International Journal of Biological Macromolecules最新文献

Euryales Semen (ES) is a highly nutritious food with low digestibility, which is closely associated with its endogenous phenolic compounds. In this study, five phenolic compounds (naringenin, isoquercitrin, gallic acid, epicatechin and quercetin) with high concentrations in ES were selected to prepare starch-polyphenol complexes. Subsequently, the effects of endogenous polyphenols on the structure, physicochemical properties and digestion characteristics of ES starch were studied using multiple techniques. The addition of phenolic compounds markedly reduced the in vitro digestibility, swelling power, gelatinization enthalpy, while increased the solubility of ES starch. Fourier-transform infrared spectroscopy and X-ray diffraction analysis showed that phenolic compounds interacted with the starch through non-covalent bonds. Five phenolic compounds inhibited α-amylase activity through a mixed competitive inhibition mechanism, with the inhibition potency ranked as follows: quercetin > epicatechin > gallic acid > isoquercitrin > naringenin. The spectroscopic analysis and molecular dynamics simulations confirmed that five phenolic compounds interacted with the amino acid residues of α-amylase through hydrogen bonding and hydrophobic interactions, caused α-amylase static fluorescence quenching, and altered its conformation and microenvironment. This study provides a better understanding of the interaction mechanisms between ES starch and polyphenols, and supports the development of ES as a food that lowers sugar levels.

To improve the gelling properties of konjac glucomannan/curdlan (KGM/CUD) composite hydrogels, KGM/CUD composite hydrogels were treated by freeze-thawing. Herein, we focus on the effects of freeze-thaw cycles, freezing temperature, and freezing time on the structural and mechanical properties of KGM/CUD composite hydrogels. SEM and SAXS results showed that ice crystals generated by freezing extruded the molecular chains and increased the cross-linking density between molecular chains, which resulted in a denser gel microstructure. Among them, the freeze-thaw treatment at -20 °C for 12 h can effectively reduce the correlation length (ξ). According to mechanical testing, freeze-thawed gels for 48 h reached 408-, 826-, and 840-fold of the hardness, gumminess and chewiness of unfrozen, respectively. After freeze-thaw treatment, the energy storage modulus (G') of the gel increased to 9872 Pa, the residual mass after heating was up to 27.9 %, the water holding capacity (WHC) was reduced to 80.85 %. In addition, low-field nuclear magnetic resonance results confirmed that the freeze-thaw treatment promoted the formation of ice crystals from water molecules, which realized the transition of the water state, thus reducing the water mobility of the gel. This study provides a facile and efficient strategy for designing hydrogels products with exceptional texture and sensory characteristics.

In this study, effects of polylactide molecular weight, i.e., high (HPLA), medium (MPLA), low (LPLA), and dichloromethane (DCM)/dimethyl sulfoxide (DMSO) blend ratio on cellulose nanocrystal (CNC) dispersion quality in solution casted PLA/CNC nanocomposites were investigated via small amplitude oscillatory shear rheological analysis, while crystallization behavior, thermal degradation, morphological structure of the nanocomposites were also reported. Due to its low dielectric constant, none of the nanocomposites with 100DCM indicated a change in their complex viscosity as a result of poor CNC dispersion. This is while the increase in DMSO content (50%vv^-1) improved CNC dispersion. The superior CNC dispersion-ability in PLAs with lower molecular weight was confirmed. The poorer CNC dispersion in HPLA attributes to hindering effect of higher molecular weight on solvent and nanoparticle diffusion. The better dispersed CNCs influenced crystal nucleation behavior of PLAs and increased crystallinity degree. In addition, the impact of well-dispersed CNCs on fiber formation quality of nanocomposites was reported. Introducing finely dispersed CNCs (1 wt%) in LPLA refined fiber diameters around 1200 nm with more homogenous structure. Besides, the use of 100DCM and the use of DMSO at high contents (50%vv^-1) deteriorated fiber formation, respectively, due to low conductivity of DCM and high boiling temperature of DMSO.

Tma12 is a fern-derived biopesticide (22 kDa) whose LPMO activity is associated with its insecticidal activity. The absence of the last 9 amino acids in the crystal structure of Tma12 suggested a possibility of its C-terminus processing. In this communication, we have shown the importance of protein C-terminus in the insecticidal activity. Additionally, we have also established the role of N-linked glycosylation in protein stability. Pichia produced (His)₆ tagged Tma12 in two forms. The 30 kDa protein comprising 192 amino acid residues did not show insecticidal activity. Contrary, 24 kDa protein exhibited toxicity to whiteflies with an LC₅₀ 1.38 μg/ml. Absence of (His)₆ tag in 24 kDa protein indicated processing at the C-terminus which was confirmed with deletion mutagenesis. Failure in expressing glycosylation defective mutant suggested the importance of glycans in the stability of Tma12. New findings together with earlier reports suggest that along with the N-terminal catalytic center, correct C-terminus is pivotal for anti-whitefly activity of Tma12.

Chitinase, an enzyme that hydrolyzes β-1,4-glycosidic bonds to degrade chitin, is essential for the digestion of chitin in fish. In this study, the chitinase OpCht from Odontobutis potamophila was expressed in Pichia pastoris, and its enzymatic properties and functional effects were evaluated. The findings revealed that OpCht exhibited optimal activity at pH 6.0 and 50 °C, with stability in the pH range of 4-8 and temperatures from 4 to 40 °C. K⁺, Na⁺, Ca²⁺, Mg²⁺, Mn²⁺, Hg²⁺, and Al³⁺ showed varying degrees of activation on the enzyme. At the end of the 8-week trial, the addition of OpCht significantly increased the height of intestinal villi and the thickness of the muscular layer, leading to significantly weight in the treated groups. The alleviation of intestinal inflammation also resulted in an increased survival rate (SR) of O. potamophila. High concentration treatment groups (2, 4 μg/g) showed significantly elevated digestive enzyme activities, as well as increased antioxidant enzyme activities and immune parameters. These results demonstrate that the P. pastoris expression system has successfully produced the chitinase OpCht from O. potamophila, and the addition of a certain concentration of OpCht can promote fish growth and enhance immune functions, offering a promising enzyme preparation for the aquaculture industry.

In orthopedic practice, accommodating irregular defects caused by trauma or surgery with traditional preformed bone graft substitutes is often challenging. As a result, injectable hydrogels with seed cells have garnered significant interest in bone repair due to their adaptability and minimally invasive properties. However, they cannot simultaneously achieve injectability and mechanical properties, providing a biophysical and biochemical environment for cell support. In this study, a novel injectable hydrogel system (OA hydrogel) loaded with aspirin and bone mesenchymal stem cells (BMSCs) was developed to enhance osteogenesis and immune regulation in small irregular bone defects. OA hydrogels possessed self-healing and shear-thinning properties due to dynamic/covalent hydrazone bonds between aldehyde-modified hyaluronic acid methacrylate (ADH-HAMA) and oxidized hyaluronic acid (OHA). By photopolymerization of the enclosed HAMA, the OA^DC hydrogel was further reinforced, making it more suitable for cell proliferation. In vitro, composite hydrogels improved the osteogenic differentiation of BMSCs. Additionally, it promoted the M2 polarization of human monocytic leukemia (THP-1) cells. In vivo, the synergistic effect of acetylsalicylic acid (ASA) and BMSCs encapsulated within the OA^DC hydrogel promoted new bone formation in rat calvaria through increased recruitment and polarization of M2 macrophages. These findings underscore the significant promise of hydrogels for bone tissue engineering applications.

In this work, by using molecular dynamics simulations, we elucidate the effect of sulfation substitution on the stability of the curdlan triple helix structure. The simulation results indicate that the stability of the triple helix structure is significantly influenced by the sites of sulfation substitution. The substitution at the O₂ site directly disrupts the hydrogen bonding network between the triple helix chains, significantly destroying the triple helix conformation. When substitutions occur at both the O₄ and O₆ sites simultaneously (O_4,6), the electrostatic repulsion between numerous sulfate groups introduces considerable energy perturbation to the triple helix, leading to alterations in the glucan chain conformation and consequent destabilization of the triple helix structure. Meanwhile, we find that even if the sulfation substitution is performed at the same substitution sites, the difference in the degree of substitution also has an impact on the triple helix stability. The resistance of the triple helix to sulfation substitution at O₂ is weak, and low degree of substitution can lead to the unwinding of the triple helix. However, it demonstrates higher resistance to substitution at O_4,6 where only higher degree of substitution results in triple helix destabilization.

In recent years, polysaccharides extracted from berries have received great attention due to their various bioactivities. However, the preparation and application of berry polysaccharides have been greatly limited due to the lack of efficient extraction techniques, unclear structure-activity relationships, and ambiguous functional mechanisms. This review discusses the technological progress in solvent extraction, assisted extraction, critical extraction, and combination extraction. The structure-activity relationship and functional mechanism (antioxidation, hypoglycemic, immunoregulation etc.) of berry polysaccharides are reviewed. After systematic exploration, we believe that industrial production is more suitable for using efficient and low-cost extraction methods, such as ultrasonic assisted extraction and microwave assisted extraction. And some of the bioactivities (antioxidant activity, hypoglycemic activity, etc.) of berry polysaccharides are closely related to their structure (molecular weight, monosaccharide composition, branching structure, etc.). Besides, berry polysaccharides exhibit bioactivities by regulating enzyme activity, cellular metabolism, gene expression, and other pathways to exert their effects on the body. These findings indicate the potential of berry polysaccharides as functional foods and drugs. This paper will contribute to the preparation, bioactivity research, and application of berry polysaccharides.

The development of sustainable agriculture has boosted an increase in demand for biodegradable and multifunctional biomass-based mulch films. Herein, a sort of eco-friendly and multifunctional soybean protein isolates crosslinked gelatins (SPI-c-Gel) composite mulch films were elaborately designed through the Schiff base reaction. The formation of physical entanglement and chemical cross-linking between the molecular chains of SPI and Gel could effectively dissipate the loading energy and thereby strengthen the resistance of the composite mulch films to water penetration. Specifically, the maximum tensile strain and tensile stress were observed to increase from 4.05 MPa at 73.3 % for pure SPI film to 14.7 MPa at 151 % for optimized SPI-c-Gel_0.3 mulch film. The swelling rate in water declined from 280 % for pure SPI film to 141 % for SPI-c-Gel_0.3 composite film. Furthermore, the fabricated composite mulch film exhibited satisfied water retention, urea slow-release properties, and biodegradability. The application experiments of SPI-c-Gel_0.3 composite mulch have shown that the seeds grew faster when cabbage seeds were covered by such mulch film during seed germination. Our findings provide a novel strategy for regulating the physical and chemical properties of biopolymer-based multifunctional mulch films, which may be employed to promote the development of sustainable agriculture.