Catalytic activity of Cu2O nanoparticles supported on cellulose beads prepared by emulsion-gelation using cellulose/LiBr solution and vegetable oil.

Nanocatalysts tend to aggregate and are difficult to recycle, limiting their practical applications. In this study, an environmentally friendly method was developed to produce cellulose beads for use as supporting materials for Cu-based nanocatalysts. Cellulose beads were synthesized from a water-in-oil emulsion using cellulose dissolved in an LiBr solution as the water phase and vegetable oil as the oil phase. Upon cooling, the gelation of the cellulose solution produced spherical cellulose beads, which were then oxidized to introduce surface carboxyl groups. These beads (diameter: 95-105 µm; specific surface area: 165-225 m2 g-1) have a three-dimensional network of nanofibers (width: 20-30 nm). Furthermore, the Cu2O nanoparticles were loaded onto oxidized cellulose beads before testing their catalytic activity in the reduction of 4-nitrophenol using NaBH4. The apparent reaction rate constant increased with increasing loading of Cu2O nanoparticles and the conversion efficiency was >90 %. The turnover frequency was 376.2 h-1 for the oxidized cellulose beads with the lowest Cu2O loading, indicating a higher catalytic activity compared to those of other Cu-based nanoparticle-loaded materials. In addition to their high catalytic activity, the cellulose beads are reusable and exhibit excellent stability.

Elucidation of the Specific Ion Effects and Intermediate Structures of Cellulose Fibers Swollen in Inorganic Salt Solutions via In Situ X-ray Diffraction.

The solubilities of many substances are significantly affected by specific ions, as demonstrated by the Hofmeister series of proteins. Cellulose has a resistant fibrillar structure that hinders its swelling and dissolution. Certain inorganic salt solutions are effective swelling agents and solvents for cellulose. However, the precise effects of these ions on cellulose are not fully understood. In this study, we studied the intermediate structures of cellulose fibers during their swelling process in ZnCl2 and LiBr solutions via in situ X-ray diffraction. Two swollen phases with characteristic morphologies were observed for both salt treatments. Only the surfaces of the fibers were swollen in ZnCl2, whereas the ions penetrated the fibers and formed complexes with cellulose while the morphology of the fibers was maintained in LiBr. Our findings clarify the reasons that ZnCl2 has been used as an excellent swelling agent, whereas LiBr has been used as a good solvent for cellulose.

α-d-(1 → 3)-graft-(1 → 6)-glucan: Comb-like polysaccharide synthesized in vitro with α-1,3/1,6-glucosyltransferase L from Streptococcus salivarius.

We demonstrated that a unique polysaccharide with extremely high molecular weight can be easily obtained via a low-cost, mild reaction in a water medium from sucrose, a photosynthetic product. α-1,3/1,6-Glucosyltransferase L (GtfL) from Streptococcus salivarius produced water-insoluble α-d-glucan from sucrose at 37 °C. Gel permeation chromatography revealed the molecular weight was extremely high; the weight-average molecular weight values were more than 1,000,000 irrespective of the substrate concentration. The Smith degradation of neat glucan and NMR spectroscopic analyses of the acetyl derivative revealed a structure similar to that of a comb-type graft copolymer, α-d-(1 â†’ 3)-graft-(1 â†’ 6)-glucan. The anhydroglucose units (AGUs) in the main-chain backbone are linked by (1 â†’ 3)-glycosidic bonds, whereas a side chain consisting of four AGUs via (1 â†’ 6)-glycosidic bonds alternately extends from C6 of the main chain.

Atomic-scale dents on cellulose nanofibers: the origin of diverse defects in sustainable fibrillar materials.

Atomic-scale dent structures on the surfaces of cellulose nanofibers were detected by comparing the experimentally measured and computer-simulated widths of single nanofibers. These dent parts constituted at least 30-40% of the total length of the dispersed nanofibers, and deep dents induced the kinking and fragmentation of nanofibers.

Recovery of the Irreversible Crystallinity of Nanocellulose by Crystallite Fusion: A Strategy for Achieving Efficient Energy Transfers in Sustainable Biopolymer Skeletons*.

Crystallites form a grain boundary or the inter-crystallite interface. A grain boundary is a structural defect that hinders the efficient directional transfer of mechanical stress or thermal phonons in crystal aggregates. We observed that grain boundaries within an aggregate of crystalline cellulose nanofibers (CNFs) were crystallized by enhancing their inter-crystallite interactions; multiple crystallites were coupled into single fusion crystals, without passing through a melting or dissolving state. Accordingly, the lowered crystallinity of CNFs, which has been considered irreversible, was recovered, and the thermal energy transfer in the aggregate was significantly improved. Other nanofibrous crystallites of chitin also showed a similar fusion phenomenon by enhancing the inter-crystallite interactions. Such crystallite fusion may naturally occur in biological structures with network skeletons of aggregated fibrillar crystallites having mechanical or thermal functions.

Local Crystallinity in Twisted Cellulose Nanofibers.

Cellulose is crystallized by plants and other organisms into fibrous nanocrystals. The mechanical properties of these nanofibers and the formation of helical superstructures with energy dissipating and adaptive optical properties depend on the ordering of polysaccharide chains within these nanocrystals, which is typically measured in bulk average. Direct measurement of the local polysaccharide chain arrangement has been elusive. In this study, we use the emerging technique of scanning electron diffraction to probe the packing of polysaccharide chains across cellulose nanofibers and to reveal local ordering of the chains in twisting sections of the nanofibers. We then use atomic force microscopy to shed light on the size dependence of the inherent driving force for cellulose nanofiber twisting. The direct measurement of crystalline twisted regions in cellulose nanofibers has important implications for understanding single-cellulose-fibril properties that influence the interactions between cellulose nanocrystals in dense assemblies. This understanding may enable cellulose extraction and separation processes to be tailored and optimized.

In Vitro Synthesis of Branchless Linear (1 → 6)-α-d-Glucan by Glucosyltransferase K: Mechanical and Swelling Properties of Its Hydrogels Crosslinked with Diglycidyl Ethers.

A hydrogel was prepared from a polysaccharide, enzymatically synthesized through a one-pot reaction in aqueous solution, and its properties as a functional material were evaluated. Enzymatic synthesis using glucosyltransferase K obtained from Streptococcus salivarius ATCC 25975 was performed with sucrose as a substrate. The synthetic product was unbranched linear (1 → 6)-α-d-glucan with a high molecular weight, M w: 1.0-3.0 × 105. The synthesized (1 → 6)-α-d-glucan was insoluble in water and crystallized in a monoclinic unit cell, which is consistent with the hydrated form of dextran. Transparent and highly swellable (1 → 6)-α-d-glucan hydrogels were obtained by crosslinking with diglycidyl ethers. The hydrogels showed no syneresis and no volume change during compression, resulting in the retention of shape under repeated compression. The elastic moduli of these hydrogels (<60 kPa) are smaller than those of other polysaccharide-based hydrogels having the same solid contents. The oven-dried gels could be restored to the hydrogel state with the original transparency and a recovery ratio greater than 98%. The mechanism of water diffusion into the hydrogel was investigated using the kinetic equation of Peppas. The properties of the hydrogel are impressive relative to those of other polysaccharide-based hydrogels, suggesting its potential as a functional biomaterial.

Crystallinity-Independent yet Modification-Dependent True Density of Nanocellulose.

In materials science and crystallography, the true density is an important derived physical quantity of solids. Here we report the correlation of the true density of nanometer-wide fibrillar crystallites of cellulose with their purity, crystallinity, morphology, and surface functionality. In the single fibrils, all the cellulose molecules are uniaxiallly oriented. Thus, the true density indicates the molecular packing density in the single fibrils and is essential for the precise estimation of the volume fraction of cellulose in fibril-based composites or porous structures. We demonstrate that the true density of fibrillar crystallites of cellulose is approximately 1.60 g/cm3 irrespective of the biological origins of the cellulose (wood, cotton, or a tunicate) and the crystallinity. The true density is in fact independent of the dimension of the crystallites and the atomic conformation of the uniaxially oriented but noncrystalline molecules at the crystallite surface. In the single fibrils, all the cellulose molecules are densely packed from the crystalline core to the noncrystalline outermost regions. The value of 1.60 g/cm3 remains unchanged even when the fibrils are dispersed through the wet disintegration process of "nanocellulose" production. In contrast, tailoring the surface functionality of the fibrils by oxidation and/or adsorption results in a substantial change in the true density up to 1.8 g/cm3 or down to 1.3 g/cm3. The true density of nanocellulose is indeed governed by the surface functionality and has a strong gradient in the fibril cross-sectional direction.

Carboxylated nanocellulose/poly(ethylene oxide) composite films as solid-solid phase-change materials for thermal energy storage.

Composite films of poly(ethylene oxide) (PEO) and 0%-20% surface-carboxylated cellulose nanofibrils (CNFs) were prepared by mixing the aqueous CNF dispersion and aqueous PEO solution at various weight ratios followed by casting and drying. The 20% CNF/PEO composite film was transparent, whereas the 100% PEO film was translucent. The addition of CNFs to the PEO matrix resulted in decreases of the crystallinity and crystal size of spherical PEO. The Young's modulus and tensile strength of the 100% PEO film were 0.2 GPa and 6.1 MPa, respectively, and remarkably increased to 2.4 GPa and 86 MPa, respectively, with the addition of 20% CNF. The CNF/PEO composite films had clear melting and crystallization temperatures in the heating and cooling processes, respectively. Nevertheless, the coefficients of thermal expansion at temperatures above the melting point of PEO significantly decreased with the CNF addition. The CNF/PEO composite films are therefore promising solid-solid phase-change materials for energy storage with high film dimensional stability.

Anatomical features of Fagaceae wood statistically extracted by computer vision approaches: Some relationships with evolution.

The anatomical structure of wood is complex and contains considerable information about its specific species, physical properties, growth environment, and other factors. While conventional wood anatomy has been established by systematizing the xylem anatomical features, which enables wood identification generally up to genus level, it is difficult to describe all the information comprehensively. This study apply two computer vision approaches to optical micrographs: the scale-invariant feature transform algorithm and connected-component labelling. They extract the shape and pore size information, respectively, statistically from the whole micrographs. Both approaches enable the efficient detection of specific features of 18 species from the family Fagaceae. Although the methods ignore the positional information, which is important for the conventional wood anatomy, the simple information on the shape or size of the elements is enough to describe the species-specificity of wood. In addition, according to the dendrograms calculated from the numerical distances of the features, the closeness of some taxonomic groups is inconsistent with the types of porosity, which is one of the typical classification systems for wood anatomy, but consistent with the evolution based on molecular phylogeny; for example, ring-porous group Cerris and radial-porous group Ilex are nested in the same cluster. We analyse which part of the wood structure gave the taxon-specific information, indicating that the latewood zone of group Cerris is similar to the whole zone of group Ilex. Computer vision approaches provide statistical information that uncovers new aspects of wood anatomy that have been overlooked by conventional visual inspection.

Outstanding Toughness of Cherry Bark Achieved by Helical Spring Structure of Rigid Cellulose Fiber Combined with Flexible Layers of Lipid Polymers.

Cellulose, a main component of cell walls, generally makes materials hard and brittle. However, an ultratough, cellulosic material is found in nature: cherry bark. Surprisingly, it elongates by more than twice of its initial length and behaves as a plastic film during stretching. This amazing mechanical property is achieved by a well-designed cell wall structure; cellulose fibers are folded like helical springs, covered by multiple flexible layers of lipid polymers.

Characterization of crystalline linear (1→3)-α-d-glucan synthesized in vitro.

We investigated the crystal structure and molecular arrangement of the linear (1→3)-α-d-glucan synthesized by glucosyltransferase GtfJ cloned from Streptococcus salivarius using sucrose as a substrate. The synthetic products had two morphologies: wavy fibril-like crystals as major and thin lamellae as minor products. Their structures were analyzed using electron microdiffraction, synchrotron X-ray powder diffraction, and solid-state 13C NMR spectroscopy. The fibrils and lamellae had the same allomorphic form but different molecular arrangements. The wet crystals were in a hydrated form, which converted into an anhydrous form with a significant decrease in crystallinity on drying. The hydrated and anhydrous forms had an extended-chain conformation with 2/1 helix, and the hydrated form was estimated to contain one water molecule per glucose residue. The long glucan chains were folded in the fibril crystals, while the short, extended chains were arranged perpendicular to the base plane of the lamellae.

Thermal expansion behavior of A- and B-type amylose crystals in the low-temperature region.

The thermal expansion behaviors of A-type and B-type amylose crystals, which were prepared by recrystallization of short amylose chains synthesized by phosphorylase, were investigated using synchrotron X-ray powder diffraction between 100 and 300K. For both types of crystals, the room-temperature phase (RT phase), which is the usually observed phase, transitioned to a low-temperature phase (LT phase), on cooling. The phase transitions took place reversibly with rapid changes in the unit-cell parameters around 200-270K. The differences between the RT and LT phase were investigated using solid-state (13)C NMR spectroscopy, which revealed there were changes in molecular chain conformations. These results suggest that the phase transition of water molecules on the crystalline surfaces affects the thermal behavior and structure of polysaccharide crystals.

X-ray texture analysis indicates downward spinning of chitin microfibrils in tubeworm tube.

The direction of ß-chitin deposition in the tube of tubeworm Lamellibrachia satsuma was investigated by texture analysis using X-ray diffraction. The ß-chitin crystallite in the tube has planar orientation with the (110) plane perpendicular to the surface, and the c-axis is aligned parallel to the tube. The monoclinic unit cell of ß-chitin allowed determination of the sense of c-axis from the orientation of (010) and (100) planes. This means that the reducing end of ß-chitin is pointing up in the tube. This orientation can be ascribed to possible secretion mechanisms of the ß-chitin microfibrils, i.e. the chitin-synthesizing enzyme complex travels unidirectionally from top to bottom when the worm body contracts in the tube.

Crystal transition between hydrate and anhydrous (1→3)-ß-D-xylan from Penicillus dumetosus.

The crystal structures of hydrated and anhydrous (1→3)-ß-d-xylan and the crystal transition between them were investigated. Highly crystalline samples of (1→3)-ß-d-xylan were prepared from a siphoneous green alga, Penicillus dumetosus. The crystal structure was analyzed using synchrotron X-ray diffraction and solid-state (13)C NMR spectroscopy. The hydrated form was converted to the anhydrous form with contraction in both the a-axis and c-axis directions, and the crystallinity decreased considerably at the same time. The crystal transition between hydrated and anhydrous (1→3)-ß-d-xylan was monitored using synchrotron X-ray diffraction under controlled relative humidity. The transition took place at certain transition points, and was accompanied by a large hysteresis. From the difference in the weight and unit-cell volume at the transition points, the number of water molecules in the hydrated form was estimated as one per xylose residue.

Thermal expansion behavior of hydrate paramylon in the low-temperature region.

The thermal expansion behavior of hydrate paramylon between 100 and 300K has been investigated using synchrotron X-ray powder diffraction. The X-ray diffraction profile at 300K showed a typical pattern of the hydrate triple helical (1→3)-ß-d-glucan with a hexagonal unit cell (a=15.782Å and c=18.580Å). On cooling, the hydrate paramylon had converted to a "low-temperature phase" around 270K. On passing through the phase transition, the a-axis and c-axis values decreased and increased, respectively, and the low-temperature phase at 100K exhibited a hexagonal unit cell (a=15.586Å and c=18.619Å). The phase transition took place reversibly. Below the transition point, both the a-axis and c-axis values decreased linearly. The thermal expansion coefficients are: α(a)=1.50×10(-5)K(-1), α(c)=0.33×10(-5)K(-1), and ß=3.08×10(-5)K(-1).

2-Acetamido-2-de-oxy-3-O-ß-d-galactopyranosyl-d-glucose dihydrate.

In the title compound, C(14)H(25)NO(11)·2H(2)O, the primary hydroxyl group connected to the anomeric C atom of the N-acetyl-ß-d-glucopyran-ose residue exhibits positional disorder, with occupancy factors for the α and ß anomers of 0.77 and 0.23, respectively. The two torsion angles (Φ and Ψ) and the bridge angle (τ) that describe conformation of the glycosidic linkage between the galactopyran-ose and glucopyran-ose rings are Φ = -81.6 (3)°, Ψ = 118.1 (2)° and τ = 115.2 (2)°. Two water mol-ecules stabilize the mol-ecular packing by forming hydrogen bonds with the saccharide residues.

Involvement of ABC transporters in chemosensitivity of human renal cell carcinoma, and regulation of MRP2 expression by conjugated bilirubin.

In this study, the involvement of ATP-binding cassette (ABC) transporters in in vitro chemosensitivity of surgically removed human renal cell carcinomas was investigated. The relative expression levels of transporter mRNAs in the renal tumors from 13 patients were similar to those in the surrounding normal kidney tissues. Five renal cell carcinomas cultured successfully in vitro for 14 days showed significantly decreased expression of multi-drug resistance-associated proteins 2 and 6 (MRP2 and MRP6) mRNAs. In vitro chemosensitivity testing of the same specimens using the collagen-gel matrix assay indicated that some anticancer drugs were effective, especially cisplatin, which is an MRP2 substrate. MRP2 mRNA expression in renal carcinoma was significantly increased when cells were cultured in the presence of conjugated bilirubin. In an established renal proximal tubule epithelial cell line (RPTEC), conjugated bilirubin increased MRP2 expression at the mRNA and protein levels, and decreased the cisplatin sensitivity of the cells. These results indicate that MRP2 expression in renal cell carcinoma may be regulated by conjugated bilirubin in the body and decreased during in vitro culture. Thus, the effectiveness of anticancer drugs selected on the basis of in vitro chemosensitivity testing of clinical cancers may be overestimated.