Structure Of Microfibrils Research Articles

Enhanced rates of enzymatic saccharification and catalytic synthesis of biofuel substrates in gelatinized cellulose generated by trifluoroacetic acid

BackgroundThe crystallinity of cellulose is a principal factor limiting the efficient hydrolysis of biomass to fermentable sugars or direct catalytic conversion to biofuel components. We evaluated the impact of TFA-induced gelatinization of crystalline cellulose on enhancement of enzymatic digestion and catalytic conversion to biofuel substrates.ResultsLow-temperature swelling of cotton linter cellulose in TFA at subzero temperatures followed by gentle heating to 55 °C dissolves the microfibril structure and forms composites of crystalline and amorphous gels upon addition of ethanol. The extent of gelatinization of crystalline cellulose was determined by reduction of birefringence in darkfield microscopy, loss of X-ray diffractability, and loss of resistance to acid hydrolysis. Upon freeze-drying, an additional degree of crystallinity returned as mostly cellulose II. Both enzymatic digestion with a commercial cellulase cocktail and maleic acid/AlCl3-catalyzed conversion to 5-hydroxymethylfurfural and levulinic acid were markedly enhanced with the low-temperature swollen cellulose. Only small improvements in rates and extent of hydrolysis and catalytic conversion were achieved upon heating to fully dissolve cellulose.ConclusionsLow-temperature swelling of cellulose in TFA substantially reduces recalcitrance of crystalline cellulose to both enzymatic digestion and catalytic conversion. In a closed system to prevent loss of fluorohydrocarbons, the relative ease of recovery and regeneration of TFA by distillation makes it a potentially useful agent in large-scale deconstruction of biomass, not only for enzymatic depolymerization but also for enhancing rates of catalytic conversion to biofuel components and useful bio-products.

3D collagen fibrillar microstructure guides pancreatic cancer cell phenotype and serves as a critical design parameter for phenotypic models of EMT.

Pancreatic cancer, one of the deadliest cancers, is characterized by high rates of metastasis and intense desmoplasia, both of which are associated with changes in fibrillar type I collagen composition and microstructure. Epithelial to mesenchymal transition (EMT), a critical step of metastasis, also involves a change in extracellular matrix (ECM) context as cells detach from basement membrane (BM) and engage interstitial matrix (IM). The objective of this work was to develop and apply an in-vitro three-dimensional (3D) tumor-ECM model to define how ECM composition and biophysical properties modulate pancreatic cancer EMT. Three established pancreatic ductal adenocarcinoma (PDAC) lines were embedded within 3D matrices prepared with type I collagen Oligomer (IM) at various fibril densities to control matrix stiffness or Oligomer and Matrigel combined at various ratios while maintaining constant matrix stiffness. Evaluation of cell morphology and protein expression at both the cellular- and population-levels revealed a spectrum of matrix-driven EMT phenotypes that were dependent on ECM composition and architecture as well as initial PDAC phenotype. In general, exposure to fibrillar IM was sufficient to drive EMT, with cells displaying spindle-shaped morphology and mesenchymal markers, and non-fibrillar BM promoted more epithelial behavior. When cultured within low density Oligomer, only a subpopulation of epithelial BxPC-3 cells displayed EMT while mesenchymal MiaPaCa-2 cells displayed more uniform spindle-shaped morphologies and mesenchymal marker expression. Interestingly, as IM fibril density increased, associated changes in spatial constraints and matrix stiffness resulted in all PDAC lines growing as tight clusters; however mesenchymal marker expression was maintained. Collectively, the comparison of these results to other in-vitro tumor models highlights the role of IM fibril microstructure in guiding EMT heterogeneity and showcases the potential of standardized 3D matrices such as Oligomer to serve as robust platforms for mechanistic study of metastasis and creation of predictive drug screening models.

Fluid in the tissue channels of vascular adventitia investigated by AFM and TEM.

Tissue channels as a part of microcirculation system have been proposed over three decades, playing an important role in fluid transportation as reported. Adventitia of inferior vena cava (IVC) is a typical hierarchical porous media with abundant tissue channels. Its fluid transportation behaviors attract massive research interest. However, the mechanism of the driving force and microstructure was lack of deep research. This study was to investigate the microstructural basis of fluid transportation within inferior vena cava (IVC). Rat IVC samples were extracted and fixed on a gelatin substrate. Four samples were randomly used as 4 cases: Case 1 with AFM loading and the fluorescent tracer adding; Case 2 with fluorescent tracer adding only; Case 3 with AFM loading only as the control group; Case 4 with no treatment. The movement of fluorescent tracer was observed by two-photon fluorescent microscope and analyzed by self-made Matlab program. The microscopic structure was characterized by high resolution TEM. The fluorescent tracer in Case 1 exhibited faster and longer transportation comparing to other cases, while in Case 2 diffused normally following Fick's law. Case 3 with only AFM loading demonstrated that collagen bundles twisting along the fluid orientation, while the bundles in Case 4 with no treatment were straggling. The brush-like macromolecule structure of collagen microfibril was found on the bundle surfaces under TEM. Transportation within loose connective tissues is observed ex vivo. AFM loading, as the mechanical stimulation resemblance to muscle constrictions and blood pulsations, can facilitate the transportation as the driving force. The brush-like glycosaminoglycan macromolecules on the surfaces of the collagen bundles can be considered as a type of hierarchical porous media, which might form the transport pathway for fluids. The possible mechanism was conducted regarding the conformation of the superficial macromolecule brushes.

Effect of Fumed SiO2 on Pore Formation Mechanism and Various Performances of β-iPP Microporous Membrane Used for Lithium-ion Battery Separator

In this work, four samples containing different contents of fumed SiO2 were prepared to improve the pore size distribution and various properties of β nucleated isotatic polypropylene (β-iPP) biaxial membrane used for lithium-ion battery separator. The wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) results show that the fumed SiO2 promotes the formation of β-crystal slightly and narrows down the thickness distribution of β-lamellae; meanwhile, evenly distributed SiO2 within β-iPP can be inspected by scanning electron microscopy (SEM). Moreover, further detailed characterization of morphological evolutions during biaxial stretching by tensile testing and SEM manifests that SiO2 can strengthen β-iPP and make the samples deform more homogeneously, resulting in a gradually elaborate and finer oriented microfibril structure after longitudinal stretching, in which more uniform defects distribute between fibrils and restrain the formation of coarse fibrils effectively. Therefore, more superior microporous structure emerges with the addition of SiO2, accompanied by narrower pore size distribution and better connectivity between microvoids, which is confirmed by mercury porosimeter and diminished Gurley value. Moreover, the lower thermal shrinkage, decreased shrinkage rate and suppressed porosity reduction indicate that fumed SiO2 improves thermal and dimensional stability of membrane dramatically. Furthermore, due to the excellent wettability of SiO2 with electrolyte, the microporous membranes doped with SiO2 have higher electrolyte uptake, even after heat treatment at elevated temperature.

Bacterial Cellulose Ionogels as Chemosensory Supports.

To fully leverage the advantages of ionic liquids for many applications, it is necessary to immobilize or encapsulate the fluids within an inert, robust, quasi-solid-state format that does not disrupt their many desirable, inherent features. The formation of ionogels represents a promising approach; however, many earlier approaches suffer from solvent/matrix incompatibility, optical opacity, embrittlement, matrix-limited thermal stability, and/or inadequate ionic liquid loading. We offer a solution to these limitations by demonstrating a straightforward and effective strategy toward flexible and durable ionogels comprising bacterial cellulose supports hosting in excess of 99% ionic liquid by total weight. Termed bacterial cellulose ionogels (BCIGs), these gels are prepared using a facile solvent-exchange process equally amenable to water-miscible and water-immiscible ionic liquids. A suite of characterization tools were used to study the preliminary (thermo)physical and structural properties of BCIGs, including no-deuterium nuclear magnetic resonance, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and X-ray diffraction. Our analyses reveal that the weblike structure and high crystallinity of the host bacterial cellulose microfibrils are retained within the BCIG. Notably, not only can BCIGs be tailored in terms of shape, thickness, and choice of ionic liquid, they can also be designed to host virtually any desired active, functional species, including fluorescent probes, nanoparticles (e.g., quantum dots, carbon nanotubes), and gas-capture reagents. In this paper, we also present results for fluorescent designer BCIG chemosensor films responsive to ammonia or hydrogen sulfide vapors on the basis of incorporating selective fluorogenic probes within the ionogels. Additionally, a thermometric BCIG hosting the excimer-forming fluorophore 1,3-bis(1-pyrenyl)propane was devised which exhibited a ratiometric (two-color) fluorescence output that responded precisely to changes in local temperature. The ionogel approach introduced here is simple and has broad generality, offering intriguing potential in (bio)analytical sensing, catalysis, membrane separations, electrochemistry, energy storage devices, and flexible electronics and displays.

Chitin and chitosan preparation from shrimp shells Penaeus monodon and its human ovarian cancer cell line, PA-1

In the present study, chitin and chitosan preparation from shrimp shells Penaeus mondon and its ovarian cancer cell line (PA-1). FTIR spectrum sharp absorption peak at 1655cm−1 is assigned to ketone C=O (α) unsaturated with chitosan. X-ray diffraction showed the presence of chitin and chitosan were strongest peak at 18.91° (β) and 29.75° (α) characters. SEM observations of chitin and chitosan surface morphologies of P. monodon showed that microfibril and porous structures. Anticancer activity of chitin and chitosan against human ovarian cancer cell line showed that chitosan an exhibited notable higher activity than chitin. Anticancer activity of aquacultural waste of shrimp shells mediated chitosan, which was proved to be good novel pharmaceutical industries.

Electric-Field-Oriented Growth of Long Hair-Like Silica Microfibrils and Derived Functional Monolithic Solids.

Controlled self-assembly using molecules/nanoparticles as building block materials represents an important approach for nanofabrication. We present a "bottom-up" fabrication approach to first grow a new class of inorganic (silica) long hair-like microfibrils or microwires and then to form monolithic solid pellet that contains parallel arrays of bundled microfibrils with a controlled orientation. During the sol-gel solution processing, reactive precursor species are utilized as molecular "building blocks" for the field-directed assembly growth of microfibrils driven by an electric field of pulsed direct current (dc) with controlled frequency. We have demonstrated a novel reactive electrofibrilation process that combines an external field with a solid-phase nucleation and growth process which in principle has no limitation on the type of reactions (such as the one here that involves sol-gel reaction chemistry) and on materials compositions (such as the example silica oxide), thus will enable bulk production of long microfibrils of wide variety of inorganic materials (other oxides or metals). Furthermore, we have fabricated uniquely architectured monolithic solid materials containing aligned microfibrils by "wet press" of the in-situ grown microfibril structure in the electric field. The consolidated monolithic slabs (1 cm × 1 cm × 3 mm) have shown anisotropic properties and desirable retention of DNA molecule fragments, thus, could serve as a platform stationary-phase materials for future development of capillary electrochromatography for biomolecule separations. Electrical field-guided self-assembly is an effective approach in producing long (hair-like) ceramic microfibrils, which can be further used in consolidation fabrication of oriented structured ceramic monoliths with potential for capillary electrophoretic chromatography and other separations applications. This original work was recorded through a patent application to understand the fibril formation mechanism and its process.

Comparative characteristics of TEMPO-oxidized cellulose nanofibers and resulting nanopapers from bamboo, softwood, and hardwood pulps

Bamboo, softwood, and hardwood pulp fibers were used as starting materials to prepare TEMPO-oxidized nanofibrillated cellulose (TO-NFC) dispersions. The resulting TO-NFC dispersions were then used to fabricate cellulose nanopapers and to coat poly(lactic acid) (PLA) films. The chemical and morphological characteristics of the dispersions together with the physical properties of the resultant nanopaper and PLA films were systematically compared. The maximum degree of oxidation was achieved for the bamboo pulp fiber. Transmission electron microscopy micrographs revealed that the oxidized pulp fibers were successfully disintegrated into cellulose nanofibrils with an average width of 5–6 nm. However, bamboo-derived TO-NFC was more densely entangled and crimped, with a heterogeneous distribution in width. It was further revealed that morphologies of the obtained TO-NFC may arise from the organizational structure of microfibrils in the cellulose fibers rather than the presence of hemicelluloses or the pulping process. The PLA films coated with a thin layer of TO-NFC from the bamboo pulp exhibited the highest oxygen-barrier property, which was even slightly higher than commercial ethylene–vinyl alcohol copolymer film, known for its high oxygen-barrier functionality.

Structure of cellulose microfibrils in mature cotton fibres

The structure of cellulose microfibrils in mature cotton fibres from three varieties – Gossypium hirsutum, G. barbadense and G. arboreum – has been investigated by a multi-technique approach combining small angle scattering techniques with spectroscopy and diffraction. Cellulose microfibrils present a Iβ-rich crystalline structure with limited surface disorder. Small angle scattering (SAXS and SANS) data have been successfully fitted using a core-shell model and the results obtained indicate that the cellulose microfibrils, formed by the association of 2–3 elementary fibrils, are composed of a ca. 2nm impermeable crystalline core, surrounded by a partially hydrated paracrystalline shell, with overall cross-sections of ca. 3.6–4.7nm. Different low levels of cell wall matrix components have a strong impact on the microfibril architecture and enable moisture penetration upon hydration. Furthermore, the higher amounts of non-cellulosic components in G. barbadense result in a less dense packing of cellulose microfibrils and increased solvent accessibility.

Observation of asphalt binder microstructure with ESEM.

The observation of asphalt binder with the environmental scanning electron microscope (ESEM) has shown the potential to observe asphalt binder microstructure and its evolution with binder aging. A procedure for the induction and identification of the microstructure in asphalt binder was established in this study and included sample preparation and observation parameters. A suitable heat-sampling asphalt binder sample preparation method was determined for the test and several stainless steel and Teflon sample moulds developed, finding that stainless steel was the preferable material. The magnification and ESEM settings conducive to observing the 3D microstructure were determined through a number of observations to be 1000×, although other magnifications could be considered. Both straight run binder (PG 58-28) and an air blown oxidised binder were analysed; their structures being compared for their relative size, abundance and other characteristics, showing a clear evolution in the fibril microstructure. The microstructure took longer to appear for the oxidised binder. It was confirmed that the fibril microstructure corresponded to actual characteristics in the asphalt binder. Additionally, a 'bee' micelle structure was found as a transitional structure in ESEM observation. The test methods in this study will be used for more comprehensive analysis of asphalt binder microstructure.

Deformation and pore formation mechanism under tensile loading in isotactic polypropylene

AbstractFour different polypropylene (PP) samples were prepared through isothermally crystallizing at 0 °C (PP‐Q), 80 °C (PP‐80), 100 °C (PP‐100) and 120 °C (PP‐120). The results of differential scanning calorimetry, wide‐angle X‐ray diffraction, polarized light microscopy and tensile testing indicate that the spherulite structure gradually improves with increasing isothermal crystallization temperature. Meanwhile, the interface between spherulites becomes more obvious due to the larger dimension and the higher strength of spherulites. Therefore, the trend of interfacial debonding during stretching is enhanced distinctly. In addition, based on the structural characterization of samples at different draw ratios, two completely distinct morphological changes are demonstrated. There are no defects generated after longitudinal stretching within PP‐Q, because intra‐spherulitic deformation predominates, which is caused by the imperfect spherulites of PP‐Q. As a result, no microporous structure is produced after sequential biaxial stretching. And the improvement of the crystalline structure makes interfacial debonding more likely to occur. Therefore, fully developed crazes and cracks disperse between microfibril structures after longitudinal stretching. Furthermore, numerous microporous structures are produced through debonding of fully developed crazes and cracks after sequential biaxial stretching. Meanwhile, the quantity, dimension and uniformity of the microporous structures and the porosity are gradually improved. © 2017 Society of Chemical Industry

Latent TGF-\u03b2 binding protein 2 and 4 have essential overlapping functions in microfibril development

Microfibrils are exracellular matrix components necessary for elastic fiber assembly and for suspending lenses. We previously reported that latent TGF-β binding protein 2 (LTBP-2), a microfibril-associated protein, is required for forming stable microfibril bundles in ciliary zonules. However, it was not understood why Ltbp2 null mice only showed an eye-specific phenotype, whereas LTBP-2 is abundantly expressed in other tissues containing microfibrils in wild type mice. Here, we show that LTBP-4, another microfibril-associated protein, compensates for the loss of LTBP-2 in microfibril formation. Ltbp2/4S double knockout (DKO) mice showed increased lethality due to emphysema, which was much more severe than that found in Ltbp4S null mice. Elastic fibers in the lungs of Ltbp2/4S DKO mice were severely disorganized and fragmented. Cultured mouse embryonic fibroblasts (MEFs) from Ltbp2/4S DKO embryos developed reduced microfibril meshwork in serum-free conditions, whereas the microfibril formation was restored by the addition of either recombinant LTBP-2 or -4. Finally, ectopic expression of LTBP-4 in the whole body restored ciliary zonule microfibril bundles in the eyes of Ltbp2 null mice. These data suggest that LTBP-2 and -4 have critical overlapping functions in forming the robust structure of microfibrils in vitro and in vivo.

Abstract A57: Novel 3D tumor-stromal model highlights the importance of ECM composition and biophysical properties in pancreatic cancer EMT and drug resistance

Abstract Introduction: Epithelial to mesenchymal transition (EMT), where cells detach from basement membrane (BM) and invade interstitial matrix (IM), plays a significant role in tumor metastasis and drug resistance. Mechanobiological mechanisms of such tumor-stroma interactions are poorly understood largely due to inherent limitations of current preclinical tumor models (e.g. 2D cell culture and spheroids). The objective of this work was to apply a novel in-vitro 3D tumor-stromal model to define how extracellular matrix (ECM) composition and biophysical properties modulate EMT. Methods: This work involved pancreatic cancer cells representing different EMT phenotypes (BxPc-3: epithelial; Panc-1: intermediate; MiaPaCa-2: mesenchymal). Matrigel was used to represent BM, while tunable type I collagen Oligomers represented IM. Cells were encapsulated within 3D matrices composed of Matrigel, Oligomer of varied fibril density (matrix stiffness), or Oligomer and Matrigel combined at varied ratios. Cell phenotype was characterized based on morphology and EMT protein immunostaining (i.e., E-cadherin and vimentin). Dose response curves to gemcitabine (standard of care) were used to define relative IC50. ECM microstructure was visualized using confocal reflection microscopy, and matrix stiffness (G') was determined using rheometric oscillatory shear testing. Results: Oligomer enhanced the mesenchymal phenotype with decreasing stiffness (vimentin expression; spindle-shaped cells), while Matrigel downregulated mesenchymal properties and encouraged an epithelial phenotype (E-cadherin expression; rounded, grouped cells). While maintaining vimentin expression in all matrices, Panc-1 and MiaPaCa-2 grew as tight clusters within Matrigel and the highest stiffness Oligomer, where they showed the greatest gemcitabine resistance. BxPc-3 were most sensitive in intermediate stiffness Oligomer where they appeared most proliferative. They also showed relatively high drug resistance in Matrigel and matched-stiffness Oligomer despite each matrix supporting opposite phenotypes. Cells were also cultured within matrices of varied Oligomer:Matrigel ratio to define how BM and IM engagement guides EMT. In matrices with high Oligomer content (>50%), MiaPaCa-2 generated a notably more invasive, mesenchymal phenotype, while BxPc-3 only transitioned to a mesenchymal phenotype in pure Oligomer. Since stiffness and fibril density were similar in the 75:25 and 100:0 ratios, the presence of BM components appears to mediate the phenotypic transition between these matrices. Collectively, these results emphasize the importance of ECM composition and biophysical properties in guiding EMT. Findings suggest that epithelial tumor cells (BxPc-3) may require engagement with a low stiffness IM to undergo EMT and reduce drug sensitivity. For already transitioned cells (Panc-1 and MiaPaCa-2), decreasing stiffness enhances their mesenchymal nature but increases drug sensitivity. Together these observations align with the idea that EMT increases drug resistance, yet challenge the view that increasing matrix stiffness mediates this transition. Also, engagement with both matrix types promotes invasiveness of mesenchymal cells while exposure to BM suppresses EMT of epithelial cells. Finally, Matrigel promotes a drug resistant, epithelial phenotype which highlights its limitations for studying EMT mechanisms. Conclusion: This work represents the first use of type I collagen oligomers for mechanistic study of EMT mechanobiology and provides new insight into how IM fibril microstructure and mechanical properties guide EMT. These results challenge correlations between stromal properties and EMT established using conventional preclinical models and help identify critical parameters for engineering pathophysiologically relevant tumor-stromal models. Citation Format: TJ Puls, Xiaohong Tan, Catherine Whittington, Sherry Voytik-Harbin. Novel 3D tumor-stromal model highlights the importance of ECM composition and biophysical properties in pancreatic cancer EMT and drug resistance. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr A57.

Functional Analysis of Cellulose Synthase (CESA) Protein Class Specificity.

The cellulose synthase complex (CSC) exhibits a 6-fold symmetry and is known as a "rosette." Each CSC is believed to contain between 18 and 24 CESA proteins that each synthesize an individual glucan chain. These chains form the microfibrils that confer the remarkable structural properties of cellulose. At least three different classes of CESA proteins are essential to form the CSC However, while organization of the CSC determines microfibril structure, how individual CESA proteins are organized within the CSC remains unclear. Parts of the plant CESA proteins map sufficiently well onto the bacterial CESA (BcsA) structure, indicating that they are likely to share a common catalytic mechanism. However, plant CESA proteins are much larger than the bacterial BcsA protein, prompting the suggestion that these plant-specific regions are important for interactions between CESA proteins and for conferring CESA class specificity. In this study, we have undertaken a comprehensive analysis of well-defined regions of secondary cell wall CESA proteins, with the aim of defining what distinguishes different CESA proteins and hence what determines the specificity of each CESA class. Our results demonstrate that CESA class specificity extends throughout the protein and not just in the highly variable regions. Furthermore, we find that different CESA isoforms vary greatly in their levels of site specificity and this is likely to be determined by the constraints imposed by their position within the CSC rather than their primary structure.

Understanding of plant cell wall biosynthesis for utilization of lignocellulosic biomass resources

How do plants make cell walls? How can the cell wall biomass be turned into fuel energy? These questions are still unsolved puzzles that have attracted a great deal of interest in scientific community as well as in industrial and political worlds. Different from animal cells, plant cells develop characteristic structures of cell walls, which play crucial roles in planting growth and response to environments. As cell walls accumulate approximately seventy percent of the land pant photosynthesized products on the globe, cell wall biomass is the most abundant renewable resource for production of bioenergy and biomaterials. However, only a small portion (~2%) of the plant cell wall resource has been used by human society so far. More efficient utilization of lignocellulosic cell wall biomass is highly desired. Great effort has been invested in understanding of how cell walls are formed in plant in recent years. Plants cell walls contain cellulose, hemicelluloses, pectic polysaccharides and lignin. These polysaccharides and phenolic polymers are constructed in concrete cell walls for supporting plant growth and development. Cellulose is composed of β-1,4-linked glucose units and a bundle of multiple -1,4-glucan chains together form microfibrils, providing a skeleton of cell wall structures. Cellulose is synthesized in plants by cellulose synthase (CesA) complexes which are integrated and localized in plasma membrane. There are a family of CesA genes in plants which direct cellulose synthesis in different layer of cell walls or regulate cellulose microfibril structures. Although cellulose has been used in many aspects of human life, such as fiber cloth, paper, and modified cellulosic products, Cellulose, the most abundant biopolymer on the Earth, promises more utilization in supporting for sustainability of human society development. Hemicellulose is a group of diverse polysaccharides, such as xyloglucan, heteromannans, heteroxylans and mixed- linkage glucan. Their diverse structure and sugar composition varies in plant species, tissues, even cell types. Hemicellulose polysaccharides, amorphous and soluble in aqueous solutions, are composed of heterogeneous monosaccharide units or linkages in their backbone and branched side chains. Hemicelluloses are usually covalently linked to cellulose and lignin in cell wall matrix. Hemicellulose has been used in many applications such as food products and nutritional supplements. How is hemicellulose synthesized? How do the diverse hemicelluloses function in plant development? How can the abundant hemicellulose sugars be used? Many questions remain to be investigated. Lignin is polymerized from phenolic monolignols and mainly deposited in the secondary cell walls of vascular plants. Evolved in higher plants, lignin is essential for long distance water transport, mechanical support of up-growth, pathogen defense and for other stress responses. In the cell walls, lignin is usually cross-linked with cellulose and hemicellulose. Although biosynthesis of monolignols including p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) monolignols has been elucidated genetically and biochemically in various plant species, regulation of monolignol formation in different species, tissues and cell types is still unclear. As the second most abundant plant biopolymer after cellulose on the globe, utilization of lignin is highly attended. Lignin is considered as a main recalcitrance during cell wall biomass conversion, therefore modification of lignin biosynthesis is of great interest in engineering plant cell walls for efficient biomass utilization. Laboratory research has showed potential benefits of lignin engineering for lignocellulosic biomass conversion, while application of the technology in the field requires more evaluation. This review summarizes recent studies of the biosynthesis of plant cell wall components such as cellulose, hemicelluloses and lignin as well as the modification of cell walls for the improvement of lignocellulosic biomass utilization.

Vascular smooth muscle cells in Marfan syndrome aneurysm: the broken bricks in the aortic wall.

Marfan syndrome (MFS) is a connective tissue disorder with multiple organ manifestations. The genetic cause of this syndrome is the mutation of the FBN1 gene, encoding the extracellular matrix (ECM) protein fibrillin-1. This genetic alteration leads to the degeneration of microfibril structures and ECM integrity in the tunica media of the aorta. Indeed, thoracic aortic aneurysm and dissection represent the leading cause of death in MFS patients. To date, the most effective treatment option for this pathology is the surgical substitution of the damaged aorta. To highlight novel therapeutic targets, we review the molecular mechanisms related to MFS etiology in vascular smooth muscle cells, the foremost cellular type involved in MFS pathogenesis.

Application of steam explosion as a method of wood matrix thermochemical activation

The thermochemical activation of a juniper lignin–carbohydrate matrix was carried out using a steam explosion method in order to have an impact on the micro- and ultrastructure of coniferous wood. Changes in the chemical composition, the physico-chemical characteristics of the components and the morphological features of the wood substance during treatment were studied. The possibility of applying steam explosion as a method of directed influence upon the lignin–carbohydrate complex was shown. Thermochemical activation of lignin–carbohydrate plant matrix occurs due to the directed destruction of ester and H-bonds in the lignin–carbohydrate complex, disturbance of thermodynamic equilibrium in the system and increase of mobility of labile complexes of biopolymers. Such a directed influence allows the opening of deep layers of the cell wall and provides new data about the specific composition and structure of a wood substance and its components. Thus, the stability of the helical structures of cellulose microfibrils in the S2 layer and high mobility of intercellular lignin after the steam explosion treatment were shown.

Synthesis and characterization of copolymers of poly(m-xylylene adipamide) and poly(ethylene terephthalate) oligomers by melt copolycondensation

Poly(m-xylylene adipamide)/poly(ethylene terephthalate) (MXD6/PET) copolymers are synthesized by melt copolycondensation with 1–5wt% low molecular weight PET oligomers into the MXD6 oligomers at 260°C. FR-IR and 1H NMR analysis results indicate that the interchange reaction has occurred between MXD6 oligomers and PET oligomers. The thermal behavior of copolymers shows that the melting temperature of MXD6/PET copolymers decreases with the increasing of amount of PET oligomers, while the crystallization temperature accordingly increases. And the equilibrium temperature Tm0 is evaluated to be 251.8°C for the copolymers with 5wt% PET oligomer adding, which is very close to that of neat MXD6. The tensile and impact strength of MXD6/PET copolymers are significantly improved than that of pure MXD6 by mechanical properties test, and the microfibril structure in the impact fracture sample's surface reveals the feature of ductile fracture.

Microtubule encounter-based catastrophe in Arabidopsis cortical microtubule arrays.

BackgroundThe cortical microtubules (CMTs) that line the plasma membrane of interphase plant cells are extensively studied owing to their importance in forming cell walls, and their usefulness as a model system for the study of MT dynamic instability and acentrosomal MT organization. CMTs influence the orientation and structure of cellulose microfibrils in the cell wall by cooperatively forming arrays of varied patterns from parallel to netted. These CMT patterns are controlled by the combined activities of MT dynamic instability and MT-MT interactions. However, it is an open question as to how CMT patterns may feedback to influence CMT dynamics and interactions.ResultsTo address this question, we investigated the effects of CMT array patterning on encounter-based CMT catastrophe, which occurs when one CMT grows into another and is unable to cross over. We hypothesized that the varied CMT angles present in disordered (mixed CMTs) arrays will create more opportunities for MT-MT interactions, and thus increase encounter-based catastrophe rates and distribution. Using live-cell imaging of Arabidopsis cotyledon and leaf epidermal cells, we found that roughly 87 % of catastrophes occur via the encounter-based mechanism, with the remainder occurring without encounter (free). When comparing ordered (parallel) and disordered (mixed orientation) CMT arrays, we found that disordered configurations show higher proportions of encounter-based catastrophe relative to free. Similarly, disordered CMT arrays have more catastrophes in general than ordered arrays. Encounter-based catastrophes were associated with frequent and sustained periods of pause prior to depolymerization, and CMTs with tight anchoring to the plasma membrane were more prone to undergo encounter-based catastrophe than weakly-attached ones. This suggests that encounter-based catastrophe has a mechanical basis, wherein MTs form physical barriers to one another. Lastly, we show that the commonly used measure of catastrophe frequencies (Fcat) can also be influenced by CMT ordering and plasma membrane anchoring.ConclusionsOur observations add a new layer of complexity to our current understanding of MT organization in plants, showing that not only do individual CMT dynamics influence CMT array organization, but that CMT organization itself has a strong effect on the behavior of individual MTs.

Cellulose is not degraded in the tunic of the edible ascidian Halocynthia roretzi contracting soft tunic syndrome.

Soft tunic syndrome is a fatal disease in the edible ascidian Halocynthia roretzi, causing serious damage to ascidian aquaculture in Korea and Japan. In diseased individuals, the tunic, an integumentary extracellular matrix of ascidians, softens and eventually tears. This is an infectious disease caused by the kinetoplastid flagellate Azumiobodo hoyamushi. However, the mechanism of tunic softening remains unknown. Because cellulose fibrils are the main component of the tunic, we compared the contents and structures of cellulose in healthy and diseased tunics by means of biochemical quantification and X-ray diffractometry. Unexpectedly, the cellulose contents and structures of cellulose microfibrils were almost the same regardless of the presence or absence of the disease. Therefore, it is unlikely that thinning of the microfibrils occurred in the softened tunic, because digestion should have resulted in decreases in crystallinity index and crystallite size. Moreover, cellulase was not detected in pure cultures of A. hoyamushi in biochemical and expressed sequence tag analyses. These results indicate that cellulose degradation does not occur in the softened tunic.