Cellulose Iβ Research Articles

Synchrotron X-ray fiber diffraction study on the thermal expansion behavior of cellulose crystals in tension wood of Japanese poplar in the low-temperature region

Abstract The thermal expansion behavior of tension wood cellulose obtained from Populus maximowiczii A. Henry was investigated by synchrotron X-ray fiber diffraction at temperatures ranging from 100 to 300 K. Three equatorial and one meridional d-spacings indexed as , 110, 200, and 004 showed a gradual linear increase with increasing temperature. Unit-cell parameters calculated from the changes in these d-spacings showed anisotropic thermal expansion behavior in the three axial directions related to the crystal structure and hydrogen-bonding system of cellulose Iβ. The linear thermal expansion coefficients (TECs) of the a-, b-, and c-axes were: α a=5.2×10-5 K-1, α b=2.1×10-5 K-1, and α c=0.4×10-5 K-1, respectively. The volume TEC was β=7.8×10-5 K-1, which was approximately 70% of previously reported values in the high-temperature region from room temperature to 250°C.

Active Movement of the Tunic in Halocynthia roretzi

Halocynthia roretzi, a solitary ascidian, can swell and deflate its solid, leather-like tunic largely, but it is not clear whether the tunic deforms actively. Cellulose Iβ, which is predominant in higher plants, is also present in the tunic as a highly crystalline form. The elastic modulus of its whisker crystalline is considerably high. Substantial amounts of chitin sulfate-like, water-soluble polysaccharide were also present. These polysaccharides alone would barely cause tunic deformation. If the tunic's flexible deformation is self-controlled, it would have another element in addition to the polysaccharide, and it would be an ideal model for designing a novel material. The hypothesis of this study was that the H. roretzi tunic has a nervous system, myocytes, and elastic fibers controlling its flexible deformation. Using acetylcholine and touch as stimuli, the tunic samples were found to deform at acetylcholine concentrations ≥20 µM, indicating the existence of a nervous system, and to have mechanosensitivity. The Bodian, Kluver-Barrera, acetylcholinesterase, immunohistochemical (α-smooth muscle actin), and Elastica-Masson staining methods indicated the presence of a nervous system, myocytes, a region rich in α-smooth muscle actin, and elastic fibers, validating the hypothesis. The self-controlled system in the tunic is useful to understand the properties of the tunic and to design a novel actively deforming material.

Polysaccharide Degradation and Lignin Modification during Brown Rot of Spruce Wood: A Polarised Fourier Transform near Infrared Study

Radial thin sections of spruce wood that had been degraded by brown-rot fungi ( Gloeophyllum trabeum or Poria placenta) exhibiting mass losses up to 16% were investigated by polarised Fourier transform near infrared (FT-NIR) transmission spectroscopy. This method allowed for the analysis of the changes within wood caused by the decay fungi. The main features of brown rot visible in the FT-NIR spectra were the reduction of amorphous wood polysaccharides in preference to crystalline, an overall loss of molecular orientation of the structural polymers, and the formation of phenolic groups in lignin through cleavage of aryl–ether bonds or demethoxylation. Furthermore, polarised FT-NIR spectroscopy allowed us to examine the assignments of the first overtones of O–H stretching vibrations in more detail and to suggest a number of new band assignments in this spectral region. Among them were the bands of the 0(3)–H(3)···O(5) intramolecular hydrogen bond of glucomannan and the strong parallel intramolecular hydrogen bond 0(2)–H(2)···O(6), which is only accessible with polarised NIR spectroscopy because it overlaps with a number of perpendicular bands, among them the perpendicular O(6)–H(6)···O(3)′ intermolecular hydrogen bond of crystalline cellulose. First overtones of strongly H-bonded O–H groups of cellulose Iβ (6340 cm−1) and cellulose Iα (6270 cm−1) were tentatively assigned.

Computational simulations of the Trichoderma reesei cellobiohydrolase I acting on microcrystalline cellulose Iβ: the enzyme–substrate complex

Cellobiohydrolases are the dominant components of the commercially relevant Trichoderma reesei cellulase system. Although natural cellulases can totally hydrolyze crystalline cellulose to soluble sugars, the current enzyme loadings and long digestion times required render these enzymes less than cost effective for biomass conversion processes. It is clear that cellobiohydrolases must be improved via protein engineering to reduce processing costs. To better understand cellobiohydrolase function, new simulations have been conducted using charmm of cellobiohydrolase I (CBH I) from T. reesei interacting with a model segment (cellodextrin) of a cellulose microfibril in which one chain from the substrate has been placed into the active site tunnel mimicking the hypothesized configuration prior to final substrate docking (i.e., the +1 and +2 sites are unoccupied), which is also the structure following a catalytic bond scission. No tendency was found for the protein to dissociate from or translate along the substrate surface during this initial simulation, nor to align with the direction of the cellulose chains. However, a tendency for the decrystallized cellodextrin to partially re-anneal into the cellulose surface hints that the arbitrary starting configuration selected was not ideal.

X‐ray diffraction study of the thermal expansion behavior of cellulose triacetate I

AbstractHighly crystalline samples of cellulose triacetate I (CTA I) were prepared from highly crystalline algal cellulose by heterogeneous acetylation. X‐ray diffraction of the prepared samples was carried out in a helium atmosphere at temperatures ranging from 20 to 250 °C. Changes in seven d‐spacings were observed with increasing temperature due to thermal expansion of the CTA I crystals. Unit cell parameters at specific temperatures were determined from these d‐spacings by the least squares method, and then thermal expansion coefficients (TECs) were calculated. The linear TECs of the a, b, and c axes were αa = 19.3 × 10−5 °C−1, αb = 0.3 × 10−5 °C−1 (T < 130 °C), αb = −2.5 × 10−5 °C−1 (T > 130 °C), and αc = −1.9 × 10−5 °C−1, respectively. The volume TEC was β = 15.6 × 10−5 °C−1, which is about 1.4 and 2.2 times greater than that of cellulose Iβ and cellulose IIII, respectively. This large thermal expansion could occur because no hydrogen bonding exists in CTA I. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 517–523, 2009

Cellulose microfibrils from banana rachis: Effect of alkaline treatments on structural and morphological features

Four different alkaline treatments for isolation of cellulose microfibrils from vascular bundles of banana rachis were comparatively studied. Isolated cellulose microfibrils were characterized using high performance anion exchange chromatography for neutral sugar composition, as well as attenuated total reflection Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray and electron diffraction and solid-state 13C NMR. The cellulose microfibrils treated with peroxide alkaline, peroxide alkaline–hydrochloric acid or 5 wt% potassium hydroxide had average diameters of 3–5 nm, estimated lengths of several micrometers. Although the interpretation of their structure is difficult because of the low cristallinity, X-ray diffraction, 13C NMR and ATR-FTIR results suggested that cellulose microfibrils from banana rachis could be either interpreted as cellulose IV 1 or cellulose Iβ. The specimens treated with a more concentrated KOH solution (18 wt%) were still microfibrillated but their structure was converted to cellulose II.

Structure and Thermal Behavior of a Cellulose I−Ethylenediamine Complex

We prepared highly crystalline samples of a cellulose I-ethylenediamine (EDA) complex by immersing oriented films of algal (Cladophora) cellulose microcrystals in EDA at room temperature for a few days. The unit-cell parameters were determined to be a = 0.455, b = 1.133, and c = 1.037 nm (fiber repeat) and gamma = 94.02 degrees. The space group was P2(1). On the basis of unit cell, density, and thermogravimetry analyses, the asymmetric unit is composed of one anhydrous glucose residue and one EDA molecule. The chemical and thermal stabilities of the cellulose I-EDA complex were also investigated by the use of X-ray diffraction. When the cellulose I-EDA complex was immersed in methanol or water at room temperature, cellulose III I or I beta was obtained, respectively. However, immersion in a nonpolar solvent such as toluene did not affect the crystal structure of the complex. The cellulose I-EDA complex was stable up to a temperature of approximately 130 degrees C, whereas the boiling point of EDA is 117 degrees C. This thermal stability of the complex is probably caused by intermolecular hydrogen bonds between EDA molecules and cellulose. When heated above 150 degrees C, the cellulose I-EDA complex decomposed into cellulose I beta.

The structure of celluloses

X-ray and neutron fiber diffraction has been used to study cellulose as it is converted from its naturally occurring crystal phase, cellulose I, to an activated crystal phase, cellulose IIII, by ammonia treatment. The detailed crystal structures determined for cellulose Iβ, an intermediate ammonia-cellulose I complex, and cellulose IIII, reveal a structural transition pathway: hydrogen bonded sheets of chains in cellulose Iβ slip with respect to each other to accommodate the penetrating ammonia guest molecules in the intermediate complex. On evaporation of ammonia from the intermediate complex, there is a relative small change in chain packing as an inter-sheet ammonia bridge is replaced by an inter-sheet hydrogen bond in cellulose IIII. When cellulose IIII is heated it converts back to cellulose Iβ. Both ammonia-cellulose I and cellulose IIII have extended chains of cooperative hydrogen bonds in relatively open crystal structures that may add to their susceptibility to rapid change.

Simulation of X-ray diffractograms relevant to the purported polymorphs cellulose IVI and IVII

Diffractograms were simulated for model nanocrystals of cellulose Iβ, using numerical summation of radiation scattered from all carbon and oxygen atoms in the nanocrystal. Diffractogram peaks were sometimes displaced by a few degrees from positions calculated by the Bragg equation, as predicted in a published study based on a different mathematical approach. Simulated diffractograms showed 2 or 3 peaks, depending on the cross-sectional size and shape of the model nanocrystal. Some of the 2-peak diffractograms resembled published results for the purported polymorph cellulose IVI, or for cell-wall cellulose, supporting suggestions that cellulose IVI is simply cellulose I fragmented into nanocrystals with relatively small cross-sectional dimensions. A published diffractogram for cellulose IVII could not be simulated with acceptable precision, suggesting that this polymorph might have a crystal structure distinctly different from that of cellulose Iβ.

Wetting the (110) and (100) Surfaces of Iβ Cellulose Studied by Molecular Dynamics

Wetting the (110) and (100) Surfaces of Iβ Cellulose Studied by Molecular Dynamics

The effect of cooperativity on hydrogen bonding interactions in native cellulose Iβ from ab initio molecular dynamics simulations

Hydrogen bonding cooperativity plays an important role in the stability of α-helices, β-sheets and many other hydrogen bonding systems. Here ab initio calculations were performed to determine the cooperative effect on hydrogen bonding structures in native crystalline cellulose Iβ. Both isolated and paired cellulose chains with degree of polymerisation varying from 2 to 7 were investigated. A highly cooperative hydrogen bonding interaction was found in the paired cellulose chains, particularly between the inter-chain and intra-chain hydrogen bonds. An enhancement in hydrogen bonding strength was also observed when infinite cellulose chains were paired to form cellulose sheets, and when cellulose sheets were stacked to form three dimensional cellulose crystalline structures. This hydrogen bonding cooperativity is likely due to the electron delocalisation effect.

Interactions of the complete cellobiohydrolase I from Trichodera reesei with microcrystalline cellulose Iβ

We describe the construction of a model complex of the cellobiohydrolase I (CBH I) cellulase from Trichoderma reesei bound to a cellulose microfibril in an aqueous environment for use in molecular dynamics (MD) simulations. Preliminary characterization from the initial phases of an MD simulation of this complex is also described. The linker sequence between the two globular domains was found to be quite flexible, and the oligosaccharides bound to this linker were found to prefer to be splayed like the spokes in a wheel due to their hydration requirements. The overall conformations of the two globular domains remained stable in the simulations, although both underwent changes in their orientations.

Characterizing wood polymers in the primary cell wall of Norway spruce (Picea abies (L.) Karst.) using dynamic FT-IR spectroscopy

Dynamic Fourier Transform Infra-Red (FT-IR) spectroscopy was used to examine the interactions among cellulose, xyloglucan, pectin, protein and lignin in the outer fibre wall layers of spruce wood tracheids. Knowledge regarding these interactions is fundamental for understanding the fibre separation in a mechanical pulping process. Sheets made from an enriched primary cell wall material were used for studying the viscoelastic response of the polymers. The results indicated that strong interactions exist among lignin, protein, pectin, xyloglucan and cellulose in the primary cell wall. This signified a closely linked network structure of the components on the fibre surface. This ultrastructural arrangement in the primary cell wall and the relatively high content of lignin, pectin and protein in it, means that the primary cell wall is more submissive to selective chemical attacks, when compared to the secondary cell wall. A low ratio of cellulose Iα to cellulose Iβ in the primary cell wall was also found.

Bioengineering Bacterial Cellulose/Poly(ethylene oxide) Nanocomposites

By adding poly(ethylene oxide) (PEO) to the growth medium of Acetobacter xylinum, finely dispersed bacterial cellulose (BC)/PEO nanocomposites were produced in a wide range of compositions and morphologies. As the BC/PEO w/w ratio increased from 15:85 to 59:41, the cellulose nanofibers aggregated in larger bundles, indicating that PEO mixed with the cellulose on the nanometer scale [corrected]. Fourier transform infrared spectroscopy suggested intermolecular hydrogen bonding and also preferred crystallization into cellulose Ibeta in the BC/PEO nanocomposites. The fine dispersion of cellulose nanofibers hindered the crystallization of PEO, lowering its melting point and crystallinity in the nanocomposites although remaining bacterial cell debris also contributed to the melting point depression. The decomposition temperature of PEO also increased by approximately 15 degrees C, and the tensile storage modulus of PEO improved significantly especially above 50 degrees C in the nanocomposites. It is argued that this integrated manufacturing approach to fiber-reinforced thermoplastic nanocomposites affords a good flexibility for tailoring morphology and properties. These results further pose the question of the necessity to remove bacterial cells to achieve desirable materials properties in biologically derived products.

Temperature-Dependent Changes in Hydrogen Bonds in Cellulose Iα Studied by Infrared Spectroscopy in Combination with Perturbation-Correlation Moving-Window Two-Dimensional Correlation Spectroscopy: Comparison with Cellulose Iβ

Our recent IR study demonstrated that hydrogen-bond structure in cellulose Ibeta drastically changes around 220 degrees C (Watanabe et al. Biomacromolecules 2006, 7, 3164). In the present study, temperature-dependent IR spectra of cellulose Ialpha from 30 to 260 degrees C were analyzed by use of perturbation-correlation moving-window two-dimensional correlation spectroscopy. It was observed that as in the case of cellulose Ibeta abrupt changes in the hydrogen-bond structure occur around 220 degrees C in cellulose Ialpha. It was also revealed that although weakly hydrogen-bonded OH groups in Ibeta are stable below 230 degrees C thermal oxidation of those in Ialpha is accelerated around 220 degrees C. In this way, the present study has clarified a difference between the thermal behavior of Ialpha and that of Ibeta at the functional group level. Our result suggests that the drastic change in the hydrogen-bond structure around 220 degrees C makes cellulose Ialpha much more unstable than Ibeta.

Thermal characterization of bacterial cellulose–phosphate composite membranes

Cellulose–phosphate composite membranes have been prepared from bacterial cellulose membranes (BC) and sodium polyphosphate solution. The structure and thermal behavior of the new composites were evaluated by X-ray diffraction (XRD), 31P-nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetry (TG) and thermomechanical analysis (TMA). From XRD analyses the Iα and Iβ cellulose crystalline phases were identified together with crystalline sodium phosphate that covers the cellulose microfibrils as revealed by SEM. 31P NMR spectra show peaks assigned to Q0 and Q1 phosphate structures to be compared to the Q2 units that characterize the precursor polyphosphate. Glass transition temperature, Tg, obtained from TMA curves and thermal stability obtained from TG and DSC measurements, were observed to be dependent on the phosphate content.

Molecular Dynamics Simulations of Solvated Crystal Models of Cellulose Iα and IIII

Swelling behaviors of cellulose I(alpha) and III(I) crystals have been studied using molecular dynamics simulations of the solvated finite-crystal models. The typical crystal models consisted of 48 x 10-mer chains. For the cellulose I(alpha) crystal, models consisting of different numbers of chains and chain lengths were also studied. The structural features of the swollen crystal models, including the cellulose I(beta) crystal model reported previously, were compared. A distinct right-handed twist was observed for models of the native cellulose crystals (cellulose I(alpha) and I(beta)), with a greater amount of twisting observed for the I(alpha) crystal model. Although the amount of twist decreased with increasing dimensions of the cellulose I(alpha) crystal model, the relative changes in twist angle suggest that considerable twist would arise in a crystal model of the actual dimensions. In contrast to the swelling behavior of crystal models of the native cellulose, the cellulose III(I) crystal model exhibited local, gradual disordering at the corner of the reducing end. Comparison of the lattice energies indicated that the cellulose chains of the I(beta) crystal were packed in the most stable fashion, whereas those of the I(alpha) and III(I) crystals were in a metastable state, which is consistent with the crystallization behaviors observed. Upon heating of the native cellulose crystal models, the chain sheets of the I(alpha) model showed a continuous increase in twist angle, suggesting weaker intersheet interactions in this model. The swollen crystal models of cellulose I(alpha) and III(I) reproduce well the representative structural features observed in the corresponding crystal structures. The crystal model twist thus characterizes the swelling behavior of the native cellulose crystal models, which seems to be related to the insolubility of the crystals.

Swelling behavior of the cellulose Iβ crystal models by molecular dynamics

The various crystal models of cellulose Iβ, each differing in crystal size, have been studied by computer simulation using the amber molecular-dynamics package and the GLYCAM parameters. The four types of crystal model were constructed by a combination of two base-plane sizes, consisting of either 24 or 48 chains and two chain lengths having either 10 or 20 residues. The base planes of the crystal models were composed by the edges of the [1, 1, 0], [1, −1, 0], and [1, 0, 0] crystal planes, where the [1, 1, 0] plane was assigned to the longest edge. The crystal models were soaked in water boxes to investigate their swelling behavior. Unexpectedly, the crystal models twisted quickly to form a slightly right-handed shape during the initial ∼50 ps and that, in a steady, swollen state, the twisted forms remained for the rest of the simulation time. In spite of such overall deformation, the inner part of the swollen model fairly reproduced the important structural features of the original crystal structure, such as the rotational positions of the substituent groups and the hydrogen-bonding scheme. On heating the crystal model up to 550 K, the twisted shape was conserved in most of the temperature range, while the initial conformations of the substituent groups deviated above ∼430 K, followed by appreciable disordering in chain sheets at higher temperatures. It is suggested that some internal tensions are involved within a chain sheet of the initial structure. In the course of swelling, some of these tensions were released to introduce a twisted shape in the crystal models.

Estimation of the Elastic Modulus of Cellulose Crystal by Molecular Mechanics Simulation

The elastic modulus of natural cellulose crystal was estimated by the molecular simulation technique. Values between 124 and 155 GPa were derived for the reasonable cellulose Iβ crystal model that were nearly equal to the observed value of 138 GPa. While the second-generation force fields were found to be superior to the first-generation ones for the optimization of cellulose structure, neither of these was good enough to achieve the structural optimization. They were, however, adequate for estimating the mechanical properties of cellulose, especially the second-generation force fields. The lateral (that is, intermolecular) interactions between cellulose chains were found to play an important role in the expression of the mechanical properties of cellulose crystal.

Oligosaccharide Analogues of Polysaccharides. Part 26

AbstractThe anthraquinone derivatives T‐x‐x (x = 2, 4, and 8), possessing two cellobiosyl, cellotetraosyl, and cellooctaosyl chains, respectively, C‐glycosidically bonded at C(1) and C(8) were synthesised as potential mimics of cellulose I. The anthraquinone template enforces a parallel orientation of the cellodextrin chains at a distance corresponding to the one between the crystallographically independent chains of cellulose I, and the ethynyl and buta‐1,3‐diynyl linker units ensure an appropriate phase shift between them. The H‐bonding of the T‐x‐x mimics was analysed and compared to the one of the mono‐chained analogues T‐x and of the known cellulose II mimics N‐x‐x and N‐x where one or two cellodextrin chains are O‐glycosidically bonded to naphthalene‐1,8‐diethanol, or to naphthalene‐1‐ethanol. The OH signals of T‐x and T‐x‐x in solution in (D6)DMSO were assigned on the basis of DQFCOSY, HSQC, and TOCSY (only of T‐4, T‐4‐4, and T‐8‐8) spectra and on a comparison with the spectra of N‐x and N‐x‐x. Hydrogen bonding was analysed on the basis of the chemical shift of OH groups and its temperature dependence, coupling constants, SIMPLE 1H‐NMR experiments, and ROESY spectra. T‐4‐4 and T‐8‐8 in (D6)DMSO appear to adopt a V‐shape arrangement of the cellosyl chains, avoiding inter‐chain H‐bond interactions. The well‐resolved solid‐state CP/MAS 13C‐NMR spectra of the mono‐chained T‐x (x = 1, 2, 4, and 8) show that only T‐8 is a close mimic of cellulose II. While the solid‐state CP/MAS 13C‐NMR spectrum of the C1‐symmetric diglucoside T‐1‐1 is well‐resolved, the spectra of T‐2‐2 and T‐4‐4 show broad signals, and that of T‐8‐8 is rather well resolved. The spectrum of T‐8‐8 resembles that of cellulose Iβ. A comparison of the X‐ray powder‐diffraction spectra of T‐8‐8 and T‐8 with those of celluloses confirms that T‐8‐8 is a H‐bond mimic of cellulose I and T‐8 one of cellulose II.Surprisingly, there is little difference between the CP/MAS 13C‐NMR spectra of the acetyl protected mono‐chained C‐glycosylated anthraquinone derivatives A‐x and the double‐chained A‐x‐x (x = 2, 4, and 8). The spectra of A‐4 and A‐4‐4 resemble strongly the one of cellulose triacetate I (CTA I). The (less well‐resolved) spectra of the cellooctaosides A‐8 and A‐8‐8, however, resemble the one of CTA II. The similarity between the solid‐state CP/MAS 13C‐NMR spectra of A‐4 and A‐4‐4 to the one of CTA I, and of A‐8 and A‐8‐8 to the one of CTA II is opposite to the observations in the acetylated cellodextrin series.The mono‐chained A‐x cellulose triacetate mimics 21 (A‐2), 32 (A‐4), and 55 (A‐8) were synthesised by Sonogashira coupling of the cellooligosyl‐ethynes 15, 28, and 50, followed by selective deacetylation. Complete deacetylation provided the corresponding T‐x mimics. The double‐chained A‐x‐x mimics 24 (A‐2‐2), 35 (A‐4‐4), and 58 (A‐8‐8) were prepared from A‐x by triflation and Sonogashira coupling with the cellosyl‐buta‐1,3‐diynes 19, 31, and 53. Their deacetylation provided the corresponding T‐x‐x mimics 25, 36, and 59. The cellooligosyl‐ethynes and cellooligosyl‐buta‐1,3‐diynes required for the Sonogashira coupling were prepared by stepwise glycosylation of the partially O‐benzylated β‐cellobiosyl‐ethyne and β‐cellobiosyl‐buta‐1,3‐diyne 13 and 17, respectively, with the cellobiosyl donor 2 and the cellohexaosyl donor 47.