Xiuping Dong

Purification and bioactivity of a sulphated polysaccharide conjugate from viscera of abalone Haliotis discus hannai Ino

Abstract A sulphated polysaccharide conjugate ACP I was purified from the viscera of abalone Haliotis discus hannai Ino, and its immunostimulatory and anti-tumour activities were studied in vivo. Effect of ACP I on immune function was investigated in normal and cyclophosphamide-induced immunosuppressive mice. The anti-tumour effect was investigated by growth inhibition of tumour. Dose-dependent increase in spleen and thymus relative weight, lymphocyte proliferation, phagocytosis of macrophage, natural killer cell activity and antibody production was observed in all the tested mice administered with 10, 20 and 40 mg kg−1 body weight of ACP I. Significant increase of the above function was observed especially in immunosuppressive mice at dose of 40 mg kg−1. A significant inhibition of tumour growth was observed in 10, 20 and 40 mg kg−1 ACP I groups, with inhibitory rates of 40.24, 41.91 and 46.43%, respectively. Results suggested that ACP I might have immunomodulating and anti-tumour potential deserving application in functional food industry.

Autophagy plays a potential role in the process of sea cucumber body wall “melting” induced by UV irradiation

The changes of tissue appearances and structures in the process of UV-induced “melting” for sea cucumber (Stichopus japonicus) body wall were studied. And the localization and determination of acid phosphatase (ACP), Cathepsin B and Cathepsin L activities were also investigated. The results show that the connective tissue was damaged with many hollows emerging and the regular collagen bundles were broken apart into irregular fragments. Margination of condensed chromatin at the nuclear membrane was observed. Both Golgi’s body and endoplasmic reticulum swelled, curled, and eventually double-or multi-lamellar vesicles were formed. A number of autophagic vesicles distributed in all through the whole cytoplasm. ACP becomes more active after UV irradiation. The activities of cathepsin B and cathepsin L increased in UV-treated sea cucumbers and both achieved their maximum under certain conditions. It indicates that autophagy plays a potential role in the “melting” process for sea cucumber body wall induced by UV irradiation.

Stimulation of lymphocyte proliferation by oyster glycogen sulfated at C-6 position

In this study, glycogen was extracted from oyster Ostrea talienwhanensis Crosse and used as a model to investigate the structure-activity correlation of polysaccharides. Purified oyster glycogen was characterized by methylation analysis, nuclear magnetic resonance (NMR) spectroscopy and infrared spectroscopy (IR). The oyster glycogen was subsequently sulfated by chlorosulfonic acid-pyridine method, and a C-6 substituted species (SOG) was identified to be the primary sulfated oyster glycogen species by (13)C NMR spectroscopy. The molecular weight and sulfate content of the SOG was determined to be 3.2×10(4) g/mol and 33.6%, respectively. Another sulfated oyster glycogen species (SOG1) with C-2 and C-3 substitution was also identified at a lesser amount in the final product. SOG exhibited a much stronger stimulation effect to splenic lymphocyte proliferation than SOG1 in vitro, indicating that the position of sulfate substitution is a major determining factor on the efficacy of sulfated glycogens to stimulate lymphocyte proliferation.

Optimisation of hydrolysis of purple sea urchin (Strongylocentrotus nudus) gonad by response surface methodology and evaluation of in vitro antioxidant activity of the hydrolysate

BACKGROUND Hydrolysates prepared from sea urchin (Strongylocentrotus nudus) gonad by enzymatic treatment showed strong 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and reducing power. RESULTS Hydrolysis of S. nudus gonad by the commercial protease papain was optimised for maximum degree of hydrolysis (DH) and trichloroacetic acid-soluble peptide index (TCA-SPI) using response surface methodology. Results showed that the optimal conditions were the following: temperature of 48.83 °C, pH of 6.92, enzyme-to-substrate ratio of 3143 U g(-1), and substrate concentration of 83.5 g L(-1). Under these conditions, a DH of 27.96 ± 0.54% and a TCA-SPI of 57.32 ± 0.63% were obtained. The hydrolysate prepared in the optimal conditions was fractionated by an ultra-filtration system and the resultant fraction below 10 kDa was found to effectively scavenge hydroxyl radical (EC(50) = 13.29 ± 0.33 mg mL(-1)) and hydrogen peroxide (EC(50) = 16.40 ± 0.37 mg mL(-1)), inhibit lipid peroxidation (EC(50) = 11.05 ± 0.62 mg mL(-1)), chelate Fe(2+) (EC(50) = 7.26 ± 0.44 mg mL(-1)), and protect mice macrophages against death induced by tert-butyl hydroperoxide. CONCLUSION Hydrolysates prepared from S. nudus gonad have the potential to be applied as natural antioxidant agents.

Effects of endogenous cysteine proteinases on structures of collagen fibres from dermis of sea cucumber (Stichopus japonicus)

Autolysis of sea cucumber, caused by endogenous enzymes, leads to postharvest quality deterioration of sea cucumber. However, the effects of endogenous proteinases on structures of collagen fibres, the major biologically relevant substrates in the body wall of sea cucumber, are less clear. Collagen fibres were prepared from the dermis of sea cucumber (Stichopus japonicus), and the structural consequences of degradation of the collagen fibres caused by endogenous cysteine proteinases (ECP) from Stichopus japonicus were examined. Scanning electron microscopic images showed that ECP caused partial disaggregation of collagen fibres into collagen fibrils by disrupting interfibrillar proteoglycan bridges. Differential scanning calorimetry and Fourier transform infrared analysis revealed increased structural disorder of fibrillar collagen caused by ECP. SDS-PAGE and chemical analysis indicated that ECP can liberate glycosaminoglycan, hydroxyproline and collagen fragments from collagen fibres. Thus ECP can cause disintegration of collagen fibres by degrading interfibrillar proteoglycan bridges.

Changes in collagenous tissue microstructures and distributions of cathepsin L in body wall of autolytic sea cucumber (Stichopus japonicus)

The autolysis of sea cucumber (Stichopus japonicus) was induced by ultraviolet (UV) irradiation, and the changes of microstructures of collagenous tissues and distributions of cathepsin L were investigated using histological and histochemical techniques. Intact collagen fibers in fresh S. japonicus dermis were disaggregated into collagen fibrils after UV stimuli. Cathepsin L was identified inside the surface of vacuoles in the fresh S. japonicus dermis cells. After the UV stimuli, the membranes of vacuoles and cells were fused together, and cathepsin L was released from cells and diffused into tissues. The density of cathepsin L was positively correlated with the speed and degree of autolysis in different layers of body wall. Our results revealed that lysosomal cathepsin L was released from cells in response to UV stimuli, which contacts and degrades the extracellular substrates such as collagen fibers, and thus participates in the autolysis of S. japonicus.

Effect of pH on the physicochemical and heat-induced gel properties of scallop Patinopecten yessoensis actomyosin

Gelation is an important functional property of protein in meats. In this study, we prepared actomyosin from scallop Patinopecten yessoensis adductor muscles and studied the effects of pH on the physicochemical properties of the actomyosin preparation and on its heat-induced gel-forming properties. The results showed that the turbidity and surface hydrophobicity of scallop actomyosin increased with increases in the heating temperature, while the α-helical content concomitantly decreased. Higher turbidity and surface hydrophobicity and lower α-helical content were found to be easily obtained at lower pH values. A high water-holding capacity, strong gel strength, fine gel network and uniform ice crystals were all clearly observed at pH 7.0, indicating that a neutral pH was most beneficial for formation of the heat-induced scallop actomyosin gel. We therefore conclude that both the physicochemical properties of scallop actomyosin and its gel-forming ability during the heating process are pH dependent.

Structural and biochemical changes in dermis of sea cucumber (Stichopus japonicus) during autolysis in response to cutting the body wall

The autolysis of sea cucumber body wall is caused by endogenous proteolysis of its structural elements. However, changes in collagen fibrils, collagen fibres and microfibrils, the major structural elements in sea cucumber body wall during autolysis are less clear. Autolysis of sea cucumber (S. japonicus) was induced by cutting the body wall, and the structural and biochemical changes in its dermis were investigated using electron microscopy, differential scanning calorimetry, infrared spectroscopy, electrophoresis, and chemical analysis. During autolysis, both collagen fibres and microfibrils gradually degraded. In contrast, damage to microfibrils was more pronounced. Upon massive autolysis, collagen fibres disaggregated into collagen fibril bundles and individual fibrils due to the fracture of interfibrillar bridges. Meanwhile, excessive unfolding of collagen fibrils occurred. However, there was only slight damage to collagen monomers. Therefore, structural damage in collagen fibres, collagen fibrils and microfibrils rather than monomeric collagen accounts for autolysis of S. japonicus dermis.

Characterization the carotenoid productions and profiles of three Rhodosporidium toruloides mutants from Agrobacterium tumefaciens-mediated transformation

The red yeast Rhodosporidium toruloides is a known lipid producer capable of accumulating large amounts of triacylglycerols and carotenoids. However, it remains challenging to study its carotenoid production profiles owing to limited biochemical information and inefficient genetic tools. Here we used an Agrobacterium tumefaciens‐mediated transformation (ATMT) to change its carotenoid production and profiles. We constructed R. toruloides NP11 mutant libraries with ATMT, selected three mutants with different colours, characterized their carotenoid products by high‐pressure liquid chromatography–mass spectrometry (HPLC‐MS) analysis and assured differences among those strains in terms of carotenoid production and its composition profiles. We then located T‐DNA insertion sites using the genome walking technology and provided discussions in terms of the new phenotypes. This study is the first of its kind to change the carotenoid production profiles in R. toruloides. Copyright

Water dynamics of Ser-His-Glu-Cys-Asn powder and effects of moisture absorption on its chemical properties

BACKGROUND This study has elucidated moisture dynamics in the soybean peptide, Ser-His-Glu-Cys-Asn (SHECN) powder by using dynamic vapor sorption (DVS) and nuclear magnetic resonance (NMR). We also tried to investigate the effects of moisture absorption on the biological activity and chemical properties of SHECN with some effective methods such as mid-infrared (MIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS). RESULTS DVS results showed that the moisture absorption of SHECN could reach a maximum of 33%, and the SHECN powder after synthesis actually existed in a trihydrate state of SHECN.3H2 O. Low-field NMR revealed that three water proportions including strong combined water, binding water and bulk water were involved in SHECN moisture absorption and absored water dominantly existed in the form of combined water. Magnetic resonance imaging (MRI) and MIR spectroscopy results indicated that moisture absorption could change the morphology and structure of SHECN. After moisture absorption at 50% and 75% relative humidity, 19 volatiles were identified by GC-MS analysis. Additionally, this study showed that a part of reductive groups in SHECN was oxidized and its antioxidant ability declined significantly (P < 0.05) after moisture absorption. CONCLUSION Water absorbed into SHECN powder can significantly change its microstructure and cause its activity to decrease. We must prevent SHECN from absorbing moisture during storage because the water can accelerate the oxidation of samples and promote microbial reactions.