Structural Changes in Milled Wood Lignin (MWL) of Chinese Quince (Chaenomeles sinensis) Fruit Subjected to Subcritical Water Treatment.

Subcritical water treatment has received considerable attention due to its cost effectiveness and environmentally friendly properties. In this investigation, Chinese quince fruits were submitted to subcritical water treatment (130, 150, and 170 °C), and the influence of treatments on the structure of milled wood lignin (MWL) was evaluated. Structural properties of these lignin samples (UL, L130, L150, and L170) were investigated by high-performance anion exchange chromatography (HPAEC), FT-IR, gel permeation chromatography (GPC), TGA, pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), 2D-Heteronculear Single Quantum Coherence (HSQC) -NMR, and 31P-NMR. The carbohydrate analysis showed that xylose in the samples increased significantly with higher temperature, and according to molecular weight and thermal analysis, the MWLs of the pretreated residues have higher thermal stability with increased molecular weight. The spectra of 2D-NMR and 31P-NMR demonstrated that the chemical linkages in the MWLs were mainly ß-O-4' ether bonds, ß-5' and ß-ß', and the units were principally G- S- H- type with small amounts of ferulic acids; these results are consistent with the results of Py-GC/MS analysis. It is believed that understanding the structural changes in MWL caused by subcritical water treatment will contribute to understanding the mechanism of subcritical water extraction, which in turn will provide a theoretical basis for developing the technology of subcritical water extraction.

Self-Folding Hybrid Graphene Skin for 3D Biosensing.

Biological samples such as cells have complex three-dimensional (3D) spatio-molecular profiles and often feature soft and irregular surfaces. Conventional biosensors are based largely on 2D and rigid substrates, which have limited contact area with the entirety of the surface of biological samples making it challenging to obtain 3D spatially resolved spectroscopic information, especially in a label-free manner. Here, we report an ultrathin, flexible skinlike biosensing platform that is capable of conformally wrapping a soft or irregularly shaped 3D biological sample such as a cancer cell or a pollen grain, and therefore enables 3D label-free spatially resolved molecular spectroscopy via surface-enhanced Raman spectroscopy (SERS). Our platform features an ultrathin thermally responsive poly( N-isopropylacrylamide)-graphene-nanoparticle hybrid skin that can be triggered to self-fold and wrap around 3D micro-objects in a conformal manner due to its superior flexibility. We highlight the utility of this 3D biosensing platform by spatially mapping the 3D molecular signatures of a variety of microparticles including silica microspheres, spiky pollen grains, and human breast cancer cells.

Mechanical Properties and Failure of Biopolymers: Atomistic Reactions to Macroscale Response.

The behavior of chemical bonding under various mechanical loadings is an intriguing mechanochemical property of biological materials, and the property plays a critical role in determining their deformation and failure mechanisms. Because of their astonishing mechanical properties and roles in constituting the basis of a variety of physiologically relevant materials, biological protein materials have been intensively studied. Understanding the relation between chemical bond networks (structures) and their mechanical properties offers great possibilities to enable new materials design in nanotechnology and new medical treatments for human diseases. Here we focus on how the chemical bonds in biological systems affect mechanical properties and how they change during mechanical deformation and failure. Three representative cases of biomaterials related to the human diseases are discussed in case studies, including: amyloids, intermediate filaments, and collagen, each describing mechanochemical features and how they relate to the pathological conditions at multiple scales.

Revealing the structural changes of lignin in Chinese quince (Chaenomeles sinensis) fruit as it matures.

Chinese quince fruits (Chaenomeles sinensis) contain substantial amounts of lignin; however, the exact structure of lignin remains to be investigated. In this study, milled wood lignins (Milled wood lignin (MWL)-1, MWL-2, MWL-3, MWL-4, MWL-5, and MWL-6) were extracted from fruits harvested once a month from May to October 2019 to investigate their structural evolution during fruit growth. The samples were characterized via High-performance anion exchange chromatography (HPAEC), Fourier transform-infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), thermogravimetric (TGA), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and NMR (2D-heteronuclear single quantum coherence (HSQC) and 31P). The MWL samples in all fruit growth stages were GS-type lignin and lignin core undergoing minimal alterations during fruit development. The predominant linkage in the lignin structure was ß-O-4', followed by ß-ß' and ß-5'. Galactose and glucose were the main monosaccharides associated with MWL. In MWL-6, the lignin exhibited the highest homogeneity and thermal stability. As the fruit matured, a gradual increase in the ß-O-4' proportion and the ratio of S/G was observed. The results provide comprehensive characterization of the cell wall lignin of quince fruit as it matures. This study could inspire innovative applications of quince fruit lignin and provide the optimal harvest time for lignin utilization.

Chemical and structural transformations of lignin in sesame seed hull during roasting.

To investigate the mechanism of lignin degradation during sesame roasting, structural transformations of milled wood lignin (MWL) from sesame seed hull samples roasted at 190-250 °C for 30 min were investigated. The findings revealed that, with increasing temperature, the degradation extent of carbohydrates from lignin carbohydrate complex in the fractions deepened, which reduced total sugar content (from 8.59 % to 0.45 %). Compared to that of the original sesame seed hull lignin (LSSH), the molecular weight of MWL fractions showed a tendency to decline (Mw 4377-2235 Da) with the rise of roasting temperature (210-250 °C). During roasting, lignins in the sesame seed hull underwent degradation and condensation. Due to demethoxylation, the H-type lignin proportion increased from 2.7 % to 26.1 %. Compared to G- and C-type lignin, S-type lignin was more stable. The ß-O-4 linkages decreased from 5.8 to 1.2/100 Ar due to CO bond breaking, and ß-ß linkages from 26.3 to 9.6/100 Ar decreased due to condensation of CC. As the roasting temperature increased, more chemical bonds between lignin structural units were broken, resulting in the generation of more phenolic hydroxyl groups (1.80-2.53 mmol/g). This study helps to elucidate the contribution of lignin degradation during roasting to the oxidative stability of sesame oil.

Effects of different precursors on the structure of lignin-based biochar and its ability to adsorb benzopyrene from sesame oil.

Agricultural by-products of sesame are promising bioresources in food processing. This study extracted lignin from the by-products of sesame oil production, namely, the capsules and straw of black and white sesame. Using acid, alkali, and ethanol methods, 12 distinct lignins were obtained to prepare biochar, aiming to investigate both the structural characteristics of lignin-based biochar (LBB) and its ability to remove benzo[a]pyrene (BaP) from sesame oil. The results showed that white sesame straw was the most suitable raw material for preparing biochar. In terms of the preparation method, acid-extracted lignin biochar was more effective in removing BaP than alkaline or ethanol methods. Notably, WS-1LB (white sesame straw acid-extracted lignin biochar) exhibited the highest BaP adsorption efficiency (91.44 %) and the maximum specific surface area (1065.8187 m2/g), characterized by porous structures. The pseudo 2nd and Freundlich models were found to be the best fit for the adsorption kinetics and isotherms of BaP on LBB, respectively, suggesting that a multilayer adsorption process was dominant. The high adsorption of LBB mainly resulted from pore filling. This study provides an economical and highly efficient biochar adsorbent for the removal of BaP in oil.

Comparison of methods for activating sesame stalk lignin biochar for removing benzo[a]pyrene from sesame oil.

In this study, three activators and two activation methods were employed to activate sesame lignin-based biochar. The biochar samples were comprehensively characterized, their abilities to adsorb benzo[a]pyrene (BaP) from sesame oil were assessed, and the mechanism was analyzed. The results showed that the biochar obtained by one-step activation was more effective in removing BaP from sesame oil than the biochar produced by two-step activation. Among them, the biochar generated by one-step activation with ZnCl2 as the activator had the largest specific surface area (1068.8776 m3/g), and the richest mesoporous structure (0.7891 m3/g); it removed 90.53 % of BaP from sesame oil. BaP was mainly adsorbed by the mesopores of biochar. Mechanistically, pore-filling, π-π conjugations, hydrogen bonding, and n-π interactions were involved. The adsorption was spontaneous and heat-absorbing. In conclusion, the preparation of sesame lignin biochar using one-step activation with ZnCl2 as the activator was found to be the best for removing BaP from sesame oil. This biochar may be an economical adsorbent for the industrial removal of BaP from sesame oil.

Structural characterization of lignin-carbohydrate complexes from Chinese quince fruits extracted after enzymatic hydrolysis pretreatment.

Chinese quince fruit (CQF) contains abundant pectin; however, the pectin cannot be efficiently separated by conventional approaches because of strong lignin-carbohydrate complexes (LCC). In this study, to elucidate the structural characteristics of the original LCC formed by lignin and pectin in CQF, single and multiple enzymatic hydrolysis pretreatments were innovatively performed, and the resulting LCC preparations were comprehensively characterized using a series of techniques. The enzymatic hydrolysis pretreatments significantly increase the LCC yield, releasing LCC fractions with low molecular weights (Mw = 4660-8288 Da). LCC-4, isolated by pretreatment with cellulase plus xylanase, had the highest galacturonic acid content (15.5 %), followed by LCC-2 (isolated by xylanase pretreatment) of 14.0 %. In CQF, lignin develops lignin-carbohydrate (LC) bonds with pectin to form LCC, with phenyl-glycoside bond being the dominant linkage. Although the pectinase pretreatment reduced the pectin content, signals of the LC linkages in the 2D-HSQC spectra were enhanced. LCC-4 could be considered as the most representative of the original LCC in CQF due to its high pectin content and multiple LCC signals in the 2D-HSQC spectrum. The structural understanding of the original LCC in CQF will lay a foundation for designing appropriate methods for extracting pectin from CQF.

Structural variation of lignin-carbohydrate complexes (LCC) in Chinese quince (Chaenomeles sinensis) fruit as it ripens.

Chinese quince (Chaenomeles sinensis) fruits are rich in lignin, and too sour, astringent and woody to be eaten raw. More than 50 % of lignin in plant cell walls is covalently associated with carbohydrates to form lignin-carbohydrate complexes (LCC). In this study, LCC preparations were extracted from fruits harvested on the 15th day of the month from May-October 2019. A variety of chemical and instrumental analytical approaches were used to characterize the LCC fractions, including HPAEC, TGA, GPC, FT-IR, and 2D HSQC NMR. Antioxidant activities were evaluated by DPPH radical scavenging assays. Results showed that the LCC fractions from October fruits had better thermal stability and homogeneity. NMR results revealed that the lignin-lignin linkages in LCC-AcOH preparations included ß-O-4', ß-ß' and ß-5', but ß-5' linkages were not present in LCC preparations. And the NMR signals of carbohydrate confirmed the presence of lignin-pectin complexes, which was consistent with sugar analysis. All LCC preparations showed good antioxidant activity, among which Björkman LCC from October fruits showed best. This study will facilitate understanding the chemical bonds of LCC macromolecules in the plant cell wall. More specifically, it provides information critical for specific industrial applications of quince fruits.

Construction of an enzymatic shuttling compartment based on reverse micellar for bamboo biomass hydrolysis in ionic liquids.

The enzymatic saccharification of regenerated lignocellulose must occur separately due to the toxicity of ionic liquids to cellulase. Therefore, it is important to develop a biocompatible IL-cellulase system which effectively achieves activation and saccharification of lignocellulose. For this purpose, a dual-phase "enzyme-shuttling compartment" was constructed in this study. Tween 80 was found to form reverse micelles in the isooctane-IL two-liquid phase, acting as a microenvironment that maintains the energetic conformation of the reactive cellulase. The activated bamboo biomass was enzymatically hydrolyzed in 20% (w/v) 1-ethyl-3-methylimidazolium dimethyl phosphate and 50 mM citrate buffer at 50 °C, achieving a high total reducing sugar yield of 71.2% and maintaining an enzymatic activity of 91.2% after 24 h. Thus, an efficient system with the simultaneous activation and saccharification of natural biomass was successfully developed in a one-pot procedure at low temperatures, ensuring large-scale biomass conversion into biofuels and biological products.

Structural characterization of lignin and lignin-carbohydrate complex (LCC) of sesame hull.

In the present study, lignin and lignin-carbohydrate complex (LCC) constituting the cell wall structure of sesame hulls were investigated to explore novel techniques of dehulling. Milled wood lignin (MWL), Björkman LCC, and acid-soluble LCC (LCC-AcOH) were extracted from sesame hulls and characterized by carbohydrate composition analysis, molecular weight analysis, UV-vis spectroscopy, FT-IR, thermal analysis, Py-GC/MS, 2D HSQC NMR, and 31P NMR. The results showed that rhamnose accounted for the largest proportion of the lignin and LCC fractions, followed by glucose. Björkman LCC had the largest molecular weight, MWL had the smallest molecular weight, and LCC-AcOH had the largest polydispersity index. The lignin of sesame hulls consisted of syringyl (S), guaiacyl (G), p-hydroxyphenyl (H), and caffeyl alcohol (C) units. The most abundant monomer was guaiacyl (G), followed by caffeyl alcohol (C). C-type lignin is a new type of lignin that is different from the three traditional lignin monomers. The major lignin-linked bonds in the MWL and LCC-AcOH were ß-O-4' and ß-ß', and ß-5' bonds were present in the Björkman LCC. The major LCC chemical bonds in the three fractions were PhGly. These findings will provide the factual basis for exploring different dehulling methods to enhance the quality of sesame products.

Sequential aqueous acetone fractionation and characterization of Brauns native lignin separated from Chinese quince fruit.

Lignin, especially Brauns native lignin (BNL), from Chinese quince (Chaenomeles sinensis) fruit represents a potential source of natural antioxidants. However, the highly inhomogeneous structure and the carbohydrate impurity reduce the antioxidant properties of BNL. Accordingly, a sequential aqueous acetone fractionation was used to prepare pure lignin fractions with homogeneous molecular structures; these fractions showed strong antioxidant properties. Analytical results showed that the yields of F50% and F60% exceeded 20% (i.e., 20.6% and 24.1%, respectively). The sugar impurities in BNL were mainly retained in the F30% and F40% fractions. For all fractions, molecular weight increased as the acetone concentration increased. The results from 2D HSQC NMR and 31P NMR indicated that the number of lignin linkages (ß-O-4', ß-ß' and ß-5') and functional groups (S-OH, G-OH, H-OH, and COOH) of these fractions varied with their molecular weights. Antioxidant assays showed that F40%, F50% and F60% had higher antioxidant properties than BNL. Overall, the study provides a simple, environmentally friendly fractionation method to prepare lignin with various structural features and strong antioxidant properties from Chinese quince fruit. These lignin fractions have promising application in some fields with high value, such as antioxidants production, biomaterials, packaging materials, and drug delivery and so on.

Structural changes of lignin-carbohydrate complexes (LCCs) from Chinese quince fruits during the sequential fractionation of pectic and hemicellulosic polysaccharides.

Chinese quince (Chaenomeles sinensis) fruits offer a potential source of pectin and hemicellulose. However, the existence of lignin-carbohydrate complexes (LCCs) can negatively impact the extraction of pectin and hemicellulose. In this work, LCCs were sequentially fractionated from Chinese quince during the removal of pectin and hemicellulose. The structures of LCCs were characterized by HPAEC, FT-IR, GPC, Py-GC/MS, TGA and 2D HSQC NMR. The results showed that the carbohydrate content and molecular weight of LCCs was found to be changed significantly after the removal of hemicellulose (KSH). The lignin in Björkman LCCs was found to be linked mainly to galactan and fructan, whereas the lignin LCC-AcOHs was found to be linked mainly to arabinan after the removal of KSH. The isolation of carbonate-soluble pectin (NSP) increased thermal stability of Björkman LCC fraction, however, the isolation of chelator-soluble pectin (CSP) increased the thermal stability of LCC-AcOHs. The S/G ratios of LCC-AcOHs increased and large amounts of S-type lignin released during sequential fractionation of pectin and hemicellulose. These results will be beneficial for understanding the mechanisms of pectin and hemicellulose isolation, thereby facilitating the potential application of Chinese quince as a valuable natural resource for food and other industries.

Electrospinning Piezoelectric Fibers for Biocompatible Devices.

The field of nanotechnology has been gaining great success due to its potential in developing new generations of nanoscale materials with unprecedented properties and enhanced biological responses. This is particularly exciting using nanofibers, as their mechanical and topographic characteristics can approach those found in naturally occurring biological materials. Electrospinning is a key technique to manufacture ultrafine fibers and fiber meshes with multifunctional features, such as piezoelectricity, to be available on a smaller length scale, thus comparable to subcellular scale, which makes their use increasingly appealing for biomedical applications. These include biocompatible fiber-based devices as smart scaffolds, biosensors, energy harvesters, and nanogenerators for the human body. This paper provides a comprehensive review of current studies focused on the fabrication of ultrafine polymeric and ceramic piezoelectric fibers specifically designed for, or with the potential to be translated toward, biomedical applications. It provides an applicative and technical overview of the biocompatible piezoelectric fibers, with actual and potential applications, an understanding of the electrospinning process, and the properties of nanostructured fibrous materials, including the available modeling approaches. Ultimately, this review aims at enabling a future vision on the impact of these nanomaterials as stimuli-responsive devices in the human body.

Structural features and antioxidant activities of Chinese quince (Chaenomeles sinensis) fruits lignin during auto-catalyzed ethanol organosolv pretreatment.

Chinese quince fruits (Chaenomeles sinensis) have an abundance of lignins with antioxidant activities. To facilitate the utilization of Chinese quince fruits, lignin was isolated from it by auto-catalyzed ethanol organosolv pretreatment. The effects of three processing conditions (temperature, time, and ethanol concentration) on yield, structural features and antioxidant activities of the auto-catalyzed ethanol organosolv lignin samples were assessed individually. Results showed the pretreatment temperature was the most significant factor; it affected the molecular weight, S/G ratio, number of ß-O-4' linkages, thermal stability, and antioxidant activities of lignin samples. According to the GPC analyses, the molecular weight of lignin samples had a negative correlation with pretreatment temperature. 2D-HSQC NMR and Py-GC/MS results revealed that the S/G ratios of lignin samples increased with temperature, while total phenolic hydroxyl content of lignin samples decreased. The structural characterization clearly indicated that the various pretreatment conditions affected the structures of organosolv lignin, which further resulted in differences in the antioxidant activities of the lignin samples. These results can be helpful for controlling and optimizing delignification during auto-catalyzed ethanol organosolv pretreatment, and they provide theoretical support for the potential applications of Chinese quince fruits lignin as a natural antioxidant in the food industry.

Natural hydrogel in American lobster: A soft armor with high toughness and strength.

Homarus americanus, known as American lobster, is fully covered by its exoskeleton composed of rigid cuticles and soft membranes. These soft membranes are mainly located at the joints and abdomen to connect the rigid cuticles and greatly contribute to the agility of the lobster in swimming and preying. Herein, we show that the soft membrane from American lobster is a natural hydrogel (90% water) with exceptionally high toughness (up to 24.98 MJ/m3) and strength (up to 23.36 MPa), and is very insensitive to cracks. By combining experimental measurements and large-scale computational modeling, we demonstrate that the unique multilayered structure in this membrane, achieved through the ordered arrangement of chitin fibers, plays a crucial role in dissipating energy during rupture and making this membrane tough and damage tolerant. The knowledge learned from the soft membrane of natural lobsters sheds light on designing synthetic soft, yet strong and tough materials for reliable usage under extreme mechanical conditions, including a flexible armor that can provide full-body protection without sacrificing limb mobility. STATEMENT OF SIGNIFICANCE: A body armor to provide protection to people who are at risk of being hurt is only enabled by using a material that is tough and strong enough to prevent mechanical penetration. However, most modern body armors sacrifice limb protection to gain mobility, simply because none of the existing armor materials are flexible enough and they all inhibit movement of the arms and legs. Herein, we focus on the mechanics and mesoscopic structure of American lobsters' soft membrane and explore how such a natural flexible armor is designed to integrate flexibility and toughness. The knowledge learned from this study is useful to design a flexible armor for full-body protection under extreme mechanical conditions.

The hidden structure of human enamel.

Enamel is the hardest and most resilient tissue in the human body. Enamel includes morphologically aligned, parallel, ∼50 nm wide, microns-long nanocrystals, bundled either into 5-µm-wide rods or their space-filling interrod. The orientation of enamel crystals, however, is poorly understood. Here we show that the crystalline c-axes are homogenously oriented in interrod crystals across most of the enamel layer thickness. Within each rod crystals are not co-oriented with one another or with the long axis of the rod, as previously assumed: the c-axes of adjacent nanocrystals are most frequently mis-oriented by 1°-30°, and this orientation within each rod gradually changes, with an overall angle spread that is never zero, but varies between 30°-90° within one rod. Molecular dynamics simulations demonstrate that the observed mis-orientations of adjacent crystals induce crack deflection. This toughening mechanism contributes to the unique resilience of enamel, which lasts a lifetime under extreme physical and chemical challenges.

Structural characterization of Chinese quince fruit lignin pretreated with enzymatic hydrolysis.

Lignin is an increasingly valuable raw material for industrial, pharmaceutical and the food industries; natural antioxidants are also being used more and more widely. The Chinese quince fruits have an abundance of lignins with antioxidant properties; however, the lignins cannot be isolated by the methods conventionally used on other sources (e.g., wood, straw). In this investigation, multi-enzymatic hydrolytic pretreatments were used to isolate lignins from Chinese quince fruit, and the structures of these multi-enzyme mixture lignin (EML) fractions were then analyzed and compared with conventional cellulolytic enzyme lignin (CEL). EML fractions are structurally similar to CEL fractions except for an increased S/G ratio, greater number of ß-O-4 linkages, higher average molecular weight and decreased thermal stability. The EML-2 fraction in particular seemed most representative of the lignins isolated, and it exhibited the highest antioxidant activity in comparison with CEL and other EML fractions.

Predicting rates of in vivo degradation of recombinant spider silk proteins.

Developing fundamental tools and insight into biomaterial designs for predictive functional outcomes remains critical for the field. Silk is a promising candidate as a biomaterial for tissue engineering scaffolds, particularly where high mechanical loads or slow rates of degradation are desirable. Although bioinspired synthetic spider silks are feasible biomaterials for this purpose, insight into how well the degradation rate can be programmed by fine tuning the sequence remains to be determined. Here we integrated experimental approaches and computational modelling to investigate the degradation of two bioengineered spider silk block copolymers, H(AB)2 and H(AB)12 , which were designed based on the consensus domains of Nephila clavipes dragline silk. The effect of protein chain length and secondary structure on degradation was analysed in vivo. The degradation rate of H(AB)12 , the silk with longer chain length/higher molecular weight, and higher crystallinity, was slower when compared to H(AB)2 . Using full atomistic modelling, it was determined that the faster degradation of H(AB)2 was due to the lower folded molecular structure of the silk and the greater accessibility to solvent. Comparison of the specific surface areas of proteins via modelling showed that higher exposure of random coil and lower exposure of ordered domains in H(AB)2 led to the more reactive silk with a higher degradation rate when compared with H(AB)12 , as validated by the experimental results. The study, based on two simple silk designs demonstrated that the control of sequence can lead to programmable degradation rates for these biomaterials, providing a suitable model system with which to study variables in protein polymer design to predict degradation rates in vivo. This approach should reduce the use of animal screening, while also accelerating translation of such biomaterials for repair and regenerative systems. Copyright © 2016 John Wiley & Sons, Ltd.

Structural elucidation of lignin-carbohydrate complexes (LCCs) from Chinese quince (Chaenomeles sinensis) fruit.

The lignin-carbohydrate complexes (LCCs) of the mesocarp (MS) and near the endocarp (NE) of Chinese quince (Chaenomeles sinensis) fruits were analyzed using three different methods of fractioning: milled wood lignin (MWL), LCC extracted from crude MWL with acetic acid (LCC-AcOH), and Bjorkman LCC. The MWL and LCC fractions were characterized by carbohydrate composition analysis, SEC, FT-IR, Py-GC/MS, thermal analysis and 2D HSQC NMR. Notably, large amounts of arabinose and galactose remained in the Björkman LCC fractions suggesting a chemical bond between the lignin and pectin. MWL and LCC-AcOH fractions showed better thermal stability than the Björkman LCC fractions. The structure of MS lignin was similar to that of NE lignin; however, fractions from the different fractionation methods revealed differences. The MWL fractions were rich in benzyl ether and γ-ester linkages, while the Björkman LCC fractions contained phenyl glycoside and γ-ester linkages, and the LCC-AcOH fractions contained phenyl glycoside and benzyl ether linkages. These findings are helpful in understanding the nature of lignin and LCC in Chinese quince fruits and provide a theoretical support for their potential application.