Shanbai Xiong

Role of secondary structures in the gelation of porcine myosin at different pH values

Secondary structures, gelation properties and their relationships in porcine myosin were studied by circular dichroism, dynamic rheological measurement and scanning electron microscopy. Gelling of porcine myosin involved a change in myosin conformation with protein-protein and protein-water interactions. The gelation properties were strongly pH and temperature dependent. Near the pI (pH 5.5 and 6.0), porcine myosin could spontaneously coagulate at 15°C resulting partially from the presence of more β-sheets. Myosin at pH6.5-9.0 began to form a gel at temperatures greater than 38°C. Heating caused α-helices to partially turn into β-sheets and random coils. Subsequently, myosin aggregated and formed a gel network. The gel strength decreased and the water-holding capacity (WHC) increased with increasing pH. Correlation analysis indicated that both the unfolding of α-helices and the formation of β-sheets favored the gelation of porcine myosin. A high β-sheet fraction prior to heating resulted in a low WHC of resultant gel. A compact and uniform gel was also obtained at pH6.5.

Development of collagen/polydopamine complexed matrix as mechanically enhanced and highly biocompatible semi-natural tissue engineering scaffold

To improve the mechanical properties and biocompatibility of collagen I matrix, a novel and facile strategy was developed to modify porcine acellular dermal matrix (PADM) via dopamine self-polymerization followed by collagen immobilization to enhance the biological, mechanical and physicochemical properties of PADM. Mechanism study indicated that the polymerization of dopamine onto PADM surface could be regulated by controlling the amount of hydrogen bonds forming between phenol hydroxyl (COH) and nitrogen atom (NCO) within collagen fibers of PADM. The investigations of surface interactions between PDA and PADM illustrated that PDA-PADM system yielded better mechanical properties, thermal stability, surface hydrophilicity and the structural integrity of PADM was maintained after dopamine coating. Furthermore, collagen (COL) was immobilized onto the fresh PDA-PADM to fabricate the collagen-PDA-PADM (COL-PDA-PADM) complexed scaffold. The MTT assay and CLSM observation showed that COL-PDA-PADM had better biocompatibility and higher cellular attachment than pure PADM and COL-PADM without dopamine coating, thus demonstrating the efficacy of PDA as the intermediate layer. Meanwhile, the expression of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) of COL-PDA-PADM were investigated by an in vivo study. The results revealed that COL-PDA-PADM could effectively promote bFGF and VEGF expression, possibly leading to enhancing the dura repairing process. Overall, this work contributed a new insight into the development of a semi-natural tissue engineering scaffold with high biocompatibility and good mechanical properties. STATEMENT OF SIGNIFICANCE Obtaining scaffolds with high biocompatibility and good mechanical properties is still one of the most challenging issues in tissue engineering. To have excellent in vitro and in vivo performance, scaffolds are desired to have similar mechanical and biological properties as the natural extracellular matrix, such as collagen based matrix. Utilizing the surface self-crosslinking and coating strategy, we successfully obtained a novel semi-natural platform with excellent biological and mechanical properties from porcine acellular dermal matrix (PADM), polydopamine and collagen. The results confirmed that this scaffold platform has very excellent cellular performance and very little toxicity/side effects in vivo. Therefore, this semi-natural scaffold may be an appropriate platform for tissue engineering and this strategy would further help to develop more robust scaffolds.

Effect of Mild Ozone Oxidation on Structural Changes of Silver Carp (Hypophthalmichthys molitrix) Myosin

To produce high-quality surimi, we investigated the effect of ozone-induced mild oxidation on structural changes of silver carp myosin by analyzing circular dichroism (CD), intrinsic fluorescence, the sulfhydryl group, surface hydrophobicity, SDS-PAGE, and dynamic light scattering (DLS) of myosin. Mild ozone oxidation of myosin was performed by applying gaseous ozone for a short time. Results showed that the content of sulfhydryl group decreased, and carbonyl content and surface hydrophobicity increased with an increase in ozone treatment time. A red shift in the maximum wavelength of intrinsic fluorescence indicated the unfolding of oxidized myosin. Further conformational change of myosin was illustrated by CD; α-helical content decreased significantly and β-turn, β-sheet, and random coil content increased with increased ozone treatment time, which demonstrated the rearrangement of β-structure in myosin. The results from DLS and SDS-PAGE indicated that soluble oligomers or aggregates were formed by disulfide bonds under mild ozone treatment. Therefore, ozone-induced mild oxidation did not strongly alter myosin structure but promoted myosin partial unfolding, which might result in exposing more cross-linking sites for the formation of surimi gel.

Heat-induced denaturation and aggregation of actomyosin and myosin from yellowcheek carp during setting

Thermal inactivation kinetics of Ca²⁺-ATPase, changes in turbidity and rheological properties of actomyosin and myosin from yellowcheek carp during setting at different temperatures were investigated. Actomyosin and myosin setting at 40-45 °C exhibited greater extent and more rapid Ca²⁺-ATPase inactivation compared to at 25-30 °C. Formation of protein aggregates and three-dimensional network structures of actomyosin and myosin at 25-30 °C was far less than those at 40-45 °C. Thermal stability of actomyosin was higher than that of myosin as revealed by its higher activation energy for the inactivation of Ca²⁺-ATPase. Actomyosin and myosin also exhibited different dynamic rheological properties, especially when the setting temperatures were 40 and 45 °C.

Gel characteristics and microstructure of fish myofibrillar protein/cassava starch composites

The changes in fish myofibrillar protein/cassava starch composites in the starch fraction range from 0 to 1, with their total content maintained at 60mg/mL, were investigated in terms of textural properties, rheological behaviours, morphology, spatial distribution and protein molecular structure. The results revealed that the starch fraction of 0.5 was a critical point for the conversion of the protein matrix to starch matrix and conversion of the gel from elastic to weak. Moreover, the protein-starch synergistic effect on the storage modulus was strongest at fractions of 0.5 and 0.6, due to the formation of a semi-interpenetrating network, with more amylose from the melted starch granules interpenetrated with the protein molecules, and the absorption of water by the starch granules to concentrate the protein matrix. Additionally, no covalent interaction between the protein and starch occurred with increasing starch fraction, thus having no significant influence on the protein secondary structure.

Characterization of cationic starch flocculants synthesized by dry process with ball milling activating method

The cationic starch flocculants were synthesized by the reaction of maize starch which was activated by a ball-milling treatment with 2,3-epoxypropyl trimethyl ammonium chlorides (ETMAC) using the dry method. The cationic starches were characterized by several approaches including scanning electron microscope (SEM), degree of substitution (DS), infrared spectrum (IR), X-ray diffraction (XRD), flocculating activity, electron spin resonance (ESR), and solid-state nuclear magnetic resonance (NMR). The effect of mechanical activation on starch etherifying modification was investigated. The mechanical activation cracked starch granules and destructed their crystal structures. This resulted in enhancements to the reaction activity and reaction efficiency, which was approved by ESR and solid state NMR. The starch flocculants, synthesized by the reaction of mechanically activated starches at 90°C for 2.5h with ETMAC at molar ratio of 0.40:1.00, showed good flocculation activity. The substitution degree (0.300) and reaction efficiency (75.06%) of starch flocculants synthesized with mechanically activated starches were significantly greater than those of starch flocculants with native starches (P<0.05).

Effects of Ozone Treatments on the Physicochemical Changes of Myofibrillar Proteins from Silver Carp (Hypophthalmichthys molitrix) during Frozen Storage

Physicochemical changes of myofibrillar proteins from silver carp surimi during frozen storage as affected by two manners of ozone treatments were investigated. For preparation of surimi treated with ozone, ozone water (8 mg/L) was used in either the first (To1) or the second (To2) cycle of rinsing. As compared with control samples (Tc) (rinsing two cycles with water), myofibrillar proteins from To1 surimi showed slightly lower free sulfhydryl contents and higher surface hydrophobicity throughout frozen storage and lower Ca2

Fabrication of a novel bio-inspired collagen–polydopamine hydrogel and insights into the formation mechanism for biomedical applications

The bio-inspired approach to the construction of hydrogels with both excellent biological properties and superior initiative adhesive ability to cells is a crucial intersection of the branches of biomaterials science and biotechnology. In the present work, a novel bio-inspired collagen–polydopamine (COL–PDA) hydrogel has been successfully fabricated via collagen self-assembly and the incorporation of PDA. Systematic FTIR and XRD analysis confirmed that the hydrogen bond interactions between collagen and PDA did not destroy the triple helix conformation of collagen which is mainly responsible for the good biological properties of the COL–PDA hydrogel. In comparison with a pristine collagen hydrogel, the physicochemical properties (i.e. porosity, swelling ratio and water holding capacity) of COL–PDA hydrogels could be tuned by modulating the extent of interaction between COL and PDA with the change of dopamine concentrations. The further analysis of AFM observation indicated that a higher dopamine concentration could interrupt the aggregation or self-assembly of collagen molecules into fibrils via the extensive self-polymerization process of dopamine. Furthermore, the formation of a fibrous network could also be controlled by the self-assembly of collagen through varying the dopamine concentration, thus to adjust the thermal stability, enhance the resistance ability to enzymatic degradation and further cause promoted chain entanglement and forming increased elasticity. In addition, owing to the combined biological properties of COL and PDA, fabrication of a bio-inspired COL–PDA hydrogel has significant potential for the development of novel collagen hydrogels with good biological property and initiative adhesive ability to cells in biomedical applications.

Effects of high intensity unltrasound on structural and physicochemical properties of myosin from silver carp

Myosin from silver carp was sonicated with varying power output (100, 150, 200 and 250W) for 3, 6, 9, and 12min. The changes in the structure and physicochemical properties of myosin were evaluated by dynamic light scattering, SDS-PAGE and some physicochemical indexes. The ultrasound treatments induced a significant conversion of myosin aggregates to smaller ones with a more uniform distribution, and obvious enhancement in solubility. The structure of myosin was also notably changed by sonication, with a decrease in Ca2+-ATPase activity and SH content, and an increase in surface hydrophobicity. Furthermore, SH groups were oxidized, leading to a decrease in reactive SH and total SH contents. SDS-PAGE analysis revealed that ultrasound could induce the degradation of myosin heavy chain and change the protein fraction of myosin. Collectively, the ultrasonic treatment of 100W for 3min showed slight influence on the SH content, S0-ANS, and electrophoretic patterns, and the extent of changes in myosin structure and physicochemical properties tended to increase with ultrasonic power and time. The integrated data indicate that ultrasonic treatment can facilitate the improvement of the solubility and dispersion of myosin, but the choice of a suitable ultrasonic condition to avoid oxidation and degradation of myosin is very important.

Gelling Properties of Fish/Pork Mince Mixtures.

The gel properties of silver carp/pork mince mixtures were investigated as well as the protein structural changes and interactions during gelling using rheology, SEM, and FT-Raman spectroscopy. The breaking force values for gels containing 0% to 40% pork was significantly lower (P < 0.05) compared with gels containing 50% to 100% pork. Gels containing 70% to 100% pork had significantly higher (P < 0.05) breaking force values compared with gels containing 50% to 60% pork. Deformation values were more mixed. Dynamic rheological data suggested that mixing fish and pork at 3:7 could strengthen the gel network. The addition of 40% pork or above, significantly decreased (P < 0.05) the water retention of the gels compared with the 100% fish gels. The dimensional ordering of gels was also reduced by addition of pork. The reduced ordering was one of the reasons for the low water retention for fish/pork mixed gels. Raman spectral analysis confirmed that mixing fish and pork in 7:3 and 3:7 ratios could promote hydrophobic interactions such as bringing tyrosine residues into the intermolecular interface. The interactions in the 3:7 fish/pork mixed gels were favorable for forming a stronger gel. However, the interactions in the 7:3 fish/pork mixed gels were adverse. The water retention of gels was related to both molecular interactions and secondary structures of protein as well as the microstructure of the gels.