corn starch was composited in gelatin films under different gelatinization conditions and, in high and low concentrations (10 and 50wt.%). It was found that hot water gelatinized starch (Gel-Shw) increased film mechanical strength and was dependent upon the starch concentration. The addition of an alkali component to the starch significantly enhanced the swelling of the starch granules and expedited the gelatinization process. Incorporation of starch, especially the alkalized starch (Sha), into the gelatin films decreased film solubility which improved its water resistance and water vapor permeability (WVP). Multiple techniques (DSC, TGA, FT-IR, and XRD) were used to characterize the process and results, including the crosslinking of the dissolved starch molecules and the particles formed from gelatinized starch during retrogradation process, which played an important role in improving the thermal stability of the composited gelatin films. Overall, the starch-gelatin composition provides a potential approach to improve gelatin film performance and benefit its applications in the food industry.

Effect of ultrasonic treatment on structure and antitumor activity of mycelial polysaccharides from Cordyceps gunnii.

Taking mycelial polysaccharides from Cordyceps gunnii (C. gunnii) as the study subject, the effect of ultrasonic power, time and concentration of polysaccharides on antitumor activity of the polysaccharides was investigated. The ultrasonic processing condition of the polysaccharides was optimized by using orthogonal test design, and determined to be 400 W, 15 min and 1g/L. The change of structures of polysaccharides before and after ultrasonic treatment was also studied. Results show that ultrasonic treatment did not change the characteristic attribute of polysaccharides from C. gunnii. The composition of monosaccharide residues and the category of glycosidic bond have not been changed. But the molecular weight and intrinsic viscosity was reduced, and the alpha-helicity was enhanced after ultrasonic treatment. It was possible that ultrasonic treatment is an effective way for enhancing antitumor activity of polysaccharides.

Selenium modification of β-lactoglobulin (β-Lg) and its biological activity.

β-Lg is a major whey protein in cows milk. This study was aimed to find a new kind of organic selenium compound synthesized with β-Lg and selenium dioxide as raw materials under the conditions of vacuum and low temperature. Fourier transformed infrared spectroscopy revealed that seleno-β-lactoglobulin (Se-β-Lg) displayed a strong band at 878cm(-1), belonging to SeO. Circular dichroism spectra results indicated that the conformation of Se-β-Lg was transformed and α-helical, and unordered structures were increased by 9% and 11.2%, respectively, while β-sheet and β-turn were reduced by 14.2% and 6%, respectively. Electrophoresis and matrix-assisted laser desorption/ionization time of flight mass spectrometry results showed that there were two protein bands (1-Seβ-Lg and 2-Seβ-Lg) in Se-β-Lg, only one β-Lg connected with selenate in 1-Seβ-Lg, but two β-Lgs, connected to each other, and with selenate, in 2-Seβ-Lg. Morphological observation and hematoxylin and eosin staining indicated that Se-β-lg could induce K562 cell apoptosis. These results indicated that Se-β-Lg could be synthesized by selenium conjugating β-Lg and it had antitumor activity.

The Production of Gelatin-Calcium Carbonate Composite Films with Different Antioxidants

Gelatin-calcium carbonate films incorporated with different natural antioxidants (sodium ascorbate, d-sodium erythorbate, and tea polyphenols) were investigated in this study. The results indicated that all of the films with antioxidants displayed promoted tensile strength and higher thickness than that of the control (p < 0.05), and most films had higher values of elongation at break. Furthermore, the addition of antioxidants favored the reduction of water vapor permeability and water solubility in comparison with the control (p < 0.05). The alternations of light transmission could vary depending on the type and concentration of antioxidants. In addition, the surface properties of films were characterized by atomic force microscopy, indicating that antioxidants caused the formation of gelatin-calcium carbonate aggregates and clusters. Moreover, Fourier transform infrared spectroscopy spectra demonstrated that antioxidants facilitated the conformational changes of the secondary structure and functional groups of gelatin in films. Gelatin-calcium carbonate films containing different natural antioxidants exhibited improved 2, 2-diphenyl-1-picryl hydrazyl radical scavenging capacities, compared to the control (p < 0.05).

Characterization of Se-enriched Pleurotus ostreatus polysaccharides and their antioxidant effects in vitro

Selenium-enriched polysaccharides have become a major research focus owing to their high anti-oxidant activities. Selenium-enriched Pleurotus ostreatus polysaccharide (Se-POP) and the native polysaccharide (POP) were obtained by hot water extraction from fresh fruiting bodies of P. ostreatus with or without selenium. Se-POP and POP had similar average molecular weights (0.95×104Da and 0.94×104Da, respectively). Se-POP was mainly composed of fucose, rhamnose, arabinose, galactose, glucose, and xylose, similar to the composition of POP, but in different molar ratios. In an FT-IR analysis, in comparison to POP, two new absorption peaks at 941cm-1 and 1048cm-1 were observed due to COSe and SeO bonds. In vitro study of DPPH, hydroxyl, and ABTS free radicals, Se-POP had a stronger antioxidant capacity than that of POP. Compared to POP, Se-POP had a superior ability to reduce hydrogen peroxide (H2O2)-induced oxidative stress and apoptosis in murine skeletal muscle (C2C12) cells. In general, selenium in Se-POP contributed to high antioxidant and biological activities. Se-POP acts as a potent antioxidant and has the ability to prevent oxidation via reactive oxygen species (ROS) and free radicals in humans. These results suggest that Se-POP is a candidate dietary supplement for functional foods.