Cellulose microfibril orientation of Picea abies and its variability at the micron-level determined by Raman imaging.

PubMed

Gierlinger, Notburga; Luss, Saskia; König, Christian; Konnerth, Johannes; Eder, Michaela; Fratzl, Peter

2010-01-01

The functional characteristics of plant cell walls depend on the composition of the cell wall polymers, as well as on their highly ordered architecture at scales from a few nanometres to several microns. Raman spectra of wood acquired with linear polarized laser light include information about polymer composition as well as the alignment of cellulose microfibrils with respect to the fibre axis (microfibril angle). By changing the laser polarization direction in 3 degrees steps, the dependency between cellulose and laser orientation direction was investigated. Orientation-dependent changes of band height ratios and spectra were described by quadratic linear regression and partial least square regressions, respectively. Using the models and regressions with high coefficients of determination (R(2) > 0.99) microfibril orientation was predicted in the S1 and S2 layers distinguished by the Raman imaging approach in cross-sections of spruce normal, opposite, and compression wood. The determined microfibril angle (MFA) in the different S2 layers ranged from 0 degrees to 49.9 degrees and was in coincidence with X-ray diffraction determination. With the prerequisite of geometric sample and laser alignment, exact MFA prediction can complete the picture of the chemical cell wall design gained by the Raman imaging approach at the micron level in all plant tissues.

Wide-Angle X-Ray Scattering and Solid-State Nuclear Magnetic Resonance Data Combined to Test Models for Cellulose Microfibrils in Mung Bean Cell Walls1

PubMed Central

Newman, Roger H.; Hill, Stefan J.; Harris, Philip J.

2013-01-01

A synchrotron wide-angle x-ray scattering study of mung bean (Vigna radiata) primary cell walls was combined with published solid-state nuclear magnetic resonance data to test models for packing of (1→4)-β-glucan chains in cellulose microfibrils. Computer-simulated peak shapes, calculated for 36-chain microfibrils with perfect order or uncorrelated disorder, were sharper than those in the experimental diffractogram. Introducing correlated disorder into the models broaden the simulated peaks but only when the disorder was increased to unrealistic magnitudes. Computer-simulated diffractograms, calculated for 24- and 18-chain models, showed good fits to experimental data. Particularly good fits to both x-ray and nuclear magnetic resonance data were obtained for collections of 18-chain models with mixed cross-sectional shapes and occasional twinning. Synthesis of 18-chain microfibrils is consistent with a model for cellulose-synthesizing complexes in which three cellulose synthase polypeptides form a particle and six particles form a rosette. PMID:24154621

Non-invasive imaging of cellulose microfibril orientation within plant cell walls by polarized Raman microspectroscopy.

PubMed

Sun, Lan; Singh, Seema; Joo, Michael; Vega-Sanchez, Miguel; Ronald, Pamela; Simmons, Blake A; Adams, Paul; Auer, Manfred

2016-01-01

Cellulose microfibrils represent the major scaffold of plant cell walls. Different packing and orientation of the microfibrils at the microscopic scale determines the macroscopic properties of cell walls and thus affect their functions with a profound effect on plant survival. We developed a polarized Raman microspectroscopic method to determine cellulose microfibril orientation within rice plant cell walls. Employing an array of point measurements as well as area imaging and subsequent Matlab-assisted data processing, we were able to characterize the distribution of cellulose microfibril orientation in terms of director angle and anisotropy magnitude. Using this approach we detected differences between wild type rice plants and the rice brittle culm mutant, which shows a more disordered cellulose microfibril arrangement, and differences between different tissues of a wild type rice plant. This novel non-invasive Raman imaging approach allows for quantitative assessment of cellulose fiber orientation in cell walls of herbaceous plants, an important advancement in cell wall characterization. © 2015 Wiley Periodicals, Inc.

Cellulose microfibril deposition: coordinated activity at the plant plasma membrane.

PubMed

Lindeboom, J; Mulder, B M; Vos, J W; Ketelaar, T; Emons, A M C

2008-08-01

Plant cell wall production is a membrane-bound process. Cell walls are composed of cellulose microfibrils, embedded inside a matrix of other polysaccharides and glycoproteins. The cell wall matrix is extruded into the existing cell wall by exocytosis. This same process also inserts the cellulose synthase complexes into the plasma membrane. These complexes, the nanomachines that produce the cellulose microfibrils, move inside the plasma membrane leaving the cellulose microfibrils in their wake. Cellulose microfibril angle is an important determinant of cell development and of tissue properties and as such relevant for the industrial use of plant material. Here, we provide an integrated view of the events taking place in the not more than 100 nm deep area in and around the plasma membrane, correlating recent results provided by the distinct field of plant cell biology. We discuss the coordinated activities of exocytosis, endocytosis, and movement of cellulose synthase complexes while producing cellulose microfibrils and the link of these processes to the cortical microtubules.

Cellulose structure and lignin distribution in normal and compression wood of the Maidenhair tree (Ginkgo biloba L.).

PubMed

Andersson, Seppo; Wang, Yurong; Pönni, Raili; Hänninen, Tuomas; Mononen, Marko; Ren, Haiqing; Serimaa, Ritva; Saranpää, Pekka

2015-04-01

We studied in detail the mean microfibril angle and the width of cellulose crystals from the pith to the bark of a 15-year-old Maidenhair tree (Ginkgo biloba L.). The orientation of cellulose microfibrils with respect to the cell axis and the width and length of cellulose crystallites were determined using X-ray diffraction. Raman microscopy was used to compare the lignin distribution in the cell wall of normal/opposite and compression wood, which was found near the pith. Ginkgo biloba showed a relatively large mean microfibril angle, varying between 19° and 39° in the S2 layer, and the average width of cellulose crystallites was 3.1-3.2 nm. Mild compression wood without any intercellular spaces or helical cavities was observed near the pith. Slit-like bordered pit openings and a heavily lignified S2L layer confirmed the presence of compression wood. Ginkgo biloba showed typical features present in the juvenile wood of conifers. The microfibril angle remained large over the 14 annual rings. The entire stem disc, with a diameter of 18 cm, was considered to consist of juvenile wood. The properties of juvenile and compression wood as well as the cellulose orientation and crystalline width indicate that the wood formation of G. biloba is similar to that of modern conifers. © 2015 Institute of Botany, Chinese Academy of Sciences.

Cellulose microfibril orientation of Picea abies and its variability at the micron-level determined by Raman imaging

PubMed Central

Gierlinger, Notburga; Luss, Saskia; König, Christian; Konnerth, Johannes; Eder, Michaela; Fratzl, Peter

2010-01-01

The functional characteristics of plant cell walls depend on the composition of the cell wall polymers, as well as on their highly ordered architecture at scales from a few nanometres to several microns. Raman spectra of wood acquired with linear polarized laser light include information about polymer composition as well as the alignment of cellulose microfibrils with respect to the fibre axis (microfibril angle). By changing the laser polarization direction in 3° steps, the dependency between cellulose and laser orientation direction was investigated. Orientation-dependent changes of band height ratios and spectra were described by quadratic linear regression and partial least square regressions, respectively. Using the models and regressions with high coefficients of determination (R2 > 0.99) microfibril orientation was predicted in the S1 and S2 layers distinguished by the Raman imaging approach in cross-sections of spruce normal, opposite, and compression wood. The determined microfibril angle (MFA) in the different S2 layers ranged from 0° to 49.9° and was in coincidence with X-ray diffraction determination. With the prerequisite of geometric sample and laser alignment, exact MFA prediction can complete the picture of the chemical cell wall design gained by the Raman imaging approach at the micron level in all plant tissues. PMID:20007198

The relation of apple texture with cell wall nanostructure studied using an atomic force microscope.

PubMed

Cybulska, Justyna; Zdunek, Artur; Psonka-Antonczyk, Katarzyna M; Stokke, Bjørn T

2013-01-30

In this study, the relation of the nanostructure of cell walls with their texture was investigated for six different apple cultivars. Cell wall material (CWM) and cellulose microfibrils were imaged by atomic force microscope (AFM). The mean diameter of cellulose microfibrils for each cultivar was estimated based on the AFM height topographs obtained using the tapping mode of dried specimens. Additionally, crystallinity of cellulose microfibrils and pectin content was determined. Texture of apple cultivars was evaluated by sensory and instrumental analysis. Differences in cellulose diameter as determined from the AFM height topographs of the nanostructure of cell walls of the apple cultivars are found to relate to the degree of crystallinity and pectin content. Cultivars with thicker cellulose microfibrils also revealed crisper, harder and juicier texture, and greater acoustic emission. The data suggest that microfibril thickness affects the mechanical strength of cell walls which has consequences for sensory and instrumental texture. Copyright © 2012 Elsevier Ltd. All rights reserved.

Exploring the Nature of Cellulose Microfibrils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Ying; Burger, Christian; Ma, Hongyang

2015-03-20

Ultrathin cellulose microfibril fractions were extracted from spruce wood powder using combined delignification, TEMPO-catalyzed oxidation, and sonication processes. Small-angle X-ray scattering of these microfibril fractions in a “dilute” aqueous suspension (concentration 0.077 wt %) revealed that their shape was in the form of nanostrip with 4 nm width and only about 0.5 nm thicknesses. We found that these dimensions were further confirmed by TEM and AFM measurements. The 0.5 nm thickness implied that the nanostrip could contain only a single layer of cellulose chains. At a higher concentration (0.15 wt %), SAXS analysis indicated that these nanostrips aggregated into amore » layered structure. The X-ray diffraction of samples collected at different preparation stages suggested that microfibrils were delaminated along the (110) planes from the Iβ cellulose crystals. Moreover, the degree of oxidation and solid-state 13C NMR characterizations indicated that, in addition to the surface molecules, some inner molecules of microfibrils were also oxidized, facilitating the delamination into cellulose nanostrips.« less

Exploring the nature of cellulose microfibrils.

PubMed

Su, Ying; Burger, Christian; Ma, Hongyang; Chu, Benjamin; Hsiao, Benjamin S

2015-04-13

Ultrathin cellulose microfibril fractions were extracted from spruce wood powder using combined delignification, TEMPO-catalyzed oxidation, and sonication processes. Small-angle X-ray scattering of these microfibril fractions in a "dilute" aqueous suspension (concentration 0.077 wt %) revealed that their shape was in the form of nanostrip with 4 nm width and only about 0.5 nm thicknesses. These dimensions were further confirmed by TEM and AFM measurements. The 0.5 nm thickness implied that the nanostrip could contain only a single layer of cellulose chains. At a higher concentration (0.15 wt %), SAXS analysis indicated that these nanostrips aggregated into a layered structure. The X-ray diffraction of samples collected at different preparation stages suggested that microfibrils were delaminated along the (11̅0) planes from the Iβ cellulose crystals. The degree of oxidation and solid-state (13)C NMR characterizations indicated that, in addition to the surface molecules, some inner molecules of microfibrils were also oxidized, facilitating the delamination into cellulose nanostrips.

Development of a size reduction equation for woody biomass: The influence of branch wood properties on Rittinger's constant

DOE PAGES

Naimi, Ladan J.; Sokhansanj, Shahabaddine; Bi, Xiaotao; ...

2015-11-25

Size reduction is an essential but energy-intensive process for preparing biomass for conversion processes. Three well-known scaling equations (Bond, Kick, and Rittinger) are used to estimate energy input for grinding minerals and food particles. Previous studies have shown that the Rittinger equation has the best fit to predict energy input for grinding cellulosic biomass. In the Rittinger equation, Rittinger's constant (k R) is independent of the size of ground particles, yet we noted large variations in k R among similar particle size ranges. In this research, the dependence of k R on the physical structure and chemical composition of amore » number of woody materials was explored. Branches from two softwood species (Douglas fir and pine) and two hardwood species (aspen and poplar) were ground in a laboratory knife mill. The recorded data included power input, mass flow rate, and particle size before and after grinding. Nine material properties were determined: particle density, solid density (pycnometer and x-ray diffraction methods), microfibril angle, fiber coarseness, fiber length, and composition (lignin and cellulose glucan contents). The correlation matrix among the nine properties revealed high degrees of interdependence between properties. The k R value had the largest positive correlation (+0.60) with particle porosity across the species tested. As a result, particle density was strongly correlated with lignin content (0.85), microfibril angle (0.71), fiber length (0.87), and fiber coarseness (0.78). An empirical model relating k R to particle density was developed.« less

Development of a size reduction equation for woody biomass: The influence of branch wood properties on Rittinger's constant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naimi, Ladan J.; Sokhansanj, Shahabaddine; Bi, Xiaotao

Size reduction is an essential but energy-intensive process for preparing biomass for conversion processes. Three well-known scaling equations (Bond, Kick, and Rittinger) are used to estimate energy input for grinding minerals and food particles. Previous studies have shown that the Rittinger equation has the best fit to predict energy input for grinding cellulosic biomass. In the Rittinger equation, Rittinger's constant (k R) is independent of the size of ground particles, yet we noted large variations in k R among similar particle size ranges. In this research, the dependence of k R on the physical structure and chemical composition of amore » number of woody materials was explored. Branches from two softwood species (Douglas fir and pine) and two hardwood species (aspen and poplar) were ground in a laboratory knife mill. The recorded data included power input, mass flow rate, and particle size before and after grinding. Nine material properties were determined: particle density, solid density (pycnometer and x-ray diffraction methods), microfibril angle, fiber coarseness, fiber length, and composition (lignin and cellulose glucan contents). The correlation matrix among the nine properties revealed high degrees of interdependence between properties. The k R value had the largest positive correlation (+0.60) with particle porosity across the species tested. As a result, particle density was strongly correlated with lignin content (0.85), microfibril angle (0.71), fiber length (0.87), and fiber coarseness (0.78). An empirical model relating k R to particle density was developed.« less

Hydrogen bonds and twist in cellulose microfibrils.

PubMed

Kannam, Sridhar Kumar; Oehme, Daniel P; Doblin, Monika S; Gidley, Michael J; Bacic, Antony; Downton, Matthew T

2017-11-01

There is increasing experimental and computational evidence that cellulose microfibrils can exist in a stable twisted form. In this study, atomistic molecular dynamics (MD) simulations are performed to investigate the importance of intrachain hydrogen bonds on the twist in cellulose microfibrils. We systematically enforce or block the formation of these intrachain hydrogen bonds by either constraining dihedral angles or manipulating charges. For the majority of simulations a consistent right handed twist is observed. The exceptions are two sets of simulations that block the O2-O6' intrachain hydrogen bond, where no consistent twist is observed in multiple independent simulations suggesting that the O2-O6' hydrogen bond can drive twist. However, in a further simulation where exocyclic group rotation is also blocked, right-handed twist still develops suggesting that intrachain hydrogen bonds are not necessary to drive twist in cellulose microfibrils. Copyright © 2017 Elsevier Ltd. All rights reserved.

Chemical genetic screening identifies a novel inhibitor of parallel alignment of cortical microtubules and cellulose microfibrils.

PubMed

Yoneda, Arata; Higaki, Takumi; Kutsuna, Natsumaro; Kondo, Yoichi; Osada, Hiroyuki; Hasezawa, Seiichiro; Matsui, Minami

2007-10-01

It is a well-known hypothesis that cortical microtubules control the direction of cellulose microfibril deposition, and that the parallel cellulose microfibrils determine anisotropic cell expansion and plant cell morphogenesis. However, the molecular mechanism by which cortical microtubules regulate the orientation of cellulose microfibrils is still unclear. To investigate this mechanism, chemical genetic screening was performed. From this screening, 'SS compounds' were identified that induced a spherical swelling phenotype in tobacco BY-2 cells. The SS compounds could be categorized into three classes: those that disrupted the cortical microtubules; those that reduced cellulose microfibril content; and thirdly those that had neither of these effects. In the last class, a chemical designated 'cobtorin' was found to induce the spherical swelling phenotype at the lowest concentration, suggesting strong binding activity to the putative target. Examining cellulose microfibril regeneration using taxol-treated protoplasts revealed that the cobtorin compound perturbed the parallel alignment of pre-existing cortical microtubules and nascent cellulose microfibrils. Thus, cobtorin could be a novel inhibitor and an attractive tool for further investigation of the mechanism that enables cortical microtubules to guide the parallel deposition of cellulose microfibrils.

Preparation of sago starch-based biocomposite reinforced microfibrillated cellulose of bamboo assisted by mechanical treatment

NASA Astrophysics Data System (ADS)

Silviana, S.; Hadiyanto, H.

2017-06-01

The utilization of green composites by using natural fibres is developed due to their availability, ecological benefits, and good properties in mechanical and thermal. One of the potential sources is bamboo that has relative high cellulose content. This paper was focused on the preparation of sago starch-based reinforced microfribrillated cellulose of bamboo that was assisted by mechanical treatment. Microfibrillated cellulose of bamboo was prepared by isolation of cellulose with chemical treatment. Preparation of bamboo microfibrillated cellulose was conducted by homogenizers for dispersing bamboo cellulose, i.e. high pressure homogenizer and ultrasonic homogenizer. Experiments were elaborated on several variables such as the concentration of bamboo microfibrillated cellulose dispersed in water (1-3 %w) and the volume of microfibrillated cellulose (37.5-75%v). Four %w of sago starch solution was mixed with bamboo microfibrillated cellulose and glycerol with plasticizer and citric acid as cross linker. This paper provided the analysis of tensile strength as well as SEM for mechanical and morphology properties of the biocomposite. The results showed that the preparation of sago starch-based biocomposite reinforced bamboo microfibrillated cellulose by using ultrasonic homogenizer yielded the highest tensile strength and well dispersed in the biocomposite.

Application of X-ray and neutron small angle scattering techniques to study the hierarchical structure of plant cell walls: a review.

PubMed

Martínez-Sanz, Marta; Gidley, Michael J; Gilbert, Elliot P

2015-07-10

Plant cell walls present an extremely complex structure of hierarchically assembled cellulose microfibrils embedded in a multi-component matrix. The biosynthesis process determines the mechanism of cellulose crystallisation and assembly, as well as the interaction of cellulose with other cell wall components. Thus, a knowledge of cellulose microfibril and bundle architecture, and the structural role of matrix components, is crucial for understanding cell wall functional and technological roles. Small angle scattering techniques, combined with complementary methods, provide an efficient approach to characterise plant cell walls, covering a broad and relevant size range while minimising experimental artefacts derived from sample treatment. Given the system complexity, approaches such as component extraction and the use of plant cell wall analogues are typically employed to enable the interpretation of experimental results. This review summarises the current research status on the characterisation of the hierarchical structure of plant cell walls using small angle scattering techniques. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Surface Plasmon Resonance Imaging of the Enzymatic Degradation of Cellulose Microfibrils

NASA Astrophysics Data System (ADS)

Reiter, Kyle; Raegen, Adam; Clarke, Anthony; Lipkowski, Jacek; Dutcher, John

2012-02-01

As the largest component of biomass on Earth, cellulose represents a significant potential energy reservoir. Enzymatic hydrolysis of cellulose into fermentable sugars, an integral step in the production of biofuel, is a challenging problem on an industrial scale. More efficient conversion processes may be developed by an increased understanding of the action of the cellulolytic enzymes involved in cellulose degradation. We have used our recently developed quantitative, angle-scanning surface plasmon resonance imaging (SPRi) device to study the degradation of cellulose microfibrils upon exposure to cellulosic enzymes. In particular, we have studied the action of individual enzymes, and combinations of enzymes, from the Hypocrea Jecorina cellulase system on heterogeneous, industrially-relevant cellulose substrates. This has allowed us to define a characteristic time of action for the enzymes for different degrees of surface coverage of the cellulose microfibrils.

A Structural Study of CESA1 Catalytic Domain of Arabidopsis Cellulose Synthesis Complex: Evidence for CESA Trimers.

PubMed

Vandavasi, Venu Gopal; Putnam, Daniel K; Zhang, Qiu; Petridis, Loukas; Heller, William T; Nixon, B Tracy; Haigler, Candace H; Kalluri, Udaya; Coates, Leighton; Langan, Paul; Smith, Jeremy C; Meiler, Jens; O'Neill, Hugh

2016-01-01

A cellulose synthesis complex with a "rosette" shape is responsible for synthesis of cellulose chains and their assembly into microfibrils within the cell walls of land plants and their charophyte algal progenitors. The number of cellulose synthase proteins in this large multisubunit transmembrane protein complex and the number of cellulose chains in a microfibril have been debated for many years. This work reports a low resolution structure of the catalytic domain of CESA1 from Arabidopsis (Arabidopsis thaliana; AtCESA1CatD) determined by small-angle scattering techniques and provides the first experimental evidence for the self-assembly of CESA into a stable trimer in solution. The catalytic domain was overexpressed in Escherichia coli, and using a two-step procedure, it was possible to isolate monomeric and trimeric forms of AtCESA1CatD. The conformation of monomeric and trimeric AtCESA1CatD proteins were studied using small-angle neutron scattering and small-angle x-ray scattering. A series of AtCESA1CatD trimer computational models were compared with the small-angle x-ray scattering trimer profile to explore the possible arrangement of the monomers in the trimers. Several candidate trimers were identified with monomers oriented such that the newly synthesized cellulose chains project toward the cell membrane. In these models, the class-specific region is found at the periphery of the complex, and the plant-conserved region forms the base of the trimer. This study strongly supports the "hexamer of trimers" model for the rosette cellulose synthesis complex that synthesizes an 18-chain cellulose microfibril as its fundamental product. © 2016 American Society of Plant Biologists. All Rights Reserved.

A Structural Study of CESA1 Catalytic Domain of Arabidopsis Cellulose Synthesis Complex: Evidence for CESA Trimers1

PubMed Central

Zhang, Qiu; Petridis, Loukas; Nixon, B. Tracy; Haigler, Candace H.; Kalluri, Udaya; Coates, Leighton; Smith, Jeremy C.; Meiler, Jens

2016-01-01

A cellulose synthesis complex with a “rosette” shape is responsible for synthesis of cellulose chains and their assembly into microfibrils within the cell walls of land plants and their charophyte algal progenitors. The number of cellulose synthase proteins in this large multisubunit transmembrane protein complex and the number of cellulose chains in a microfibril have been debated for many years. This work reports a low resolution structure of the catalytic domain of CESA1 from Arabidopsis (Arabidopsis thaliana; AtCESA1CatD) determined by small-angle scattering techniques and provides the first experimental evidence for the self-assembly of CESA into a stable trimer in solution. The catalytic domain was overexpressed in Escherichia coli, and using a two-step procedure, it was possible to isolate monomeric and trimeric forms of AtCESA1CatD. The conformation of monomeric and trimeric AtCESA1CatD proteins were studied using small-angle neutron scattering and small-angle x-ray scattering. A series of AtCESA1CatD trimer computational models were compared with the small-angle x-ray scattering trimer profile to explore the possible arrangement of the monomers in the trimers. Several candidate trimers were identified with monomers oriented such that the newly synthesized cellulose chains project toward the cell membrane. In these models, the class-specific region is found at the periphery of the complex, and the plant-conserved region forms the base of the trimer. This study strongly supports the “hexamer of trimers” model for the rosette cellulose synthesis complex that synthesizes an 18-chain cellulose microfibril as its fundamental product. PMID:26556795

A Structural Study of CESA1 Catalytic Domain of Arabidopsis Cellulose Synthesis Complex: Evidence for CESA Trimers

DOE PAGES

Vandavasi, Venu Gopal; Putnam, Daniel K.; Zhang, Qiu; ...

2015-11-10

In a cellulose synthesis complex a "rosette" shape is responsible for the synthesis of cellulose chains and their assembly into microfibrils within the cell walls of land plants and their charophyte algal progenitors. The number of cellulose synthase proteins in this large multisubunit transmembrane protein complex and the number of cellulose chains in a microfibril have been debated for many years. Our work reports a low resolution structure of the catalytic domain of CESA1 from Arabidopsis (Arabidopsis thaliana; AtCESA1CatD) determined by small-angle scattering techniques and provides the first experimental evidence for the self-assembly of CESA into a stable trimer inmore » solution. The catalytic domain was overexpressed in Escherichia coli, and using a two-step procedure, it was possible to isolate monomeric and trimeric forms of AtCESA1CatD. Moreover, the conformation of monomeric and trimeric AtCESA1CatD proteins were studied using small-angle neutron scattering and small-angle x-ray scattering. A series of AtCESA1CatD trimer computational models were compared with the small-angle x-ray scattering trimer profile to explore the possible arrangement of the monomers in the trimers. Several candidate trimers were identified with monomers oriented such that the newly synthesized cellulose chains project toward the cell membrane. In these models, the class-specific region is found at the periphery of the complex, and the plant-conserved region forms the base of the trimer. Finally, this study strongly supports the "hexamer of trimers" model for the rosette cellulose synthesis complex that synthesizes an 18-chain cellulose microfibril as its fundamental product.« less

Periodic disorder along ramie cellulose microfibrils.

PubMed

Nishiyama, Yoshiharu; Kim, Ung-Jin; Kim, Dae-Young; Katsumata, Kyoko S; May, Roland P; Langan, Paul

2003-01-01

Small angle neutron scattering studies have been carried out on cellulose fibers from ramie and Populus maximowicii (cotton wood). Labile hydrogen atoms were replaced by deuterium atoms, in water-accessible disordered regions of the fibers, to increase the neutron scattering contrast between the disordered and crystalline regions. A meridional Bragg reflection, corresponding to a longitudinal periodicity of 150 nm, was observed when scattering collected from hydrogenated and deuterated dry ramie fibers was subtracted. No Bragg reflection was observed with the cotton wood fibers, probably because of lower orientation of the microfibrils in the cell wall. The ramie fibers were then subjected to electron microscopy, acid hydrolysis, gel permeation chromatography, and viscosity studies. The leveling off degree of polymerization (LODP) of the hydrolyzed samples matched exactly the periodicity observed in the diffraction studies. The weight loss related to the LODP was only about 1.5%, and thus, the microfibrils can be considered to have 4-5 disordered residues every 300 residues.

Synergy between cellulolytic enzymes during the biodegradation of cellulose microfibrils measured using angle-scanning surface plasmon resonance (SPR) imaging

NASA Astrophysics Data System (ADS)

Raegen, Adam; Dion, Alexander; Reiter, Kyle; Clarke, Anthony; Lipkowski, Jacek; Dutcher, John

2014-03-01

The use of cellulosic ethanol, a promising emerging energy source, is limited by the energy intensive and costly step of first converting the cellulose fibers into their constituent glucose monomers. Industrial processes mimic those that occur in nature, using mixtures or ``cocktails'' of different classes of cellulolytic enzymes derived from fungi. Despite several decades of investigation, the molecular mechanisms for enzyme synergy remain poorly understood. To gain additional insight, we have used a custom angle-scanning surface plasmon resonance (SPR) imaging apparatus to obtain a sensitive measure of enzymatic degradation. By implementing a novel SPR data analysis procedure, we have been able to track the thickness and roughness of laterally heterogeneous cellulose microfibril-coated substrates as enzymatic degradation proceeds. This has allowed us to measure the synergistic actions of the different enzymes, providing data that are directly relevant to the cellulosic ethanol industry.

The supramolecular structure of bone: X-ray scattering analysis and lateral structure modeling

PubMed Central

Zhou, Hong-Wen; Burger, Christian; Wang, Hao; Hsiao, Benjamin S.; Chu, Benjamin; Graham, Lila

2016-01-01

The evolution of vertebrates required a key development in supramolecular evolution: internally mineralized collagen fibrils. In bone, collagen molecules and mineral crystals form a nanocomposite material comparable to cast iron in tensile strength, but several times lighter and more flexible. Current understanding of the internal nanoscale structure of collagen fibrils, derived from studies of rat tail tendon (RTT), does not explain how nucleation and growth of mineral crystals can occur inside a collagen fibril. Experimental obstacles encountered in studying bone have prevented a solution to this problem for several decades. This report presents a lateral packing model for collagen molecules in bone fibrils, based on the unprecedented observation of multiple resolved equatorial reflections for bone tissue using synchrotron small-angle X-ray scattering (SAXS; ∼1 nm resolution). The deduced structure for pre-mineralized bone fibrils includes features that are not present in RTT: spatially discrete microfibrils. The data are consistent with bone microfibrils similar to pentagonal Smith microfibrils, but are not consistent with the (nondiscrete) quasi-hexagonal microfibrils reported for RTT. These results indicate that collagen fibrils in bone and tendon differ in their internal structure in a manner that allows bone fibrils, but not tendon fibrils, to internally mineralize. In addition, the unique pattern of collagen cross-link types and quantities in mineralized tissues can be can be accounted for, in structural/functional terms, based on a discrete microfibril model. PMID:27599731

Folding of xylan onto cellulose fibrils in plant cell walls revealed by solid-state NMR

NASA Astrophysics Data System (ADS)

Simmons, Thomas J.; Mortimer, Jenny C.; Bernardinelli, Oigres D.; Pöppler, Ann-Christin; Brown, Steven P.; Deazevedo, Eduardo R.; Dupree, Ray; Dupree, Paul

2016-12-01

Exploitation of plant lignocellulosic biomass is hampered by our ignorance of the molecular basis for its properties such as strength and digestibility. Xylan, the most prevalent non-cellulosic polysaccharide, binds to cellulose microfibrils. The nature of this interaction remains unclear, despite its importance. Here we show that the majority of xylan, which forms a threefold helical screw in solution, flattens into a twofold helical screw ribbon to bind intimately to cellulose microfibrils in the cell wall. 13C solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, supported by in silico predictions of chemical shifts, shows both two- and threefold screw xylan conformations are present in fresh Arabidopsis stems. The twofold screw xylan is spatially close to cellulose, and has similar rigidity to the cellulose microfibrils, but reverts to the threefold screw conformation in the cellulose-deficient irx3 mutant. The discovery that induced polysaccharide conformation underlies cell wall assembly provides new principles to understand biomass properties.

Cellulose microfibrils grafted with PBA via surface-initiated atom transfer radical polymerization for biocomposite reinforcement.

PubMed

Li, Shuzhao; Xiao, Miaomiao; Zheng, Anna; Xiao, Huining

2011-09-12

Immobilizing poly(butyl acrylate) (PBA) on cellulose microfibrils (CMFs) by atom transfer radical polymerization (ATRP) of butyl acrylate (BA) on the surface of 2-bromoisobutyryl-functionalized CMF generated highly hydrophobic microfibrils (CMF-PBA) with a hard core and a soft-shell structure. TGA and static water contact angle results suggested that the surfaces of the modified CMF samples were not completely covered by PBA chains until the molecular weight of grafts became sufficiently long. The GPC results indicated that the grafts with low molecular weight showed controlled/"living" characteristics of the surface-initiated ATRP; however, there existed more side reactions with the increase in molecular weights. Biocomposites consisting of polypropylene (PP) and CMF-PBA samples exhibited significantly improved compatibility, interface adhesion, and mechanical properties with the increase in PBA graft length. The findings confirmed that the longer grafts facilitated the better entanglement of PBA grafts with PP macromolecules and thus further improved the mechanical properties.

Folding of xylan onto cellulose fibrils in plant cell walls revealed by solid-state NMR.

PubMed

Simmons, Thomas J; Mortimer, Jenny C; Bernardinelli, Oigres D; Pöppler, Ann-Christin; Brown, Steven P; deAzevedo, Eduardo R; Dupree, Ray; Dupree, Paul

2016-12-21

Exploitation of plant lignocellulosic biomass is hampered by our ignorance of the molecular basis for its properties such as strength and digestibility. Xylan, the most prevalent non-cellulosic polysaccharide, binds to cellulose microfibrils. The nature of this interaction remains unclear, despite its importance. Here we show that the majority of xylan, which forms a threefold helical screw in solution, flattens into a twofold helical screw ribbon to bind intimately to cellulose microfibrils in the cell wall. 13 C solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, supported by in silico predictions of chemical shifts, shows both two- and threefold screw xylan conformations are present in fresh Arabidopsis stems. The twofold screw xylan is spatially close to cellulose, and has similar rigidity to the cellulose microfibrils, but reverts to the threefold screw conformation in the cellulose-deficient irx3 mutant. The discovery that induced polysaccharide conformation underlies cell wall assembly provides new principles to understand biomass properties.

Chitinase-like1/pom-pom1 and its homolog CTL2 are glucan-interacting proteins important for cellulose biosynthesis in Arabidopsis.

PubMed

Sánchez-Rodríguez, Clara; Bauer, Stefan; Hématy, Kian; Saxe, Friederike; Ibáñez, Ana Belén; Vodermaier, Vera; Konlechner, Cornelia; Sampathkumar, Arun; Rüggeberg, Markus; Aichinger, Ernst; Neumetzler, Lutz; Burgert, Ingo; Somerville, Chris; Hauser, Marie-Theres; Persson, Staffan

2012-02-01

Plant cells are encased by a cellulose-containing wall that is essential for plant morphogenesis. Cellulose consists of β-1,4-linked glucan chains assembled into paracrystalline microfibrils that are synthesized by plasma membrane-located cellulose synthase (CESA) complexes. Associations with hemicelluloses are important for microfibril spacing and for maintaining cell wall tensile strength. Several components associated with cellulose synthesis have been identified; however, the biological functions for many of them remain elusive. We show that the chitinase-like (CTL) proteins, CTL1/POM1 and CTL2, are functionally equivalent, affect cellulose biosynthesis, and are likely to play a key role in establishing interactions between cellulose microfibrils and hemicelluloses. CTL1/POM1 coincided with CESAs in the endomembrane system and was secreted to the apoplast. The movement of CESAs was compromised in ctl1/pom1 mutant seedlings, and the cellulose content and xyloglucan structures were altered. X-ray analysis revealed reduced crystalline cellulose content in ctl1 ctl2 double mutants, suggesting that the CTLs cooperatively affect assembly of the glucan chains, which may affect interactions between hemicelluloses and cellulose. Consistent with this hypothesis, both CTLs bound glucan-based polymers in vitro. We propose that the apoplastic CTLs regulate cellulose assembly and interaction with hemicelluloses via binding to emerging cellulose microfibrils.

CHITINASE-LIKE1/POM-POM1 and Its Homolog CTL2 Are Glucan-Interacting Proteins Important for Cellulose Biosynthesis in Arabidopsis[W][OA

PubMed Central

Sánchez-Rodríguez, Clara; Bauer, Stefan; Hématy, Kian; Saxe, Friederike; Ibáñez, Ana Belén; Vodermaier, Vera; Konlechner, Cornelia; Sampathkumar, Arun; Rüggeberg, Markus; Aichinger, Ernst; Neumetzler, Lutz; Burgert, Ingo; Somerville, Chris; Hauser, Marie-Theres; Persson, Staffan

2012-01-01

Plant cells are encased by a cellulose-containing wall that is essential for plant morphogenesis. Cellulose consists of β-1,4-linked glucan chains assembled into paracrystalline microfibrils that are synthesized by plasma membrane–located cellulose synthase (CESA) complexes. Associations with hemicelluloses are important for microfibril spacing and for maintaining cell wall tensile strength. Several components associated with cellulose synthesis have been identified; however, the biological functions for many of them remain elusive. We show that the chitinase-like (CTL) proteins, CTL1/POM1 and CTL2, are functionally equivalent, affect cellulose biosynthesis, and are likely to play a key role in establishing interactions between cellulose microfibrils and hemicelluloses. CTL1/POM1 coincided with CESAs in the endomembrane system and was secreted to the apoplast. The movement of CESAs was compromised in ctl1/pom1 mutant seedlings, and the cellulose content and xyloglucan structures were altered. X-ray analysis revealed reduced crystalline cellulose content in ctl1 ctl2 double mutants, suggesting that the CTLs cooperatively affect assembly of the glucan chains, which may affect interactions between hemicelluloses and cellulose. Consistent with this hypothesis, both CTLs bound glucan-based polymers in vitro. We propose that the apoplastic CTLs regulate cellulose assembly and interaction with hemicelluloses via binding to emerging cellulose microfibrils. PMID:22327741

Transcriptome profiling of Pinus radiata juvenile wood with contrasting stiffness identifies putative candidate genes involved in microfibril orientation and cell wall mechanics

PubMed Central

2011-01-01

Background The mechanical properties of wood are largely determined by the orientation of cellulose microfibrils in secondary cell walls. Several genes and their allelic variants have previously been found to affect microfibril angle (MFA) and wood stiffness; however, the molecular mechanisms controlling microfibril orientation and mechanical strength are largely uncharacterised. In the present study, cDNA microarrays were used to compare gene expression in developing xylem with contrasting stiffness and MFA in juvenile Pinus radiata trees in order to gain further insights into the molecular mechanisms underlying microfibril orientation and cell wall mechanics. Results Juvenile radiata pine trees with higher stiffness (HS) had lower MFA in the earlywood and latewood of each ring compared to low stiffness (LS) trees. Approximately 3.4 to 14.5% out of 3, 320 xylem unigenes on cDNA microarrays were differentially regulated in juvenile wood with contrasting stiffness and MFA. Greater variation in MFA and stiffness was observed in earlywood compared to latewood, suggesting earlywood contributes most to differences in stiffness; however, 3-4 times more genes were differentially regulated in latewood than in earlywood. A total of 108 xylem unigenes were differentially regulated in juvenile wood with HS and LS in at least two seasons, including 43 unigenes with unknown functions. Many genes involved in cytoskeleton development and secondary wall formation (cellulose and lignin biosynthesis) were preferentially transcribed in wood with HS and low MFA. In contrast, several genes involved in cell division and primary wall synthesis were more abundantly transcribed in LS wood with high MFA. Conclusions Microarray expression profiles in Pinus radiata juvenile wood with contrasting stiffness has shed more light on the transcriptional control of microfibril orientation and the mechanical properties of wood. The identified candidate genes provide an invaluable resource for further gene function and association genetics studies aimed at deepening our understanding of cell wall biomechanics with a view to improving the mechanical properties of wood. PMID:21962175

Earlywood and latewood elastic properties in loblolly pine

Treesearch

Steven Cramer; David Kretschmann; Roderic Lakes; Troy Schmidt

2005-01-01

The elastic properties of earlywood and latewood and their variability were measured in 388 specimens from six loblolly pine trees in a commercial plantation. Properties measured included longitudinal modulus of elasticity, shear modulus, specific gravity, microfibril angle and presence of compression wood. Novel testing procedures were developed to measure properties...

Aspen Tension Wood Fibers Contain β-(1→4)-Galactans and Acidic Arabinogalactans Retained by Cellulose Microfibrils in Gelatinous Walls1[OPEN

PubMed Central

Gorshkova, Tatyana; Mokshina, Natalia; Chernova, Tatyana; Ibragimova, Nadezhda; Salnikov, Vadim; Mikshina, Polina; Tryfona, Theodora; Banasiak, Alicja; Immerzeel, Peter; Dupree, Paul; Mellerowicz, Ewa J.

2015-01-01

Contractile cell walls are found in various plant organs and tissues such as tendrils, contractile roots, and tension wood. The tension-generating mechanism is not known but is thought to involve special cell wall architecture. We previously postulated that tension could result from the entrapment of certain matrix polymers within cellulose microfibrils. As reported here, this hypothesis was corroborated by sequential extraction and analysis of cell wall polymers that are retained by cellulose microfibrils in tension wood and normal wood of hybrid aspen (Populus tremula × Populus tremuloides). β-(1→4)-Galactan and type II arabinogalactan were the main large matrix polymers retained by cellulose microfibrils that were specifically found in tension wood. Xyloglucan was detected mostly in oligomeric form in the alkali-labile fraction and was enriched in tension wood. β-(1→4)-Galactan and rhamnogalacturonan I backbone epitopes were localized in the gelatinous cell wall layer. Type II arabinogalactans retained by cellulose microfibrils had a higher content of (methyl)glucuronic acid and galactose in tension wood than in normal wood. Thus, β-(1→4)-galactan and a specialized form of type II arabinogalactan are trapped by cellulose microfibrils specifically in tension wood and, thus, are the main candidate polymers for the generation of tensional stresses by the entrapment mechanism. We also found high β-galactosidase activity accompanying tension wood differentiation and propose a testable hypothesis that such activity might regulate galactan entrapment and, thus, mechanical properties of cell walls in tension wood. PMID:26378099

Aspen Tension Wood Fibers Contain β-(1---> 4)-Galactans and Acidic Arabinogalactans Retained by Cellulose Microfibrils in Gelatinous Walls.

PubMed

Gorshkova, Tatyana; Mokshina, Natalia; Chernova, Tatyana; Ibragimova, Nadezhda; Salnikov, Vadim; Mikshina, Polina; Tryfona, Theodora; Banasiak, Alicja; Immerzeel, Peter; Dupree, Paul; Mellerowicz, Ewa J

2015-11-01

Contractile cell walls are found in various plant organs and tissues such as tendrils, contractile roots, and tension wood. The tension-generating mechanism is not known but is thought to involve special cell wall architecture. We previously postulated that tension could result from the entrapment of certain matrix polymers within cellulose microfibrils. As reported here, this hypothesis was corroborated by sequential extraction and analysis of cell wall polymers that are retained by cellulose microfibrils in tension wood and normal wood of hybrid aspen (Populus tremula × Populus tremuloides). β-(1→4)-Galactan and type II arabinogalactan were the main large matrix polymers retained by cellulose microfibrils that were specifically found in tension wood. Xyloglucan was detected mostly in oligomeric form in the alkali-labile fraction and was enriched in tension wood. β-(1→4)-Galactan and rhamnogalacturonan I backbone epitopes were localized in the gelatinous cell wall layer. Type II arabinogalactans retained by cellulose microfibrils had a higher content of (methyl)glucuronic acid and galactose in tension wood than in normal wood. Thus, β-(1→4)-galactan and a specialized form of type II arabinogalactan are trapped by cellulose microfibrils specifically in tension wood and, thus, are the main candidate polymers for the generation of tensional stresses by the entrapment mechanism. We also found high β-galactosidase activity accompanying tension wood differentiation and propose a testable hypothesis that such activity might regulate galactan entrapment and, thus, mechanical properties of cell walls in tension wood. © 2015 American Society of Plant Biologists. All Rights Reserved.

Mechanism for Tuning the Hydrophobicity of Microfibrillated Cellulose Films by Controlled Thermal Release of Encapsulated Wax

PubMed Central

Rastogi, Vibhore Kumar; Stanssens, Dirk; Samyn, Pieter

2014-01-01

Although films of microfibrillated cellulose (MFC) have good oxygen barrier properties due to its fine network structure, properties strongly deteriorate after absorption of water. In this work, a new approach has been followed for actively tuning the water resistance of a MFC fiber network by the inclusion of dispersed organic nanoparticles with encapsulated plant wax. The modified pulp suspensions have been casted into films and were subsequently cured at 40 to 220 °C. As such, static water contact angles can be specifically tuned from 120 to 150° by selection of the curing temperature in relation with the intrinsic transition temperatures of the modified pulp, as determined by thermal analysis. The appearance of encapsulated wax after curing was followed by a combination of morphological analysis, infrared spectroscopy and Raman mapping, showing balanced mechanisms of progressive release and migration of wax into the fiber network controlling the surface properties and water contact angles. Finally, the appearance of nanoparticles covered with a thin wax layer after complete thermal release provides highest hydrophobicity. PMID:28788241

Exploiting CELLULOSE SYNTHASE (CESA) Class Specificity to Probe Cellulose Microfibril Biosynthesis.

PubMed

Kumar, Manoj; Mishra, Laxmi; Carr, Paul; Pilling, Michael; Gardner, Peter; Mansfield, Shawn D; Turner, Simon

2018-05-01

Cellulose microfibrils are the basic units of cellulose in plants. The structure of these microfibrils is at least partly determined by the structure of the cellulose synthase complex. In higher plants, this complex is composed of 18 to 24 catalytic subunits known as CELLULOSE SYNTHASE A (CESA) proteins. Three different classes of CESA proteins are required for cellulose synthesis and for secondary cell wall cellulose biosynthesis these classes are represented by CESA4, CESA7, and CESA8. To probe the relationship between CESA proteins and microfibril structure, we created mutant cesa proteins that lack catalytic activity but retain sufficient structural integrity to allow assembly of the cellulose synthase complex. Using a series of Arabidopsis ( Arabidopsis thaliana ) mutants and genetic backgrounds, we found consistent differences in the ability of these mutant cesa proteins to complement the cellulose-deficient phenotype of the cesa null mutants. The best complementation was observed with catalytically inactive cesa4, while the equivalent mutation in cesa8 exhibited significantly lower levels of complementation. Using a variety of biophysical techniques, including solid-state nuclear magnetic resonance and Fourier transform infrared microscopy, to study these mutant plants, we found evidence for changes in cellulose microfibril structure, but these changes largely correlated with cellulose content and reflected differences in the relative proportions of primary and secondary cell walls. Our results suggest that individual CESA classes have similar roles in determining cellulose microfibril structure, and it is likely that the different effects of mutating members of different CESA classes are the consequence of their different catalytic activity and their influence on the overall rate of cellulose synthesis. © 2018 American Society of Plant Biologists. All Rights Reserved.

Exploiting CELLULOSE SYNTHASE (CESA) Class Specificity to Probe Cellulose Microfibril Biosynthesis1[OPEN

PubMed Central

Mishra, Laxmi; Carr, Paul; Gardner, Peter

2018-01-01

Cellulose microfibrils are the basic units of cellulose in plants. The structure of these microfibrils is at least partly determined by the structure of the cellulose synthase complex. In higher plants, this complex is composed of 18 to 24 catalytic subunits known as CELLULOSE SYNTHASE A (CESA) proteins. Three different classes of CESA proteins are required for cellulose synthesis and for secondary cell wall cellulose biosynthesis these classes are represented by CESA4, CESA7, and CESA8. To probe the relationship between CESA proteins and microfibril structure, we created mutant cesa proteins that lack catalytic activity but retain sufficient structural integrity to allow assembly of the cellulose synthase complex. Using a series of Arabidopsis (Arabidopsis thaliana) mutants and genetic backgrounds, we found consistent differences in the ability of these mutant cesa proteins to complement the cellulose-deficient phenotype of the cesa null mutants. The best complementation was observed with catalytically inactive cesa4, while the equivalent mutation in cesa8 exhibited significantly lower levels of complementation. Using a variety of biophysical techniques, including solid-state nuclear magnetic resonance and Fourier transform infrared microscopy, to study these mutant plants, we found evidence for changes in cellulose microfibril structure, but these changes largely correlated with cellulose content and reflected differences in the relative proportions of primary and secondary cell walls. Our results suggest that individual CESA classes have similar roles in determining cellulose microfibril structure, and it is likely that the different effects of mutating members of different CESA classes are the consequence of their different catalytic activity and their influence on the overall rate of cellulose synthesis. PMID:29523715

Effective Young's modulus of bacterial and microfibrillated cellulose fibrils in fibrous networks.

PubMed

Tanpichai, Supachok; Quero, Franck; Nogi, Masaya; Yano, Hiroyuki; Young, Robert J; Lindström, Tom; Sampson, William W; Eichhorn, Stephen J

2012-05-14

The deformation micromechanics of bacterial cellulose (BC) and microfibrillated cellulose (MFC) networks have been investigated using Raman spectroscopy. The Raman spectra of both BC and MFC networks exhibit a band initially located at ≈ 1095 cm(-1). We have used the intensity of this band as a function of rotation angle of the specimens to study the cellulose fibril orientation in BC and MFC networks. We have also used the change in this peak's wavenumber position with applied tensile deformation to probe the stress-transfer behavior of these cellulosic materials. The intensity of this Raman band did not change significantly with rotation angle, indicating an in-plane 2D network of fibrils with uniform random orientation; conversely, a highly oriented flax fiber exhibited a marked change in intensity with rotation angle. Experimental data and theoretical analysis shows that the Raman band shift rate arising from deformation of networks under tension is dependent on the angles between the axis of fibrils, the strain axis, the incident laser polarization direction, and the back scattered polarization configurations. From this analysis, the effective moduli of single fibrils of BC and MFC in the networks were estimated to be in the ranges of 79-88 and 29-36 GPa, respectively. It is shown also that for the model to fit the data it is necessary to use a negative Poisson's ratio for MFC networks and BC networks. Discussion of this in-plane "auxetic" behavior is given.

Impact of the foliar pathogen Swiss needle cast on wood quality of Douglas-fir.

Treesearch

G.R. Johnson; Amy T. Grotta; Barbara L. Gartner; Geoff. Downes

2005-01-01

Many stands of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) near coastal areas of Oregon and Washington are heavily infected with the foliar pathogen causing Swiss needle cast (SNC) disease, and yet there is very little research on the resulting wood quality. Modulus of elasticity(MOE), modulus of rupture (MOR), microfibril angle (MFA), wood...

Maturation Stress Generation in Poplar Tension Wood Studied by Synchrotron Radiation Microdiffraction[C][W][OA

PubMed Central

Clair, Bruno; Alméras, Tancrède; Pilate, Gilles; Jullien, Delphine; Sugiyama, Junji; Riekel, Christian

2011-01-01

Tension wood is widespread in the organs of woody plants. During its formation, it generates a large tensile mechanical stress called maturation stress. Maturation stress performs essential biomechanical functions such as optimizing the mechanical resistance of the stem, performing adaptive movements, and ensuring the long-term stability of growing plants. Although various hypotheses have recently been proposed, the mechanism generating maturation stress is not yet fully understood. In order to discriminate between these hypotheses, we investigated structural changes in cellulose microfibrils along sequences of xylem cell differentiation in tension and normal wood of poplar (Populus deltoides × Populus trichocarpa ‘I45-51’). Synchrotron radiation microdiffraction was used to measure the evolution of the angle and lattice spacing of crystalline cellulose associated with the deposition of successive cell wall layers. Profiles of normal and tension wood were very similar in early development stages corresponding to the formation of the S1 layer and the outer part of the S2 layer. Subsequent layers were found with a lower microfibril angle (MFA), corresponding to the inner part of the S2 layer of normal wood (MFA approximately 10°) and the G layer of tension wood (MFA approximately 0°). In tension wood only, this steep decrease in MFA occurred together with an increase in cellulose lattice spacing. The relative increase in lattice spacing was found close to the usual value of maturation strains. Analysis showed that this increase in lattice spacing is at least partly due to mechanical stress induced in cellulose microfibrils soon after their deposition, suggesting that the G layer directly generates and supports the tensile maturation stress in poplar tension wood. PMID:21068364

Advances in Surface Plasmon Resonance Imaging allowing for quantitative measurement of laterally heterogeneous samples

NASA Astrophysics Data System (ADS)

Raegen, Adam; Reiter, Kyle; Clarke, Anthony; Lipkowski, Jacek; Dutcher, John

2012-02-01

The Surface Plasmon Resonance (SPR) phenomenon is routinely exploited to qualitatively probe changes to materials on metallic surfaces for use in probes and sensors. Unfortunately, extracting truly quantitative information is usually limited to a select few cases -- uniform absorption/desorption of small biomolecules and films, in which a continuous ``slab'' model is a good approximation. We present advancements in the SPR technique that expand the number of cases for which the technique can provide meaningful results. Use of a custom, angle-scanning SPR imaging system, together with a refined data analysis method, allow for quantitative kinetic measurements of laterally heterogeneous systems. The degradation of cellulose microfibrils and bundles of microfibrils due to the action of cellulolytic enzymes will be presented as an excellent example of the capabilities of the SPR imaging system.

On the alignment of cellulose microfibrils by cortical microtubules: a review and a model.

PubMed

Baskin, T I

2001-01-01

The hypothesis that microtubules align microfibrils, termed the alignment hypothesis, states that there is a causal link between the orientation of cortical microtubules and the orientation of nascent microfibrils. I have assessed the generality of this hypothesis by reviewing what is known about the relation between microtubules and microfibrils in a wide group of examples: in algae of the family Characeae, Closterium acerosum, Oocystis solitaria, and certain genera of green coenocytes and in land plant tip-growing cells, xylem, diffusely growing cells, and protoplasts. The salient features about microfibril alignment to emerge are as follows. Cellulose microfibrils can be aligned by cortical microtubules, thus supporting the alignment hypothesis. Alignment of microfibrils can occur independently of microtubules, showing that an alternative to the alignment hypothesis must exist. Microfibril organization is often random, suggesting that self-assembly is insufficient. Microfibril organization differs on different faces of the same cell, suggesting that microfibrils are aligned locally, not with respect to the entire cell. Nascent microfibrils appear to associate tightly with the plasma membrane. To account for these observations, I present a model that posits alignment to be mediated through binding the nascent microfibril. The model, termed templated incorporation, postulates that the nascent microfibril is incorporated into the cell wall by binding to a scaffold that is oriented; further, the scaffold is built and oriented around either already incorporated microfibrils or plasma membrane proteins, or both. The role of cortical microtubules is to bind and orient components of the scaffold at the plasma membrane. In this way, spatial information to align the microfibrils may come from either the cell wall or the cell interior, and microfibril alignment with and without microtubules are subsets of a single mechanism.

Moisture changes in the plant cell wall force cellulose crystallites to deform.

PubMed

Zabler, S; Paris, O; Burgert, I; Fratzl, P

2010-08-01

Nano-crystallite deformation of cellulose microfibrils in the secondary cell wall layer of spruce wood tracheids was observed during de- and rehydration experiments below the fibre saturation point. A quantitative analysis of the (004), (200) and the (110)/(11 0) doublet X-ray diffraction peaks revealed longitudinal contraction, lateral expansion and changes in the monoclinic angle of the cellulose unit cell during drying of wood fibres. Experiments on unfixed samples as well as the simultaneous application of mechanical tensile and dehydration stress to samples hold at constant length showed two deformation mechanisms of different nature and magnitude. The first mechanism depends on the relative wood moisture content and the second one on the macroscopic tensile stress. These findings imply a new perspective on the role of water adsorption perceiving a hydration-induced structural change of cellulose crystal structure as a major driving force for deformation. Copyright 2010 Elsevier Inc. All rights reserved.

Comparative structural and computational analysis supports eighteen cellulose synthases in the plant cellulose synthesis complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nixon, B. Tracy; Mansouri, Katayoun; Singh, Abhishek

A six-lobed membrane spanning cellulose synthesis complex (CSC) containing multiple cellulose synthase (CESA) glycosyltransferases mediates cellulose microfibril formation. The number of CESAs in the CSC has been debated for decades in light of changing estimates of the diameter of the smallest microfibril formed from the β-1,4 glucan chains synthesized by one CSC. We obtained more direct evidence through generating improved transmission electron microscopy (TEM) images and image averages of the rosette-type CSC, revealing the frequent triangularity and average cross-sectional area in the plasma membrane of its individual lobes. Trimeric oligomers of two alternative CESA computational models corresponded well with individualmore » lobe geometry. A six-fold assembly of the trimeric computational oligomer had the lowest potential energy per monomer and was consistent with rosette CSC morphology. Negative stain TEM and image averaging showed the triangularity of a recombinant CESA cytosolic domain, consistent with previous modeling of its trimeric nature from small angle scattering (SAXS) data. Six trimeric SAXS models nearly filled the space below an average FF-TEM image of the rosette CSC. In conclusion, the multifaceted data support a rosette CSC with 18 CESAs that mediates the synthesis of a fundamental microfibril composed of 18 glucan chains.« less

Comparative structural and computational analysis supports eighteen cellulose synthases in the plant cellulose synthesis complex

DOE PAGES

Nixon, B. Tracy; Mansouri, Katayoun; Singh, Abhishek; ...

2016-06-27

A six-lobed membrane spanning cellulose synthesis complex (CSC) containing multiple cellulose synthase (CESA) glycosyltransferases mediates cellulose microfibril formation. The number of CESAs in the CSC has been debated for decades in light of changing estimates of the diameter of the smallest microfibril formed from the β-1,4 glucan chains synthesized by one CSC. We obtained more direct evidence through generating improved transmission electron microscopy (TEM) images and image averages of the rosette-type CSC, revealing the frequent triangularity and average cross-sectional area in the plasma membrane of its individual lobes. Trimeric oligomers of two alternative CESA computational models corresponded well with individualmore » lobe geometry. A six-fold assembly of the trimeric computational oligomer had the lowest potential energy per monomer and was consistent with rosette CSC morphology. Negative stain TEM and image averaging showed the triangularity of a recombinant CESA cytosolic domain, consistent with previous modeling of its trimeric nature from small angle scattering (SAXS) data. Six trimeric SAXS models nearly filled the space below an average FF-TEM image of the rosette CSC. In conclusion, the multifaceted data support a rosette CSC with 18 CESAs that mediates the synthesis of a fundamental microfibril composed of 18 glucan chains.« less

Comparative Structural and Computational Analysis Supports Eighteen Cellulose Synthases in the Plant Cellulose Synthesis Complex

PubMed Central

Nixon, B. Tracy; Mansouri, Katayoun; Singh, Abhishek; Du, Juan; Davis, Jonathan K.; Lee, Jung-Goo; Slabaugh, Erin; Vandavasi, Venu Gopal; O’Neill, Hugh; Roberts, Eric M.; Roberts, Alison W.; Yingling, Yaroslava G.; Haigler, Candace H.

2016-01-01

A six-lobed membrane spanning cellulose synthesis complex (CSC) containing multiple cellulose synthase (CESA) glycosyltransferases mediates cellulose microfibril formation. The number of CESAs in the CSC has been debated for decades in light of changing estimates of the diameter of the smallest microfibril formed from the β-1,4 glucan chains synthesized by one CSC. We obtained more direct evidence through generating improved transmission electron microscopy (TEM) images and image averages of the rosette-type CSC, revealing the frequent triangularity and average cross-sectional area in the plasma membrane of its individual lobes. Trimeric oligomers of two alternative CESA computational models corresponded well with individual lobe geometry. A six-fold assembly of the trimeric computational oligomer had the lowest potential energy per monomer and was consistent with rosette CSC morphology. Negative stain TEM and image averaging showed the triangularity of a recombinant CESA cytosolic domain, consistent with previous modeling of its trimeric nature from small angle scattering (SAXS) data. Six trimeric SAXS models nearly filled the space below an average FF-TEM image of the rosette CSC. In summary, the multifaceted data support a rosette CSC with 18 CESAs that mediates the synthesis of a fundamental microfibril composed of 18 glucan chains. PMID:27345599

Coarse-Grained Simulation of Solvated Cellulose Ib Microfibril

NASA Astrophysics Data System (ADS)

Fan, Bingxin; Maranas, Janna; Zhong, Linghao; Zhen Zhao Collaboration

2013-03-01

We construct a coarse-grained (CG) model of cellulose microfibrils in water. The force field is derived from atomistic simulation of a 40 glucose-unit-long microfibril by requiring consistency between the chain configuration, intermolecular packing and hydrogen bonding of the two levels of modeling. Intermolecular interactions such as hydrogen bonding are added sequentially until the force field holds the microfibril crystal structure. This stepwise process enables us to evaluate the importance of each potential and provides insight to ordered and disordered regions. We simulate cellulose microfibrils with 100 to 400 residues, comparable to the smallest observed microfibrils. Microfibrils longer than 100nm would form a bending region along their longitudinal direction. Multiple bends are observed in the microfibril containing 400 residues. Although the cause is not clear, the bending regions may provide us insights about the periodicity and the behavior of the disordered regions in the microfibril.

Nanoscale movements of cellulose microfibrils in primary cell walls.

PubMed

Zhang, Tian; Vavylonis, Dimitrios; Durachko, Daniel M; Cosgrove, Daniel J

2017-04-28

The growing plant cell wall is commonly considered to be a fibre-reinforced structure whose strength, extensibility and anisotropy depend on the orientation of crystalline cellulose microfibrils, their bonding to the polysaccharide matrix and matrix viscoelasticity 1-4 . Structural reinforcement of the wall by stiff cellulose microfibrils is central to contemporary models of plant growth, mechanics and meristem dynamics 4-12 . Although passive microfibril reorientation during wall extension has been inferred from theory and from bulk measurements 13-15 , nanometre-scale movements of individual microfibrils have not been directly observed. Here we combined nanometre-scale imaging of wet cell walls by atomic force microscopy (AFM) with a stretching device and endoglucanase treatment that induces wall stress relaxation and creep, mimicking wall behaviours during cell growth. Microfibril movements during forced mechanical extensions differ from those during creep of the enzymatically loosened wall. In addition to passive angular reorientation, we observed a diverse repertoire of microfibril movements that reveal the spatial scale of molecular connections between microfibrils. Our results show that wall loosening alters microfibril connectivity, enabling microfibril dynamics not seen during mechanical stretch. These insights into microfibril movements and connectivities need to be incorporated into refined models of plant cell wall structure, growth and morphogenesis.

Multi-scale model for the hierarchical architecture of native cellulose hydrogels.

PubMed

Martínez-Sanz, Marta; Mikkelsen, Deirdre; Flanagan, Bernadine; Gidley, Michael J; Gilbert, Elliot P

2016-08-20

The structure of protiated and deuterated cellulose hydrogels has been investigated using a multi-technique approach combining small-angle scattering with diffraction, spectroscopy and microscopy. A model for the multi-scale structure of native cellulose hydrogels is proposed which highlights the essential role of water at different structural levels characterised by: (i) the existence of cellulose microfibrils containing an impermeable crystalline core surrounded by a partially hydrated paracrystalline shell, (ii) the creation of a strong network of cellulose microfibrils held together by hydrogen bonding to form cellulose ribbons and (iii) the differential behaviour of tightly bound water held within the ribbons compared to bulk solvent. Deuterium labelling provides an effective platform on which to further investigate the role of different plant cell wall polysaccharides in cellulose composite formation through the production of selectively deuterated cellulose composite hydrogels. Copyright © 2016 Elsevier Ltd. All rights reserved.

Mechanical properties of individual southern pine fibers. Part III. Global relationships between fiber properties and fiber location within an individual tree.

Treesearch

Leslie H. Groom; Stephen Shaler; Laurence Mott

2002-01-01

This is the third and final paper in a three-part series investigating the effect of location within a tree on the mechanical properties of individual wood tracheids. This paper focuses on the definition of juvenile, transition, and mature zones as classified by fiber stiffness, strength, microfibril angle, and cross-sectional area. The average modulus of elasticity...

Mechanical Properties of Individual Southern Pine Fibers. Part III: Global Relationships Between Fiber Properties and Fiber Location Within An Individual Tree

Treesearch

Les Groom; Stephen Shaler; Laurence Mott

2002-01-01

This is the third and final paper in a three-part series investigating the effect of location within a tree on the mechanical properties of individual wood tracheids. This paper focuses on the definition of juvenile, transition, and mature zones as classified by fiber stiffness, strength, microfibril angle, and cross-sectional area. The average modulus of elasticity...

The potential of acoustics to determine family differences for wood quality in a loblolly pine (Pinus taeda L.) trial

Treesearch

E M Raley; Jennifer H Myszewski; T D Byram

2007-01-01

Acoustics have been used to determine wood quality attributes in both standing timber and sawn lumber. Sonic transmission data are collected non-destructively and can act as a surrogate for stiffness, they are directly related to modulus of elasticity (MOE) and closely related to differences in microfibril angle (MFA). Together with wood density, MFA and MOE are the...

Arrangement of Cellulose Microfibrils in Walls of Elongating Parenchyma Cells

PubMed Central

Setterfield, G.; Bayley, S. T.

1958-01-01

The arrangement of cellulose microfibrils in walls of elongating parenchyma cells of Avena coleoptiles, onion roots, and celery petioles was studied in polarizing and electron microscopes by examining whole cell walls and sections. Walls of these cells consist firstly of regions containing the primary pit fields and composed of microfibrils oriented predominantly transversely. The transverse microfibrils show a progressive disorientation from the inside to the outside of the wall which is consistent with the multinet model of wall growth. Between the pit-field regions and running the length of the cells are ribs composed of longitudinally oriented microfibrils. Two types of rib have been found at all stages of cell elongation. In some regions, the wall appears to consist entirely of longitudinal microfibrils so that the rib forms an integral part of the wall. At the edges of such ribs the microfibrils can be seen to change direction from longitudinal in the rib to transverse in the pit-field region. Often, however, the rib appears to consist of an extra separate layer of longitudinal microfibrils outside a continuous wall of transverse microfibrils. These ribs are quite distinct from secondary wall, which consists of longitudinal microfibrils deposited within the primary wall after elongation has ceased. It is evident that the arrangement of cellulose microfibrils in a primary wall can be complex and is probably an expression of specific cellular differentiation. PMID:13563544

Use of Small Angle Neutron Scattering to Study Various Properties of Wool and Mohair Fibres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franklyn, C. B.; Toeroek, Gy.

2011-12-13

To maintain a competitive edge in the wool and mohair industry, a detailed knowledge and understanding of the properties of wool fibres is essential. Standard techniques are used to determine fibre diameter, length and strength; however, properties such as hydroscopicity, lustre and changes in fibre structure following chemical or mechanical treatment are not so well understood. The unique capabilities of small angle neutron scattering to study changes in the supermolecular structure of wool fibres, particularly at the level of the microfibril-matrix complex, have been used to provide previously unknown features of the fibres. The results of these studies are presented.

Scanning Electron Microscope Examination of Cotton Linters and Wood Pulp Fibers before and after Nitration and Gun Propellant Manufacture

DTIC Science & Technology

1983-03-01

both types of cellulose , the cell walls are still intact with the microfibrils showing little damage. The cellulose microfibrils consist of long chains...25 2. Model of Cellulose Microfibril ... S............. .............. .26 3. Model of Plant Cell Wall Bonding of Microfibril Bundles...molecules protrude above and below the plane of the cellulose ribbon.J’ (See Figures 2 and 3,) Bundles of these cellulose ribbons are called microfibrils

Hierarchical structure and biomineralization in cricket teeth

NASA Astrophysics Data System (ADS)

Xing, Xue-Qing; Gong, Yu; Cai, Quan; Mo, Guang; Du, Rong; Chen, Zhong-Jun; Wu, Zhong-Hua

2013-02-01

The cricket is a truculent insect with stiff and sharp teeth as a fighting weapon. The structure and possible biomineralization of cricket teeth are always interesting. Synchrotron radiation X-ray fluorescence, X-ray diffraction, and small angle X-ray scattering techniques were used to probe the element distribution, possible crystalline structures and size distribution of scatterers in cricket teeth. A scanning electron microscope was used to observe the nanoscaled structure. The results demonstrate that Zn is the main heavy element in cricket teeth. The surface of a cricket tooth has a crystalline compound like ZnFe2(AsO4)2(OH)2(H2O)4. The interior of the tooth has a crystalline compound like ZnCl2, which is from the biomineralization. The ZnCl2-like biomineral forms nanoscaled microfibrils and their axial direction points towards the top of the tooth cusp. The microfibrils aggregate randomly into intermediate filaments, forming a hierarchical structure. A sketch map of the cricket tooth cusp is proposed and a detailed discussion is given in this paper.

Cellulose microfibril formation within a coarse grained molecular dynamics

NASA Astrophysics Data System (ADS)

Nili, Abdolmadjid; Shklyaev, Oleg; Crespi, Vincent; Zhao, Zhen; Zhong, Linghao; CLSF Collaboration

2014-03-01

Cellulose in biomass is mostly in the form of crystalline microfibrils composed of 18 to 36 parallel chains of polymerized glucose monomers. A single chain is produced by cellular machinery (CesA) located on the preliminary cell wall membrane. Information about the nucleation stage can address important questions about intermediate region between cell wall and the fully formed crystalline microfibrils. Very little is known about the transition from isolated chains to protofibrils up to a full microfibril, in contrast to a large body of studies on both CesA and the final crystalline microfibril. In addition to major experimental challenges in studying this transient regime, the length and time scales of microfibril nucleation are inaccessible to atomistic molecular dynamics. We have developed a novel coarse grained model for cellulose microfibrils which accounts for anisotropic interchain interactions. The model allows us to study nucleation, kinetics, and growth of cellulose chains/protofibrils/microfibrils. This work is supported by the US Department of Energy, Office of Basic Energy Sciences as part of The Center for LignoCellulose Structure and Formation, an Energy Frontier Research Center.

Structure of native cellulose microfibrils, the starting point for nanocellulose manufacture

NASA Astrophysics Data System (ADS)

Jarvis, Michael C.

2017-12-01

There is an emerging consensus that higher plants synthesize cellulose microfibrils that initially comprise 18 chains. However, the mean number of chains per microfibril in situ is usually greater than 18, sometimes much greater. Microfibrils from woody tissues of conifers, grasses and dicotyledonous plants, and from organs like cotton hairs, all differ in detailed structure and mean diameter. Diameters increase further when aggregated microfibrils are isolated. Because surface chains differ, the tensile properties of the cellulose may be augmented by increasing microfibril diameter. Association of microfibrils with anionic polysaccharides in primary cell walls and mucilages leads to in vivo mechanisms of disaggregation that may be relevant to the preparation of nanofibrillar cellulose products. For the preparation of nanocrystalline celluloses, the key issue is the nature and axial spacing of disordered domains at which axial scission can be initiated. These disordered domains do not, as has often been suggested, take the form of large blocks occupying much of the length of the microfibril. They are more likely to be located at chain ends or at places where the microfibril has been mechanically damaged, but their structure and the reasons for their sensitivity to acid hydrolysis need better characterization. This article is part of a discussion meeting issue `New horizons for cellulose nanotechnology'.

Structure of native cellulose microfibrils, the starting point for nanocellulose manufacture.

PubMed

Jarvis, Michael C

2018-02-13

There is an emerging consensus that higher plants synthesize cellulose microfibrils that initially comprise 18 chains. However, the mean number of chains per microfibril in situ is usually greater than 18, sometimes much greater. Microfibrils from woody tissues of conifers, grasses and dicotyledonous plants, and from organs like cotton hairs, all differ in detailed structure and mean diameter. Diameters increase further when aggregated microfibrils are isolated. Because surface chains differ, the tensile properties of the cellulose may be augmented by increasing microfibril diameter. Association of microfibrils with anionic polysaccharides in primary cell walls and mucilages leads to in vivo mechanisms of disaggregation that may be relevant to the preparation of nanofibrillar cellulose products. For the preparation of nanocrystalline celluloses, the key issue is the nature and axial spacing of disordered domains at which axial scission can be initiated. These disordered domains do not, as has often been suggested, take the form of large blocks occupying much of the length of the microfibril. They are more likely to be located at chain ends or at places where the microfibril has been mechanically damaged, but their structure and the reasons for their sensitivity to acid hydrolysis need better characterization.This article is part of a discussion meeting issue 'New horizons for cellulose nanotechnology'. © 2017 The Author(s).

Cell wall biogenesis in Oocystis: experimental alteration of microfibril assembly and orientation.

PubMed

Montezinos, D; Brown, R M

1978-01-01

Cell wall biogenesis in the unicellular green alga Oocystis apiculata has been studied. Under normal growth conditions, a cell wall with ordered microfibrils is synthesized. In each layer there are rows of parallel microfibrils. Layers are nearly perpendicular to each other. Terminal linear synthesizing complexes are located in the plasma membrane, and they are capable of bidirectional synthesis of cellulose microfibrils. Granule bands associated with the inner leaflet of the plasma membrane appear to control the orientation of newly synthesized microfibrils. Subcortical microtubules also are present during wall synthesis. Patterns of cell wall synthesis were studied after treatment with EDTA and EGTA as well as divalent cations (MgSO4, CaSO4, Cacl2). 0.1 M EDTA treatment for 15 min results in the disassociation of the terminal complexes from the ends of microfibrils. EDTA-treated cells followed by 15 min treatment with MgSO4 results in reaggregation of the linear complexes into a paired state, remote from the original ends to which they were associated. After 90 min treatment with MgSO4, normal synthesis resumes. EGTA and calcium salts do not affect the linear complexes or microfibril orientation. Treatments with colchicine and vinblastine sulphate do not depolymerize the microtubles, but the wall microfibril orientation is altered. With colchicine or vinblastine, the change in orientation from layer to layer is inhibited. The process is reversible upon removal of the drugs. Lumicolchicine has no effect upon microfibril orientation, but granule bands are disorganized. Treatment with coumarin, a known inhibitor of cellulose synthesis, causes the loss of visualization of subunits of the terminal complexes. The possibility of the existence of a membrane-associated colchicine-sensitive orientation protein for cellulose microfibrils is discussed. Transmembrane modulation of microfibril synthesis and orientation is presented.

The missing link: do cortical microtubules define plasma membrane nanodomains that modulate cellulose biosynthesis?

PubMed

Fujita, Miki; Lechner, Bettina; Barton, Deborah A; Overall, Robyn L; Wasteneys, Geoffrey O

2012-02-01

Cellulose production is a crucial aspect of plant growth and development. It is functionally linked to cortical microtubules, which self-organize into highly ordered arrays often situated in close proximity to plasma membrane-bound cellulose synthase complexes (CSCs). Although most models put forward to explain the microtubule-cellulose relationship have considered mechanisms by which cortical microtubule arrays influence the orientation of cellulose microfibrils, little attention has been paid to how microtubules affect the physicochemical properties of cellulose. A recent study using the model system Arabidopsis, however, indicates that microtubules can modulate the crystalline and amorphous content of cellulose microfibrils. Microtubules are required during rapid growth for reducing crystalline content, which is predicted to increase the degree to which cellulose is tethered by hemicellulosic polysaccharides. Such tethering is, in turn, critical for maintaining unidirectional cell expansion. In this article, we hypothesize that cortical microtubules influence the crystalline content of cellulose either by controlling plasma membrane fluidity or by modulating the deposition of noncellulosic wall components in the vicinity of the CSCs. We discuss the current limitations of imaging technology to address these hypotheses and identify the image acquisition and processing strategies that will integrate live imaging with super resolution three-dimensional information.

Long-term effects of elevated carbon dioxide concentration on sour orange wood specific gravity, modulus of elasticity, and microfibril angle

Treesearch

David Kretschmann; James Evans; Mike Wiemann; Bruce A. Kimball; Sherwood B. Idso

2007-01-01

The carbon dioxide (CO2) concentration of Earth’s atmosphere continues to rise. Plants in general are responsive to changing CO2 concentrations, which suggests changes in agricultural productivity in the United States and around the world. The ability of plants to absorb CO2 during photosynthesis and then store carbon in their structure or sequester it in the soil has...

Genetic architecture of wood properties based on association analysis and co-expression networks in white spruce.

PubMed

Lamara, Mebarek; Raherison, Elie; Lenz, Patrick; Beaulieu, Jean; Bousquet, Jean; MacKay, John

2016-04-01

Association studies are widely utilized to analyze complex traits but their ability to disclose genetic architectures is often limited by statistical constraints, and functional insights are usually minimal in nonmodel organisms like forest trees. We developed an approach to integrate association mapping results with co-expression networks. We tested single nucleotide polymorphisms (SNPs) in 2652 candidate genes for statistical associations with wood density, stiffness, microfibril angle and ring width in a population of 1694 white spruce trees (Picea glauca). Associations mapping identified 229-292 genes per wood trait using a statistical significance level of P < 0.05 to maximize discovery. Over-representation of genes associated for nearly all traits was found in a xylem preferential co-expression group developed in independent experiments. A xylem co-expression network was reconstructed with 180 wood associated genes and several known MYB and NAC regulators were identified as network hubs. The network revealed a link between the gene PgNAC8, wood stiffness and microfibril angle, as well as considerable within-season variation for both genetic control of wood traits and gene expression. Trait associations were distributed throughout the network suggesting complex interactions and pleiotropic effects. Our findings indicate that integration of association mapping and co-expression networks enhances our understanding of complex wood traits. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Suppression of xylan endotransglycosylase PtxtXyn10A affects cellulose microfibril angle in secondary wall in aspen wood.

PubMed

Derba-Maceluch, Marta; Awano, Tatsuya; Takahashi, Junko; Lucenius, Jessica; Ratke, Christine; Kontro, Inkeri; Busse-Wicher, Marta; Kosik, Ondrej; Tanaka, Ryo; Winzéll, Anders; Kallas, Åsa; Leśniewska, Joanna; Berthold, Fredrik; Immerzeel, Peter; Teeri, Tuula T; Ezcurra, Ines; Dupree, Paul; Serimaa, Ritva; Mellerowicz, Ewa J

2015-01-01

Certain xylanases from family GH10 are highly expressed during secondary wall deposition, but their function is unknown. We carried out functional analyses of the secondary-wall specific PtxtXyn10A in hybrid aspen (Populus tremula × tremuloides). PtxtXyn10A function was analysed by expression studies, overexpression in Arabidopsis protoplasts and by downregulation in aspen. PtxtXyn10A overexpression in Arabidopsis protoplasts resulted in increased xylan endotransglycosylation rather than hydrolysis. In aspen, the enzyme was found to be proteolytically processed to a 68 kDa peptide and residing in cell walls. Its downregulation resulted in a corresponding decrease in xylan endotransglycosylase activity and no change in xylanase activity. This did not alter xylan molecular weight or its branching pattern but affected the cellulose-microfibril angle in wood fibres, increased primary growth (stem elongation, leaf formation and enlargement) and reduced the tendency to form tension wood. Transcriptomes of transgenic plants showed downregulation of tension wood related genes and changes in stress-responsive genes. The data indicate that PtxtXyn10A acts as a xylan endotransglycosylase and its main function is to release tensional stresses arising during secondary wall deposition. Furthermore, they suggest that regulation of stresses in secondary walls plays a vital role in plant development. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Alteration of Oriented Deposition of Cellulose Microfibrils by Mutation of a Katanin-Like Microtubule-Severing Protein

PubMed Central

Burk, David H.; Ye, Zheng-Hua

2002-01-01

It has long been hypothesized that cortical microtubules (MTs) control the orientation of cellulose microfibril deposition, but no mutants with alterations of MT orientation have been shown to affect this process. We have shown previously that in Arabidopsis, the fra2 mutation causes aberrant cortical MT orientation and reduced cell elongation, and the gene responsible for the fra2 mutation encodes a katanin-like protein. In this study, using field emission scanning electron microscopy, we found that the fra2 mutation altered the normal orientation of cellulose microfibrils in walls of expanding cells. Although cellulose microfibrils in walls of wild-type cells were oriented transversely along the elongation axis, cellulose microfibrils in walls of fra2 cells often formed bands and ran in different directions. The fra2 mutation also caused aberrant deposition of cellulose microfibrils in secondary walls of fiber cells. The aberrant orientation of cellulose microfibrils was shown to be correlated with disorganized cortical MTs in several cell types examined. In addition, the thickness of both primary and secondary cell walls was reduced significantly in the fra2 mutant. These results indicate that the katanin-like protein is essential for oriented cellulose microfibril deposition and normal cell wall biosynthesis. We further demonstrated that the Arabidopsis katanin-like protein possessed MT-severing activity in vitro; thus, it is an ortholog of animal katanin. We propose that the aberrant MT orientation caused by the mutation of katanin results in the distorted deposition of cellulose microfibrils, which in turn leads to a defect in cell elongation. These findings strongly support the hypothesis that cortical MTs regulate the oriented deposition of cellulose microfibrils that determines the direction of cell elongation. PMID:12215512

Alteration of oriented deposition of cellulose microfibrils by mutation of a katanin-like microtubule-severing protein.

PubMed

Burk, David H; Ye, Zheng-Hua

2002-09-01

It has long been hypothesized that cortical microtubules (MTs) control the orientation of cellulose microfibril deposition, but no mutants with alterations of MT orientation have been shown to affect this process. We have shown previously that in Arabidopsis, the fra2 mutation causes aberrant cortical MT orientation and reduced cell elongation, and the gene responsible for the fra2 mutation encodes a katanin-like protein. In this study, using field emission scanning electron microscopy, we found that the fra2 mutation altered the normal orientation of cellulose microfibrils in walls of expanding cells. Although cellulose microfibrils in walls of wild-type cells were oriented transversely along the elongation axis, cellulose microfibrils in walls of fra2 cells often formed bands and ran in different directions. The fra2 mutation also caused aberrant deposition of cellulose microfibrils in secondary walls of fiber cells. The aberrant orientation of cellulose microfibrils was shown to be correlated with disorganized cortical MTs in several cell types examined. In addition, the thickness of both primary and secondary cell walls was reduced significantly in the fra2 mutant. These results indicate that the katanin-like protein is essential for oriented cellulose microfibril deposition and normal cell wall biosynthesis. We further demonstrated that the Arabidopsis katanin-like protein possessed MT-severing activity in vitro; thus, it is an ortholog of animal katanin. We propose that the aberrant MT orientation caused by the mutation of katanin results in the distorted deposition of cellulose microfibrils, which in turn leads to a defect in cell elongation. These findings strongly support the hypothesis that cortical MTs regulate the oriented deposition of cellulose microfibrils that determines the direction of cell elongation.

Epithelial-mesenchymal status influences how cells deposit fibrillin microfibrils.

PubMed

Baldwin, Andrew K; Cain, Stuart A; Lennon, Rachel; Godwin, Alan; Merry, Catherine L R; Kielty, Cay M

2014-01-01

Here, we show that epithelial-mesenchymal status influences how cells deposit extracellular matrix. Retinal pigmented epithelial (RPE) cells that expressed high levels of E-cadherin and had cell-cell junctions rich in zona occludens (ZO)-1, β-catenin and heparan sulfate, required syndecan-4 but not fibronectin or protein kinase C α (PKCα) to assemble extracellular matrix (fibrillin microfibrils and perlecan). In contrast, RPE cells that strongly expressed mesenchymal smooth muscle α-actin but little ZO-1 or E-cadherin, required fibronectin (like fibroblasts) and PKCα, but not syndecan-4. Integrins α5β1 and/or α8β1 and actomyosin tension were common requirements for microfibril deposition, as was heparan sulfate biosynthesis. TGFβ, which stimulates epithelial-mesenchymal transition, altered gene expression and overcame the dependency on syndecan-4 for microfibril deposition in epithelial RPE cells, whereas blocking cadherin interactions disrupted microfibril deposition. Renal podocytes had a transitional phenotype with pericellular β-catenin but little ZO-1; they required syndecan-4 and fibronectin for efficient microfibril deposition. Thus, epithelial-mesenchymal status modulates microfibril deposition.

Building and degradation of secondary cell walls: are there common patterns of lamellar assembly of cellulose microfibrils and cell wall delamination?

PubMed

De Micco, Veronica; Ruel, Katia; Joseleau, Jean-Paul; Aronne, Giovanna

2010-08-01

During cell wall formation and degradation, it is possible to detect cellulose microfibrils assembled into thicker and thinner lamellar structures, respectively, following inverse parallel patterns. The aim of this study was to analyse such patterns of microfibril aggregation and cell wall delamination. The thickness of microfibrils and lamellae was measured on digital images of both growing and degrading cell walls viewed by means of transmission electron microscopy. To objectively detect, measure and classify microfibrils and lamellae into thickness classes, a method based on the application of computerized image analysis combined with graphical and statistical methods was developed. The method allowed common classes of microfibrils and lamellae in cell walls to be identified from different origins. During both the formation and degradation of cell walls, a preferential formation of structures with specific thickness was evidenced. The results obtained with the developed method allowed objective analysis of patterns of microfibril aggregation and evidenced a trend of doubling/halving lamellar structures, during cell wall formation/degradation in materials from different origin and which have undergone different treatments.

Cellulose microfibrils in plants: biosynthesis, deposition, and integration into the cell wall.

PubMed

Brett, C T

2000-01-01

Cellulose occurs in all higher plants and some algae, fungi, bacteria, and animals. It forms microfibrils containing the crystalline allomorphs, cellulose I alpha and I beta. Cellulose molecules are 500-15,000 glucose units long. What controls molecular size is unknown. Microfibrils are elongated by particle rosettes in the plasma membrane (cellulose synthase complexes). The precursor, UDP-glucose, may be generated from sucrose at the site of synthesis. The biosynthetic mechanism may involve lipid-linked intermediates. Cellulose synthase has been purified from bacteria, but not from plants. In plants, disrupted cellulose synthase may form callose. Cellulose synthase genes have been isolated from bacteria and plants. Cellulose-deficient mutants have been characterised. The deduced amino acid sequence suggests possible catalytic mechanisms. It is not known whether synthesis occurs at the reducing or nonreducing end. Endoglucanase may play a role in synthesis. Nascent cellulose molecules associate by Van der Waals and hydrogen bonds to form microfibrils. Cortical microtubules control microfibril orientation, thus determining the direction of cell growth. Self-assembly mechanisms may operate. Microfibril integration into the wall occurs by interactions with matrix polymers during microfibril formation.

Microfibril-associated glycoproteins MAGP-1 and MAGP-2 in disease.

PubMed

Craft, Clarissa S; Broekelmann, Thomas J; Mecham, Robert P

2018-03-07

Microfibril-associated glycoproteins 1 and 2 (MAGP-1, MAGP-2) are protein components of extracellular matrix microfibrils. These proteins interact with fibrillin, the core component of microfibrils, and impart unique biological properties that influence microfibril function in vertebrates. MAGPs bind active forms of TGFβ and BMPs and are capable of modulating Notch signaling. Mutations in MAGP-1 or MAGP-2 have been linked to thoracic aneurysms and metabolic disease in humans. MAGP-2 has also been shown to be an important biomarker in several human cancers. Mice lacking MAGP-1 or MAGP-2 have defects in multiple organ systems, which reflects the widespread distribution of microfibrils in vertebrate tissues. This review summarizes our current understanding of the function of the MAGPs and their relationship to human disease. Copyright © 2017 International Society of Matrix Biology. Published by Elsevier B.V. All rights reserved.

The Impact of Microfibril Orientations on the Biomechanics of Plant Cell Walls and Tissues.

PubMed

Ptashnyk, Mariya; Seguin, Brian

2016-11-01

The microscopic structure and anisotropy of plant cell walls greatly influence the mechanical properties, morphogenesis, and growth of plant cells and tissues. The microscopic structure and properties of cell walls are determined by the orientation and mechanical properties of the cellulose microfibrils and the mechanical properties of the cell wall matrix. Viewing the shape of a plant cell as a square prism with the axis aligning with the primary direction of expansion and growth, the orientation of the microfibrils within the side walls, i.e. the parts of the cell walls on the sides of the cells, is known. However, not much is known about their orientation at the upper and lower ends of the cell. Here we investigate the impact of the orientation of cellulose microfibrils within the upper and lower parts of the plant cell walls by solving the equations of linear elasticity numerically. Three different scenarios for the orientation of the microfibrils are considered. We also distinguish between the microstructure in the side walls given by microfibrils perpendicular to the main direction of the expansion and the situation where the microfibrils are rotated through the wall thickness. The macroscopic elastic properties of the cell wall are obtained using homogenization theory from the microscopic description of the elastic properties of the cell wall microfibrils and wall matrix. It is found that the orientation of the microfibrils in the upper and lower parts of the cell walls affects the expansion of the cell in the lateral directions and is particularly important in the case of forces acting on plant cell walls and tissues.

Structure of Cellulose Microfibrils in Primary Cell Walls from Collenchyma1[C][W][OA

PubMed Central

Thomas, Lynne H.; Forsyth, V. Trevor; Šturcová, Adriana; Kennedy, Craig J.; May, Roland P.; Altaner, Clemens M.; Apperley, David C.; Wess, Timothy J.; Jarvis, Michael C.

2013-01-01

In the primary walls of growing plant cells, the glucose polymer cellulose is assembled into long microfibrils a few nanometers in diameter. The rigidity and orientation of these microfibrils control cell expansion; therefore, cellulose synthesis is a key factor in the growth and morphogenesis of plants. Celery (Apium graveolens) collenchyma is a useful model system for the study of primary wall microfibril structure because its microfibrils are oriented with unusual uniformity, facilitating spectroscopic and diffraction experiments. Using a combination of x-ray and neutron scattering methods with vibrational and nuclear magnetic resonance spectroscopy, we show that celery collenchyma microfibrils were 2.9 to 3.0 nm in mean diameter, with a most probable structure containing 24 chains in cross section, arranged in eight hydrogen-bonded sheets of three chains, with extensive disorder in lateral packing, conformation, and hydrogen bonding. A similar 18-chain structure, and 24-chain structures of different shape, fitted the data less well. Conformational disorder was largely restricted to the surface chains, but disorder in chain packing was not. That is, in position and orientation, the surface chains conformed to the disordered lattice constituting the core of each microfibril. There was evidence that adjacent microfibrils were noncovalently aggregated together over part of their length, suggesting that the need to disrupt these aggregates might be a constraining factor in growth and in the hydrolysis of cellulose for biofuel production. PMID:23175754

Structure of cellulose microfibrils in primary cell walls from collenchyma.

PubMed

Thomas, Lynne H; Forsyth, V Trevor; Sturcová, Adriana; Kennedy, Craig J; May, Roland P; Altaner, Clemens M; Apperley, David C; Wess, Timothy J; Jarvis, Michael C

2013-01-01

In the primary walls of growing plant cells, the glucose polymer cellulose is assembled into long microfibrils a few nanometers in diameter. The rigidity and orientation of these microfibrils control cell expansion; therefore, cellulose synthesis is a key factor in the growth and morphogenesis of plants. Celery (Apium graveolens) collenchyma is a useful model system for the study of primary wall microfibril structure because its microfibrils are oriented with unusual uniformity, facilitating spectroscopic and diffraction experiments. Using a combination of x-ray and neutron scattering methods with vibrational and nuclear magnetic resonance spectroscopy, we show that celery collenchyma microfibrils were 2.9 to 3.0 nm in mean diameter, with a most probable structure containing 24 chains in cross section, arranged in eight hydrogen-bonded sheets of three chains, with extensive disorder in lateral packing, conformation, and hydrogen bonding. A similar 18-chain structure, and 24-chain structures of different shape, fitted the data less well. Conformational disorder was largely restricted to the surface chains, but disorder in chain packing was not. That is, in position and orientation, the surface chains conformed to the disordered lattice constituting the core of each microfibril. There was evidence that adjacent microfibrils were noncovalently aggregated together over part of their length, suggesting that the need to disrupt these aggregates might be a constraining factor in growth and in the hydrolysis of cellulose for biofuel production.

Advances in Surface Plasmon Resonance Imaging enable quantitative measurement of laterally heterogeneous coatings of nanoscale thickness

NASA Astrophysics Data System (ADS)

Raegen, Adam; Reiter, Kyle; Clarke, Anthony; Lipkowski, Jacek; Dutcher, John

2013-03-01

The Surface Plasmon Resonance (SPR) phenomenon is routinely exploited to qualitatively probe changes to the optical properties of nanoscale coatings on thin metallic surfaces, for use in probes and sensors. Unfortunately, extracting truly quantitative information is usually limited to a select few cases - uniform absorption/desorption of small biomolecules and films, in which a continuous ``slab'' model is a good approximation. We present advancements in the SPR technique that expand the number of cases for which the technique can provide meaningful results. Use of a custom, angle-scanning SPR imaging system, together with a refined data analysis method, allow for quantitative kinetic measurements of laterally heterogeneous systems. We first demonstrate the directionally heterogeneous nature of the SPR phenomenon using a directionally ordered sample, then show how this allows for the calculation of the average coverage of a heterogeneous sample. Finally, the degradation of cellulose microfibrils and bundles of microfibrils due to the action of cellulolytic enzymes will be presented as an excellent example of the capabilities of the SPR imaging system.

Preparation and properties of self-reinforced cellulose composite films from Agave microfibrils using an ionic liquid.

PubMed

Reddy, K Obi; Zhang, Jinming; Zhang, Jun; Rajulu, A Varada

2014-12-19

The applications of natural fibers and their microfibrils are increasing rapidly due to their environment benefits, specific strength properties and renewability. In the present work, we successfully extracted cellulose microfibrils from Agave natural fibers by chemical method. The extracted microfibrils were characterized by chemical analysis. The cellulose microfibrils were found to dissolve in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) to larger extent along with little quantity of undissolved microfibrils. Using this solution, the self-reinforced regenerated cellulose composite films were prepared. The raw fiber, extracted cellulose microfibrils and regenerated cellulose composite films were characterized by FTIR, (13)C CP-MAS NMR, XRD, TGA and SEM techniques. The average tensile strength, modulus and elongation at break of the self-reinforced cellulose composite films were found to be 135 MPa, 8150 MPa and 3.2%, respectively. The high values of tensile strength and modulus were attributed to the self-reinforcement of Agave fibers in their generated matrix. These self-reinforced cellulose biodegradable composite films prepared from renewable source can find applications in packaging field. Copyright © 2014 Elsevier Ltd. All rights reserved.

New techniques enable comparative analysis of microtubule orientation, wall texture, and growth rate in intact roots of Arabidopsis.

PubMed

Sugimoto, K; Williamson, R E; Wasteneys, G O

2000-12-01

This article explores root epidermal cell elongation and its dependence on two structural elements of cells, cortical microtubules and cellulose microfibrils. The recent identification of Arabidopsis morphology mutants with putative cell wall or cytoskeletal defects demands a procedure for examining and comparing wall architecture and microtubule organization patterns in this species. We developed methods to examine cellulose microfibrils by field emission scanning electron microscopy and microtubules by immunofluorescence in essentially intact roots. We were able to compare cellulose microfibril and microtubule alignment patterns at equivalent stages of cell expansion. Field emission scanning electron microscopy revealed that Arabidopsis root epidermal cells have typical dicot primary cell wall structure with prominent transverse cellulose microfibrils embedded in pectic substances. Our analysis showed that microtubules and microfibrils have similar orientation only during the initial phase of elongation growth. Microtubule patterns deviate from a predominantly transverse orientation while cells are still expanding, whereas cellulose microfibrils remain transverse until well after expansion finishes. We also observed microtubule-microfibril alignment discord before cells enter their elongation phase. This study and the new technology it presents provide a starting point for further investigations on the physical properties of cell walls and their mechanisms of assembly.

Fluorescent cellulose microfibrils as substrate for the detection of cellulase activity.

PubMed

Helbert, William; Chanzy, Henri; Husum, Tommy Lykke; Schülein, Martin; Ernst, Steffen

2003-01-01

To devise a sensitive cellulase assay based on substrates having most of the physical characteristics of native cellulose, 5-(4,6-dichlorotriazinyl)aminofluorescein (DTAF) was used as a grafting agent to prepare suspensions of fluorescent microfibrils from bacterial cellulose. These suspensions were digested by a series of commercially relevant cellulases from Humicola insolens origin: cloned Cel6B and Cel 45A as well as crude H. insolens complex. The digestion induced the release of fluorescent cellodextrins as well as reducing sugars. After adequate centrifugation, these soluble products were analyzed as a function of grafting content, digestion time, and cellulase characteristics. The resulting data allowed the grafting conditions to be optimized in order to maximize the quantity of soluble products and therefore to increase the sensitivity of the detection. A comparison between the amount of released fluorescence and that of released reducing sugar allowed the differentiation between processive exo and endo cellulase activities. The casting of films of DTAF-grafted microfibrils at the bottom of the microwell titer plates also led to sensitive cellulase detection. As these films kept their integrity and remained firmly glued to the well bottom during the digestion time, they are tailored made for a full automation of the cellulases testing.

Microtubules and cellulose biosynthesis: the emergence of new players.

PubMed

Li, Shundai; Lei, Lei; Yingling, Yaroslava G; Gu, Ying

2015-12-01

Microtubules determine the orientation of newly formed cellulose microfibrils in expanding cells. There are many hypotheses regarding how the information is transduced across the plasma membrane from microtubules to cellulose microfibrils. However, the molecular mechanisms underlying the co-alignment between microtubules and cellulose microfibrils were not revealed until the recent discovery of cellulose synthase interacting (CSI) proteins. Characterization of CSIs and additional cellulose synthase-associated proteins will greatly advance the knowledge of how cellulose microfibrils are organized. Copyright © 2015 Elsevier Ltd. All rights reserved.

Cellulose microfibrils: visualization of biosynthetic and orienting complexes in association with the plasma membrane.

PubMed

Brown, R M; Montezinos, D

1976-01-01

Cellulose microfibril biosynthesis, assembly, and orientation in the unicellular green alga, Oocystis, is visualized in association with a linear enzyme complex embedded in the B face of the plasma membrane. Granule bands of the A face and complementary ridges of the B face are postulated to assist in the orientation of recently synthesized microfibrils. A model for microfibril synthesis and orientation is proposed and correlated with current hypotheses regarding cellulose biosynthesis in higher plants.

Spatial organization of cellulose microfibrils and matrix polysaccharides in primary plant cell walls as imaged by multichannel atomic force microscopy.

PubMed

Zhang, Tian; Zheng, Yunzhen; Cosgrove, Daniel J

2016-01-01

We used atomic force microscopy (AFM), complemented with electron microscopy, to characterize the nanoscale and mesoscale structure of the outer (periclinal) cell wall of onion scale epidermis - a model system for relating wall structure to cell wall mechanics. The epidermal wall contains ~100 lamellae, each ~40 nm thick, containing 3.5-nm wide cellulose microfibrils oriented in a common direction within a lamella but varying by ~30 to 90° between adjacent lamellae. The wall thus has a crossed polylamellate, not helicoidal, wall structure. Montages of high-resolution AFM images of the newly deposited wall surface showed that single microfibrils merge into and out of short regions of microfibril bundles, thereby forming a reticulated network. Microfibril direction within a lamella did not change gradually or abruptly across the whole face of the cell, indicating continuity of the lamella across the outer wall. A layer of pectin at the wall surface obscured the underlying cellulose microfibrils when imaged by FESEM, but not by AFM. The AFM thus preferentially detects cellulose microfibrils by probing through the soft matrix in these hydrated walls. AFM-based nanomechanical maps revealed significant heterogeneity in cell wall stiffness and adhesiveness at the nm scale. By color coding and merging these maps, the spatial distribution of soft and rigid matrix polymers could be visualized in the context of the stiffer microfibrils. Without chemical extraction and dehydration, our results provide multiscale structural details of the primary cell wall in its near-native state, with implications for microfibrils motions in different lamellae during uniaxial and biaxial extensions. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

In vitro synthesis of cellulose microfibrils by a membrane protein from protoplasts of the non-vascular plant Physcomitrella patens.

PubMed

Cho, Sung Hyun; Du, Juan; Sines, Ian; Poosarla, Venkata Giridhar; Vepachedu, Venkata; Kafle, Kabindra; Park, Yong Bum; Kim, Seong H; Kumar, Manish; Nixon, B Tracy

2015-09-01

Plant cellulose synthases (CesAs) form a family of membrane proteins that are associated with hexagonal structures in the plasma membrane called CesA complexes (CSCs). It has been difficult to purify plant CesA proteins for biochemical and structural studies. We describe CesA activity in a membrane protein preparation isolated from protoplasts of Physcomitrella patens overexpressing haemagglutinin (HA)-tagged PpCesA5. Incubating the membrane preparation with UDP-glucose predominantly produced cellulose. Negative-stain EM revealed microfibrils. Cellulase bound to and degraded these microfibrils. Vibrational sum frequency generation (SFG) spectroscopic analysis detected the presence of crystalline cellulose in the microfibrils. Putative CesA proteins were frequently observed attached to the microfibril ends. Combined cross-linking and gradient centrifugation showed bundles of cellulose microfibrils with larger particle aggregates, possibly CSCs. These results suggest that P. patens is a useful model system for biochemical and structural characterization of plant CSCs and their components. © 2015 Authors; published by Portland Press Limited.

Different Conformations of Surface Cellulose Molecules in Native Cellulose Microfibrils Revealed by Layer-by-Layer Peeling.

PubMed

Funahashi, Ryunosuke; Okita, Yusuke; Hondo, Hiromasa; Zhao, Mengchen; Saito, Tsuguyuki; Isogai, Akira

2017-11-13

Layer-by-layer peeling of surface molecules of native cellulose microfibrils was performed using a repeated sequential process of 2,2,6,6-tetramethylpiperidine-1-oxyl radical-mediated oxidation followed by hot alkali extraction. Both highly crystalline algal and tunicate celluloses and low-crystalline cotton and wood celluloses were investigated. Initially, the C6-hydroxy groups of the outermost surface molecules of each algal cellulose microfibril facing the exterior had the gauche-gauche (gg) conformation, whereas those facing the interior had the gauche-trans (gt) conformation. All the other C6-hydroxy groups of the cellulose molecules inside the microfibrils contributing to crystalline cellulose I had the trans-gauche (tg) conformation. After surface peeling, the originally second-layer molecules from the microfibril surface became the outermost surface molecules, and the original tg conformation changed to gg and gt conformations. The plant cellulose microfibrils likely had disordered structures for both the outermost surface and second-layer molecules, as demonstrated using the same layer-by-layer peeling technique.

Structural factors affecting 13C NMR chemical shifts of cellulose: a computational study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Hui; Wang, Tuo; Oehme, Daniel

Here, the doublet C4 peaks at ~ 85 and ~ 89 ppm in solid-state 13C NMR spectra of native cellulose have been attributed to signals of C4 atoms on the surface (solvent-exposed) and in the interior of microfibrils, designated as sC4 and iC4, respectively. The relative intensity ratios of sC4 and iC4 observed in NMR spectra of cellulose have been used to estimate the degree of crystallinity of cellulose and the number of glucan chains in cellulose microfibrils. However, the molecular structures of cellulose responsible for the specific surface and interior C4 peaks have not been positively confirmed. Using densitymore » functional theory (DFT) methods and structures produced from classical molecular dynamics simulations, we investigated how the following four factors affect 13C NMR chemical shifts in cellulose: conformations of exocyclic groups at C6 ( tg, gt and gg), H 2O molecules H-bonded on the surface of the microfibril, glycosidic bond angles (Φ, Ψ) and the distances between H4 and HO3 atoms. We focus on changes in the δ 13C4 value because it is the most significant observable for the same C atom within the cellulose structure. DFT results indicate that different conformations of the exocyclic groups at C6 have the greatest influence on δ 13C4 peak separation, while the other three factors have secondary effects that increase the spread of the calculated C4 interior and surface peaks.« less

Structural factors affecting 13C NMR chemical shifts of cellulose: a computational study

DOE PAGES

Yang, Hui; Wang, Tuo; Oehme, Daniel; ...

2017-11-02

Here, the doublet C4 peaks at ~ 85 and ~ 89 ppm in solid-state 13C NMR spectra of native cellulose have been attributed to signals of C4 atoms on the surface (solvent-exposed) and in the interior of microfibrils, designated as sC4 and iC4, respectively. The relative intensity ratios of sC4 and iC4 observed in NMR spectra of cellulose have been used to estimate the degree of crystallinity of cellulose and the number of glucan chains in cellulose microfibrils. However, the molecular structures of cellulose responsible for the specific surface and interior C4 peaks have not been positively confirmed. Using densitymore » functional theory (DFT) methods and structures produced from classical molecular dynamics simulations, we investigated how the following four factors affect 13C NMR chemical shifts in cellulose: conformations of exocyclic groups at C6 ( tg, gt and gg), H 2O molecules H-bonded on the surface of the microfibril, glycosidic bond angles (Φ, Ψ) and the distances between H4 and HO3 atoms. We focus on changes in the δ 13C4 value because it is the most significant observable for the same C atom within the cellulose structure. DFT results indicate that different conformations of the exocyclic groups at C6 have the greatest influence on δ 13C4 peak separation, while the other three factors have secondary effects that increase the spread of the calculated C4 interior and surface peaks.« less

A survey of cellulose microfibril patterns in dividing, expanding, and differentiating cells of Arabidopsis thaliana.

PubMed

Fujita, Miki; Wasteneys, Geoffrey O

2014-05-01

Cellulose microfibrils are critical for plant cell specialization and function. Recent advances in live cell imaging of fluorescently tagged cellulose synthases to track cellulose synthesis have greatly advanced our understanding of cellulose biosynthesis. Nevertheless, cellulose deposition patterns remain poorly described in many cell types, including those in the process of division or differentiation. In this study, we used field emission scanning electron microscopy analysis of cryo-planed tissues to determine the arrangement of cellulose microfibrils in various faces of cells undergoing cytokinesis or specialized development, including cell types in which cellulose cannot be imaged by conventional approaches. In dividing cells, we detected microfibrillar meshworks in the cell plates, consistent with the concentration at the cell plate of cellulose synthase complexes, as detected by fluorescently tagged CesA6. We also observed a loss of parallel cellulose microfibril orientation in walls of the mother cell during cytokinesis, which corresponded with the loss of fluorescently tagged cellulose synthase complexes from these surfaces. In recently formed guard cells, microfibrils were randomly organized and only formed a highly ordered circumferential pattern after pore formation. In pit fields, cellulose microfibrils were arranged in circular patterns around plasmodesmata. Microfibrils were random in most cotyledon cells except the epidermis and were parallel to the growth axis in trichomes. Deposition of cellulose microfibrils was spatially delineated in metaxylem and protoxylem cells of the inflorescence stem, supporting recent studies on microtubule exclusion mechanisms.

A synchronous increase in hydraulic conductive capacity and mechanical support in conifers with relatively uniform xylem structure.

PubMed

Jagels, Richard; Visscher, George E

2006-02-01

The dual function provided by longitudinal tracheids in conifers has led to a generally held trade-off concept that increasing wall thickness and/or volume of latewood tracheids improves mechanical support, while increasing cell diameter and/or volume of earlywood tracheids enhances conductive potential. Yet, some conifers have either uniform cell structure across the growth ring or, at most, a small amount of latewood. How do these trees accomplish the needs for increasing support and conduction with height growth? We examined Metasequoia glyptostroboides, a species that we previously demonstrated improves its mechanical properties with increasing age without a change in specific gravity or secondary wall microfibril angle. In this paper, we showed that lignin and extractive contents are not contributing factors, and through composite structure analysis, we eliminated a role for tracheid length. Using micromorphometric analysis, we demonstrated that as cell diameter increases, total primary wall decreases, secondary wall increases, and strength and conductive capacity increase with no change in specific gravity. Meta-analysis using other species of Cupressaceae, Podocarpaceae, and Araucariaceae provided strong corroborative evidence for this design strategy.

In vitro versus in vivo cellulose microfibrils from plant primary wall synthases: structural differences.

PubMed

Lai-Kee-Him, Joséphine; Chanzy, Henri; Müller, Martin; Putaux, Jean-Luc; Imai, Tomoya; Bulone, Vincent

2002-10-04

Detergent extracts of microsomal fractions from suspension cultured cells of Rubus fruticosus (blackberry) were tested for their ability to synthesize in vitro sizable quantities of cellulose from UDP-glucose. Both Brij 58 and taurocholate were effective and yielded a substantial percentage of cellulose microfibrils together with (1-->3)-beta-d-glucan (callose). The taurocholate extracts, which did not require the addition of Mg(2+), were the most efficient, yielding roughly 20% of cellulose. This cellulose was characterized after callose removal by methylation analysis, electron microscopy, and electron and x-ray synchrotron diffractions; its resistance toward the acid Updegraff reagent was also evaluated. The cellulose microfibrils synthesized in vitro had the same diameter as the endogenous microfibrils isolated from primary cell walls. Both polymers diffracted as cellulose IV(I), a disorganized form of cellulose I. Besides these similarities, the in vitro microfibrils had a higher perfection and crystallinity as well as a better resistance toward the Updegraff reagent. These differences can be attributed to the mode of synthesis of the in vitro microfibrils that are able to grow independently in a neighbor-free environment, as opposed to the cellulose in the parent cell walls where new microfibrils have to interweave with the already laid polymers, with the result of a number of structural defects.

Mineral-Ground Micro-Fibrillated Cellulose Reinforcement for Polymer Compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phipps, Jon; Ireland, Sean; Skuse, David

2017-01-01

ORNL worked with Imerys to demonstrate reinforcement of additive manufacturing feedstock materials using mineral-ground microfibrillated cellulose (MFC). Properly prepared/dried mineral-ground cellulose microfibrils significantly improved mechanical properties of both ABS and PLA resins. While tensile strength increases up to ~40% were observed, elastic modulus of the both resins doubled with the addition of 30% MFC.

Elastic modulus of single cellulose microfibrils from tunicate measured by atomic force microscopy.

PubMed

Iwamoto, Shinichiro; Kai, Weihua; Isogai, Akira; Iwata, Tadahisa

2009-09-14

The elastic modulus of single microfibrils from tunicate ( Halocynthia papillosa ) cellulose was measured by atomic force microscopy (AFM). Microfibrils with cross-sectional dimensions 8 x 20 nm and several micrometers in length were obtained by oxidation of cellulose with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) as a catalyst and subsequent mechanical disintegration in water and by sulfuric acid hydrolysis. The nanocellulosic materials were deposited on a specially designed silicon wafer with grooves 227 nm in width, and a three-point bending test was applied to determine the elastic modulus using an AFM cantilever. The elastic moduli of single microfibrils prepared by TEMPO-oxidation and acid hydrolysis were 145.2 +/- 31.3 and 150.7 +/- 28.8 GPa, respectively. The result showed that the experimentally determined modulus of the highly crystalline tunicate microfibrils was in agreement with the elastic modulus of native cellulose crystals.

Quasi-one-dimensional arrangement of silver nanoparticles templated by cellulose microfibrils.

PubMed

Wu, Min; Kuga, Shigenori; Huang, Yong

2008-09-16

We demonstrate a simple, facile approach to the deposition of silver nanoparticles on the surface of cellulose microfibrils with a quasi-one-dimensional arrangement. The process involves the generation of aldehyde groups by oxidizing the surface of cellulose microfibrils and then the assembly of silver nanoparticles on the surface by means of the silver mirror reaction. The linear nature of the microfibrils and the relatively uniform surface chemical modification result in a uniform linear distribution of silver particles along the microfibrils. The effects of various reaction parameters, such as the reaction time for the reduction process and employed starting materials, have been investigated by transmission electron microscopy (TEM) and ultraviolet-visible spectroscopy. Additionally, the products were examined for their electric current-voltage characteristics, the results showing that these materials had an electric conductivity of approximately 5 S/cm, being different from either the oxidated cellulose or bulk silver materials by many orders of magnitude.

Unraveling cellulose microfibrils: a twisted tale.

PubMed

Hadden, Jodi A; French, Alfred D; Woods, Robert J

2013-10-01

Molecular dynamics (MD) simulations of cellulose microfibrils are pertinent to the paper, textile, and biofuels industries for their unique capacity to characterize dynamic behavior and atomic-level interactions with solvent molecules and cellulase enzymes. While high-resolution crystallographic data have established a solid basis for computational analysis of cellulose, previous work has demonstrated a tendency for modeled microfibrils to diverge from the linear experimental structure and adopt a twisted conformation. Here, we investigate the dependence of this twisting behavior on computational approximations and establish the theoretical basis for its occurrence. We examine the role of solvent, the effect of nonbonded force field parameters [partial charges and van der Waals (vdW) contributions], and the use of explicitly modeled oxygen lone pairs in both the solute and solvent. Findings suggest that microfibril twisting is favored by vdW interactions, and counteracted by both intrachain hydrogen bonds and solvent effects at the microfibril surface. Copyright © 2013 Wiley Periodicals, Inc.

Unraveling Cellulose Microfibrils: A Twisted Tale

PubMed Central

Hadden, Jodi A.; French, Alfred D.; Woods, Robert J.

2014-01-01

Molecular dynamics (MD) simulations of cellulose microfibrils are pertinent to the paper, textile, and biofuels industries for their unique capacity to characterize dynamic behavior and atomic-level interactions with solvent molecules and cellulase enzymes. While high-resolution crystallographic data have established a solid basis for computational analysis of cellulose, previous work has demonstrated a tendency for modeled microfibrils to diverge from the linear experimental structure and adopt a twisted conformation. Here, we investigate the dependence of this twisting behavior on computational approximations and establish the theoretical basis for its occurrence. We examine the role of solvent, the effect of nonbonded force field parameters [partial charges and van der Waals (vdW) contributions], and the use of explicitly modeled oxygen lone pairs in both the solute and solvent. Findings suggest that microfibril twisting is favored by vdW interactions, and counteracted by both intrachain hydrogen bonds and solvent effects at the microfibril surface. PMID:23681971

Tunicamycin Prevents Cellulose Microfibril Formation in Oocystis solitaria.

PubMed

Quader, H

1984-07-01

The effect of tunicamycin (TM) on the development of the cell wall in Oocystis solitaria has been investigated. It was found that 10 micromolar TM completely stops the assembly of new microfibrils as observed at the ultrastructural level. During cell wall formation, freeze fracture replicas of the E-face of the plasma membrane reveal two major substructures: the terminal complexes (TC), paired and unpaired, and the microfibril imprints extending from unpaired TCs. In cells treated for 3 hours or longer with TM, the TCs are no longer visible, whereas microfibril imprints are still present. Because of the reported highly selective mode of action of TM, our results implicate a role for lipid-intermediates in cellulose synthesis in O. solitaria. It is assumed that TM prevents the formation of a glycoprotein which probably is a fundamental part of the TCs and may act as a primer for the assembly of the microfibrils.

New Model of Wood Cell Wall Microfibril and Its Implications

Treesearch

Umesh P. Agarwal; Sally A. Ralph; Rick S. Reiner; Carlos Baez

2015-01-01

Traditionally it has been accepted that the cell walls are made up of microfibrils which are partly crystalline. However, based on the recently obtained Raman evidence that showed that the interior of the microfibril was significantly disordered and water accessible, a new model is proposed. In this model, the molecular chains of cellulose are still organized along the...

Novel high-strength biocomposites based on microfibrillated cellulose having nano-order-unit web-like network structure

NASA Astrophysics Data System (ADS)

Nakagaito, A. N.; Yano, H.

2005-01-01

A completely new kind of high-strength composite was manufactured using microfibrillated cellulose (MFC) derived from kraft pulp. Because of the unique structure of nano-order-scale interconnected fibrils and microfibrils greatly expanded in the surface area that characterizes MFC, it was possible to produce composites that exploit the extremely high strength of microfibrils. The Young’s modulus (E) and bending strength (σb) of composites using phenolic resin as binder achieved values up to 19 GPa and 370 MPa, respectively, with a density of 1.45 g/cm2, exhibiting outstanding mechanical properties for a plant-fiber-based composite.

Possible participation of transient sheets of 1. -->. 4-. beta. -glucans in the biosynthesis of cellulose I. [Acetobacter xylinum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colvin, J.R.

1983-01-01

It is suggested that a primary, essential stage in the biologic formation of a microfibril of cellulose I is an extracellular, lateral association of presynthesized (1..-->..4)-..beta..-D-glucans, by hydrogen bonding, to form long, thin sheets. These sheets then superimpose themselves nonenzymatically by London forces to form the nascent microfibril. The ends of the constituent glucans of the nascent microfibril may undergo extension or rearrangement of the type indicated by Maclachlan and colleagues. The formation of the metastable, native structure (cellulose I) may be deduced from the above suggestion as a natural consequence of closest packing of the sheets. The irreversibility ofmore » the change from cellulose I to cellulose II, either by mercerization or regeneration, also follows from the postulate. The suggestion also explains why cellulose microfibrils and chitin microfibrils may be formed contiguously in cell walls without interfering with each other. High-resolution electron micrographs of the tips of newly formed microfibrils of bacterial cellulose which had been very lightly negatively stained with sodium phosphotungstate are consistent with the suggestion. 33 references, 3 figures.« less

Molecular Origin of Strength and Stiffness in Bamboo Fibrils.

PubMed

Youssefian, Sina; Rahbar, Nima

2015-06-08

Bamboo, a fast-growing grass, has a higher strength-to-weight ratio than steel and concrete. The unique properties of bamboo come from the natural composite structure of fibers that consists mainly of cellulose microfibrils in a matrix of intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Here, we have used atomistic simulations to study the mechanical properties of and adhesive interactions between the materials in bamboo fibers. With this aim, we have developed molecular models of lignin, hemicellulose and LCC structures to study the elastic moduli and the adhesion energies between these materials and cellulose microfibril faces. Good agreement was observed between the simulation results and experimental data. It was also shown that the hemicellulose model has stronger mechanical properties than lignin while lignin exhibits greater tendency to adhere to cellulose microfibrils. The study suggests that the abundance of hydrogen bonds in hemicellulose chains is responsible for improving the mechanical behavior of LCC. The strong van der Waals forces between lignin molecules and cellulose microfibril is responsible for higher adhesion energy between LCC and cellulose microfibrils. We also found out that the amorphous regions of cellulose microfibrils are the weakest interfaces in bamboo fibrils. Hence, they determine the fibril strength.

Molecular Origin of Strength and Stiffness in Bamboo Fibrils

PubMed Central

Youssefian, Sina; Rahbar, Nima

2015-01-01

Bamboo, a fast-growing grass, has a higher strength-to-weight ratio than steel and concrete. The unique properties of bamboo come from the natural composite structure of fibers that consists mainly of cellulose microfibrils in a matrix of intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Here, we have used atomistic simulations to study the mechanical properties of and adhesive interactions between the materials in bamboo fibers. With this aim, we have developed molecular models of lignin, hemicellulose and LCC structures to study the elastic moduli and the adhesion energies between these materials and cellulose microfibril faces. Good agreement was observed between the simulation results and experimental data. It was also shown that the hemicellulose model has stronger mechanical properties than lignin while lignin exhibits greater tendency to adhere to cellulose microfibrils. The study suggests that the abundance of hydrogen bonds in hemicellulose chains is responsible for improving the mechanical behavior of LCC. The strong van der Waals forces between lignin molecules and cellulose microfibril is responsible for higher adhesion energy between LCC and cellulose microfibrils. We also found out that the amorphous regions of cellulose microfibrils are the weakest interfaces in bamboo fibrils. Hence, they determine the fibril strength. PMID:26054045

Molecular Origin of Strength and Stiffness in Bamboo Fibrils

NASA Astrophysics Data System (ADS)

Youssefian, Sina; Rahbar, Nima

2015-06-01

Bamboo, a fast-growing grass, has a higher strength-to-weight ratio than steel and concrete. The unique properties of bamboo come from the natural composite structure of fibers that consists mainly of cellulose microfibrils in a matrix of intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Here, we have used atomistic simulations to study the mechanical properties of and adhesive interactions between the materials in bamboo fibers. With this aim, we have developed molecular models of lignin, hemicellulose and LCC structures to study the elastic moduli and the adhesion energies between these materials and cellulose microfibril faces. Good agreement was observed between the simulation results and experimental data. It was also shown that the hemicellulose model has stronger mechanical properties than lignin while lignin exhibits greater tendency to adhere to cellulose microfibrils. The study suggests that the abundance of hydrogen bonds in hemicellulose chains is responsible for improving the mechanical behavior of LCC. The strong van der Waals forces between lignin molecules and cellulose microfibril is responsible for higher adhesion energy between LCC and cellulose microfibrils. We also found out that the amorphous regions of cellulose microfibrils are the weakest interfaces in bamboo fibrils. Hence, they determine the fibril strength.

Influence of drying of chara cellulose on length/length distribution of microfibrils after acid hydrolysis.

PubMed

Horikawa, Yoshiki; Shimizu, Michiko; Saito, Tsuguyuki; Isogai, Akira; Imai, Tomoya; Sugiyama, Junji

2018-04-01

Chara is a genus of freshwater alga that is evolutionarily observed at the aquatic-terrestrial boundary, whose cellulose microfibrils are similar to those of terrestrial plants regarding the crystallinity and biosynthesis of cellulose. Oven-dried and never-dried celluloses samples were prepared from chara. Terrestrial plant cellulose samples were used as references. The lengths and length distributions of oven-dried and never-dried chara cellulose microfibrils after acid hydrolysis with or without pretreatment by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, which was used for efficient fibrillation of acid-hydrolyzed products, were observed by transmission electron microscopy. All terrestrial plant celluloses and oven-dried chara cellulose had short nanocrystal-like morphologies of 100-300 nm in length after acid hydrolysis. In contrast, the never-dried chara cellulose had much longer microfibrils of ∼970 nm in length after acid hydrolysis. These results indicated that disordered regions present periodically along the cellulose microfibrils, which cause the formation of cellulose nanocrystals after acid hydrolysis, are not present in inherent chara cellulose microfibrils in water, but are formed artificially under drying or dehydration conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

The mechanism of formation of Cellulose-like microfibrils in a cell-free system from Acetobacter xylinum.

PubMed

Colvin, J R

1980-07-01

The mechanism of formation of cellulose-like microfibrils by a non-soluble, particulate enzyme and uridine diphosphoglucose (UDPG) in a cell-free system from Acetobacter xylinum was studied by transmission electron microscopy and X-ray diffraction. The suspension of particles to which the enzyme is adsorbed is composed of whole, dense ovoids, 50-250 nm long when wet, of fragments of the ovoids, and amorphous substance. There is a typical unit membrane around each ovoid but initially there is no trace of fibrillar material in the suspension. When the suspension of particles is incubated with UDPG, linear wisps of fibrils are produced which associate rapidly to form longer and wider threads, especially in 0.01 M NaCl. There is no visible attachment of the wisps to the particles. After 20 min incubation, threads with the typical morphology of cellulose microfibrils are formed that later tend to become entangled in clumps. The microfibrils are insoluble in hot, aqueous, alkaline solutions and resistant to the action of trypsin, but may be degraded by glusulase. After treatment with 1 M NaOH at 100° C or with cold 18% NaOH they show an X-ray diffraction pattern which resembles that of Cellulose II from mercerized, authentic bacterial cellulose. Incorporation of radioactive glucose into the insoluble residue is enhanced by drying of the cellulose microfibrils before alkaline digestion and especially by the addition of a gross excess of carrier cellulose after incubation. In this system there is no evidence for participation of linear, axial, synthesizing sites on the cell wall of the bacterium or for ordered, organized granules in the assembly of the microfibrils. That is, cellulose-like microfibrils may be formed in a cell-free system without the action of any of the previously suggested cell organelles. In addition, these observations are consistent with a previously described notion of a transient, hydrated, nascent, bacterial cellulose microfibril. The possibility that cellulose microfibrils of green plants may be formed in the same way is considered.

Defining Determinants and Dynamics and Cellulose Microfibril Biosynthesis, Assembly and Degredation OSP Number: 63079/A001

DOE Office of Scientific and Technical Information (OSTI.GOV)

None, None

The central paradigm for converting plant biomass into soluble sugars for subsequent conversion to transportation fuels involves the enzymatic depolymerization of lignocellulosic plant cell walls by microbial enzymes. Despite decades of intensive research, this is still a relatively inefficient process, due largely to the recalcitrance and enormous complexity of the substrate. A major obstacle is still insufficient understanding of the detailed structure and biosynthesis of major wall components, including cellulose. For example, although cellulose is generally depicted as rigid, insoluble, uniformly crystalline microfibrils that are resistant to enzymatic degradation, the in vivo structures of plant cellulose microfibrils are surprisingly complex.more » Crystallinity is frequently disrupted, for example by dislocations and areas containing chain ends, resulting in “amorphous” disordered regions. Importantly, microfibril structure and the relative proportions of crystalline and non-crystalline disordered surface regions vary substantially and yet the molecular mechanisms by which plants regulate microfibril crystallinity, and other aspects of microfibril architecture, are still entirely unknown. This obviously has a profound effect on susceptibility to enzymatic hydrolysis and so this is a critical area of research in order to characterize and optimize cellulosic biomass degradation. The entire field of cell wall assembly, as distinct from polysaccharide biosynthesis, and the degree to which they are coupled, are relatively unexplored, despite the great potential for major advances in addressing the hurdle of biomass recalcitrance. Our overarching hypothesis was that identification of the molecular machinery that determine microfibril polymerization, deposition and structure will allow the design of more effective degradative systems, and the generation of cellulosic materials with enhanced and predictable bioconversion characteristics. Our experimental framework had been based on the idea that the most effective way to address this long standing and highly complex question is to adopt a broad ‘systems approach’. Accordingly, we assembled a multi-disciplinary collaborative team with collective expertise in plant biology and molecular genetics, polymer structure and chemistry, enzyme biochemistry and biochemical engineering. We used a spectrum of cutting edge technologies, including plant functional genomics, chemical genetics, live cell imaging, advanced microscopy, high energy X-ray spectroscopy and nanotechnology, to study the molecular determinants of cellulose microfibril structure. Importantly, this research effort was closely coupled with an analytical pipeline to characterize the effects of altering microfibril architecture on bioconversion potential, with the goal of generating predictive models to help guide the identification, development and implementation of new feedstocks. This project therefore spanned core basic science and applied research, in line with the goals of the program. Over the course of the project, accomplishments included: - Establishing platforms through reverse and forward genetics to identify and manipulate candidate genes that influence cellulose microfibril synthesis and structure in a model C3 grass, Brachypodium distachyon and a model C4 grass Setaria viridis; Identifying and characterizing the effects of a number of cellulose biosynthesis inhibitors (CBIs), and particularly those that target monocots with the aim of generating resistance loci; Developing protocols for the use of high energy X-ray diffraction (XRD) to study the structure and organization of cellulose microfibrils in plant walls, notably those in Arabidopsis and Brachypodium; Using the chemical and genetic based inhibition strategies to develop new mechanistic models of cellulose microfibril crystallization, and of how altering microfibril architecture influences digestibility.« less

Homogeneous suspensions of individualized microfibrils from TEMPO-catalyzed oxidation of native cellulose.

PubMed

Saito, Tsuguyuki; Nishiyama, Yoshiharu; Putaux, Jean-Luc; Vignon, Michel; Isogai, Akira

2006-06-01

Never-dried native celluloses (bleached sulfite wood pulp, cotton, tunicin, and bacterial cellulose) were disintegrated into individual microfibrils after oxidation mediated by the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical followed by a homogenizing mechanical treatment. When oxidized with 3.6 mmol of NaClO per gram of cellulose, almost the totality of sulfite wood pulp and cotton were readily disintegrated into long individual microfibrils by a treatment with a Waring Blendor, yielding transparent and highly viscous suspensions. When observed by transmission electron microscopy, the wood pulp and cotton microfibrils exhibited a regular width of 3-5 nm. Tunicin and bacterial cellulose could be disintegrated by sonication. A bulk degree of oxidation of about 0.2 per one anhydroglucose unit of cellulose was necessary for a smooth disintegration of sulfite wood pulp, whereas only small amounts of independent microfibrils were obtained at lower oxidation levels. This limiting degree of oxidation decreased in the following order: sulfite wood pulp > cotton > bacterial cellulose, tunicin.

Mechanical Properties Versus Morphology of Ordered Polymers. Volume 6

DTIC Science & Technology

1986-06-01

of PBT fiber was examined by TEM of epoxy impregnated fibers. An oriented network of microfibrils with typical fibril diameters of about 80-100A was...observed. We suggest that these microfibrils are the fundamental structural elements of the fiber. Thus knowledge of the mechanism by which this initial...benzobisthiazole) fiber was examined by transmission electron 1 microscopy of epoxy impregnated fibers. An oriented network of microfibrils with typical

Probing crystal structure and mesoscale assembly of cellulose microfibrils in plant cell walls, tunicate tests, and bacterial films using vibrational sum frequency generation (SFG) spectroscopy.

PubMed

Lee, Christopher M; Kafle, Kabindra; Park, Yong Bum; Kim, Seong H

2014-06-14

This study reports that the noncentrosymmetry and phase synchronization requirements of the sum frequency generation (SFG) process can be used to distinguish the three-dimensional organization of crystalline cellulose distributed in amorphous matrices. Crystalline cellulose is produced as microfibrils with a few nanometer diameters by plants, tunicates, and bacteria. Crystalline cellulose microfibrils are embedded in wall matrix polymers and assembled into hierarchical structures that are precisely designed for specific biological and mechanical functions. The cellulose microfibril assemblies inside cell walls are extremely difficult to probe. The comparison of vibrational SFG spectra of uniaxially-aligned and disordered films of cellulose Iβ nanocrystals revealed that the spectral features cannot be fully explained with the crystallographic unit structure of cellulose. The overall SFG intensity, the alkyl peak shape, and the alkyl/hydroxyl intensity ratio are sensitive to the lateral packing and net directionality of the cellulose microfibrils within the SFG coherence length scale. It was also found that the OH SFG stretch peaks could be deconvoluted to find the polymorphic crystal structures of cellulose (Iα and Iβ). These findings were used to investigate the cellulose crystal structure and mesoscale cellulose microfibril packing in intact plant cell walls, tunicate tests, and bacterial films.

The assembly of cellulose microfibrils in Valonia macrophysa Kütz.

PubMed

Itoh, T; Brown, R M

1984-03-01

The assembly of cellulose microfibrils was investigated in artificially induced protoplasts of the alga, Valonia macrophysa (Siphonocladales). Primary-wall microfibrills, formed within 72 h of protoplast induction, are randomly oriented. Secondary-wall lamellae, which are produced within 96 h after protoplast induction, have more than three orientations of highly ordered microfibrils. The innermost, recently deposited micofibrils are not parallel with the cortical microtubules, thus indicating a more indirect role of microtubules in the orientation of microfibrils. Fine filamentous structures with a periodicity of 5.0-5.5 nm and the dimensions of actin were observed adjacent to the plasma membrane. Linear cellulose-terminal synthesizing complexes (TCs) consisting of three rows, each with 30-40 particles, were observed not only on the E fracture (EF) but also on P fracture (PF) faces of the plasma membrane. The TC appears to span both faces of the bimolecular leaflet. The average length of the TC is 350 nm, and the number of TCs per unit area during primary-wall synthesis is 1 per μm(2). Neither paired TCs nor granule bands characteristic of Oocystis were observed. Changes in TC structure and distribution during the conversion from primary- to secondary-wall formation have been described. Cellulose microfibril assembly in Valonia is discussed in relation to the process among other eukaryotic systems.

Modeling of the morphological change of cellulose microfibrils caused with aqueous NaOH solution: the longitudinal contraction and laterally swelling during decrystallization.

PubMed

Nakano, Takato

2017-04-01

The conformation of cellulose microfibrils treated with aqueous NaOH was modeled as partially decrystallized cellulose chains before completing conversion to cellulose II, in order to elucidate the change in morphology of ramie fiber caused by NaOH treatment. Equations for the relative length and width of the microfibrils were derived on the basis of partially decrystallized microfibrils modeling. Each equation contains four parameters, n, β, w c , and c r , which correspond to the number of glucose residues between periodic defects along the untreated ramie cellulose microfibrils, the extension ratio of amorphous cellulose chain along length, the cross-section crystallinity, and the correction term of crystallinity, respectively. The validity of the derived equations was confirmed by two types of simulations. One is performed using experimental data L/L 0 and W/W 0 as a function of crystallinity, while the other is done using the relationship between the relative length and width obtained from the experimental data, which is independent of crystallinity, was performed. The best-fit simulation was obtained under n = 277, β = 2.813, and c r w c  = 0.671 for the former and under n = 301 and β = 2.792 for the latter. These values of n and β correspond closely to the values reported in references for ramie microfibrils. Both simulation results show that macroscopic changes in the morphology of ramie fibers is attributable to the changes in cellulose chain conformation in the decrystallized regions created along the microfibrils upon NaOH treatment.

Disorganization of Cortical Microtubules Stimulates Tangential Expansion and Reduces the Uniformity of Cellulose Microfibril Alignment among Cells in the Root of Arabidopsis1

PubMed Central

Baskin, Tobias I.; Beemster, Gerrit T.S.; Judy-March, Jan E.; Marga, Françoise

2004-01-01

To test the role of cortical microtubules in aligning cellulose microfibrils and controlling anisotropic expansion, we exposed Arabidopsis thaliana roots to moderate levels of the microtubule inhibitor, oryzalin. After 2 d of treatment, roots grow at approximately steady state. At that time, the spatial profiles of relative expansion rate in length and diameter were quantified, and roots were cryofixed, freeze-substituted, embedded in plastic, and sectioned. The angular distribution of microtubules as a function of distance from the tip was quantified from antitubulin immunofluorescence images. In alternate sections, the overall amount of alignment among microfibrils and their mean orientation as a function of position was quantified with polarized-light microscopy. The spatial profiles of relative expansion show that the drug affects relative elongation and tangential expansion rates independently. The microtubule distributions averaged to transverse in the growth zone for all treatments, but on oryzalin the distributions became broad, indicating poorly organized arrays. At a subcellular scale, cellulose microfibrils in oryzalin-treated roots were as well aligned as in controls; however, the mean alignment direction, while consistently transverse in the controls, was increasingly variable with oryzalin concentration, meaning that microfibril orientation in one location tended to differ from that of a neighboring location. This conclusion was confirmed by direct observations of microfibrils with field-emission scanning electron microscopy. Taken together, these results suggest that cortical microtubules ensure microfibrils are aligned consistently across the organ, thereby endowing the organ with a uniform mechanical structure. PMID:15299138

Degree of polymerization of glucan chains shapes the structure fluctuations and melting thermodynamics of a cellulose microfibril.

PubMed

Chang, Rakwoo; Gross, Adam S; Chu, Jhih-Wei

2012-07-19

A Staggered LATtice (SLAT) model is developed for modeling cellulose microfibrils. The simple representation of molecular packing and interactions employed in SLAT allows simulations of structure fluctuations and phase transition of cellulose microfibrils at sufficiently long and large scales for comparison with experiments. Glucan chains in the microfibril are modeled as connected monomers, each corresponding to a cellobiose subunit, and the surrounding space around the cellulose is composed of solvent cells. Interaction parameters of monomer-monomer interactions were parametrized based on the results of atomistic molecular dynamics simulations. The monomer-solvent interaction was optimized to give a melting temperature of ∼695 K for the 36-glucan chain model cellulose microfibril, which is consistent with the estimation based on experimental data. Monte Carlo simulations of the SLAT model also capture experimentally measured X-ray diffraction patterns of cellulose as a function of temperature, including the region of melting transition, as well as predict the highly flexible regions in the microfibril. Beyond the diameter of ∼3 nm, we found that melting temperature of the cellulose microfibril is not significantly shifted by changing the thickness. On the other hand, a slight decrease in the degree of polymerization of glucan chains is shown to enhance structure fluctuations through the ends of glucan chains, i.e., the defect sites, and thereby significantly reduce the melting temperature. Analysis of the sizes, densities, and lifetimes of defect structures in the microfibril indicates a significant extent of fluctuations on the surfaces even at room temperature and that defect statistics are strong but distinct functions of temperature and solvent quality. The SLAT model is the first of its kind for simulating cellulosic materials, and this work shows that it can be used to incorporate information obtained from atomistic simulations and experimental data to enable the aforementioned findings through computation.

Defining the hierarchical organisation of collagen VI microfibrils at nanometre to micrometre length scales.

PubMed

Godwin, Alan R F; Starborg, Tobias; Sherratt, Michael J; Roseman, Alan M; Baldock, Clair

2017-04-01

Extracellular matrix microfibrils are critical components of connective tissues with a wide range of mechanical and cellular signalling functions. Collagen VI is a heteromeric network-forming collagen which is expressed in tissues such as skin, lung, blood vessels and articular cartilage where it anchors cells into the matrix allowing for transduction of biochemical and mechanical signals. It is not understood how collagen VI is arranged into microfibrils or how these microfibrils are arranged into tissues. Therefore we have characterised the hierarchical organisation of collagen VI across multiple length scales. The frozen hydrated nanostructure of purified collagen VI microfibrils was reconstructed using cryo-TEM. The bead region has a compact hollow head and flexible tail regions linked by the collagenous interbead region. Serial block face SEM imaging coupled with electron tomography of the pericellular matrix (PCM) of murine articular cartilage revealed that the PCM has a meshwork-like organisation formed from globular densities ∼30nm in diameter. These approaches can characterise structures spanning nanometer to millimeter length scales to define the nanostructure of individual collagen VI microfibrils and the micro-structural organisation of these fibrils within tissues to help in the future design of better mimetics for tissue engineering. Cartilage is a connective tissue rich in extracellular matrix molecules and is tough and compressive to cushion the bones of joints. However, in adults cartilage is poorly repaired after injury and so this is an important target for tissue engineering. Many connective tissues contain collagen VI, which forms microfibrils and networks but we understand very little about these assemblies or the tissue structures they form. Therefore, we have use complementary imaging techniques to image collagen VI microfibrils from the nano-scale to the micro-scale in order to understand the structure and the assemblies it forms. These findings will help to inform the future design of scaffolds to mimic connective tissues in regenerative medicine applications. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The Axial Compressive Strength of High Performance Polymer Fibers

DTIC Science & Technology

1985-03-01

consists of axially oriented graphitic microfibrils that have the strong and stiff graphite crystal basal plane oriented parallel to the long axis of the... microfibrils [3,4]. The synthetic rigid polymer fibers are represented by only one commercial material: the PPTA fibers produced by E.I. DuPont de...and/or microfibrils is presented. A potential energy balance analysis is used to calculate critical stresses for the onset of compressive buckling

Structural and mechanical design of tissue interfaces in the giant reed Arundo donax.

PubMed

Rüggeberg, Markus; Burgert, Ingo; Speck, Thomas

2010-03-06

The culms of the giant reed Arundo donax represent slender tube-like structures. Several nodes along the culm, a ring of sclerenchymatous fibres in the periphery of the culm wall and numerous isolated vascular bundles enclosed by fibre rings in the culm wall function as stiffening elements. The bundles are embedded in lignified parenchyma. Micromechanical analysis indicated differences in stiffness between the individual tissues of more than one order of magnitude. In case of abrupt transitions in stiffness at the interfaces, stress discontinuities arise under dynamic loads. This eventually leads to critical shear stresses at cell ends, and culm failure may be initiated at these points. Pronounced mechanical differences between individual tissues can be compromised by gradual transitions at their interfaces. Ultrastructural and spectroscopic investigations with high spatial resolution revealed a gradual transition of cell parameters (cell wall area fraction and cell length). However, cell wall parameters (cellulose microfibril angle and lignin content) showed abrupt transitions or remained almost constant across the interfaces between various tissues. The design principles found at the interfaces between tissues in the culm walls of A. donax are discussed as an adaptation strategy to mechanical loads at different levels of hierarchy.

Structural and mechanical design of tissue interfaces in the giant reed Arundo donax

PubMed Central

Rüggeberg, Markus; Burgert, Ingo; Speck, Thomas

2010-01-01

The culms of the giant reed Arundo donax represent slender tube-like structures. Several nodes along the culm, a ring of sclerenchymatous fibres in the periphery of the culm wall and numerous isolated vascular bundles enclosed by fibre rings in the culm wall function as stiffening elements. The bundles are embedded in lignified parenchyma. Micromechanical analysis indicated differences in stiffness between the individual tissues of more than one order of magnitude. In case of abrupt transitions in stiffness at the interfaces, stress discontinuities arise under dynamic loads. This eventually leads to critical shear stresses at cell ends, and culm failure may be initiated at these points. Pronounced mechanical differences between individual tissues can be compromised by gradual transitions at their interfaces. Ultrastructural and spectroscopic investigations with high spatial resolution revealed a gradual transition of cell parameters (cell wall area fraction and cell length). However, cell wall parameters (cellulose microfibril angle and lignin content) showed abrupt transitions or remained almost constant across the interfaces between various tissues. The design principles found at the interfaces between tissues in the culm walls of A. donax are discussed as an adaptation strategy to mechanical loads at different levels of hierarchy. PMID:19726440

Symposium on Wood Moisture Content - Temperature and Humidity Relationships Held at Blacksburg, Virginia on October 29, 1979.

DTIC Science & Technology

1979-10-29

34Recommended We all know this figure, from Al Stamm’s book moisture-content averages for interior-fin- on ood and Cellulose Science, I’m sure. It ishing...is about Stamm: Wood and Cellulose Science 0.100 in. of mercury. Now, if temperature alone is increased, let’s say to 75’ F, EMC The second figure that...of as a st ruc tural sys ten involv ing f il/men/to//s tie ope’ra/tion of lesser it tractivye forces microfibrils , rmostly celliuloqir nd

Cellulose microfibril crystallinity is reduced by mutating C-terminal transmembrane region residues CESA1A903V and CESA3T942I of cellulose synthase.

PubMed

Harris, Darby M; Corbin, Kendall; Wang, Tuo; Gutierrez, Ryan; Bertolo, Ana L; Petti, Carloalberto; Smilgies, Detlef-M; Estevez, José Manuel; Bonetta, Dario; Urbanowicz, Breeanna R; Ehrhardt, David W; Somerville, Chris R; Rose, Jocelyn K C; Hong, Mei; Debolt, Seth

2012-03-13

The mechanisms underlying the biosynthesis of cellulose in plants are complex and still poorly understood. A central question concerns the mechanism of microfibril structure and how this is linked to the catalytic polymerization action of cellulose synthase (CESA). Furthermore, it remains unclear whether modification of cellulose microfibril structure can be achieved genetically, which could be transformative in a bio-based economy. To explore these processes in planta, we developed a chemical genetic toolbox of pharmacological inhibitors and corresponding resistance-conferring point mutations in the C-terminal transmembrane domain region of CESA1(A903V) and CESA3(T942I) in Arabidopsis thaliana. Using (13)C solid-state nuclear magnetic resonance spectroscopy and X-ray diffraction, we show that the cellulose microfibrils displayed reduced width and an additional cellulose C4 peak indicative of a degree of crystallinity that is intermediate between the surface and interior glucans of wild type, suggesting a difference in glucan chain association during microfibril formation. Consistent with measurements of lower microfibril crystallinity, cellulose extracts from mutated CESA1(A903V) and CESA3(T942I) displayed greater saccharification efficiency than wild type. Using live-cell imaging to track fluorescently labeled CESA, we found that these mutants show increased CESA velocities in the plasma membrane, an indication of increased polymerization rate. Collectively, these data suggest that CESA1(A903V) and CESA3(T942I) have modified microfibril structure in terms of crystallinity and suggest that in plants, as in bacteria, crystallization biophysically limits polymerization.

Cellulose microfibril crystallinity is reduced by mutating C-terminal transmembrane region residues CESA1A903V and CESA3T942I of cellulose synthase

PubMed Central

Harris, Darby M.; Corbin, Kendall; Wang, Tuo; Gutierrez, Ryan; Bertolo, Ana L.; Petti, Carloalberto; Smilgies, Detlef-M.; Estevez, José Manuel; Bonetta, Dario; Urbanowicz, Breeanna R.; Ehrhardt, David W.; Somerville, Chris R.; Rose, Jocelyn K. C.; Hong, Mei; DeBolt, Seth

2012-01-01

The mechanisms underlying the biosynthesis of cellulose in plants are complex and still poorly understood. A central question concerns the mechanism of microfibril structure and how this is linked to the catalytic polymerization action of cellulose synthase (CESA). Furthermore, it remains unclear whether modification of cellulose microfibril structure can be achieved genetically, which could be transformative in a bio-based economy. To explore these processes in planta, we developed a chemical genetic toolbox of pharmacological inhibitors and corresponding resistance-conferring point mutations in the C-terminal transmembrane domain region of CESA1A903V and CESA3T942I in Arabidopsis thaliana. Using 13C solid-state nuclear magnetic resonance spectroscopy and X-ray diffraction, we show that the cellulose microfibrils displayed reduced width and an additional cellulose C4 peak indicative of a degree of crystallinity that is intermediate between the surface and interior glucans of wild type, suggesting a difference in glucan chain association during microfibril formation. Consistent with measurements of lower microfibril crystallinity, cellulose extracts from mutated CESA1A903V and CESA3T942I displayed greater saccharification efficiency than wild type. Using live-cell imaging to track fluorescently labeled CESA, we found that these mutants show increased CESA velocities in the plasma membrane, an indication of increased polymerization rate. Collectively, these data suggest that CESA1A903V and CESA3T942I have modified microfibril structure in terms of crystallinity and suggest that in plants, as in bacteria, crystallization biophysically limits polymerization. PMID:22375033

Cellulose microfibril structure: inspirations from plant diversity

NASA Astrophysics Data System (ADS)

Roberts, A. W.

2018-03-01

Cellulose microfibrils are synthesized at the plasma membrane by cellulose synthase catalytic subunits that associate to form cellulose synthesis complexes. Variation in the organization of these complexes underlies the variation in cellulose microfibril structure among diverse organisms. However, little is known about how the catalytic subunits interact to form complexes with different morphologies. We are using an evolutionary approach to investigate the roles of different catalytic subunit isoforms in organisms that have rosette-type cellulose synthesis complexes.

Cobtorin target analysis reveals that pectin functions in the deposition of cellulose microfibrils in parallel with cortical microtubules.

PubMed

Yoneda, Arata; Ito, Takuya; Higaki, Takumi; Kutsuna, Natsumaro; Saito, Tamio; Ishimizu, Takeshi; Osada, Hiroyuki; Hasezawa, Seiichiro; Matsui, Minami; Demura, Taku

2010-11-01

Cellulose and pectin are major components of primary cell walls in plants, and it is believed that their mechanical properties are important for cell morphogenesis. It has been hypothesized that cortical microtubules guide the movement of cellulose microfibril synthase in a direction parallel with the microtubules, but the mechanism by which this alignment occurs remains unclear. We have previously identified cobtorin as an inhibitor that perturbs the parallel relationship between cortical microtubules and nascent cellulose microfibrils. In this study, we searched for the protein target of cobtorin, and we found that overexpression of pectin methylesterase and polygalacturonase suppressed the cobtorin-induced cell-swelling phenotype. Furthermore, treatment with polygalacturonase restored the deposition of cellulose microfibrils in the direction parallel with cortical microtubules, and cobtorin perturbed the distribution of methylated pectin. These results suggest that control over the properties of pectin is important for the deposition of cellulose microfibrils and/or the maintenance of their orientation parallel with the cortical microtubules. © 2010 The Authors. The Plant Journal © 2010 Blackwell Publishing Ltd.

Spider Silk-CBD-Cellulose Nanocrystal Composites: Mechanism of Assembly

PubMed Central

Meirovitch, Sigal; Shtein, Zvi; Ben-Shalom, Tal; Lapidot, Shaul; Tamburu, Carmen; Hu, Xiao; Kluge, Jonathan A.; Raviv, Uri; Kaplan, David L.; Shoseyov, Oded

2016-01-01

The fabrication of cellulose-spider silk bio-nanocomposites comprised of cellulose nanocrystals (CNCs) and recombinant spider silk protein fused to a cellulose binding domain (CBD) is described. Silk-CBD successfully binds cellulose, and unlike recombinant silk alone, silk-CBD self-assembles into microfibrils even in the absence of CNCs. Silk-CBD-CNC composite sponges and films show changes in internal structure and CNC alignment related to the addition of silk-CBD. The silk-CBD sponges exhibit improved thermal and structural characteristics in comparison to control recombinant spider silk sponges. The glass transition temperature (Tg) of the silk-CBD sponge was higher than the control silk sponge and similar to native dragline spider silk fibers. Gel filtration analysis, dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and cryo-transmission electron microscopy (TEM) indicated that silk-CBD, but not the recombinant silk control, formed a nematic liquid crystalline phase similar to that observed in native spider silk during the silk spinning process. Silk-CBD microfibrils spontaneously formed in solution upon ultrasonication. We suggest a model for silk-CBD assembly that implicates CBD in the central role of driving the dimerization of spider silk monomers, a process essential to the molecular assembly of spider-silk nanofibers and silk-CNC composites. PMID:27649169

Spider Silk-CBD-Cellulose Nanocrystal Composites: Mechanism of Assembly.

PubMed

Meirovitch, Sigal; Shtein, Zvi; Ben-Shalom, Tal; Lapidot, Shaul; Tamburu, Carmen; Hu, Xiao; Kluge, Jonathan A; Raviv, Uri; Kaplan, David L; Shoseyov, Oded

2016-09-18

The fabrication of cellulose-spider silk bio-nanocomposites comprised of cellulose nanocrystals (CNCs) and recombinant spider silk protein fused to a cellulose binding domain (CBD) is described. Silk-CBD successfully binds cellulose, and unlike recombinant silk alone, silk-CBD self-assembles into microfibrils even in the absence of CNCs. Silk-CBD-CNC composite sponges and films show changes in internal structure and CNC alignment related to the addition of silk-CBD. The silk-CBD sponges exhibit improved thermal and structural characteristics in comparison to control recombinant spider silk sponges. The glass transition temperature (Tg) of the silk-CBD sponge was higher than the control silk sponge and similar to native dragline spider silk fibers. Gel filtration analysis, dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and cryo-transmission electron microscopy (TEM) indicated that silk-CBD, but not the recombinant silk control, formed a nematic liquid crystalline phase similar to that observed in native spider silk during the silk spinning process. Silk-CBD microfibrils spontaneously formed in solution upon ultrasonication. We suggest a model for silk-CBD assembly that implicates CBD in the central role of driving the dimerization of spider silk monomers, a process essential to the molecular assembly of spider-silk nanofibers and silk-CNC composites.

Analysis of Enzymatic Degradation of Cellulose Microfibrils using Quantitative Surface Plasmon Resonance Imaging

NASA Astrophysics Data System (ADS)

Reiter, Kyle; Raegen, Adam; Allen, Scott; Quirk, Amanda; Clarke, Anthony; Lipkowski, Jacek; Dutcher, John

2013-03-01

Cellulose is the largest component of biomass on Earth and, as a result, is a significant potential energy source. The production of cellulosic ethanol as a fuel source requires conversion of cellulose fibers into fermentable sugars. Increasing our understanding of the action of cellulose enzymes (cellulases) on cellulose microfibrils is an important step in developing more efficient industrial processes for the production of cellulosic ethanol. We have used a custom designed Surface Plasmon Resonance imaging (SPRi) device to study the action of cellulases from the Hypocrea jecorinasecretome on bacterial cellulose microfibrils. This has allowed us to determine the rates of action and extent of degradation of cellulose microfibrils on exposure to both individual cellulases and combinations of different classes of cellulases, which has allowed us to investigate synergistic interactions between the cellulases.

Enhanced cellulose orientation analysis in complex model plant tissues.

PubMed

Rüggeberg, Markus; Saxe, Friederike; Metzger, Till H; Sundberg, Björn; Fratzl, Peter; Burgert, Ingo

2013-09-01

The orientation distribution of cellulose microfibrils in the plant cell wall is a key parameter for understanding anisotropic plant growth and mechanical behavior. However, precisely visualizing cellulose orientation in the plant cell wall has ever been a challenge due to the small size of the cellulose microfibrils and the complex network of polymers in the plant cell wall. X-ray diffraction is one of the most frequently used methods for analyzing cellulose orientation in single cells and plant tissues, but the interpretation of the diffraction images is complex. Traditionally, circular or square cells and Gaussian orientation of the cellulose microfibrils have been assumed to elucidate cellulose orientation from the diffraction images. However, the complex tissue structures of common model plant systems such as Arabidopsis or aspen (Populus) require a more sophisticated approach. We present an evaluation procedure which takes into account the precise cell geometry and is able to deal with complex microfibril orientation distributions. The evaluation procedure reveals the entire orientation distribution of the cellulose microfibrils, reflecting different orientations within the multi-layered cell wall. By analyzing aspen wood and Arabidopsis stems we demonstrate the versatility of this method and show that simplifying assumptions on geometry and orientation distributions can lead to errors in the calculated microfibril orientation pattern. The simulation routine is intended to be used as a valuable tool for nanostructural analysis of plant cell walls and is freely available from the authors on request. Copyright © 2013 Elsevier Inc. All rights reserved.

Organization of pectic arabinan and galactan side chains in association with cellulose microfibrils in primary cell walls and related models envisaged.

PubMed

Zykwinska, Agata; Thibault, Jean-François; Ralet, Marie-Christine

2007-01-01

The structure of arabinan and galactan domains in association with cellulose microfibrils was investigated using enzymatic and alkali degradation procedures. Sugar beet and potato cell wall residues (called 'natural' composites), rich in pectic neutral sugar side chains and cellulose, as well as 'artificial' composites, created by in vitro adsorption of arabinan and galactan side chains onto primary cell wall cellulose, were studied. These composites were sequentially treated with enzymes specific for pectic side chains and hot alkali. The degradation approach used showed that most of the arabinan and galactan side chains are in strong interaction with cellulose and are not hydrolysed by pectic side chain-degrading enzymes. It seems unlikely that isolated arabinan and galactan chains are able to tether adjacent microfibrils. However, cellulose microfibrils may be tethered by different pectic side chains belonging to the same pectic macromolecule.

3D electron tomography of pretreated biomass informs atomic modeling of cellulose microfibrils.

PubMed

Ciesielski, Peter N; Matthews, James F; Tucker, Melvin P; Beckham, Gregg T; Crowley, Michael F; Himmel, Michael E; Donohoe, Bryon S

2013-09-24

Fundamental insights into the macromolecular architecture of plant cell walls will elucidate new structure-property relationships and facilitate optimization of catalytic processes that produce fuels and chemicals from biomass. Here we introduce computational methodology to extract nanoscale geometry of cellulose microfibrils within thermochemically treated biomass directly from electron tomographic data sets. We quantitatively compare the cell wall nanostructure in corn stover following two leading pretreatment strategies: dilute acid with iron sulfate co-catalyst and ammonia fiber expansion (AFEX). Computational analysis of the tomographic data is used to extract mathematical descriptions for longitudinal axes of cellulose microfibrils from which we calculate their nanoscale curvature. These nanostructural measurements are used to inform the construction of atomistic models that exhibit features of cellulose within real, process-relevant biomass. By computational evaluation of these atomic models, we propose relationships between the crystal structure of cellulose Iβ and the nanoscale geometry of cellulose microfibrils.

The Effect of Water Molecules on Mechanical Properties of Bamboo Microfibrils

NASA Astrophysics Data System (ADS)

Rahbar, Nima

Bamboo fibers have higher strength-to-weight ratios than steel and concrete. The unique properties of bamboo fibers come from their natural composite structures that comprise mainly cellulose nanofibrils in a matrix of intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Here, we have utilized atomistic simulations to investigate the mechanical properties and mechanisms of interactions between these materials, in the presence of water molecules. Our results suggest that hemicellulose exhibits better mechanical properties and lignin shows greater tendency to adhere to cellulose nanofibrils. Consequently, the role of hemicellulose found to be enhancing the mechanical properties and lignin found to be providing the strength of bamboo fibers. The abundance of Hbonds in hemicellulose chains is responsible for improving the mechanical behavior of LCC. The strong van der Waals forces between lignin molecules and cellulose nanofibrils is responsible for higher adhesion energy between LCC/cellulose nanofibrils. We also found out that the amorphous regions of cellulose nanofibrils is the weakest interface in bamboo Microfibrils. In presence of water, the elastic modulus of lignin increases at low water content (less than 10 NSF CAREER Grant No. 1261284.

The effect of altered lignin composition on mechanical properties of CINNAMYL ALCOHOL DEHYDROGENASE (CAD) deficient poplars.

PubMed

Özparpucu, Merve; Gierlinger, Notburga; Burgert, Ingo; Van Acker, Rebecca; Vanholme, Ruben; Boerjan, Wout; Pilate, Gilles; Déjardin, Annabelle; Rüggeberg, Markus

2018-04-01

CAD-deficient poplars enabled studying the influence of altered lignin composition on mechanical properties. Severe alterations in lignin composition did not influence the mechanical properties. Wood represents a hierarchical fiber-composite material with excellent mechanical properties. Despite its wide use and versatility, its mechanical behavior has not been entirely understood. It has especially been challenging to unravel the mechanical function of the cell wall matrix. Lignin engineering has been a useful tool to increase the knowledge on the mechanical function of lignin as it allows for modifications of lignin content and composition and the subsequent studying of the mechanical properties of these transgenics. Hereby, in most cases, both lignin composition and content are altered and the specific influence of lignin composition has hardly been revealed. Here, we have performed a comprehensive micromechanical, structural, and spectroscopic analysis on xylem strips of transgenic poplar plants, which are downregulated for cinnamyl alcohol dehydrogenase (CAD) by a hairpin-RNA-mediated silencing approach. All parameters were evaluated on the same samples. Raman microscopy revealed that the lignin of the hpCAD poplars was significantly enriched in aldehydes and reduced in the (relative) amount of G-units. FTIR spectra indicated pronounced changes in lignin composition, whereas lignin content was not significantly changed between WT and the hpCAD poplars. Microfibril angles were in the range of 18°-24° and were not significantly different between WT and transgenics. No significant changes were observed in mechanical properties, such as tensile stiffness, ultimate stress, and yield stress. The specific findings on hpCAD poplar allowed studying the specific influence of lignin composition on mechanics. It can be concluded that the changes in lignin composition in hpCAD poplars did not affect the micromechanical tensile properties.

Unraveling cellulose microfibrils: a twisted tale

USDA-ARS?s Scientific Manuscript database

Molecular dynamics (MD) simulations of hydrated cellulose microfibrils are attractive to the textiles industry for their capacity to characterize water interactions with cotton fiber, as well as to the biofuels industry for their potential to provide insight toward efficient mechanisms for conversio...

Viscoelastic properties of microfibrillated cellulose (MFC) produced from agricultural residue corn stover

USDA-ARS?s Scientific Manuscript database

The rheological properties of microfibrillated cellulose (MFC) produced from agricultural residue corn stover were investigated. The corn stover MFC gels exhibited concentration-dependent viscoelastic properties. Higher corn stover MFC concentrations resulted in stronger viscoelastic properties. Th...

Viscoelastic properties of microfibrillated cellulose (MFC) produced from agricultural residue corn stover

USDA-ARS?s Scientific Manuscript database

The rheological properties of microfibrillated cellulose (MFC) produced from agricultural residue corn stover were investigated. The corn stover MFC gels exhibited concentration-dependent viscoelastic solid properties. Higher corn stover MFC concentrations resulted in stronger viscoelastic propertie...

Origin of chiral interactions in cellulose supra-molecular microfibrils.

PubMed

Khandelwal, Mudrika; Windle, Alan

2014-06-15

The formation of a chiral-nematic phase from cellulose nanowhiskers has been frequently reported in the literature. The most popular theory used to explain the chiral interactions is that of twisted morphology of cellulose nanowhiskers. Two possible origins of twist have been suggested: the intrinsic chirality of cellulose chains and result of interaction of chiral surfaces. High resolution SEM and AFM have been used to locate twists in cellulose microfibrils and nanowhiskers. The origin of the twisted morphology in cellulose microfibrils has been studied with reference to the protein aggregation theory. Copyright © 2014 Elsevier Ltd. All rights reserved.

Impaired cellulose synthase guidance leads to stem torsion and twists phyllotactic patterns in Arabidopsis.

PubMed

Landrein, Benoît; Lathe, Rahul; Bringmann, Martin; Vouillot, Cyril; Ivakov, Alexander; Boudaoud, Arezki; Persson, Staffan; Hamant, Olivier

2013-05-20

The parallel alignment of stiff cellulose microfibrils in plant-cell walls mediates anisotropic growth. This is largely controlled by cortical microtubules, which drive the insertion and trajectory of the cellulose synthase (CESA) complex at the plasma membrane. The CESA interactive protein 1 (CSI1) acts as a physical linker between CESA and cortical microtubules. Here we show that the inflorescence stems of csi1 mutants exhibit subtle right-handed torsion. Because cellulose deposition is largely uncoupled from cortical microtubules in csi1, we hypothesize that strictly transverse deposition of microfibrils in the wild-type is replaced by a helical orientation of uniform handedness in the mutant and that the helical microfibril alignment generates torsion. Interestingly, both elastic and viscous models for an expanding cell predict that a net helical orientation of microfibrils gives rise to a torque. We indeed observed tilted microfibrils in csi1 cells, and the torsion was almost absent in a csi1 prc1 background with impaired cellulose synthesis. In addition, the stem torsion led to a novel bimodal and robust phyllotactic pattern in the csi1 mutant, illustrating how growth perturbations can replace one robust mathematical pattern with a different, equally robust pattern. Copyright © 2013 Elsevier Ltd. All rights reserved.

Computational study of packing a collagen-like molecule: quasi-hexagonal vs "Smith" collagen microfibril model.

PubMed

Lee, J; Scheraga, H A; Rackovsky, S

1996-01-01

The lateral packing of a collagen-like molecule, CH3CO-(Gly-L-Pro-L-Pro)4-NHCH3, has been examined by energy minimization with the ECEPP/3 force field. Two current packing models, the Smith collagen microfibril twisted equilateral pentagonal model and the quasi-hexagonal packing model, have been extensively investigated. In treating the Smith microfibril model, energy minimization was carried out on various conformations including those with the symmetry of equivalent packing, i.e., in which the triple helices were arranged equivalently with respect to each other. Both models are based on the experimental observation of the characteristic axial periodicity, D = 67 nm, of light and dark bands, indicating that, if any superstructure exists, it should consist of five triple helices. The quasi-hexagonal packing structure is found to be energetically more favorable than the Smith microfibril model by as much as 31.2 kcal/mol of five triple helices. This is because the quasi-hexagonal packing geometry provides more nonbonded interaction possibilities between triple helices than does the Smith microfibril geometry. Our results are consistent with recent x-ray studies with synthetic collagen-like molecules and rat tail tendon, in which the data were interpreted as being consistent with either a quasi-hexagonal or a square-triangular structure.

COBRA, an Arabidopsis Extracellular Glycosyl-Phosphatidyl Inositol-Anchored Protein, Specifically Controls Highly Anisotropic Expansion through Its Involvement in Cellulose Microfibril OrientationW⃞

PubMed Central

Roudier, François; Fernandez, Anita G.; Fujita, Miki; Himmelspach, Regina; Borner, Georg H.H.; Schindelman, Gary; Song, Shuang; Baskin, Tobias I.; Dupree, Paul; Wasteneys, Geoffrey O.; Benfey, Philip N.

2005-01-01

The orientation of cell expansion is a process at the heart of plant morphogenesis. Cellulose microfibrils are the primary anisotropic material in the cell wall and thus are likely to be the main determinant of the orientation of cell expansion. COBRA (COB) has been identified previously as a potential regulator of cellulose biogenesis. In this study, characterization of a null allele, cob-4, establishes the key role of COB in controlling anisotropic expansion in most developing organs. Quantitative polarized-light and field-emission scanning electron microscopy reveal that loss of anisotropic expansion in cob mutants is accompanied by disorganization of the orientation of cellulose microfibrils and subsequent reduction of crystalline cellulose. Analyses of the conditional cob-1 allele suggested that COB is primarily implicated in microfibril deposition during rapid elongation. Immunodetection analysis in elongating root cells revealed that, in agreement with its substitution by a glycosylphosphatidylinositol anchor, COB was polarly targeted to both the plasma membrane and the longitudinal cell walls and was distributed in a banding pattern perpendicular to the longitudinal axis via a microtubule-dependent mechanism. Our observations suggest that COB, through its involvement in cellulose microfibril orientation, is an essential factor in highly anisotropic expansion during plant morphogenesis. PMID:15849274

COBRA, an Arabidopsis extracellular glycosyl-phosphatidyl inositol-anchored protein, specifically controls highly anisotropic expansion through its involvement in cellulose microfibril orientation.

PubMed

Roudier, François; Fernandez, Anita G; Fujita, Miki; Himmelspach, Regina; Borner, Georg H H; Schindelman, Gary; Song, Shuang; Baskin, Tobias I; Dupree, Paul; Wasteneys, Geoffrey O; Benfey, Philip N

2005-06-01

The orientation of cell expansion is a process at the heart of plant morphogenesis. Cellulose microfibrils are the primary anisotropic material in the cell wall and thus are likely to be the main determinant of the orientation of cell expansion. COBRA (COB) has been identified previously as a potential regulator of cellulose biogenesis. In this study, characterization of a null allele, cob-4, establishes the key role of COB in controlling anisotropic expansion in most developing organs. Quantitative polarized-light and field-emission scanning electron microscopy reveal that loss of anisotropic expansion in cob mutants is accompanied by disorganization of the orientation of cellulose microfibrils and subsequent reduction of crystalline cellulose. Analyses of the conditional cob-1 allele suggested that COB is primarily implicated in microfibril deposition during rapid elongation. Immunodetection analysis in elongating root cells revealed that, in agreement with its substitution by a glycosylphosphatidylinositol anchor, COB was polarly targeted to both the plasma membrane and the longitudinal cell walls and was distributed in a banding pattern perpendicular to the longitudinal axis via a microtubule-dependent mechanism. Our observations suggest that COB, through its involvement in cellulose microfibril orientation, is an essential factor in highly anisotropic expansion during plant morphogenesis.

Ultrastructural organization of connective tissue microfibrils in the posterior chamber of the eye in vivo and in vitro.

PubMed

Inoue, S

1995-02-01

The ultrastructural organization of connective tissue microfibrils was studied in the mouse eye and also by means of in vitro experiments for reconstituting microfibrils. In the posterior chamber of the eye of the C57BL/6J mouse, 3 nm-wide ribbon-like double-tracked structures were present and were periodically associated on either side with 3.5 nm-wide particulate structures identified as pentosomes, the subunits of amyloid P component (AP). At certain sites, such composite structures were observed in various stages of helical winding, and in these helices, pentosomes were preferentially localized internally. In helices in the final stages of winding, the resulting rods appeared increasingly similar to those of microfibrils. In experiments in vitro, incubation of chondroitin sulfate proteoglycan (CSPG) in TRIS buffer, pH 7.4, at 35 degrees C for 1 h produced random aggregates of 3 nm-wide double-tracked structures similar to those observed in the eye. Co-incubation of CSPG and AP resulted in the formation of rod-like structures arranged parallel to one another in approximately 50 nm-thick sheet-like layers. These rods were ultrastructurally similar to microfibrils and were made up of helically wound, 3 nm-wide double-tracked structures containing pentosomes within their core. The results of in vivo as well as in vitro experiments suggest the possibility that the connective tissue microfibril is composed of helically wound, CSPG-containing, 3 nm-wide double-tracked structures periodically associated with pentosomes which, as the helix becomes progressively tighter, fit with one another at the core of the helix to form successive 8.5 nm-wide disks of AP segments.

Arabinan-cellulose composite in Opuntia ficus-indica prickly pear spines.

PubMed

Vignon, M R; Heux, L; Malainine, M-E; Mahrouz, M

2004-01-02

The ultrastructure of the spines decorating the cladodes of the cactus Opuntia ficus-indica was investigated by optical microscopy, scanning and transmission electron microscopy, wide angle X-ray, and solid state 13C NMR analyses. Each spine consisted of a compact parallel arrangement of slender cellulosic fibers (0.4 mm in length and 6-10 microm in diameter) with small lumens. The fibers were disencrusted by alkali and sodium chlorite bleaching, yielding a remarkable arabinan-cellulose (1:1) product. X-ray fiber diagrams of the spines before and after purification confirmed the presence of crystalline cellulose domains with molecular axis parallel to the spine axis. CP-MAS 13C T1 NMR data showed a strong interaction at a nanometric level of a fraction of the arabinan and the cellulose crystalline domains. By sequential hydrothermal extractions, followed by a trifluoroacetic acid treatment, a relatively pure cellulose was isolated while the extracted fibers became fibrillated into slender microfibrils having no more than 4-6 nm diameter. The hydrothermal extract yielded the alpha-L-arabinofuranan consisting of a chain of (1-->5)-linked L-arabinosyl residues with branching either at C-2 or C-3 or at both C-2 and C-3. Taken together, these observations suggest that the bulk of the spine fibers consists of an intimate composite of cellulose microfibrils embedded in an arabinan matrix.

The jiaoyao1 Mutant Is an Allele of korrigan1 That Abolishes Endoglucanase Activity and Affects the Organization of Both Cellulose Microfibrils and Microtubules in Arabidopsis[C][W

PubMed Central

Lei, Lei; Zhang, Tian; Strasser, Richard; Lee, Christopher M.; Gonneau, Martine; Mach, Lukas; Vernhettes, Samantha; Kim, Seong H.; J. Cosgrove, Daniel; Li, Shundai; Gu, Ying

2014-01-01

In higher plants, cellulose is synthesized by plasma membrane–localized cellulose synthase complexes (CSCs). Arabidopsis thaliana GH9A1/KORRIGAN1 is a membrane-bound, family 9 glycosyl hydrolase that is important for cellulose synthesis in both primary and secondary cell walls. Most previously identified korrigan1 mutants show severe phenotypes such as embryo lethality; therefore, the role of GH9A1 in cellulose synthesis remains unclear. Here, we report a novel A577V missense mutation, designated jiaoyao1 (jia1), in the second of the glycosyl hydrolase family 9 active site signature motifs in GH9A1. jia1 is defective in cell expansion in dark-grown hypocotyls, roots, and adult plants. Consistent with its defect in cell expansion, this mutation in GH9A1 resulted in reduced cellulose content and reduced CSC velocity at the plasma membrane. Green fluorescent protein–GH9A1 is associated with CSCs at multiple locations, including the plasma membrane, Golgi, trans-Golgi network, and small CESA-containing compartments or microtubule-associated cellulose synthase compartments, indicating a tight association between GH9A1 and CSCs. GH9A1A577V abolishes the endoglucanase activity of GH9A1 in vitro but does not affect its interaction with CESAs in vitro, suggesting that endoglucanase activity is important for cellulose synthesis. Interestingly, jia1 results in both cellulose microfibril and microtubule disorganization. Our study establishes the important role of endoglucanase in cellulose synthesis and cellulose microfibril organization in plants. PMID:24963054

The jiaoyao1 Mutant Is an Allele of korrigan1 That Abolishes Endoglucanase Activity and Affects the Organization of Both Cellulose Microfibrils and Microtubules in Arabidopsis.

PubMed

Lei, Lei; Zhang, Tian; Strasser, Richard; Lee, Christopher M; Gonneau, Martine; Mach, Lukas; Vernhettes, Samantha; Kim, Seong H; J Cosgrove, Daniel; Li, Shundai; Gu, Ying

2014-06-01

In higher plants, cellulose is synthesized by plasma membrane-localized cellulose synthase complexes (CSCs). Arabidopsis thaliana GH9A1/KORRIGAN1 is a membrane-bound, family 9 glycosyl hydrolase that is important for cellulose synthesis in both primary and secondary cell walls. Most previously identified korrigan1 mutants show severe phenotypes such as embryo lethality; therefore, the role of GH9A1 in cellulose synthesis remains unclear. Here, we report a novel A577V missense mutation, designated jiaoyao1 (jia1), in the second of the glycosyl hydrolase family 9 active site signature motifs in GH9A1. jia1 is defective in cell expansion in dark-grown hypocotyls, roots, and adult plants. Consistent with its defect in cell expansion, this mutation in GH9A1 resulted in reduced cellulose content and reduced CSC velocity at the plasma membrane. Green fluorescent protein-GH9A1 is associated with CSCs at multiple locations, including the plasma membrane, Golgi, trans-Golgi network, and small CESA-containing compartments or microtubule-associated cellulose synthase compartments, indicating a tight association between GH9A1 and CSCs. GH9A1 A577V abolishes the endoglucanase activity of GH9A1 in vitro but does not affect its interaction with CESAs in vitro, suggesting that endoglucanase activity is important for cellulose synthesis. Interestingly, jia1 results in both cellulose microfibril and microtubule disorganization. Our study establishes the important role of endoglucanase in cellulose synthesis and cellulose microfibril organization in plants. © 2014 American Society of Plant Biologists. All rights reserved.

Dissecting the molecular mechanism underlying the intimate relationship between cellulose microfibrils and cortical microtubules.

PubMed

Lei, Lei; Li, Shundai; Bashline, Logan; Gu, Ying

2014-01-01

A central question in plant cell development is how the cell wall determines directional cell expansion and therefore the final shape of the cell. As the major load-bearing component of the cell wall, cellulose microfibrils are laid down transversely to the axis of elongation, thus forming a spring-like structure that reinforces the cell laterally and while favoring longitudinal expansion in most growing cells. Mounting evidence suggests that cortical microtubules organize the deposition of cellulose microfibrils, but the precise molecular mechanisms linking microtubules to cellulose organization have remained unclear until the recent discovery of cellulose synthase interactive protein 1 , a linker protein between the cortical microtubules and the cellulose biosynthesizing machinery. In this review, we will focus on the intimate relationship between cellulose microfibrils and cortical microtubules, in particular, we will discuss microtubule arrangement and cell wall architecture, the linkage between cellulose synthase complexes and microtubules, and the feedback mechanisms between cell wall and microtubules.

Cytoskeleton-mediated templating of complex cellulose-scaffolded extracellular structure and its association with oikosins in the urochordate Oikopleura.

PubMed

Sagane, Yoshimasa; Hosp, Julia; Zech, Karin; Thompson, Eric M

2011-05-01

Oriented cellulose deposition is critical to plant patterning and models suggest microtubules constrain cellulose synthase movements through the plasma membrane. Though widespread in plants, urochordates are the only animals that synthesize cellulose. We characterized the distinctive cellulose microfibril scaffold of the larvacean house and its interaction with house structural proteins (oikosins). Targeted disruption of cytoskeletal elements, secretory pathways, and plasma membrane organization, suggested a working model for templating extracellular cellulose microfibrils from animal cells that shows both convergence and differences to plant models. Specialized cortical F-actin arrays template microfibril orientation and glycosylphosphatidylinositol-anchored proteins in lipid rafts may act as scaffolding proteins in microfibril elongation. Microtubules deliver and maintain cellulose synthase complexes to specific cell membrane sites rather than orienting their movement through the membrane. Oikosins are incorporated into house compartments directly above their corresponding cellular field of expression and interact with the cellulose scaffold to a variable extent.

Alteration of in vivo cellulose ribbon assembly by carboxymethylcellulose and other cellulose derivatives.

PubMed

Haigler, C H; White, A R; Brown, R M; Cooper, K M

1982-07-01

In vivo cellulose ribbon assembly by the Gram-negative bacterium Acetobacter xylinum can be altered by incubation in carboxymethylcellulose (CMC), a negatively charged water-soluble cellulose derivative, and also by incubation in a variety of neutral, water-soluble cellulose derivatives. In the presence of all of these substituted celluloses, normal fasciation of microfibril bundles to form the typical twisting ribbon is prevented. Alteration of ribbon assembly is most extensive in the presence of CMC, which often induces synthesis of separate, intertwining bundles of microfibrils. Freeze-etch preparations of the bacterial outer membrane suggest that particles that are thought to be associated with cellulose synthesis or extrusion may be specifically organized to mediate synthesis of microfibril bundles. These data support the previous hypothesis that the cellulose ribbon of A. xylinum is formed by a hierarchical, cell-directed, self-assembly process. The relationship of these results to the regulation of cellulose microfibril size and wall extensibility in plant cell walls is discussed.

Structural and biochemical changes in dermis of sea cucumber (Stichopus japonicus) during autolysis in response to cutting the body wall.

PubMed

Liu, Yu-Xin; Zhou, Da-Yong; Liu, Zi-Qiang; Lu, Ting; Song, Liang; Li, Dong-Mei; Dong, Xiu-Ping; Qi, Hang; Zhu, Bei-Wei; Shahidi, Fereidoon

2018-02-01

The autolysis of sea cucumber body wall is caused by endogenous proteolysis of its structural elements. However, changes in collagen fibrils, collagen fibres and microfibrils, the major structural elements in sea cucumber body wall during autolysis are less clear. Autolysis of sea cucumber (S. japonicus) was induced by cutting the body wall, and the structural and biochemical changes in its dermis were investigated using electron microscopy, differential scanning calorimetry, infrared spectroscopy, electrophoresis, and chemical analysis. During autolysis, both collagen fibres and microfibrils gradually degraded. In contrast, damage to microfibrils was more pronounced. Upon massive autolysis, collagen fibres disaggregated into collagen fibril bundles and individual fibrils due to the fracture of interfibrillar bridges. Meanwhile, excessive unfolding of collagen fibrils occurred. However, there was only slight damage to collagen monomers. Therefore, structural damage in collagen fibres, collagen fibrils and microfibrils rather than monomeric collagen accounts for autolysis of S. japonicus dermis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Super Water-Repellent Fractal Surfaces of a Photochromic Diarylethene Induced by UV Light

NASA Astrophysics Data System (ADS)

Izumi, Norikazu; Minami, Takayuki; Mayama, Hiroyuki; Takata, Atsushi; Nakamura, Shinichiro; Yokojima, Satoshi; Tsujii, Kaoru; Uchida, Kingo

2008-09-01

Photochromic diarylethene forms super water-repellent surfaces upon irradiation with UV light. Microfibril-like crystals grow on the solid diarylethene surface after UV irradiation, and the contact angle of water on the surface becomes larger with increasing surface roughness with time. The fractal analysis was made by the box-counting method for the rough surfaces. There are three regions in the roughness size having the fractal dimension of ca. 2.4 (size of roughness smaller than 5 µm), of ca. 2.2 (size of roughness between 5-40 µm), and of ca. 2.0 (size of roughness larger than 40 µm). The fractal dimension of ca. 2.4 was due to the fibril-like structures generated gradually by UV irradiation on diarylethene surfaces accompanied with an increase in the contact angle. The surface structure with larger fractal dimension mainly contributes to realizing the super water-repellency of the diarylethene surfaces. This mechanism of spontaneous formation of fractal surfaces is similar to that for triglyceride and alkylketene dimer waxes.

Monitoring Meso-Scale Ordering of Cellulose in Intact Plant Cell Walls Using Sum Frequency Generation Spectroscopy1[C][W][OPEN

PubMed Central

Park, Yong Bum; Lee, Christopher M.; Koo, Bon-Wook; Park, Sunkyu; Cosgrove, Daniel J.; Kim, Seong H.

2013-01-01

Sum frequency generation (SFG) vibration spectroscopy can selectively detect crystalline cellulose without spectral interference from cell wall matrix components. Here, we show that the cellulose SFG spectrum is sensitive to cellulose microfibril alignment and packing within the cell wall. SFG intensity at 2,944 cm−1 correlated well with crystalline cellulose contents of various regions of the Arabidopsis (Arabidopsis thaliana) inflorescence, while changes in the 3,320/2,944 cm−1 intensity ratio suggest subtle changes in cellulose ordering as tissues mature. SFG analysis of two cellulose synthase mutants (irx1/cesa8 and irx3/cesa7) indicates a reduction in cellulose content without evidence of altered cellulose structure. In primary cell walls of Arabidopsis, cellulose exhibited a characteristic SFG peak at 2,920 and 3,320 cm−1, whereas in secondary cell walls, it had peaks at 2,944 and 3,320 cm−1. Starch (amylose) gave an SFG peak at 2,904 cm−1 (CH methine) whose intensity increased with light exposure prior to harvest. Selective removal of matrix polysaccharides from primary cell walls by acid hydrolysis resulted in an SFG spectrum resembling that of secondary wall cellulose. Our results show that SFG spectroscopy is sensitive to the ordering of cellulose microfibrils in plant cell walls at the meso scale (nm to μm) that is important for cell wall architecture but cannot be probed by other spectroscopic or diffraction techniques. PMID:23995148

Monitoring meso-scale ordering of cellulose in intact plant cell walls using sum frequency generation spectroscopy.

PubMed

Park, Yong Bum; Lee, Christopher M; Koo, Bon-Wook; Park, Sunkyu; Cosgrove, Daniel J; Kim, Seong H

2013-10-01

Sum frequency generation (SFG) vibration spectroscopy can selectively detect crystalline cellulose without spectral interference from cell wall matrix components. Here, we show that the cellulose SFG spectrum is sensitive to cellulose microfibril alignment and packing within the cell wall. SFG intensity at 2,944 cm(-1) correlated well with crystalline cellulose contents of various regions of the Arabidopsis (Arabidopsis thaliana) inflorescence, while changes in the 3,320/2,944 cm(-1) intensity ratio suggest subtle changes in cellulose ordering as tissues mature. SFG analysis of two cellulose synthase mutants (irx1/cesa8 and irx3/cesa7) indicates a reduction in cellulose content without evidence of altered cellulose structure. In primary cell walls of Arabidopsis, cellulose exhibited a characteristic SFG peak at 2,920 and 3,320 cm(-1), whereas in secondary cell walls, it had peaks at 2,944 and 3,320 cm(-1). Starch (amylose) gave an SFG peak at 2,904 cm(-1) (CH methine) whose intensity increased with light exposure prior to harvest. Selective removal of matrix polysaccharides from primary cell walls by acid hydrolysis resulted in an SFG spectrum resembling that of secondary wall cellulose. Our results show that SFG spectroscopy is sensitive to the ordering of cellulose microfibrils in plant cell walls at the meso scale (nm to μm) that is important for cell wall architecture but cannot be probed by other spectroscopic or diffraction techniques.

The Evolutionary Fate of Phenotypic Plasticity and Functional Traits under Domestication in Manioc: Changes in Stem Biomechanics and the Appearance of Stem Brittleness

PubMed Central

Ménard, Léa; McKey, Doyle; Mühlen, Gilda S.; Clair, Bruno; Rowe, Nick P.

2013-01-01

Domestication can influence many functional traits in plants, from overall life-history and growth form to wood density and cell wall ultrastructure. Such changes can increase fitness of the domesticate in agricultural environments but may negatively affect survival in the wild. We studied effects of domestication on stem biomechanics in manioc by comparing domesticated and ancestral wild taxa from two different regions of greater Amazonia. We compared mechanical properties, tissue organisation and wood characteristics including microfibril angles in both wild and domesticated plants, each growing in two different habitats (forest or savannah) and varying in growth form (shrub or liana). Wild taxa grew as shrubs in open savannah but as lianas in overgrown and forested habitats. Growth form plasticity was retained in domesticated manioc. However, stems of the domesticate showed brittle failure. Wild plants differed in mechanical architecture between shrub and liana phenotypes, a difference that diminished between shrubs and lianas of the domesticate. Stems of wild plants were generally stiffer, failed at higher bending stresses and were less prone to brittle fracture compared with shrub and liana phenotypes of the domesticate. Biomechanical differences between stems of wild and domesticated plants were mainly due to changes in wood density and cellulose microfibril angle rather than changes in secondary growth or tissue geometry. Domestication did not significantly modify “large-scale” trait development or growth form plasticity, since both wild and domesticated manioc can develop as shrubs or lianas. However, “finer-scale” developmental traits crucial to mechanical stability and thus ecological success of the plant were significantly modified. This profoundly influenced the likelihood of brittle failure, particularly in long climbing stems, thereby also influencing the survival of the domesticate in natural situations vulnerable to mechanical perturbation. We discuss the different selective pressures that could explain evolutionary modifications of stem biomechanical properties under domestication in manioc. PMID:24023960

Cambial injury in lodgepole pine (Pinus contorta): mountain pine beetle vs fire.

PubMed

Arbellay, Estelle; Daniels, Lori D; Mansfield, Shawn D; Chang, Alice S

2017-12-01

Both mountain pine beetle (MPB) Dendroctonus ponderosae Hopkins and fire leave scars with similar appearance on lodgepole pine Pinus contorta Dougl. ex Loud. var. latifolia Engelm. that have never been compared microscopically, despite the pressing need to determine the respective effects of MPB and fire injury on tree physiology. We analysed changes in wood formation in naturally caused scars on lodgepole pine, and tested the hypotheses that (i) MPB and fire injury elicit distinct anomalies in lodgepole pine wood and (ii) anomalies differ in magnitude and/or duration between MPB and fire. Mountain pine beetle and fire injury reduced radial growth in the first year post-injury. Otherwise, radial growth and wood density increased over more than 10 years in both MPB and fire scars. We found that the general increase in radial growth was of greater magnitude (up to 27%) and of longer duration (up to 5 years) in fire scars compared with MPB scars, as shown in earlywood width. We also observed that the increase in latewood density was of greater magnitude (by 12%) in MPB scars, but of longer duration (by 4 years) in fire scars. Crystallinity decreased following MPB and fire injury, while microfibril angle increased. These changes in fibre traits were of longer duration (up to 4 years) in MPB scars compared with fire scars, as shown in microfibril angle. We found no significant changes in carbon and nitrogen concentrations. In conclusion, we stress that reduced competition and resistance to cavitation play an important role alongside cambial injury in influencing the type and severity of changes. In addition, more research is needed to validate the thresholds introduced in this study. Our findings serve as a foundation for new protocols to distinguish between bark beetle and fire disturbance, which is essential for improving our knowledge of historical bark beetle and fire regimes, and their interactions. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A novel wood flour-filled composite based on microfibrillar high-density polyethylene (HDPE)/Nylon-6 blends.

PubMed

Liu, Hongzhi; Yao, Fei; Xu, Yanjun; Wu, Qinglin

2010-05-01

A novel wood flour (WF)-filled composite based on the microfibrillar high-density polyethylene (HDPE) and Nylon-6 co-blend, in which both in situ formed Nylon-6 microfibrils and WF acted as reinforcing elements, was successfully developed using a two-step extrusion method. At the 30wt.% WF loading level, WF-filled composite based on the microfibrillized HDPE/Nylon-6 blend exhibited higher strengths and moduli than the corresponding HDPE-based composite. The incorporation of WF reduced short-term creep response of HDPE matrix and the presence of Nylon-6 microfibrils further contributed to the creep reduction. Copyright 2009 Elsevier Ltd. All rights reserved.

Cellulose Structural Polymorphism in Plant Primary Cell Walls Investigated by High-Field 2D Solid-State NMR Spectroscopy and Density Functional Theory Calculations.

PubMed

Wang, Tuo; Yang, Hui; Kubicki, James D; Hong, Mei

2016-06-13

The native cellulose of bacterial, algal, and animal origins has been well studied structurally using X-ray and neutron diffraction and solid-state NMR spectroscopy, and is known to consist of varying proportions of two allomorphs, Iα and Iβ, which differ in hydrogen bonding, chain packing, and local conformation. In comparison, cellulose structure in plant primary cell walls is much less understood because plant cellulose has lower crystallinity and extensive interactions with matrix polysaccharides. Here we have combined two-dimensional magic-angle-spinning (MAS) solid-state nuclear magnetic resonance (solid-state NMR) spectroscopy at high magnetic fields with density functional theory (DFT) calculations to obtain detailed information about the structural polymorphism and spatial distributions of plant primary-wall cellulose. 2D (13)C-(13)C correlation spectra of uniformly (13)C-labeled cell walls of several model plants resolved seven sets of cellulose chemical shifts. Among these, five sets (denoted a-e) belong to cellulose in the interior of the microfibril while two sets (f and g) can be assigned to surface cellulose. Importantly, most of the interior cellulose (13)C chemical shifts differ significantly from the (13)C chemical shifts of the Iα and Iβ allomorphs, indicating that plant primary-wall cellulose has different conformations, packing, and hydrogen bonding from celluloses of other organisms. 2D (13)C-(13)C correlation experiments with long mixing times and with water polarization transfer revealed the spatial distributions and matrix-polysaccharide interactions of these cellulose structures. Celluloses f and g are well mixed chains on the microfibril surface, celluloses a and b are interior chains that are in molecular contact with the surface chains, while cellulose c resides in the core of the microfibril, outside spin diffusion contact with the surface. Interestingly, cellulose d, whose chemical shifts differ most significantly from those of bacterial, algal, and animal cellulose, interacts with hemicellulose, is poorly hydrated, and is targeted by the protein expansin during wall loosening. To obtain information about the C6 hydroxymethyl conformation of these plant celluloses, we carried out DFT calculations of (13)C chemical shifts, using the Iα and Iβ crystal structures as templates and varying the C5-C6 torsion angle. Comparison with the experimental chemical shifts suggests that all interior cellulose favor the tg conformation, but cellulose d also has a similar propensity to adopt the gt conformation. These results indicate that cellulose in plant primary cell walls, due to their interactions with matrix polysaccharides, and has polymorphic structures that are not a simple superposition of the Iα and Iβ allomorphs, thus distinguishing them from bacterial and animal celluloses.

Cellulose Structural Polymorphism in Plant Primary Cell Walls Investigated by High-Field 2D Solid-State NMR Spectroscopy and Density Functional Theory Calculations

PubMed Central

Wang, Tuo; Yang, Hui; Kubicki, James D.; Hong, Mei

2017-01-01

The native cellulose of bacterial, algal, and animal origins has been well studied structurally using X-ray and neutron diffraction and solid-state NMR spectroscopy, and is known to consist of varying proportions of two allomorphs, Iα and Iβ, which differ in hydrogen bonding, chain packing, and local conformation. In comparison, cellulose structure in plant primary cell walls is much less understood because plant cellulose has lower crystallinity and extensive interactions with matrix polysaccharides. Here we have combined two-dimensional magic-angle-spinning (MAS) solid-state nuclear magnetic resonance (solid-state NMR) spectroscopy at high magnetic fields with density functional theory (DFT) calculations to obtain detailed information about the structural polymorphism and spatial distributions of plant primary-wall cellulose. 2D 13C-13C correlation spectra of uniformly 13C-labeled cell walls of several model plants resolved seven sets of cellulose chemical shifts. Among these, five sets (denoted a-e) belong to cellulose in the interior of the microfibril while two sets (f and g) can be assigned to surface cellulose. Importantly, most of the interior cellulose 13C chemical shifts differ significantly from the 13C chemical shifts of the Iα and Iβ allomorphs, indicating that plant primary-wall cellulose has different conformations, packing and hydrogen bonding from celluloses of other organisms. 2D 13C-13C correlation experiments with long mixing times and with water polarization transfer revealed the spatial distributions and matrix-polysaccharide interactions of these cellulose structures. Cellulose f and g are well mixed chains on the microfibril surface, cellulose a and b are interior chains that are in molecular contact with the surface chains, while cellulose c resides in the core of the microfibril, outside spin diffusion contact with the surface. Interestingly, cellulose d, whose chemical shifts differ most significantly from those of bacterial, algal and animal cellulose, interacts with hemicellulose, is poorly hydrated, and is targeted by the protein expansin during wall loosening. To obtain information about the C6 hydroxymethyl conformation of these plant celluloses, we carried out DFT calculations of 13C chemical shifts, using the Iα and Iβ crystal structures as templates and varying the C5-C6 torsion angle. Comparison with the experimental chemical shifts suggests that all interior cellulose favor the tg conformation, but cellulose d also has a similar propensity to adopt the gt conformation. These results indicate that cellulose in plant primary cell walls, due to their interactions with matrix polysaccharides, has polymorphic structures that are not a simple superposition of the Iα and Iβ allomorphs, thus distinguishing them from bacterial and animal celluloses. PMID:27192562

Structure of the Fibrillin-1 N-Terminal Domains Suggests that Heparan Sulfate Regulates the Early Stages of Microfibril Assembly

PubMed Central

Yadin, David A.; Robertson, Ian B.; McNaught-Davis, Joanne; Evans, Paul; Stoddart, David; Handford, Penny A.; Jensen, Sacha A.; Redfield, Christina

2013-01-01

Summary The human extracellular matrix glycoprotein fibrillin-1 is the primary component of the 10- to 12-nm-diameter microfibrils, which perform key structural and regulatory roles in connective tissues. Relatively little is known about the molecular mechanisms of fibrillin assembly into microfibrils. Studies using recombinant fibrillin fragments indicate that an interaction between the N- and C-terminal regions drives head-to-tail assembly. Here, we present the structure of a fibrillin N-terminal fragment comprising the fibrillin unique N-terminal (FUN) and the first three epidermal growth factor (EGF)-like domains (FUN-EGF3). Two rod-like domain pairs are separated by a short, flexible linker between the EGF1 and EGF2 domains. We also show that the binding site for the C-terminal region spans multiple domains and overlaps with a heparin interaction site. These data suggest that heparan sulfate may sequester fibrillin at the cell surface via FUN-EGF3 prior to aggregation of the C terminus, thereby regulating microfibril assembly. PMID:24035709

Cellulose Microfibril Formation by Surface-Tethered Cellulose Synthase Enzymes.

PubMed

Basu, Snehasish; Omadjela, Okako; Gaddes, David; Tadigadapa, Srinivas; Zimmer, Jochen; Catchmark, Jeffrey M

2016-02-23

Cellulose microfibrils are pseudocrystalline arrays of cellulose chains that are synthesized by cellulose synthases. The enzymes are organized into large membrane-embedded complexes in which each enzyme likely synthesizes and secretes a β-(1→4) glucan. The relationship between the organization of the enzymes in these complexes and cellulose crystallization has not been explored. To better understand this relationship, we used atomic force microscopy to visualize cellulose microfibril formation from nickel-film-immobilized bacterial cellulose synthase enzymes (BcsA-Bs), which in standard solution only form amorphous cellulose from monomeric BcsA-B complexes. Fourier transform infrared spectroscopy and X-ray diffraction techniques show that surface-tethered BcsA-Bs synthesize highly crystalline cellulose II in the presence of UDP-Glc, the allosteric activator cyclic-di-GMP, as well as magnesium. The cellulose II cross section/diameter and the crystal size and crystallinity depend on the surface density of tethered enzymes as well as the overall concentration of substrates. Our results provide the correlation between cellulose microfibril formation and the spatial organization of cellulose synthases.

Wood formation in Angiosperms.

PubMed

Déjardin, Annabelle; Laurans, Françoise; Arnaud, Dominique; Breton, Christian; Pilate, Gilles; Leplé, Jean-Charles

2010-04-01

Wood formation is a complex biological process, involving five major developmental steps, including (1) cell division from a secondary meristem called the vascular cambium, (2) cell expansion (cell elongation and radial enlargement), (3) secondary cell wall deposition, (4) programmed cell death, and (5) heartwood formation. Thanks to the development of genomic studies in woody species, as well as genetic engineering, recent progress has been made in the understanding of the molecular mechanisms underlying wood formation. In this review, we will focus on two different aspects, the lignification process and the control of microfibril angle in the cell wall of wood fibres, as they are both key features of wood material properties. Copyright (c) 2010 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Functional Specialization of Cellulose Synthase Isoforms in a Moss Shows Parallels with Seed Plants1[OPEN

PubMed Central

Li, Xingxing; Huang, Shixin; Van de Meene, Allison M.L.; Tran, Mai L.; Killeavy, Erin; Mercure, Danielle; Burton, Rachel A.

2017-01-01

The secondary cell walls of tracheary elements and fibers are rich in cellulose microfibrils that are helically oriented and laterally aggregated. Support cells within the leaf midribs of mosses deposit cellulose-rich secondary cell walls, but their biosynthesis and microfibril organization have not been examined. Although the Cellulose Synthase (CESA) gene families of mosses and seed plants diversified independently, CESA knockout analysis in the moss Physcomitrella patens revealed parallels with Arabidopsis (Arabidopsis thaliana) in CESA functional specialization, with roles for both subfunctionalization and neofunctionalization. The similarities include regulatory uncoupling of the CESAs that synthesize primary and secondary cell walls, a requirement for two or more functionally distinct CESA isoforms for secondary cell wall synthesis, interchangeability of some primary and secondary CESAs, and some CESA redundancy. The cellulose-deficient midribs of ppcesa3/8 knockouts provided negative controls for the structural characterization of stereid secondary cell walls in wild type P. patens. Sum frequency generation spectra collected from midribs were consistent with cellulose microfibril aggregation, and polarization microscopy revealed helical microfibril orientation only in wild type leaves. Thus, stereid secondary walls are structurally distinct from primary cell walls, and they share structural characteristics with the secondary walls of tracheary elements and fibers. We propose a mechanism for the convergent evolution of secondary walls in which the deposition of aggregated and helically oriented microfibrils is coupled to rapid and highly localized cellulose synthesis enabled by regulatory uncoupling from primary wall synthesis. PMID:28768816

Atomic force microscopy of torus-bearing pit membranes

Treesearch

Roland R. Dute; Thomas Elder

2011-01-01

Atomic force microscopy was used to compare the structures of dried, torus-bearing pit membranes from four woody species, three angiosperms and one gymnosperm. Tori of Osmanthus armatus are bipartite consisting of a pustular zone overlying parallel sets of microfibrils that form a peripheral corona. Microfibrils of the corona form radial spokes as they traverse the...

Atomic force microscopy based nanoindentation study of onion abaxial epidermis walls in aqueous environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xi, Xiaoning; Tittmann, Bernhard; Kim, Seong H.

An atomic force microscopy based nanoindentation method was employed to study how the structure of cellulose microfibril packing and matrix polymers affect elastic modulus of fully hydrated primary plant cell walls. The isolated, single-layered abaxial epidermis cell wall of an onion bulb was used as a test system since the cellulose microfibril packing in this cell wall is known to vary systematically from inside to outside scales and the most abundant matrix polymer, pectin, can easily be altered through simple chemical treatments such as ethylenediaminetetraacetic acid and calcium ions. Experimental results showed that the pectin network variation has significant impactsmore » on the cell wall modulus, and not the cellulose microfibril packing.« less

Re-constructing our models of cellulose and primary cell wall assembly

PubMed Central

Cosgrove, Daniel J.

2014-01-01

The cellulose microfibril has more subtlety than is commonly recognized. Details of its structure may influence how matrix polysaccharides interact with its distinctive hydrophobic and hydrophilic surfaces to form a strong yet extensible structure. Recent advances in this field include the first structures of bacterial and plant cellulose synthases and revised estimates of microfibril structure, reduced from 36 to 18 chains. New results also indicate that cellulose interactions with xyloglucan are more limited than commonly believed, whereas pectin-cellulose interactions are more prevalent. Computational results indicate that xyloglucan binds tightest to the hydrophobic surface of cellulose microfibrils. Wall extensibility may be controlled at limited regions (“biomechanical hotspots”) where cellulose-cellulose contacts are made, potentially mediated by trace amounts of xyloglucan. PMID:25460077

Re-constructing our models of cellulose and primary cell wall assembly.

PubMed

Cosgrove, Daniel J

2014-12-01

The cellulose microfibril has more subtlety than is commonly recognized. Details of its structure may influence how matrix polysaccharides interact with its distinctive hydrophobic and hydrophilic surfaces to form a strong yet extensible structure. Recent advances in this field include the first structures of bacterial and plant cellulose synthases and revised estimates of microfibril structure, reduced from 36 to 18 chains. New results also indicate that cellulose interactions with xyloglucan are more limited than commonly believed, whereas pectin–cellulose interactions are more prevalent. Computational results indicate that xyloglucan binds tightest to the hydrophobic surface of cellulose microfibrils. Wall extensibility may be controlled at limited regions (‘biomechanical hotspots’) where cellulose–cellulose contacts are made, potentially mediated by trace amounts of xyloglucan.

Unique Aspects of the Structure and Dynamics of Elementary Iβ Cellulose Microfibrils Revealed by Computational Simulations1[OPEN

PubMed Central

Oehme, Daniel P.; Downton, Matthew T.; Doblin, Monika S.; Wagner, John; Gidley, Michael J.; Bacic, Antony

2015-01-01

The question of how many chains an elementary cellulose microfibril contains is critical to understanding the molecular mechanism(s) of cellulose biosynthesis and regulation. Given the hexagonal nature of the cellulose synthase rosette, it is assumed that the number of chains must be a multiple of six. We present molecular dynamics simulations on three different models of Iβ cellulose microfibrils, 18, 24, and 36 chains, to investigate their structure and dynamics in a hydrated environment. The 36-chain model stays in a conformational space that is very similar to the initial crystalline phase, while the 18- and 24-chain models sample a conformational space different from the crystalline structure yet similar to conformations observed in recent high-temperature molecular dynamics simulations. Major differences in the conformations sampled between the different models result from changes to the tilt of chains in different layers, specifically a second stage of tilt, increased rotation about the O2-C2 dihedral, and a greater sampling of non-TG exocyclic conformations, particularly the GG conformation in center layers and GT conformation in solvent-exposed exocyclic groups. With a reinterpretation of nuclear magnetic resonance data, specifically for contributions made to the C6 peak, data from the simulations suggest that the 18- and 24-chain structures are more viable models for an elementary cellulose microfibril, which also correlates with recent scattering and diffraction experimental data. These data inform biochemical and molecular studies that must explain how a six-particle cellulose synthase complex rosette synthesizes microfibrils likely comprised of either 18 or 24 chains. PMID:25786828

A Structurally Specialized Uniform Wall Layer is Essential for Constructing Wall Ingrowth Papillae in Transfer Cells

PubMed Central

Xia, Xue; Zhang, Hui-Ming; Offler, Christina E.; Patrick, John W.

2017-01-01

Transfer cells are characterized by wall labyrinths with either a flange or reticulate architecture. A literature survey established that reticulate wall ingrowth papillae ubiquitously arise from a modified component of their wall labyrinth, termed the uniform wall layer; a structure absent from flange transfer cells. This finding sparked an investigation of the deposition characteristics and role of the uniform wall layer using a Vicia faba cotyledon culture system. On transfer of cotyledons to culture, their adaxial epidermal cells spontaneously trans-differentiate to a reticulate architecture comparable to their abaxial epidermal transfer cell counterparts formed in planta. Uniform wall layer construction commenced once adaxial epidermal cell expansion had ceased to overlay the original outer periclinal wall on its inner surface. In contrast to the dense ring-like lattice of cellulose microfibrils in the original primary wall, the uniform wall layer was characterized by a sparsely dispersed array of linear cellulose microfibrils. A re-modeled cortical microtubule array exerted no influence on uniform wall layer formation or on its cellulose microfibril organization. Surprisingly, formation of the uniform wall layer was not dependent upon depositing a cellulose scaffold. In contrast, uniform wall cellulose microfibrils were essential precursors for constructing wall ingrowth papillae. On converging to form wall ingrowth papillae, the cellulose microfibril diameters increased 3-fold. This event correlated with up-regulated differential, and transfer-cell specific, expression of VfCesA3B while transcript levels of other cellulose biosynthetic-related genes linked with primary wall construction were substantially down-regulated. PMID:29259611

Roles of microtubules and cellulose microfibril assembly in the localization of secondary-cell-wall deposition in developing tracheary elements.

PubMed

Roberts, A W; Frost, A O; Roberts, E M; Haigler, C H

2004-12-01

The roles of cellulose microfibrils and cortical microtubules in establishing and maintaining the pattern of secondary-cell-wall deposition in tracheary elements were investigated with direct dyes to inhibit cellulose microfibril assembly and amiprophosmethyl to inhibit microtubule polymerization. When direct dyes were added to xylogenic cultures of Zinnia elegans L. mesophyll cells just before the onset of differentiation, the secondary cell wall was initially secreted as bands composed of discrete masses of stained material, consistent with immobilized sites of cellulose synthesis. The masses coalesced, forming truncated, sinuous or smeared thickenings, as secondary cell wall deposition continued. The absence of ordered cellulose microfibrils was confirmed by polarization microscopy and a lack of fluorescence dichroism as determined by laser scanning microscopy. Indirect immunofluorescence showed that cortical microtubules initially subtended the masses of dye-altered secondary cell wall material but soon became disorganized and disappeared. Although most of the secondary cell wall was deposited in the absence of subtending cortical microtubules in dye-treated cells, secretion remained confined to discrete regions of the plasma membrane. Examination of non-dye-treated cultures following application of microtubule inhibitors during various stages of secondary-cell-wall deposition revealed that the pattern became fixed at an early stage such that deposition remained localized in the absence of cortical microtubules. These observations indicate that cortical microtubules are required to establish, but not to maintain, patterned secondary-cell-wall deposition. Furthermore, cellulose microfibrils play a role in maintaining microtubule arrays and the integrity of the secondary-cell-wall bands during deposition.

A Structurally Specialized Uniform Wall Layer is Essential for Constructing Wall Ingrowth Papillae in Transfer Cells.

PubMed

Xia, Xue; Zhang, Hui-Ming; Offler, Christina E; Patrick, John W

2017-01-01

Transfer cells are characterized by wall labyrinths with either a flange or reticulate architecture. A literature survey established that reticulate wall ingrowth papillae ubiquitously arise from a modified component of their wall labyrinth, termed the uniform wall layer; a structure absent from flange transfer cells. This finding sparked an investigation of the deposition characteristics and role of the uniform wall layer using a Vicia faba cotyledon culture system. On transfer of cotyledons to culture, their adaxial epidermal cells spontaneously trans -differentiate to a reticulate architecture comparable to their abaxial epidermal transfer cell counterparts formed in planta . Uniform wall layer construction commenced once adaxial epidermal cell expansion had ceased to overlay the original outer periclinal wall on its inner surface. In contrast to the dense ring-like lattice of cellulose microfibrils in the original primary wall, the uniform wall layer was characterized by a sparsely dispersed array of linear cellulose microfibrils. A re-modeled cortical microtubule array exerted no influence on uniform wall layer formation or on its cellulose microfibril organization. Surprisingly, formation of the uniform wall layer was not dependent upon depositing a cellulose scaffold. In contrast, uniform wall cellulose microfibrils were essential precursors for constructing wall ingrowth papillae. On converging to form wall ingrowth papillae, the cellulose microfibril diameters increased 3-fold. This event correlated with up-regulated differential, and transfer-cell specific, expression of VfCesA3B while transcript levels of other cellulose biosynthetic-related genes linked with primary wall construction were substantially down-regulated.

Microtubule and cellulose microfibril orientation during plant cell and organ growth.

PubMed

Chan, J

2012-07-01

In this review, I ask the question of what is the relationship between growth and the orientations of microtubules and cellulose microfibrils in plant cells. This should be a relatively simple question to answer considering that text books commonly describe microtubules and cellulose microfibrils as hoops that drive expansion perpendicular to their orientation. However, recent live imaging techniques, which allow microtubules and cellulose synthase dynamics to be imaged simultaneously with cell elongation, show that cells can elongate with nonperpendicular microtubule arrays. In this review, I look at the significance of these different microtubule arrangements for growth and cell wall architecture and how these resultant walls differ from those derived from perpendicular arrays. I also discuss how these divergent arrays in stems may be important for coordinating growth between the different cell layers. This role reveals some general features of microtubule alignment that can be used to predict the growth status of organs. In conclusion, nonperpendicular arrays demonstrate alternative ways of cell elongation that do not require hooped arrays of microtubules and cellulose microfibrils. Such nonperpendicular arrays may be required for optimal growth and strengthening of tissues. © 2011 The Author Journal of Microscopy © 2011 Royal Microscopical Society.

Re-constructing our models of cellulose and primary cell wall assembly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cosgrove, Daniel J.

2014-11-16

The cellulose microfibril has more subtlety than is commonly recognized. Details of its structure may influence how matrix polysaccharides interact with its distinctive hydrophobic and hydrophilic surfaces to form a strong yet extensible structure. We report that recent advances in this field include the first structures of bacterial and plant cellulose synthases and revised estimates of microfibril structure, reduced from 36 to 18 chains. New results also indicate that cellulose interactions with xyloglucan are more limited than commonly believed, whereas pectin-cellulose interactions are more prevalent. Computational results indicate that xyloglucan binds tightest to the hydrophobic surface of cellulose microfibrils. Finally,more » wall extensibility may be controlled at limited regions (“biomechanical hotspots”) where cellulose-cellulose contacts are made, potentially mediated by trace amounts of xyloglucan.« less

Calcofluor white ST Alters the in vivo assembly of cellulose microfibrils.

PubMed

Haigler, C H; Brown, R M; Benziman, M

1980-11-21

The fluorescent brightener, Calcofluor White ST, prevents the in vivo assembly of crystalline cellulose microfibrils and ribbons by Acetobacter xylinum. In the presence of more than 0.01 percent Calcofluor, Acetobacter continues to synthesize high-molecular-weight beta-1,4 glucans. X-ray crystallography shows that the altered product exhibits no detectable crystallinity in the wet state, but upon drying it changes into crystalline cellulose I. Calcofluor alters cellulose crystallization by hydrogen bonding with glucan chains. Synthesis of this altered product is reversible and can be monitored with fluorescence and electron microscopy. Use of Calcofluor has made it possible to separate the processes of polymerization and crystallization leading to the biogenesis of cellulose microfibrils, and has suggested that crystallization occurs by a cell-directed. self-assembly process in Acetobacter xylinum.

Raman microspectroscopy as a diagnostic tool for the non-invasive analysis of fibrillin-1 deficiency in the skin and in the in vitro skin models.

PubMed

Brauchle, Eva; Bauer, Hannah; Fernes, Patrick; Zuk, Alexandra; Schenke-Layland, Katja; Sengle, Gerhard

2017-04-01

Fibrillin microfibrils and elastic fibers are critical determinants of elastic tissues where they define as tissue-specific architectures vital mechanical properties such as pliability and elastic recoil. Fibrillin microfibrils also facilitate elastic fiber formation and support the association of epithelial cells with the interstitial matrix. Mutations in fibrillin-1 (FBN1) are causative for the Marfan syndrome, a congenital multisystem disorder characterized by progressive deterioration of the fibrillin microfibril/ elastic fiber architecture in the cardiovascular, musculoskeletal, ocular, and dermal system. In this study, we utilized Raman microspectroscopy in combination with principal component analysis (PCA) to analyze the molecular consequences of fibrillin-1 deficiency in skin of a mouse model (GT8) of Marfan syndrome. In addition, full-thickness skin models incorporating murine wild-type and Fbn1 GT8/GT8 fibroblasts as well as human HaCaT keratinocytes were generated and analyzed. Skin models containing GT8 fibroblasts showed an altered epidermal morphology when compared to wild-type models indicating a new role for fibrillin-1 in dermal-epidermal crosstalk. Obtained Raman spectra together with PCA allowed to discriminate between healthy and deficient microfibrillar networks in murine dermis and skin models. Interestingly, results obtained from GT8 dermis and skin models showed similar alterations in molecular signatures triggered by fibrillin-1 deficiency such as amide III vibrations and decreased levels of glycan vibrations. Overall, this study indicates that Raman microspectroscopy has the potential to analyze subtle changes in fibrillin-1 microfibrils and elastic fiber networks. Therefore Raman microspectroscopy may be utilized as a non-invasive and sensitive diagnostic tool to identify connective tissue disorders and monitor their disease progression. Mutations in building blocks of the fibrillin microfibril/ elastic fiber network manifest in disease conditions such as aneurysms, emphysema or lax skin. Understanding how structural changes induced by fibrillin-1 mutation impact the architecture of fibrillin microfibrils, which then translates into an altered activation state of targeted growth factors, represents a huge challenge in elucidating the genotype-phenotype correlations in connective tissue disorders such as Marfan syndrome. This study shows that Raman microspectroscopy is able to reveal structural changes in fibrillin-1 microfibrils and elastic fiber networks and to discriminate between normal and diseased networks in vivo and in vitro. Therefore Raman microspectroscopy may be utilized as a non-invasive and sensitive diagnostic tool to identify connective tissue disorders and monitor their disease progression. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Fabrication of microfibrillated cellulose gel from waste pulp sludge via mild maceration combined with mechanical shearing

Treesearch

Nusheng Chen; Junyong Zhu; Zhaohui Tong

2016-01-01

This article describes a facile route, which combines mild maceration of waste pulp sludge and a mechanical shearing process, to prepare microfibrillated cellulose (MFC) with a high storage modulus. In the maceration, the mixture of glacial acetic acid and hydrogen peroxide was used to extract cellulose from never-dried waste pulp sludge. Then, two different mechanical...

Mechanical Properties versus Morphology of Ordered Polymers

DTIC Science & Technology

1980-05-01

for a similar banding observed in PPTA 30 fibers. The dark field results suggest each microfibril ribbon consists of a succession of narrow...transmission electron microscopy may be obtained by surface tension aided microfibril dispersion. The longitudinal sections of fibers obtained by...the value of c ( 0.08) obtained for native and regenerated cellulose , another class of stiff chain polymers16). (Deriva- tives of cellulose can be spun

Ultrastructure Processing of Ordered Polymers

DTIC Science & Technology

1990-01-18

from regenerated cellulose , then from synthetic polymer consisting of chemical raw materials derived from oils and coal. Since then, some scientists have...ordered crystal- line material, crystallite, throughout the fiber, which is composed of microfibrils and fibrils. The small crystallites are regularly...these flat ribbons appears to consist of smaller " microfibrils " of lateral dimension varying from 50-80 A, as described before(Figs. 15 and 16). These

Synthesis and Self-Assembly of Cellulose Microfibrils from Reconstituted Cellulose Synthase.

PubMed

Cho, Sung Hyun; Purushotham, Pallinti; Fang, Chao; Maranas, Cassandra; Díaz-Moreno, Sara M; Bulone, Vincent; Zimmer, Jochen; Kumar, Manish; Nixon, B Tracy

2017-09-01

Cellulose, the major component of plant cell walls, can be converted to bioethanol and is thus highly studied. In plants, cellulose is produced by cellulose synthase, a processive family-2 glycosyltransferase. In plant cell walls, individual β-1,4-glucan chains polymerized by CesA are assembled into microfibrils that are frequently bundled into macrofibrils. An in vitro system in which cellulose is synthesized and assembled into fibrils would facilitate detailed study of this process. Here, we report the heterologous expression and partial purification of His-tagged CesA5 from Physcomitrella patens Immunoblot analysis and mass spectrometry confirmed enrichment of PpCesA5. The recombinant protein was functional when reconstituted into liposomes made from yeast total lipid extract. The functional studies included incorporation of radiolabeled Glc, linkage analysis, and imaging of cellulose microfibril formation using transmission electron microscopy. Several microfibrils were observed either inside or on the outer surface of proteoliposomes, and strikingly, several thinner fibrils formed ordered bundles that either covered the surfaces of proteoliposomes or were spawned from liposome surfaces. We also report this arrangement of fibrils made by proteoliposomes bearing CesA8 from hybrid aspen. These observations describe minimal systems of membrane-reconstituted CesAs that polymerize β-1,4-glucan chains that coalesce to form microfibrils and higher-ordered macrofibrils. How these micro- and macrofibrils relate to those found in primary and secondary plant cell walls is uncertain, but their presence enables further study of the mechanisms that govern the formation and assembly of fibrillar cellulosic structures and cell wall composites during or after the polymerization process controlled by CesA proteins. © 2017 American Society of Plant Biologists. All Rights Reserved.

Unique aspects of the structure and dynamics of elementary Iβ cellulose microfibrils revealed by computational simulations.

PubMed

Oehme, Daniel P; Downton, Matthew T; Doblin, Monika S; Wagner, John; Gidley, Michael J; Bacic, Antony

2015-05-01

The question of how many chains an elementary cellulose microfibril contains is critical to understanding the molecular mechanism(s) of cellulose biosynthesis and regulation. Given the hexagonal nature of the cellulose synthase rosette, it is assumed that the number of chains must be a multiple of six. We present molecular dynamics simulations on three different models of Iβ cellulose microfibrils, 18, 24, and 36 chains, to investigate their structure and dynamics in a hydrated environment. The 36-chain model stays in a conformational space that is very similar to the initial crystalline phase, while the 18- and 24-chain models sample a conformational space different from the crystalline structure yet similar to conformations observed in recent high-temperature molecular dynamics simulations. Major differences in the conformations sampled between the different models result from changes to the tilt of chains in different layers, specifically a second stage of tilt, increased rotation about the O2-C2 dihedral, and a greater sampling of non-TG exocyclic conformations, particularly the GG conformation in center layers and GT conformation in solvent-exposed exocyclic groups. With a reinterpretation of nuclear magnetic resonance data, specifically for contributions made to the C6 peak, data from the simulations suggest that the 18- and 24-chain structures are more viable models for an elementary cellulose microfibril, which also correlates with recent scattering and diffraction experimental data. These data inform biochemical and molecular studies that must explain how a six-particle cellulose synthase complex rosette synthesizes microfibrils likely comprised of either 18 or 24 chains. © 2015 American Society of Plant Biologists. All Rights Reserved.

Mutant alleles of Arabidopsis RADIALLY SWOLLEN 4 and 7 reduce growth anisotropy without altering the transverse orientation of cortical microtubules or cellulose microfibrils.

PubMed

Wiedemeier, Allison M D; Judy-March, Jan E; Hocart, Charles H; Wasteneys, Geoffrey O; Williamson, Richard E; Baskin, Tobias I

2002-10-01

The anisotropic growth of plant cells depends on cell walls having anisotropic mechanical properties, which are hypothesized to arise from aligned cellulose microfibrils. To test this hypothesis and to identify genes involved in controlling plant shape, we isolated mutants in Arabidopsis thaliana in which the degree of anisotropic expansion of the root is reduced. We report here the characterization of mutants at two new loci, RADIALLY SWOLLEN 4 (RSW4) and RSW7. The radial swelling phenotype is temperature sensitive, being moderate (rsw7) or negligible (rsw4) at the permissive temperature, 19 degrees C, and pronounced at the restrictive temperature, 30 degrees C. After transfer to 30 degrees C, the primary root's elongation rate decreases and diameter increases, with all tissues swelling radially. Swelling is accompanied by ectopic cell production but swelling is not reduced when the extra cell production is eliminated chemically. A double mutant was generated, whose roots swell constitutively and more than either parent. Based on analytical determination of acid-insoluble glucose, the amount of cellulose was normal in rsw4 and slightly elevated in rsw7. The orientation of cortical microtubules was examined with immunofluorescence in whole mounts and in semi-thin plastic sections, and the orientation of microfibrils was examined with field-emission scanning electron microscopy and quantitative polarized-light microscopy. In the swollen regions of both mutants, cortical microtubules and cellulose microfibrils are neither depleted nor disoriented. Thus, oriented microtubules and microfibrils themselves are insufficient to limit radial expansion; to build a wall with high mechanical anisotropy, additional factors are required, supplied in part by RSW4 and RSW7.

Synthesis and Self-Assembly of Cellulose Microfibrils from Reconstituted Cellulose Synthase1[OPEN

PubMed Central

Purushotham, Pallinti; Fang, Chao; Maranas, Cassandra; Bulone, Vincent

2017-01-01

Cellulose, the major component of plant cell walls, can be converted to bioethanol and is thus highly studied. In plants, cellulose is produced by cellulose synthase, a processive family-2 glycosyltransferase. In plant cell walls, individual β-1,4-glucan chains polymerized by CesA are assembled into microfibrils that are frequently bundled into macrofibrils. An in vitro system in which cellulose is synthesized and assembled into fibrils would facilitate detailed study of this process. Here, we report the heterologous expression and partial purification of His-tagged CesA5 from Physcomitrella patens. Immunoblot analysis and mass spectrometry confirmed enrichment of PpCesA5. The recombinant protein was functional when reconstituted into liposomes made from yeast total lipid extract. The functional studies included incorporation of radiolabeled Glc, linkage analysis, and imaging of cellulose microfibril formation using transmission electron microscopy. Several microfibrils were observed either inside or on the outer surface of proteoliposomes, and strikingly, several thinner fibrils formed ordered bundles that either covered the surfaces of proteoliposomes or were spawned from liposome surfaces. We also report this arrangement of fibrils made by proteoliposomes bearing CesA8 from hybrid aspen. These observations describe minimal systems of membrane-reconstituted CesAs that polymerize β-1,4-glucan chains that coalesce to form microfibrils and higher-ordered macrofibrils. How these micro- and macrofibrils relate to those found in primary and secondary plant cell walls is uncertain, but their presence enables further study of the mechanisms that govern the formation and assembly of fibrillar cellulosic structures and cell wall composites during or after the polymerization process controlled by CesA proteins. PMID:28768815

Helicoidal Organization of Chitin in the Cuticle of the Migratory Locust Requires the Function of the Chitin Deacetylase2 Enzyme (LmCDA2)*

PubMed Central

Yu, Rongrong; Liu, Weimin; Li, Daqi; Zhao, Xiaoming; Ding, Guowei; Zhang, Min; Ma, Enbo; Zhu, KunYan; Li, Sheng; Moussian, Bernard; Zhang, Jianzhen

2016-01-01

In the three-dimensional extracellular matrix of the insect cuticle, horizontally aligned microfibrils composed of the polysaccharide chitin and associated proteins are stacked either parallel to each other or helicoidally. The underlying molecular mechanisms that implement differential chitin organization are largely unknown. To learn more about cuticle organization, we sought to study the role of chitin deacetylases (CDA) in this process. In the body cuticle of nymphs of the migratory locust Locusta migratoria, helicoidal chitin organization is changed to an organization with unidirectional microfibril orientation when LmCDA2 expression is knocked down by RNA interference. In addition, the LmCDA2-deficient cuticle is less compact suggesting that LmCDA2 is needed for chitin packaging. Animals with reduced LmCDA2 activity die at molting, underlining that correct chitin organization is essential for survival. Interestingly, we find that LmCDA2 localizes only to the initially produced chitin microfibrils that constitute the apical site of the chitin stack. Based on our data, we hypothesize that LmCDA2-mediated chitin deacetylation at the beginning of chitin production is a decisive reaction that triggers helicoidal arrangement of subsequently assembled chitin-protein microfibrils. PMID:27637332

Helicoidal Organization of Chitin in the Cuticle of the Migratory Locust Requires the Function of the Chitin Deacetylase2 Enzyme (LmCDA2).

PubMed

Yu, Rongrong; Liu, Weimin; Li, Daqi; Zhao, Xiaoming; Ding, Guowei; Zhang, Min; Ma, Enbo; Zhu, KunYan; Li, Sheng; Moussian, Bernard; Zhang, Jianzhen

2016-11-18

In the three-dimensional extracellular matrix of the insect cuticle, horizontally aligned microfibrils composed of the polysaccharide chitin and associated proteins are stacked either parallel to each other or helicoidally. The underlying molecular mechanisms that implement differential chitin organization are largely unknown. To learn more about cuticle organization, we sought to study the role of chitin deacetylases (CDA) in this process. In the body cuticle of nymphs of the migratory locust Locusta migratoria, helicoidal chitin organization is changed to an organization with unidirectional microfibril orientation when LmCDA2 expression is knocked down by RNA interference. In addition, the LmCDA2-deficient cuticle is less compact suggesting that LmCDA2 is needed for chitin packaging. Animals with reduced LmCDA2 activity die at molting, underlining that correct chitin organization is essential for survival. Interestingly, we find that LmCDA2 localizes only to the initially produced chitin microfibrils that constitute the apical site of the chitin stack. Based on our data, we hypothesize that LmCDA2-mediated chitin deacetylation at the beginning of chitin production is a decisive reaction that triggers helicoidal arrangement of subsequently assembled chitin-protein microfibrils. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Versatile gas-phase reactions for surface to bulk esterification of cellulose microfibrils aerogels.

PubMed

Fumagalli, Matthieu; Ouhab, Djamila; Boisseau, Sonia Molina; Heux, Laurent

2013-09-09

Aqueous suspensions of microfibrillated cellulose obtained by a high pressure homogenization process were freeze-dried after solvent exchange into tert-butanol. The resulting aerogels, which displayed a remarkable open morphology with a surface area reaching 100 m(2)/g, were subjected to a gas-phase esterification with palmitoyl chloride. Under these conditions, variations of the reaction temperature from 100 to 200 °C, of the reaction time from 0.5 to 2 h, and of the initial quantity of reagent, led to the preparation of a library of cellulose palmitates with DS varying from zero to 2.36. These products were characterized by gravimetry, FTIR, and (13)C solid-state NMR spectroscopy. Of special interest were the cellulose palmitate samples of low DS in the range of 0.1-0.4, which corresponded to hydrophobic cellulose microfibrils exclusively esterified at their surface while keeping intact their inner structure.

Cellulose fibres, nanofibrils and microfibrils: The morphological sequence of MFC components from a plant physiology and fibre technology point of view

NASA Astrophysics Data System (ADS)

Chinga-Carrasco, Gary

2011-06-01

During the last decade, major efforts have been made to develop adequate and commercially viable processes for disintegrating cellulose fibres into their structural components. Homogenisation of cellulose fibres has been one of the principal applied procedures. Homogenisation has produced materials which may be inhomogeneous, containing fibres, fibres fragments, fibrillar fines and nanofibrils. The material has been denominated microfibrillated cellulose (MFC). In addition, terms relating to the nano-scale have been given to the MFC material. Several modern and high-tech nano-applications have been envisaged for MFC. However, is MFC a nano-structure? It is concluded that MFC materials may be composed of (1) nanofibrils, (2) fibrillar fines, (3) fibre fragments and (4) fibres. This implies that MFC is not necessarily synonymous with nanofibrils, microfibrils or any other cellulose nano-structure. However, properly produced MFC materials contain nano-structures as a main component, i.e. nanofibrils.

Bratislava Symposium on Saccharides (7th) Programme and Abstracts

DTIC Science & Technology

1994-09-01

that of cellulose (1). Althoug the binding capacity of cellulose microfibrils is dependent on the sace of the binding un of the kmfbrul& xyloglucans...are not only party embedded in but are also parly free between microfibrils . suggesting cross-link to cellulose microfibuils (2). Xyloglucan...desediftcoli Y.-C.-M a 12. KoIlkovd B., Hricovfrni M., Sirmoutti R.: 43C NMR study of solid-stal, reaction of cellulose with lIgnin monomers 13. Joniak D

Study of Transport Properties and Structure of Extended-Chain Polymers: Diffusion and Solubility of Gases.

DTIC Science & Technology

1985-09-01

sonication of PPBT fibers .... .............. 123 53. (a) Proposed stacking forms of microfibrils with voids in intarval s .... .............. 124 (b... cellulose (Newns, 1956), Keratin (King, 1945) and -. inyl alcohol• 41 (Long and Thomoson, 1935). -The -water remaining inside PPBT in the deso-r-’tion...kinked ribbons is orcoosed n Figure (52) Each microfibril consists of a succession of narrow 0 crvstallites (50 x 500 A or smaller) enmbedded in

Gradients in Wall Mechanics and Polysaccharides along Growing Inflorescence Stems.

PubMed

Phyo, Pyae; Wang, Tuo; Kiemle, Sarah N; O'Neill, Hugh; Pingali, Sai Venkatesh; Hong, Mei; Cosgrove, Daniel J

2017-12-01

At early stages of Arabidopsis ( Arabidopsis thaliana ) flowering, the inflorescence stem undergoes rapid growth, with elongation occurring predominantly in the apical ∼4 cm of the stem. We measured the spatial gradients for elongation rate, osmotic pressure, cell wall thickness, and wall mechanical compliances and coupled these macroscopic measurements with molecular-level characterization of the polysaccharide composition, mobility, hydration, and intermolecular interactions of the inflorescence cell wall using solid-state nuclear magnetic resonance spectroscopy and small-angle neutron scattering. Force-extension curves revealed a gradient, from high to low, in the plastic and elastic compliances of cell walls along the elongation zone, but plots of growth rate versus wall compliances were strikingly nonlinear. Neutron-scattering curves showed only subtle changes in wall structure, including a slight increase in cellulose microfibril alignment along the growing stem. In contrast, solid-state nuclear magnetic resonance spectra showed substantial decreases in pectin amount, esterification, branching, hydration, and mobility in an apical-to-basal pattern, while the cellulose content increased modestly. These results suggest that pectin structural changes are connected with increases in pectin-cellulose interaction and reductions in wall compliances along the apical-to-basal gradient in growth rate. These pectin structural changes may lessen the ability of the cell wall to undergo stress relaxation and irreversible expansion (e.g. induced by expansins), thus contributing to the growth kinematics of the growing stem. © 2017 American Society of Plant Biologists. All Rights Reserved.

Breakdown of hierarchical architecture in cellulose during dilute acid pretreatments.

PubMed

Zhang, Yan; Inouye, Hideyo; Yang, Lin; Himmel, Michael E; Tucker, Melvin; Makowski, Lee

Cellulose is an attractive candidate as a feedstock for sustainable bioenergy because of its global abundance. Pretreatment of biomass has significant influence on the chemical availability of cellulose locked in recalcitrant microfibrils. Optimizing pretreatment depends on an understanding of its impact on the microscale and nanoscale molecular architecture. X-ray scattering experiments have been performed on native and pre-treated maize stover and models of cellulose architecture have been derived from these data. Ultra small-angle, very small-angle and small-angle X-ray scattering (USAXS, VSAXS and SAXS) probe three different levels of architectural scale. USAXS and SAXS have been used to study cellulose at two distinct length scales, modeling the fibrils as ~30 Å diameter rods packed into ~0.14 μm diameter bundles. VSAXS is sensitive to structural features at length scales between these two extremes. Detailed analysis of diffraction patterns from untreated and pretreated maize using cylindrical Guinier plots and the derivatives of these plots reveals the presence of substructures within the ~0.14 μm diameter bundles that correspond to grouping of cellulose approximately 30 nm in diameter. These sub-structures are resilient to dilute acid pretreatments but are sensitive to pretreatment when iron sulfate is added. These results provide evidence of the hierarchical arrangement of cellulose at three length scales and the evolution of these arrangements during pre-treatments.

Breakdown of hierarchical architecture in cellulose during dilute acid pretreatments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yan; Inouye, Hideyo; Yang, Lin

2015-02-28

Cellulose can work as a feedstock for sustainable bioenergy because of its global abundance. Pretreatment of biomass has significant influence on the chemical availability of cellulose locked in recalcitrant microfibrils. Optimizing pretreatment depends on an understanding of its impact on the microscale and nanoscale molecular architecture. X-ray scattering experiments have been performed on native and pre-treated maize stover and models of cellulose architecture have been derived from these data. Ultra small-angle, very small-angle and small-angle X-ray scattering (USAXS, VSAXS and SAXS) probe three different levels of architectural scale. USAXS and SAXS have been used to study cellulose at two distinctmore » length scales, modeling the fibrils as ~30 Å diameter rods packed into ~0.14 μm diameter bundles. VSAXS is sensitive to structural features at length scales between these two extremes. Detailed analysis of diffraction patterns from untreated and pretreated maize using cylindrical Guinier plots and the derivatives of these plots reveals the presence of substructures within the ~0.14 μm diameter bundles that correspond to grouping of cellulose approximately 30 nm in diameter. These sub-structures are resilient to dilute acid pretreatments but are sensitive to pretreatment when iron sulfate is added. Our results provide evidence of the hierarchical arrangement of cellulose at three length scales and the evolution of these arrangements during pre-treatments.« less

Breakdown of hierarchical architecture in cellulose during dilute acid pretreatments

DOE PAGES

Zhang, Yan; Inouye, Hideyo; Yang, Lin; ...

2015-02-28

Cellulose is an attractive candidate as a feedstock for sustainable bioenergy because of its global abundance. Pretreatment of biomass has significant influence on the chemical availability of cellulose locked in recalcitrant microfibrils. Optimizing pretreatment depends on an understanding of its impact on the microscale and nanoscale molecular architecture. X-ray scattering experiments have been performed on native and pre-treated maize stover and models of cellulose architecture have been derived from these data. Ultra small-angle, very small-angle and small-angle X-ray scattering (USAXS, VSAXS and SAXS) probe three different levels of architectural scale. USAXS and SAXS have been used to study cellulose atmore » two distinct length scales, modeling the fibrils as ~30 Å diameter rods packed into ~0.14 μm diameter bundles. VSAXS is sensitive to structural features at length scales between these two extremes. Detailed analysis of diffraction patterns from untreated and pretreated maize using cylindrical Guinier plots and the derivatives of these plots reveals the presence of substructures within the ~0.14 μm diameter bundles that correspond to grouping of cellulose approximately 30 nm in diameter. These sub-structures are resilient to dilute acid pretreatments but are sensitive to pretreatment when iron sulfate is added. Lastly, these results provide evidence of the hierarchical arrangement of cellulose at three length scales and the evolution of these arrangements during pre-treatments.« less

Supercritical CO2 and ionic liquids for the pretreatment of lignocellulosic biomass in bioethanol production.

PubMed

Gu, Tingyue; Held, Michael A; Faik, Ahmed

2013-01-01

Owing to high petroleum prices, there has been a major push in recent years to use lignocellulosic biomass as biorefinery feedstocks. Unfortunately, by nature's design, lignocellulosic biomass is notoriously recalcitrant. Cellulose is the most abundant renewable carbon source on the planet and comprises glucan polysaccharides which self-assemble into paracrystalline microfibrils. The extent of cellulose crystallinity largely contributes to biomass recalcitrance. Additionally, cellulose microfibrils are embedded into both hemicellulose and lignin polymeric networks, making cellulose accessibility an additional obstacle. Pretreatment is necessary before enzymatic hydrolysis in order to liberate high yields of glucose and other fermentable sugars from biomass polysaccharides. This work discusses two pretreatment methods, supercritical CO2 and ionic liquids (ILs). Both methods utilize green solvents that do not emit toxic vapours. Mechanisms for destroying or weakening biomass recalcitrance have been explored. Various pretreatment operating parameters such as temperature, pressure, time, dry biomass/solvent ratio, water content, etc. have been investigated for the pretreatment of various biomass types such as corn stover, switchgrass, sugarcane bagasse, soft and hard wood. The two pretreatment methods have their pros and cons. For example, supercritical CO2 explosion pretreatment uses inexpensive CO2, but requires a high pressure. By comparison, while IL pretreatment does not require an elevated pressure, ILs are still too expensive for large-scale uses. Further research and development are needed to make the two green pretreatment methods practical.

Simultaneous influence of pectin and xyloglucan on structure and mechanical properties of bacterial cellulose composites.

PubMed

Szymańska-Chargot, Monika; Chylińska, Monika; Cybulska, Justyna; Kozioł, Arkadiusz; Pieczywek, Piotr M; Zdunek, Artur

2017-10-15

The impact of the matrix polysaccharides on the cellulose microfibrils structure as well as on the mechanical properties of cell walls still remains an open question. Therefore, the aim of investigations was to determine the simultaneous influence of (i) different concentrations of pectins with constant concentration of xyloglucan, and (ii) different concentrations of xyloglucan with constant concentration of pectins on cellulose structure. Composites of bacterial cellulose (BC) produced by Komagataeibacter xylinus are considered to mimic natural plant cell walls. This investigation showed that the lower the ratio of xyloglucan to pectin was, the higher Young's modulus of BC composite was and also obtained cellulose microfibrils were thinner. The increasing concentration of xyloglucan to pectin also caused the drop down in microfibrils crystallinity degree with predominant structure of cellulose I β . In that case, also the length of cellulose chains was growing and reaching the highest value among all BC composites. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mechanical behavior of cellulose microfibrils in tension wood, in relation with maturation stress generation.

PubMed

Clair, Bruno; Alméras, Tancrède; Yamamoto, Hiroyuki; Okuyama, Takashi; Sugiyama, Junji

2006-08-01

A change in cellulose lattice spacing can be detected during the release of wood maturation stress by synchrotron x-ray diffraction experiment. The lattice strain was found to be the same order of magnitude as the macroscopic strain. The fiber repeat distance, 1.033 nm evaluated for tension wood after the release of maturation stress was equal to the conventional wood values, whereas the value before stress release was larger, corresponding to a fiber repeat of 1.035 nm, nearly equal to that of cotton and ramie. Interestingly, the fiber repeat varied from 1.033 nm for wood to 1.040 nm for algal cellulose, with an increasing order of lateral size of cellulose microfibrils so far reported. These lines of experiments demonstrate that, before the stress release, the cellulose was in a state of tension, which is, to our knowledge, the first experimental evidence supporting the assumption that tension is induced in cellulose microfibrils.

Finite element 3D modeling of mechanical behavior of mineralized collagen microfibrils.

PubMed

Barkaoui, Abdelwahed; Hambli, Ridha

2011-01-01

The aim of this work is to develop a 3D finite elements model to study the nanomechanical behavior of mineralized collagen microfibrils, which consists of three phases, (i) collagen phase formed by five tropocollagen (TC) molecules linked together with cross-links, (ii) a mineral phase (Hydroxyapatite), and (iii) impure mineral phase, and to investigate the important role of individual properties of every constituent. The mechanical and geometric properties (TC molecule diameter) of both tropocollagen and mineral were taken into consideration as well as cross-links, which was represented by spring elements with adjusted properties based on experimental data. In this paper an equivalent homogenized model was developed to assess the whole microfibril mechanical properties (Young's modulus and Poisson's ratio) under varying mechanical properties of each phase. In this study, both equivalent Young's modulus and Poisson's ratio, which were expressed as functions of Young's modulus of each phase, were obtained under tensile load with symmetric and periodic boundary conditions.

Cellulose synthase stoichiometry in aspen differs from Arabidopsis and Norway spruce.

PubMed

Zhang, Xueyang; Dominguez, Pia Guadalupe; Kumar, Manoj; Bygdell, Joakim; Miroshnichenko, Sergey; Sundberg, Bjorn; Wingsle, Gunnar; Niittyla, Totte

2018-05-14

Cellulose is synthesised at the plasma membrane by cellulose synthase complexes (CSCs) containing cellulose synthases (CESAs). Genetic analysis and CESA isoform quantification indicate that cellulose in the secondary cell walls of Arabidopsis (Arabidopsis thaliana) is synthesised by isoforms CESA4, CESA7 and CESA8 in equimolar amounts. Here, we used quantitative proteomics to investigate whether the CSC model based on Arabidopsis secondary cell wall CESA stoichiometry can be applied to the angiosperm tree aspen (Populus tremula) and the gymnosperm tree Norway spruce (Picea abies). In the developing xylem of aspen the secondary cell wall CESA stoichiometry was 3:2:1 for PtCESA8a/b : PtCESA4 : PtCESA7a/b, while in Norway spruce the stoichiometry was 1:1:1 as previously observed in Arabidopsis. Furthermore, in aspen tension wood the secondary cell wall CESA stoichiometry changed to 8:3:1 for PtCESA8a/b : PtCESA4 : PtCESA7a/b. PtCESA8b represented 73% of the total secondary cell wall CESA pool, and quantitative PCR analysis of CESA transcripts in cryo-sectioned tension wood revealed increased PtCESA8b expression during formation of the cellulose-enriched gelatinous layer while the transcripts of PtCESA4, PtCESA7a/b and PtCESA8a decreased. A wide-angle X-ray scattering analysis showed that the shift in CESA stoichiometry in tension wood coincided with an increase in crystalline cellulose microfibril diameter suggesting that the CSC CESA composition influences microfibril properties. The aspen CESA stoichiometry results raise the possibility of alternative CSC models, and suggest that homomeric PtCESA8b complexes are responsible for cellulose biosynthesis in the gelatinous layer in tension wood. {copyright, serif} 2018 American Society of Plant Biologists. All rights reserved.

Texture of cellulose microfibrils of root hair cell walls of Arabidopsis thaliana, Medicago truncatula, and Vicia sativa.

PubMed

Akkerman, M; Franssen-Verheijen, M A W; Immerzeel, P; Hollander, L D E N; Schel, J H N; Emons, A M C

2012-07-01

Cellulose is the most abundant biopolymer on earth, and has qualities that make it suitable for biofuel. There are new tools for the visualisation of the cellulose synthase complexes in living cells, but those do not show their product, the cellulose microfibrils (CMFs). In this study we report the characteristics of cell wall textures, i.e. the architectures of the CMFs in the wall, of root hairs of Arabidopsis thaliana, Medicago truncatula and Vicia sativa and compare the different techniques we used to study them. Root hairs of these species have a random primary cell wall deposited at the root hair tip, which covers the outside of the growing and fully grown hair. The secondary wall starts between 10 (Arabidopsis) and 40 (Vicia) μm from the hair tip and the CMFs make a small angle, Z as well as S direction, with the long axis of the root hair. CMFs are 3-4 nm wide in thin sections, indicating that single cellulose synthase complexes make them. Thin sections after extraction of cell wall matrix, leaving only the CMFs, reveal the type of wall texture and the orientation and width of CMFs, but CMF density within a lamella cannot be quantified, and CMF length is always underestimated by this technique. Field emission scanning electron microscopy and surface preparations for transmission electron microscopy reveal the type of wall texture and the orientation of individual CMFs. Only when the orientation of CMFs in subsequent deposited lamellae is different, their density per lamella can be determined. It is impossible to measure CMF length with any of the EM techniques. © 2012 The Authors Journal of Microscopy © 2012 Royal Microscopical Society.

Preparation using pectinase and characterization of nanofibers from orange peel waste in juice factories.

PubMed

Hideno, Akihiro; Abe, Kentaro; Yano, Hiroyuki

2014-06-01

This study reports the preparation and characterization of nanofibers consisting mainly of cellulose microfibrils from orange peel (OP), which is a significant byproduct of orange juice production. Three treatments (boiling, alkaline, and pectinase) were investigated with and without subsequent grinding treatment. It was possible to prepare the cellulose nanofibers (CNFs) using these methods, except for the boiling treatment with grinding. Interestingly, only pectinase and a mild-physical blender treatment without grinding produced nanofibers. The width of the nanofibers from OP was approximately 10 to 50 nm. The microfibril bundles of OP were considered to be thinner than those of commercial CNFs. Our data indicated that the removal of pectic polysaccharides and hemicelluloses covering the cellulose microfibrils was important for the preparation of nanofibers from OP. These nanofibers from OP using pectinase are proposed to be applicable as food materials, pharmaceuticals, and filters for the tractive characteristics of the sheet. This study demonstrates: (1) it was possible to prepare the nanofibers from orange peel using pectinase and (2) the width of the nanofibers from orange peel was approximately 10 to 50 nm. (3) Removal of polysaccharides such as pectin and hemicelluloses covering cellulose microfibrils was very important for preparation of nanofibers from OP. Considering the tractive characteristics of the sheets from nanofibers and the origin of orange peel, they are suitable for application of food materials, pharmaceuticals, and filters. © 2014 Institute of Food Technologists®

WallGen, software to construct layered cellulose-hemicellulose networks and predict their small deformation mechanics.

PubMed

Kha, Hung; Tuble, Sigrid C; Kalyanasundaram, Shankar; Williamson, Richard E

2010-02-01

We understand few details about how the arrangement and interactions of cell wall polymers produce the mechanical properties of primary cell walls. Consequently, we cannot quantitatively assess if proposed wall structures are mechanically reasonable or assess the effectiveness of proposed mechanisms to change mechanical properties. As a step to remedying this, we developed WallGen, a Fortran program (available on request) building virtual cellulose-hemicellulose networks by stochastic self-assembly whose mechanical properties can be predicted by finite element analysis. The thousands of mechanical elements in the virtual wall are intended to have one-to-one spatial and mechanical correspondence with their real wall counterparts of cellulose microfibrils and hemicellulose chains. User-defined inputs set the properties of the two polymer types (elastic moduli, dimensions of microfibrils and hemicellulose chains, hemicellulose molecular weight) and their population properties (microfibril alignment and volume fraction, polymer weight percentages in the network). This allows exploration of the mechanical consequences of variations in nanostructure that might occur in vivo and provides estimates of how uncertainties regarding certain inputs will affect WallGen's mechanical predictions. We summarize WallGen's operation and the choice of values for user-defined inputs and show that predicted values for the elastic moduli of multinet walls subject to small displacements overlap measured values. "Design of experiment" methods provide systematic exploration of how changed input values affect mechanical properties and suggest that changing microfibril orientation and/or the number of hemicellulose cross-bridges could change wall mechanical anisotropy.

Adsorption behavior of optical brightening agent on microfibrillated cellulose studied through inverse liquid chromatography: The need to correct for axial dispersion effect.

PubMed

Serroukh, Sonia; Huber, Patrick; Lallam, Abdelaziz

2018-01-19

Inverse liquid chromatography is a technique for studying solid/liquid interaction and most specifically for the determination of solute adsorption isotherm. For the first time, the adsorption behaviour of microfibrillated cellulose was assessed using inverse liquid chromatography. We showed that microfibrillated cellulose could adsorb 17 mg/g of tetrasulfonated optical brightening agent in typical papermaking conditions. The adsorbed amount of hexasulfonated optical brightening agent was lower (7 mg/g). The packing of the column with microfibrillated cellulose caused important axial dispersion (D a  = 5e-7 m²/s). Simulation of transport phenomena in the column showed that neglecting axial dispersion in the analysis of the chromatogram caused significant error (8%) in the determination of maximum adsorbed amount. We showed that conventional chromatogram analysis technique such as elution by characteristic point could not be used to fit our data. Using a bi-Langmuir isotherm model improved the fitting, but did not take into account axial dispersion, thus provided adsorption parameters which may have no physical significance. Using an inverse method with a single Langmuir isotherm, and fitting the transport equation to the chromatogram was shown to provide a satisfactory fitting to the chromatogram data. In general, the inverse method could be recommended to analyse inverse liquid chromatography data for column packing with significant axial dispersion (D a   > 1e-7 m²/s). Copyright © 2017 Elsevier B.V. All rights reserved.

Fibrillar assembly of bacterial cellulose in the presence of wood-based hemicelluloses.

PubMed

Penttilä, Paavo A; Imai, Tomoya; Sugiyama, Junji

2017-09-01

Composite materials mimicking the plant cell wall structure were made by culturing cellulose-producing bacteria together with secondary-wall hemicelluloses from wood. The effects of spruce galactoglucomannan (GGM) and beech xylan on the nanoscale morphology of bacterial cellulose were studied in the original, hydrated state with small-angle X-ray scattering (SAXS). The SAXS intensities were fitted with a model covering multiple levels of the hierarchical structure. Additional information on the structure of dried samples was obtained using scanning and transmission electron microscopy and infra-red spectroscopy. Both hemicelluloses induced a partial conversion of the cellulose crystal structure from I α to I β and a reduction of the cross-sectional dimensions of the cellulose microfibrils, thereby affecting also their packing into bundles. The differences were more pronounced in samples with xylan instead of GGM, and they became more significant with higher hemicellulose concentrations. Copyright © 2017 Elsevier B.V. All rights reserved.

Enzymatic hydrolysis of biomimetic bacterial cellulose-hemicellulose composites.

PubMed

Penttilä, Paavo A; Imai, Tomoya; Hemming, Jarl; Willför, Stefan; Sugiyama, Junji

2018-06-15

The production of biofuels and other chemicals from lignocellulosic biomass is limited by the inefficiency of enzymatic hydrolysis. Here a biomimetic composite material consisting of bacterial cellulose and wood-based hemicelluloses was used to study the effects of hemicelluloses on the enzymatic hydrolysis with a commercial cellulase mixture. Bacterial cellulose synthesized in the presence of hemicelluloses, especially xylan, was found to be more susceptible to enzymatic hydrolysis than hemicellulose-free bacterial cellulose. The reason for the easier hydrolysis could be related to the nanoscale structure of the substrate, particularly the packing of cellulose microfibrils into ribbons or bundles. In addition, small-angle X-ray scattering was used to show that the average nanoscale morphology of bacterial cellulose remained unchanged during the enzymatic hydrolysis. The reported easier enzymatic hydrolysis of bacterial cellulose produced in the presence of wood-based xylan offers new insights to overcome biomass recalcitrance through genetic engineering. Copyright © 2018 Elsevier Ltd. All rights reserved.

Palaeo-adaptive properties of the xylem of Metasequoia: mechanical/hydraulic compromises.

PubMed

Jagels, Richard; Visscher, George E; Lucas, John; Goodell, Barry

2003-07-01

The xylem of Metasequoia glyptostroboides Hu et Cheng is characterized by very low density (average specific gravity = 0.27) and tracheids with relatively large dimensions (length and diameter). The microfibril angle in the S2 layer of tracheid walls is large, even in outer rings, suggesting a cambial response to compressive rather than tensile stresses. In some cases, this compressive stress is converted to irreversible strain (plastic deformation), as evidenced by cell wall corrugations. The heartwood is moderately decay resistant, helping to prevent Brazier buckling. These xylem properties are referenced to the measured bending properties of modulus of rupture and modulus of elasticity, and compared with other low-to-moderate density conifers. The design strategy for Metasequoia is to produce a mechanically weak but hydraulically efficient xylem that permits rapid height growth and crown development to capture and dominate a wet site environment. The adaptability of these features to a high-latitude Eocene palaeoenvironment is discussed.

Effect of lignin content on changes occurring in poplar cellulose ultrastructure during dilute acid pretreatment

DOE PAGES

Sun, Qining; Foston, Marcus; Meng, Xianzhi; ...

2014-10-14

Obtaining a better understanding of the complex mechanisms occurring during lignocellulosic deconstruction is critical to the continued growth of renewable biofuel production. A key step in bioethanol production is thermochemical pretreatment to reduce plant cell wall recalcitrance for downstream processes. Previous studies of dilute acid pretreatment (DAP) have shown significant changes in cellulose ultrastructure that occur during pretreatment, but there is still a substantial knowledge gap with respect to the influence of lignin on these cellulose ultrastructural changes. This study was designed to assess how the presence of lignin influences DAP-induced changes in cellulose ultrastructure, which might ultimately have largemore » implications with respect to enzymatic deconstruction efforts. Native, untreated hybrid poplar (Populus trichocarpa x Populus deltoids) samples and a partially delignified poplar sample (facilitated by acidic sodium chlorite pulping) were separately pretreated with dilute sulfuric acid (0.10 M) at 160°C for 15 minutes and 35 minutes, respectively . Following extensive characterization, the partially delignified biomass displayed more significant changes in cellulose ultrastructure following DAP than the native untreated biomass. With respect to the native untreated poplar, delignified poplar after DAP (in which approximately 40% lignin removal occurred) experienced: increased cellulose accessibility indicated by increased Simons’ stain (orange dye) adsorption from 21.8 to 72.5 mg/g, decreased cellulose weight-average degree of polymerization (DP w) from 3087 to 294 units, and increased cellulose crystallite size from 2.9 to 4.2 nm. These changes following DAP ultimately increased enzymatic sugar yield from 10 to 80%. We conclude that, overall, the results indicate a strong influence of lignin content on cellulose ultrastructural changes occurring during DAP. With the reduction of lignin content during DAP, the enlargement of cellulose microfibril dimensions and crystallite size becomes more apparent. Further, this enlargement of cellulose microfibril dimensions is attributed to specific processes, including the co-crystallization of crystalline cellulose driven by irreversible inter-chain hydrogen bonding (similar to hornification) and/or cellulose annealing that converts amorphous cellulose to paracrystalline and crystalline cellulose. Essentially, lignin acts as a barrier to prevent cellulose crystallinity increase and cellulose fibril coalescence during DAP.« less

An Experimental Study on the Iso-Content-Based Angle Similarity Measure.

ERIC Educational Resources Information Center

Zhang, Jin; Rasmussen, Edie M.

2002-01-01

Retrieval performance of the iso-content-based angle similarity measure within the angle, distance, conjunction, disjunction, and ellipse retrieval models is compared with retrieval performance of the distance similarity measure and the angle similarity measure. Results show the iso-content-based angle similarity measure achieves satisfactory…

Corneal stroma microfibrils.

PubMed

Hanlon, Samuel D; Behzad, Ali R; Sakai, Lynn Y; Burns, Alan R

2015-03-01

Elastic tissue was first described well over a hundred years ago and has since been identified in nearly every part of the body. In this review, we examine elastic tissue in the corneal stroma with some mention of other ocular structures which have been more thoroughly described in the past. True elastic fibers consist of an elastin core surrounded by fibrillin microfibrils. However, the presence of elastin fibers is not a requirement and some elastic tissue is comprised of non-elastin-containing bundles of microfibrils. Fibers containing a higher relative amount of elastin are associated with greater elasticity and those without elastin, with structural support. Recently it has been shown that the microfibrils, not only serve mechanical roles, but are also involved in cell signaling through force transduction and the release of TGF-β. A well characterized example of elastin-free microfibril bundles (EFMBs) is found in the ciliary zonules which suspend the crystalline lens in the eye. Through contraction of the ciliary muscle they exert enough force to reshape the lens and thereby change its focal point. It is believed that the molecules comprising these fibers do not turn-over and yet retain their tensile strength for the life of the animal. The mechanical properties of the cornea (strength, elasticity, resiliency) would suggest that EFMBs are present there as well. However, many authors have reported that, although present during embryonic and early postnatal development, EFMBs are generally not present in adults. Serial-block-face imaging with a scanning electron microscope enabled 3D reconstruction of elements in murine corneas. Among these elements were found fibers that formed an extensive network throughout the cornea. In single sections these fibers appeared as electron dense patches. Transmission electron microscopy provided additional detail of these patches and showed them to be composed of fibrils (∼10 nm diameter). Immunogold evidence clearly identified these fibrils as fibrillin EFMBs and EFMBs were also observed with TEM (without immunogold) in adult mammals of several species. Evidence of the presence of EFMBs in adult corneas will hopefully pique an interest in further studies that will ultimately improve our understanding of the cornea's biomechanical properties and its capacity to repair. Copyright © 2015 Elsevier Ltd. All rights reserved.

Corneal Stroma Microfibrils

PubMed Central

Hanlon, Samuel D.; Behzad, Ali R.; Sakai, Lynn Y.; Burns, Alan R.

2015-01-01

Elastic tissue was first described well over a hundred years ago and has since been identified in nearly every part of the body. In this review, we examine elastic tissue in the corneal stroma with some mention of other ocular structures which have been more thoroughly described in the past. True elastic fibers consist of an elastin core surrounded by fibrillin microfibrils. However, the presence of elastin fibers is not a requirement and some elastic tissue is comprised of non-elastin-containing bundles of microfibrils. Fibers containing a higher relative amount of elastin are associated with greater elasticity and those without elastin, with structural support. Recently it has been shown that the microfibrils, not only serve mechanical roles, but are also involved in cell signaling through force transduction and the release of TGF-β. A well characterized example of elastin-free microfibril bundles (EFMBs) is found in the ciliary zonules which suspend the crystalline lens in the eye. Through contraction of the ciliary muscle they exert enough force to reshape the lens and thereby change its focal point. It is believed that the molecules comprising these fibers do not turn-over and yet retain their tensile strength for the life of the animal. The mechanical properties of the cornea (strength, elasticity, resiliency) would suggest that EFMBs are present there as well. However, many authors have reported that, although present during embryonic and early postnatal development, EFMBs are generally not present in adults. Serial-block-face imaging with a scanning electron microscope enabled 3D reconstruction of elements in murine corneas. Among these elements were found fibers that formed an extensive network throughout the cornea. In single sections these fibers appeared as electron dense patches. Transmission electron microscopy provided additional detail of these patches and showed them to be composed of fibrils (∼10nm diameter). Immunogold evidence clearly identified these fibrils as fibrillin EFMBs and EFMBs were also observed with TEM (without immunogold) in adult mammals of several species. Evidence of the presence of EFMBs in adult corneas will hopefully pique an interest in further studies that will ultimately improve our understanding of the cornea's biomechanical properties and its capacity to repair. PMID:25613072

Patterns of cell elongation in the determination of the final shape in galls of Baccharopelma dracunculifoliae (Psyllidae) on Baccharis dracunculifolia DC (Asteraceae).

PubMed

Magalhães, Thiago Alves; de Oliveira, Denis Coelho; Suzuki, Aline Yasko Marinho; Isaias, Rosy Mary dos Santos

2014-07-01

Cell redifferentiation, division, and elongation are recurrent processes, which occur during gall development, and are dependent on the cellulose microfibrils reorientation. We hypothesized that changes in the microfibrils orientation from non-galled tissues to galled ones occur and determine the final gall shape. This determination is caused by a new tissue zonation, its hyperplasia, and relative cell hypertrophy. The impact of the insect's activity on these patterns of cell development was herein tested in Baccharopelma dracunculifoliae-Baccharis dracunculifolia system. In this system, the microfibrils are oriented perpendicularly to the longest cell axis in elongated cells and randomly in isodiametric ones, either in non-galled or in galled tissues. The isodiametric cells of the abaxial epidermis in non-galled tissues divided and elongated periclinally, forming the outer gall epidermis. The anticlinally elongated cells of the abaxial palisade layer and the isodiametric cells of the spongy parenchyma originated the gall outer cortex with hypertrophied and periclinally elongated cells. The anticlinally elongated cells of the adaxial palisade layer originated the inner cortex with hypertrophied and periclinally elongated cells in young and mature galls and isodiametric cells in senescent galls. The isodiametric cells of the adaxial epidermis elongated periclinally in the inner gall epidermis. The current investigation demonstrates the role of cellulose microfibril reorientation for gall development. Once many factors other than this reorientation act on gall development, it should be interesting to check the possible relationship of the new cell elongation patterns with the pectic composition of the cell walls.

Application of a quick-freezing and deep-etching method to pathological diagnosis: a case of elastofibroma.

PubMed

Hemmi, Akihiro; Tabata, Masahiko; Homma, Taku; Ohno, Nobuhiko; Terada, Nobuo; Fujii, Yasuhisa; Ohno, Shinichi; Nemoto, Norimichi

2006-04-01

A case of elastofibroma in a middle-aged Japanese woman was examined by the quick-freezing and deep-etching (QF-DE) method, as well as by immunohistochemistry and conventional electron microscopy. The slowly growing tumor developed at the right scapular region and was composed of fibrous connective tissue with unique elastic materials called elastofibroma fibers. A normal elastic fiber consists of a central core and peripheral zone, in which the latter has small aggregates of 10 nm microfibrils. By the QF-DE method, globular structures consisting of numerous fibrils (5-20 nm in width) were observed between the collagen bundles. We could confirm that they were microfibril-rich peripheral zones of elastofibroma fibers by comparing the replica membrane and conventional electron microscopy. One of the characteristics of elastofibroma fibers is that they are assumed to contain numerous microfibrils. Immunohistochemically, spindle tumor cells showed positive immunoreaction for vimentin, whereas alpha-smooth muscle actin, desmin, S-100 protein and CD34 showed negative immunoreaction. By conventional electron microscopy, the tumor cell had thin cytoplasmic processes, pinocytotic vesicles and prominent rough endoplasmic reticulum. Abundant intracytoplasmic filaments were observed in some tumor cells. Thick lamina-like structures along with their inner nuclear membrane were often observed in the tumor cell nuclei. The whole image of the tumor cell was considered to be a periosteal-derived cell, which would produce numerous microfibrils in the peripheral zone of elastofibroma fibers. This study indicated that the QF-DE method could be applied to the pathological diagnosis and analysis of pathomechanism, even for surgical specimens obtained from a patient.

Cellulose-hemicellulose interaction in wood secondary cell-wall

NASA Astrophysics Data System (ADS)

Zhang, Ning; Li, Shi; Xiong, Liming; Hong, Yu; Chen, Youping

2015-12-01

The wood cell wall features a tough and relatively rigid fiber reinforced composite structure. It acts as a pressure vessel, offering protection against mechanical stress. Cellulose microfibrils, hemicellulose and amorphous lignin are the three major components of wood. The structure of secondary cell wall could be imagined as the same as reinforced concrete, in which cellulose microfibrils acts as reinforcing steel bar and hemicellulose-lignin matrices act as the concrete. Therefore, the interface between cellulose and hemicellulose/lignin plays a significant role in determine the mechanical behavior of wood secondary cell wall. To this end, we present a molecular dynamics (MD) simulation study attempting to quantify the strength of the interface between cellulose microfibrils and hemicellulose. Since hemicellulose binds with adjacent cellulose microfibrils in various patterns, the atomistic models of hemicellulose-cellulose composites with three typical binding modes, i.e. bridge, loop and random binding modes are constructed. The effect of the shape of hemicellulose chain on the strength of hemicellulose-cellulose composites under shear loadings is investigated. The contact area as well as hydrogen bonds between cellulose and hemicellulose, together with the covalent bonds in backbone of hemicellulose chain are found to be the controlling parameters which determine the strength of the interfaces in the composite system. For the bridge binding model, the effect of shear loading direction on the strength of the cellulose material is also studied. The obtained results suggest that the shear strength of wood-inspired engineering composites can be optimized through maximizing the formations of the contributing hydrogen bonds between cellulose and hemicellulose.

N-terminal domains of fibrillin 1 and fibrillin 2 direct the formation of homodimers: a possible first step in microfibril assembly.

PubMed Central

Trask, T M; Ritty, T M; Broekelmann, T; Tisdale, C; Mecham, R P

1999-01-01

Aggregation of fibrillin molecules via disulphide bonds is postulated to be an early step in microfibril assembly. By expressing fragments of fibrillin 1 and fibrillin 2 in a mammalian expression system, we found that the N-terminal region of each protein directs the formation of homodimers and that disulphide bonds stabilize this interaction. A large fragment of fibrillin 1 containing much of the region downstream from the N-terminus remained as a monomer when expressed in the same cell system, indicating that this region of the protein lacks dimerization domains. This finding also confirms that the overexpression of fibrillin fragments does not in itself lead to spurious dimer formation. Pulse-chase analysis demonstrated that dimer formation occurred intracellularly, suggesting that the process of fibrillin aggregation is initiated early after biosynthesis of the molecules. These findings also implicate the N-terminal region of fibrillin 1 and fibrillin 2 in directing the formation of a dimer intermediate that aggregates to form the functional microfibril. PMID:10359653

Effect of Intrinsic Twist on Length of Crystalline and Disordered Regions in Cellulose Microfibrils

NASA Astrophysics Data System (ADS)

Nili, Abdolmadjid; Shklyaev, Oleg; Zhao, Zhen; Zhong, Linghao; Crespi, Vincent

2013-03-01

Cellulose is the most abundant biological material in the world. It provides mechanical reinforcement for plant cell wall, and could potentially serve as renewable energy source for biofuel. Native cellulose forms a non-centrosymmetric chiral crystal due to lack of roto-inversion symmetry of constituent glucose chains. Chirality of cellulose crystal could result in an overall twist. Competition between unwinding torsional/extensional and twisting energy terms leads to twist induced frustration along fibril's axis. The accumulated frustration could be the origin of periodic disordered regions observed in cellulose microfibrils. These regions could play significant role in properties of cellulose bundles and ribbons as well as biological implications on plant cell walls. We propose a mechanical model based on Frenkel-Kontorova mechanism to investigate effects of radius dependent twist on crystalline size in cellulose microfibrils. Parameters of the model are adjusted according to all-atom molecular simulations. This work is supported by the US Department of Energy, Office of Basic Energy Sciences as part of The Center for LignoCellulose Structure and Formation, an Energy Frontier Research Center

Assembly and enlargement of the primary cell wall in plants

NASA Technical Reports Server (NTRS)

Cosgrove, D. J.

1997-01-01

Growing plant cells are shaped by an extensible wall that is a complex amalgam of cellulose microfibrils bonded noncovalently to a matrix of hemicelluloses, pectins, and structural proteins. Cellulose is synthesized by complexes in the plasma membrane and is extruded as a self-assembling microfibril, whereas the matrix polymers are secreted by the Golgi apparatus and become integrated into the wall network by poorly understood mechanisms. The growing wall is under high tensile stress from cell turgor and is able to enlarge by a combination of stress relaxation and polymer creep. A pH-dependent mechanism of wall loosening, known as acid growth, is characteristic of growing walls and is mediated by a group of unusual wall proteins called expansins. Expansins appear to disrupt the noncovalent bonding of matrix hemicelluloses to the microfibril, thereby allowing the wall to yield to the mechanical forces generated by cell turgor. Other wall enzymes, such as (1-->4) beta-glucanases and pectinases, may make the wall more responsive to expansin-mediated wall creep whereas pectin methylesterases and peroxidases may alter the wall so as to make it resistant to expansin-mediated creep.

Assembly and enlargement of the primary cell wall in plants.

PubMed

Cosgrove, D J

1997-01-01

Growing plant cells are shaped by an extensible wall that is a complex amalgam of cellulose microfibrils bonded noncovalently to a matrix of hemicelluloses, pectins, and structural proteins. Cellulose is synthesized by complexes in the plasma membrane and is extruded as a self-assembling microfibril, whereas the matrix polymers are secreted by the Golgi apparatus and become integrated into the wall network by poorly understood mechanisms. The growing wall is under high tensile stress from cell turgor and is able to enlarge by a combination of stress relaxation and polymer creep. A pH-dependent mechanism of wall loosening, known as acid growth, is characteristic of growing walls and is mediated by a group of unusual wall proteins called expansins. Expansins appear to disrupt the noncovalent bonding of matrix hemicelluloses to the microfibril, thereby allowing the wall to yield to the mechanical forces generated by cell turgor. Other wall enzymes, such as (1-->4) beta-glucanases and pectinases, may make the wall more responsive to expansin-mediated wall creep whereas pectin methylesterases and peroxidases may alter the wall so as to make it resistant to expansin-mediated creep.

A potential role for endogenous proteins as sacrificial sunscreens and antioxidants in human tissues.

PubMed

Hibbert, Sarah A; Watson, Rachel E B; Gibbs, Neil K; Costello, Patrick; Baldock, Clair; Weiss, Anthony S; Griffiths, Christopher E M; Sherratt, Michael J

2015-08-01

Excessive ultraviolet radiation (UVR) exposure of the skin is associated with adverse clinical outcomes. Although both exogenous sunscreens and endogenous tissue components (including melanins and tryptophan-derived compounds) reduce UVR penetration, the role of endogenous proteins in absorbing environmental UV wavelengths is poorly defined. Having previously demonstrated that proteins which are rich in UVR-absorbing amino acid residues are readily degraded by broadband UVB-radiation (containing UVA, UVB and UVC wavelengths) here we hypothesised that UV chromophore (Cys, Trp and Tyr) content can predict the susceptibility of structural proteins in skin and the eye to damage by physiologically relevant doses (up to 15.4 J/cm(2)) of solar UVR (95% UVA, 5% UVB). We show that: i) purified suspensions of UV-chromophore-rich fibronectin dimers, fibrillin microfibrils and β- and γ-lens crystallins undergo solar simulated radiation (SSR)-induced aggregation and/or decomposition and ii) exposure to identical doses of SSR has minimal effect on the size or ultrastructure of UV chromophore-poor tropoelastin, collagen I, collagen VI microfibrils and α-crystallin. If UV chromophore content is a factor in determining protein stability in vivo, we would expect that the tissue distribution of Cys, Trp and Tyr-rich proteins would correlate with regional UVR exposure. From bioinformatic analysis of 244 key structural proteins we identified several biochemically distinct, yet UV chromophore-rich, protein families. The majority of these putative UV-absorbing proteins (including the late cornified envelope proteins, keratin associated proteins, elastic fibre-associated components and β- and γ-crystallins) are localised and/or particularly abundant in tissues that are exposed to the highest doses of environmental UVR, specifically the stratum corneum, hair, papillary dermis and lens. We therefore propose that UV chromophore-rich proteins are localised in regions of high UVR exposure as a consequence of an evolutionary pressure to express sacrificial protein sunscreens which reduce UVR penetration and hence mitigate tissue damage. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

A potential role for endogenous proteins as sacrificial sunscreens and antioxidants in human tissues

PubMed Central

Hibbert, Sarah A.; Watson, Rachel E.B.; Gibbs, Neil K.; Costello, Patrick; Baldock, Clair; Weiss, Anthony S.; Griffiths, Christopher E.M.; Sherratt, Michael J.

2015-01-01

Excessive ultraviolet radiation (UVR) exposure of the skin is associated with adverse clinical outcomes. Although both exogenous sunscreens and endogenous tissue components (including melanins and tryptophan-derived compounds) reduce UVR penetration, the role of endogenous proteins in absorbing environmental UV wavelengths is poorly defined. Having previously demonstrated that proteins which are rich in UVR-absorbing amino acid residues are readily degraded by broadband UVB-radiation (containing UVA, UVB and UVC wavelengths) here we hypothesised that UV chromophore (Cys, Trp and Tyr) content can predict the susceptibility of structural proteins in skin and the eye to damage by physiologically relevant doses (up to 15.4 J/cm2) of solar UVR (95% UVA, 5% UVB). We show that: i) purified suspensions of UV-chromophore-rich fibronectin dimers, fibrillin microfibrils and β- and γ-lens crystallins undergo solar simulated radiation (SSR)-induced aggregation and/or decomposition and ii) exposure to identical doses of SSR has minimal effect on the size or ultrastructure of UV chromophore-poor tropoelastin, collagen I, collagen VI microfibrils and α-crystallin. If UV chromophore content is a factor in determining protein stability in vivo, we would expect that the tissue distribution of Cys, Trp and Tyr-rich proteins would correlate with regional UVR exposure. From bioinformatic analysis of 244 key structural proteins we identified several biochemically distinct, yet UV chromophore-rich, protein families. The majority of these putative UV-absorbing proteins (including the late cornified envelope proteins, keratin associated proteins, elastic fibre-associated components and β- and γ-crystallins) are localised and/or particularly abundant in tissues that are exposed to the highest doses of environmental UVR, specifically the stratum corneum, hair, papillary dermis and lens. We therefore propose that UV chromophore-rich proteins are localised in regions of high UVR exposure as a consequence of an evolutionary pressure to express sacrificial protein sunscreens which reduce UVR penetration and hence mitigate tissue damage. PMID:25911998

Multiscale approach including microfibril scale to assess elastic constants of cortical bone based on neural network computation and homogenization method.

PubMed

Barkaoui, Abdelwahed; Chamekh, Abdessalem; Merzouki, Tarek; Hambli, Ridha; Mkaddem, Ali

2014-03-01

The complexity and heterogeneity of bone tissue require a multiscale modeling to understand its mechanical behavior and its remodeling mechanisms. In this paper, a novel multiscale hierarchical approach including microfibril scale based on hybrid neural network (NN) computation and homogenization equations was developed to link nanoscopic and macroscopic scales to estimate the elastic properties of human cortical bone. The multiscale model is divided into three main phases: (i) in step 0, the elastic constants of collagen-water and mineral-water composites are calculated by averaging the upper and lower Hill bounds; (ii) in step 1, the elastic properties of the collagen microfibril are computed using a trained NN simulation. Finite element calculation is performed at nanoscopic levels to provide a database to train an in-house NN program; and (iii) in steps 2-10 from fibril to continuum cortical bone tissue, homogenization equations are used to perform the computation at the higher scales. The NN outputs (elastic properties of the microfibril) are used as inputs for the homogenization computation to determine the properties of mineralized collagen fibril. The mechanical and geometrical properties of bone constituents (mineral, collagen, and cross-links) as well as the porosity were taken in consideration. This paper aims to predict analytically the effective elastic constants of cortical bone by modeling its elastic response at these different scales, ranging from the nanostructural to mesostructural levels. Our findings of the lowest scale's output were well integrated with the other higher levels and serve as inputs for the next higher scale modeling. Good agreement was obtained between our predicted results and literature data. Copyright © 2013 John Wiley & Sons, Ltd.

Localization of Cell Wall Polysaccharides in Normal and Compression Wood of Radiata Pine: Relationships with Lignification and Microfibril Orientation1

PubMed Central

Donaldson, Lloyd A.; Knox, J. Paul

2012-01-01

The distribution of noncellulosic polysaccharides in cell walls of tracheids and xylem parenchyma cells in normal and compression wood of Pinus radiata, was examined to determine the relationships with lignification and cellulose microfibril orientation. Using fluorescence microscopy combined with immunocytochemistry, monoclonal antibodies were used to detect xyloglucan (LM15), β(1,4)-galactan (LM5), heteroxylan (LM10 and LM11), and galactoglucomannan (LM21 and LM22). Lignin and crystalline cellulose were localized on the same sections used for immunocytochemistry by autofluorescence and polarized light microscopy, respectively. Changes in the distribution of noncellulosic polysaccharides between normal and compression wood were associated with changes in lignin distribution. Increased lignification of compression wood secondary walls was associated with novel deposition of β(1,4)-galactan and with reduced amounts of xylan and mannan in the outer S2 (S2L) region of tracheids. Xylan and mannan were detected in all lignified xylem cell types (tracheids, ray tracheids, and thick-walled ray parenchyma) but were not detected in unlignified cell types (thin-walled ray parenchyma and resin canal parenchyma). Mannan was absent from the highly lignified compound middle lamella, but xylan occurred throughout the cell walls of tracheids. Using colocalization measurements, we confirmed that polysaccharides containing galactose, mannose, and xylose have consistent correlations with lignification. Low or unsubstituted xylans were localized in cell wall layers characterized by transverse cellulose microfibril orientation in both normal and compression wood tracheids. Our results support the theory that the assembly of wood cell walls, including lignification and microfibril orientation, may be mediated by changes in the amount and distribution of noncellulosic polysaccharides. PMID:22147521

The Structural Role of Elastic Fibers in the Cornea Investigated Using a Mouse Model for Marfan Syndrome

PubMed Central

White, Tomas L.; Lewis, Philip; Hayes, Sally; Fergusson, James; Bell, James; Farinha, Luis; White, Nick S.; Pereira, Lygia V.; Meek, Keith M.

2017-01-01

Purpose The presence of fibrillin-rich elastic fibers in the cornea has been overlooked in recent years. The aim of the current study was to elucidate their functional role using a mouse model for Marfan syndrome, defective in fibrillin-1, the major structural component of the microfibril bundles that constitute most of the elastic fibers. Methods Mouse corneas were obtained from animals with a heterozygous fibrillin-1 mutation (Fbn1+/−) and compared to wild type controls. Corneal thickness and radius of curvature were calculated using optical coherence tomography microscopy. Elastic microfibril bundles were quantified and visualized in three-dimensions using serial block face scanning electron microscopy. Transmission electron microscopy was used to analyze stromal ultrastructure and proteoglycan distribution. Center-to-center average interfibrillar spacing was determined using x-ray scattering. Results Fbn1+/− corneas were significantly thinner than wild types and displayed a higher radius of curvature. In the Fbn1+/− corneas, elastic microfibril bundles were significantly reduced in density and disorganized compared to wild-type controls, in addition to containing a higher average center-to-center collagen interfibrillar spacing in the center of the cornea. No other differences were detected in stromal ultrastructure or proteoglycan distribution between the two groups. Proteoglycan side chains appeared to colocalize with the microfibril bundles. Conclusions Elastic fibers have an important, multifunctional role in the cornea as highlighted by the differences observed between Fbn1+/− and wild type animals. We contend that the presence of normal quantities of structurally organized elastic fibers are required to maintain the correct geometry of the cornea, which is disrupted in Marfan syndrome. PMID:28395026

Hydrogen-Bonding Network and OH Stretch Vibration of Cellulose: Comparison of Computational Modeling with Polarized IR and SFG Spectra.

PubMed

Lee, Christopher M; Kubicki, James D; Fan, Bingxin; Zhong, Linghao; Jarvis, Michael C; Kim, Seong H

2015-12-10

Hydrogen bonds play critical roles in noncovalent directional interactions determining the crystal structure of cellulose. Although diffraction studies accurately determined the coordinates of carbon and oxygen atoms in crystalline cellulose, the structural information on hydrogen atoms involved in hydrogen-bonding is still elusive. This could be complemented by vibrational spectroscopy; but the assignment of the OH stretch peaks has been controversial. In this study, we performed calculations using density functional theory with dispersion corrections (DFT-D2) for the cellulose Iβ crystal lattices with the experimentally determined carbon and oxygen coordinates. DFT-D2 calculations revealed that the OH stretch vibrations of cellulose are highly coupled and delocalized through intra- and interchain hydrogen bonds involving all OH groups in the crystal. Additionally, molecular dynamics (MD) simulations of a single cellulose microfibril showed that the conformations of OH groups exposed at the microfibril surface are not well-defined. Comparison of the computation results with the experimentally determined IR dichroism of uniaxially aligned cellulose microfibrils and the peak positions of various cellulose crystals allowed unambiguous identification of OH stretch modes observed in the vibrational spectra of cellulose.

The stability of cellulose: a statistical perspective from a coarse-grained model of hydrogen-bond networks.

PubMed

Shen, Tongye; Gnanakaran, S

2009-04-22

A critical roadblock to the production of biofuels from lignocellulosic biomass is the efficient degradation of crystalline microfibrils of cellulose to glucose. A microscopic understanding of how different physical conditions affect the overall stability of the crystalline structure of microfibrils could facilitate the design of more effective protocols for their degradation. One of the essential physical interactions that stabilizes microfibrils is a network of hydrogen (H) bonds: both intrachain H-bonds between neighboring monomers of a single cellulose polymer chain and interchain H-bonds between adjacent chains. We construct a statistical mechanical model of cellulose assembly at the resolution of explicit hydrogen-bond networks. Using the transfer matrix method, the partition function and the subsequent statistical properties are evaluated. With the help of this lattice-based model, we capture the plasticity of the H-bond network in cellulose due to frustration and redundancy in the placement of H-bonds. This plasticity is responsible for the stability of cellulose over a wide range of temperatures. Stable intrachain and interchain H-bonds are identified as a function of temperature that could possibly be manipulated toward rational destruction of crystalline cellulose.

Differential wall growth in gravistimulated corn roots: Its timing and regulation

NASA Technical Reports Server (NTRS)

Serlin, B. S.

1985-01-01

The experiments designed to document cell-wall level changes which occur as a result of their gravistimulation are described. The goal of this research is to elucidate the mechanism and time frame of differential growth following a controlled gravistimulation. To achieve this, rates of wall deposition will be determined by following the incorporation of radioactive monosaccharides into the wall. Complementing this experiment will be a freeze-etch study directed at revealing the spatial arrangment of both newly-deposited microfibrils and microfibrils that were present in the growing root prior to stimulation. The second phase of the proposed research will examine the roles ethylene and Ca(2+) have in the modulation of differential wall changes during gravitropism. Ethylene and Ca(2+) have both been implicated as regulators of the gravitropic response in roots and they have also been implicated as regulators of the gravitropic response in roots and they have also been reported to exert some control on the orientation of microfibrils. Both of these agents will be manipulated in such a way as to reveal whether they have a direct influence on cell wall deposition and microfibrillar alignment during the geotropic response.

Onion epidermis as a new model to study the control of growth anisotropy in higher plants.

PubMed

Suslov, Dmitry; Verbelen, Jean-Pierre; Vissenberg, Kris

2009-01-01

To elucidate the role of cellulose microfibrils in the control of growth anisotropy, a link between their net orientation, in vitro cell wall extensibility, and anisotropic cell expansion was studied during development of the adaxial epidermis of onion (Allium cepa) bulb scales using polarization confocal microscopy, creep tests, and light microscopy. During growth the net cellulose alignment across the whole thickness of the outer epidermal wall changed from transverse through random to longitudinal and back to transverse relative to the bulb axis. Cell wall extension in vitro was always higher transverse than parallel to the net cellulose alignment. The direction of growth anisotropy was perpendicular to the net microfibril orientation and changed during development from longitudinal to transverse to the bulb axis. The correlation between the degree of growth anisotropy and the net cellulose alignment was poor. Thus the net cellulose microfibril orientation across the whole thickness of the outer periclinal epidermis wall defines the direction but not the degree of growth anisotropy. Strips isolated from the epidermis in the directions perpendicular and transverse to a net cellulose orientation can be used as an extensiometric model to prove a protein involvement in the control of growth anisotropy.

Chapter 4. Cytomechanics of hair basics of the mechanical stability.

PubMed

Popescu, Crisan; Höcker, Hartwig

2009-01-01

Hair is a complex "cornified" multicellular tissue composed of cuticle and cortex cells mechanically acting as a whole. The cuticle cells overlap and cortex cells interdigitate, all cells being composed of different morphological elements and separated by the cell membrane complex (CMC). The CMC and the morphological elements of the cortex cells, the macrofibrils, composed of microfibrils or intermediate filaments (IFs), and the intermacrofibrillar and intermicrofibrillar cement or the amorphous matrix material determine the mechanical properties of hair. The IFs consist of alpha-keratin molecules being arranged in a sophisticated way of two parallel monomers and antiparallel and shifted dimers rationalized by the amino acid composition and sequence. The mechanical properties of hair result from mechanical interlocking effects, hydrophobic effects, hydrogen bridges, Coulombic interactions, and (covalent) isodipeptide and, in particular, disulfide bridges on a molecular level. The mechanical models applied to hair are based on a simple two-component system, the microfibril/matrix structure. An important regime of the stress-strain curve is the transition of the molecules of the microfibrils from the alpha-helical to the beta-sheet structure. Due to the longitudinal orientation of the IF molecules the longitudinal swelling of the fibers in water is negligible, the radial swelling, however, is substantial.

Morphological changes in the cellulose and lignin components of biomass occur at different stages of steam pretreatment

DOE PAGES

Pingali, Sai Venkatesh; O'Neill, Hugh Michael; Nishiyama, Yoshiharu; ...

2014-01-09

Morphological changes to the different components of lignocellulosic biomass were observed as they occurred during steam pretreatment by placing a pressure reaction cell in a neutron beam and collecting time-resolved neutron scattering data. Changes to cellulose morphology occurred mainly in the heating phase, whereas changes in lignin morphology occurred mainly in the holding and cooling phases. During the heating stage, water is irreversibly expelled from cellulose microfibrils as the elementary fibrils coalesce. During the holding phase lignin aggregates begin to appear and they increase in size most noticeably during the cooling phase. This experiment demonstrates the unique information that inmore » situ small angle neutron scattering studies of pretreatment can provide. This approach is potentially useful in optimizing the heating, holding and cooling stages of pretreatments to allow the exact size and nature of lignin aggregates to be controlled in order to enhance enzyme accessibility to cellulose and therefore the efficiency of biomass conversion.« less

Property evaluations of dry-cast reconstituted bacterial cellulose/tamarind xyloglucan biocomposites.

PubMed

de Souza, Clayton F; Lucyszyn, Neoli; Woehl, Marco A; Riegel-Vidotti, Izabel C; Borsali, Redouane; Sierakowski, Maria Rita

2013-03-01

We describe the mechanical defibrillation of bacterial cellulose (BC) followed by the dry-cast generation of reconstituted BC films (RBC). Xyloglucan (XGT), extracted from tamarind seeds, was incorporated into the defibrillated cellulose at various compositions, and new films were created using the same process. Microscopy and contact angle analyses of films revealed an increase in the microfibre adhesion, a reduced polydispersity in the diameters of the microfibrils and increased hydrophobic behaviour as a function of %XGT. X-ray diffraction analysis revealed changes to the crystallographic planes of the RBC and the biocomposite films with preferential orientation along the (110) plane. Compared with BC, RBC/XGT biocomposite with 10% XGT exhibited improvement in its thermal properties and in Young's modulus. These results indicated a reorganisation of the microfibres with mechanical treatment, which when combined with hydrocolloids, can create cellulose-based materials that could be applied as scaffolding for tissue engineering and drug release. Copyright © 2012 Elsevier Ltd. All rights reserved.

Pectin impacts cellulose fibre architecture and hydrogel mechanics in the absence of calcium.

PubMed

Lopez-Sanchez, Patricia; Martinez-Sanz, Marta; Bonilla, Mauricio R; Wang, Dongjie; Walsh, Cherie T; Gilbert, Elliot P; Stokes, Jason R; Gidley, Michael J

2016-11-20

Pectin is a major polysaccharide in many plant cell walls and recent advances indicate that its role in wall mechanics is more important than previously thought. In this work cellulose hydrogels were synthesised in pectin solutions, as a biomimetic tool to investigate the influence of pectin on cellulose assembly and hydrogel mechanical properties. Most of the pectin (60-80%) did not interact at the molecular level with cellulose, as judged by small angle scattering techniques (SAXS and SANS). Despite the lack of strong interactions with cellulose, this pectin fraction impacted the mechanical properties of the hydrogels through poroelastic effects. The other 20-40% of pectin (containing neutral sugar sidechains) was able to interact intimately with cellulose microfibrils at the point of assembly. These results support the need to revise the role of pectin in cell wall architecture and mechanics, and; furthermore they assist the design of cellulose-based products through controlling the viscoelasticity of the fluid phase. Copyright © 2016 Elsevier Ltd. All rights reserved.

Palaeo‐adaptive Properties of the Xylem of Metasequoia: Mechanical/Hydraulic Compromises

PubMed Central

JAGELS, RICHARD; VISSCHER, GEORGE E.; LUCAS, JOHN; GOODELL, BARRY

2003-01-01

The xylem of Metasequoia glyptostroboides Hu et Cheng is characterized by very low density (average specific gravity = 0·27) and tracheids with relatively large dimensions (length and diameter). The microfibril angle in the S2 layer of tracheid walls is large, even in outer rings, suggesting a cambial response to compressive rather than tensile stresses. In some cases, this compressive stress is converted to irreversible strain (plastic deformation), as evidenced by cell wall corrugations. The heartwood is moderately decay resistant, helping to prevent Brazier buckling. These xylem properties are referenced to the measured bending properties of modulus of rupture and modulus of elasticity, and compared with other low‐to‐moderate density conifers. The design strategy for Metasequoia is to produce a mechanically weak but hydraulically efficient xylem that permits rapid height growth and crown development to capture and dominate a wet site environment. The adaptability of these features to a high‐latitude Eocene palaeoenvironment is discussed. PMID:12763758

Seasonal and clonal variation in cellulose microfibril orientation during cell wall formation of tracheids in Cryptomeria japonica.

PubMed

Jyske, Tuula; Fujiwara, Takeshi; Kuroda, Katsushi; Iki, Taiichi; Zhang, Chunhua; Jyske, Tuomas K; Abe, Hisashi

2014-08-01

To investigate the biological mechanism by which trees control the changes in microfibril (MF) orientation among secondary cell wall layers of conifer tracheids, we studied seasonal variation in the orientation of newly deposited MFs during tracheid cell wall development in Japanese cedar (Cryptomeria japonica D. Don) trees growing in Central Japan (36°36'N, 140°39'E). Sample blocks were repeatedly collected from four 16-year-old clones of different origins during the growing season of 2010 to investigate the hypotheses that changes in cellulose MF orientation between wall layers exhibited seasonal and clonal differences. The progressive change in the orientation of newly deposited MFs on the primary and secondary cell wall layers of tracheids was detected by field-emission-scanning electron microscopy. Tracheid production and differentiation was studied by light microscopy. We observed a decreasing trend in the orientation of deposited MFs from earlywood to latewood in the S2 and S1 layers, where MFs appeared in a Z-helix. In contrast, no seasonal pattern in the orientation of the MFs in the S-helix was observed. Minor clonal variation was observed in the phenology of tracheid production and differentiation. We concluded that a seasonal decreasing trend in the orientation of the MFs in the Z-helix in S1 and S2 was present, whereas the MFs in other layers exhibited minor random variations. Thus, the orientation of the MFs in S2 was affected by seasonal factors, whereas the MFs in other layers were more intrinsically controlled. The within-ring variations in the MF orientation and thus the resulting average MF angle might also be related to genotypic differences in the tracheid production and differentiation rate. However, our results do not exclude other intrinsic and environmental regulations in the change in MF orientation, which remains a topic for future studies. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Cell wall formation in zoospores of Allomyces arbuscula. II. Development of surface structure of encysted haploid zoospores, rhizoids, and hyphae.

PubMed

Kroh, M; Hendriks, H; Kirby, E G; Sassen, M M

1976-08-01

Development of haploid meiospores of Allomyces arbuscula into germling cells with rhizoids and hyphae was followed during incubation in complete growth medium. The surface structure of encysted meiospores, rhizoids and hyphae before and after extraction of amorphous materials with ethanolic KOH was studied by means of carbon-platinum replicas. After 2--3 min incubation in complete medium 10% of the meiospores were surrounded by a cell wall containing microfibrils embedded in a matrix. Structure of cell walls of encysted meiospores, rhizoids, and hyphae differ from one another by the location of amorphous materials and by the arrangement of chitin microfibrils.

On the molecular origins of biomass recalcitrance: the interaction network and solvation structures of cellulose microfibrils.

PubMed

Gross, Adam S; Chu, Jhih-Wei

2010-10-28

Biomass recalcitrance is a fundamental bottleneck to producing fuels from renewable sources. To understand its molecular origin, we characterize the interaction network and solvation structures of cellulose microfibrils via all-atom molecular dynamics simulations. The network is divided into three components: intrachain, interchain, and intersheet interactions. Analysis of their spatial dependence and interaction energetics indicate that intersheet interactions are the most robust and strongest component and do not display a noticeable dependence on solvent exposure. Conversely, the strength of surface-exposed intrachain and interchain hydrogen bonds is significantly reduced. Comparing the interaction networks of I(β) and I(α) cellulose also shows that the number of intersheet interactions is a clear descriptor that distinguishes the two allomorphs and is consistent with the observation that I(β) is the more stable form. These results highlight the dominant role of the often-overlooked intersheet interactions in giving rise to biomass recalcitrance. We also analyze the solvation structures around the surfaces of microfibrils and show that the structural and chemical features at cellulose surfaces constrict water molecules into specific density profiles and pair correlation functions. Calculations of water density and compressibility in the hydration shell show noticeable but not drastic differences. Therefore, specific solvation structures are more prominent signatures of different surfaces.

Solid-state NMR investigations of cellulose structure and interactions with matrix polysaccharides in plant primary cell walls.

PubMed

Wang, Tuo; Hong, Mei

2016-01-01

Until recently, the 3D architecture of plant cell walls was poorly understood due to the lack of high-resolution techniques for characterizing the molecular structure, dynamics, and intermolecular interactions of the wall polysaccharides in these insoluble biomolecular mixtures. We introduced multidimensional solid-state NMR (SSNMR) spectroscopy, coupled with (13)C labelling of whole plants, to determine the spatial arrangements of macromolecules in near-native plant cell walls. Here we review key evidence from 2D and 3D correlation NMR spectra that show relatively few cellulose-hemicellulose cross peaks but many cellulose-pectin cross peaks, indicating that cellulose microfibrils are not extensively coated by hemicellulose and all three major polysaccharides exist in a single network rather than two separate networks as previously proposed. The number of glucan chains in the primary-wall cellulose microfibrils has been under active debate recently. We show detailed analysis of quantitative (13)C SSNMR spectra of cellulose in various wild-type (WT) and mutant Arabidopsis and Brachypodium primary cell walls, which consistently indicate that primary-wall cellulose microfibrils contain at least 24 glucan chains. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Differential regulation of cellulose orientation at the inner and outer face of epidermal cells in the Arabidopsis hypocotyl.

PubMed

Crowell, Elizabeth Faris; Timpano, Hélène; Desprez, Thierry; Franssen-Verheijen, Tiny; Emons, Anne-Mie; Höfte, Herman; Vernhettes, Samantha

2011-07-01

It is generally believed that cell elongation is regulated by cortical microtubules, which guide the movement of cellulose synthase complexes as they secrete cellulose microfibrils into the periplasmic space. Transversely oriented microtubules are predicted to direct the deposition of a parallel array of microfibrils, thus generating a mechanically anisotropic cell wall that will favor elongation and prevent radial swelling. Thus far, support for this model has been most convincingly demonstrated in filamentous algae. We found that in etiolated Arabidopsis thaliana hypocotyls, microtubules and cellulose synthase trajectories are transversely oriented on the outer surface of the epidermis for only a short period during growth and that anisotropic growth continues after this transverse organization is lost. Our data support previous findings that the outer epidermal wall is polylamellate in structure, with little or no anisotropy. By contrast, we observed perfectly transverse microtubules and microfibrils at the inner face of the epidermis during all stages of cell expansion. Experimental perturbation of cortical microtubule organization preferentially at the inner face led to increased radial swelling. Our study highlights the previously underestimated complexity of cortical microtubule organization in the shoot epidermis and underscores a role for the inner tissues in the regulation of growth anisotropy.

Differential Regulation of Cellulose Orientation at the Inner and Outer Face of Epidermal Cells in the Arabidopsis Hypocotyl[W

PubMed Central

Crowell, Elizabeth Faris; Timpano, Hélène; Desprez, Thierry; Franssen-Verheijen, Tiny; Emons, Anne-Mie; Höfte, Herman; Vernhettes, Samantha

2011-01-01

It is generally believed that cell elongation is regulated by cortical microtubules, which guide the movement of cellulose synthase complexes as they secrete cellulose microfibrils into the periplasmic space. Transversely oriented microtubules are predicted to direct the deposition of a parallel array of microfibrils, thus generating a mechanically anisotropic cell wall that will favor elongation and prevent radial swelling. Thus far, support for this model has been most convincingly demonstrated in filamentous algae. We found that in etiolated Arabidopsis thaliana hypocotyls, microtubules and cellulose synthase trajectories are transversely oriented on the outer surface of the epidermis for only a short period during growth and that anisotropic growth continues after this transverse organization is lost. Our data support previous findings that the outer epidermal wall is polylamellate in structure, with little or no anisotropy. By contrast, we observed perfectly transverse microtubules and microfibrils at the inner face of the epidermis during all stages of cell expansion. Experimental perturbation of cortical microtubule organization preferentially at the inner face led to increased radial swelling. Our study highlights the previously underestimated complexity of cortical microtubule organization in the shoot epidermis and underscores a role for the inner tissues in the regulation of growth anisotropy. PMID:21742992

Characterization of the viscoelastic behavior of a simplified collagen micro-fibril based on molecular dynamics simulations.

PubMed

Ghodsi, Hossein; Darvish, Kurosh

2016-10-01

Collagen fibril is a major component of connective tissues such as bone, tendon, blood vessels, and skin. The mechanical properties of this highly hierarchical structure are greatly influenced by the presence of covalent cross-links between individual collagen molecules. This study investigates the viscoelastic behavior of a collagen lysine-lysine cross-link based on creep simulations with applied forces in the range or 10 to 2000pN using steered molecular dynamics (SMD). The viscoelastic model of the cross-link was combined with a system composed by two segments of adjacent collagen molecules hence representing a reduced viscoelastic model for a simplified micro-fibril. It was found that the collagen micro-fibril assembly had a steady-state Young׳s modulus ranging from 2.24 to 3.27GPa, which is in agreement with reported experimental measurements. The propagation of longitudinal force wave along the molecule was implemented by adding a delay element to the model. The force wave speed was found to be correlated with the speed of one-dimensional elastic waves in rods. The presented reduced model with three degrees of freedom can serve as a building block for developing models of the next level of hierarchy, i.e., a collagen fibril. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of surface modified cellulose microfibrils on the improved mechanical properties of poly (lactic acid).

PubMed

Johari, Atul P; Kurmvanshi, S K; Mohanty, S; Nayak, S K

2016-03-01

Cellulose microfibrils (CMF) were extracted from sisal fiber and characterized. Biocomposites of PLA reinforced with CMF were fabricated employing melt blending technique followed by injection moulding. The biocomposites were subjected to various characterization studies to investigate the effect of CMF within the PLA matrix. Differential scanning calorimetry (DSC) measurements confirmed that the addition of CMF accelerates the crystallization process of PLA matrix. Addition of 5 wt.% of CMF with and without compatibilizers and plasticizers such as maleic anhydride, polyethylene glycol and acetyltributyl citrate in PLA improved the crystallization of PLA up to 100 °C. MA grafting gave moderate effects on both the stiffness and ductility, exhibiting optimum properties. Copyright © 2015 Elsevier B.V. All rights reserved.

Structural characterization of a mixed-linkage glucan deficient mutant reveals alteration in cellulose microfibril orientation in rice coleoptile mesophyll cell walls

PubMed Central

Smith-Moritz, Andreia M.; Hao, Zhao; Fernández-Niño, Susana G.; Fangel, Jonatan U.; Verhertbruggen, Yves; Holman, Hoi-Ying N.; Willats, William G. T.; Ronald, Pamela C.; Scheller, Henrik V.; Heazlewood, Joshua L.; Vega-Sánchez, Miguel E.

2015-01-01

The CELLULOSE SYNTHASE-LIKE F6 (CslF6) gene was previously shown to mediate the biosynthesis of mixed-linkage glucan (MLG), a cell wall polysaccharide that is hypothesized to be tightly associated with cellulose and also have a role in cell expansion in the primary cell wall of young seedlings in grass species. We have recently shown that loss-of-function cslf6 rice mutants do not accumulate MLG in most vegetative tissues. Despite the absence of a structurally important polymer, MLG, these mutants are unexpectedly viable and only show a moderate growth compromise compared to wild type. Therefore these mutants are ideal biological systems to test the current grass cell wall model. In order to gain a better understanding of the role of MLG in the primary wall, we performed in-depth compositional and structural analyses of the cell walls of 3 day-old rice seedlings using various biochemical and novel microspectroscopic approaches. We found that cellulose content as well as matrix polysaccharide composition was not significantly altered in the MLG deficient mutant. However, we observed a significant change in cellulose microfibril bundle organization in mesophyll cell walls of the cslf6 mutant. Using synchrotron source Fourier Transform Mid-Infrared (FTM-IR) Spectromicroscopy for high-resolution imaging, we determined that the bonds associated with cellulose and arabinoxylan, another major component of the primary cell walls of grasses, were in a lower energy configuration compared to wild type, suggesting a slightly weaker primary wall in MLG deficient mesophyll cells. Taken together, these results suggest that MLG may influence cellulose deposition in mesophyll cell walls without significantly affecting anisotropic growth thus challenging MLG importance in cell wall expansion. PMID:26347754

Nanocellulose patents trends: a comprehensive review on patents on cellulose nanocrystals, microfibrillated and bacterial cellulose.

PubMed

Charreau, Hernan; Foresti, Maria L; Vazquez, Analia

2013-01-01

Cellulose nanoparticles (i.e. cellulose elements having at least one dimension in the 1-100 nm range) have received increasing attention during the last decade. This is not only evident in academic articles, but it is also manifested by the increasing number of nanocellulose patents that are published every year. In the current review, nanocellulose patents are reviewed using specific software which provides valuable information on the annual number of patents that have been published throughout the years, main patent owners, most prolific inventors, and patents on the field that have received more citations. Patent statistics on rod-like cellulose nanoparticles extracted from plants by acid hydrolysis (nanocrystals), mechanical treatment leading to microfibrillated cellulose (MFC), and microbially produced nanofibrils (bacterial cellulose, BC) are analyzed in detail. The aim of the current review is to provide researchers with patent information which may help them in visualizing the evolution of nanocellulose technology, both as a whole and also divided among the different nanosized particles that are currently the subject of outstanding scientific attention. Then, patents are not only analyzed by their content, but also by global statistics which will reveal the moment at which different cellulose nanoparticles technologies achieved a breakthrough, the relative interest received by different nanocellulose particles throughout the years, the companies that have been most interested in this technology, the most prolific inventors, and the patents that have had more influence in further developments. It is expected that the results showing the explosion that nanocellulose technology is experiencing in current days will still bring more research on the topic and contribute to the expansion of nanocellulosics applications.

Structural characterization of a mixed-linkage glucan deficient mutant reveals alteration in cellulose microfibril orientation in rice coleoptile mesophyll cell walls

DOE PAGES

Smith-Moritz, Andreia M.; Hao, Zhao; Fernández-Nino, Susana G.; ...

2015-08-18

The CELLULOSE SYNTHASE-LIKE F6 (CslF6) gene was previously shown to mediate the biosynthesis of mixed-linkage glucan (MLG), a cell wall polysaccharide that is hypothesized to be tightly associated with cellulose and also have a role in cell expansion in the primary cell wall of young seedlings in grass species. We have recently shown that loss-of-function cslf6 rice mutants do not accumulate MLG in most vegetative tissues. Despite the absence of a structurally important polymer, MLG, these mutants are unexpectedly viable and only show a moderate growth compromise compared to wild type. Therefore these mutants are ideal biological systems to testmore » the current grass cell wall model. In order to gain a better understanding of the role of MLG in the primary wall, we performed in-depth compositional and structural analyses of the cell walls of 3 day-old rice seedlings using various biochemical and novel microspectroscopic approaches. We found that cellulose content as well as matrix polysaccharide composition was not significantly altered in the MLG deficient mutant. However, we observed a significant change in cellulose microfibril bundle organization in mesophyll cell walls of the cslf6 mutant. Using synchrotron source Fourier Transform Mid-Infrared (FTM-IR) Spectromicroscopy for high-resolution imaging, we determined that the bonds associated with cellulose and arabinoxylan, another major component of the primary cell walls of grasses, were in a lower energy configuration compared to wild type, suggesting a slightly weaker primary wall in MLG deficient mesophyll cells. Finally, taken together, these results suggest that MLG may influence cellulose deposition in mesophyll cell walls without significantly affecting anisotropic growth thus challenging MLG importance in cell wall expansion.« less

Normal number of CGG repeats in the FMR-1 gene and abnormal incorporation of fibrillin into the extracellular matrix in Lujan Syndrome

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenhaw, G.A.; Stone, C.; Milewicz, D.

1994-09-01

Lujan syndrome is an X-linked condition that includes mild-to-moderate mental retardation, poor social integration, normal secondary sexual development with normal testicular size, generalized hypotonia, hypernasal voice and dolichostenomelia. Major cardiac complications and lens dislocation have not been reported although severe myopia may occur. All reported cases have had negative cytogenetic screening for fra(X) syndrome but establishing this constellation of findings as a distinctive entity has been difficult. We report 4 males in two sibships with clinical findings consistent with Lujan syndrome, normal karyotypes, negative cytogenetic screening for fra(X) syndrome and a normal number of CGG repeats in the FMR-1 gene.more » Dermal fibroblasts explanted from one of the affected males were used to study fibrillin synthesis secretion and extracellular matrix incorporation into microfibrils. Cells from the affected individual showed normal synthesis and secretion of fibrillin when compared to control cells, but the fibrillin was not incorporated into the extracellular matrix. These results suggest the presence of a gene on the X chromosome which may play a role in microfibril assembly and when deficient may disrupt the incorporation of fibrillin into microfibrils. This may be important not only in normal body morphogenesis but also in the development/function of the brain. More affected individuals are needed to investigate these findings further.« less

Surface functional group dependent apatite formation on bacterial cellulose microfibrils network in a simulated body fluid.

PubMed

Nge, Thi Thi; Sugiyama, Junji

2007-04-01

The apatite forming ability of biopolymer bacterial cellulose (BC) has been investigated by soaking different BC specimens in a simulated body fluid (1.5 SBF) under physiological conditions, at 37 degrees C and pH 7.4, mimicking the natural process of apatite formation. From ATR-FTIR spectra and ICP-AES analysis, the crystalline phase nucleated on the BC microfibrils surface was calcium deficient carbonated apatite through initial formation of octacalcium phosphate (OCP) or OCP like calcium phosphate phase regardless of the substrates. Morphology of the deposits from SEM, FE-SEM, and TEM observations revealed the fine structure of thin film plates uniting together to form apatite globules of various size (from <1 mum to 3 mum) with respect to the substrates. Surface modification by TEMPO (2,2,6,6-tetramethylpyperidine-1-oxyl)-mediated oxidation, which can readily form active carboxyl functional groups upon selective oxidation of primary hydroxyl groups on the surface of BC microfibrils, enhanced the rate of apatite nucleation. Ion exchanged treatment with calcium chloride solution after TEMPO-mediated oxidation was found to be remarkably different from other BC substrates with the highest deposit weight and the smallest apatite globules size. The role of BC substrates to induce mineralization rate differs according to the nature of the BC substrates, which strongly influences the growth behavior of the apatite crystals. (c) 2006 Wiley Periodicals, Inc.

The xyloglucan-cellulose assembly at the atomic scale.

PubMed

Hanus, Jaroslav; Mazeau, Karim

2006-05-01

The assembly of cell wall components, cellulose and xyloglucan (XG), was investigated at the atomistic scale using molecular dynamics simulations. A molecular model of a cellulose crystal corresponding to the allomorph Ibeta and exhibiting a flexible complex external morphology was employed to mimic the cellulose microfibril. The xyloglucan molecules considered were the three typical basic repeat units, differing only in the size of one of the lateral chain. All the investigated XG fragments adsorb nonspecifically onto cellulose fiber; multiple arrangements are equally probable, and every cellulose surface was capable of binding the short XG molecules. The following structural effects emerged: XG molecules that do not have any long side chains tended to adapt themselves nicely to the topology of the microfibril, forming a flat, outstretched conformation with all the sugar residues interacting with the surface. In contrast, the XG molecules, which have long side chains, were not able to adopt a flat conformation that would enable the interaction of all the XG residues with the surface. In addition to revealing the fundamental atomistic details of the XG adsorption on cellulose, the present calculations give a comprehensive understanding of the way the XG molecules can unsorb from cellulose to create a network that forms the cell wall. Our revisited view of the adsorption features of XG on cellulose microfibrils is consistent with experimental data, and a model of the network is proposed. Copyright (c) 2006 Wiley Periodicals, Inc.

Characterization of Cellulose Synthesis in Plant Cells

PubMed Central

Maleki, Samaneh Sadat; Mohammadi, Kourosh; Ji, Kong-shu

2016-01-01

Cellulose is the most significant structural component of plant cell wall. Cellulose, polysaccharide containing repeated unbranched β (1-4) D-glucose units, is synthesized at the plasma membrane by the cellulose synthase complex (CSC) from bacteria to plants. The CSC is involved in biosynthesis of cellulose microfibrils containing 18 cellulose synthase (CesA) proteins. Macrofibrils can be formed with side by side arrangement of microfibrils. In addition, beside CesA, various proteins like the KORRIGAN, sucrose synthase, cytoskeletal components, and COBRA-like proteins have been involved in cellulose biosynthesis. Understanding the mechanisms of cellulose biosynthesis is of great importance not only for improving wood production in economically important forest trees to mankind but also for plant development. This review article covers the current knowledge about the cellulose biosynthesis-related gene family. PMID:27314060

Impact of plant matrix polysaccharides on cellulose produced by surface-tethered cellulose synthases.

PubMed

Basu, Snehasish; Omadjela, Okako; Zimmer, Jochen; Catchmark, Jeffrey M

2017-04-15

Surface immobilized BcsA-B cellulose synthases synthesize crystalline cellulose II under in vitro conditions and were used to explore the interaction between cellulose and hemicelluloses and pectin. The morphology of the cellulose microfibrils changed in the presence of xyloglucan and glucomannan, while pectin did not significantly impact morphology. X-ray diffractometry and FT-IR spectroscopy indicated that crystal size and crystallinity were significantly affected by xyloglucan and glucomannan but not altered by pectin. Glucomannan had the most significant impact on the structure of cellulose and inhibits crystallization. The presence of xyloglucan and glucomannan prevents the proper assembly of cellulose microfibrils and changes the crystalline properties of cellulose II in in vitro conditions, but did not have any impact on cellulose allomorph. Copyright © 2017 Elsevier Ltd. All rights reserved.

Selectively Structural Determination of Cellulose and Hemicellulose in Plant Cell Wall

NASA Astrophysics Data System (ADS)

Huang, Shih-Chun; Park, Yong; Cosgrove, Daniel; Maranas, Janna; Janna Maranas Team; Daniel Cosgrove Team

2013-03-01

Primary plant cell walls support the plant body, and regulate cell size, and plant growth. It contains several biopolymers that can be categorized into three groups: cellulose, hemicellulose and pectin. To determine the structure of plant cell wall, we use small angle neutron scattering in combination with selective deuteration and contrast matching method. We compare the structure between wild Arabidopsis thaliana and its xyloglucan-deficient mutant. Hemicellulose in both samples forms coil with similar radii of gyration, and weak scattering from the mutant suggests a limited amount of hemicellulose in the xyloglucan-deficient mutant. We observe good amount of hemicellulose coating on cellulose microfibrils only in wild Arabidopsis. The absence of coating in its xyloglucan-deficient mutation suggests the other polysaccharides do not have comparable interaction with cellulose. This highlights the importance of xyloglucan in plant cell wall. At larger scale, the average distance between cellulose fibril is found smaller than reported value, which directly reflects on their smaller matured plant size. U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Center for LignoCellulose Structure and Formation

Determination of cellulose crystallinity from powder diffraction diagrams: Powder Diffraction Diagrams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindner, Benjamin; Petridis, Loukas; Langan, Paul

2014-10-01

Commonly one-dimensional (1D) (spherically averaged) powder diffraction diagrams are used to determine the degree of cellulose crystallinity in biomass samples. Here, it is shown using molecular modeling how disorder in cellulose fibrils can lead to considerable uncertainty in conclusions drawn concerning crystallinity based on 1D powder diffraction data alone. For example, cellulose microfibrils that contain both crystalline and noncrystalline segments can lead to powder diffraction diagrams lacking identifiable peaks, while microfibrils without any crystalline segments can lead to such peaks. Moreover, this leads to false positives, that is, assigning disordered cellulose as crystalline, and false negatives, that is, categorizing fibrilsmore » with crystalline segments as amorphous. Finally, the reliable determination of the fraction of crystallinity in any given biomass sample will require a more sophisticated approach combining detailed experiment and simulation.« less

Deformation and failure mechanism of secondary cell wall in Spruce late wood

NASA Astrophysics Data System (ADS)

Adusumalli, Ramesh-Babu; Raghavan, Rejin; Ghisleni, Rudy; Zimmermann, Tanja; Michler, Johann

2010-08-01

The deformation and failure of the secondary cell wall of Spruce wood was studied by in-situ SEM compression of micropillars machined by the focused ion beam technique. The cell wall exhibited yield strength values of approximately 160 MPa and large scale plasticity. High resolution SEM imaging post compression revealed bulging of the pillars followed by shear failure. With additional aid of cross-sectional analysis of the micropillars post compression, a model for deformation and failure mechanism of the cell wall has been proposed. The cell wall consists of oriented cellulose microfibrils with high aspect ratio embedded in a hemicellulose-lignin matrix. The deformation of the secondary wall occurs by asymmetric out of plane bulging because of buckling of the microfibrils. Failure of the cell wall following the deformation occurs by the formation of a shear or kink band.

Losartan and captopril treatment rescue normal thrombus formation in microfibril associated glycoprotein-1 (MAGP1) deficient mice.

PubMed

Vassequi-Silva, Tallita; Pereira, Danielle Sousa; Nery Diez, Ana Cláudia C; Braga, Guilherme G; Godoy, Juliana A; Mendes, Camila B; Dos Santos, Leonardo; Krieger, José E; Antunes, Edson; Costa, Fábio T M; Vicente, Cristina P; Werneck, Claudio C

2016-02-01

MAGP1 is a glycoprotein present in the elastic fibers and is a part of the microfibrils components. MAGP1 interacts with von Willebrand factor and the active form of TGF-β and BMP. In mice lacking MAGP1, thrombus formation is delayed, increasing the occlusion time of carotid artery despite presenting normal blood coagulation in vitro. MAGP1-containing microfibrils may play a role in hemostasis and thrombosis. In this work, we evaluated the function of MAGP1 and its relation to TGF-β in the arterial thrombosis process. We analyzed thrombus formation time in wild type and MAGP1-deficient mice comparing Rose Bengal and Ferric Chloride induced arterial lesion. The potential participation of TGF-β in this process was accessed when we treated both wild type and MAGP1-deficient mice with losartan (an antihypertensive drug that decreases TGF-β activity) or captopril (an angiotensin converting enzyme inhibitor that was used as a control antihypertensive drug). Besides, we evaluated thrombus embolization and the gelatinolytic activity in the arterial walls in vitro and ex vivo. Losartan and captopril were able to recover the thrombus formation time without changing blood pressure, activated partial thromboplastin time (aPTT), PT (prothrombin time), platelet aggregation and adhesion, but decreased gelatinase activity. Our results suggest that both treatments are effective in the prevention of the sub-endothelial ECM degradation, allowing the recovery of normal thrombus formation. Copyright © 2015 Elsevier Ltd. All rights reserved.

On the role of stress anisotropy in the growth of stems.

PubMed

Baskin, Tobias I; Jensen, Oliver E

2013-11-01

We review the role of anisotropic stress in controlling the growth anisotropy of stems. Instead of stress, growth anisotropy is usually considered in terms of compliance. Anisotropic compliance is typical of cell walls, because they contain aligned cellulose microfibrils, and it appears to be sufficient to explain the growth anisotropy of an isolated cell. Nevertheless, a role for anisotropic stress in the growth of stems is indicated by certain growth responses that appear too rapid to be accounted for by changes in cell-wall compliance and because the outer epidermal wall of most growing stems has microfibrils aligned axially, an arrangement that would favour radial expansion based on cell-wall compliance alone. Efforts to quantify stress anisotropy in the stem have found that it is predominantly axial, and large enough in principle to explain the elongation of the epidermis, despite its axial microfibrils. That the epidermis experiences a stress deriving from the inner tissue, the so-called 'tissue stress', has been widely recognized; however, the origin of the dominant axial direction remains obscure. Based on geometry, an isolated cylindrical cell should have an intramural stress anisotropy favouring the transverse direction. Explanations for tissue stress have invoked differential elastic moduli, differential plastic deformation (so-called differential growth), and a phenomenon analogous to the maturation stress generated by secondary cell walls. None of these explanations has been validated. We suggest that understanding the role of stress anisotropy in plant growth requires a deeper understanding of the nature of stress in hierarchical, organic structures.

Understanding Ionic Liquid Pretreatment of Lignocellulosic Biomasses

USDA-ARS?s Scientific Manuscript database

Pretreatment of biomass is essential for breaking apart highly ordered and crystalline plant cell walls and loosening the lignin and hemicellulose conjugation to cellulose microfibrills, thereby facilitating enzyme accessibility and adsorption and reducing costs of downstream saccharification proces...

Differential Regulation of Elastic Fiber Formation by Fibulin-4 and -5*

PubMed Central

Choudhury, Rawshan; McGovern, Amanda; Ridley, Caroline; Cain, Stuart A.; Baldwin, Andrew; Wang, Ming-Chuan; Guo, Chun; Mironov, Aleksandr; Drymoussi, Zoe; Trump, Dorothy; Shuttleworth, Adrian; Baldock, Clair; Kielty, Cay M.

2009-01-01

Fibulin-4 and -5 are extracellular glycoproteins with essential non-compensatory roles in elastic fiber assembly. We have determined how they interact with tropoelastin, lysyl oxidase, and fibrillin-1, thereby revealing how they differentially regulate assembly. Strong binding between fibulin-4 and lysyl oxidase enhanced the interaction of fibulin-4 with tropoelastin, forming ternary complexes that may direct elastin cross-linking. In contrast, fibulin-5 did not bind lysyl oxidase strongly but bound tropoelastin in terminal and central regions and could concurrently bind fibulin-4. Both fibulins differentially bound N-terminal fibrillin-1, which strongly inhibited their binding to lysyl oxidase and tropoelastin. Knockdown experiments revealed that fibulin-5 controlled elastin deposition on microfibrils, although fibulin-4 can also bind fibrillin-1. These experiments provide a molecular account of the distinct roles of fibulin-4 and -5 in elastic fiber assembly and how they act in concert to chaperone cross-linked elastin onto microfibrils. PMID:19570982

MAGP1, the extracellular matrix, and metabolism

PubMed Central

Craft, Clarissa S

2014-01-01

Adipose tissue and the extracellular matrix were once considered passive players in regulating physiological processes. Now, both entities are acknowledged for their capacity to engage signal transduction pathways, and for their involvement in maintaining normal tissue homeostasis. We recently published a series of studies that identified a novel mechanism whereby an extracellular matrix molecule, MAGP1 (microfibril associated glycoprotein 1), can regulate energy metabolism in adipose tissue. MAGP1 is a component of extracellular microfibrils and plays a supportive role in maintaining thermoregulation by indirectly regulating expression of the thermogenic uncoupling proteins (UCPs). The focus of this commentary is to draw attention to the role of the extracellular matrix in regulating the bioavailability of signaling molecules, like transforming growth factor β (TGFβ), and exemplify that a better understanding of the extracellular matrix's biological properties could unveil a new source of therapeutic targets for metabolic diseases. PMID:26167404

MAGP1, the extracellular matrix, and metabolism.

PubMed

Craft, Clarissa S

2015-01-01

Adipose tissue and the extracellular matrix were once considered passive players in regulating physiological processes. Now, both entities are acknowledged for their capacity to engage signal transduction pathways, and for their involvement in maintaining normal tissue homeostasis. We recently published a series of studies that identified a novel mechanism whereby an extracellular matrix molecule, MAGP1 (microfibril associated glycoprotein 1), can regulate energy metabolism in adipose tissue. MAGP1 is a component of extracellular microfibrils and plays a supportive role in maintaining thermoregulation by indirectly regulating expression of the thermogenic uncoupling proteins (UCPs). The focus of this commentary is to draw attention to the role of the extracellular matrix in regulating the bioavailability of signaling molecules, like transforming growth factor β (TGFβ), and exemplify that a better understanding of the extracellular matrix's biological properties could unveil a new source of therapeutic targets for metabolic diseases.

Microscopic Examination of Chitosan Polyphosphate Beads with Entrapped Spores of the Biocontrol Agent, Streptomyces melanosporofaciens EF-76

NASA Astrophysics Data System (ADS)

Jobin, Guy; Grondin, Gilles; Couture, Geneviève; Beaulieu, Carole

2005-04-01

Spores of the biocontrol agent, Streptomyces melanosporofaciens EF-76, were entrapped by complex coacervation in beads composed of a macromolecular complex (MC) of chitosan and polyphosphate. A proportion of spores entrapped in beads survived the entrapment procedure as shown by treating spores from chitosan beads with a dye allowing the differentiation of live and dead cells. The spore-loaded chitosan beads could be digested by a chitosanase, suggesting that, once introduced in soil, the beads would be degraded to release the biocontrol agent. Spore-loaded beads were examined by optical and scanning electron microscopy because the release of the biological agent depends on the spore distribution in the chitosan beads. The microscopic examination revealed that the beads had a porous surface and contained a network of inner microfibrils. Spores were entrapped in both the chitosan microfibrils and the bead lacuna.

Cellulose nanocrystals, nanofibers, and their composites as renewable smart materials

NASA Astrophysics Data System (ADS)

Kim, Jaehwan; Zhai, Lindong; Mun, Seongcheol; Ko, Hyun-U.; Yun, Young-Min

2015-04-01

Cellulose is one of abundant renewable biomaterials in the world. Over 1.5 trillion tons of cellulose is produced per year in nature by biosynthesis, forming microfibrils which in turn aggregate to form cellulose fibers. Using new effective methods these microfibrils can be disintegrated from the fibers to nanosized materials, so called cellulose nanocrystal (CNC) and cellulose nanofiber (CNF). The CNC and CNF have extremely good strength properties, dimensional stability, thermal stability and good optical properties on top of their renewable behavior, which can be a building block of new materials. This paper represents recent advancement of cellulose nanocrystals and cellulose nanofibers, followed by their possibility for smart materials. Natural behaviors, extraction, modification of cellulose nanocrystals and fibers are explained and their synthesis with nanomaterials is introduced, which is necessary to meet the technological requirements for smart materials. Also, its challenges are addressed.

Dispersions of attractive semiflexible fiberlike colloidal particles from bacterial cellulose microfibrils.

PubMed

Kuijk, Anke; Koppert, Remco; Versluis, Peter; van Dalen, Gerard; Remijn, Caroline; Hazekamp, Johan; Nijsse, Jaap; Velikov, Krassimir P

2013-11-26

We prepared dispersions from bacterial cellulose microfibrils (CMF) of a commercial Nata de Coco source. We used an ultra-high-energy mechanical deagglomeration process that is able to disperse the CMFs from the pellicle in which they are organized in an irregular network. Because of the strong attractions between the CMFs, the dispersion remained highly heterogeneous, consisting of fiber bundles, flocs, and voids spanning tens to hundreds of micrometers depending on concentration. The size of these flocs increased with CMF concentration, the size of the bundles stayed constant, and the size of the voids decreased. The observed percolation threshold in MFC dispersions is lower than the theoretical prediction, which is accounted for by the attractive interactions in the system. Because bacterial cellulose is chemically very pure, it can be used to study the interaction of attractive and highly shape-anisotropic, semiflexible fiberlike colloidal particles.

Estimation of canopy carotenoid content of winter wheat using multi-angle hyperspectral data

NASA Astrophysics Data System (ADS)

Kong, Weiping; Huang, Wenjiang; Liu, Jiangui; Chen, Pengfei; Qin, Qiming; Ye, Huichun; Peng, Dailiang; Dong, Yingying; Mortimer, A. Hugh

2017-11-01

Precise estimation of carotenoid (Car) content in crops, using remote sensing data, could be helpful for agricultural resources management. Conventional methods for Car content estimation were mostly based on reflectance data acquired from nadir direction. However, reflectance acquired at this direction is highly influenced by canopy structure and soil background reflectance. Off-nadir observation is less impacted, and multi-angle viewing data are proven to contain additional information rarely exploited for crop Car content estimation. The objective of this study was to explore the potential of multi-angle observation data for winter wheat canopy Car content estimation. Canopy spectral reflectance was measured from nadir as well as from a series of off-nadir directions during different growing stages of winter wheat, with concurrent canopy Car content measurements. Correlation analyses were performed between Car content and the original and continuum removed spectral reflectance. Spectral features and previously published indices were derived from data obtained at different viewing angles and were tested for Car content estimation. Results showed that spectral features and indices obtained from backscattering directions between 20° and 40° view zenith angle had a stronger correlation with Car content than that from the nadir direction, and the strongest correlation was observed from about 30° backscattering direction. Spectral absorption depth at 500 nm derived from spectral data obtained from 30° backscattering direction was found to reduce the difference induced by plant cultivars greatly. It was the most suitable for winter wheat canopy Car estimation, with a coefficient of determination 0.79 and a root mean square error of 19.03 mg/m2. This work indicates the importance of taking viewing geometry effect into account when using spectral features/indices and provides new insight in the application of multi-angle remote sensing for the estimation of crop physiology.

Comparison of Cellulose Iβ Simulations with Three Carbohydrate Force Fields.

PubMed

Matthews, James F; Beckham, Gregg T; Bergenstråhle-Wohlert, Malin; Brady, John W; Himmel, Michael E; Crowley, Michael F

2012-02-14

Molecular dynamics simulations of cellulose have recently become more prevalent due to increased interest in renewable energy applications, and many atomistic and coarse-grained force fields exist that can be applied to cellulose. However, to date no systematic comparison between carbohydrate force fields has been conducted for this important system. To that end, we present a molecular dynamics simulation study of hydrated, 36-chain cellulose Iβ microfibrils at room temperature with three carbohydrate force fields (CHARMM35, GLYCAM06, and Gromos 45a4) up to the near-microsecond time scale. Our results indicate that each of these simulated microfibrils diverge from the cellulose Iβ crystal structure to varying degrees under the conditions tested. The CHARMM35 and GLYCAM06 force fields eventually result in structures similar to those observed at 500 K with the same force fields, which are consistent with the experimentally observed high-temperature behavior of cellulose I. The third force field, Gromos 45a4, produces behavior significantly different from experiment, from the other two force fields, and from previously reported simulations with this force field using shorter simulation times and constrained periodic boundary conditions. For the GLYCAM06 force field, initial hydrogen-bond conformations and choice of electrostatic scaling factors significantly affect the rate of structural divergence. Our results suggest dramatically different time scales for convergence of properties of interest, which is important in the design of computational studies and comparisons to experimental data. This study highlights that further experimental and theoretical work is required to understand the structure of small diameter cellulose microfibrils typical of plant cellulose.

Structure of the Elastin-Contractile Units in the Thoracic Aorta and How Genes That Cause Thoracic Aortic Aneurysms and Dissections Disrupt This Structure.

PubMed

Karimi, Ashkan; Milewicz, Dianna M

2016-01-01

The medial layer of the aorta confers elasticity and strength to the aortic wall and is composed of alternating layers of smooth muscle cells (SMCs) and elastic fibres. The SMC elastin-contractile unit is a structural unit that links the elastin fibres to the SMCs and is characterized by the following: (1) layers of elastin fibres that are surrounded by microfibrils; (2) microfibrils that bind to the integrin receptors in focal adhesions on the cell surface of the SMCs; and (3) SMC contractile filaments that are linked to the focal adhesions on the inner side of the membrane. The genes that are altered to cause thoracic aortic aneurysms and aortic dissections encode proteins involved in the structure or function of the SMC elastin-contractile unit. Included in this gene list are the genes encoding protein that are structural components of elastin fibres and microfibrils, FBN1, MFAP5, ELN, and FBLN4. Also included are genes that encode structural proteins in the SMC contractile unit, including ACTA2, which encodes SMC-specific α-actin and MYH11, which encodes SMC-specific myosin heavy chain, along with MYLK and PRKG1, which encode kinases that control SMC contraction. Finally, mutations in the gene encoding the protein linking integrin receptors to the contractile filaments, FLNA, also predispose to thoracic aortic disease. Thus, these data suggest that functional SMC elastin-contractile units are important for maintaining the structural integrity of the aorta. Copyright © 2016 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.

Cell Wall Architecture of the Elongating Maize Coleoptile1

PubMed Central

Carpita, Nicholas C.; Defernez, Marianne; Findlay, Kim; Wells, Brian; Shoue, Douglas A.; Catchpole, Gareth; Wilson, Reginald H.; McCann, Maureen C.

2001-01-01

The primary walls of grasses are composed of cellulose microfibrils, glucuronoarabinoxylans (GAXs), and mixed-linkage β-glucans, together with smaller amounts of xyloglucans, glucomannans, pectins, and a network of polyphenolic substances. Chemical imaging by Fourier transform infrared microspectroscopy revealed large differences in the distributions of many chemical species between different tissues of the maize (Zea mays) coleoptile. This was confirmed by chemical analyses of isolated outer epidermal tissues compared with mesophyll-enriched preparations. Glucomannans and esterified uronic acids were more abundant in the epidermis, whereas β-glucans were more abundant in the mesophyll cells. The localization of β-glucan was confirmed by immunocytochemistry in the electron microscope and quantitative biochemical assays. We used field emission scanning electron microscopy, infrared microspectroscopy, and biochemical characterization of sequentially extracted polymers to further characterize the cell wall architecture of the epidermis. Oxidation of the phenolic network followed by dilute NaOH extraction widened the pores of the wall substantially and permitted observation by scanning electron microscopy of up to six distinct microfibrillar lamellae. Sequential chemical extraction of specific polysaccharides together with enzymic digestion of β-glucans allowed us to distinguish two distinct domains in the grass primary wall. First, a β-glucan-enriched domain, coextensive with GAXs of low degrees of arabinosyl substitution and glucomannans, is tightly associated around microfibrils. Second, a GAX that is more highly substituted with arabinosyl residues and additional glucomannan provides an interstitial domain that interconnects the β-glucan-coated microfibrils. Implications for current models that attempt to explain the biochemical and biophysical mechanism of wall loosening during cell growth are discussed. PMID:11598229

Microenvironmental Regulation by Fibrillin-1

PubMed Central

Sengle, Gerhard; Tsutsui, Ko; Keene, Douglas R.; Tufa, Sara F.; Carlson, Eric J.; Charbonneau, Noe L.; Ono, Robert N.; Sasaki, Takako; Wirtz, Mary K.; Samples, John R.; Fessler, Liselotte I.; Fessler, John H.; Sekiguchi, Kiyotoshi; Hayflick, Susan J.; Sakai, Lynn Y.

2012-01-01

Fibrillin-1 is a ubiquitous extracellular matrix molecule that sequesters latent growth factor complexes. A role for fibrillin-1 in specifying tissue microenvironments has not been elucidated, even though the concept that fibrillin-1 provides extracellular control of growth factor signaling is currently appreciated. Mutations in FBN1 are mainly responsible for the Marfan syndrome (MFS), recognized by its pleiotropic clinical features including tall stature and arachnodactyly, aortic dilatation and dissection, and ectopia lentis. Each of the many different mutations in FBN1 known to cause MFS must lead to similar clinical features through common mechanisms, proceeding principally through the activation of TGFβ signaling. Here we show that a novel FBN1 mutation in a family with Weill-Marchesani syndrome (WMS) causes thick skin, short stature, and brachydactyly when replicated in mice. WMS mice confirm that this mutation does not cause MFS. The mutation deletes three domains in fibrillin-1, abolishing a binding site utilized by ADAMTSLIKE-2, -3, -6, and papilin. Our results place these ADAMTSLIKE proteins in a molecular pathway involving fibrillin-1 and ADAMTS-10. Investigations of microfibril ultrastructure in WMS humans and mice demonstrate that modulation of the fibrillin microfibril scaffold can influence local tissue microenvironments and link fibrillin-1 function to skin homeostasis and the regulation of dermal collagen production. Hence, pathogenetic mechanisms caused by dysregulated WMS microenvironments diverge from Marfan pathogenetic mechanisms, which lead to broad activation of TGFβ signaling in multiple tissues. We conclude that local tissue-specific microenvironments, affected in WMS, are maintained by a fibrillin-1 microfibril scaffold, modulated by ADAMTSLIKE proteins in concert with ADAMTS enzymes. PMID:22242013

Ocular Phenotype of Fbn2-Null Mice

PubMed Central

Shi, Yanrong; Tu, Yidong; Mecham, Robert P.; Bassnett, Steven

2013-01-01

Purpose. Fibrillin-2 (Fbn2) is the dominant fibrillin isoform expressed during development of the mouse eye. To test its role in morphogenesis, we examined the ocular phenotype of Fbn2−/− mice. Methods. Ocular morphology was assessed by confocal microscopy using antibodies against microfibril components. Results. Fbn2−/− mice had a high incidence of anterior segment dysgenesis. The iris was the most commonly affected tissue. Complete iridal coloboma was present in 37% of eyes. Dyscoria, corectopia and pseudopolycoria were also common (43% combined incidence). In wild-type (WT) mice, fibrillin-2-rich microfibrils are prominent in the pupillary membrane (PM) during development. In Fbn2-null mice, the absence of Fbn2 was partially compensated for by increased expression of fibrillin-1, although the resulting PM microfibrils were disorganized, compared with WTs. In colobomatous adult Fbn2−/− eyes, the PM failed to regress normally, especially beneath the notched region of the iris. Segments of the ciliary body were hypoplastic, and zonular fibers, although relatively plentiful, were unevenly distributed around the lens equator. In regions where the zonular fibers were particularly disturbed, the synchronous differentiation of the underlying lens fiber cells was affected. Conclusions. Fbn2 has an indispensable role in ocular morphogenesis in mice. The high incidence of iris coloboma in Fbn2-null animals implies a previously unsuspected role in optic fissure closure. The observation that fiber cell differentiation was disturbed in Fbn2−/− mice raises the possibility that the attachment of zonular fibers to the lens surface may help specify the equatorial margin of the lens epithelium. PMID:24130178

Nondestructive hydrogen analysis of steam-oxidized Zircaloy-4 by wide-angle neutron scattering

NASA Astrophysics Data System (ADS)

Yan, Yong; Qian, Shuo; Garrison, Ben; Smith, Tyler; Kim, Peter

2018-04-01

A nondestructive neutron scattering method to precisely measure the hydrogen content in high-temperature steam-oxidized Zircaloy-4 cladding was developed. Zircaloy-4 cladding was used to produce hydrided specimens with hydrogen content up to ≈500 wppm. Following hydrogen charging, the hydrogen content of the hydrided specimens was measured using the vacuum hot extraction method, by which the samples with desired hydrogen concentrations were selected for the neutron study. The hydrided samples were then oxidized in steam up to ≈6.0 wt. % at 1100 °C. Optical microscopy shows that our hydriding procedure results in uniform distribution of circumferential hydrides across the wall thickness, and uniform oxide layers were formed on the sample surfaces by the steam oxidation. Small- and wide-angle neutron scattering were simultaneously performed to provide a quick (less than an hour per sample) measurement of the hydrogen content in various types of hydrided and oxidized Zircaloy-4. Our study demonstrates that the hydrogen in pre-oxidized Zircaloy-4 cladding can be measured very accurately by both small- and wide-angle neutron scattering. For steam-oxidized samples, the small-angle neutron scattering is contaminated with coherent scattering from additional structural features induced by the steam oxidation. However, the scattering intensity of the wide-angle neutron scattering increases proportionally with the hydrogen charged in the samples. The hydrogen content and wide-angle neutron scattering intensity are highly linearly correlated for the oxidized cladding samples examined in this work, and can be used to precisely determine the hydrogen content in steam-oxidized Zircaloy-4 samples. Hydrogen contents determined by neutron scattering of oxidation samples were also found to be consistent with the results of chemical analysis within acceptable margins for error.

Nondestructive hydrogen analysis of steam-oxidized Zircaloy-4 by wide-angle neutron scattering

DOE PAGES

Yan, Yong; Qian, Shuo; Garrison, Ben; ...

2018-04-15

In this study, a nondestructive neutron scattering method to precisely measure the hydrogen content in high-temperature steam-oxidized Zircaloy-4 cladding was developed. Zircaloy-4 cladding was used to produce hydrided specimens with hydrogen content up to ≈500 wppm. Following hydrogen charging, the hydrogen content of the hydrided specimens was measured using the vacuum hot extraction method, by which the samples with desired hydrogen concentrations were selected for the neutron study. The hydrided samples were then oxidized in steam up to ≈6.0wt. % at 1100°C. Optical microscopy shows that our hydriding procedure results in uniform distribution of circumferential hydrides across the wall thickness,more » and uniform oxide layers were formed on the sample surfaces by the steam oxidation. Small- and wide-angle neutron scattering were simultaneously performed to provide a quick (less than an hour per sample) measurement of the hydrogen content in various types of hydrided and oxidized Zircaloy-4. Our study demonstrates that the hydrogen in pre-oxidized Zircaloy-4 cladding can be measured very accurately by both small- and wide-angle neutron scattering. For steam-oxidized samples, the small-angle neutron scattering is contaminated with coherent scattering from additional structural features induced by the steam oxidation. However, the scattering intensity of the wide-angle neutron scattering increases proportionally with the hydrogen charged in the samples. The hydrogen content and wide-angle neutron scattering intensity are highly linearly correlated for the oxidized cladding samples examined in this work, and can be used to precisely determine the hydrogen content in steam-oxidized Zircaloy-4 samples. Hydrogen contents determined by neutron scattering of oxidation samples were also found to be consistent with the results of chemical analysis within acceptable margins for error.« less

Nondestructive hydrogen analysis of steam-oxidized Zircaloy-4 by wide-angle neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Yong; Qian, Shuo; Garrison, Ben

In this study, a nondestructive neutron scattering method to precisely measure the hydrogen content in high-temperature steam-oxidized Zircaloy-4 cladding was developed. Zircaloy-4 cladding was used to produce hydrided specimens with hydrogen content up to ≈500 wppm. Following hydrogen charging, the hydrogen content of the hydrided specimens was measured using the vacuum hot extraction method, by which the samples with desired hydrogen concentrations were selected for the neutron study. The hydrided samples were then oxidized in steam up to ≈6.0wt. % at 1100°C. Optical microscopy shows that our hydriding procedure results in uniform distribution of circumferential hydrides across the wall thickness,more » and uniform oxide layers were formed on the sample surfaces by the steam oxidation. Small- and wide-angle neutron scattering were simultaneously performed to provide a quick (less than an hour per sample) measurement of the hydrogen content in various types of hydrided and oxidized Zircaloy-4. Our study demonstrates that the hydrogen in pre-oxidized Zircaloy-4 cladding can be measured very accurately by both small- and wide-angle neutron scattering. For steam-oxidized samples, the small-angle neutron scattering is contaminated with coherent scattering from additional structural features induced by the steam oxidation. However, the scattering intensity of the wide-angle neutron scattering increases proportionally with the hydrogen charged in the samples. The hydrogen content and wide-angle neutron scattering intensity are highly linearly correlated for the oxidized cladding samples examined in this work, and can be used to precisely determine the hydrogen content in steam-oxidized Zircaloy-4 samples. Hydrogen contents determined by neutron scattering of oxidation samples were also found to be consistent with the results of chemical analysis within acceptable margins for error.« less

The Hygroscopic Nature of Wood,

DTIC Science & Technology

The cell walls of wood are organized as a structural system involving filamentous microfibrils , oriented essentially in the direction of the...longitudinal axis embedded in an amorphous matrix of noncrystalline cellulose , hemicelluloses, and lignin. The molecules in the amorphous regions, primarily

From nano- to micrometer scale: the role of microwave-assisted acid and alkali pretreatments in the sugarcane biomass structure.

PubMed

Isaac, Augusta; de Paula, Jéssica; Viana, Carlos Martins; Henriques, Andréia Bicalho; Malachias, Angelo; Montoro, Luciano A

2018-01-01

To date, great strides have been made in elucidating the role of thermochemical pretreatments in the chemical and structural features of plant cell walls; however, there is no clear picture of the plant recalcitrance and its relationship to deconstruction. Previous studies precluded full answers due to the challenge of multiscale features of plant cell wall organization. Complementing the previous efforts, we undertook a systematic, multiscale, and integrated approach to track the effect of microwave-assisted H 2 SO 4 and NaOH treatments on the hierarchical structure of plants, i.e., from a nano- to micrometer scale. We focused on the investigation of the highly recalcitrant sclerenchyma cell walls from sugarcane bagasse. Through atomic force microscopy and X-ray diffraction analyses, remarkable details of the assembly of cellulose microfibrils not previously seen were revealed. Following the H 2 SO 4 treatment, we observed that cellulose microfibrils were almost double the width of the alkali pretreated sample at the temperature of 160 °C. Such enlargement led to a greater contact between cellulose chains, with a subsequent molecule alignment, as indicated by the X-ray diffraction (XRD) results with the conspicuous expansion of the average crystallite size. The delignification process had little effect on the local nanometer-sized arrangement of cellulose molecules. However, the rigidity and parallel alignment of cellulose microfibrils were partially degraded. The XRD analysis also agrees with these findings as evidenced by large momentum transfer vectors ( q  > 20 nm -1 ), interpreted as indicators of the long-range order of cell wall components, which were similar for all the studied samples except with application of the NaOH treatment at 160 °C. These changes were followed by the eventual swelling of the fiber cell walls. Based on an integrated approach, we presented multidimensional architectural models of cell wall deconstruction resulting from microwave-assisted pretreatments. We provided direct evidence supporting the idea that hemicellulose is the main barrier for the swelling of cellulose microfibrils, whereas lignin adds rigidity to cell walls. Our findings shed light on the design of more efficient strategies, not only for the conversion of biomass to fuels but also for the production of nanocellulose, which has great potential for several applications such as composites, rheology modifiers, and pharmaceuticals.

Food waste impact on municipal solid waste angle of internal friction.

PubMed

Cho, Young Min; Ko, Jae Hac; Chi, Liqun; Townsend, Timothy G

2011-01-01

The impact of food waste content on the municipal solid waste (MSW) friction angle was studied. Using reconstituted fresh MSW specimens with different food waste content (0%, 40%, 58%, and 80%), 48 small-scale (100-mm-diameter) direct shear tests and 12 large-scale (430 mm × 430 mm) direct shear tests were performed. A stress-controlled large-scale direct shear test device allowing approximately 170-mm sample horizontal displacement was designed and used. At both testing scales, the mobilized internal friction angle of MSW decreased considerably as food waste content increased. As food waste content increased from 0% to 40% and from 40% to 80%, the mobilized internal friction angles (estimated using the mobilized peak (ultimate) shear strengths of the small-scale direct shear tests) decreased from 39° to 31° and from 31° to 7°, respectively, while those of large-scale tests decreased from 36° to 26° and from 26° to 15°, respectively. Most friction angle measurements produced in this study fell within the range of those previously reported for MSW. Copyright © 2010 Elsevier Ltd. All rights reserved.

Functional characterization of two distinct xyoglucanases from rumenal microbes

USDA-ARS?s Scientific Manuscript database

Xyloglucans are known to function by binding to cellulose microfibrils, crosslinking adjacent fibers forming cellulose-XG networks important for modulation of rigidity and extensibility of the primary cell wall of plants. Enzymatic hydrolysis and modification of xyloglucans has received considerabl...

Monitoring Process Streams Towards Understanding Ionic Liquid Pretreatment of Switchgrass and Corn Stover

USDA-ARS?s Scientific Manuscript database

Pretreatment of Biomass is essential for breaking apart highly ordered and crystalline plant cell walls and loosening the lignin and hemicellulose conjugation to cellulose microfibrils, thereby facilitating enzyme accessibility and adsorption and reducing cotsts of downstream saccharification proces...

A Microwave Method for Measuring Moisture Content, Density, and Grain Angle of Wood.

DTIC Science & Technology

1985-03-01

Livermore, CA 94550. James, William L; Yen , You - Hsin ; King, Ray J. A microwave method for measuring moisture content,density, and grain angle of wood...Note S FPL-0250 March 1985 Density, and Grain 8 Angle of Wood William L. James, Physicist Forest Products Laboratory, Madison, WI You -Hain Yen ... Yen . You -1tsin. Microwave electromagnetic nondestructive testing of wood in real- time. Madison. WI: Department of Electronic and Computer

Elastic microfibril distribution in the cornea: Differences between normal and keratoconic stroma.

PubMed

White, Tomas L; Lewis, Philip N; Young, Robert D; Kitazawa, Koji; Inatomi, Tsutomu; Kinoshita, Shigeru; Meek, Keith M

2017-06-01

The optical and biomechanical properties of the cornea are largely governed by the collagen-rich stroma, a layer that represents approximately 90% of the total thickness. Within the stroma, the specific arrangement of superimposed lamellae provides the tissue with tensile strength, whilst the spatial arrangement of individual collagen fibrils within the lamellae confers transparency. In keratoconus, this precise stromal arrangement is lost, resulting in ectasia and visual impairment. In the normal cornea, we previously characterised the three-dimensional arrangement of an elastic fiber network spanning the posterior stroma from limbus-to-limbus. In the peripheral cornea/limbus there are elastin-containing sheets or broad fibers, most of which become microfibril bundles (MBs) with little or no elastin component when reaching the central cornea. The purpose of the current study was to compare this network with the elastic fiber distribution in post-surgical keratoconic corneal buttons, using serial block face scanning electron microscopy and transmission electron microscopy. We have demonstrated that the MB distribution is very different in keratoconus. MBs are absent from a region of stroma anterior to Descemet's membrane, an area that is densely populated in normal cornea, whilst being concentrated below the epithelium, an area in which they are absent in normal cornea. We contend that these latter microfibrils are produced as a biomechanical response to provide additional strength to the anterior stroma in order to prevent tissue rupture at the apex of the cone. A lack of MBs anterior to Descemet's membrane in keratoconus would alter the biomechanical properties of the tissue, potentially contributing to the pathogenesis of the disease. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Cellulose Biosynthesis: Current Views and Evolving Concepts

PubMed Central

SAXENA, INDER M.; BROWN, R. MALCOLM

2005-01-01

• Aims To outline the current state of knowledge and discuss the evolution of various viewpoints put forth to explain the mechanism of cellulose biosynthesis. • Scope Understanding the mechanism of cellulose biosynthesis is one of the major challenges in plant biology. The simplicity in the chemical structure of cellulose belies the complexities that are associated with the synthesis and assembly of this polysaccharide. Assembly of cellulose microfibrils in most organisms is visualized as a multi-step process involving a number of proteins with the key protein being the cellulose synthase catalytic sub-unit. Although genes encoding this protein have been identified in almost all cellulose synthesizing organisms, it has been a challenge in general, and more specifically in vascular plants, to demonstrate cellulose synthase activity in vitro. The assembly of glucan chains into cellulose microfibrils of specific dimensions, viewed as a spontaneous process, necessitates the assembly of synthesizing sites unique to most groups of organisms. The steps of polymerization (requiring the specific arrangement and activity of the cellulose synthase catalytic sub-units) and crystallization (directed self-assembly of glucan chains) are certainly interlinked in the formation of cellulose microfibrils. Mutants affected in cellulose biosynthesis have been identified in vascular plants. Studies on these mutants and herbicide-treated plants suggest an interesting link between the steps of polymerization and crystallization during cellulose biosynthesis. • Conclusions With the identification of a large number of genes encoding cellulose synthases and cellulose synthase-like proteins in vascular plants and the supposed role of a number of other proteins in cellulose biosynthesis, a complete understanding of this process will necessitate a wider variety of research tools and approaches than was thought to be required a few years back. PMID:15894551

Brittle Culm1, a COBRA-Like Protein, Functions in Cellulose Assembly through Binding Cellulose Microfibrils

PubMed Central

Zhang, Baocai; Liu, Xiangling; Yan, Meixian; Zhang, Lanjun; Shi, Yanyun; Zhang, Mu; Qian, Qian; Li, Jiayang; Zhou, Yihua

2013-01-01

Cellulose represents the most abundant biopolymer in nature and has great economic importance. Cellulose chains pack laterally into crystalline forms, stacking into a complicated crystallographic structure. However, the mechanism of cellulose crystallization is poorly understood. Here, via functional characterization, we report that Brittle Culm1 (BC1), a COBRA-like protein in rice, modifies cellulose crystallinity. BC1 was demonstrated to be a glycosylphosphatidylinositol (GPI) anchored protein and can be released into cell walls by removal of the GPI anchor. BC1 possesses a carbohydrate-binding module (CBM) at its N-terminus. In vitro binding assays showed that this CBM interacts specifically with crystalline cellulose, and several aromatic residues in this domain are essential for binding. It was further demonstrated that cell wall-localized BC1 via the CBM and GPI anchor is one functional form of BC1. X-ray diffraction (XRD) assays revealed that mutations in BC1 and knockdown of BC1 expression decrease the crystallite width of cellulose; overexpression of BC1 and the CBM-mutated BC1s caused varied crystallinity with results that were consistent with the in vitro binding assay. Moreover, interaction between the CBM and cellulose microfibrils was largely repressed when the cell wall residues were pre-stained with two cellulose dyes. Treating wild-type and bc1 seedlings with the dyes resulted in insensitive root growth responses in bc1 plants. Combined with the evidence that BC1 and three secondary wall cellulose synthases (CESAs) function in different steps of cellulose production as revealed by genetic analysis, we conclude that BC1 modulates cellulose assembly by interacting with cellulose and affecting microfibril crystallinity. PMID:23990797

Brittle Culm1, a COBRA-like protein, functions in cellulose assembly through binding cellulose microfibrils.

PubMed

Liu, Lifeng; Shang-Guan, Keke; Zhang, Baocai; Liu, Xiangling; Yan, Meixian; Zhang, Lanjun; Shi, Yanyun; Zhang, Mu; Qian, Qian; Li, Jiayang; Zhou, Yihua

2013-01-01

Cellulose represents the most abundant biopolymer in nature and has great economic importance. Cellulose chains pack laterally into crystalline forms, stacking into a complicated crystallographic structure. However, the mechanism of cellulose crystallization is poorly understood. Here, via functional characterization, we report that Brittle Culm1 (BC1), a COBRA-like protein in rice, modifies cellulose crystallinity. BC1 was demonstrated to be a glycosylphosphatidylinositol (GPI) anchored protein and can be released into cell walls by removal of the GPI anchor. BC1 possesses a carbohydrate-binding module (CBM) at its N-terminus. In vitro binding assays showed that this CBM interacts specifically with crystalline cellulose, and several aromatic residues in this domain are essential for binding. It was further demonstrated that cell wall-localized BC1 via the CBM and GPI anchor is one functional form of BC1. X-ray diffraction (XRD) assays revealed that mutations in BC1 and knockdown of BC1 expression decrease the crystallite width of cellulose; overexpression of BC1 and the CBM-mutated BC1s caused varied crystallinity with results that were consistent with the in vitro binding assay. Moreover, interaction between the CBM and cellulose microfibrils was largely repressed when the cell wall residues were pre-stained with two cellulose dyes. Treating wild-type and bc1 seedlings with the dyes resulted in insensitive root growth responses in bc1 plants. Combined with the evidence that BC1 and three secondary wall cellulose synthases (CESAs) function in different steps of cellulose production as revealed by genetic analysis, we conclude that BC1 modulates cellulose assembly by interacting with cellulose and affecting microfibril crystallinity.

Cellulose biosynthesis: current views and evolving concepts.

PubMed

Saxena, Inder M; Brown, R Malcolm

2005-07-01

To outline the current state of knowledge and discuss the evolution of various viewpoints put forth to explain the mechanism of cellulose biosynthesis. * Understanding the mechanism of cellulose biosynthesis is one of the major challenges in plant biology. The simplicity in the chemical structure of cellulose belies the complexities that are associated with the synthesis and assembly of this polysaccharide. Assembly of cellulose microfibrils in most organisms is visualized as a multi-step process involving a number of proteins with the key protein being the cellulose synthase catalytic sub-unit. Although genes encoding this protein have been identified in almost all cellulose synthesizing organisms, it has been a challenge in general, and more specifically in vascular plants, to demonstrate cellulose synthase activity in vitro. The assembly of glucan chains into cellulose microfibrils of specific dimensions, viewed as a spontaneous process, necessitates the assembly of synthesizing sites unique to most groups of organisms. The steps of polymerization (requiring the specific arrangement and activity of the cellulose synthase catalytic sub-units) and crystallization (directed self-assembly of glucan chains) are certainly interlinked in the formation of cellulose microfibrils. Mutants affected in cellulose biosynthesis have been identified in vascular plants. Studies on these mutants and herbicide-treated plants suggest an interesting link between the steps of polymerization and crystallization during cellulose biosynthesis. * With the identification of a large number of genes encoding cellulose synthases and cellulose synthase-like proteins in vascular plants and the supposed role of a number of other proteins in cellulose biosynthesis, a complete understanding of this process will necessitate a wider variety of research tools and approaches than was thought to be required a few years back.

Xylem development and cell wall changes of soybean seedlings grown in space.

PubMed

de Micco, Veronica; Aronne, Giovanna; Joseleau, Jean-Paul; Ruel, Katia

2008-04-01

Plants growing in altered gravity conditions encounter changes in vascular development and cell wall deposition. The aim of this study was to investigate xylem anatomy and arrangement of cellulose microfibrils in vessel walls of different organs of soybean seedlings grown in Space. Seeds germinated and seedlings grew for 5 d in Space during the Foton-M2 mission. The environmental conditions, other than gravity, of the ground control repeated those experienced in orbit. The seedlings developed in space were compared with those of the control test on the basis of numerous anatomical and ultrastructural parameters such as number of veins, size and shape of vessel lumens, thickness of cell walls and deposition of cellulose microfibrils. Observations made with light, fluorescence and transmission electron microscopy, together with the quantification of the structural features through digital image analysis, showed that the alterations due to microgravity do not occur at the same level in the various organs of soybean seedlings. The modifications induced by microgravity or by the indirect effect of space-flight conditions, became conspicuous only in developing vessels at the ultrastructural level. The results suggested that the orientation of microfibrils and their assembly in developing vessels are perturbed by microgravity at the beginning of wall deposition, while they are still able to orient and arrange in thicker and ordered structures at later stages of secondary wall deposition. The process of proper cell-wall building, although not prevented, is perturbed in Space at the early stage of development. This would explain the almost unaltered anatomy of mature structures, accompanied by a slower growth observed in seedlings grown in Space than on Earth.

Liquid crystal-type assembly of native cellulose-glucuronoxylans extracted from plant cell wall.

PubMed

Reis, D; Vian, B; Chanzy, H; Roland, J C

1991-01-01

In numerous plant cell walls, the cellulose microfibrils are arranged in a helicoidal pattern which has been considered as an analog to a cholesteric order. Here, we report on the spontaneous helicoidal organization which occurs in acellular conditions from aqueous suspensions of cellulose. The cellulosic mucilage of mature seeds of quince (Cydonia oblonga L) was studied both in situ (pre-release mucilage) and after water extraction and in in vitro re-assembly (prolonged high speed ultracentrifugation, further progressive dehydration and embedding in LR White methacrylate or hydrosoluble melamine resin). The cellulosic component was characterized by the use of cellobiohydrolase (CBH1) bound to colloidal gold, and the glucuronic acid residues of the xylan matrix were characterized by the use of cationised gold. Inside the seeds, the pre-release mucilage is mostly helicoidal, with the occurrence of more or less ordered domains, which indicate a fluid organization relevant to an actual liquid crystal state. Cytochemical tests revealed the tight association between cellulose and glucuronoxylans, the latter constituting a charged coat around each microfibril. Following the hydration of the seed, a cellulosic suspension was extracted in which microfibrils were totally dispersed. The progressive dehydration of the suspension gave rise to concentrated viscous drops. Ultrastructural observations revealed the occurrence of multidomain organization, from non-ordered to cholesteric-like regions, revealing that the mucilage is at the same time crystalline and liquid. This constitutes the first demonstration that liquid crystal type assemblies can arise from crystalline and biological cellulose in aqueous suspension. It strengthens the hypothesis that a transient liquid crystal state must occur during the cellulose ordering. The possible morphogenetic role of the glucuronoxylans in the cholesteric organization of the cellulose is discussed.

Xylem Development and Cell Wall Changes of Soybean Seedlings Grown in Space

PubMed Central

de Micco, Veronica; Aronne, Giovanna; Joseleau, Jean-Paul; Ruel, Katia

2008-01-01

Background and Aims Plants growing in altered gravity conditions encounter changes in vascular development and cell wall deposition. The aim of this study was to investigate xylem anatomy and arrangement of cellulose microfibrils in vessel walls of different organs of soybean seedlings grown in Space. Methods Seeds germinated and seedlings grew for 5 d in Space during the Foton-M2 mission. The environmental conditions, other than gravity, of the ground control repeated those experienced in orbit. The seedlings developed in space were compared with those of the control test on the basis of numerous anatomical and ultrastructural parameters such as number of veins, size and shape of vessel lumens, thickness of cell walls and deposition of cellulose microfibrils. Key Results Observations made with light, fluorescence and transmission electron microscopy, together with the quantification of the structural features through digital image analysis, showed that the alterations due to microgravity do not occur at the same level in the various organs of soybean seedlings. The modifications induced by microgravity or by the indirect effect of space-flight conditions, became conspicuous only in developing vessels at the ultrastructural level. The results suggested that the orientation of microfibrils and their assembly in developing vessels are perturbed by microgravity at the beginning of wall deposition, while they are still able to orient and arrange in thicker and ordered structures at later stages of secondary wall deposition. Conclusions The process of proper cell-wall building, although not prevented, is perturbed in Space at the early stage of development. This would explain the almost unaltered anatomy of mature structures, accompanied by a slower growth observed in seedlings grown in Space than on Earth. PMID:18252765

Effects of high-speed homogenization and high-pressure homogenization on structure of tomato residue fibers.

PubMed

Hua, Xiao; Xu, Shanan; Wang, Mingming; Chen, Ying; Yang, Hui; Yang, Ruijin

2017-10-01

Tomato residue fibers obtained after derosination and deproteinization were processed by high-speed homogenization (HSH) and high-pressure homogenization (HPH), and their effects on fiber structure was investigated, respectively. Characterizations including particle size distribution, SEM, TEM and XRD were performed. HSH could break raw fibers to small particles of around 60μm, while HPH could reshape fibers to build network structure. Microfibrils were released and their nanostructure consisting of elementary fibrils was observed by TEM. XRD patterns indicated both HSH and HPH could hardly alter the nanostructure of the fibers. Physicochemical properties including expansibility, WHC and OHC were determined. Both HSH and HPH could increase the soluble fiber content by about 8%, but HSH-HPH combined processing did not show better result. Acid (4mol/L HCl) was used in replacement of water medium and the acidic degradation of fibers could be promoted by high speed shearing or high pressure processing. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nanocomposites of natural rubber and polyaniline-modified cellulose nanofibrils

USDA-ARS?s Scientific Manuscript database

Cellulose nanofibrils (CNF) were isolated from cotton microfibrils (CM) by acid hydrolysis and coated with polyaniline (PANI) by in situ polymerization of aniline onto CNF in the presence of hydrochloride acid and ammonium peroxydisulfate to produce CNF/PANI. Nanocomposites of natural rubber (NR) re...

Gas-phase surface esterification of cellulose microfibrils and whiskers.

PubMed

Berlioz, Sophie; Molina-Boisseau, Sonia; Nishiyama, Yoshiharu; Heux, Laurent

2009-08-10

A new and highly efficient synthetic method has been developed for the surface esterification of model cellulosic substrates of high crystallinity and accessibility, namely, freeze-dried tunicin whiskers and bacterial cellulose microfibrils dried by the critical point method. The reaction, which is based on the gas-phase action of palmitoyl chloride, was monitored by solid-state CP-MAS (13)C NMR. It was found that the grafting density not only depended on the experimental conditions, but also on the nature and conditioning of the cellulose samples. The structural and morphological modifications of the substrates at various degrees of grafting were revealed by scanning electron microscopy and X-ray diffraction analysis. These characterizations indicated that the esterification proceeded from the surface of the substrate to their crystalline core. Hence, for moderate degree of substitution, the surface was fully grafted whereas the cellulose core remained unmodified and the original fibrous morphology maintained. An almost total esterification could be achieved under certain conditions, leading to highly substituted cellulose esters, presenting characteristic X-ray diffraction patterns.

Cellulose whiskers versus microfibrils: influence of the nature of the nanoparticle and its surface functionalization on the thermal and mechanical properties of nanocomposites.

PubMed

Siqueira, Gilberto; Bras, Julien; Dufresne, Alain

2009-02-09

In the present work, nanowhiskers and microfibrillated cellulose (MFC) both extracted from sisal were used to reinforce polycaprolactone (PCL). We report the influence of the nanoparticle's nature on the mechanical and thermal properties of the ensuing nanocomposites. The surface of both the nanoparticles was chemically modified to improve their compatibilization with the polymeric matrix. N-Octadecyl isocyanate (C18H37NCO) was used as the grafting agent. PCL nanocomposite films reinforced with sisal whiskers or MFC (raw or chemically modified) were prepared by film casting. The thermal behavior (Tg, Tm, Tc, and degree of crystallinity) and the mechanical properties of the nanocomposites in both the linear and the nonlinear range were determined using differential scanning calorimetry (DSC), dynamical mechanical analysis (DMA), and tensile tests, respectively. Significant differences were reported according to the nature of the nanoparticle and amount of nanofillers used as reinforcement. It was also proved that the chemical treatment clearly improves the ultimate properties of the nanocomposites.

Polymer mobility in cell walls of cucumber hypocotyls

NASA Technical Reports Server (NTRS)

Fenwick, K. M.; Apperley, D. C.; Cosgrove, D. J.; Jarvis, M. C.

1999-01-01

Cell walls were prepared from the growing region of cucumber (Cucumis sativus) hypocotyls and examined by solid-state 13C NMR spectroscopy, in both enzymically active and inactivated states. The rigidity of individual polymer segments within the hydrated cell walls was assessed from the proton magnetic relaxation parameter, T2, and from the kinetics of cross-polarisation from 1H to 13C. The microfibrils, including most of the xyloglucan in the cell wall, as well as cellulose, behaved as very rigid solids. A minor xyloglucan fraction, which may correspond to cross-links between microfibrils, shared a lower level of rigidity with some of the pectic galacturonan. Other pectins, including most of the galactan side-chain residues of rhamnogalacturonan I, were much more mobile and behaved in a manner intermediate between the solid and liquid states. The only difference observed between the enzymically active and inactive cell walls, was the loss of a highly mobile, methyl-esterified galacturonan fraction, as the result of pectinesterase activity.

Microfibrillated cellulose - its barrier properties and applications in cellulosic materials: a review.

PubMed

Lavoine, Nathalie; Desloges, Isabelle; Dufresne, Alain; Bras, Julien

2012-10-01

Interest in microfibrillated cellulose (MFC) has been increasing exponentially. During the last decade, this bio-based nanomaterial was essentially used in nanocomposites for its reinforcement property. Its nano-scale dimensions and its ability to form a strong entangled nanoporous network, however, have encouraged the emergence of new high-value applications. In previous years, its mode of production has completely changed, as many forms of optimization have been developed. New sources, new mechanical processes, and new pre- and post-treatments are currently under development to reduce the high energy consumption and produce new types of MFC materials on an industrial scale. The nanoscale characterization possibilities of different MFC materials are thus increasing intensively. Therefore, it is critical to review such MFC materials and their properties. Moreover, very recent studies have proved the significant barrier properties of MFC. Hence, it is proposed to focus on the barrier properties of MFC used in films, in nanocomposites, or in paper coating. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effects of bagasse microfibrillated cellulose and cationic polyacrylamide on key properties of bagasse paper.

PubMed

Djafari Petroudy, Seyed Rahman; Syverud, Kristin; Chinga-Carrasco, Gary; Ghasemain, Ali; Resalati, Hossein

2014-01-01

This study explores the benefits of using bagasse microfibrillated cellulose (MFC) in bagasse paper. Two different types of MFC were produced from DED bleached soda bagasse pulp. The MFC was added to soda bagasse pulp furnishes in different amounts. Cationic polyacrylamide (C-PAM) was selected as retention aid. The results show that addition of MFC increased the strength of paper as expected. Interestingly, 1% MFC in combination with 0.1% C-PAM yielded similar drainage time as the reference pulp, which did not contain MFC. In addition, the samples containing 1% MFC and 0.1% C-PAM yielded (i) a significant increment of the tensile index, (ii) a minor decrease of opacity and (iii) preserved Gurley porosity. Hence, this study proves that small fractions of MFC in combination with adequate retention aids can have positive effects with respect to paper properties, which is most interesting from an industrial point of view. Copyright © 2013 Elsevier Ltd. All rights reserved.

The solvation structures of cellulose microfibrils in ionic liquids.

PubMed

Mostofian, Barmak; Smith, Jeremy C; Cheng, Xiaolin

2011-12-01

The use of ionic liquids for non-derivatized cellulose dissolution promises an alternative method for the thermochemical pretreatment of biomass that may be more efficient and environmentally acceptable than more conventional techniques in aqueous solution. Here, we performed equilibrium MD simulations of a cellulose microfibril in the ionic liquid 1-butyl-3-methylimidazolium chloride (BmimCl) and compared the solute structure and the solute-solvent interactions at the interface with those from corresponding simulations in water. The results indicate a higher occurrence of solvent-exposed orientations of cellulose surface hydroxymethyl groups in BmimCl than in water. Moreover, spatial and radial distribution functions indicate that hydrophilic surfaces are a preferred site of interaction between cellulose and the ionic liquid. In particular, hydroxymethyl groups on the hydrophilic fiber surface adopt a different conformation from their counterparts oriented towards the fiber's core. Furthermore, the glucose units with these solvent-oriented hydroxymethyls are surrounded by the heterocyclic organic cation in a preferred parallel orientation, suggesting a direct and distinct interaction scheme between cellulose and BmimCl.

Stress transfer and matrix-cohesive fracture mechanism in microfibrillated cellulose-gelatin nanocomposite films.

PubMed

Quero, Franck; Padilla, Cristina; Campos, Vanessa; Luengo, Jorge; Caballero, Leonardo; Melo, Francisco; Li, Qiang; Eichhorn, Stephen J; Enrione, Javier

2018-09-01

Microfibrillated cellulose (MFC) obtained from eucalyptus was embedded in gelatin from two sources; namely bovine and salmon gelatin. Raman spectroscopy revealed that stress is transferred more efficiently from bovine gelatin to the MFC when compared to salmon gelatin. Young's modulus, tensile strength, strain at failure and work of fracture of the nanocomposite films were improved by ∼67, 131, 43 y 243% respectively when using salmon gelatin as matrix material instead of bovine gelatin. Imaging of the tensile fracture surface of the MFC-gelatin nanocomposites revealed that crack formation occurs predominantly within bovine and salmon gelatin matrices rather than within the MFC or at the MFC/gelatin interface. This suggests that the mechanical failure mechanism in these nanocomposite materials is predominantly governed by a matrix-cohesive fracture mechanism. Both strength and flexibility are desirable properties for composite coatings made from gelatin-based materials, and so the findings of this study could assist in their utilization in the food and pharmaceutical industry. Copyright © 2018 Elsevier Ltd. All rights reserved.

Cellulose Aggregation under Hydrothermal Pretreatment Conditions.

PubMed

Silveira, Rodrigo L; Stoyanov, Stanislav R; Kovalenko, Andriy; Skaf, Munir S

2016-08-08

Cellulose, the most abundant biopolymer on Earth, represents a resource for sustainable production of biofuels. Thermochemical treatments make lignocellulosic biomaterials more amenable to depolymerization by exposing cellulose microfibrils to enzymatic or chemical attacks. In such treatments, the solvent plays fundamental roles in biomass modification, but the molecular events underlying these changes are still poorly understood. Here, the 3D-RISM-KH molecular theory of solvation has been employed to analyze the role of water in cellulose aggregation under different thermodynamic conditions. The results show that, under ambient conditions, highly structured hydration shells around cellulose create repulsive forces that protect cellulose microfibrils from aggregating. Under hydrothermal pretreatment conditions, however, the hydration shells lose structure, and cellulose aggregation is favored. These effects are largely due to a decrease in cellulose-water interactions relative to those at ambient conditions, so that cellulose-cellulose attractive interactions become prevalent. Our results provide an explanation to the observed increase in the lateral size of cellulose crystallites when biomass is subject to pretreatments and deepen the current understanding of the mechanisms of biomass modification.

Mice lacking the extracellular matrix protein MAGP1 display delayed thrombotic occlusion following vessel injury

PubMed Central

Werneck, Claudio C.; Vicente, Cristina P.; Weinberg, Justin S.; Shifren, Adrian; Pierce, Richard A.; Broekelmann, Thomas J.; Tollefsen, Douglas M.

2008-01-01

Mice lacking the extracellular matrix protein microfibril-associated glycoprotein-1 (MAGP1) display delayed thrombotic occlusion of the carotid artery following injury as well as prolonged bleeding from a tail vein incision. Normal occlusion times were restored when recombinant MAGP1 was infused into deficient animals prior to vessel wounding. Blood coagulation was normal in these animals as assessed by activated partial thromboplastin time and prothrombin time. Platelet number was lower in MAGP1-deficient mice, but the platelets showed normal aggregation properties in response to various agonists. MAGP1 was not found in normal platelets or in the plasma of wild-type mice. In ligand blot assays, MAGP1 bound to fibronectin, fibrinogen, and von Willebrand factor, but von Willebrand factor was the only protein of the 3 that bound to MAGP1 in surface plasmon resonance studies. These findings show that MAGP1, a component of microfibrils and vascular elastic fibers, plays a role in hemostasis and thrombosis. PMID:18281502

Content-based fused off-axis object illumination direct-to-digital holography

DOEpatents

Price, Jeffery R.

2006-05-02

Systems and methods are described for content-based fused off-axis illumination direct-to-digital holography. A method includes calculating an illumination angle with respect to an optical axis defined by a focusing lens as a function of data representing a Fourier analyzed spatially heterodyne hologram; reflecting a reference beam from a reference mirror at a non-normal angle; reflecting an object beam from an object the object beam incident upon the object at the illumination angle; focusing the reference beam and the object beam at a focal plane of a digital recorder to from the content-based off-axis illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis; and digitally recording the content based off-axis illuminated spatially heterodyne hologram including spatially heterodyne fringes for Fourier analysis.

The Effect of Water Molecules on Mechanical Properties of Cell Walls

NASA Astrophysics Data System (ADS)

Rahbar, Nima; Youssefian, Sina

The unique properties of bamboo fibers come from their natural composite structures that comprise mainly cellulose nanofibrils in a matrix of intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Here, we have utilized atomistic simulations to investigate the mechanical properties and mechanisms of interactions between these materials, in the presence of water molecules. The role of hemicellulose found to be enhancing the mechanical properties and lignin found to be providing the strength of bamboo fibers. The abundance of Hbonds in hemicellulose chains is responsible for improving the mechanical behavior of LCC. The strong van der Waals forces between lignin molecules and cellulose nanofibrils are responsible for higher adhesion energy between LCC/cellulose nanofibrils. We also found out that the amorphous regions of cellulose nanofibrils is the weakest interface in bamboo Microfibrils. In presence of water, the elastic modulus of lignin increases at low water content and decreases in higher water content, whereas the hemicellulose elastic modulus constantly decreases. The variations of Radial Distribution Function and Free Fractional Volume of these materials with water suggest that water molecules enhance the mechanical properties of lignin by filling voids in the system and creating Hbond bridges between polymer chains. For hemicellulose, however, the effect is always regressive due to the destructive effect of water molecules on the Hbond of its dense structure.

Effect of Multiangular Observations on Crop Chlorophyll Content Retrieval Using Field Top-Of Spectrometer Data

NASA Astrophysics Data System (ADS)

Jiao, Q.; Liu, L.; Zhang, B.

2017-12-01

Leaf chlorophyll content is an important indicator of crop growth condition that determines final crop yield. A lot of research on remote sensing of leaf chlorophyll content were based on reflectance data acquired from nadir direction. However, reflectance data at nadir may be affected by soil background. In fact, many satellite sensors with capability of chlorophyll retrieval, like the 68.5 degrees field-of-view MERIS, have produced large multiangular data. This study tries to assess the anisotropic effect on the retrieval of leaf chlorophyll content using field hyperspectral data of wheat canopy. The field multi-angle observation experiment of winter wheat was carried out in April 2017 in Xiaotangshan agriculture demonstration study site in Beijing. Field canopy spectra and leaf chlorophyll content of winter wheat were measured. The most used indices for chlorophyll content retrieval, such as CIred-edge, REP, MTCI, MCARI/OSAVI[705,750], TCARI/OSAVI[705,750], were calculated based on the filed multiangular reflectance. The ratio index TCARI/OSAVI owned the best results in estimating leaf chlorophyll content (R2 of 0.62) among all the selected indices, when using the top-of-canopy reflectance at nadir. The determination coefficient of the relationship of TCARI/OSAVI with chlorophyll content reached its peak (R2 of 0.70) at angle of 15 degrees, and the minimum R2 value of only 0.25 at angle of 60 degrees. The MTCI got the peak of determination coefficient (R2 of 0.63) at angle of 15 degrees and the minimum value (R2 of 0.57) for 60 degrees. Our results showed the MTCI could keep a more satisfactory correlation with leaf chlorophyll content of winter wheat, however the mean values of the MTCI basically decreased as the observation angle increases. This work shows the strong anisotropic effects of top-of-canopy reflectance which influences most of selected popular chlorophyll indices. If spectral index selection is proper, multiangular remote sensing could produce higher accuracy for leaf chlorophyll content retrieval than only using nadir observation. Multi-angular remote sensing has the potential of leaf chlorophyll content retrieval for diagnosis of crop nitrogen stress or water stress.

Molecular modeling approach to vegetable tanning: preliminary results for gallotannin interactions with the collagen microfibril

USDA-ARS?s Scientific Manuscript database

Tanning of animal hides produces leather, a durable, flexible material that is stabilized against putrefaction. Chrome-tanned wet blue, aldehyde crosslinked wet white, and vegetable tanned hides are major contributors to current leather production. Although the chemistries involved are significant...

Hydraulic and mechanical properties of young Norway spruce clones related to growth and wood structure

PubMed Central

ROSNER, SABINE; KLEIN, ANDREA; MÜLLER, ULRICH; KARLSSON, BO

2011-01-01

Summary Stem segments of eight five-year-old Norway spruce (Picea abies (L.) Karst.) clones differing in growth characteristics were tested for maximum specific hydraulic conductivity (ks100), vulnerability to cavitation and behavior under mechanical stress. The vulnerability of the clones to cavitation was assessed by measuring the applied air pressure required to cause 12 and 50% loss of conductivity (Ψ12, Ψ50) and the percent loss of conductivity at 4 MPa applied air pressure (PLC4MPa). The bending strength and stiffness and the axial compression strength and stiffness of the same stem segments were measured to characterize wood mechanical properties. Growth ring width, wood density, latewood percentage, lumen diameter, cell wall thickness, tracheid length and pit dimensions of earlywood cells, spiral grain and microfibril angles were examined to identify structure–function relationships. High ks100 was strongly and positively related to spiral grain angle, which corresponded positively to tracheid length and pit dimensions. Spiral grain may reduce flow resistance of the bordered pits of the first earlywood tracheids, which are characterized by rounded tips and an equal distribution of pits along the entire length. Wood density was unrelated to hydraulic vulnerability parameters. Traits associated with higher hydraulic vulnerability were long tracheids, high latewood percentage and thick earlywood cell walls. The positive relationship between earlywood cell wall thickness and vulnerability to cavitation suggest that air seeding through the margo of bordered pits may occur in earlywood. There was a positive phenotypic and genotypic relationship between ks100 and PLC4MPa, and both parameters were positively related to tree growth rate. Variability in mechanical properties depended mostly on wood density, but also on the amount of compression wood. Accordingly, hydraulic conductivity and mechanical strength or stiffness showed no tradeoff. PMID:17472942

Investigation of Plant Cell Wall Properties: A Study of Contributions from the Nanoscale to the Macroscale Impacting Cell Wall Recalcitrance

NASA Astrophysics Data System (ADS)

Crowe, Jacob Dillon

Biochemical conversion of lignocellulosic biomass to fuel ethanol is one of a few challenging, yet opportune technologies that can reduce the consumption of petroleum-derived transportation fuels, while providing parallel reductions in greenhouse gas emissions. Biomass recalcitrance, or resistance to deconstruction, is a major technical challenge that limits effective conversion of biomass to fermentable sugars, often requiring a costly thermochemical pretreatment step to improve biomass deconstruction. Biomass recalcitrance is imparted largely by the secondary cell wall, a complex polymeric matrix of cell wall polysaccharides and aromatic heteropolymers, that provides structural stability to cells and enables plant upright growth. Polymers within the cell wall can vary both compositionally and structurally depending upon plant species and anatomical fraction, and have varied responses to thermochemical pretreatments. Cell wall properties impacting recalcitrance are still not well understood, and as a result, the goal of this dissertation is to investigate structural features of the cell wall contributing to recalcitrance (1) in diverse anatomical fractions of a single species, (2) in response to diverse pretreatments, and (3) resulting from genetic modification. In the first study, feedstock cell wall heterogeneity was investigated in anatomical (stem, leaf sheaths, and leaf blades) and internode fractions of switchgrass at varying tissue maturities. Lignin content was observed as the key contributor to recalcitrance in maturing stem tissues only, with non-cellulosic substituted glucuronoarabinoxylans and pectic polysaccharides contributing to cell wall recalcitrance in leaf sheath and leaf blades. Hydroxycinnamate (i.e., saponifiable p-coumarate and ferulate) content along with xylan and pectin extractability decreased with tissue maturity, suggesting lignification is only one component imparting maturity specific cell wall recalcitrance. In the second study, alkaline hydrogen peroxide and liquid hot water pretreatments were shown to alter structural properties impacting nanoscale porosity in corn stover. Delignification by alkaline hydrogen peroxide pretreatment decreased cell wall rigidity, with subsequent cell wall swelling resulting in increased nanoscale porosity and improved enzymatic hydrolysis compared to limited swelling and increased accessible surface areas observed in liquid hot water pretreated biomass. The volume accessible to a 90 A dextran probe within the cell wall was found to be positively correlated to both enzyme binding and glucose hydrolysis yields, indicating cell wall porosity is a key contributor to effective hydrolysis yields. In the third study, the effect of altered xylan content and structure was investigated in irregular xylem (irx) Arabidopsis thaliana mutants to understand the role xylan plays in secondary cell wall development and organization. Higher xylan extractability and lower cellulose crystallinity observed in irx9 and irx15 irx15-L mutants compared to wild type indicated altered xylan integration into the secondary cell wall. Nanoscale cell wall organization observed using multiple microscopy techniques was impacted to some extent in all irx mutants, with disorganized cellulose microfibril layers in sclerenchyma secondary cell walls likely resulting from irregular xylan structure and content. Irregular secondary cell wall microfibril layers showed heterogeneous nanomechanical properties compared to wild type, which translated to mechanical deficiencies observed in stem tensile tests. These results suggest nanoscale defects in cell wall strength can correspond to macroscale phenotypes.

Effects of electrode bevel angle on argon arc properties and weld shape

NASA Astrophysics Data System (ADS)

Dong, W. C.; Lu, S. P.; Li, D. Z.; Y Li, Y.

2012-07-01

A numerical modeling of coupled welding arc with weld pool is established using FLUENT software for moving shielded GTA welding to systematically investigate the effects of electrode bevel angle on the argon arc properties as well as the weld shape on SUS304 stainless steel. The calculated results show that the argon arc is constricted and the peak values of heat flux and shear stress on the weld pool decrease with increasing electrode bevel angle, while the radial distribution of heat flux and shear stress varying slightly. The weld shape is controlled by the pool flow patterns driving by the surface tension, gas shear stress, electromagnetic force and buoyancy. The Marangoni convection induced by surface tension plays an important role on weld shapes. All the weld shapes are wide and shallow with low weld metal oxygen content, while the narrow and deep weld shapes form under high weld metal oxygen content, which is related with the oxygen concentration in the shielding gas. The weld depth/width (D/W) ratio increases with increasing electrode bevel angle for high weld metal oxygen content and is not sensitive to the electrode bevel angle under low weld metal oxygen content. The calculated results for the weld shape, weld size and weld D/W ratio agree well with the experimental ones.

Effect of microfibril twisting in theoretical powder diffraction studies of cellulose Iß

USDA-ARS?s Scientific Manuscript database

Previous studies of calculated diffraction patterns for cellulose crystallites have suggested that the distortions arising once models have been subjected to MD simulation are likely the result of dimensional changes induced by the empirical force field, but have been unable to determine to what ext...

A microwave method for measuring moisture content, density, and grain angle of wood

Treesearch

W. L. James; Y.-H. Yen; R. J. King

1985-01-01

The attenuation, phase shift and depolarization of a polarized 4.81-gigahertz wave as it is transmitted through a wood specimen can provide estimates of the moisture content (MC), density, and grain angle of the specimen. Calibrations are empirical, and computations are complicated, with considerable interaction between parameters. Measured dielectric parameters,...

Morphological changes in woody stem of Prunus jamasakura under simulated microgravity

NASA Technical Reports Server (NTRS)

Yoneyama, Emi; Ishimoto-Negishi, Yoko; Sano, Yuzou; Funada, Ryo; Yamada, Mitsuhiro; Nakamura, Teruko

2004-01-01

When the four-week-old woody stem of Prunus jamasakura was grown under simulated microgravity condition on a three-dimensional clinostat, it bent at growth, and width of its secondary xylem decreased due to the reduction of fiber cell numbers and a smaller microfibril angle in the secondary cell wall, as reported in our previous paper. Gravity induces the development of the secondary xylem that supports the stem upward against the action of gravity. In this study, morphological changes of the tissues and cells were microscopically observed. Disorder was found in the concentric structure of tissues that organize the stem. The radial arrangement of the cells was also disturbed in the secondary xylem, and in the secondary phloem secondary cell walls of the bast fiber cells were undeveloped. These findings suggest that differentiation and development of the secondary xylem and the bast fiber cells are strongly controlled by terrestrial gravity. These tissue and cells functions to support the stem under the action of gravity. Furthermore, clinorotation induced disorder in the straight joint of vessel elements and the lattice-like structure of radial parenchyma cells, which is responsible for water transportation and storage, respectively. Gravity is an essential factor for keeping the division and differentiation normal in woody stem.

Dynamics of water bound to crystalline cellulose

DOE Office of Scientific and Technical Information (OSTI.GOV)

O’Neill, Hugh; Pingali, Sai Venkatesh; Petridis, Loukas

Interactions of water with cellulose are of both fundamental and technological importance. Here, we characterize the properties of water associated with cellulose using deuterium labeling, neutron scattering and molecular dynamics simulation. Quasi-elastic neutron scattering provided quantitative details about the dynamical relaxation processes that occur and was supported by structural characterization using small-angle neutron scattering and X-ray diffraction. We can unambiguously detect two populations of water associated with cellulose. The first is “non-freezing bound” water that gradually becomes mobile with increasing temperature and can be related to surface water. The second population is consistent with confined water that abruptly becomes mobilemore » at ~260 K, and can be attributed to water that accumulates in the narrow spaces between the microfibrils. Quantitative analysis of the QENS data showed that, at 250 K, the water diffusion coefficient was 0.85 ± 0.04 × 10-10 m2sec-1 and increased to 1.77 ± 0.09 × 10-10 m2sec-1 at 265 K. MD simulations are in excellent agreement with the experiments and support the interpretation that water associated with cellulose exists in two dynamical populations. Our results provide clarity to previous work investigating the states of bound water and provide a new approach for probing water interactions with lignocellulose materials.« less

Static and Dynamic Characterization of Cellulose Nanofibril Scaffold-Based Composites

Treesearch

Issam I. Qamhia; Ronald C. Sabo; Rani F. Elhajjar

2014-01-01

The reinforcement potential of novel nanocellulose-based scaffolding reinforcements composed of microfibrils 5 to 50 nm in diameter and several microns in length was investigated. The cellulose nanofibril reinforcement was used to produce a three-dimensional scaffolding. A hybrid two-step approach using vacuum pressure and hot pressing was used to integrate the...

Development and utilization of a bovine type I collagen microfibril model

USDA-ARS?s Scientific Manuscript database

The structure of fibrous collagen, a long triple helix that self-associates in a staggered array to form a matrix of fibrils, fibers and fiber bundles, makes it uniquely suitable as a scaffold for biomaterial engineering. A major challenge for this application is to stabilize collagen structure by m...

The collagen microfibril model, a tool for biomaterials scientists

USDA-ARS?s Scientific Manuscript database

Animal hides, a major byproduct of the meat industry, are a rich source of collagen, a structural protein of the extracellular matrix that gives strength and form to the skin, tendons and bones of mammals. The structure of fibrous collagen, a long triple helix that self-associates in a staggered arr...

Application of the 2-cyanoacetamide method for spectrophotometric assay of cellulase enzyme activity

USDA-ARS?s Scientific Manuscript database

Cellulose is the most abundant form of carbon on the planet. Breakdown of cellulose microfibrils in the plant cell wall is a means by which microbes gain ingress into their respective hosts. Cellulose degradation is also important for global carbon recycling and is the primary substrate for producti...

Probing crystallinity of never-dried wood cellulose with Raman spectroscopy

Treesearch

Umesh P. Agarwal; Sally A. Ralph; Richard S. Reiner; Carlos Baez

2016-01-01

The structure of wood cell wall cellulose in its native state remains poorly understood, limiting the progress of research and development in numerous areas, including plant science, biofuels, and nanocellulose based materials. It is generally believed that cellulose in cell wall microfibrils has both crystalline and amorphous regions. However, there is evidence that...

DNA AND THE FINE STRUCTURE OF SYNAPTIC CHROMOSOMES IN THE DOMESTIC ROOSTER (GALLUS DOMESTICUS)

PubMed Central

Coleman, James R.; Moses, Montrose J.

1964-01-01

The indium trichloride method of Watson and Aldridge (38) for staining nucleic acids for electron microscopy was employed to study the relationship of DNA to the structure of the synaptinemal complex in meiotic prophase chromosomes of the domestic rooster. The selectivity of the method was demonstrated in untreated and DNase-digested testis material by comparing the distribution of indium staining in the electron microscope to Feulgen staining and ultraviolet absorption in thicker sections seen with the light microscope. Following staining by indium, DNA was found mainly in the microfibril component of the synaptinemal complex. When DNA was known to have been removed from aldehyde-fixed material by digestion with DNase, indium stainability was also lost. However, staining of the digested material with non-selective heavy metal techniques demonstrated the presence of material other than DNA in the microfibrils and showed that little alteration in appearance of the chromosome resulted from DNA removal. The two dense lateral axial elements of the synaptinemal complex, but not the central one to any extent, also contained DNA, together with non-DNA material. PMID:14228519

Preparation of micro-fibrillated cellulose based on sugar palm ijuk (Arenga pinnata) fibres through partial acid hydrolysis

NASA Astrophysics Data System (ADS)

Saputro, A.; Verawati, I.; Ramahdita, G.; Chalid, M.

2017-07-01

The aim of this study was to isolate and characterized micro-fibrillated cellulose (MFC) from sugar palm/ijuk fibre (Arenga pinnata) by partial sulfuric acid hydrolysis. Cellulose fibre was prepared by repeated treatments with 5 wt% sodium hydroxide 2 h at 80°C, followed by bleaching with 1.7 wt% sodium chlorite for 2 h at 80°C in acidic environment under stirring. MFC was prepared by partial hydrolysis with sulfuric acid in various concentrations (30, 40, 50, and 60 % for 45 min at 45 °C) under stirring. Fourier Transform Infrared, Field Emission Scanning Electron Microscope, Thermo Gravimetric Analyzer and X-ray Diffraction characterized cellulose fibre and MFC. FTIR measurements showed that alkaline and bleaching treatments were effective to remove non-cellulosic constituents such as wax, lignin and hemicellulose. FESEM observation revealed conversion into more clear surface and defibrillation of cellulosic fibre after pre-treatments. XRD measurement revealed increase in crystallinity after pre-treatments and acid hydrolysis from 54.4 to 87.8%. Thermal analysis showed that increasing acid concentration reduced thermal stability.

In situ imaging of single carbohydrate-binding modules on cellulose microfibrils.

PubMed

Dagel, Daryl J; Liu, Yu-San; Zhong, Lanlan; Luo, Yonghua; Himmel, Michael E; Xu, Qi; Zeng, Yining; Ding, Shi-You; Smith, Steve

2011-02-03

The low efficiency of enzymes used in the bioprocessing of biomass for biofuels is one of the primary bottlenecks that must be overcome to make lignocellulosic biofuels cost-competitive. One of the rate-limiting factors is the accessibility of the cellulase enzymes to insoluble cellulolytic substrates, facilitated by surface absorption of the carbohydrate-binding modules (CBMs), a component of most cellulase systems. Despite their importance, reports of direct observation of CBM function and activity using microscopic methods are still uncommon. Here, we examine the site-specific binding of individual CBMs to crystalline cellulose in an aqueous environment, using the single molecule fluorescence method known as Defocused Orientation and Position Imaging (DOPI). Systematic orientations were observed that are consistent with the CBMs binding to the two opposite hydrophobic faces of the cellulose microfibril, with a well-defined orientation relative to the fiber axis. The approach provides in situ physical evidence indicating the CBMs bind with a well-defined orientation on those planes, thus supporting a binding mechanism driven by chemical and structural recognition of the cellulose surface.

Cellulose biogenesis: Polymerization and crystallization are coupled processes in Acetobacter xylinum.

PubMed

Benziman, M; Haigler, C H; Brown, R M; White, A R; Cooper, K M

1980-11-01

Calcofluor White ST, stilbene derivative used commerically as an optical brightener for cellulose, increased the rate of glucose polymerization into cellulose by resting cells of the gram-negative bacterium Acetobacter xylinum. This bacterium normally produces a ribbon of cellulose that is a composite of crystalline microfibrils. In concentrations above 0.1 mM, Calcofluor disrupts the assembly of crystalline cellulose I microfibrils and their integration into a composite ribbon by stoichiometric binding to glucose residues of newly polymerized glucan chains. Under these conditions, the rate of glucose polymerization increases up to 4 times the control rate, whereas oxygen uptake increases only 10-15%. These observed effects are readily reversible. If free Calcofluor is washed away or depleted below the threshold value by binding to cellulose as polymerization continues, ribbon production and the normal rate of polymerization resume. It is concluded that polymerization and crystallization are cell-directed, coupled processes and that the rate of crystallization determines the rate of polymerization. It is suggested that coupling must be maintained for biogenesis of crystalline cellulose I.

Evidence for in vitro binding of pectin side chains to cellulose.

PubMed

Zykwinska, Agata W; Ralet, Marie-Christine J; Garnier, Catherine D; Thibault, Jean-François J

2005-09-01

Pectins of varying structures were tested for their ability to interact with cellulose in comparison to the well-known adsorption of xyloglucan. Our results reveal that sugar beet (Beta vulgaris) and potato (Solanum tuberosum) pectins, which are rich in neutral sugar side chains, can bind in vitro to cellulose. The extent of binding varies with respect to the nature and structure of the side chains. Additionally, branched arabinans (Br-Arabinans) or debranched arabinans (Deb-Arabinans; isolated from sugar beet) and galactans (isolated from potato) were shown bind to cellulose microfibrils. The adsorption of Br-Arabinan and galactan was lower than that of Deb-Arabinan. The maximum adsorption affinity of Deb-Arabinan to cellulose was comparable to that of xyloglucan. The study of sugar beet and potato alkali-treated cell walls supports the hypothesis of pectin-cellulose interaction. Natural composites enriched in arabinans or galactans and cellulose were recovered. The binding of pectins to cellulose microfibrils may be of considerable significance in the modeling of primary cell walls of plants as well as in the process of cell wall assembly.

Inhomogeneity of Cellulose Microfibril Assembly in Plant Cell Walls Revealed with Sum Frequency Generation Microscopy.

PubMed

Huang, Shixin; Makarem, Mohamadamin; Kiemle, Sarah N; Hamedi, Hossein; Sau, Moujhuri; Cosgrove, Daniel J; Kim, Seong H

2018-05-17

Sum frequency generation (SFG) vibrational spectroscopy can selectively detect and analyze noncentrosymmetric components interspersed in amorphous matrices; this principle has been used for studies of nanoscale structure and mesoscale assembly of cellulose in plant cell walls. However, the spectral information averaged over a large area or volume cannot provide regiospecific or tissue-specific information of different cells in plants. This study demonstrates spatially resolved SFG analysis and imaging by combining a broad-band SFG spectroscopy system with an optical microscope. The system was designed to irradiate both narrow-band 800 nm and broad-band tunable IR beams through a single reflective objective lens, but from opposite sides of the surface normal direction of the sample. The developed technique was used to reveal inhomogeneous distributions of cellulose microfibrils within single cell walls, such as cotton fibers and onion epidermis as well as among different tissues in Arabidopsis inflorescence stems and bamboo culms. SFG microscopy can be used for vibrational spectroscopic imaging of other biological systems in complement to conventional Fourier transform infrared spectroscopy and confocal Raman microscopy.

A novel method for preparing microfibrillated cellulose from bamboo fibers

NASA Astrophysics Data System (ADS)

Dat Nguyen, Huu; Thanh Thuy Mai, Thi; Bich Nguyen, Ngoc; Duy Dang, Thanh; Loan Phung Le, My; Dang, Tan Tai; Tran, Van Man

2013-03-01

The bamboo fiber is a potential candidate for biomass and power source application. In this study, microfibrillated cellulose (MFC) is prepared from raw fibers of bamboo tree (Bambusa Blumeana J A & J H Schultes) by an alkali treatment at room temperature in association with a bleaching treatment followed by a sulfuric acid hydrolysis. Field-emission scanning electron microscopy (FESEM) images indicated that final products ranged from 20 to 40 nm in diameter. The chemical composition measurement and Fourier transform infrared (FTIR) spectroscopy showed that both hemicellulose and lignin are mostly removed in the MFC. The x-ray diffraction (XRD) results also show that MFC has crystallinity of more than 70%. The thermogravimetric analysis (TGA) curves revealed that cellulose microfibers have a two-step thermal decomposition behavior owing to the attachment of sulfated groups onto the cellulose surface in the hydrolysis process with sulfuric acid. The obtained MFCs may have potential applications in alternative power sources as biomass, in pharmaceutical and optical industries as additives, as well as in composite fields as a reinforcement phase.

Elastic moduli of biological fibers in a coarse-grained model: crystalline cellulose and β-amyloids.

PubMed

Poma, Adolfo B; Chwastyk, Mateusz; Cieplak, Marek

2017-10-25

We study the mechanical response of cellulose and β-amyloid microfibrils to three types of deformation: tensile, indentational, and shear. The cellulose microfibrils correspond to the allomorphs Iα or Iβ whereas the β-amyloid microfibrils correspond to the polymorphs of either two- or three-fold symmetry. This response can be characterized by three elastic moduli, namely, Y L , Y T , and S. We use a structure-based coarse-grained model to analyze the deformations in a unified manner. We find that each of the moduli is almost the same for the two allomorphs of cellulose but Y L is about 20 times larger than Y T (140 GPa vs. 7 GPa), indicating the existence of significant anisotropy. For cellulose we note that the anisotropy results from the involvement of covalent bonds in stretching. For β-amyloid, the sense of anisotropy is opposite to that of cellulose. In the three-fold symmetry case, Y L is about half of Y T (3 vs. 7) whereas for two-fold symmetry the anisotropy is much larger (1.6 vs. 21 GPa). The S modulus is derived to be 1.2 GPa for three-fold symmetry and one half of it for the other symmetry and 3.0 GPa for cellulose. The values of the moduli reflect deformations in the hydrogen-bond network. Unlike in our theoretical approach, no experiment can measure all three elastic moduli with the same apparatus. However, our theoretical results are consistent with various measured values: typical Y L for cellulose Iβ ranges from 133 to 155 GPa, Y T from 2 to 25 GPa, and S from 1.8 to 3.8 GPa. For β-amyloid, the experimental values of S and Y T are about 0.3 GPa and 3.3 GPa respectively, while the value of Y L has not been reported.

Cell-wall architecture and lignin composition of wheat developed in a microgravity environment.

PubMed

Levine, L H; Heyenga, A G; Levine, H G; Choi, J; Davin, L B; Krikorian, A D; Lewis, N G

2001-07-01

The microgravity environment encountered during space-flight has long been considered to affect plant growth and developmental processes, including cell wall biopolymer composition and content. As a prelude to studying how microgravity is perceived - and acted upon - by plants, it was first instructive to investigate what gross effects on plant growth and development occurred in microgravity. Thus, wheat seedlings were exposed to microgravity on board the space shuttle Discovery (STS-51) for a 10 day duration, and these specimens were compared with their counterparts grown on Earth under the same conditions (e.g. controls). First, the primary roots of the wheat that developed under both microgravity and 1 g on Earth were examined to assess the role of gravity on cellulose microfibril (CMF) organization and secondary wall thickening patterns. Using a quick freeze/deep etch technique, this revealed that the cell wall CMFs of the space-grown wheat maintained the same organization as their 1 g-grown counterparts. That is, in all instances, CMFs were randomly interwoven with each other in the outermost layers (farthest removed from the plasma membrane), and parallel to each other within the individual strata immediately adjacent to the plasma membranes. The CMF angle in the innermost stratum relative to the immediately adjacent stratum was ca 80 degrees in both the space and Earth-grown plants. Second, all plants grown in microgravity had roots that grew downwards into the agar; they did not display "wandering" and upward growth as previously reported by others. Third, the space-grown wheat also developed normal protoxylem and metaxylem vessel elements with secondary thickening patterns ranging from spiral to regular pit to reticulate thickenings. Fourthly, both the space- and Earth-grown plants were essentially of the same size and height, and their lignin analyses revealed no substantial differences in their amounts and composition regardless of the gravitational field experienced, i.e. for the purposes of this study, all plants were essentially identical. These results suggest that the microgravity environment itself at best only slightly affected either cell wall biopolymer synthesis or the deposition of CMFs, in contrast to previous assertions.

Cell-wall architecture and lignin composition of wheat developed in a microgravity environment

NASA Technical Reports Server (NTRS)

Levine, L. H.; Heyenga, A. G.; Levine, H. G.; Choi, J.; Davin, L. B.; Krikorian, A. D.; Lewis, N. G.; Sager, J. C. (Principal Investigator)

2001-01-01

The microgravity environment encountered during space-flight has long been considered to affect plant growth and developmental processes, including cell wall biopolymer composition and content. As a prelude to studying how microgravity is perceived - and acted upon - by plants, it was first instructive to investigate what gross effects on plant growth and development occurred in microgravity. Thus, wheat seedlings were exposed to microgravity on board the space shuttle Discovery (STS-51) for a 10 day duration, and these specimens were compared with their counterparts grown on Earth under the same conditions (e.g. controls). First, the primary roots of the wheat that developed under both microgravity and 1 g on Earth were examined to assess the role of gravity on cellulose microfibril (CMF) organization and secondary wall thickening patterns. Using a quick freeze/deep etch technique, this revealed that the cell wall CMFs of the space-grown wheat maintained the same organization as their 1 g-grown counterparts. That is, in all instances, CMFs were randomly interwoven with each other in the outermost layers (farthest removed from the plasma membrane), and parallel to each other within the individual strata immediately adjacent to the plasma membranes. The CMF angle in the innermost stratum relative to the immediately adjacent stratum was ca 80 degrees in both the space and Earth-grown plants. Second, all plants grown in microgravity had roots that grew downwards into the agar; they did not display "wandering" and upward growth as previously reported by others. Third, the space-grown wheat also developed normal protoxylem and metaxylem vessel elements with secondary thickening patterns ranging from spiral to regular pit to reticulate thickenings. Fourthly, both the space- and Earth-grown plants were essentially of the same size and height, and their lignin analyses revealed no substantial differences in their amounts and composition regardless of the gravitational field experienced, i.e. for the purposes of this study, all plants were essentially identical. These results suggest that the microgravity environment itself at best only slightly affected either cell wall biopolymer synthesis or the deposition of CMFs, in contrast to previous assertions.

Biocellulose-based flexible magnetic paper

NASA Astrophysics Data System (ADS)

Barud, H. S.; Tercjak, A.; Gutierrez, J.; Viali, W. R.; Nunes, E. S.; Ribeiro, S. J. L.; Jafellici, M.; Nalin, M.; Marques, R. F. C.

2015-05-01

Biocellulose or bacterial cellulose (BC) is a biocompatible (nano) material produced with a three-dimensional network structure composed of microfibrils having nanometric diameters obtained by the Gluconacetobacter xylinus bacteria. BC membranes present relatively high porosity, allowing the incorporation or synthesis in situ of inorganic nanoparticles for multifunctional applications and have been used as flexible membranes for incorporation of magnetic nanocomposite. In this work, highly stable superparamagnetic iron oxide nanoparticles (SPION), functionalized with polyethylene glycol (PEG), with an average diameter of 5 nm and a saturation magnetization of 41 emu/g at 300 K were prepared. PEG-Fe2O3 hybrid was dispersed by mixing a pristine BC membrane in a stable aqueous dispersion of PEG-SPION. The PEG chains at PEG-SPION's surface provide a good permeability and strong affinity between the BC chains and SPION through hydrogen-bonding interactions. PEG-SPION also allow the incorporation of higher content of nanoparticles without compromising the mechanical properties of the nanocomposite. Structural and magnetic properties of the composite have been characterized by XRD, SEM, energy-dispersive X-ray spectroscopy (EDX), magnetization, Raman spectroscopy, and magnetic force microscopy.

Cellulose nanocrystals the next big nano-thing?

Treesearch

Michael T. Postek; Andras Vladar; John Dagata; Natalia Farkas; Bin Ming; Ronald Sabo; Theodore H. Wegner; James Beecher

2008-01-01

Biomass surrounds us from the smallest alga to the largest redwood tree. Even the largest trees owe their strength to a newly-appreciated class of nanomaterials known as cellulose nanocrystals (CNC). Cellulose, the world’s most abundant natural, renewable, biodegradable polymer, occurs as whisker like microfibrils that are biosynthesized and deposited in plant material...

At $2.15 a Gallon, Cellulosic Ethanol Could Be Cost Competitive -

Science.gov Websites

Continuum Magazine | NREL At $2.15 a Gallon, Cellulosic Ethanol Could Be Cost Competitive In cellulose microfibrils. Photo by Dennis Schroeder, NREL At $2.15 a Gallon, Cellulosic Ethanol Could Be Cost ethanol-ethanol from non-food plant sources-in a way that is cost competitive with other transportation

Role of xyloglucan in cotton (Gossypium hirsutum L.) fiber elongation of the short fiber mutant Ligon-lintless-2 (Li2)

USDA-ARS?s Scientific Manuscript database

Xyloglucan is a matrix polysaccharide found in the cell walls of all land plants. In growing cells, xyloglucan is thought to connect cellulose microfibrils and regulate their separation during wall extension. Ligon lintless-2 (Li2), a monogenic dominant cotton fiber mutation, that causes extreme red...

Transcriptome profiling of radiata pine branches reveals new insights into reaction wood formation with implications in plant gravitropism.

PubMed

Li, Xinguo; Yang, Xiaohui; Wu, Harry X

2013-11-08

Formation of compression (CW) and opposite wood (OW) in branches and bent trunks is an adaptive feature of conifer trees in response to various displacement forces, such as gravity, wind, snow and artificial bending. Several previous studies have characterized tracheids, wood and gene transcription in artificially or naturally bent conifer trunks. These studies have provided molecular basis of reaction wood formation in response to bending forces and gravity stimulus. However, little is known about reaction wood formation and gene transcription in conifer branches under gravity stress. In this study SilviScan® technology was used to characterize tracheid and wood traits in radiate pine (Pinus radiata D. Don) branches and genes differentially transcribed in CW and OW were investigated using cDNA microarrays. CW drastically differed from OW in tracheids and wood traits with increased growth, thicker tracheid walls, larger microfibril angle (MFA), higher density and lower stiffness. However, CW and OW tracheids had similar diameters in either radial or tangential direction. Thus, gravity stress largely influenced wood growth, secondary wall deposition, cellulose microfibril orientation and wood properties, but had little impact on primary wall expansion. Microarray gene transcription revealed about 29% of the xylem transcriptomes were significantly altered in CW and OW sampled in both spring and autumn, providing molecular evidence for the drastic variation in tracheid and wood traits. Genes involved in cell division, cellulose biosynthesis, lignin deposition, and microtubules were mostly up-regulated in CW, conferring its greater growth, thicker tracheid walls, higher density, larger MFA and lower stiffness. However, genes with roles in cell expansion and primary wall formation were differentially transcribed in CW and OW, respectively, implicating their similar diameters of tracheid walls and different tracheid lengths. Interestingly, many genes related to hormone and calcium signalling as well as various environmental stresses were exclusively up-regulated in CW, providing important clues for earlier molecular signatures of reaction wood formation under gravity stimulus. The first comprehensive investigation of tracheid characteristics, wood properties and gene transcription in branches of a conifer species revealed more accurate and new insights into reaction wood formation in response to gravity stress. The identified differentially transcribed genes with diverse functions conferred or implicated drastic CW and OW variation observed in radiata pine branches. These genes are excellent candidates for further researches on the molecular mechanisms of reaction wood formation with a view to plant gravitropism.

Contact angles of wetting and water stability of soil structure

NASA Astrophysics Data System (ADS)

Kholodov, V. A.; Yaroslavtseva, N. V.; Yashin, M. A.; Frid, A. S.; Lazarev, V. I.; Tyugai, Z. N.; Milanovskiy, E. Yu.

2015-06-01

From the soddy-podzolic soils and typical chernozems of different texture and land use, dry 3-1 mm aggregates were isolated and sieved in water. As a result, water-stable aggregates and water-unstable particles composing dry 3-1 mm aggregates were obtained. These preparations were ground, and contact angles of wetting were determined by the static sessile drop method. The angles varied from 11° to 85°. In most cases, the values of the angles for the water-stable aggregates significantly exceeded those for the water-unstable components. In terms of carbon content in structural units, there was no correlation between these parameters. When analyzing the soil varieties separately, the significant positive correlation between the carbon content and contact angle of aggregates was revealed only for the loamy-clayey typical chernozem. Based on the multivariate analysis of variance, the value of contact wetting angle was shown to be determined by the structural units belonging to water-stable or water-unstable components of macroaggregates and by the land use type. In addition, along with these parameters, the texture has an indirect effect.

Properties of carbon composite paper derived from coconut coir as a function of polytetrafluoroethylene content

NASA Astrophysics Data System (ADS)

Destyorini, Fredina; Indriyati; Indayaningsih, Nanik; Prihandoko, Bambang; Zulfia Syahrial, Anne

2018-03-01

The carbon composite papers were produced by utilizing carbon materials from coconut coir. In the present work, carbon composite papers (CCP) were prepared by mixing carbon materials in the form of powder and fibre with polymer (ethylene vinyl acetate and polyethylene glycol) in xylene at 100°C. Then, polytetrafluoroethylene (PTFE) with different content was used to treat the surface of CCP. The properties of PTFE-coated CCP were analysed by means of contact angle measurement, tensile testing, porosity, density, and electrical conductivity measurements. As expected, all CCP’s surfaces treated with PTFE were found to be hydrophobic with contact angle >120° and relatively constant during 60 minutes measurement. Furthermore, water contact angle, density, and mechanical properties of CCP generally increase with increasing PTFE content. However, the porosity and electrical conductivity of CCP decrease slightly as the PTFE content increased from 0 wt% to 30 wt%. Based on the observation and analysis, the optimum PTFE content on CCP was 20 %, in which the mechanical properties and hydrophobicity behaviour were improved significantly, but it was only caused a very small drop in porosity and electrical conductivity

Improvement of Piezoelectricity in Piezoelectric Paper Made With Cellulose

DTIC Science & Technology

2009-11-25

Cellulose microfibril has ordered crystalline regions and disordered regions. b. EAPap is made from cellulose paper on which gold electrodes are...Final Report: AOARD-084035 Improvement of Piezoelectricity in Piezoelectric Paper made with Cellulose •Prof. Jaehwan Kim Center for EAPap...webpage: www.EAPap.com ABSTRACT This report deals with the improvement of piezoelectricity in the piezoelectric paper made with cellulose

Recent Development in Spectroscopic and Chemical Characterization of Cellulose

DTIC Science & Technology

2005-01-01

specific to the reducing end groups of the polysaccharides , confirmed the parallel alignment of molecular chains within the microfibrils in native...they include primary, secondary, and tertiary structures. And indeed, crystallographic studies of the monosaccharides and of related structures...Two approaches were adopted for this purpose. The first was based on examining the Raman spectra of polysaccharide polymers and oligomers that

Comparison of adsorption equilibrium models and error functions for the study of sulfate removal by calcium hydroxyapatite microfibrillated cellulose composite.

PubMed

Hokkanen, Sanna; Bhatnagar, Amit; Koistinen, Ari; Kangas, Teija; Lassi, Ulla; Sillanpää, Mika

2018-04-01

In the present study, the adsorption of sulfates of sodium sulfate (Na 2 SO 4 ) and sodium lauryl sulfate (SLS) by calcium hydroxyapatite-modified microfibrillated cellulose was studied in the aqueous solution. The adsorbent was characterized using elemental analysis, Fourier transform infrared, scanning electron microscope and elemental analysis in order to gain the information on its structure and physico-chemical properties. The adsorption studies were conducted in batch mode. The effects of solution pH, contact time, the initial concentration of sulfate and the effect of competing anions were studied on the performance of synthesized adsorbent for sulfate removal. Adsorption kinetics indicated very fast adsorption rate for sulfate of both sources (Na 2 SO 4 and SLS) and the adsorption process was well described by the pseudo-second-order kinetic model. Experimental maximum adsorption capacities were found to be 34.53 mg g -1 for sulfates of SLS and 7.35 mg g -1 for sulfates of Na 2 SO 4. The equilibrium data were described by the Langmuir, Sips, Freundlich, Toth and Redlich-Peterson isotherm models using five different error functions.

Deposition of tropoelastin into the extracellular matrix requires a competent elastic fiber scaffold but not live cells.

PubMed

Kozel, Beth A; Ciliberto, Christopher H; Mecham, Robert P

2004-04-01

The initial steps of elastic fiber assembly were investigated using an in vitro assembly model in which purified recombinant tropoelastin (rbTE) was added to cultures of live or dead cells. The ability of tropoelastin to associate with preexisting elastic fibers or microfibrils in the extracellular matrix was then assessed by immunofluorescence microscopy using species-specific tropoelastin antibodies. Results show that rbTE can associate with elastic fiber components in the absence of live cells through a process that does not depend on crosslink formation. Time course studies show a transformation of the deposited protein from an initial globular appearance early in culture to a more fibrous structure as the matrix matures. Deposition required the C-terminal region of tropoelastin and correlated with the presence of preexisting elastic fibers or microfibrils. Association of exogenously added tropoelastin to the cellular extracellular matrix was inhibited by the addition of heparan sulfate but not chondroitin sulfate sugars. Together, these results suggest that the matrix elaborated by the cell is sufficient for the initial deposition of tropoelastin in the extracellular space and that elastin assembly may be influenced by the composition of sulfated proteoglycans in the matrix.

Distribution of collagens type V and VI in the normal human alveolar mucosa: an immunoelectronmicroscopic study using ultrathin frozen sections.

PubMed

Rabanus, J P; Gelderblom, H R; Schuppan, D; Becker, J

1991-05-01

The ultrastructural localization of collagens type V and VI in normal human gingival mucosa was investigated by immunoelectron microscopy. Twenty biopsies were fixed in dimethylsuberimidate and shock-frozen in slush nitrogen. Collagen type V was mainly located to meshworks of uniform nonstriated microfibrils of 12 to 20 nm width, which preferentially appeared in larger spaces between cross-striated major collagen fibrils. Occasionally single microfibrils of collagen type V fanned out from the ends of major collagen fibrils, which may indicate a role as a core fibril. Collagen type V was not found in the subepithelial basement membrane and the immediately adjacent stroma. Collagen type VI was detected in a loose reticular network of unbanded microfilaments that were morphologically distinguishable by knoblike protrusions every 100-110 nm. These microfilaments were found in the vicinity, but not as an intrinsic component, of the subepithelial basement membrane. Single filaments of collagen type VI filaments appeared to form bridges between neighboring cross-striated major collagen fibrils, suggesting an interconnecting role for this collagen type. The method presented appears to be excellently suited to study the normal and pathological supramolecular organization of the oral extracellular matrix.

Assembly of collagen into microribbons: effects of pH and electrolytes.

PubMed

Jiang, Fengzhi; Hörber, Heinrich; Howard, Jonathon; Müller, Daniel J

2004-12-01

Collagen represents the major structural protein of the extracellular matrix. Elucidating the mechanism of its assembly is important for understanding many cell biological and medical processes as well as for tissue engineering and biotechnological approaches. In this work, conditions for the self-assembly of collagen type I molecules on a supporting surface were characterized. By applying hydrodynamic flow, collagen assembled into ultrathin ( approximately 3 nm) highly anisotropic ribbon-like structures coating the entire support. We call these novel collagen structures microribbons. High-resolution atomic force microscopy topographs show that subunits of these microribbons are built by fibrillar structures. The smallest units of these fibrillar structures have cross-sections of approximately 3 x 5nm, consistent with current models of collagen microfibril formation. By varying the pH and electrolyte of the buffer solution during the self-assembly process, the microfibril density and contacts formed within this network could be controlled. Under certain electrolyte compositions the microribbons and microfibers display the characteristic D-periodicity of approximately 65 nm observed for much thicker collagen fibrils. In addition to providing insight into the mechanism of collagen assembly, the ultraflat collagen matrices may also offer novel ways to bio-functionalize surfaces.

Cellulose synthase complexes act in a concerted fashion to synthesize highly aggregated cellulose in secondary cell walls of plants

PubMed Central

Li, Shundai; Bashline, Logan; Zheng, Yunzhen; Xin, Xiaoran; Huang, Shixin; Kong, Zhaosheng; Kim, Seong H.; Cosgrove, Daniel J.; Gu, Ying

2016-01-01

Cellulose, often touted as the most abundant biopolymer on Earth, is a critical component of the plant cell wall and is synthesized by plasma membrane-spanning cellulose synthase (CESA) enzymes, which in plants are organized into rosette-like CESA complexes (CSCs). Plants construct two types of cell walls, primary cell walls (PCWs) and secondary cell walls (SCWs), which differ in composition, structure, and purpose. Cellulose in PCWs and SCWs is chemically identical but has different physical characteristics. During PCW synthesis, multiple dispersed CSCs move along a shared linear track in opposing directions while synthesizing cellulose microfibrils with low aggregation. In contrast, during SCW synthesis, we observed swaths of densely arranged CSCs that moved in the same direction along tracks while synthesizing cellulose microfibrils that became highly aggregated. Our data support a model in which distinct spatiotemporal features of active CSCs during PCW and SCW synthesis contribute to the formation of cellulose with distinct structure and organization in PCWs and SCWs of Arabidopsis thaliana. This study provides a foundation for understanding differences in the formation, structure, and organization of cellulose in PCWs and SCWs. PMID:27647923

Cellulose synthase complexes act in a concerted fashion to synthesize highly aggregated cellulose in secondary cell walls of plants.

PubMed

Li, Shundai; Bashline, Logan; Zheng, Yunzhen; Xin, Xiaoran; Huang, Shixin; Kong, Zhaosheng; Kim, Seong H; Cosgrove, Daniel J; Gu, Ying

2016-10-04

Cellulose, often touted as the most abundant biopolymer on Earth, is a critical component of the plant cell wall and is synthesized by plasma membrane-spanning cellulose synthase (CESA) enzymes, which in plants are organized into rosette-like CESA complexes (CSCs). Plants construct two types of cell walls, primary cell walls (PCWs) and secondary cell walls (SCWs), which differ in composition, structure, and purpose. Cellulose in PCWs and SCWs is chemically identical but has different physical characteristics. During PCW synthesis, multiple dispersed CSCs move along a shared linear track in opposing directions while synthesizing cellulose microfibrils with low aggregation. In contrast, during SCW synthesis, we observed swaths of densely arranged CSCs that moved in the same direction along tracks while synthesizing cellulose microfibrils that became highly aggregated. Our data support a model in which distinct spatiotemporal features of active CSCs during PCW and SCW synthesis contribute to the formation of cellulose with distinct structure and organization in PCWs and SCWs of Arabidopsis thaliana This study provides a foundation for understanding differences in the formation, structure, and organization of cellulose in PCWs and SCWs.

TEMPO-oxidized cellulose nanofibers

NASA Astrophysics Data System (ADS)

Isogai, Akira; Saito, Tsuguyuki; Fukuzumi, Hayaka

2011-01-01

Native wood celluloses can be converted to individual nanofibers 3-4 nm wide that are at least several microns in length, i.e. with aspect ratios >100, by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and successive mild disintegration in water. Preparation methods and fundamental characteristics of TEMPO-oxidized cellulose nanofibers (TOCN) are reviewed in this paper. Significant amounts of C6 carboxylate groups are selectively formed on each cellulose microfibril surface by TEMPO-mediated oxidation without any changes to the original crystallinity (~74%) or crystal width of wood celluloses. Electrostatic repulsion and/or osmotic effects working between anionically-charged cellulose microfibrils, the ζ-potentials of which are approximately -75 mV in water, cause the formation of completely individualized TOCN dispersed in water by gentle mechanical disintegration treatment of TEMPO-oxidized wood cellulose fibers. Self-standing TOCN films are transparent and flexible, with high tensile strengths of 200-300 MPa and elastic moduli of 6-7 GPa. Moreover, TOCN-coated poly(lactic acid) films have extremely low oxygen permeability. The new cellulose-based nanofibers formed by size reduction process of native cellulose fibers by TEMPO-mediated oxidation have potential application as environmentally friendly and new bio-based nanomaterials in high-tech fields.

Cytosolic invertase contributes to the supply of substrate for cellulose biosynthesis in developing wood.

PubMed

Rende, Umut; Wang, Wei; Gandla, Madhavi Latha; Jönsson, Leif J; Niittylä, Totte

2017-04-01

Carbon for cellulose biosynthesis is derived from sucrose. Cellulose is synthesized from uridine 5'-diphosphoglucose (UDP-glucose), but the enzyme(s) responsible for the initial sucrose cleavage and the source of UDP-glucose for cellulose biosynthesis in developing wood have not been defined. We investigated the role of CYTOSOLIC INVERTASEs (CINs) during wood formation in hybrid aspen (Populus tremula × tremuloides) and characterized transgenic lines with reduced CIN activity during secondary cell wall biosynthesis. Suppression of CIN activity by 38-55% led to a 9-13% reduction in crystalline cellulose. The changes in cellulose were reflected in reduced diameter of acid-insoluble cellulose microfibrils and increased glucose release from wood upon enzymatic digestion of cellulose. Reduced CIN activity decreased the amount of the cellulose biosynthesis precursor UDP-glucose in developing wood, pointing to the likely cause of the cellulose phenotype. The findings suggest that CIN activity has an important role in the cellulose biosynthesis of trees, and indicate that cellulose biosynthesis in wood relies on a quantifiable UDP-glucose pool. The results also introduce a concept of altering cellulose microfibril properties by modifying substrate supply to cellulose biosynthesis. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Origin of the biomechanical properties of wood related to the fine structure of the multi-layered cell wall.

PubMed

Yamamoto, H; Kojima, Y; Okuyama, T; Abasolo, W P; Gril, J

2002-08-01

In this study, a basic model is introduced to describe the biomechanical properties of the wood from the viewpoint of the composite structure of its cell wall. First, the mechanical interaction between the cellulose microfibril (CMF) as a bundle framework and the lignin-hemicellulose as a matrix (MT) skeleton in the secondary wall is formulated based on "the two phase approximation." Thereafter, the origins of (1) tree growth stress, (2) shrinkage or swelling anisotropy of the wood, and (3) moisture dependency of the Young's modulus of wood along the grain were simulated using the newly introduced model. Through the model formulation; (1) the behavior of the cellulose microfibril (CMF) and the matrix substance (MT) during cell wall maturation was estimated; (2) the moisture reactivity of each cell wall constituent was investigated; and (3) a realistic model of the fine composite structure of the matured cell wall was proposed. Thus, it is expected that the fine structure and internal property of each cell wall constituent can be estimated through the analyses of the macroscopic behaviors of wood based on the two phase approximation.

Hydraulic efficiency compromises compression strength perpendicular to the grain in Norway spruce trunkwood

PubMed Central

2011-01-01

The aim of this study was to investigate bending stiffness and compression strength perpendicular to the grain of Norway spruce (Picea abies (L.) Karst.) trunkwood with different anatomical and hydraulic properties. Hydraulically less safe mature sapwood had bigger hydraulic lumen diameters and higher specific hydraulic conductivities than hydraulically safer juvenile wood. Bending stiffness (MOE) was higher, whereas radial compression strength lower in mature than in juvenile wood. A density-based tradeoff between MOE and hydraulic efficiency was apparent in mature wood only. Across cambial age, bending stiffness did not compromise hydraulic efficiency due to variation in latewood percent and because of the structural demands of the tree top (e.g. high flexibility). Radial compression strength compromised, however, hydraulic efficiency because it was extremely dependent on the characteristics of the “weakest” wood part, the highly conductive earlywood. An increase in conduit wall reinforcement of earlywood tracheids would be too costly for the tree. Increasing radial compression strength by modification of microfibril angles or ray cell number could result in a decrease of MOE, which would negatively affect the trunk’s capability to support the crown. We propose that radial compression strength could be an easily assessable and highly predictive parameter for the resistance against implosion or vulnerability to cavitation across conifer species, which should be topic of further studies. PMID:22058609

Dynamics of water bound to crystalline cellulose.

PubMed

O'Neill, Hugh; Pingali, Sai Venkatesh; Petridis, Loukas; He, Junhong; Mamontov, Eugene; Hong, Liang; Urban, Volker; Evans, Barbara; Langan, Paul; Smith, Jeremy C; Davison, Brian H

2017-09-19

Interactions of water with cellulose are of both fundamental and technological importance. Here, we characterize the properties of water associated with cellulose using deuterium labeling, neutron scattering and molecular dynamics simulation. Quasi-elastic neutron scattering provided quantitative details about the dynamical relaxation processes that occur and was supported by structural characterization using small-angle neutron scattering and X-ray diffraction. We can unambiguously detect two populations of water associated with cellulose. The first is "non-freezing bound" water that gradually becomes mobile with increasing temperature and can be related to surface water. The second population is consistent with confined water that abruptly becomes mobile at ~260 K, and can be attributed to water that accumulates in the narrow spaces between the microfibrils. Quantitative analysis of the QENS data showed that, at 250 K, the water diffusion coefficient was 0.85 ± 0.04 × 10 -10  m 2 sec -1 and increased to 1.77 ± 0.09 × 10 -10  m 2 sec -1 at 265 K. MD simulations are in excellent agreement with the experiments and support the interpretation that water associated with cellulose exists in two dynamical populations. Our results provide clarity to previous work investigating the states of bound water and provide a new approach for probing water interactions with lignocellulose materials.

A novel collagen hydrogel cross-linked by gamma-ray irradiation in acidic pH conditions.

PubMed

Inoue, Naoki; Bessho, Masahiko; Furuta, Masakazu; Kojima, Takao; Okuda, Shuichi; Hara, Masayuki

2006-01-01

We made a new type of collagen gel by gamma-ray irradiation of an acidic solution of type-I collagen, and performed comparative studies on a conventional gel and the new type of gel. The neutral gel, a conventional 0.3% (w/v) collagen gel, was formed at neutral pH and then irradiated by gamma-rays. The acidic gel, a 0.3% (w/v) collagen gel, was formed directly from the acidic solution of collagen by y-ray irradiation. Both types of gel were prepared, swollen in water and then dried for the measurement of specific water content. The neutral gel showed a relatively high specific water content and shrunk moderately, depending on the dose, while the acidic gel showed lower specific water content and shrunk clearly by y-ray irradiation. A three-dimensional tangled network of microfibrils was clearly observed in the neutral gels by scanning electron microscopy, but not in the acidic gels. From these results, we concluded that the acidic gel was quite different from a conventional collagen gel. Sodium dodecylsulfate-polyacrylamide gel electrophoresis showed that the alpha1 subunit and alpha2 subunit of the collagen molecule were cross-linked. The triple-helical structure of collagen was only partially perturbed, but not denatured completely, because the circular dichroism spectrum of the collagen solution irradiated at 1.3 kGy was similar to that of native collagen solution. Amino-acid analysis revealed that tyrosine, phenylalanine and histidine decreased by irradiation in the neutral gel. In the case of the acidic gel, these three amino acids and methionine decreased. We considered that these amino acids were cross-linking points between the collagen subunits during the gamma-ray irradiation.

Mechanical properties of untreated and alkaline treated fibers from zalacca midrib wastes

NASA Astrophysics Data System (ADS)

Raharjo, Wahyu Purwo; Soenoko, Rudy; Purnowidodo, Anindito; Choiron, Mochammad Agus; Triyono

2016-03-01

The environmental concern has been raised due to the abundance of waste from synthetic materials which cannot be biodegraded after their life-time. It provides opportunity to exploit natural resources which are neglected. For example, midrib wastes from zalacca plants after cutting are able to utilize as composite reinforcement. The aim of this research was to characterize the mechanical properties of zalacca midrib fibers. As other ones, zalacca midrib fibers consisted of cellulose, hemicellulose and lignin, which their compositions were 42.54, 34.35 and 28.01 % respectively. To raise their cellulose content, the zalacca fibers were alkaline treated by immersion in the sodium hydroxide for 2 hours and rinsing in the distilled water. The concentration of sodium hydroxide was varied 1 and 5%. To investigate the influence of alkaline treatment, the mechanical testing and morphological analysis was performed. The tensile testing was done to obtain ultimate strength, elastic modulus and strain to fracture. The surface morphology of fibers was observed by SEM. The average ultimate tensile strength of zalacca fibers ranged from 182.12 MPa (untreated) to 417.94 MPa (5%NaOH treated). The diameter measurement showed that the alkaline treatment reduce the average fiber diameters due to the decline of the hemicellulose and lignin content as fiber matrix. This caused the increase of the tensile strength and elastic modulus due to the reduction of diameters as divider meanwhile the cellulose content as structural supporter of the fibers was relatively constant. From the SEM analysis, it was shown that the alkaline treatment reduced the fiber matrix so that its surface morphology became rougher due to the microfibrils appearance.

Structure-function relationships of human meniscus.

PubMed

Danso, Elvis K; Oinas, Joonas M T; Saarakkala, Simo; Mikkonen, Santtu; Töyräs, Juha; Korhonen, Rami K

2017-03-01

Biomechanical properties of human meniscus have been shown to be site-specific. However, it is not known which meniscus constituents at different depths and locations contribute to biomechanical properties obtained from indentation testing. Therefore, we investigated the composition and structure of human meniscus in a site- and depth-dependent manner and their relationships with tissue site-specific biomechanical properties. Elastic and poroelastic properties were analyzed from experimental stress-relaxation and sinusoidal indentation measurements with fibril reinforced poroelastic finite element modeling. Proteoglycan (PG) and collagen contents, as well as the collagen orientation angle, were determined as a function of tissue depth using microscopic and spectroscopic methods, and they were compared with biomechanical properties. For all the measurement sites (anterior, middle and posterior) of lateral and medial menisci (n=26), PG content and collagen orientation angle increased as a function of tissue depth while the collagen content had an initial sharp increase followed by a decrease across tissue depth. The highest values (p<0.05) of elastic parameters (equilibrium and instantaneous moduli) and strain-dependent biomechanical parameters (strain-dependent fibril network modulus and permeability) were observed in the anterior horn of the medial meniscus. This location had also higher (p<0.05) PG content in the deep meniscus, higher (p<0.05) collagen content in the entire tissue depth, and lower (p<0.05) collagen orientation angle at the superficial tissue, as compared to many other locations. On the other hand, in certain comparisons (such as anterior vs. middle sites of the medial meniscus) significantly higher (p<0.05) collagen content and lower orientation angle, without any difference in the PG content, were consistent with increased meniscus modulus and/or nonlinear permeability. This study suggests that nonlinear biomechanical properties of meniscus, caused by the collagen network and fluid, may be strongly influenced by tissue osmotic swelling from the deep meniscus caused by the increased PG content, leading to increased collagen fibril tension. These nonlinear biomechanical properties are suggested to be further amplified by higher collagen content at all tissue depths and superficial collagen fibril orientation. However, these structure-function relationships are suggested to be highly site-specific. Copyright © 2016 Elsevier Ltd. All rights reserved.

Direct Determination of Hydroxymethyl Conformations of Plant Cell Wall Cellulose Using 1H Polarization Transfer Solid-State NMR.

PubMed

Phyo, Pyae; Wang, Tuo; Yang, Yu; O'Neill, Hugh; Hong, Mei

2018-05-14

In contrast to the well-studied crystalline cellulose of microbial and animal origins, cellulose in plant cell walls is disordered due to its interactions with matrix polysaccharides. Plant cell wall (PCW) is an undisputed source of sustainable global energy; therefore, it is important to determine the molecular structure of PCW cellulose. The most reactive component of cellulose is the exocyclic hydroxymethyl group: when it adopts the tg conformation, it stabilizes intrachain and interchain hydrogen bonding, while gt and gg conformations destabilize the hydrogen-bonding network. So far, information about the hydroxymethyl conformation in cellulose has been exclusively obtained from 13 C chemical shifts of monosaccharides and oligosaccharides, which do not reflect the environment of cellulose in plant cell walls. Here, we use solid-state Nuclear Magnetic Resonance (ssNMR) spectroscopy to measure the hydroxymethyl torsion angle of cellulose in two model plants, by detecting distance-dependent polarization transfer between H4 and H6 protons in 2D 13 C- 13 C correlation spectra. We show that the interior crystalline portion of cellulose microfibrils in Brachypodium and Arabidopsis cell walls exhibits H4-H6 polarization transfer curves that are indicative of a tg conformation, whereas surface cellulose chains exhibit slower H4-H6 polarization transfer that is best fit to the gt conformation. Joint constraints by the H4-H6 polarization transfer curves and 13 C chemical shifts indicate that it is unlikely for interior cellulose to have a significant population of the gt and gg conformation mixed with the tg conformation, while surface cellulose may adopt a small percentage of the gg conformation. These results provide new constraints to the structure and matrix interactions of cellulose in plant cell walls, and represent the first direct determination of a torsion angle in an important noncrystalline carbohydrate polymer.

Thermodynamics of cellulose solvation in water and the ionic liquid 1-butyl-3-methylimidazolim chloride.

PubMed

Gross, Adam S; Bell, Alexis T; Chu, Jhih-Wei

2011-11-24

Cellulose is present in biomass as crystalline microfibrils held together by a complex network of intermolecular interactions making it difficult to initiate its hydrolysis and conversion to fuels. While cellulose is insoluble in water and most organic solvents, complete dissolution of cellulose can be achieved in certain classes of ionic liquids (ILs). The present study was undertaken to analyze the thermodynamic driving forces of this process and to understand how the anions and cations comprising an IL interact with the different moieties of glucose residues to cause dissolution. All-atom molecular dynamics (MD) simulations were performed at two extreme states of cellulose dissolution: a crystalline microfibril and a dissociated state in which all the glucan chains of the microfibril are fully separated from each other by at least four solvation shells. MD simulations of the two states were carried out in water and in the IL 1-butyl-3-methylimidazolium chloride (BmimCl) to provide a comprehensive analysis of solvent effects on cellulose dissolution. The results reveal two important molecular aspects of the mechanism of cellulose dissolution. The first is that the perturbation of solvent structures by the dissolved glucan chains can be a crucial factor in determining solubility, particularly for the insolubility of cellulose in water at 300 K. Second, both the Cl(-) and the Bmim(+) ions of BmimCl interact with the moieties of glucan residues that form intersheet contacts, the most robust component of the interaction network of crystalline cellulose. Cl(-) anions can form hydrogen bonds (HBs) with the hydroxyl groups of glucan chains from either the equatorial or the axial directions. For Bmim(+) cations, the calculated density profiles reveal that the contacts with glucan chains along the axial directions are closer than those along the equatorial directions. On the basis of the results of atomistic MD simulations, we propose that interacting with glucan chains along axial directions and disrupting the intersheet contacts of cellulose is an important ability of cellulose pretreatment solvents. © 2011 American Chemical Society

Microstructural Characterization and Mechanical Properties Analysis of Weld Metals with Two Ni Contents During Post-Weld Heat Treatments

NASA Astrophysics Data System (ADS)

Wu, Da-yong; Han, Xiu-lin; Tian, Hong-tao; Liao, Bo; Xiao, Fu-ren

2015-05-01

This study designed post-weld heat treatments, including reheating and tempering, associated with hot bending to investigate the microstructures, toughness, and hardness of two weld metals with different Ni contents (<1 wt pct level). The results indicated that a high Ni content decreased the ferrite transformation temperature and increased the proportion of acicular ferrite (AF). Furthermore, a high Ni content promoted the martensite/austenite (M/A) constituent formation after reheating. The promotion of the M/A formation increased the number of cementite particles, and accelerated cementite coarsening during tempering. The large-angle grain boundary density from the AF improved the toughness despite the negative effect of cementite. The strengthening contributions were calculated, and the grain refinement was the greatest. The high Ni content decreased the effective grain size with a 2 deg tolerance angle, thus enhancing the grain refinement contribution.

Evaluating the composition and processing potential of novel sources of Brazilian biomass for sustainable biorenewables production

PubMed Central

2014-01-01

Background The search for promising and renewable sources of carbohydrates for the production of biofuels and other biorenewables has been stimulated by an increase in global energy demand in the face of growing concern over greenhouse gas emissions and fuel security. In particular, interest has focused on non-food lignocellulosic biomass as a potential source of abundant and sustainable feedstock for biorefineries. Here we investigate the potential of three Brazilian grasses (Panicum maximum, Pennisetum purpureum and Brachiaria brizantha), as well as bark residues from the harvesting of two commercial Eucalyptus clones (E. grandis and E. grandis x urophylla) for biofuel production, and compare these to sugarcane bagasse. The effects of hot water, acid, alkaline and sulfite pretreatments (at increasing temperatures) on the chemical composition, morphology and saccharification yields of these different biomass types were evaluated. Results The average yield (per hectare), availability and general composition of all five biomasses were compared. Compositional analyses indicate a high level of hemicellulose and lignin removal in all grass varieties (including sugarcane bagasse) after acid and alkaline pretreatment with increasing temperatures, whilst the biomasses pretreated with hot water or sulfite showed little variation from the control. For all biomasses, higher cellulose enrichment resulted from treatment with sodium hydroxide at 130°C. At 180°C, a decrease in cellulose content was observed, which is associated with high amorphous cellulose removal and 5-hydroxymethyl-furaldehyde production. Morphological analysis showed the effects of different pretreatments on the biomass surface, revealing a high production of microfibrillated cellulose on grass surfaces, after treatment with 1% sodium hydroxide at 130°C for 30 minutes. This may explain the higher hydrolysis yields resulting from these pretreatments, since these cellulosic nanoparticles can be easily accessed and cleaved by cellulases. Conclusion Our results show the potential of three Brazilian grasses with high productivity yields as valuable sources of carbohydrates for ethanol production and other biomaterials. Sodium hydroxide at 130°C was found to be the most effective pretreatment for enhanced saccharification yields. It was also efficient in the production of microfibrillated cellulose on grass surfaces, thereby revealing their potential as a source of natural fillers used for bionanocomposites production. PMID:24438499

Impact of CCR1 silencing on the assembly of lignified secondary walls in Arabidopsis thaliana.

PubMed

Ruel, Katia; Berrio-Sierra, Jimmy; Derikvand, Mohammad Mir; Pollet, Brigitte; Thévenin, Johanne; Lapierre, Catherine; Jouanin, Lise; Joseleau, Jean-Paul

2009-01-01

A cinnamoyl-CoA reductase 1 knockout mutant in Arabidopsis thaliana was investigated for the consequences of lignin synthesis perturbation on the assembly of the cell walls. The mutant displayed a dwarf phenotype and a strong collapse of its xylem vessels corresponding to lower lignin content and a loss of lignin units of the noncondensed type. Transmission electron microscopy revealed that the transformation considerably impaired the capacity of interfascicular fibers and vascular bundles to complete the assembly of cellulose microfibrils in the S(2) layer, the S(1) layer remaining unaltered. Such disorder in cellulose was correlated with X-ray diffraction showing altered organization. Semi-quantitative immunolabeling of lignins showed that the patterns of distribution were differentially affected in interfascicular fibers and vascular bundles, pointing to the importance of noncondensed lignin structures for the assembly of a coherent secondary wall. The use of laser capture microdissection combined with the microanalysis of lignins and polysaccharides allowed these polymers to be characterized into specific cell types. Wild-type A. thaliana displayed a two-fold higher syringyl to guaiacyl ratio in interfascicular fibers compared with vascular bundles, whereas this difference was less marked in the cinnamoyl-CoA reductase 1 knockout mutant.

Magnetic field effect for cellulose nanofiber alignment

NASA Astrophysics Data System (ADS)

Kim, Jaehwan; Chen, Yi; Kang, Kwang-Sun; Park, Young-Bin; Schwartz, Mark

2008-11-01

Regenerated cellulose formed into cellulose nanofibers under strong magnetic field and aligned perpendicularly to the magnetic field. Well-aligned microfibrils were found as the exposure time of the magnetic field increased. Better alignment and more crystalline structure of the cellulose resulted in the increased decomposition temperature of the material. X-ray crystallograms showed that crystallinity index of the cellulose increased as the exposure time of the magnetic field increased.

Study on the Fabrication and Characterization of Piezoelectric Paper Made With Cellulose

DTIC Science & Technology

2008-10-07

alignment of the chiral nematic phase of a cellulose microfibril suspension. Langmuir 21:2034-2037. Bordel D, Putaux JL, Heux L (2006) Orientation of...Final Report: AOARD-07-4073 Study on the Fabrication and Characterization of Piezoelectric Paper made with Cellulose •Prof. Jaehwan Kim...jaehwan@inha.ac.kr, webpage: www.EAPap.com ABSTRACT This report deals piezoelectric paper made with cellulose by mechanically and electrically

Cellulose powder from Cladophora sp. algae.

PubMed

Ek, R; Gustafsson, C; Nutt, A; Iversen, T; Nyström, C

1998-01-01

The surface are and crystallinity was measured on a cellulose powder made from Cladophora sp. algae. The algae cellulose powder was found to have a very high surface area (63.4 m2/g, N2 gas adsorption) and build up of cellulose with a high crystallinity (approximately 100%, solid state NMR). The high surface area was confirmed by calculations from atomic force microscope imaging of microfibrils from Cladophora sp. algae.

Characterization of metabolic health in mouse models of fibrillin-1 perturbation

PubMed Central

Walji, Tezin A.; Turecamo, Sarah E.; DeMarsilis, Antea J.; Sakai, Lynn Y.; Mecham, Robert P.; Craft, Clarissa S.

2016-01-01

Mutations in the microfibrillar protein fibrillin-1 or the absence of its binding partner microfibril-associated glycoprotein (MAGP1) lead to increased TGFβ signaling due to an inability to sequester latent or active forms of TGFβ, respectively. Mouse models of excess TGFβ signaling display increased adiposity and predisposition to type-2 diabetes. It is therefore interesting that individuals with Marfan syndrome, a disease in which fibrillin-1 mutation leads to aberrant TGFβ signaling, typically present with extreme fat hypoplasia. The goal of this project was to characterize multiple fibrillin-1 mutant mouse strains to understand how fibrillin-1 contributes to metabolic health. The results of this study demonstrate that fibrillin-1 contributes little to lipid storage and metabolic homeostasis, which is in contrast to the obesity and metabolic changes associated with MAGP1 deficiency. MAGP1 but not fibrillin-1 mutant mice had elevated TGFβ signaling in their adipose tissue, which is consistent with the difference in obesity phenotypes. However, fibrillin-1 mutant strains and MAGP1-deficient mice all exhibit increased bone length and reduced bone mineralization which are characteristic of Marfan syndrome. Our findings suggest Marfan-associated adipocyte hypoplasia is likely not due to microfibril-associated changes in adipose tissue, and provide evidence that MAGP1 may function independently of fibrillin in some tissues. PMID:26902431

Residual wood polymers facilitate compounding of microfibrillated cellulose with poly(lactic acid) for 3D printer filaments

NASA Astrophysics Data System (ADS)

Winter, Armin; Mundigler, Norbert; Holzweber, Julian; Veigel, Stefan; Müller, Ulrich; Kovalcik, Adriana; Gindl-Altmutter, Wolfgang

2017-12-01

Microfibrillated cellulose (MFC) is a fascinating material with an obvious potential for composite reinforcement due to its excellent mechanics together with high specific surface area. However, in order to use this potential, commercially viable solutions to important technological challenges have to be found. Notably, the distinct hydrophilicity of MFC prevents efficient drying without loss in specific surface area, necessitating storage and processing in wet condition. This greatly hinders compounding with important technical polymers immiscible with water. Differently from cellulose, the chemistry of the major wood polymers lignin and hemicellulose is much more diverse in terms of functional groups. Specifically, the aromatic moieties present in lignin and acetyl groups in hemicellulose provide distinctly less polar surface-chemical functionality compared to hydroxyl groups which dominate the surface-chemical character of cellulose. It is shown that considerable advantages in the production of MFC-filled poly(lactic acid) filaments for three-dimensional printing can be obtained through the use of MFC containing residual lignin and hemicellulose due to their advantageous surface-chemical characteristics. Specifically, considerably reduced agglomerations of MFC in the filaments in combination with improved printability and improved toughness of printed objects are achieved. This article is part of a discussion meeting issue `New horizons for cellulose nanotechnology'.

Heterologous expression of an active chitin synthase from Rhizopus oryzae.

PubMed

Salgado-Lugo, Holjes; Sánchez-Arreguín, Alejandro; Ruiz-Herrera, José

2016-12-01

Chitin synthases are highly important enzymes in nature, where they synthesize structural components in species belonging to different eukaryotic kingdoms, including kingdom Fungi. Unfortunately, their structure and the molecular mechanism of synthesis of their microfibrilar product remain largely unknown, probably because no fungal active chitin synthases have been isolated, possibly due to their extreme hydrophobicity. In this study we have turned to the heterologous expression of the transcript from a small chitin synthase of Rhizopus oryzae (RO3G_00942, Chs1) in Escherichia coli. The enzyme was active, but accumulated mostly in inclusion bodies. High concentrations of arginine or urea solubilized the enzyme, but their dilution led to its denaturation and precipitation. Nevertheless, use of urea permitted the purification of small amounts of the enzyme. The properties of Chs1 (Km, optimum temperature and pH, effect of GlcNAc) were abnormal, probably because it lacks the hydrophobic transmembrane regions characteristic of chitin synthases. The product of the enzyme showed that, contrasting with chitin made by membrane-bound Chs's and chitosomes, was only partially in the form of short microfibrils of low crystallinity. This approach may lead to future developments to obtain active chitin synthases that permit understanding their molecular mechanism of activity, and microfibril assembly. Copyright © 2016. Published by Elsevier Inc.

Human Eye Development Is Characterized by Coordinated Expression of Fibrillin Isoforms

PubMed Central

Hubmacher, Dirk; Reinhardt, Dieter P.; Plesec, Thomas; Schenke-Layland, Katja; Apte, Suneel S.

2014-01-01

Purpose. Mutations in human fibrillin-1 and -2, which are major constituents of tissue microfibrils, can affect multiple ocular components, including the ciliary zonule, lens, drainage apparatus, cornea, and retina. However, the expression pattern of the three human fibrillins and an integral microfibrillar component, MAGP1, during human eye development is not known. Methods. We analyzed sections from human eyes at gestational weeks (GWs) 6, 8, and 11 and at 1 and 3 years of age with antibodies specific for each human fibrillin isoform or MAGP1, using immunofluorescence microscopy. Results. During embryonic development, each fibrillin isoform was detected in vascular structures bridging the ciliary body and the developing lens, hyaloid vasculature, and retina. In addition, they were present in the developing corneal basement membranes and lens capsule. MAGP1 codistributed with the fibrillin isoforms. In contrast, the juvenile zonule was composed of fibrillin-1 microfibrils containing MAGP1, but fibrillin-2 was absent and fibrillin-3 was only sparsely detected. Conclusions. Fibrillin-1, -2, and, unique to humans, fibrillin-3 are found in various ocular structures during human embryonic eye development, whereas fibrillin-1 dominates the postnatal zonule. We speculate that vasculature spanning the ciliary body and lens, which elaborates fibrillin-2 and -3, may provide an initial scaffold for fibrillin assembly and zonule formation. PMID:25406291

Residual wood polymers facilitate compounding of microfibrillated cellulose with poly(lactic acid) for 3D printer filaments.

PubMed

Winter, Armin; Mundigler, Norbert; Holzweber, Julian; Veigel, Stefan; Müller, Ulrich; Kovalcik, Adriana; Gindl-Altmutter, Wolfgang

2018-02-13

Microfibrillated cellulose (MFC) is a fascinating material with an obvious potential for composite reinforcement due to its excellent mechanics together with high specific surface area. However, in order to use this potential, commercially viable solutions to important technological challenges have to be found. Notably, the distinct hydrophilicity of MFC prevents efficient drying without loss in specific surface area, necessitating storage and processing in wet condition. This greatly hinders compounding with important technical polymers immiscible with water. Differently from cellulose, the chemistry of the major wood polymers lignin and hemicellulose is much more diverse in terms of functional groups. Specifically, the aromatic moieties present in lignin and acetyl groups in hemicellulose provide distinctly less polar surface-chemical functionality compared to hydroxyl groups which dominate the surface-chemical character of cellulose. It is shown that considerable advantages in the production of MFC-filled poly(lactic acid) filaments for three-dimensional printing can be obtained through the use of MFC containing residual lignin and hemicellulose due to their advantageous surface-chemical characteristics. Specifically, considerably reduced agglomerations of MFC in the filaments in combination with improved printability and improved toughness of printed objects are achieved.This article is part of a discussion meeting issue 'New horizons for cellulose nanotechnology'. © 2017 The Author(s).

Cellulose synthase interactive protein 1 (CSI1) mediates the intimate relationship between cellulose microfibrils and cortical microtubules.

PubMed

Lei, Lei; Li, Shundai; Gu, Ying

2012-07-01

Cellulose is synthesized at the plasma membrane by protein complexes known as cellulose synthase complexes (CSCs). The cellulose-microtubule alignment hypothesis states that there is a causal link between the orientation of cortical microtubules and orientation of nascent cellulose microfibrils. The mechanism behind the alignment hypothesis is largely unknown. CESA interactive protein 1 (CSI1) interacts with CSCs and potentially links CSCs to the cytoskeleton. CSI1 not only co-localizes with CSCs but also travels bi-directionally in a speed indistinguishable from CSCs. The linear trajectories of CSI1-RFP coincide with the underlying microtubules labeled by YFP-TUA5. In the absence of CSI1, both the distribution and the motility of CSCs are defective and the alignment of CSCs and microtubules is disrupted. These observations led to the hypothesis that CSI1 directly mediates the interaction between CSCs and microtubules. In support of this hypothesis, CSI1 binds to microtubules directly by an in vitro microtubule-binding assay. In addition to a role in serving as a messenger from microtubule to CSCs, CSI1 labels SmaCCs/MASCs, a compartment that has been proposed to be involved in CESA trafficking and/or delivery to the plasma membrane.

Crystalline and amorphous cellulose in the secondary walls of Arabidopsis.

PubMed

Ruel, Katia; Nishiyama, Yoshiharu; Joseleau, Jean-Paul

2012-09-01

In the cell walls of higher plants, cellulose chains are present in crystalline microfibril, with an amorphous part at the surface, or present as amorphous material. To assess the distribution and relative occurrence of the two forms of cellulose in the inflorescence stem of Arabidopsis, we used two carbohydrate-binding modules, CBM3a and CBM28, specific for crystalline and amorphous cellulose, respectively, with immunogold detection in TEM. The binding of the two CBMs displayed specific patterns suggesting that the synthesis of cellulose leads to variable nanodomains of cellulose structures according to cell type. In developing cell walls, only CBM3a bound significantly to the incipient primary walls, indicating that at the onset of its deposition cellulose is in a crystalline structure. As the secondary wall develops, the labeling with both CBMs becomes more intense. The variation of the labeling pattern by CBM3a between transverse and longitudinal sections appeared related to microfibril orientation and differed between fibers and vessels. Although the two CBMs do not allow the description of the complete status of cellulose microstructures, they revealed the dynamics of the deposition of crystalline and amorphous forms of cellulose during wall formation and between cell types adapting cellulose microstructures to the cell function. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Cellulose synthase interactive protein 1 (CSI1) mediates the intimate relationship between cellulose microfibrils and cortical microtubules

PubMed Central

Lei, Lei; Li, Shundai; Gu, Ying

2012-01-01

Cellulose is synthesized at the plasma membrane by protein complexes known as cellulose synthase complexes (CSCs). The cellulose-microtubule alignment hypothesis states that there is a causal link between the orientation of cortical microtubules and orientation of nascent cellulose microfibrils. The mechanism behind the alignment hypothesis is largely unknown. CESA interactive protein 1 (CSI1) interacts with CSCs and potentially links CSCs to the cytoskeleton. CSI1 not only co-localizes with CSCs but also travels bi-directionally in a speed indistinguishable from CSCs. The linear trajectories of CSI1-RFP coincide with the underlying microtubules labeled by YFP-TUA5. In the absence of CSI1, both the distribution and the motility of CSCs are defective and the alignment of CSCs and microtubules is disrupted. These observations led to the hypothesis that CSI1 directly mediates the interaction between CSCs and microtubules. In support of this hypothesis, CSI1 binds to microtubules directly by an in vitro microtubule-binding assay. In addition to a role in serving as a messenger from microtubule to CSCs, CSI1 labels SmaCCs/MASCs, a compartment that has been proposed to be involved in CESA trafficking and/or delivery to the plasma membrane. PMID:22751327

Collagen Fibrils and Proteoglycans of Macular Dystrophy Cornea: Ultrastructure and 3D Transmission Electron Tomography.

PubMed

Akhtar, Saeed; Alkatan, Hind M; Kirat, Omar; Khan, Adnan A; Almubrad, Turki

2015-06-01

We report the ultrastructure and 3D transmission electron tomography of collagen fibrils (CFs), proteoglycans (PGs), and microfibrils within the CF of corneas of patients with macular corneal dystrophy (MCD). Three normal corneas and three MCD corneas from three Saudi patients (aged 25, 31, and 49 years, respectively) were used for this study. The corneas were processed for light and electron microscopy studies. 3D images were composed from a set of 120 ultrastructural images using the program "Composer" and visualized using the program "Visuliser Kai". 3D image analysis of MCD cornea showed a clear organization of PGs around the CF at very high magnification and degeneration of the microfibrils within the CF. Within the MCD cornea, the PG area in the anterior stroma was significantly larger than in the middle and posterior stroma. The PG area in the MCD cornea was significantly larger compared with the PG area in the normal cornea. The CF diameter and inter-fibrillar spacing of the MCD cornea were significantly smaller compared with those of the normal cornea. Ultrastructural 3D imaging showed that the production of unsulfated keratin sulfate (KS) may lead to the degeneration of micro-CFs within the CFs. The effect of the unsulfated KS was higher in the anterior stroma compared with the posterior stroma.

Antibacterial paperboard packaging using microfibrillated cellulose.

PubMed

Lavoine, Nathalie; Desloges, Isabelle; Manship, Brigitte; Bras, Julien

2015-09-01

The industry and consumers are focusing more and more on the development of biodegradable and lightweight food-packaging materials, which could better preserve the quality of the food and improve its shelf-life. In an attempt to meet these requirements, this study presents a novel bio-substrate able to contain active bio-molecules for future food-packaging applications. Based on a paperboard substrate, the development of an antibacterial bio-packaging material is, therein, achieved using a chlorhexidine digluconate (CHX) solution as a model of an antibacterial molecule, mixed with microfibrillated cellulose (MFC) and used as coating onto paperboard samples. AFM and FE-SEM analyses were performed to underline the nanoporous MFC network able to trap and to progressively release the CHX molecules. The release study of CHX was conducted in an aqueous medium and showed a lower proportion (20 %) of CHX released when using MFC. This led to the constant release of low amounts of CHX over 40 h. Antibacterial tests were carried out to assess the preservation of the antibacterial activity of the samples after the release studies. Samples remained active against Bacillus subtilis, with better results being obtained when MFC was used. The preservation of the quality of a model food was finally evaluated paving the way for future promising applications in the food packaging industry.

Improvement of interfacial adhesion and nondestructive damage evaluation for plasma-treated PBO and Kevlar fibers/epoxy composites using micromechanical techniques and surface wettability.

PubMed

Park, Joung-Man; Kim, Dae-Sik; Kim, Sung-Ryong

2003-08-15

Comparison of interfacial properties and microfailure mechanisms of oxygen-plasma treated poly(p-phenylene-2,6-benzobisoxazole (PBO, Zylon) and poly(p-phenylene terephthalamide) (PPTA, Kevlar) fibers/epoxy composites were investigated using a micromechanical technique and nondestructive acoustic emission (AE). The interfacial shear strength (IFSS) and work of adhesion, Wa, of PBO or Kevlar fiber/epoxy composites increased with oxygen-plasma treatment, due to induced hydrogen and covalent bondings at their interface. Plasma-treated Kevlar fiber showed the maximum critical surface tension and polar term, whereas the untreated PBO fiber showed the minimum values. The work of adhesion and the polar term were proportional to the IFSS directly for both PBO and Kevlar fibers. The microfibril fracture pattern of two plasma-treated fibers appeared obviously. Unlike in slow cooling, in rapid cooling, case kink band and kicking in PBO fiber appeared, whereas buckling in the Kevlar fiber was observed mainly due to compressive and residual stresses. Based on the propagation of microfibril failure toward the core region, the number of AE events for plasma-treated PBO and Kevlar fibers increased significantly compared to the untreated case. The results of nondestructive AE were consistent with microfailure modes.

LWC and Temperature Effects on Ice Accretion Formation on Swept Wings at Glaze Ice Conditions

NASA Technical Reports Server (NTRS)

Vargas, Mario; Reshotko, Eli

2000-01-01

An experiment was conducted to study the effect of liquid water content and temperature on the critical distance in ice accretion formation on swept wings at glaze ice conditions. The critical distance is defined as the distance from the attachment line to tile beginning of the zone where roughness elements develop into glaze ice feathers. A baseline case of 150 mph, 25 F, 0.75 g/cu m. Cloud Liquid Water Content (LWC) and 20 micrometers in Water Droplet Median Volume Diameter (MVD) was chosen. Icing runs were performed on a NACA 0012 swept wing tip at 150 mph and MVD of 20 micrometers for liquid water contents of 0.5 g/cu m, 0.75 g/cu m, and 1.0 g/cu m, and for total temperatures of 20 F, 25 F and 30 F. At each tunnel condition, the sweep angle was changed from 0 deg to 45 deg in 5 deg increments. Casting data, ice shape tracings, and close-up photographic data were obtained. The results showed that decreasing the LWC to 0.5 g/cu m decreases the value of the critical distance at a given sweep angle compared to the baseline case, and starts the formation of complete scallops at 30 sweep angle. Increasing the LWC to 1.0 g/cu m increases the value of the critical distance compared to the baseline case, the critical distance remains always above 0 millimeters and complete scallops are not formed. Decreasing the total temperature to 20 F decreases the critical distance with respect to the baseline case and formation of complete scallops begins at 25 deg sweep angle. When the total temperature is increased to 30 F, bumps covered with roughness elements appear on the ice accretion at 25 deg and 30 deg sweep angles, large ice structures appear at 35 deg and 40 deg sweep angles, and complete scallops are formed at 45 deg sweep angle.

Variation in xylem formation of Viburnum odoratissimum var. awabuki: growth strain and related anatomical features of branches exhibiting unusual eccentric growth.

PubMed

Wang, Yue; Gril, Joseph; Sugiyama, Junji

2009-05-01

Growth strains (GSs) and growth eccentricity in the branches of Viburnum odoratissimum var. awabuki (K. Koch) Zabel were measured. A pronounced growth promotion occurred on the lower side of some branches. Although the GS of the branches was similar to that of normal wood, a larger GS was observed on the upper side of the branches. Thus, eccentric growth occurred on the side opposite to the larger GS. In addition, there was a strong negative relationship between f-back bending and eccentric growth, indicating that eccentric growth largely precluded correction to the vertical position. To understand the function of eccentric growth on the lower side of the branches, we examined several anatomical features of the branches and found that (1) the cell walls of both sides lacked the gelatinous layer, (2) the microfibril angle measured by X-ray diffraction and polarizing light was small on both the upper and the lower sides and (3) the vessel number and the cell wall area did not change to a large extent. The anatomical features of the xylem did not differ obviously between the upper and the lower sides of the branches; however, the fibers were longer on the lower side than on the upper side. These results suggest that the growth stress pattern and formation of branch architecture in V. odoratissimum differ from those observed in other woody angiosperms.

A materials perspective of Martyniaceae fruits: Exploring structural and micromechanical properties.

PubMed

Horbens, Melanie; Eder, Michaela; Neinhuis, Christoph

2015-12-01

Several species of the plant family Martyniaceae are characterised by unique lignified capsules with hook-shaped extensions that interlock with hooves and ankles of large mammals to disperse the seeds. The arrangement of fruit endocarp fibre tissues is exceptional and intriguing among plants. Structure-function-relationships of these slender, curved, but mechanically highly stressed fruit extensions are of particular interest that may inspire advanced biomimetic composite materials. In the present study, we analyse mechanical properties and fracture behaviour of the hook-shaped fruit extensions under different load conditions. The results are correlated with calculated stress distributions, the specific cell wall structure, and chemical composition, providing a detailed interpretation of the complex fruit tissue microstructure. At the cell wall level, both a large microfibril angle and greater strain rates resulted in Young's moduli of 4-9 GPa, leading to structural plasticity. Longitudinally arranged fibre bundles contribute to a great tensile strength. At the tissue level, transversely oriented fibres absorb radial stresses upon bending, whereas cells encompass and pervade longitudinal fibre bundles, thus, stabilise them against buckling. During bending and torsion, microcracks between axial fibre bundles are probably spanned analogous to a circular anchor. Our study fathoms a highly specialized plant structure, substantiating former assumptions about epizoochory as dispersal mode. While the increased flexibility allows for proper attachment of fruits during dynamical locomotion, the high strength and stability prevent a premature failure due to heavy loads exerted by the animal. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Stress Related Surface Tension Effects in Hard Elastic Polymers.

DTIC Science & Technology

1982-08-19

tension 4, and viscosity and the ,_;.rain imposed csn the materials. Results indicate that these microfi-r! Slated polymers contain a substantia- surface...modulus, 2) large recoverability (up to 98%), 3) ’energetic’ elasticity, and 4) high porosity. This field was thoroughly reviewed by Cannon, McKenna, and...influenced ’N load bearing microfibrils, open to the environment. The stress sensitivity of hard elastic polymers to changes in environmental surface

Structure Formation in Solutions of Rigid Polymers Undergoing a Phase Transition

DTIC Science & Technology

1987-04-01

cyclohexene dioxide (ERL-4206) - 10 g. nonenyl succinic anhydride (NSA) - 26 g. dimethyl amino ethanol ( DMAE ) - 0.4 g. After infiltration, short segments...existence of a significant number of defects within the individual microfibril. The presence of defects in the lateral packing of PBT chains is also suggested...of the D- and L- enantiomers yields a nematic phase. The ordered phases exhi- bit complex textures due to defects (disclinations) which depend on

A High Resolution Capacitive Sensing System for the Measurement of Water Content in Crude Oil

PubMed Central

Aslam, Muhammad Zubair; Tang, Tong Boon

2014-01-01

This paper presents the design of a non-intrusive system to measure ultra-low water content in crude oil. The system is based on a capacitance to phase angle conversion method. Water content is measured with a capacitance sensor comprising two semi-cylindrical electrodes mounted on the outer side of a glass tube. The presence of water induces a capacitance change that in turn converts into a phase angle, with respect to a main oscillator. A differential sensing technique is adopted not only to ensure high immunity against temperature variation and background noise, but also to eliminate phase jitter and amplitude variation of the main oscillator that could destabilize the output. The complete capacitive sensing system was implemented in hardware and experiment results using crude oil samples demonstrated that a resolution of ±50 ppm of water content in crude oil was achieved by the proposed design. PMID:24967606

A high resolution capacitive sensing system for the measurement of water content in crude oil.

PubMed

Zubair, Muhammad; Tang, Tong Boon

2014-06-25

This paper presents the design of a non-intrusive system to measure ultra-low water content in crude oil. The system is based on a capacitance to phase angle conversion method. Water content is measured with a capacitance sensor comprising two semi-cylindrical electrodes mounted on the outer side of a glass tube. The presence of water induces a capacitance change that in turn converts into a phase angle, with respect to a main oscillator. A differential sensing technique is adopted not only to ensure high immunity against temperature variation and background noise, but also to eliminate phase jitter and amplitude variation of the main oscillator that could destabilize the output. The complete capacitive sensing system was implemented in hardware and experiment results using crude oil samples demonstrated that a resolution of ± 50 ppm of water content in crude oil was achieved by the proposed design.

On the analysis of time-of-flight spin-echo modulated dark-field imaging data

NASA Astrophysics Data System (ADS)

Sales, Morten; Plomp, Jeroen; Bouwman, Wim G.; Tremsin, Anton S.; Habicht, Klaus; Strobl, Markus

2017-06-01

Spin-Echo Modulated Small Angle Neutron Scattering with spatial resolution, i.e. quantitative Spin-Echo Dark Field Imaging, is an emerging technique coupling neutron imaging with spatially resolved quantitative small angle scattering information. However, the currently achieved relatively large modulation periods of the order of millimeters are superimposed to the images of the samples. So far this required an independent reduction and analyses of the image and scattering information encoded in the measured data and is involving extensive curve fitting routines. Apart from requiring a priori decisions potentially limiting the information content that is extractable also a straightforward judgment of the data quality and information content is hindered. In contrast we propose a significantly simplified routine directly applied to the measured data, which does not only allow an immediate first assessment of data quality and delaying decisions on potentially information content limiting further reduction steps to a later and better informed state, but also, as results suggest, generally better analyses. In addition the method enables to drop the spatial resolution detector requirement for non-spatially resolved Spin-Echo Modulated Small Angle Neutron Scattering.

Effect of dielectric barrier discharge treatment on surface nanostructure and wettability of polylactic acid (PLA) nonwoven fabrics

NASA Astrophysics Data System (ADS)

Ren, Yu; Xu, Lin; Wang, Chunxia; Wang, Xiaona; Ding, Zhirong; Chen, Yuyue

2017-12-01

Polylactic acid (PLA) nonwoven fabrics are treated with atmospheric dielectric barrier discharge (DBD) plasma to improve surface wettability. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) show that micro- to nano-scale textures appear on the treated PLA surfaces dependent on the treatment time. X-ray photoelectron spectroscopy (XPS) analysis reveals that the DBD plasma treatments result in decreased carbon contents and increased oxygen contents as well as slightly increased nitrogen contents. The water contact angle decreases sharply with the increase of the DBD plasma treatment time. The super hydrophilic PLA surfaces (the water contact angle reached 0°) are obtained when the treatment time is longer than 90 s. Ninety days after the DBD plasma treatment, the XPS analysis shows that Csbnd O/Csbnd N and Cdbnd O/Osbnd Cdbnd O percentages decline for all treatment groups. However, the water contact angle is kept constant at 0° for the groups treated above 90 s, which could be due to the oxidized nano-structured layer on the DBD plasma treated PLA surfaces.

Solvent composition of one-step self-etch adhesives and dentine wettability.

PubMed

Grégoire, Geneviève; Dabsie, Firas; Dieng-Sarr, Farimata; Akon, Bernadette; Sharrock, Patrick

2011-01-01

Our aim was to determine the wettability of dentine by four commercial self-etch adhesives and evaluate their spreading rate on the dentine surface. Any correlation with chemical composition was sought, particularly with the amount of solvent or HEMA present in the adhesive. The adhesives used were AdheSE One, Optibond All.In.One, Adper Easy Bond and XenoV. Chemical compositions were determined by proton nuclear magnetic resonance (NMR) spectroscopy of the adhesives dissolved in dimethylsulfoxide. Apparent contact angles for sessile drops of adhesives were measured on dentine slices as a function of time for up to 180s. The water contact angles were determined for fully polymerised adhesives. All adhesives were water-based with total solvent contents ranging from 27% to 73% for HEMA-free adhesives, and averaging 45% for HEMA containing adhesives. The contents in hydrophobic groups decreased as water contents increased. No differences were found in the adhesive contact angles after 180s even though the spreading rates were different for the products tested. Water contact angles differed significantly but were not correlated with HEMA or solvent presence. Manufacturers use different approaches to stabilise acid co-monomer ingredients in self-etch adhesives. Co-solvents, HEMA, or acrylamides without co-solvents are used to simultaneously etch and infiltrate dentine. A large proportion of water is necessary for decalcification action. Copyright © 2010 Elsevier Ltd. All rights reserved.

[Doubting the twirling angle of filiform needle in Science of Acupuncture and Moxibustion textbooks and National Standards].

PubMed

Tian, Kaiyu

2016-07-12

In National Standards (GB) as well as the textbooks used in TCM universities, the twirling angles of acupuncture manipulation vary a lot. By reviewing the previous editions of textbooks from 3 publication houses and comparing the relevant contents, the author calculated the arc lengths of various twirling angles based on the specification of filiform needle in National Standards (GB) and International Standards (ISO). The conclusion is that the twirling angles mentioned in National Standards (GB) and textbooks are too small and not in compliance with the clinical practice. Hence, it is not advisable to propose a rigid specific provision of twirling angle in acupuncture manipulation.

Firing system modification to alter ash properties for reduction of deposition and slagging under low NOx firing conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hart, D.; Lewis, R.; Tobiasz, R.

1998-12-31

The composition and properties of ash formed during coal firing have a major impact on boiler performance. Higher ash content in the coal can mean higher costs associated with coal handling, transportation, ash removal and ash disposal along with higher costs due to the increased ash content`s deleterious effects on pulverizing, combustion and heat transfer. ABB C-E Services, Inc. has conducted research for many years on what might be done to minimize the adverse effects of ash on boiler performance. Recently, ABB C-E Services has studied the effects of firing system modifications on ash composition and properties and the effectmore » these firing system modifications have on overall furnace performance. The subject of this paper is the impact of the installation of the CFS Concentric Firing System on the propensity for boiler wall ash deposition. For this study, CFS yaw angles were varied and particle samples were collected at the waterwalls for the different yaw angles tested. These ash samples were analyzed for ash composition. The results showed that with a larger CFS yaw angle (the air stream directed more towards the boiler walls) the base/acid ratio, iron content and sulfur content of the particle samples collected at the waterwall were reduced. This effect is due to several contributing factors: (1) an oxidizing environment produced by injecting more air toward the walls; and (2) an aerodynamic change which impacts the particle combustion time/temperature history.« less

Neutron Scattering Studies of Nano-Scale Wood-Water Interactions

NASA Astrophysics Data System (ADS)

Plaza Rodriguez, Nayomi Z.

Understanding and controlling water in wood is critical to both improving forest products moisture durability and developing new sustainable forest products-based technologies. While wood is known to be hygroscopic, there is still a lack of understanding on the nanoscale wood-water interactions necessary for increased moisture-durability and dimensional stability. My PhD thesis focuses on the development and implementation of neutron scattering methods that can provide insight on both the structural and dynamical changes associated with these interactions so that products with improved moisture durability can be developed efficiently. Using small angle neutron scattering (SANS) and a custom-built in situ relative humidity chamber I studied the anisotropic moisture-induced swelling of wood nanostructure. First, I studied the effects of sample preparation by comparing SANS patterns of wiley milled wood and intact latewood cell walls, and found that scattering from intact wood provide more information about the spatial arrangement of the wood nanostructures inside the cell wall. Comparisons between SANS patterns from earlywood and latewood, also showed that the higher cell wall density of latewood cell walls results in patterns with more pronounced anisotropic features. Then, by measuring latewood loblolly pine sections obtained from the same growth ring and prepared in each of the primary wood planes, I tracked the cellulose elementary fibril spacing as a function of humidity in both intact and partially cut cell walls. These studies showed that even though swelling at the elementary fibril spacing is responsible for the majority of the transverse swelling observed at the S2 level, it is not primary plane dependent. Additionally, there were no differences in the elementary fibril spacing between partially-cut and intact cell walls, except at high humidity where the spacing in partially-cut cells was higher. SANS was also used to study the effects of two chemical modifications, namely, adhesive infiltration and acetylation, on the wood nanostructure as well as its moisture-induced swelling. Tangential-longitudinal latewood loblolly pine 0.5 mm thick sections were acetylated or treated with an adhesive (Phenol-formaldehyde (PF) or polymeric methylene diisocyanate (pMDI)) using deuterated or hydrogenated chemicals. Contrast variation experiments on wood modified with deuterated chemicals revealed that PF can infiltrate the regions between the elementary fibrils, while acetylation does not. The moisture-induced swelling of the chemically modified wood was studied, by studying the samples modified with hydrogenated chemicals using SANS and the previously built humidity chamber. These studies revealed that while both PF and pMDI can infiltrate the microfibrils, only PF reduced significantly the swelling at both the elementary fibril and bulk levels. In acetylated samples, the elementary fibril spacing was proportional to the moisture-content of the sample, which was reduced with increasing acetylation. This suggested that the acetylation treatment did not reduce the swelling at the elementary fibril but prevented water from entering the microfibril by modifying the regions surrounding the elementary fibrils. Using quasi-elastic neutron scattering (QENS) and a custom-built in situ relative humidity sample environment I measured experimentally the (5 - 400 ps) water dynamics inside wood cell walls for the first time and found that there are two types of bound water in the cell wall, namely, slow and fast water. The motion of both water types is well described by a jump-diffusion model, which corresponds to water molecules whose movement follows a stop and go process. Here, the slow water corresponds to water molecules that are highly associated to the wood polymers, whereas the fast water corresponds to water confined inside nanopores within the wood cell wall.

Vibrational sum frequency generation (SFG) spectroscopic study of crystalline cellulose in biomass

NASA Astrophysics Data System (ADS)

Kim, Seong H.; Lee, Christopher M.; Kafle, Kabindra; Park, Yong Bum; Xi, Xiaoning

2013-09-01

The noncentrosymmetry requirement of sum frequency generation (SFG) spectroscopy allows selective detection of crystalline cellulose in plant cell walls and lignocellulose biomass without spectral interferences from hemicelluloses and lignin. In addition, the phase synchronization requirement of the SFG process allows noninvasive investigation of spatial arrangement of crystalline cellulose microfibrils in the sample. This paper reviews how these principles are applied to reveal structural information of crystalline cellulose in plant cell walls and biomass.

The structure of the catalytic domain of a plant cellulose synthase and its assembly into dimers

DOE PAGES

Olek, Anna T.; Rayon, Catherine; Makowski, Lee; ...

2014-07-10

Cellulose microfibrils are para-crystalline arrays of several dozen linear (1→4)-β-d-glucan chains synthesized at the surface of the cell membrane by large, multimeric complexes of synthase proteins. Recombinant catalytic domains of rice ( Oryza sativa) CesA8 cellulose synthase form dimers reversibly as the fundamental scaffold units of architecture in the synthase complex. Specificity of binding to UDP and UDP-Glc indicates a properly folded protein, and binding kinetics indicate that each monomer independently synthesizes single glucan chains of cellulose, i.e., two chains per dimer pair. In contrast to structure modeling predictions, solution x-ray scattering studies demonstrate that the monomer is a two-domain,more » elongated structure, with the smaller domain coupling two monomers into a dimer. The catalytic core of the monomer is accommodated only near its center, with the plant-specific sequences occupying the small domain and an extension distal to the catalytic domain. This configuration is in stark contrast to the domain organization obtained in predicted structures of plant CesA. As a result, the arrangement of the catalytic domain within the CesA monomer and dimer provides a foundation for constructing structural models of the synthase complex and defining the relationship between the rosette structure and the cellulose microfibrils they synthesize.« less

Water sorption in microfibrillated cellulose (MFC): The effect of temperature and pretreatment.

PubMed

Meriçer, Çağlar; Minelli, Matteo; Giacinti Baschetti, Marco; Lindström, Tom

2017-10-15

Water sorption behavior of two different microfibrillated cellulose (MFC) films, produced by delamination of cellulose pulp after different pretreatment methods, is examined at various temperatures (16-65°C) and up to 70% RH. The effect of drying temperature of MFC films on the water uptake is also investigated. The obtained solubility isotherms showed the typical downward curvature at moderate RH, while no upturn is observed at higher RH; the uptakes are in line with characteristic values for cellulose fibers. Enzymatically pretreated MFC dispersion showed lower solubility than carboxymethylated MFC, likely due to the different material structure, which results from the different preparation methods The experimental results are analyzed by Park and GAB models, which proved suitable to describe the observed behaviors. Interestingly, while no significant thermal effect is detected on water solubility above 35°C, the uptake at 16 and 25°C, at a given RH, is substantially lower than that at higher temperature, indicating that, in such range, sorption process is endothermic. Such unusual behavior for a cellulose-based system seems to be related mainly to the structural characteristics of MFC films, and to relaxation phenomena taking place upon water sorption. The diffusion kinetics, indeed, showed a clear Fickian behavior at low temperature and RH, whereas a secondary process seems to occur at high temperature and higher RH, leading to anomalous diffusion behaviors. Copyright © 2017 Elsevier Ltd. All rights reserved.

Characterization of metabolic health in mouse models of fibrillin-1 perturbation.

PubMed

Walji, Tezin A; Turecamo, Sarah E; DeMarsilis, Antea J; Sakai, Lynn Y; Mecham, Robert P; Craft, Clarissa S

2016-09-01

Mutations in the microfibrillar protein fibrillin-1 or the absence of its binding partner microfibril-associated glycoprotein (MAGP1) lead to increased TGFβ signaling due to an inability to sequester latent or active forms of TGFβ, respectively. Mouse models of excess TGFβ signaling display increased adiposity and predisposition to type-2 diabetes. It is therefore interesting that individuals with Marfan syndrome, a disease in which fibrillin-1 mutation leads to aberrant TGFβ signaling, typically present with extreme fat hypoplasia. The goal of this project was to characterize multiple fibrillin-1 mutant mouse strains to understand how fibrillin-1 contributes to metabolic health. The results of this study demonstrate that fibrillin-1 contributes little to lipid storage and metabolic homeostasis, which is in contrast to the obesity and metabolic changes associated with MAGP1 deficiency. MAGP1 but not fibrillin-1 mutant mice had elevated TGFβ signaling in their adipose tissue, which is consistent with the difference in obesity phenotypes. However, fibrillin-1 mutant strains and MAGP1-deficient mice all exhibit increased bone length and reduced bone mineralization which are characteristic of Marfan syndrome. Our findings suggest that Marfan-associated adipocyte hypoplasia is likely not due to microfibril-associated changes in adipose tissue, and provide evidence that MAGP1 may function independently of fibrillin in some tissues. Copyright © 2016 International Society of Matrix Biology. Published by Elsevier B.V. All rights reserved.

Preparation of micro-fibrillated cellulose from sorghum fibre through alkalization and acetylation treatments

NASA Astrophysics Data System (ADS)

Ismojo; Simanulang, P. H.; Zulfia, A.; Chalid, M.

2017-07-01

Recently, the pollution due to non-degradable materials including plastics, has led to needs on the development of environmental-friendly material. Owing to its biodegradability nature, sorghum fibres are interesting to be modified with petro-polymer as a composite. These materials are also expected to reduce the impact of environmental pollution. Surface modification of sorghum through chemical treatment was aimed to enhanced crystalline part of micro-fibrillated cellulose, thus increased compatibility to petro-polymer, as mean to improve composite properties. The experiments were conducted by alkalization process (10% NaOH) followed by acetylation with acetic acid glacial and acetic anhydride (CH3CO2)2 with additions of 1 and 2 drops of 25% H2SO4. Fourier transform infra-red (FTIR) spectroscopy, field-emission scanning electron microscope (FE-SEM) and x-ray diffraction (XRD) were used to characterize the treated and untreated fibres. The results of investigation showed that the chemical treatments have effectively produced MFC with the smallest fibre size around 5.5 - 6.5 microns and reduced lignin and hemicellulose where the highest crystalline part up to 80.64% was obtained through acetate acid treatment of 17.4 M, followed acetic anhydride with 1 drop of H2SO4 addition. Based on the current results, it is promising that the synthesized composites can be improved for their compatibilities.

DOPI and PALM imaging of single carbohydrate binding modules bound to cellulose nanocrystals

NASA Astrophysics Data System (ADS)

Dagel, D. J.; Liu, Y.-S.; Zhong, L.; Luo, Y.; Zeng, Y.; Himmel, M.; Ding, S.-Y.; Smith, S.

2011-03-01

We use single molecule imaging methods to study the binding characteristics of carbohydrate-binding modules (CBMs) to cellulose crystals. The CBMs are carbohydrate specific binding proteins, and a functional component of most cellulase enzymes, which in turn hydrolyze cellulose, releasing simple sugars suitable for fermentation to biofuels. The CBM plays the important role of locating the crystalline face of cellulose, a critical step in cellulase action. A biophysical understanding of the CBM action aids in developing a mechanistic picture of the cellulase enzyme, important for selection and potential modification. Towards this end, we have genetically modified cellulose-binding CBM derived from bacterial source with green fluorescent protein (GFP), and photo-activated fluorescence protein PAmCherry tags, respectively. Using the single molecule method known as Defocused Orientation and Position Imaging (DOPI), we observe a preferred orientation of the CBM-GFP complex relative to the Valonia cellulose nanocrystals. Subsequent analysis showed the CBMs bind to the opposite hydrophobic <110> faces of the cellulose nanocrystals with a welldefined cross-orientation of about { 70°. Photo Activated Localization Microscopy (PALM) is used to localize CBMPAmCherry with a localization accuracy of { 10nm. Analysis of the nearest neighbor distributions along and perpendicular to the cellulose nanocrystal axes are consistent with single-file CBM binding along the fiber axis, and microfibril bundles consisting of close packed { 20nm or smaller cellulose microfibrils.

The structure of the catalytic domain of a plant cellulose synthase and its assembly into dimers.

PubMed

Olek, Anna T; Rayon, Catherine; Makowski, Lee; Kim, Hyung Rae; Ciesielski, Peter; Badger, John; Paul, Lake N; Ghosh, Subhangi; Kihara, Daisuke; Crowley, Michael; Himmel, Michael E; Bolin, Jeffrey T; Carpita, Nicholas C

2014-07-01

Cellulose microfibrils are para-crystalline arrays of several dozen linear (1→4)-β-d-glucan chains synthesized at the surface of the cell membrane by large, multimeric complexes of synthase proteins. Recombinant catalytic domains of rice (Oryza sativa) CesA8 cellulose synthase form dimers reversibly as the fundamental scaffold units of architecture in the synthase complex. Specificity of binding to UDP and UDP-Glc indicates a properly folded protein, and binding kinetics indicate that each monomer independently synthesizes single glucan chains of cellulose, i.e., two chains per dimer pair. In contrast to structure modeling predictions, solution x-ray scattering studies demonstrate that the monomer is a two-domain, elongated structure, with the smaller domain coupling two monomers into a dimer. The catalytic core of the monomer is accommodated only near its center, with the plant-specific sequences occupying the small domain and an extension distal to the catalytic domain. This configuration is in stark contrast to the domain organization obtained in predicted structures of plant CesA. The arrangement of the catalytic domain within the CesA monomer and dimer provides a foundation for constructing structural models of the synthase complex and defining the relationship between the rosette structure and the cellulose microfibrils they synthesize. © 2014 American Society of Plant Biologists. All rights reserved.

The making of the architecture of the plant cell wall: how cells exploit geometry.

PubMed

Emons, A M; Mulder, B M

1998-06-09

Cell wall deposition is a key process in the formation, growth, and differentiation of plant cells. The most important structural components of the wall are long cellulose microfibrils, which are synthesized by synthases embedded in the plasma membrane. A fundamental question is how the microfibrils become oriented during deposition at the plasma membrane. The current textbook explanation for the orientation mechanism is a guidance system mediated by cortical microtubules. However, too many contraindications are known in secondary cell walls for this to be a universal mechanism, particularly in the case of helicoidal arrangements, which occur in many situations. An additional construction mechanism involves liquid crystalline self-assembly [A. C. Neville (1993) Biology of Fibrous Composites: Development Beyond the Cell Membrane (Cambridge Univ. Press, Cambridge, U.K.)], but the required amount of bulk material that is able to equilibrate thermally is not normally present at any stage of the wall deposition process. Therefore, we have asked whether the complex ordered texture of helicoidal cell walls can be formed in the absence of direct cellular guidance mechanisms. We propose that they can be formed by a mechanism that is based on geometrical considerations. It explains the genesis of the complicated helicoidal texture and shows that the cell has intrinsic, versatile tools for creating a variety of textures. A compelling feature of the model is that local rules generate global order, a typical phenomenon of life.

Transverse mechanical properties of cell walls of single living plant cells probed by laser-generated acoustic waves.

PubMed

Gadalla, Atef; Dehoux, Thomas; Audoin, Bertrand

2014-05-01

Probing the mechanical properties of plant cell wall is crucial to understand tissue dynamics. However, the exact symmetry of the mechanical properties of this anisotropic fiber-reinforced composite remains uncertain. For this reason, biologically relevant measurements of the stiffness coefficients on individual living cells are a challenge. For this purpose, we have developed the single-cell optoacoustic nanoprobe (SCOPE) technique, which uses laser-generated acoustic waves to probe the stiffness, thickness and viscosity of live single-cell subcompartments. This all-optical technique offers a sub-micrometer lateral resolution, nanometer in-depth resolution, and allows the non-contact measurement of the mechanical properties of live turgid tissues without any assumption of mechanical symmetry. SCOPE experiments reveal that single-cell wall transverse stiffness in the direction perpendicular to the epidermis layer of onion cells is close to that of cellulose. This observation demonstrates that cellulose microfibrils are the main load-bearing structure in this direction, and suggests strong bonding of microfibrils by hemicelluloses. Altogether our measurement of the viscosity at high frequencies suggests that the rheology of the wall is dominated by glass-like dynamics. From a comparison with literature, we attribute this behavior to the influence of the pectin matrix. SCOPE's ability to unravel cell rheology and cell anisotropy defines a new class of experiments to enlighten cell nano-mechanics.

The modelling influence of water content to mechanical parameter of soil in analysis of slope stability

NASA Astrophysics Data System (ADS)

Gusman, M.; Nazki, A.; Putra, R. R.

2018-04-01

One of the parameters in slope stability analysis is the shear strength of the soil. Changes in soil shear strength characteristics lead to a decrease in safety factors on the slopes. This study aims to see the effect of increased moisture content on soil mechanical parameters. The case study study was conducted on the slopes of Sitinjau Lauik Kota Padang. The research method was done by laboratory analysis and simple liniear regression analysis and multiple. Based on the test soil results show that the increase in soil water content causes a decrease in cohesion values and internal shear angle. The relationship of moisture content to cohesion is described in equation Y = 55.713-0,6X with R2 = 0.842. While the relationship of water content to shear angle in soil is described in the equation Y = 38.878-0.258X with R2 = 0.915. From several simulations of soil water level improvement, calculation of safety factor (SF) of slope. The calculation results show that the increase of groundwater content is very significant affect the safety factor (SF) slope. SF slope values are in safe condition when moisture content is 50% and when it reaches maximum water content 73.74% slope safety factor value potentially for landslide.

The role of contact angle on unstable flow formation during infiltration and drainage in wettable porous media

NASA Astrophysics Data System (ADS)

Wallach, Rony; Margolis, Michal; Graber, Ellen R.

2013-10-01

The impact of contact angle on 2-D spatial and temporal water-content distribution during infiltration and drainage was experimentally studied. The 0.3-0.5 mm fraction of a quartz dune sand was treated and turned subcritically repellent (contact angle of 33°, 48°, 56°, and 75° for S33, S48, S56, and S75, respectively). The media were packed uniformly in transparent flow chambers and water was supplied to the surface as a point source at different rates (1-20 ml/min). A sequence of gray-value images was taken by CCD camera during infiltration and subsequent drainage; gray values were converted to volumetric water content by water volume balance. Narrow and long plumes with water accumulation behind the downward moving wetting front (tip) and negative water gradient above it (tail) developed in the S56 and S75 media during infiltration at lower water application rates. The plumes became bulbous with spatially uniform water-content distribution as water application rates increased. All plumes in these media propagated downward at a constant rate during infiltration and did not change their shape during drainage. In contrast, regular plume shapes were observed in the S33 and S48 media at all flow rates, and drainage profiles were nonmonotonic with a transition plane at the depth that water reached during infiltration. Given that the studied media have similar pore-size distributions, the conclusion is that imbibition hindered by the nonzero contact angle induced pressure buildup at the wetting front (dynamic water-entry value) that controlled the plume shape and internal water-content distribution during infiltration and drainage.

Constraints on melt content of off-axis magma lenses at the East Pacific Rise from analysis of 3-D seismic amplitude variation with angle of incidence

NASA Astrophysics Data System (ADS)

Aghaei, Omid; Nedimović, Mladen R.; Marjanović, Milena; Carbotte, Suzanne M.; Pablo Canales, J.; Carton, Hélène; Nikić, Nikola

2017-06-01

We use 3-D multichannel seismic data to form partial angle P wave stacks and apply amplitude variation with angle (AVA) crossplotting to assess melt content and melt distribution within two large midcrustal off-axis magma lenses (OAMLs) found along the East Pacific Rise from 9°37.5'N to 9°57'N. The signal envelope of the partial angle stacks suggests that both OAMLs are partially molten with higher average melt content and more uniform melt distribution in the southern OAML than in the northern OAML. For AVA crossplotting, the OAMLs are subdivided into seven 1 km2 analysis windows. The AVA crossplotting results indicate that the OAMLs contain a smaller amount of melt than the axial magma lens (AML). For both OAMLs, a higher melt fraction is detected within analysis windows located close to the ridge axis than within the most distant windows. The highest average melt concentration is interpreted for the central sections of the OAMLs. The overall low OAML melt content could be indicative of melt lost due to recent off-axis eruptions, drainage to the AML, or limited mantle melt supply. Based on the results of this and earlier bathymetric, morphological, geochemical, and geophysical investigations, we propose that the melt-poor OAML state is largely the result of limited melt supply from the underlying mantle source reservoir with smaller contribution attributed to melt leakage to the AML. We hypothesize that the investigated OAMLs have a longer period of melt replenishment, lower eruption recurrence rates, and lower eruption volumes than the AML, though some could be single intrusion events.

Firing system modification to alter ash properties for reduction of deposition and slagging under low NOx firing conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hart, D.; Lewis, R.; Tobiasz, R.

1998-07-01

The composition and properties of ash formed during coal firing have a major impact on boiler performance. Higher ash content in the coal can mean higher costs associated with coal handling, transportation, ash removal and ash disposal along with higher costs due to the increased ash content's deleterious effects on pulverizing, combustion and heat transfer. ABB C-E Services, Inc. has conducted research what might be done to minimize the adverse effects of ash on boiler performance for many years. Recently, ABB C-E Services has studied the effects of firing system modifications on ash composition and properties and the effect thesemore » firing system modifications have on overall furnace performance. The subject of this paper is the impact of the installation of the CFS{trademark} yaw angles were varied and particle samples were collected at the waterwalls for the different yaw angles tested. These ash samples were analyzed for ash composition. The results showed that with a larger CFS{trademark} yaw angle (the air stream directed more towards the boiler walls) the base/acid ratio, iron content and sulfur content of the particle samples collected at the waterwall were reduced. This effect is due to several contributing factors: (1) an oxidizing environment produced by injecting more air toward the walls; and (2) an aerodynamic change which impacts the particle combustion time/temperature history.« less

Prediction of ultrasonic properties from grain angle

Treesearch

M.F. Kabir

2001-01-01

The ultrasonic properties of rubber wood were evaluated in three main symmetry axes – longitudinal (L), radial (R) and tangential direction and also at an angle rotating from the symmetry axes at different moisture content. The ultrasonic velocity were determined with a commercial ultrasonic tester of 45 kHz pulsed longitudinal waves. The experimental results were...

A microstructure-based model for shape distortion during liquid phase sintering

NASA Astrophysics Data System (ADS)

Upadhyaya, Anish

Tight dimensional control is a major concern in consolidation of alloys via liquid phase sintering. This research demonstrates the role of microstructure in controlling the bulk dimensional changes that occur during liquid phase sintering. The dimensional changes were measured using a coordinate measuring machine and also on a real-time basis using in situ video imaging. To quantify compact distortion, a distortion parameter is formulated which takes into consideration the compact distortion in radial as well as axial directions. The microstructural attributes considered in this study are as follows: solid content, dihedral angle, grain size, grain contiguity and connectivity, and solid-solubility. Sintering experiments were conducted with the W-Ni-Cu, W-Ni-Fe, Mo-Ni-Cu, and Fe-Cu systems. The alloy systems and the compositions were selected to give a range of microstructures during liquid phase sintering. The results show that distortion correlates with the measured microstructural attributes. Systems containing a high solid content, high grain coordination number and contiguity, and large dihedral angle have more structural rigidity. The results show that a minimum two-dimensional grain coordination number of 3.0 is necessary for shape preservation. Based on the experimental observations, a model is derived that relates the critical solid content required for maintaining structural rigidity to the dihedral angle. The critical solid content decreases with an increasing dihedral angle. Consequently, W-Cu alloys, which have a dihedral angle of about 95sp°, can be consolidated without gross distortion with as little as 20 vol.% solid. To comprehensively understand the gravitational effects in the evolution of both the microstructure and the macrostructure during liquid phase sintering, W-Ni-Fe alloys with W content varying from 78 to 93 wt.% were sintered in microgravity. Compositions that slump during ground-based sintering also distort when sintered under microgravity. In ground-based sintering, low solid content alloys distort with a typical elephant-foot profile, while in microgravity, the compacts tend to spheroidize. This study shows that microstructural segregation occurs in both ground-based as well as microgravity sintering. In ground-based experiments, because of the density difference between the solid and the liquid phase, the solid content increases from top to the bottom of the sample. In microgravity, the solid content increases from periphery to the center of the samples. A model is derived to show that grain agglomeration and segregation are energetically favored events and will therefore be inherent to the system, even in the absence of gravity. Real time distortion measurement in alloys having appreciable solid-solubility in the liquid phase, such as W-Ni-Fe and Fe-Cu, show that the bulk of distortion occur within the first 5 min of melt formation. Distortion in such systems can be minimized by presaturating the matrix with the solid phase.

Factors affecting the shear strength behavior of municipal solid wastes.

PubMed

Pulat, Hasan Firat; Yukselen-Aksoy, Yeliz

2017-11-01

In this study, the shear strength behavior of European (E-1), Turkey (T-1), and United States of America (U-1) average synthetic municipal solid waste (MSW) compositions were investigated. The large-scale direct shear tests were conducted using fresh and aged MSW samples collected from the Manisa Landfill. The natural samples' test results were compared with synthetic samples. The affecting factors such as ageing, waste composition, and waste type (synthetic and natural) on the shear strength of MSWs were investigated. The effect of composition was evaluated using three main and six modified synthetic MSW compositions. In addition to the synthetic fresh MSW samples, synthetic aged samples were also used. Angle of shearing resistance decreased with increasing organic content whereas cohesion intercept increased with increasing organic content. The fresh and aged wastes with higher coarse fraction lead to a higher angle of shearing resistance. The synthetic aged samples had higher internal friction angles but lower cohesion values than the synthetic fresh samples. Waste with average European composition had the highest internal friction angle as it has the highest fibrous content. On the other hand, the highest cohesion belonged to the Turkey composition, which had the highest organic matter ratio. The main differences between E-1, T-1 and U-1 samples in terms of compositions were observed. The results of this study indicated that shear strength of waste significantly depends on composition and hence a site specific evaluation is recommended. Copyright © 2017 Elsevier Ltd. All rights reserved.

Basic Rheology and Its Application to Nitrocellulose Propellant Processing by Screw Mix-Extruders

DTIC Science & Technology

1990-09-01

plastics and rubber industries. In its raw state NC retains much of the supermolecular structure of the precursor cellulose , and it exists in the form of...they have a cholesteric liquid crystal structure, in common with many other cellulosic materials(ref.8). It has been postulated that thermal...and molecules, see figure 19. Fibrils are about 25 plm in diameter, and are made up of ordered bundles of microfibrils which are about 3 jim in

Microtubules and cellulose microfibrils: how intimate is their relationship?

PubMed

Emons, Anne Mie C; Höfte, Herman; Mulder, Bela M

2007-07-01

The recent visualization of the motion of fluorescently labeled cellulose synthase complexes by Alexander Paredez and colleagues heralds the start of a new era in the science of the plant cell wall. Upon drug-induced complete depolymerization, the movement of the complexes does not become disordered but instead establishes an apparently self-organized novel pattern. The ability to label complexes in vivo has provided us with the ideal tool for tackling the intriguing question of the underlying default mechanisms at play.

Effect of water content on the water repellency for hydrophobized sands

NASA Astrophysics Data System (ADS)

Subedi, S.; Kawamoto, K.; Kuroda, T.; Moldrup, P.; Komatsu, T.

2011-12-01

Alternative earthen covers such as capillary barriers (CBs) and evapotranspirative covers are recognized as useful technical and low-cost solutions for limiting water infiltration and controlling seepage flow at solid waste landfills in semi-arid and arid regions. However, their application to the landfills at wet regions seems to be matter of concern due to loss of their impending capability under high precipitation. One of the possible techniques to enhance the impermeable properties of CBs is to alter soil grain surfaces to be water-repellent by mixing/coating hydrophobic agents (HAs). In order to examine a potential use of model sands hydrophobized with locally available and environmental-friendly HAs such as oleic acid (OA) and stearic acid (SA) for hydrophobic CBs. In the present study, we first characterized the effect of water content on the degree of water repellency (WR) for hydrophobized sands and volcanic ash soil at different depth. Secondly, the time dependency of the contact angle in hydrophobized sands and volcanic ash soils at different water content was evaluated. Further, the effects of hydrophobic organic matter contents on the WR of hydrophobized sands were investigated by horizontal infiltration test. We investigated the degree of WR as functions of volumetric water content (θ) of a volcanic ash soil samples from different depth and water adjusted hydrophobized sand samples with different ratio of HAs by using sessile drop method (SDM). The initial contact angle (αi) measured from SDM decreased gradually with increasing water content in OA and SA coated samples. Measured αi values for volcanic ash soils increased with increasing water content and reached a peak values of 111.7o at θ= 0.325 cm3 cm-3, where-after αi gradually decreased. Each test sample exhibited sharp decrease in contact angle with time at higher water content. Sorptivity values for oleic acid coated samples decreased with increasing HA content and reached the minimum value of 0.068 cm s-1/2 at 1 g HA kg-1 sand, and then gradually increased.

Nondestructive Determination of Moisture Content in Dry Fruits by Impedance and Phase angle measurements

USDA-ARS?s Scientific Manuscript database

Impedance (Z), and phase angle (') of a cylindrical parallel-plate capacitor with dry fruits between the plates was measured using a CI meter (Chari’s Impedance meter), at 1 and 9 MHz . Capacitance, C was derived from Z and ', and using the C, ', and Z values of a set of cherries whose moisture con...

Wood properties and trunk allometry of co-occurring rainforest canopy trees in a cyclone-prone environment.

PubMed

Read, Jennifer; Evans, Robert; Sanson, Gordon D; Kerr, Stuart; Jaffré, Tanguy

2011-11-01

New Caledonia commonly experiences cyclones, so trees there are expected to have enhanced wood traits and trunk allometry that confer resistance to wind damage. We ask whether there is evidence of a trade-off between these traits and growth rate among species. Wood traits, including density, microfibril angle (MFA), and modulus of elasticity (MOE), ratio of tree height to stem diameter, and growth rate were investigated in mature trees of 15 co-occurring canopy species in a New Caledonian rainforest. In contrast to some studies, wood density did not correlate negatively with growth increment. Among angiosperms, wood density and MOE correlated positively with diameter-adjusted tree height, and MOE correlated positively with stem-diameter growth increment. Tall slender trees achieved high stiffness with high efficiency with respect to wood density, in part by low MFA, and with a higher diameter growth increment but a lower buckling safety factor. However, some tree species of a similar niche differed in whole-tree resistance to wind damage and achieved wood stiffness in different ways. There was no evidence of a growth-safety trade-off in these trees. In forests that regularly experience cyclones, there may be stronger selection for high wood density and/or stiffness in fast-growing trees of the upper canopy, with the potential growth trade-off amortized by access to the upper canopy and by other plant traits. Furthermore, decreasing wood density does not necessarily decrease resistance to wind damage, resistance being influenced by other characteristics including cell-level traits (e.g., MFA) and whole-plant architecture.

Mathematical Language Skills of Mathematics Prospective Teachers

ERIC Educational Resources Information Center

Gürefe, Nejla

2018-01-01

Effective mathematics teaching can be actualized only with correct use of the mathematical content language which comprises mathematical rules, concepts, symbols and terms. In this research, it was aimed to examine the mathematics prospective teachers' content language skills in some basic geometric concepts which are ray, angle, polygon,…

Salinity-Dependent Contact Angle Alteration in Oil/Brine/Silicate Systems: the Critical Role of Divalent Cations

PubMed Central

2017-01-01

The effectiveness of water flooding oil recovery depends to an important extent on the competitive wetting of oil and water on the solid rock matrix. Here, we use macroscopic contact angle goniometry in highly idealized model systems to evaluate how brine salinity affects the balance of wetting forces and to infer the microscopic origin of the resultant contact angle alteration. We focus, in particular, on two competing mechanisms debated in the literature, namely, double-layer expansion and divalent cation bridging. Our experiments involve aqueous droplets with a variable content of chloride salts of Na+, K+, Ca2+, and Mg2+, wetting surfaces of muscovite and amorphous silica, and an environment of ambient decane containing small amounts of fatty acids to represent polar oil components. By diluting the salt content in various manners, we demonstrate that the water contact angle on muscovite, not on silica, decreases by up to 25° as the divalent cation concentration is reduced from typical concentrations in seawater to zero. Decreasing the ionic strength at a constant divalent ion concentration, however, has a negligible effect on the contact angle. We discuss the consequences for the interpretation of core flooding experiments and the identification of a microscopic mechanism of low salinity water flooding, an increasingly popular, inexpensive, and environment-friendly technique for enhanced oil recovery. PMID:28332396

Salinity-Dependent Contact Angle Alteration in Oil/Brine/Silicate Systems: the Critical Role of Divalent Cations.

PubMed

Haagh, M E J; Siretanu, I; Duits, M H G; Mugele, F

2017-04-11

The effectiveness of water flooding oil recovery depends to an important extent on the competitive wetting of oil and water on the solid rock matrix. Here, we use macroscopic contact angle goniometry in highly idealized model systems to evaluate how brine salinity affects the balance of wetting forces and to infer the microscopic origin of the resultant contact angle alteration. We focus, in particular, on two competing mechanisms debated in the literature, namely, double-layer expansion and divalent cation bridging. Our experiments involve aqueous droplets with a variable content of chloride salts of Na + , K + , Ca 2+ , and Mg 2+ , wetting surfaces of muscovite and amorphous silica, and an environment of ambient decane containing small amounts of fatty acids to represent polar oil components. By diluting the salt content in various manners, we demonstrate that the water contact angle on muscovite, not on silica, decreases by up to 25° as the divalent cation concentration is reduced from typical concentrations in seawater to zero. Decreasing the ionic strength at a constant divalent ion concentration, however, has a negligible effect on the contact angle. We discuss the consequences for the interpretation of core flooding experiments and the identification of a microscopic mechanism of low salinity water flooding, an increasingly popular, inexpensive, and environment-friendly technique for enhanced oil recovery.

Off-Nadir Hyperspectral Sensing for Estimation of Vertical Profile of Leaf Chlorophyll Content within Wheat Canopies.

PubMed

Kong, Weiping; Huang, Wenjiang; Casa, Raffaele; Zhou, Xianfeng; Ye, Huichun; Dong, Yingying

2017-11-23

Monitoring the vertical profile of leaf chlorophyll (Chl) content within winter wheat canopies is of significant importance for revealing the real nutritional status of the crop. Information on the vertical profile of Chl content is not accessible to nadir-viewing remote or proximal sensing. Off-nadir or multi-angle sensing would provide effective means to detect leaf Chl content in different vertical layers. However, adequate information on the selection of sensitive spectral bands and spectral index formulas for vertical leaf Chl content estimation is not yet available. In this study, all possible two-band and three-band combinations over spectral bands in normalized difference vegetation index (NDVI)-, simple ratio (SR)- and chlorophyll index (CI)-like types of indices at different viewing angles were calculated and assessed for their capability of estimating leaf Chl for three vertical layers of wheat canopies. The vertical profiles of Chl showed top-down declining trends and the patterns of band combinations sensitive to leaf Chl content varied among different vertical layers. Results indicated that the combinations of green band (520 nm) with NIR bands were efficient in estimating upper leaf Chl content, whereas the red edge (695 nm) paired with NIR bands were dominant in quantifying leaf Chl in the lower layers. Correlations between published spectral indices and all NDVI-, SR- and CI-like types of indices and vertical distribution of Chl content showed that reflectance measured from 50°, 30° and 20° backscattering viewing angles were the most promising to obtain information on leaf Chl in the upper-, middle-, and bottom-layer, respectively. Three types of optimized spectral indices improved the accuracy for vertical leaf Chl content estimation. The optimized three-band CI-like index performed the best in the estimation of vertical distribution of leaf Chl content, with R² of 0.84-0.69, and RMSE of 5.37-5.56 µg/cm² from the top to the bottom layers, while the optimized SR-like index was recommended for the bottom Chl estimation due to its simple and universal form. We suggest that it is necessary to take into account the penetration characteristic of the light inside the canopy for different Chl absorption regions of the spectrum and the formula used to derive spectral index when estimating the vertical profile of leaf Chl content using off-nadir hyperspectral data.

Mutations of cellulose synthase (CESA1) phosphorylation sites modulate anisotropic cell expansion and bidirectional mobility of cellulose synthase.

PubMed

Chen, Shaolin; Ehrhardt, David W; Somerville, Chris R

2010-10-05

The CESA1 component of cellulose synthase is phosphorylated at sites clustered in two hypervariable regions of the protein. Mutations of the phosphorylated residues to Ala (A) or Glu (E) alter anisotropic cell expansion and cellulose synthesis in rapidly expanding roots and hypocotyls. Expression of T166E, S686E, or S688E mutants of CESA1 fully rescued the temperature sensitive cesA1-1 allele (rsw1) at a restrictive temperature whereas mutations to A at these positions caused defects in anisotropic cell expansion. However, mutations to E at residues surrounding T166 (i.e., S162, T165, and S167) caused opposite effects. Live-cell imaging of fluorescently labeled CESA showed close correlations between tissue or cell morphology and patterns of bidirectional motility of CESA complexes in the plasma membrane. In the WT, CESA complexes moved at similar velocities in both directions along microtubule tracks. By contrast, the rate of movement of CESA particles was directionally asymmetric in mutant lines that exhibited abnormal tissue or cell expansion, and the asymmetry was removed upon depolymerizing microtubules with oryzalin. This suggests that phosphorylation of CESA differentially affects a polar interaction with microtubules that may regulate the length or quantity of a subset of cellulose microfibrils and that this, in turn, alters microfibril structure in the primary cell wall resulting in or contributing to the observed defect in anisotropic cell expansion.

Hydrolytic degradation and morphologic study of poly-p-dioxanone.

PubMed

Lin, H L; Chu, C C; Grubb, D

1993-02-01

The in vitro hydrolytic degradation of 2-0 size PDS monofilament suture was studied for the purpose of revealing its morphologic structure and degradation mechanism. The sutures were immersed in phosphate buffer of pH 7.44 for up to 120 days at 37 degrees C. These hydrolyzed sutures were examined by the changes in tensile properties, weight, thermal properties, x-ray diffraction structure, surface morphology, and dye diffusion phenomena. It was found that hydrolysis had significant effects on the change of PDS fiber morphology and properties. Hydrolysis, however, had no significant effect on overall molecular orientation of the fiber until the very late stage. PDS suture fibers retained their skeleton throughout the earlier periods of hydrolysis concurrent with mass and tensile strength losses. PDS sutures exhibited an absorption delay of 120 days. Both heat of fusion and melting point exhibited a maximum function of hydrolysis time. Hydrolysis of PDS suture fibers proceeded through two stages: random scission of chain segments located in the amorphous regions of microfibrils and intermicrofibrillar space, followed by stepwise scission of chain segments located in the crystalline regions of microfibrils. Dye diffusion data showed that the passage along the longitudinal direction of the fiber was relatively easier than the lateral direction as evident in the diffusion coefficient, activation energy, and flexibility of chain segments. Swiss-cheese model of fiber structure appears to describe the observed dye diffusion phenomena and their dependence on hydrolysis time and dying temperature.

Multi-Mode Binding of Cellobiohydrolase Cel7A from Trichoderma reesei to Cellulose

PubMed Central

Jalak, Jürgen; Väljamäe, Priit

2014-01-01

Enzymatic hydrolysis of recalcitrant polysaccharides like cellulose takes place on the solid-liquid interface. Therefore the adsorption of enzymes to the solid surface is a pre-requisite for catalysis. Here we used enzymatic activity measurements with fluorescent model-substrate 4-methyl-umbelliferyl-β-D-lactoside for sensitive monitoring of the binding of cellobiohydrolase TrCel7A from Trichoderma reesei to bacterial cellulose (BC). The binding at low nanomolar free TrCel7A concentrations was exclusively active site mediated and was consistent with Langmuir's one binding site model with K d and A max values of 2.9 nM and 126 nmol/g BC, respectively. This is the strongest binding observed with non-complexed cellulases and apparently represents the productive binding of TrCel7A to cellulose chain ends on the hydrophobic face of BC microfibril. With increasing free TrCel7A concentrations the isotherm gradually deviated from the Langmuir's one binding site model. This was caused by the increasing contribution of lower affinity binding modes that included both active site mediated binding and non-productive binding with active site free from cellulose chain. The binding of TrCel7A to BC was found to be only partially reversible. Furthermore, the isotherm was dependent on the concentration of BC with more efficient binding observed at lower BC concentrations. The phenomenon can be ascribed to the BC concentration dependent aggregation of BC microfibrils with concomitant reduction of specific surface area. PMID:25265511

Near-infrared spectroscopic observation of the ageing process in archaeological wood using a deuterium exchange method.

PubMed

Tsuchikawa, Satoru; Yonenobu, Hitoshi; Siesler, H W

2005-03-01

The ageing degradation of the fine wood structure of dry-exposed archaeological wood was investigated by Fourier transform near-infrared spectroscopy with the aid of a deuterium exchange method. The archaeological wood sample was taken from an old wooden temple in Japan (late 7th century), which has been designated as a UNESCO world heritage site. Comparing the analytical results with those of a modern wood sample of the same species, the ageing process of archaeological wood was clarified as a change in the state of order on a macromolecular structural level. It can be concluded from NIR spectra that the amorphous region, and partially semi-crystalline region, in cellulose, hemicellulose, and lignin decreased by the ageing degradation, whereas the crystalline region in cellulose was not affected by the ageing. The accessibility of the diffusant to effect H/D-exchange was monitored by an OH-related absorption band obtained from FT-NIR transmission spectroscopy and characteristically varied with the ageing process of the wood samples, the absorption bands characteristic of a specific state of order and the diffusion agent. Finally, we proposed a morphological model to describe the variation of the fine structure of the microfibrils in the cell wall with ageing degradation. The state of microfibrils changed loosely by ageing, so that elementary fibrils were arranged loosely under 5 A, whereas several elementary fibrils in the modern wood were arranged in very close proximity under 3 A to each other.

Hyaluronic acid and chondroitin sulfate content of osteoarthritic human knee cartilage: site-specific correlation with weight-bearing force based on femorotibial angle measurement.

PubMed

Otsuki, Shuhei; Nakajima, Mikio; Lotz, Martin; Kinoshita, Mitsuo

2008-09-01

This study analyzed glycosaminoglycan (GAG) content in specific compartments of the knee joint to determine the impact of malalignment and helped refine indications for osteotomy. To assess malalignment, the radiological femorotibial angle (FTA) was measured and knee joints were also graded for OA severity with the Kellgren/Lawrence (K/L) classification. Cartilage samples were obtained from 36 knees of 32 OA patients undergoing total knee replacement surgery. Explants were harvested from the medial femoral condyle (MFC), lateral femoral condyle (LFC), patellar groove (PG), and lateral posterior femoral condyle (LPC). Concentrations of hyaluronic acid (HA) and chondroitin sulfate (CS) were measured by high-performance liquid chromatography (HPLC). With OA severity, the average FTA significantly increased. HA and CS content in MFC was negatively correlated with radiographic FTA. In LFC, HA ratio, which is HA content in lateral condyle divided by medial condyle and chondroitin 6 sulfate, increased until about 190 degrees FTA. Importantly, at >190 degrees these contents were significantly decreased. HA and CS content of the femoral condyle shows topographic differences that are related to OA grade and weight-bearing force based on FTA. The clinical relevance is that osteotomy may not be indicated for patients with severe varus (>190 degrees) abnormalities. (c) 2008 Orthopaedic Research Society

Assessing Ink Transfer Performance of Gravure-Offset Fine-Line Circuitry Printing

NASA Astrophysics Data System (ADS)

Cheng, Hsien-Chie; Chen, You-Wei; Chen, Wen-Hwa; Lu, Su-Tsai; Lin, Shih-Ming

2018-03-01

In this study, the printing mechanism and performance of gravure-offset fine-line circuitry printing technology are investigated in terms of key printing parameters through experimental and theoretical analyses. First, the contact angles of the ink deposited on different substrates, blankets, and gravure metal plates are experimentally determined; moreover, their temperature and solvent content dependences are analyzed. Next, the ink solvent absorption and evaporation behaviors of the blankets at different temperatures, times, and numbers of printing repetitions are characterized by conducting experiments. In addition, while printing repeatedly, the surface characteristics of the blankets, such as the contact angle, vary with the amount of absorbed ink solvent, further affecting the ink transfer performance (ratio) and printing quality. Accordingly, the surface effect of the blanket due to ink solvent absorption on the ink contact angle is analyzed. Furthermore, the amount of ink transferred from the gravure plate to the blanket in the "off process" and from the blanket to the substrate in the "set process" is evaluated by conducting a simplified plate-to-plate experiment. The influences of loading rate (printing velocity), temperature, and solvent content on the ink transfer performance are addressed. Finally, the ink transfer mechanism is theoretically analyzed for different solvent contents using Surface Evolver. The calculation results are compared with those of the experiment.

Impact of drainage on wettability of fen peat-moorsh soils

NASA Astrophysics Data System (ADS)

Szajdak, L.; Szatyłowicz, J.; Brandyk, T.

2009-04-01

High water retention in peat is attributed to structural voids (macro-pores) due to the partial degradation of the structure of peat-forming plants, and molecular absorption sites (micro-pores) associated with the formation of humic substances. Water retention by the heterogeneously-structured system in peat organic matter depends on the chemical structure of solid surfaces. These naturally wet solids, if dried sufficiently, lose the ability to rewet quickly when immersed in water. The ability of peat surfaces to attract and hold water is attributed to hydrophilic functional groups which characterize the organic substances of peat. The investigations of chemical and physical properties were performed for three different peat-moorsh soils located in the Biebrza River Valley in Poland. All examined soils were used as meadow. Soil samples were taken from two depths: 5-10 cm (moorsh) and 50-80 cm (peat). Total organic carbon (TOC), dissolved organic carbon (DOC) and humic acids (HA) extracted from these samples were analysed. Also basic physical properties such as ash content and bulk density were measured. Wetting behavior of soils was quantified using water drop penetration time test (WDPT) and measured values of the soil-water contact angle using sessile drop method. The measurements were conducted on air-dry soil samples which volumetric moisture content was not exceeding 7%. The significant differences in the concentrations of TOC, DOC and properties of HA between two investigated depth of among peat and moorsh samples were observed. The measured concentrations of total organic carbon in the considered soils ranged from 37.2 to 45.6%. Generally, the decrease of total organic carbon concentration with depth of profiles was observed. The contents of dissolved organic carbon in the soils ranged from 5.3 to 19.4%. The quantities of dissolved organic carbon decreased simultaneously with E4/E6 values and with the depth of the soil profiles. For the investigated peat's, an increase of the depth is accompanied by the decrease in the degree of humification or an increase in chemical maturity of HA. The measured values of the contact angle for investigated soils were in the range from 81.4˚ to 114.3˚ what indicates their high water repellency. The WDPT was positively correlated with total organic carbon, organic matter and humic acids content while ash content, soil bulk density, pH and absorbance were correlated negatively. The highest value of correlation coefficient (statistically significant) was obtained for relation between WDPT and ash content. The soil water contact angle was less correlated with peat-moorsh soil properties in comparison with WDPT with one exception pH. The pH against the contact angle indicates tendency of increasing the contact angle with decreasing pH.

Rhizobium sp. Degradation of Legume Root Hair Cell Wall at the Site of Infection Thread Origin

PubMed Central

Ridge, Robert W.; Rolfe, Barry G.

1985-01-01

Using a new microinoculation technique, we demonstrated that penetration of Rhizobium sp. into the host root hair cell occurs at 20 to 22 h after inoculation. It did this by dissolving the cell wall maxtrix, leaving a layer of depolymerized wall microfibrils. Colony growth pressure “stretched” the weakened wall, forming a bulge into an interfacial zone between the wall and plasmalemma. At the same time vesicular bodies, similar to plasmalemmasomes, accumulated at the penetration site in a manner which parallels host-pathogen systems. Images PMID:16346892

Gravitropism in Leafy Dicot Stems

NASA Technical Reports Server (NTRS)

Salisbury, F. B.

1985-01-01

A polarizing research microscope with rotating stage and associated camera equipment were ordered, and techniques of fixation and preparation of specimens were perfected for studying possible changes in orientation of cellulose microfibrils in cell walls of gravistimulated dicot stems. Acid ethephon solutions or acid without ethephon caused elongation of stem tissues where they were applied; stems bent away from the side of application. Acid solutions applied to the bottom of horizontal stems greatly delayed bending. Research in tissue sensitivity changes during gravitropic bending of soybean hypocotyls while immersed in auxin and in castor bean stems is also reported.

Atmospheric microwave refractivity and refraction

NASA Technical Reports Server (NTRS)

Yu, E.; Hodge, D. B.

1980-01-01

The atmospheric refractivity can be expressed as a function of temperature, pressure, water vapor content, and operating frequency. Based on twenty-year meteorological data, statistics of the atmospheric refractivity were obtained. These statistics were used to estimate the variation of dispersion, attenuation, and refraction effects on microwave and millimeter wave signals propagating along atmospheric paths. Bending angle, elevation angle error, and range error were also developed for an exponentially tapered, spherical atmosphere.

Fiber Ring Interferometer Noise Study.

DTIC Science & Technology

1980-01-31

data was obtained by a frame-by-frame analysis of the oscilloscope tracing " movies " obtained by changing the twist angle in 50 increments, from about...North Quincy Street Arlington, Virginia 22217 . Approved for Public Release; Distribution Unlimited LC (..; TABLE OF CONTENTS Page I. INTRODUCTION 1...sequence of photographs of the oscilloscope, each corres- ponding to a different twist angle. The resultant " movie " presents a large amount of data in a

Analysis of Relationship between the Body Mass Composition and Physical Activity with Body Posture in Children

PubMed Central

Baran, Joanna; Czenczek-Lewandowska, Ewelina; Leszczak, Justyna; Mazur, Artur

2016-01-01

Introduction. Excessive body mass in turn may contribute to the development of many health disorders including disorders of musculoskeletal system, which still develops intensively at that time. Aim. The aim of this study was to assess the relationship between children's body mass composition and body posture. The relationship between physical activity level of children and the parameters characterizing their posture was also evaluated. Material and Methods. 120 school age children between 11 and 13 years were enrolled in the study, including 61 girls and 59 boys. Each study participant had the posture evaluated with the photogrammetric method using the projection moiré phenomenon. Moreover, body mass composition and the level of physical activity were evaluated. Results. Children with the lowest content of muscle tissue showed the highest difference in the height of the inferior angles of the scapulas in the coronal plane. Children with excessive body fat had less slope of the thoracic-lumbar spine, greater difference in the depth of the inferior angles of the scapula, and greater angle of the shoulder line. The individuals with higher level of physical activity have a smaller angle of body inclination. Conclusion. The content of muscle tissue, adipose tissue, and physical activity level determines the variability of the parameter characterizing the body posture. PMID:27761467

Wettability, soil organic matter and structure-properties of typical chernozems under the forest and under the arable land

NASA Astrophysics Data System (ADS)

Bykova, Galina; Umarova, Aminat; Tyugai, Zemfira; Milanovskiy, Evgeny; Shein, Evgeny

2017-04-01

Intensive tillage affects the properties of soil: decrease in content of soil organic matter and in hydrophobicity of the soil's solid phase, the reduction of amount of water stable aggregates - all this leads to deterioration of the structure of the soil and affects the process of movement of moisture in the soil profile. One of the hypotheses of soil's structure formation ascribes the formation of water stable aggregates with the presence of hydrophobic organic substances on the surface of the soil's solid phase. The aim of this work is to study the effect of tillage on properties of typical chernozems (pachic Voronic Chernozems, Haplic Chernozems) (Russia, Kursk region), located under the forest and under the arable land. The determination of soil-water contact angle was performed by a Drop Shape Analyzer DSA100 (Krüss GmbH, Germany) by the static sessile drop method. For all samples the content of total and organic carbon by dry combustion in oxygen flow and the particle size distribution by the laser diffraction method on the device Analysette 22 comfort, FRITCH, Germany were determined. The estimation of aggregate composition was performed by dry sieving (AS 200, Retsch, Germany), the content of water stable aggregates was estimated by the Savvinov method. There was a positive correlation between the content of organic matter and soil's wettability in studied soils, a growth of contact angle with the increasing the content of organic matter. Under the forest the content of soil organic matter was changed from 6,41% on the surface up to 1,9% at the depth of 100 cm. In the Chernozem under the arable land the organic carbon content in arable horizon is almost two times less. The maximum of hydrophobicity (78.1o) was observed at the depth of 5 cm under the forest. In the profile under the arable land the contact angle value at the same depth was 50o. The results of the structure analysis has shown a decrease in the content of agronomically valuable and water stable aggregates in the profile under arable land. These data indicate the correlation between the wettability of soils with the content of organic matter and their influence on the formation of water stable structure, as well as the negative impact of tillage on the analyzed characteristics.

Off-Nadir Hyperspectral Sensing for Estimation of Vertical Profile of Leaf Chlorophyll Content within Wheat Canopies

PubMed Central

Huang, Wenjiang; Zhou, Xianfeng; Ye, Huichun; Dong, Yingying

2017-01-01

Monitoring the vertical profile of leaf chlorophyll (Chl) content within winter wheat canopies is of significant importance for revealing the real nutritional status of the crop. Information on the vertical profile of Chl content is not accessible to nadir-viewing remote or proximal sensing. Off-nadir or multi-angle sensing would provide effective means to detect leaf Chl content in different vertical layers. However, adequate information on the selection of sensitive spectral bands and spectral index formulas for vertical leaf Chl content estimation is not yet available. In this study, all possible two-band and three-band combinations over spectral bands in normalized difference vegetation index (NDVI)-, simple ratio (SR)- and chlorophyll index (CI)-like types of indices at different viewing angles were calculated and assessed for their capability of estimating leaf Chl for three vertical layers of wheat canopies. The vertical profiles of Chl showed top-down declining trends and the patterns of band combinations sensitive to leaf Chl content varied among different vertical layers. Results indicated that the combinations of green band (520 nm) with NIR bands were efficient in estimating upper leaf Chl content, whereas the red edge (695 nm) paired with NIR bands were dominant in quantifying leaf Chl in the lower layers. Correlations between published spectral indices and all NDVI-, SR- and CI-like types of indices and vertical distribution of Chl content showed that reflectance measured from 50°, 30° and 20° backscattering viewing angles were the most promising to obtain information on leaf Chl in the upper-, middle-, and bottom-layer, respectively. Three types of optimized spectral indices improved the accuracy for vertical leaf Chl content estimation. The optimized three-band CI-like index performed the best in the estimation of vertical distribution of leaf Chl content, with R2 of 0.84–0.69, and RMSE of 5.37–5.56 µg/cm2 from the top to the bottom layers, while the optimized SR-like index was recommended for the bottom Chl estimation due to its simple and universal form. We suggest that it is necessary to take into account the penetration characteristic of the light inside the canopy for different Chl absorption regions of the spectrum and the formula used to derive spectral index when estimating the vertical profile of leaf Chl content using off-nadir hyperspectral data. PMID:29168757

Influences of oxygen content on characteristics of atmospheric pressure dielectric barrier discharge in argon/oxygen mixtures

NASA Astrophysics Data System (ADS)

Fang, Zhi; Shao, Tao; Wang, Ruixue; Yang, Jing; Zhang, Cheng

2016-04-01

The dielectric barrier discharge generated in argon/oxygen mixtures at atmospheric pressure is investigated, and the effect of oxygen content on discharge characteristics at applied voltage of 4.5 kV is studied by means of electrical measurements and optical diagnostics. The results show that the filaments in the discharge regime become more densely packed with the increasing in the oxygen content, and the distribution of the filaments is more uniform in the gap. An increase in the oxygen content results in a decrease in the average power consumed and transported charges, while there exists an optimal value of oxygen content for the production of oxygen radicals. The maximal yield of oxygen radicals is obtained in mixtures of argon with 0.3% oxygen addition, and the oxygen radicals then decrease with the further increase in the oxygen content. The oxygen/argon plasma is employed to modify surface hydrophilicity of the PET films to estimate the influence of oxygen content on the surface treatment, and the static contact angles before and after the treatments are measured. The lowest contact angle is obtained at a 0.3% addition of oxygen to argon, which is in accordance with the optimum oxygen content for oxygen radicals generation. The electron density and electron temperature are estimated from the measured current and optical emission spectroscopy, respectively. The electron density is found to reduce significantly at a higher oxygen content due to the increased electron attachment, while the estimated electron temperature do not change apparently with the oxygen content. Contribution to the Topical Issue "Recent Breakthroughs in Microplasma Science and Technology", edited by Kurt Becker, Jose Lopez, David Staack, Klaus-Dieter Weltmann and Wei Dong Zhu.

Wetting properties and critical micellar concentration of benzalkonium chloride mixed in sodium hypochlorite.

PubMed

Bukiet, Frédéric; Couderc, Guillaume; Camps, Jean; Tassery, Hervé; Cuisinier, Frederic; About, Imad; Charrier, Anne; Candoni, Nadine

2012-11-01

The purposes of the present study were to (1) assess the effect of the addition of benzalkonium chloride to sodium hypochlorite on its wetting properties, contact angle, and surface energy; (2) determine the critical micellar concentration of benzalkonium chloride in sodium hypochlorite; and (3) investigate the influence of addition of benzalkonium chloride on the free chlorine level, cytotoxicity, and antiseptic properties of the mixture. Solutions of benzalkonium chloride, with concentrations ranging from 0%-1%, were mixed in 2.4% sodium hypochlorite and tested as follows. The wetting properties were investigated by measuring the contact angle of the solutions on a nondehydrated dentin surface by using the static sessile drop method. The pending drop technique was subsequently used to determine the surface energy of the solutions. The critical micellar concentration of benzalkonium chloride mixed in sodium hypochlorite was calculated from the data. When 2.4% NaOCl was mixed with benzalkonium chloride at the critical micellar concentration, 3 parameters were tested: free chloride content, cytotoxicity, and antibacterial effects against Enterococcus faecalis. The contact angle (P < .001) as well as the surface energy (P < .001) significantly decreased with increasing benzalkonium chloride concentrations. The critical micellar concentration of benzalkonium chloride in sodium hypochlorite was 0.008%. At this concentration, the addition of benzalkonium chloride had no effect on the free chlorine content, cytotoxicity, or antibacterial efficiency of the mixture. The addition of benzalkonium chloride to sodium hypochlorite at the critical micellar concentration reduced the contact angle by 51.2% and the surface energy by 53.4%, without affecting the free chloride content, cytotoxicity, or antibacterial properties of the mixture. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Transparent anti-stain coatings with good thermal and mechanical properties based on polyimide-silica nanohybrids.

PubMed

Choi, Myeon-Cheon; Sung, Giju; Nagappan, Saravanan; Han, Mi-Jeong; Ha, Chang-Sik

2012-07-01

In this work, we synthesized polyimide/silica hybrid materials via sol-gel method using a fluorinated poly(amic acid) silane precursor and a variety of perfluorosilane contents. We studied the influence of a hybrid coating film with the following characteristics; hydrophobicity, oleophobicity, optical transparency, and surface hardness of the coating films. The hybrid coatings with the fluorosilane contents up to 10 wt% are optically transparent and present good thermal stability with a degradation temperature of > 500 degrees C as well as a glass transition of > 300 degrees C. Both water contact angle and oil contact angle increase rapidly with introducing small amount of the fluorosilane in the hybrids and reaches the maximum of 115 degrees and 61 degrees, respectively. The hardness of the hybrid coatings increases up to 5H with an increase of the FTES content in the hybrids. These colorless, transparent, and thermally stable hybrid materials could be suitable for applications as anti-stain coatings.

Active microwave measurement of soil water content

NASA Technical Reports Server (NTRS)

Ulaby, F. T.; Cihlar, J.; Moore, R. K.

1974-01-01

Measurements of radar backscatter from bare soil at 4.7, 5.9, and 7.1 GHz for incident angles of 0-70 deg have been analyzed to determine sensitivity to soil moisture. Because the effective depth of penetration of the radar signal is only about one skin depth, the observed signals were correlated with the moisture in a skin depth as characterized by the attenuation coefficient (reciprocal of skin depth). Since the attenuation coefficient is a monotonically increasing function of moisture density, it may also be used as a measure of moisture content over the distance involved, which varies with frequency and moisture content. The measurements show an approximately linear increase in scattering with attenuation coefficient of the soil at angles within 10 deg of vertical and all frequencies. At 4.7 GHz this increase continues relatively large out to 70 deg incidence, but by 7.1 GHz the sensitivity is much less even at 20 deg and practically gone at 50 deg.

A Laboratory Investigation on Shear Strength Behavior of Sandy Soil: Effect of Glass Fiber and Clinker Residue Content

NASA Astrophysics Data System (ADS)

Bouaricha, Leyla; Henni, Ahmed Djafar; Lancelot, Laurent

2017-12-01

A study was undertaken to investigate the shear strength parameters of treated sands reinforced with randomly distributed glass fibers by carrying out direct shear test after seven days curing periods. Firstly, we studied the fiber content and fiber length effect on the peak shear strength on samples. The second part gives a parametric analysis on the effect of glass fiber and clinker residue content on the shear strength parameters for two types of uniform Algerian sands having different particle sizes (Chlef sand and Rass sand) with an average relative density Dr = 50%. Finally, the test results show that the combination of glass fiber and clinker residue content can effectively improve the shear strength parameters of soil in comparison with unreinforced soil. For instance, there is a significant gain for the cohesion and friction angle of reinforced sand of Chlef. Compared to unreinforced sand, the cohesion for sand reinforced with different ratios of clinker residue increased by 4.36 to 43.08 kPa for Chlef sand and by 3.1 to 28.64 kPa for Rass sand. The feature friction angles increased from 38.73° to 43.01° (+4.28°), and after the treatment, clinker residue content of soil evaluated to 5% (WRC = 5%).

Carotenoids from new apricot (Prunus armeniaca L.) varieties and their relationship with flesh and skin color.

PubMed

Ruiz, David; Egea, José; Tomás-Barberán, Francisco A; Gil, María I

2005-08-10

Thirty-seven apricot varieties, including four new releases (Rojo Pasión, Murciana, Selene, and Dorada) obtained from different crosses between apricot varieties and three traditional Spanish cultivars (Currot, Mauricio, and Búlida), were separated according to flesh color into four groups. The L*, a*, b*, hue angle, and chroma color measurements on the skin and flesh as well as other quality indices including flesh firmness, soluble solids, titratable acidity, and pH were plotted against the total carotenoid content measured by HPLC. Among the 37 apricot varieties, the total carotenoid content ranged from 1,512 to 16,500 microg 100 g(-1) of edible portion, with beta-carotene as the main pigment followed by beta-cryptoxanthin and gamma-carotene. The wide range of variability in the provitamin A content in the apricot varieties encouraged these studies in order to select the breeding types with enhanced carotenoid levels as the varieties with a higher potential health benefit. The carotenoid content was correlated with the color measurements, and the hue angle in both flesh and peel was the parameter with the best correlation (R = 0.92 and 0.84, respectively). An estimation of the carotenoid content in apricots could be achieved by using a portable colorimeter, as a simple and easy method for field usage applications.

High indium content homogenous InAlN layers grown by plasma-assisted molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Kyle, Erin C. H.; Kaun, Stephen W.; Wu, Feng; Bonef, Bastien; Speck, James S.

2016-11-01

InAlN grown by plasma-assisted molecular beam epitaxy often contains a honeycomb microstructure. The honeycomb microstructure consists of 5-10 nm diameter aluminum-rich regions which are surrounded by indium-rich regions. Layers without this microstructure were previously developed for nominally lattice-matched InAlN and have been developed here for higher indium content InAlN. In this study, InAlN was grown in a nitrogen-rich environment with high indium to aluminum flux ratios at low growth temperatures. Samples were characterized by high-resolution x-ray diffraction, atomic force microscopy, high-angle annular dark-field scanning transmission electron microscopy, and atom probe tomography. Atomic force microscopy showed InAlN layers grown at temperatures below 450 °C under nitrogen-rich conditions were free of droplets. InAlN films with indium contents up to 81% were grown at temperatures between 410 and 440 °C. High-angle annular dark-field scanning transmission electron microscopy and atom probe tomography showed no evidence of honeycomb microstructure for samples with indium contents of 34% and 62%. These layers are homogeneous and follow a random alloy distribution. A growth diagram for InAlN of all indium contents is reported.

Hydration and distance dependence of intermolecular shearing between collagen molecules in a model microfibril.

PubMed

Gautieri, Alfonso; Pate, Monica I; Vesentini, Simone; Redaelli, Alberto; Buehler, Markus J

2012-08-09

In vertebrates, collagen tissues are the main component responsible for force transmission. In spite of the physiological importance of these phenomena, force transmission mechanisms are still not fully understood, especially at smaller scales, including in particular collagen molecules and fibrils. Here we investigate the mechanism of molecular sliding between collagen molecules within a fibril, by shearing a central molecule in a hexagonally packed bundle mimicking the collagen microfibril environment, using varied lateral distance between the molecules in both dry and solvated conditions. In vacuum, the central molecule slides under a stick-slip mechanism that is due to the characteristic surface profile of collagen molecules, enhanced by the breaking and reformation of H-bonds between neighboring collagen molecules. This mechanism is consistently observed for varied lateral separations between molecules. The high shearing force (>7 nN) found for the experimentally observed intermolecular distance (≈1.1 nm) suggests that in dry samples the fibril elongation mechanism relies almost exclusively on molecular stretching, which may explain the higher stiffnesses found in dry fibrils. When hydrated, the slip-stick behavior is observed only below 1.3 nm of lateral distance, whereas above 1.3 nm the molecule shears smoothly, showing that the water layer has a strong lubricating effect. Moreover, the average force required to shear is approximately the same in solvated as in dry conditions (≈2.5 nN), which suggests that the role of water at the intermolecular level includes the transfer of load between molecules. Copyright © 2012 Elsevier Ltd. All rights reserved.

Differential expansion and expression of alpha- and beta-tubulin gene families in Populus.

PubMed

Oakley, Rodney V; Wang, Yuh-Shuh; Ramakrishna, Wusirika; Harding, Scott A; Tsai, Chung-Jui

2007-11-01

Microtubule organization is intimately associated with cellulose microfibril deposition, central to plant secondary cell wall development. We have determined that a relatively large suite of eight alpha-TUBULIN (TUA) and 20 beta-TUBULIN (TUB) genes is expressed in the woody perennial Populus. A number of features, including gene number, alpha:beta gene representation, amino acid changes at the C terminus, and transcript abundance in wood-forming tissue, distinguish the Populus tubulin suite from that of Arabidopsis thaliana. Five of the eight Populus TUAs are unusual in that they contain a C-terminal methionine, glutamic acid, or glutamine, instead of the more typical, and potentially regulatory, C-terminal tyrosine. Both C-terminal Y-type (TUA1) and M-type (TUA5) TUAs were highly expressed in wood-forming tissues and pollen, while the Y-type TUA6 and TUA8 were abundant only in pollen. Transcripts of the disproportionately expanded TUB family were present at comparatively low levels, with phylogenetically distinct classes predominating in xylem and pollen. When tension wood induction was used as a model system to examine changes in tubulin gene expression under conditions of augmented cellulose deposition, xylem-abundant TUA and TUB genes were up-regulated. Immunolocalization of TUA and TUB in xylem and phloem fibers of stems further supported the notion of heavy microtubule involvement during cellulose microfibril deposition in secondary walls. The high degree of sequence diversity, differential expansion, and differential regulation of Populus TUA and TUB families may confer flexibility in cell wall formation that is of adaptive significance to the woody perennial growth habit.

Endoglucanase Peripheral Loops Facilitate Complexation of Glucan Chains on Cellulose via Adaptive Coupling to the Emergent Substrate Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Yuchun; Beckham, Gregg T.; Himmel, Michael E.

We examine how the catalytic domain of a glycoside hydrolase family 7 endoglucanase catalytic domain (Cel7B CD) facilitates complexation of cellulose chains from a crystal surface. With direct relevance to the science of biofuel production, this problem also represents a model system of biopolymer processing by proteins in Nature. Interactions of Cel7B CD with a cellulose microfibril along different paths of complexation are characterized by mapping the atomistic fluctuations recorded in free-energy simulations onto the parameters of a coarse-grain model. The resulting patterns of protein-biopolymer couplings also uncover the sequence signatures of the enzyme in peeling off glucan chains frommore » the microfibril substrate. We show that the semiopen active site of Cel7B CD exhibits similar barriers and free energies of complexation over two distinct routes; namely, scooping of a chain into the active-site cleft and threading from the chain end into the channel. On the other hand, the complexation energetics strongly depends on the surface packing of the targeted chain and the resulting interaction sites with the enzyme. A revealed principle is that Cel7B CD facilitates cellulose deconstruction via adaptive coupling to the emergent substrate. The flexible, peripheral segments of the protein outside of the active-site cleft are able to accommodate the varying features of cellulose along the simulated paths of complexation. The general strategy of linking physics-based molecular interactions to protein sequence could also be helpful in elucidating how other protein machines process biopolymers.« less

MicroFilament Analyzer, an image analysis tool for quantifying fibrillar orientation, reveals changes in microtubule organization during gravitropism.

PubMed

Jacques, Eveline; Buytaert, Jan; Wells, Darren M; Lewandowski, Michal; Bennett, Malcolm J; Dirckx, Joris; Verbelen, Jean-Pierre; Vissenberg, Kris

2013-06-01

Image acquisition is an important step in the study of cytoskeleton organization. As visual interpretations and manual measurements of digital images are prone to errors and require a great amount of time, a freely available software package named MicroFilament Analyzer (MFA) was developed. The goal was to provide a tool that facilitates high-throughput analysis to determine the orientation of filamentous structures on digital images in a more standardized, objective and repeatable way. Here, the rationale and applicability of the program is demonstrated by analyzing the microtubule patterns in epidermal cells of control and gravi-stimulated Arabidopsis thaliana roots. Differential expansion of cells on either side of the root results in downward bending of the root tip. As cell expansion depends on the properties of the cell wall, this may imply a differential orientation of cellulose microfibrils. As cellulose deposition is orchestrated by cortical microtubules, the microtubule patterns were analyzed. The MFA program detects the filamentous structures on the image and identifies the main orientation(s) within individual cells. This revealed four distinguishable microtubule patterns in root epidermal cells. The analysis indicated that gravitropic stimulation and developmental age are both significant factors that determine microtubule orientation. Moreover, the data show that an altered microtubule pattern does not precede differential expansion. Other possible applications are also illustrated, including field emission scanning electron micrographs of cellulose microfibrils in plant cell walls and images of fluorescent actin. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

A single heterologously expressed plant cellulose synthase isoform is sufficient for cellulose microfibril formation in vitro

PubMed Central

Purushotham, Pallinti; Cho, Sung Hyun; Díaz-Moreno, Sara M.; Kumar, Manish; Nixon, B. Tracy; Bulone, Vincent; Zimmer, Jochen

2016-01-01

Plant cell walls are a composite material of polysaccharides, proteins, and other noncarbohydrate polymers. In the majority of plant tissues, the most abundant polysaccharide is cellulose, a linear polymer of glucose molecules. As the load-bearing component of the cell wall, individual cellulose chains are frequently bundled into micro and macrofibrils and are wrapped around the cell. Cellulose is synthesized by membrane-integrated and processive glycosyltransferases that polymerize UDP-activated glucose and secrete the nascent polymer through a channel formed by their own transmembrane regions. Plants express several different cellulose synthase isoforms during primary and secondary cell wall formation; however, so far, none has been functionally reconstituted in vitro for detailed biochemical analyses. Here we report the heterologous expression, purification, and functional reconstitution of Populus tremula x tremuloides CesA8 (PttCesA8), implicated in secondary cell wall formation. The recombinant enzyme polymerizes UDP-activated glucose to cellulose, as determined by enzyme degradation, permethylation glycosyl linkage analysis, electron microscopy, and mutagenesis studies. Catalytic activity is dependent on the presence of a lipid bilayer environment and divalent manganese cations. Further, electron microscopy analyses reveal that PttCesA8 produces cellulose fibers several micrometers long that occasionally are capped by globular particles, likely representing PttCesA8 complexes. Deletion of the enzyme’s N-terminal RING-finger domain almost completely abolishes fiber formation but not cellulose biosynthetic activity. Our results demonstrate that reconstituted PttCesA8 is not only sufficient for cellulose biosynthesis in vitro but also suffices to bundle individual glucan chains into cellulose microfibrils. PMID:27647898

The pattern of xylan acetylation suggests xylan may interact with cellulose microfibrils as a twofold helical screw in the secondary plant cell wall of Arabidopsis thaliana

PubMed Central

Busse-Wicher, Marta; Gomes, Thiago C F; Tryfona, Theodora; Nikolovski, Nino; Stott, Katherine; Grantham, Nicholas J; Bolam, David N; Skaf, Munir S; Dupree, Paul

2014-01-01

The interaction between xylan and cellulose microfibrils is important for secondary cell wall properties in vascular plants; however, the molecular arrangement of xylan in the cell wall and the nature of the molecular bonding between the polysaccharides are unknown. In dicots, the xylan backbone of β-(1,4)-linked xylosyl residues is decorated by occasional glucuronic acid, and approximately one-half of the xylosyl residues are O-acetylated at C-2 or C-3. We recently proposed that the even, periodic spacing of GlcA residues in the major domain of dicot xylan might allow the xylan backbone to fold as a twofold helical screw to facilitate alignment along, and stable interaction with, cellulose fibrils; however, such an interaction might be adversely impacted by random acetylation of the xylan backbone. Here, we investigated the arrangement of acetyl residues in Arabidopsis xylan using mass spectrometry and NMR. Alternate xylosyl residues along the backbone are acetylated. Using molecular dynamics simulation, we found that a twofold helical screw conformation of xylan is stable in interactions with both hydrophilic and hydrophobic cellulose faces. Tight docking of xylan on the hydrophilic faces is feasible only for xylan decorated on alternate residues and folded as a twofold helical screw. The findings suggest an explanation for the importance of acetylation for xylan–cellulose interactions, and also have implications for our understanding of cell wall molecular architecture and properties, and biological degradation by pathogens and fungi. They will also impact strategies to improve lignocellulose processing for biorefining and bioenergy. PMID:24889696

A single heterologously expressed plant cellulose synthase isoform is sufficient for cellulose microfibril formation in vitro.

PubMed

Purushotham, Pallinti; Cho, Sung Hyun; Díaz-Moreno, Sara M; Kumar, Manish; Nixon, B Tracy; Bulone, Vincent; Zimmer, Jochen

2016-10-04

Plant cell walls are a composite material of polysaccharides, proteins, and other noncarbohydrate polymers. In the majority of plant tissues, the most abundant polysaccharide is cellulose, a linear polymer of glucose molecules. As the load-bearing component of the cell wall, individual cellulose chains are frequently bundled into micro and macrofibrils and are wrapped around the cell. Cellulose is synthesized by membrane-integrated and processive glycosyltransferases that polymerize UDP-activated glucose and secrete the nascent polymer through a channel formed by their own transmembrane regions. Plants express several different cellulose synthase isoforms during primary and secondary cell wall formation; however, so far, none has been functionally reconstituted in vitro for detailed biochemical analyses. Here we report the heterologous expression, purification, and functional reconstitution of Populus tremula x tremuloides CesA8 (PttCesA8), implicated in secondary cell wall formation. The recombinant enzyme polymerizes UDP-activated glucose to cellulose, as determined by enzyme degradation, permethylation glycosyl linkage analysis, electron microscopy, and mutagenesis studies. Catalytic activity is dependent on the presence of a lipid bilayer environment and divalent manganese cations. Further, electron microscopy analyses reveal that PttCesA8 produces cellulose fibers several micrometers long that occasionally are capped by globular particles, likely representing PttCesA8 complexes. Deletion of the enzyme's N-terminal RING-finger domain almost completely abolishes fiber formation but not cellulose biosynthetic activity. Our results demonstrate that reconstituted PttCesA8 is not only sufficient for cellulose biosynthesis in vitro but also suffices to bundle individual glucan chains into cellulose microfibrils.

The growing outer epidermal wall: design and physiological role of a composite structure.

PubMed

Kutschera, U

2008-04-01

The cells of growing plant organs secrete an extracellular fibrous composite (the primary wall) that allows the turgid protoplasts to expand irreversibly via wall-yielding events, which are regulated by processes within the cytoplasm. The role of the epidermis in the control of stem elongation is described with special reference to the outer epidermal wall (OEW), which forms a 'tensile skin'. The OEW is much thicker and less extensible than the walls of the inner tissues. Moreover, in the OEW the amount of cellulose per unit wall mass is considerably greater than in the inner tissues. Ultrastructural studies have shown that the expanding OEW is composed of a highly ordered internal and a diffuse outer half, with helicoidally organized cellulose microfibrils in the inner (load-bearing) region of this tension-stressed organ wall. The structural and mechanical backbone of the wall consists of helicoids, i.e. layers of parallel, inextensible cellulose microfibrils. These 'plywood laminates' contain crystalline 'cables' orientated in all directions with respect to the axis of elongation (isotropic material). Cessation of cell elongation is accompanied by a loss of order, i.e. the OEW is a dynamic structure. Helicoidally arranged extracellular polymers have also been found in certain bacteria, algae, fungi and animals. In the insect cuticle crystalline cutin nanofibrils form characteristic 'OEW-like' herringbone patterns. Theoretical considerations, in vitro studies and computer simulations suggest that extracellular biological helicoids form by directed self-assembly of the crystalline biopolymers. This spontaneous generation of complex design 'without an intelligent designer' evolved independently in the protective 'skin' of plants, animals and many other organisms.

Improvement of thermal and mechanical properties of composite based on polylactic acid and microfibrillated cellulose through chemical modification

NASA Astrophysics Data System (ADS)

Suryanegara, L.; Nugraha, R. A.; Achmadi, S. S.

2017-07-01

Polylactic acid (PLA) is the most representative sustainable and bio-based polymer environmentally friendly that has a great potential to replace petroleum-based plastics. However, brittleness, low heat resistance, and slow crystallization limit the wide application of PLA. One of strategies to improve PLA properties is by reinforcing with microfibrillated cellulose (MFC). Unfortunately, the hydrophilic properties of MFC make it difficult to attain good dispersion in a hydrophobic PLA matrix. Therefore, modification of MFC was needed to increase its compatibility with PLA in the composite formation. In this experiment, MFC was modified with partial acetylation (degree of substitution: 1) and further grafted with lactide monomers through ring-opening polymerization using Sn(Oct)2 catalyst. The result of acetylation and grafting were verified by infrared spectra. Composites were prepared by mixing PLA (molecular weight of 200,000) and the modified MFC at 9:1 ratio through organic solvent method. Followed by 8 min-kneading and hot pressing at 180°C, the resulted composites were evaluated for their mechanical and thermal properties. Thermal characterization carried out using differential scanning calorimetry measurements showed that the presence of modified MFC increased the temperature of glass transition and accelerated the crystallization of PLA. Mechanical properties measurement showed that the presence of modified MFC enhanced the elongation at break (1.1 to 1.8%), tensile strength (14.9 to 25.7 MPa), and modulus of elasticity (1.7 to 2.1 GPa). These results demonstrated that the modified MFC could extend the application of PLA in industry.

Controlled release of chlorhexidine digluconate using β-cyclodextrin and microfibrillated cellulose.

PubMed

Lavoine, Nathalie; Tabary, Nicolas; Desloges, Isabelle; Martel, Bernard; Bras, Julien

2014-09-01

This study aims to develop a high-performance delivery system using microfibrillated cellulose (MFC)-coated papers as a controlled release system combined with the well-known drug delivery agent, β-cyclodextrin (βCD). Chlorhexidine digluconate (CHX), an antibacterial molecule, was mixed with a suspension of MFC or a βCD solution or mixed with both the substances, before coating onto a cellulosic substrate. The intermittent diffusion of CHX (i.e., diffusion interrupted by the renewal of the release medium periodically) was conducted in an aqueous medium, and the release mechanism of CHX was elucidated by field emission gun-scanning electron microscopy, SEM, NMR, and Fourier transform infrared analyses. According to the literature, both βCD and MFC are efficient controlled delivery systems. This study indicated that βCD releases CHX more gradually and over a longer period of time compared to MFC, which is mainly due to the ability of βCD to form an inclusion complex with CHX. Furthermore from the release study, a complementary action when the two compounds were combined was deduced. MFC mainly affected the burst effect, while βCD primarily controlled the amount of CHX released over time. In this paper, two different types of controlled release systems are proposed and compared. Depending on the final application, the use of βCD alone would release low amounts of active molecules over time (slow delivery), whereas the combination of β-cyclodextrin and MFC would be more suitable for the release of higher amounts of active molecules over time (rapid delivery). Copyright © 2014 Elsevier B.V. All rights reserved.

FIRE_CI2_CITATN_1HZ

Atmospheric Science Data Center

2015-11-25

... Flow Angle Sensors Hot-Wire Icing Rate Detector Pressure Transducer Reverse Flow Temperature Probes Spatial ... Condensation Nuclei Dew/Frost Point Temperature Liquid Water Content Nitrogen Dioxide Ozone Pressure Supercooled ...

Feeling stretched or compressed? The multiple mechanosensitive responses of wood formation to bending.

PubMed

Roignant, Jeanne; Badel, Éric; Leblanc-Fournier, Nathalie; Brunel-Michac, Nicole; Ruelle, Julien; Moulia, Bruno; Decourteix, Mélanie

2018-05-11

Trees constantly experience wind, perceive resulting mechanical cues, and modify their growth and development accordingly. Previous studies have demonstrated that multiple bending treatments trigger ovalization of the stem and the formation of flexure wood in gymnosperms, but ovalization and flexure wood have rarely been studied in angiosperms, and none of the experiments conducted so far has used multidirectional bending treatments at controlled intensities. Assuming that bending involves tensile and compressive strain, we hypothesized that different local strains may generate specific growth and wood differentiation responses. Basal parts of young poplar stems were subjected to multiple transient controlled unidirectional bending treatments during 8 weeks, which enabled a distinction to be made between the wood formed under tensile or compressive flexural strains. This set-up enabled a local analysis of poplar stem responses to multiple stem bending treatments at growth, anatomical, biochemical and molecular levels. In response to multiple unidirectional bending treatments, poplar stems developed significant cross-sectional ovalization. At the tissue level, some aspects of wood differentiation were similarly modulated in the compressed and stretched zones (vessel frequency and diameter of fibres without a G-layer), whereas other anatomical traits (vessel diameter, G-layer formation, diameter of fibres with a G-layer and microfibril angle) and the expression of fasciclin-encoding genes were differentially modulated in the two zones. This work leads us to propose new terminologies to distinguish the 'flexure wood' produced in response to multiple bidirectional bending treatments from wood produced under transient tensile strain (tensile flexure wood; TFW) or under transient compressive strain (compressive flexure wood; CFW). By highlighting similarities and differences between tension wood and TFW and by demonstrating that plants could have the ability to discriminate positive strains from negative strains, this work provides new insight into the mechanisms of mechanosensitivity in plants.

The Influence of SAND’s Gradation and Clay Content of Direct Sheart Test on Clayey Sand

NASA Astrophysics Data System (ADS)

Wibisono, Gunawan; Agus Nugroho, Soewignjo; Umam, Khairul

2018-03-01

The shear strength of clayey-sand can be affected by several factors, e.g. gradation, density, moisture content, and the percentage of clay and sand fraction. The same percentage of clay and sand fraction in clayey-sand mixtures may have different shear strengths due to those factors. This research aims to study the effect of clay content on sand that cause the change of its shear strength. Samples consisted of different clay and sand fractions were reconstituted at a certain moisture content. Sand fractions varied from well-graded to poorly-graded sand. Shear strength was measured in terms of the direct shear test. Prior to the test, surcharge loads were applied to represent overburden pressures. Shear strength results and their components (i.e. Cohesion and internal angle of friction) were correlated with physical properties of samples (i.e. grading coefficient of curvature, coefficient of uniformity, and density). Results showed that samples classified as well-graded and dense sand had higher shear strength. In the other hand, the shear strengths decreased when the mixtures became poorly-graded and less dense. The inclusion of the clay fraction increased cohesion component and decreased internal angle of friction.

The parallel lives of microtubules and cellulose microfibrils.

PubMed

Lloyd, Clive; Chan, Jordi

2008-12-01

A major breakthrough was the recent discovery that cellulose synthases really do move along the plasma membrane upon tracks provided by the underlying cortical microtubules. It emphasized the cytoplasmic contribution to cell wall organization. A growing number of microtubule-associated proteins has been identified and shown to affect the way that microtubules are ordered, with downstream effects on the pattern of growth. The dynamic properties of microtubules turn out to be key in understanding the behaviour of the global array and good progress has been made in deciphering the rules by which the array is self-organized.

Helicoidal pattern in secondary cell walls and possible role of xylans in their construction.

PubMed

Reis, Danièle; Vian, Brigitte

2004-01-01

The helicoidal organization of secondary cell walls is overviewed from several examples. Both the plywood texture and the occurrence of characteristic defects strongly suggest that the wall ordering is relevant of a cholesteric liquid-crystal assembly that is rapidly and strongly consolidated by lignification. A preferential localization of glucuronoxylans, major matrix components, and in vitro re-association experiments emphasize their preeminent role: (1) during the construction of the composite as directing the cellulose microfibrils in a helicoidal array; (2) during the lignification of the composite as a host structure for lignin precursors.

Software and database for the analysis of mutations in the human FBN1 gene.

PubMed Central

Collod, G; Béroud, C; Soussi, T; Junien, C; Boileau, C

1996-01-01

Fibrillin is the major component of extracellular microfibrils. Mutations in the fibrillin gene on chromosome 15 (FBN1) were described at first in the heritable connective tissue disorder, Marfan syndrome (MFS). More recently, FBN1 has also been shown to harbor mutations related to a spectrum of conditions phenotypically related to MFS and many mutations will have to be accumulated before genotype/phenotype relationships emerge. To facilitate mutational analysis of the FBN1 gene, a software package along with a computerized database (currently listing 63 entries) have been created. PMID:8594563

Adhesion enhancement of biomimetic dry adhesives by nanoparticle in situ synthesis

NASA Astrophysics Data System (ADS)

Díaz Téllez, J. P.; Harirchian-Saei, S.; Li, Y.; Menon, C.

2013-10-01

A novel method to increase the adhesion strength of a gecko-inspired dry adhesive is presented. Gold nanoparticles are synthesized on the tips of the microfibrils of a polymeric dry adhesive to increase its Hamaker constant. Formation of the gold nanoparticles is qualitatively studied through a colour change in the originally transparent substance and quantitatively analysed using ultraviolet-visible spectrophotometry. A pull-off force test is employed to quantify the adhesion enhancement. Specifically, adhesion forces of samples with and without embedded gold nanoparticles are measured and compared. The experimental results indicate that an adhesion improvement of 135% can be achieved.

Tip-path-plane angle effects on rotor blade-vortex interaction noise levels and directivity

NASA Technical Reports Server (NTRS)

Burley, Casey L.; Martin, Ruth M.

1988-01-01

Acoustic data of a scale model BO-105 main rotor acquired in a large aeroacoustic wind tunnel are presented to investigate the parametric effects of rotor operating conditions on blade-vortex interaction (BVI) impulsive noise. Contours of a BVI noise metric are employed to quantify the effects of rotor advance ratio and tip-path-plane angle on BVI noise directivity and amplitude. Acoustic time history data are presented to illustrate the variations in impulsive characteristics. The directionality, noise levels and impulsive content of both advancing and retreating side BVI are shown to vary significantly with tip-path-plane angle and advance ratio over the range of low and moderate flight speeds considered.

Comparison of animal discs used in disc research to human lumbar disc: torsion mechanics and collagen content.

PubMed

Showalter, Brent L; Beckstein, Jesse C; Martin, John T; Beattie, Elizabeth E; Espinoza Orías, Alejandro A; Schaer, Thomas P; Vresilovic, Edward J; Elliott, Dawn M

2012-07-01

Experimental measurement and normalization of in vitro disc torsion mechanics and collagen content for several animal species used in intervertebral disc research and comparing these with the human disc. To aid in the selection of appropriate animal models for disc research by measuring torsional mechanical properties and collagen content. There is lack of data and variability in testing protocols for comparing animal and human disc torsion mechanics and collagen content. Intervertebral disc torsion mechanics were measured and normalized by disc height and polar moment of inertia for 11 disc types in 8 mammalian species: the calf, pig, baboon, goat, sheep, rabbit, rat, and mouse lumbar discs, and cow, rat, and mouse caudal discs. Collagen content was measured and normalized by dry weight for the same discs except the rat and the mouse. Collagen fiber stretch in torsion was calculated using an analytical model. Measured torsion parameters varied by several orders of magnitude across the different species. After geometric normalization, only the sheep and pig discs were statistically different from human discs. Fiber stretch was found to be highly dependent on the assumed initial fiber angle. The collagen content of the discs was similar, especially in the outer annulus where only the calf and goat discs were statistically different from human. Disc collagen content did not correlate with torsion mechanics. Disc torsion mechanics are comparable with human lumbar discs in 9 of 11 disc types after normalization by geometry. The normalized torsion mechanics and collagen content of the multiple animal discs presented are useful for selecting and interpreting results for animal disc models. Structural organization of the fiber angle may explain the differences that were noted between species after geometric normalization.

Comparison of Animal Discs Used in Disc Research to Human Lumbar Disc: Torsion Mechanics and Collagen Content

PubMed Central

Showalter, Brent L.; Beckstein, Jesse C.; Martin, John T.; Beattie, Elizabeth E.; Orías, Alejandro A. Espinoza; Schaer, Thomas P.; Vresilovic, Edward J.; Elliott, Dawn M.

2012-01-01

Study Design Experimental measurement and normalization of in vitro disc torsion mechanics and collagen content for several animal species used in intervertebral disc research and comparing these to the human disc. Objective To aid in the selection of appropriate animal models for disc research by measuring torsional mechanical properties and collagen content. Summary of Background Data There is lack of data and variability in testing protocols for comparing animal and human disc torsion mechanics and collagen content. Methods Intervertebral disc torsion mechanics were measured and normalized by disc height and polar moment of inertia for 11 disc types in 8 mammalian species: the calf, pig, baboon, goat, sheep, rabbit, rat, and mouse lumbar, and cow, rat, and mouse caudal. Collagen content was measured and normalized by dry weight for the same discs except the rat and mouse. Collagen fiber stretch in torsion was calculated using an analytical model. Results Measured torsion parameters varied by several orders of magnitude across the different species. After geometric normalization, only the sheep and pig discs were statistically different from human. Fiber stretch was found to be highly dependent on the assumed initial fiber angle. The collagen content of the discs was similar, especially in the outer annulus where only the calf and goat discs were statistically different from human. Disc collagen content did not correlate with torsion mechanics. Conclusion Disc torsion mechanics are comparable to human lumbar discs in 9 of 11 disc types after normalization by geometry. The normalized torsion mechanics and collagen content of the multiple animal discs presented is useful for selecting and interpreting results for animal models of the disc. Structural composition of the disc, such as initial fiber angle, may explain the differences that were noted between species after geometric normalization. PMID:22333953

Spray formation of biodiesel-water in air-assisted atomizer using Schlieren photography

NASA Astrophysics Data System (ADS)

Amirnordin, S. H.; Khalid, A.; Sapit, A.; Salleh, H.; Razali, A.; Fawzi, M.

2016-11-01

Biodiesels are attractive renewable energy sources, particularly for industrial boiler and burner operators. However, biodiesels produce higher nitrogen oxide (NOx) emissions compared with diesel. Although water-emulsified fuels can lower NOx emissions by reducing flame temperature, its influence on atomization needs to be investigated further. This study investigates the effects of water on spray formation in air-assisted atomizers. The Schlieren method was used to capture the spray images in terms of tip penetration, spray angle, and spray area. The experiment used palm oil biodiesel at different blending ratios (B5, B10, and B15) and water contents (0vol%-15vol%). Results show that water content in the fuel increases the spray penetration and area but reduces the spray angle because of the changes in fuel properties. Therefore, biodiesel-water application is applicable to burner systems.

Effect of Ambient Temperature on Hydrophobic Recovery Behavior of Silicone Rubber Composites

NASA Astrophysics Data System (ADS)

Peng, Xiangyang; Li, Zijian; Zheng, Feng; Zhang, Ni; Huang, Zhen; Fang, Pengfei

A series of silicone rubber samples with different cyclosiloxanes contents have been successfully prepared, and their hydrophobic recovery behaviors and mechanism were investigated in detail. The gas chromatography-mass spectroscopy technique after Soxhlet extraction was utilized to examine the low molecular weight siloxanes in the sample, SEM was used to observe the surface morphology of the silicone rubber influenced by plasma treatment, and contact angle measurement was applied to probe the hydrophobic recovery of the sample surface after plasma treatment at different storage temperatures. The storage time-dependent contact angle of water can be well fitted by the diffusion model calculated from Fick’s second law. The results imply that the hydrophobic recovery of silicone rubber is related to the diffusion of low molecular weight siloxanes, while larger content or higher temperature can induce faster hydrophobic recovery.

A Unit-Cell Model for Predicting the Elastic Constants of 3D Four Directional Cylindrical Braided Composite Shafts

NASA Astrophysics Data System (ADS)

Hao, Wenfeng; Liu, Ye; Huang, Xinrong; Liu, Yinghua; Zhu, Jianguo

2018-06-01

In this work, the elastic constants of 3D four directional cylindrical braided composite shafts were predicted using analytical and numerical methods. First, the motion rule of yarn carrier of 3D four directional cylindrical braided composite shafts was analyzed, and the horizontal projection of yarn motion trajectory was obtained. Then, the geometry models of unit-cells with different braiding angles and fiber volume contents were built up, and the meso-scale models of 3D cylindrical braided composite shafts were obtained. Finally, the effects of braiding angles and fiber volume contents on the elastic constants of 3D braided composite shafts were analyzed theoretically and numerically. These results play a crucial role in investigating the mechanical properties of 3D 4-directional braided composites shafts.

Diagenetic and compositional controls of wettability in siliceous sedimentary rocks, Monterey Formation, California

NASA Astrophysics Data System (ADS)

Hill, Kristina M.

Modified imbibition tests were performed on 69 subsurface samples from Monterey Formation reservoirs in the San Joaquin Valley to measure wettability variation as a result of composition and silica phase change. Contact angle tests were also performed on 6 chert samples from outcrop and 3 nearly pure mineral samples. Understanding wettability is important because it is a key factor in reservoir fluid distribution and movement, and its significance rises as porosity and permeability decrease and fluid interactions with reservoir grain surface area increase. Although the low permeability siliceous reservoirs of the Monterey Formation are economically important and prolific, a greater understanding of factors that alter their wettability will help better develop them. Imbibition results revealed a strong trend of decreased wettability to oil with increased detrital content in opal-CT phase samples. Opal-A phase samples exhibited less wettability to oil than both opal-CT and quartz phase samples of similar detrital content. Subsurface reservoir samples from 3 oil fields were crushed to eliminate the effect of capillary pressure and cleansed of hydrocarbons to eliminate wettability alterations by asphaltene, then pressed into discs of controlled density. Powder discs were tested for wettability by dispensing a controlled volume of water and motor oil onto the surface and measuring the time required for each fluid to imbibe into the sample. The syringe and software of a CAM101 tensiometer were used to control the amount of fluid dispensed onto each sample, and imbibition completion times were determined by high-speed photography for water drops; oil drop imbibition was significantly slower and imbibition was timed and determined visually. Contact angle of water and oil drops on polished chert and mineral sample surfaces was determined by image analysis and the Young-Laplace equation. Oil imbibition was significantly slower with increased detrital composition and faster with increased silica content in opal-CT and quartz phase samples, implying decreased wettability to oil with increased detrital (clay) content. However, contact angle tests showed that opal-CT is more wetting to oil with increased detritus and results for oil on quartz-phase samples were inconsistent between different proxies for detritus over their very small compositional range. Water contact angle trends also showed inconsistent wetting trends compared to imbibition tests. We believe this is because the small range in bulk detrital composition between the "pure" samples used in contact angle tests was close to analytical error and because small-scale spatial compositional variability may be significant enough to effect wettability. These experiments show that compositional variables significantly affect wettability, outweighing the effect of silica phase.

A Method for Computing Three-Dimensional Viscous Flows over an Ogival Body at Angle of Attack

DTIC Science & Technology

1976-02-01

the ogival body problems; however, some gen- erality is still maintained by considering coordinate systems that are generated from any two ...transformation. We shall assume that the covariant derivative is the natural one derivable from the metric. This is known as the Levi - Civita connection (Ref...MV..»^^.^ R76-91202^-8 I A Method for Computing Three-Dimensional Viscoua Flows Over an Ogival Body at Angle of Attack TABLE OF CONTENTS

Fabrication of superhydrophobic film by microcellular plastic foaming method

NASA Astrophysics Data System (ADS)

Zhang, Zhen Xiu; Li, Ya Nan; Xia, Lin; Ma, Zhen Guo; Xin, Zhen Xiang; Kim, Jin Kuk

2014-08-01

To solve the complicated manufacturing operation and the usage of toxic solvent problems, a simple and novel method to fabricate superhydrophobic film by surface foaming method was introduced in this paper. The superhydrophobic property of the foamed material was obtained at a contact angle >150° and a rolling angle about 8°. The foamed material can instantly generate its superhydrophobicity via peeling process. The effects of blowing agent content, foaming time and peeling rate on the foam structure and superhydrophobicity were studied.

Cross-Grain Knife Planing Improves Surface Quality and Utilization of Aspen

Treesearch

Harold A. Stewart

1971-01-01

Aspen at 6 percent moisture content was planed parallel to the grain and across the grain on a cabinet planer with a 25? rake angle, 1/16- and 1/32-inch depth of cut, and 20 knife marks per inch. Aspen was also cross-grain knife planed with a 45? rake angle, 1/32-, 1/16-, and 1/8-inch depths of cut, and 20, 10, 5, and 2.5 knife marks per inch. Cross-grain knife...

Effects of Compression, Staging, and Braid Angle on Braided Rope Seal Performance

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.; Dunlap, Patrick H.; Adams, Michael L.

2006-01-01

This viewgraph presentation describes the effects of compression, staging and braid angle on braided rope seals. The contents include: 1) Test Fixture Schematics; 2) Comparison of Hybrid Seal Braid Architecture; 3) Residual Interference After Compression Cycling; 4) Effect of Compression, Braid, and Staging on Seal Flow; 5) Effect of Staging on Seal Pressure Drop; 6) Three Stag Seal Durability; 7) P&W Turbine Vane Seal Requirements; and 8) Next Generation Fighter F-22 P&W F119 Engines.

Influence of moisture content on physical properties of minor millets.

PubMed

Balasubramanian, S; Viswanathan, R

2010-06-01

Physical properties including 1000 kernel weight, bulk density, true density, porosity, angle of repose, coefficient of static friction, coefficient of internal friction and grain hardness were determined for foxtail millet, little millet, kodo millet, common millet, barnyard millet and finger millet in the moisture content range of 11.1 to 25% db. Thousand kernel weight increased from 2.3 to 6.1 g and angle of repose increased from 25.0 to 38.2°. Bulk density decreased from 868.1 to 477.1 kg/m(3) and true density from 1988.7 to 884.4 kg/m(3) for all minor millets when observed in the moisture range of 11.1 to 25%. Porosity decreased from 63.7 to 32.5%. Coefficient of static friction of minor millets against mild steel surface increased from 0.253 to 0.728 and coefficient of internal friction was in the range of 1.217 and 1.964 in the moisture range studied. Grain hardness decreased from 30.7 to 12.4 for all minor millets when moisture content was increased from 11.1 to 25% db.

Undrained behavior and shear strength of clean sand containing low-plastic fines

NASA Astrophysics Data System (ADS)

To-Anh Phan, Vu; Hsiao, Darn-Horng

2018-04-01

This study presents experimental tests to understand the undrained behavior of sand containing various fines contents. The specimens were prepared by the wet tamping method. The consolidated undrained triaxial shear tests were carried out by sands mixed with amounts of fines in ranging from 0 to 60%. The results showed that the deviator stress quickly reaches the peak value with an axial strain in a range of 0.5 to 2%, and then, the value drops significantly with further increases in the axial strain, the pore water pressure of all the sand-fines mixtures rapidly increases as the axial strain reaches a value in a range from 1 to 2% and then slowly increases and reaches a stable state when strain is greater than 8%. Peak deviator stress gradually decreases with an increasing fines content from 0 to 40%, thereafter, the peak deviator significantly increases with further increases in the fines content up to 60%, irrespective of confining pressure values using in these tests. Finally, the effective internal friction angles are remarkably greater than the total friction angles for various sand-fines mixtures.

VHF/UHF technique for the determination of the columnar electron contents of the plasmasphere and of the protonosphere using geostationary satellite transmission: Observations during magnetic storms

NASA Technical Reports Server (NTRS)

Almeida, O. G.

1972-01-01

Measurements of the total electron content of the plasmasphere up to geostationary heights were made using the beacon transmitters aboard the satellite ATS-3. The technique employed is a combination of the phase-path length difference and the Faraday rotation angle methods. Such a combination permits very accurate determination of the integration constant necessary to convert phase-path length difference data into information about the absolute value of the columnar content.

Anatomic Characteristics Associated with Head Splitting in Cabbage (Brassica oleracea var. capitata L.)

PubMed Central

Li, Xiaonan; Choi, Su Ryun; Wang, Yunbo; Sung, Chang-keun; Im, Subin; Ramchiary, Nirala; Zhou, Guangsheng; Lim, Yong Pyo

2015-01-01

Cabbage belonging to Brassicaceae family is one of the most important vegetables cultivated worldwide. The economically important part of cabbage crop is head, formed by leaves which may be of splitting and non-splitting types. Cabbage varieties showing head splitting causes huge loss to the farmers and therefore finding the molecular and structural basis of splitting types would be helpful to breeders. To determine which anatomical characteristics were related to head-splitting in cabbage, we analyzed two contrasting cabbage lines and their offspring using a field emission scanning electron microscope. The inbred line “747” is an early head-splitting type, while the inbred line “748” is a head-splitting-resistant type. The petiole cells of “747” seems to be larger than those of “748” at maturity; however, there was no significant difference in petiole cell size at both pre-heading and maturity stages. The lower epidermis cells of “747” were larger than those of “748” at the pre-heading and maturity stages. “747” had thinner epidermis cell wall than “748” at maturity stage, however, there was no difference of the epidermis cell wall thickness in the two lines at the pre-heading stage. The head-splitting plants in the F1 and F2 population inherited the larger cell size and thinner cell walls of epidermis cells in the petiole. In the petiole cell walls of “747” and the F1 and F2 plants that formed splitting heads, the cellulose microfibrils were loose and had separated from each other. These findings verified that anomalous cellulose microfibrils, larger cell size and thinner-walled epidermis cells are important genetic factors that make cabbage heads prone to splitting. PMID:26536356

Evolution of Xylan Substitution Patterns in Gymnosperms and Angiosperms: Implications for Xylan Interaction with Cellulose1[CC-BY

PubMed Central

Li, An; Gomes, Thiago C.F.

2016-01-01

The interaction between cellulose and xylan is important for the load-bearing secondary cell wall of flowering plants. Based on the precise, evenly spaced pattern of acetyl and glucuronosyl (MeGlcA) xylan substitutions in eudicots, we recently proposed that an unsubstituted face of xylan in a 2-fold helical screw can hydrogen bond to the hydrophilic surfaces of cellulose microfibrils. In gymnosperm cell walls, any role for xylan is unclear, and glucomannan is thought to be the important cellulose-binding polysaccharide. Here, we analyzed xylan from the secondary cell walls of the four gymnosperm lineages (Conifer, Gingko, Cycad, and Gnetophyta). Conifer, Gingko, and Cycad xylan lacks acetylation but is modified by arabinose and MeGlcA. Interestingly, the arabinosyl substitutions are located two xylosyl residues from MeGlcA, which is itself placed precisely on every sixth xylosyl residue. Notably, the Gnetophyta xylan is more akin to early-branching angiosperms and eudicot xylan, lacking arabinose but possessing acetylation on alternate xylosyl residues. All these precise substitution patterns are compatible with gymnosperm xylan binding to hydrophilic surfaces of cellulose. Molecular dynamics simulations support the stable binding of 2-fold screw conifer xylan to the hydrophilic face of cellulose microfibrils. Moreover, the binding of multiple xylan chains to adjacent planes of the cellulose fibril stabilizes the interaction further. Our results show that the type of xylan substitution varies, but an even pattern of xylan substitution is maintained among vascular plants. This suggests that 2-fold screw xylan binds hydrophilic faces of cellulose in eudicots, early-branching angiosperm, and gymnosperm cell walls. PMID:27325663

Disruption of cellulose synthesis by 2,6-dichlorobenzonitrile affects the structure of the cytoskeleton and cell wall construction in Arabidopsis.

PubMed

Peng, L; Zhang, L; Cheng, X; Fan, L-S; Hao, H-Q

2013-03-01

Cellulose is the major component of plant cell walls and is an important source of industrial raw material. Although cellulose biosynthesis is one of the most important biochemical processes in plant biology, the regulatory mechanisms of cellulose synthesis are still unclear. Here, we report that 2,6-dichlorobenzonitrile (DCB), an inhibitor of cellulose synthesis, inhibits Arabidopsis root development in a dose- and time-dependent manner. When treated with DCB, the plant cell wall showed altered cellulose distribution and intensity, as shown by calcofluor white and S4B staining. Moreover, pectin deposition was reduced in the presence of DCB when immunostained with the monoclonal antibody JIM5, which was raised against pectin epitopes. This result was confirmed using Fourier transform infrared (FTIR) analysis. Confocal microscopy revealed that the organisation of the microtubule cytoskeleton was significantly disrupted in the presence of low concentrations of DCB, whereas the actin cytoskeleton only showed changes with the application of high DCB concentrations. In addition, the subcellular dynamics of Golgi bodies labelled with N-ST-YFP and TGN labelled with VHA-a1-GFP were both partially blocked by DCB. Transmission electron microscopy indicated that the cell wall structure was affected by DCB, as were the Golgi bodies. Scanning electron microscopy showed changes in the organisation of cellulose microfibrils. These results suggest that the inhibition of cellulose synthesis by DCB not only induced changes in the chemical composition of the root cell wall and cytoskeleton structure, but also changed the distribution of cellulose microfibrils, implying that cellulose plays an important role in root development in Arabidopsis. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

Cellulose nanowhiskers and nanofibers from biomass for composite applications

NASA Astrophysics Data System (ADS)

Wang, Tao

2011-12-01

Biological nanocomposites such as plant cell wall exhibit high mechanical properties at a light weight. The secret of the rigidity and strength of the cell wall lies in its main structural component -- cellulose. Native cellulose exists as highly-ordered microfibrils, which are just a few nanometers wide and have been found to be stiffer than many synthetic fibers. In the quest for sustainable development around the world, using cellulose microfibrils from plant materials as renewable alternatives to conventional reinforcement materials such as glass fibers and carbon fibers is generating particular interest. In this research, by mechanical disintegration and by controlled chemical hydrolysis, both cellulose nanofibers and nanowhiskers were extracted from the cell wall of an agricultural waste, wheat straw. The reinforcement performances of the two nanofillers were then studied and compared using the water-soluble polyvinyl alcohol (PVOH) as a matrix material. It was found that while both of these nanofillers could impart higher stiffness to the polymer, the nanofibers from biomass were more effective in composite reinforcement than the cellulose crystals thanks to their large aspect ratio and their ability to form interconnected network structures through hydrogen bonding. One of the biggest challenges in the development of cellulose nanocomposites is achieving good dispersion. Because of the high density of hydroxyl groups on the surface of cellulose, it remains a difficult task to disperse cellulose nanofibers in many commonly used polymer matrices. The present work addresses this issue by developing a water-based route taking advantage of polymer colloidal suspensions. Combining cellulose nanofibers with one of the most important biopolymers, poly(lactic acid) (PLA), we have prepared nanocomposites with excellent fiber dispersion and improved modulus and strength. The bio-based nanocomposites have a great potential to serve as light-weight structural materials for automotive, medical, and other applications.

The pattern of xylan acetylation suggests xylan may interact with cellulose microfibrils as a twofold helical screw in the secondary plant cell wall of Arabidopsis thaliana.

PubMed

Busse-Wicher, Marta; Gomes, Thiago C F; Tryfona, Theodora; Nikolovski, Nino; Stott, Katherine; Grantham, Nicholas J; Bolam, David N; Skaf, Munir S; Dupree, Paul

2014-08-01

The interaction between xylan and cellulose microfibrils is important for secondary cell wall properties in vascular plants; however, the molecular arrangement of xylan in the cell wall and the nature of the molecular bonding between the polysaccharides are unknown. In dicots, the xylan backbone of β-(1,4)-linked xylosyl residues is decorated by occasional glucuronic acid, and approximately one-half of the xylosyl residues are O-acetylated at C-2 or C-3. We recently proposed that the even, periodic spacing of GlcA residues in the major domain of dicot xylan might allow the xylan backbone to fold as a twofold helical screw to facilitate alignment along, and stable interaction with, cellulose fibrils; however, such an interaction might be adversely impacted by random acetylation of the xylan backbone. Here, we investigated the arrangement of acetyl residues in Arabidopsis xylan using mass spectrometry and NMR. Alternate xylosyl residues along the backbone are acetylated. Using molecular dynamics simulation, we found that a twofold helical screw conformation of xylan is stable in interactions with both hydrophilic and hydrophobic cellulose faces. Tight docking of xylan on the hydrophilic faces is feasible only for xylan decorated on alternate residues and folded as a twofold helical screw. The findings suggest an explanation for the importance of acetylation for xylan-cellulose interactions, and also have implications for our understanding of cell wall molecular architecture and properties, and biological degradation by pathogens and fungi. They will also impact strategies to improve lignocellulose processing for biorefining and bioenergy. © 2014 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.

Microtubules and epithem-cell morphogenesis in hydathodes of Pilea cadierei.

PubMed

Galatis, B

1988-12-01

When cell divisions have ceased, the epithem of the hydathodes of Pilea cadierei Gagnep. et Guill. consists of small polyhedral cells exhibiting a meristematic appearance, and completely lacks intercellular spaces. The cortical microtubules in epithem cells exhibit a unique organization: they are not scattered along the whole wall surface but form groups lying at some distance from each other. In sections, from two to eight groups of microtubules can be observed, each lining a wall region averaging between 0.5 and 1.5 μm in length. These groups represent sections of microtubule bundles girdling a major part or the whole of the cell periphery. They are connected to one another by anastomoses, forming a microtubular reticulum. The assembly of microtubule bundles is followed by the appearance of distinct local thickenings in the adjacent wall areas. The cellulose microfibrils in the thickenings are deposited in parallel to the underlying microtubules. Gradually, the vacuolating epithem cells undergo swelling, except for the areas bounded by the wall thickenings. Since the latter, and actually their constituent bundles of cellulose microfibrils, cannot extend in length the differential cell growth results in schizogenous formation of intercellular spaces between contiguous cell walls at their thickened regions. The spaces then broaden and merge to become an extensive intercellular space system. As a result of the above processes, the epithem cells become constricted and finally deeply lobed. The observations show that (i) the cortical microtubules are intimately involved in the morphogenesis of the epithem cells and (ii) the initiation and development of the epithem intercellular spaces is a phenomenon directly related to cell morphogenesis and therefore to the cortical microtubule cytoskeleton. The sites of initiation of these spaces are highly predictable.

Secondary cell-wall assembly in flax phloem fibres: role of galactans.

PubMed

Gorshkova, Tatyana; Morvan, Claudine

2006-01-01

Non-lignified fibre cells (named gelatinous fibres) are present in tension wood and the stems of fibre crops (such as flax and hemp). These cells develop a very thick S2 layer within the secondary cell wall, which is characterised by (1) cellulose microfibrils largely parallel to the longitudinal axis of the cell, and (2) a high proportion of galactose-containing polymers among the non-cellulosic polysaccharides. In this review, we focus on the role of these polymers in the assembly of gelatinous fibres of flax. At the different stages of fibre development, we analyse in detail data based on sugar composition, linkages of pectic polymers, and immunolocalisation of the beta-(1-->4)-galactans. These data indicate that high molecular-mass gelatinous galactans accumulate in specialised Golgi-derived vesicles during fibre cell-wall thickening. They consist of RG-I-like polymers with side chains of beta-(1-->4)-linked galactose. Most of them are short, but there are also long chains containing up to 28 galactosyl residues. At fibre maturity, two types of cross-linked galactans are identified, a C-L structure that resembles the part of soluble galactan with long side chains and a C-S structure with short chains. Different possibilities for soluble galactan to give rise to C-L and C-S are analysed. In addition, we discuss the prospect for the soluble galactan in preventing the newly formed cellulose chains from completing immediate crystallisation. This leads to a hypothesis that firstly the secretion of soluble galactans plays a role in the axial orientation of cellulose microfibrils, and secondly the remodelling and cross-linking of pectic galactans are linked to the dehydration and the assembly of S2 layer.

Functional reconstitution of cellulose synthase in Escherichia coli.

PubMed

Imai, Tomoya; Sun, Shi-Jing; Horikawa, Yoshiki; Wada, Masahisa; Sugiyama, Junji

2014-11-10

Cellulose is a high molecular weight polysaccharide of β1 → 4-d-glucan widely distributed in nature-from plant cell walls to extracellular polysaccharide in bacteria. Cellulose synthase, together with other auxiliary subunit(s) in the cell membrane, facilitates the fibrillar assembly of cellulose polymer chains into a microfibril. The gene encoding the catalytic subunit of cellulose synthase is cesA and has been identified in many cellulose-producing organisms. Very few studies, however, have shown that recombinant CesA protein synthesizes cellulose polymer, but the mechanism by which CesA protein synthesizes cellulose microfibrils is not known. Here we show that cellulose-synthesizing activity is successfully reconstituted in Escherichia coli by expressing the bacterial cellulose synthase complex of Gluconacetobacter xylinus: CesA and CesB (formerly BcsA and BcsB, respectively). Cellulose synthase activity was, however, only detected when CesA and CesB were coexpressed with diguanyl cyclase (DGC), which synthesizes cyclic-di-GMP (c-di-GMP), which in turn activates cellulose-synthesizing activity in bacteria. Direct observation by electron microscopy revealed extremely thin fibrillar structures outside E. coli cells, which were removed by cellulase treatment. This fiber structure is not likely to be the native crystallographic form of cellulose I, given that it was converted to cellulose II by a chemical treatment milder than ever described. We thus putatively conclude that this fine fiber is an unprecedented structure of cellulose. Despite the inability of the recombinant enzyme to synthesize the native structure of cellulose, the system described in this study, named "CESEC (CEllulose-Synthesizing E. Coli)", represents a useful tool for functional analyses of cellulose synthase and for seeding new nanomaterials.

Cellulose synthase (CesA) genes in the green alga Mesotaenium caldariorum.

PubMed

Roberts, Alison W; Roberts, Eric M; Delmer, Deborah P

2002-12-01

Cellulose, a microfibrillar polysaccharide consisting of bundles of beta-1,4-glucan chains, is a major component of plant and most algal cell walls and is also synthesized by some prokaryotes. Seed plants and bacteria differ in the structures of their membrane terminal complexes that make cellulose and, in turn, control the dimensions of the microfibrils produced. They also differ in the domain structures of their CesA gene products (the catalytic subunit of cellulose synthase), which have been localized to terminal complexes and appear to help maintain terminal complex structure. Terminal complex structures in algae range from rosettes (plant-like) to linear forms (bacterium-like). Thus, algal CesA genes may reveal domains that control terminal complex assembly and microfibril structure. The CesA genes from the alga Mesotaenium caldariorum, a member of the order Zygnematales, which have rosette terminal complexes, are remarkably similar to seed plant CesAs, with deduced amino acid sequence identities of up to 59%. In addition to the putative transmembrane helices and the D-D-D-QXXRW motif shared by all known CesA gene products, M. caldariorum and seed plant CesAs share a region conserved among plants, an N-terminal zinc-binding domain, and a variable or class-specific region. This indicates that the domains that characterize seed plant CesAs arose prior to the evolution of land plants and may play a role in maintaining the structures of rosette terminal complexes. The CesA genes identified in M. caldariorum are the first reported for any eukaryotic alga and will provide a basis for analyzing the CesA genes of algae with different types of terminal complexes.

Cellulose-Pectin Spatial Contacts Are Inherent to Never-Dried Arabidopsis Primary Cell Walls: Evidence from Solid-State Nuclear Magnetic Resonance1[OPEN

PubMed Central

Wang, Tuo; Park, Yong Bum; Hong, Mei

2015-01-01

The structural role of pectins in plant primary cell walls is not yet well understood because of the complex and disordered nature of the cell wall polymers. We recently introduced multidimensional solid-state nuclear magnetic resonance spectroscopy to characterize the spatial proximities of wall polysaccharides. The data showed extensive cross peaks between pectins and cellulose in the primary wall of Arabidopsis (Arabidopsis thaliana), indicating subnanometer contacts between the two polysaccharides. This result was unexpected because stable pectin-cellulose interactions are not predicted by in vitro binding assays and prevailing cell wall models. To investigate whether the spatial contacts that give rise to the cross peaks are artifacts of sample preparation, we now compare never-dried Arabidopsis primary walls with dehydrated and rehydrated samples. One-dimensional 13C spectra, two-dimensional 13C-13C correlation spectra, water-polysaccharide correlation spectra, and dynamics data all indicate that the structure, mobility, and intermolecular contacts of the polysaccharides are indistinguishable between never-dried and rehydrated walls. Moreover, a partially depectinated cell wall in which 40% of homogalacturonan is extracted retains cellulose-pectin cross peaks, indicating that the cellulose-pectin contacts are not due to molecular crowding. The cross peaks are observed both at −20°C and at ambient temperature, thus ruling out freezing as a cause of spatial contacts. These results indicate that rhamnogalacturonan I and a portion of homogalacturonan have significant interactions with cellulose microfibrils in the native primary wall. This pectin-cellulose association may be formed during wall biosynthesis and may involve pectin entrapment in or between cellulose microfibrils, which cannot be mimicked by in vitro binding assays. PMID:26036615

Mosaicing of single plane illumination microscopy images using groupwise registration and fast content-based image fusion

NASA Astrophysics Data System (ADS)

Preibisch, Stephan; Rohlfing, Torsten; Hasak, Michael P.; Tomancak, Pavel

2008-03-01

Single Plane Illumination Microscopy (SPIM; Huisken et al., Nature 305(5686):1007-1009, 2004) is an emerging microscopic technique that enables live imaging of large biological specimens in their entirety. By imaging the living biological sample from multiple angles SPIM has the potential to achieve isotropic resolution throughout even relatively large biological specimens. For every angle, however, only a relatively shallow section of the specimen is imaged with high resolution, whereas deeper regions appear increasingly blurred. In order to produce a single, uniformly high resolution image, we propose here an image mosaicing algorithm that combines state of the art groupwise image registration for alignment with content-based image fusion to prevent degrading of the fused image due to regional blurring of the input images. For the registration stage, we introduce an application-specific groupwise transformation model that incorporates per-image as well as groupwise transformation parameters. We also propose a new fusion algorithm based on Gaussian filters, which is substantially faster than fusion based on local image entropy. We demonstrate the performance of our mosaicing method on data acquired from living embryos of the fruit fly, Drosophila, using four and eight angle acquisitions.

Design of a simple non-destructive detection system using P-wave lasers for determining the soluble solids content of apples.

PubMed

Hua, Shih-Hao; Chen, Chao-Pin; Han, Pin

2017-08-01

The simple and nondestructive detection system studied in this work uses a near-infrared (NIR) detector and parallel-polarized (P-wave) NIR lasers to determine the soluble solids content (SSC) of apples. The P-wave NIR laser in this system is incident into the apple's pulp at the Brewster angle to minimize the interference caused by interfacial reflections. After the apple has been illuminated by four P-wave NIR lasers that correspond to the specified wavelengths of the SSC chemical bonds (880, 940, 980, and 1064 nm), the prediction of correlation (rp2) and the root-mean-square error for prediction (RMSEP) of the SSC are determined via partial least square regression analysis of the reflectance. Our results indicate that the use of P-wave lasers at the Brewster angle (as the angle of incidence) and the above specified wavelengths for the prediction set measurement of the SSC of apples obtained an rp2 of 0.88 and an RMSEP of 0.47°Brix. These rp2 are 6% higher, and the RMSEPs are 9% lower, than those obtained using non-polarized lasers.

Sucrose lyophiles: a semi-quantitative study of residual water content by total X-ray diffraction analysis.

PubMed

Bates, S; Jonaitis, D; Nail, S

2013-10-01

Total X-ray Powder Diffraction Analysis (TXRPD) using transmission geometry was able to observe significant variance in measured powder patterns for sucrose lyophilizates with differing residual water contents. Integrated diffraction intensity corresponding to the observed variances was found to be linearly correlated to residual water content as measured by an independent technique. The observed variance was concentrated in two distinct regions of the lyophilizate powder pattern, corresponding to the characteristic sucrose matrix double halo and the high angle diffuse region normally associated with free-water. Full pattern fitting of the lyophilizate powder patterns suggested that the high angle variance was better described by the characteristic diffraction profile of a concentrated sucrose/water system rather than by the free-water diffraction profile. This suggests that the residual water in the sucrose lyophilizates is intimately mixed at the molecular level with sucrose molecules forming a liquid/solid solution. The bound nature of the residual water and its impact on the sucrose matrix gives an enhanced diffraction response between 3.0 and 3.5 beyond that expected for free-water. The enhanced diffraction response allows semi-quantitative analysis of residual water contents within the studied sucrose lyophilizates to levels below 1% by weight. Copyright © 2013 Elsevier B.V. All rights reserved.

Effect of MnO content on the interfacial property of mold flux and steel

NASA Astrophysics Data System (ADS)

Wang, Wanlin; Li, Jingwen; Zhou, Lejun; Yang, Jian

2016-07-01

The interfacial property between liquid mold flux and steel has significant impact on the quality of casting slab, and this property is mainly determined by the chemical composition of mold flux and the reaction between the flux and steel. The effect of MnO content on the contact angle and interfacial tension between liquid mold flux and ultra-low carbon steel was investigated by sessile drop method in this article, and the results suggested that both the contact angle and interfacial tension decreased with the increase of MnO content in the mold flux. The increase of Si and Mn and the reduction of Al and Ti in the interaction layer were caused by the chemical reactions occurred in the vicinity of interface between mold flux and steel substrate. Besides, the thickness of the interaction layer increased from 4 μm to 7 μm, then to 9 μm, 11 μm and 15 μm when the MnO content was added from 1 wt% to 3 wt%, then to 5 wt%, 7 wt%, and 9 wt% due to the fact that MnO can simplify the polymerized structure of the melt and improve the penetrability of molten mold flux to make the interfacial reaction easier.

Probing the evolution of the EAS muon content in the atmosphere with KASCADE-Grande

NASA Astrophysics Data System (ADS)

Apel, W. D.; Arteaga-Velázquez, J. C.; Bekk, K.; Bertaina, M.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Fuhrmann, D.; Gherghel-Lascu, A.; Gils, H. J.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Huege, T.; Kampert, K.-H.; Kang, D.; Klages, H. O.; Link, K.; Łuczak, P.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mitrica, B.; Morello, C.; Oehlschläger, J.; Ostapchenko, S.; Pierog, T.; Rebel, H.; Roth, M.; Schieler, H.; Schoo, S.; Schröder, F. G.; Sima, O.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Weindl, A.; Wochele, J.; Zabierowski, J.

2017-10-01

The evolution of the muon content of very high energy air showers (EAS) in the atmosphere is investigated with data of the KASCADE-Grande observatory. For this purpose, the muon attenuation length in the atmosphere is obtained to Λμ = 1256 ± 85-232+229 (syst) g/cm2 from the experimental data for shower energies between 1016.3 and 1017.0 eV. Comparison of this quantity with predictions of the high-energy hadronic interaction models QGSJET-II-02, SIBYLL 2.1, QGSJET-II-04 and EPOS-LHC reveals that the attenuation of the muon content of measured EAS in the atmosphere is lower than predicted. Deviations are, however, less significant with the post-LHC models. The presence of such deviations seems to be related to a difference between the simulated and the measured zenith angle evolutions of the lateral muon density distributions of EAS, which also causes a discrepancy between the measured absorption lengths of the density of shower muons and the predicted ones at large distances from the EAS core. The studied deficiencies show that all four considered hadronic interaction models fail to describe consistently the zenith angle evolution of the muon content of EAS in the aforesaid energy regime.

Role of xyloglucan in cotton (Gossypium hirsutum L.) fiber elongation of the short fiber mutant Ligon lintless-2 (Li2).

PubMed

Naoumkina, Marina; Hinchliffe, Doug J; Fang, David D; Florane, Christopher B; Thyssen, Gregory N

2017-08-30

Xyloglucan is a matrix polysaccharide found in the cell walls of all land plants. In growing cells, xyloglucan is thought to connect cellulose microfibrils and regulate their separation during wall extension. Ligon lintless-2 (Li 2 ) is a monogenic dominant cotton fiber mutation that causes extreme reduction in lint fiber length with no pleiotropic effects on vegetative growth. Li 2 represents an excellent model system to study fiber elongation. To understand the role of xyloglucan in cotton fiber elongation we used the short fiber mutant Li 2 and its near isogenic wild type for analysis of xyloglucan content and expression of xyloglucan-related genes in developing fibers. Accumulation of xyloglucan was significantly higher in Li 2 developing fibers than in wild type. Genes encoding enzymes for nine family members of xyloglucan biosynthesis were identified in the draft Gossypium hirsutum genome. RNAseq analysis revealed that most differentially expressed xyloglucan-related genes were down-regulated in Li 2 fiber cells. RT-qPCR analysis revealed that the peak of expression for the majority of xyloglucan-related genes in wild type developing fibers was 5-16days post anthesis (DPA) compared to 1-3 DPA in Li 2 fibers. Thus, our results suggest that early activation of xyloglucan-related genes and down regulation of xyloglucan degradation genes during the elongation phase lead to elevated accumulation of xyloglucan that restricts elongation of fiber cells in Li 2 . Copyright © 2017. Published by Elsevier B.V.

High-Alpha Handling Qualities Flight Research on the NASA F/A-18 High Alpha Research Vehicle

NASA Technical Reports Server (NTRS)

Wichman, Keith D.; Pahle, Joseph W.; Bahm, Catherine; Davidson, John B.; Bacon, Barton J.; Murphy, Patrick C.; Ostroff, Aaron J.; Hoffler, Keith D.

1996-01-01

A flight research study of high-angle-of-attack handling qualities has been conducted at the NASA Dryden Flight Research Center using the F/A-18 High Alpha Research Vehicle (HARV). The objectives were to create a high-angle-of-attack handling qualities flight database, develop appropriate research evaluation maneuvers, and evaluate high-angle-of-attack handling qualities guidelines and criteria. Using linear and nonlinear simulations and flight research data, the predictions from each criterion were compared with the pilot ratings and comments. Proposed high-angle-of-attack nonlinear design guidelines and proposed handling qualities criteria and guidelines developed using piloted simulation were considered. Recently formulated time-domain Neal-Smith guidelines were also considered for application to high-angle-of-attack maneuvering. Conventional envelope criteria were evaluated for possible extension to the high-angle-of-attack regime. Additionally, the maneuvers were studied as potential evaluation techniques, including a limited validation of the proposed standard evaluation maneuver set. This paper gives an overview of these research objectives through examples and summarizes result highlights. The maneuver development is described briefly, the criteria evaluation is emphasized with example results given, and a brief discussion of the database form and content is presented.

Self-Assembly Behavior of Pullulan Abietate

NASA Astrophysics Data System (ADS)

Gradwell, Sheila; Esker, Alan; Glasser, Wolgang; Heinze, Thomas

2003-03-01

Wood is one of nature's most fascinating biological composites due to its toughness and resistance to fracture properties. These properties stem from the self-assembly of cellulose microfibrils in an amorphous matrix of hemicellulose and lignin. In recent years, science has looked to nature for guidance in preparing synthetic materials with desirable physical properties. In order to study the self-assembly process in wood, a model system composed of a polysaccharide, pullulan abietate, and a biomimetic cellulose substrate prepared by the Langmuir-Blodgett technique has been developed. Interfacial tension and surface plasmon resonance measurements used to study the self-assembly process will be discussed for different pullulan derivatives.

Assembly of synthetic cellulose I.

PubMed

Lee, J H; Brown, R M; Kuga, S; Shoda, S; Kobayashi, S

1994-08-02

Cellulose microfibrils with an electron diffraction pattern characteristic of crystalline native cellulose I have been assembled abiotically by means of a cellulase-catalyzed polymerization of beta-cellobiosyl fluoride substrate monomer in acetonitrile/acetate buffer. Substantial purification of the Trichoderma viride cellulase enzyme was found to be essential for the formation of the synthetic cellulose I allomorph. Assembly of synthetic cellulose I appears to be a result of a micellar aggregation of the partially purified enzyme and the substrate in an organic/aqueous solvent system favoring the alignment of glucan chains with the same polarity and extended chain conformation, resulting in crystallization to form the metastable cellulose I allomorph.

Estimation of crystallinity in a model thermoplastic composite

NASA Technical Reports Server (NTRS)

Wakelyn, N. T.

1986-01-01

Crystallinities as low as 16 percent have been estimated by determination of the interplanar spacing on PET/carbonaceous filament composites with resin content of aobut 25 percent w/w using wide-angle X-ray scattering (WAXS) in the angular range 2 theta = 16-18 deg. The diffraction pattern of the carbonaceous reinforcements masks the major reflections of the resin, and the resin content and the crystallinity are kept low to make the simulation reasonable.

Bone and Soft Tissue Nasal Angles Discrepancies and Overlying Skin Thickness: A Computed Tomography Study.

PubMed

Alharethy, Sami; Alohali, Sama; Alquniabut, Ibrahim; Jang, Yong Ju

2018-04-11

The aim of this study was to derive the normal values for bone and soft tissue nasal angles as well as the overlying skin thickness and to attempt to determine the correlation between differences in bone and soft tissue angles and overlying skin thickness in Middle Eastern patients. Three-dimensional cephalometric analysis was performed for 100 patients who underwent computed tomography of the paranasal sinuses. The nasofrontal angle, pyramidal angle-nasal root, pyramidal angle-tip of the nasal bone, and overlying skin thickness were measured, and the results were analyzed according to sex, age, and body mass index (BMI). All soft tissue angles were significantly larger than the bone angles, with the mean difference being 11.62°, 30.80°, and 27.05° for the nasofrontal angle (P = 0.000), pyramidal angle-nasal root (P = 0.000), and pyramidal angle-tip of the nasal bone (P = 0.000), respectively. The mean overlying skin thickness was 3.89 ± 1.48 mm at the nasion, 1.16 ± 0.6 mm at the rhinion, and 2.93 ± .97 mm at the nasal tip. Differences in the nasofrontal angle were strongly correlated with the skin thickness at the nasion (P = 0.001). A simple clinical exam of the soft tissue nasal angles does not reflect the underlying bone angles that will be encountered during rhinoplasty. BMI does not influence nasal shape, and rhinoplasty surgery should take into account the ethnic group, age, and sex of the patient. Surgeons should leave a minor skeletal hump at the end of the nasal bone for Middle Eastern patients. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Wettability of MnxSiyOz by Liquid Zn-Al Alloys

NASA Astrophysics Data System (ADS)

Kim, Yunkyum; Shin, Minsoo; Tang, Chengying; Lee, Joonho

2010-08-01

The wettability of MnxSiyOz by liquid Zn-Al alloys was investigated to obtain basic information on the coating properties of high-strength steels with surface oxides in the hot-dip galvanizing process. In this study, the contact angles of liquid Zn-Al alloys (Al concentrations were 0.12 and 0.23 wt pct) on four different MnxSiyOz oxides, namely MnO, MnSiO3, Mn2SiO4, and SiO2, were measured with the dispensed drop method. The contact angle did not change across time. With an increasing Al concentration, the contact angle was slightly decreased for MnO and Mn2SiO4, but there was no change for MnSiO3 and SiO2. With an increasing SiO2 content, the contact angle gradually increased by 54 wt pct to form MnSiO3, and for pure SiO2 substrate, the contact angle decreased again. Consequently, the MnSiO3 substrate showed the worst wettability among the four tested oxide substrates.

Fabrication of a silica aerogel and examination of its hydrophobic properties via contact angle and 3M water repellency tests

NASA Astrophysics Data System (ADS)

Mazrouei-Sebdani, Z.; Javazmi, L.; Khoddami, A.; Shams-Ghahfarokhi, F.; Low, T.

2017-05-01

Aerogels are dry gels with a very high specific pore volume. Aerogels with increased hydrophobicity have significant potential to expand their use as lightweight materials. Considering its special nanostructure and exceptional properties, this paper focuses on the synthesis and hydrophobic evaluation of a silica aerogel. The structural properties were investigated by measuring density, SEM micrographs, and BET analyses. Also, the hydrophobic evaluation was carried out by measuring 3M water repellency and water/alcohol contact angle. The BET analysis showed successful synthesis of the nanoporous silica aerogel with a pore size of 24 nm and porosity of 89%. The synthesized aerogel showed 3M water repellency of 3 and water contact angle of 129.6°. Also, it is worth-mentioning that as the alcohol content of the drops in 3M water repellency test is increased, the drop contact angle is decreased due to its lower surface tension. Thus, the contact angle reaches the zero at 3M water repellency test number of 4 (water/alcohol 60/40).

SSMILES.

ERIC Educational Resources Information Center

Berlin, Donna

1990-01-01

Provides an activity for determining the relationship between the displacement of light rays passing through a plate of transparent material and the angle of refraction for the material. Describes related concepts and skills, prerequisites, objectives, rationale, content background, lesson outline, worksheet, evaluation, teacher notes, and…

Characterizing a New Surface-Based Shortwave Cloud Retrieval Technique, Based on Transmitted Radiance for Soil and Vegetated Surface Types

NASA Technical Reports Server (NTRS)

Coddington, Odele; Pilewskie, Peter; Schmidt, K. Sebastian; McBride, Patrick J.; Vukicevic, Tomislava

2013-01-01

This paper presents an approach using the GEneralized Nonlinear Retrieval Analysis (GENRA) tool and general inverse theory diagnostics including the maximum likelihood solution and the Shannon information content to investigate the performance of a new spectral technique for the retrieval of cloud optical properties from surface based transmittance measurements. The cumulative retrieval information over broad ranges in cloud optical thickness (tau), droplet effective radius (r(sub e)), and overhead sun angles is quantified under two conditions known to impact transmitted radiation; the variability in land surface albedo and atmospheric water vapor content. Our conclusions are: (1) the retrieved cloud properties are more sensitive to the natural variability in land surface albedo than to water vapor content; (2) the new spectral technique is more accurate (but still imprecise) than a standard approach, in particular for tau between 5 and 60 and r(sub e) less than approximately 20 nm; and (3) the retrieved cloud properties are dependent on sun angle for clouds of tau from 5 to 10 and r(sub e) less than 10 nm, with maximum sensitivity obtained for an overhead sun.

Influence of propylene glycol on aqueous silica dispersions and particle-stabilized emulsions.

PubMed

Binks, Bernard P; Fletcher, Paul D I; Thompson, Michael A; Elliott, Russell P

2013-05-14

We have studied the influence of adding propylene glycol to both aqueous dispersions of fumed silica nanoparticles and emulsions of paraffin liquid and water stabilized by the same particles. In the absence of oil, aerating mixtures of aqueous propylene glycol and particles yields either stable dispersions, aqueous foams, climbing particle films, or liquid marbles depending on the glycol content and particle hydrophobicity. The presence of glycol in water promotes particles to behave as if they are more hydrophilic. Calculations of their contact angle at the air-aqueous propylene glycol surface are in agreement with these findings. In the presence of oil, particle-stabilized emulsions invert from water-in-oil to oil-in-water upon increasing either the inherent hydrophilicity of the particles or the glycol content in the aqueous phase. Stable multiple emulsions occur around phase inversion in systems of low glycol content, and completely stable, waterless oil-in-propylene glycol emulsions can also be prepared. Accounting for the surface energies at the respective interfaces allows estimation of the contact angle at the oil-polar phase interface; reasonable agreement between measured and calculated phase inversion conditions is found assuming no glycol adsorption on particle surfaces.

Properties of ternary Sn-Ag-Bi solder alloys. Part 2: Wettability and mechanical properties analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vianco, P.T.; Rejent, J.A.

1999-10-01

Bismuth additions of 1% to 10% were made to the 96.5Sn-3.5Ag (wt.%) alloy in a study to develop a Sn-Ag-Bi ternary composition. Thermal properties and microstructural analyses of selected alloy compositions were reported in Part 1. Wettability and mechanical properties are described in this paper. Contact angle measurements demonstrated that Bi additions improved wetting/spreading performance on Cu; a minimum contact angle of 31 {+-} 4{degree} was observed with 4.83 wt.% Bi addition. Increasing the Bi content of the ternary alloy raised the Cu/solder/Cu solder joint shear strength to 81 MPa as determined by the ring-and-plug tests. TEM analysis of themore » 91.84Sn-3.33Ag-4.83Bi composition presented in Part 1 indicated that the strength improvement was attributed to solid-solution and precipitation strengthening effects by the Bi addition residing in the Sn-rich phase. Microhardness measurements of the Sn-Ag-Bi alloy, as a function of Bi content, reached maximum values of 30 (Knoop, 50 g) and 110 (Knoop, 5g) for Bi contents greater than approximately 4--5 wt.%.« less

Active probing of cloud multiple scattering, optical depth, vertical thickness, and liquid water content using wide-angle imaging lidar

NASA Astrophysics Data System (ADS)

Love, Steven P.; Davis, Anthony B.; Rohde, Charles A.; Tellier, Larry; Ho, Cheng

2002-09-01

At most optical wavelengths, laser light in a cloud lidar experiment is not absorbed but merely scattered out of the beam, eventually escaping the cloud via multiple scattering. There is much information available in this light scattered far from the input beam, information ignored by traditional 'on-beam' lidar. Monitoring these off-beam returns in a fully space- and time-resolved manner is the essence of our unique instrument, Wide Angle Imaging Lidar (WAIL). In effect, WAIL produces wide-field (60-degree full-angle) 'movies' of the scattering process and records the cloud's radiative Green functions. A direct data product of WAIL is the distribution of photon path lengths resulting from multiple scattering in the cloud. Following insights from diffusion theory, we can use the measured Green functions to infer the physical thickness and optical depth of the cloud layer, and, from there, estimate the volume-averaged liquid water content. WAIL is notable in that it is applicable to optically thick clouds, a regime in which traditional lidar is reduced to ceilometry. Here we present recent WAIL data on various clouds and discuss the extension of WAIL to full diurnal monitoring by means of an ultra-narrow magneto-optic atomic line filter for daytime measurements.

Factors influencing the drain and rinse operation of Banana screens

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Brien, M.; Firth, B.

An Australian Coal Association Research Project (ACARP) study to identify the variables and effects on Banana screens is described in this article. The impacts of the following system variables were investigated: panel angle, volumetric feed flow rate, solids content of feed screen motion, vibration frequency, magnetite content and impact of screen aperture. The article was adapted from a presentation at Coal Prep 2005, Lexington, KY, USA in May 2005. 4 refs., 8 figs., 1 tab.

Evaluating the capabilities of vegetation spectral indices on chlorophyll content estimation at Sentinel-2 spectral resolutions

NASA Astrophysics Data System (ADS)

Sun, Qi; Jiao, Quanjun; Dai, Huayang

2018-03-01

Chlorophyll is an important pigment in green plants for photosynthesis and obtaining the energy for growth and development. The rapid, nondestructive and accurate estimation of chlorophyll content is significant for understanding the crops growth, monitoring the disease and insect, and assessing the yield of crops. Sentinel-2 equipped with the Multi-Spectral Instrument (MSI), which will provide images with high spatial, spectral and temporal resolution. It covers the VNIR/SWIR spectral region in 13 bands and incorporates two new spectral bands in the red-edge region and a spatial resolution of 20nm, which can be used to derive vegetation indices using red-edge bands. In this paper, we will focus on assessing the potential of vegetation spectral indices for retrieving chlorophyll content from Sentinel-2 at different angles. Subsequently, we used in-situ spectral data and Sentinel-2 data to test the relationship between VIs and chlorophyll content. The REP, MTCI, CIred-edge, CIgreen, Macc01, TCARI/OSAVI [705,750], NDRE1 and NDRE2 were calculated. NDRE2 index displays a strongly similar result for hyperspectral and simulated Sentinel-2 spectral bands (R2 =0.53, R2 =0.51, for hyperspectral and Sentinel-2, respectively). At different observation angles, NDRE2 has the smallest difference in performance (R2 = 0.51, R2 =0.64, at 0° and 15° , respectively).

Surface forces between hydrophilic silica surfaces in a moisture-sensitive oleophilic diacrylate monomer liquid

NASA Astrophysics Data System (ADS)

Ito, Shunya; Kasuya, Motohiro; Kurihara, Kazue; Nakagawa, Masaru

2018-02-01

We measured the surface forces generated between fused silica surfaces in a low-viscosity oleophilic diacrylate monomer for reliably repeated ultraviolet (UV) nanoimprinting, and studied the influence of water in monomer liquids on the forces. Fused silica surfaces, with a static contact angle of 52.6 ± 1.7° for water, owing to the low degree of hydroxylation, hardly showed reproducible surface forces with repeated scan cycles, comprising approach and separation, even in an identical liquid monomer medium with both of low and high water content. The monomer liquid with a high water content of approximately 420 ppm showed a greater tendency to increase the surface forces at longer surface-surface distances compared with the monomer liquid with a low water content of approximately 60 ppm. On the other hand, silica surfaces with a water contact angle of < 5° after exposure to vacuum UV (VUV) light under a reduced air pressure showed reproducible profiles of surfaces forces using the monomer with a low water concentration of approximately 60 ppm for repeated surface forces scan cycles even in separately prepared silica surfaces, whilst they showed less reproducible profiles in the liquids with high water content of 430 ppm. These results suggested that water possibly adsorbed on the hydrophilic and hydrophobic silica surfaces in the monomer liquid of the high water concentration influenced the repeatability of the surface forces profiles.

Trihydroxybenzoic acid glucoside as a global skin color modulator and photo-protectant

PubMed Central

Chajra, Hanane; Redziniak, Gérard; Auriol, Daniel; Schweikert, Kuno; Lefevre, Fabrice

2015-01-01

Background 3,4,5-Trihydroxybenzoic acid glucoside (THBG), a molecule produced by an original biocatalysis-based technology, was assessed in this study with respect to its skin photoprotective capacity and its skin color control property on Asian-type skin at a clinical level and on skin explant culture models. Methods The double-blinded clinical study was done in comparison to a vehicle by the determination of objective color parameters thanks to recognized quantitative and qualitative analysis tools, including Chroma-Meter, VISIA-CR™, and SIAscope™. Determination of L* (brightness), a* and b* (green–red and blue–yellow chromaticity coordinates), individual typology angle, and C* (chroma) and h* (hue angle) parameters using a Chroma-Meter demonstrated that THBG is able to modify skin color while quantification of ultraviolet (UV) spots by VISIA-CR™ confirmed its photoprotective effect. The mechanism of action of THBG molecule was determined using explant skin culture model coupled to histological analysis (epidermis melanin content staining). Results We have demonstrated that THBG was able to modulate significantly several critical parameters involved in skin color control such as L* (brightness), a* (redness), individual typology angle (pigmentation), and hue angle (yellowness in this study), whereas no modification occurs on b* and C* parameters. We have demonstrated using histological staining that THBG decrease epidermis melanin content under unirradiated and irradiated condition. We also confirmed that THBG molecule is not a sunscreen agent. Conclusion This study demonstrated that THBG controls skin tone via the inhibition of melanin synthesis as well as the modulation of skin brightness, yellowness, and redness. PMID:26648748

Contribution of pigment content, myoglobin forms and internal reflectance to the colour of pork loin and ham from pure breed pigs.

PubMed

Lindahl, G; Lundström, K; Tornberg, E

2001-10-01

The colour of loin, M. longissimus dorsi (LD), and ham, M. biceps femoris (BF), from pure breed Hampshire, Swedish Landrace and Swedish Yorkshire pigs was studied. The contribution of the pigment content, the myoglobin forms deoxymyoglobin (Mb), oxymyoglobin (MbO) and metmyoglobin (MetMb) and the internal reflectance to the colour of pork of normal meat quality was evaluated using partial least squares regression (PLS). The colour of LD and BF from the Hampshire breed was more red and yellow and more saturated than the colour of the same muscles from the Swedish Landrace and the Swedish Yorkshire breeds. Furthermore, BF from Hampshire was darker than BF from the other two breeds. These differences in colour were related to the lower pH in Hampshire, resulting in more blooming and in higher internal reflectance, and to the higher pigment content. The colour of BF was darker and more red than the colour of LD within each breed. No colour difference was found between gilts and castrates within each breed. Most of the variation (86-90%) in lightness (L* value), redness (a* value) and yellowness (b* value), chroma (saturation) and hue angle of pork of normal meat quality was explained by the pigment content, myoglobin forms and internal reflectance. The L* value, a* value, chroma and hue angle were influenced by both the pigment content and by the myoglobin forms to almost the same extent, while the internal reflectance was of no significance to these colour parameters. The b* value was influenced most by the myoglobin forms, less by the internal reflectance and almost not at all by the pigment content.

Adaptive Selective Harmonic Minimization Based on ANNs for Cascade Multilevel Inverters With Varying DC Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filho, Faete; Maia, Helder Z; Mateus, Tiago Henrique D

2013-01-01

A new approach for modulation of an 11-level cascade multilevel inverter using selective harmonic elimination is presented in this paper. The dc sources feeding the multilevel inverter are considered to be varying in time, and the switching angles are adapted to the dc source variation. This method uses genetic algorithms to obtain switching angles offline for different dc source values. Then, artificial neural networks are used to determine the switching angles that correspond to the real-time values of the dc sources for each phase. This implies that each one of the dc sources of this topology can have different valuesmore » at any time, but the output fundamental voltage will stay constant and the harmonic content will still meet the specifications. The modulating switching angles are updated at each cycle of the output fundamental voltage. This paper gives details on the method in addition to simulation and experimental results.« less

Exploring high-achieving sixth grade students' erroneous answers and misconceptions on the angle concept

NASA Astrophysics Data System (ADS)

Bütüner, Suphi Önder; Filiz, Mehmet

2017-05-01

The aim of this research was to investigate high achievers' erroneous answers and misconceptions on the angle concept. The participants consisted of 233 grade 6 students drawn from eight classes in two well-established elementary schools of Trabzon, Turkey. All the participants were considered to be current achievers in mathematics, graded 4 or 5 out of 5, and selected via a purposive sampling method. Data were collected through six questions reflecting the learning competencies set out in the grade 6 curriculum in Turkey and the findings of previous studies that aimed to identify students' misconceptions of the angle concept. This questionnaire was then applied over a 40-minute period in each class. The findings were analysed by two researchers whose inter-rater agreement was computed as 0.97, or almost perfect. Thereafter, coding discrepancies were resolved, and consensus was established. We found that although the participants in this study were high achievers, they still held several misconceptions on the angle concept such as recognizing a straight angle or a right angle in different orientations. We also show how some of these misconceptions could have arisen due to the definitions or representations used in the textbook, and offer suggestions concerning their content in the future.

[Estimation of forest canopy chlorophyll content based on PROSPECT and SAIL models].

PubMed

Yang, Xi-guang; Fan, Wen-yi; Yu, Ying

2010-11-01

The forest canopy chlorophyll content directly reflects the health and stress of forest. The accurate estimation of the forest canopy chlorophyll content is a significant foundation for researching forest ecosystem cycle models. In the present paper, the inversion of the forest canopy chlorophyll content was based on PROSPECT and SAIL models from the physical mechanism angle. First, leaf spectrum and canopy spectrum were simulated by PROSPECT and SAIL models respectively. And leaf chlorophyll content look-up-table was established for leaf chlorophyll content retrieval. Then leaf chlorophyll content was converted into canopy chlorophyll content by Leaf Area Index (LAD). Finally, canopy chlorophyll content was estimated from Hyperion image. The results indicated that the main effect bands of chlorophyll content were 400-900 nm, the simulation of leaf and canopy spectrum by PROSPECT and SAIL models fit better with the measured spectrum with 7.06% and 16.49% relative error respectively, the RMSE of LAI inversion was 0. 542 6 and the forest canopy chlorophyll content was estimated better by PROSPECT and SAIL models with precision = 77.02%.

Duck gait: Relationship to hip angle, bone ash, bone density, and morphology.

PubMed

Robison, Cara I; Rice, Meredith; Makagon, Maja M; Karcher, Darrin M

2015-05-01

The rapid growth meat birds, including ducks, undergo requires skeletal integrity; however, fast growth may not be conducive to adequate bone structure. A relationship likely exists between skeletal changes and duck mobility. Reduced mobility in meat ducks may have impacts on welfare and production. This study examined the relationships among gait score, bone parameters, and hip angle. Commercial Pekin ducks, ages 14 d (n = 100), 21 d (n = 100), and 32 d (n = 100) were weighed and gait scored with a 3-point gait score system by an observer as they walked over a Tekscan gait analysis system. Gait was scored as GS0, GS1, or GS2 with a score of GS0 defined as good walking ability and a score of GS2 as poorest walking ability. Ducks were humanely euthanized, full body scanned using quantitative computed tomography (QCT), and the right femur and tibia were extracted. Leg bones were cleaned, measured, fat extracted, and ashed. QCT scans were rendered to create computerized 3D models where pelvic hip angles and bone density were measured. Statistical analysis was conducted using PROC MIXED with age and gait score in the model. Body weight increased with age, but within an age, body weight decreased as walking ability became worse (P < 0.01). As expected, linear increases in tibia and femur bone width and length were observed as the ducks aged (P < 0.01). Right and left hip angle increased with duck age (P < 0.01). Additionally, ducks with a GS2 had wider hip angles opposed to ducks with a GS0 (P < 0.01). Bone density increased linearly with both age and gait score (P < 0.05). Femur ash content was lowest in 32-day-old ducks and ducks with GS1 and GS2 (P < 0.0001). Tibia ash content increased with age, but decreased as gait score increased (P < 0.001). The observation that right hip angle changed with gait scores merits further investigation into the relationship between duck mobility and skeletal changes during growth. © 2015 Poultry Science Association Inc.

The impact of fibre orientation on T1-relaxation and apparent tissue water content in white matter.

PubMed

Schyboll, Felix; Jaekel, Uwe; Weber, Bernd; Neeb, Heiko

2018-02-20

Recent MRI studies have shown that the orientation of nerve fibres relative to the main magnetic field affects the R 2 *(= 1/T 2 *) relaxation rate in white matter (WM) structures. The underlying physical causes have been discussed in several studies but are still not completely understood. However, understanding these effects in detail is of great importance since this might serve as a basis for the development of new diagnostic tools and/or improve quantitative susceptibility mapping techniques. Therefore, in addition to the known angular dependence of R 2 *, the current study investigates the relationship between fibre orientation and the longitudinal relaxation rate, R 1 (= 1/T 1 ), as well as the apparent water content. For a group of 16 healthy subjects, a series of gradient echo, echo-planar and diffusion weighted images were acquired at 3T from which the decay rates, the apparent water content and the diffusion direction were reconstructed. The diffusion weighted data were used to determine the angle between the principle fibre direction and the main magnetic field to examine the angular dependence of R 1 and apparent water content. The obtained results demonstrate that both parameters depend on the fibre orientation and exhibit a positive correlation with the angle between fibre direction and main magnetic field. These observations could be helpful to improve and/or constrain existing biophysical models of brain microstructure by imposing additional constraints resulting from the observed angular dependence R 1 and apparent water content in white matter.

Response of some Thematic Mapper band ratios to variation in soil water content

NASA Technical Reports Server (NTRS)

Musick, H. Brad; Pelletier, Ramona E.

1986-01-01

Bidirectional reflectance to nadir in the reflective TM bands and the 1.15-1.3-micron band was measured in the laboratory as moisture content was varied in ten soils. Stronger absorption by water in TM5 and TM7 was expected to cause ratios of other bands to TM5 and TM7 to increase with water content, but in most cases these ratios were constant or decreased at low to intermediate water content and increased only at high moisture levels. Because these ratios were found to decrease as illumination elevation angle decreased, it was suggested that increased roughness resulting from the methods of moistening and mixing the soil may have tended to counteract the expected ratio increases.

Improved estimation of leaf area index and leaf chlorophyll content of a potato crop using multi-angle spectral data - potential of unmanned aerial vehicle imagery

NASA Astrophysics Data System (ADS)

Roosjen, Peter P. J.; Brede, Benjamin; Suomalainen, Juha M.; Bartholomeus, Harm M.; Kooistra, Lammert; Clevers, Jan G. P. W.

2018-04-01

In addition to single-angle reflectance data, multi-angular observations can be used as an additional information source for the retrieval of properties of an observed target surface. In this paper, we studied the potential of multi-angular reflectance data for the improvement of leaf area index (LAI) and leaf chlorophyll content (LCC) estimation by numerical inversion of the PROSAIL model. The potential for improvement of LAI and LCC was evaluated for both measured data and simulated data. The measured data was collected on 19 July 2016 by a frame-camera mounted on an unmanned aerial vehicle (UAV) over a potato field, where eight experimental plots of 30 × 30 m were designed with different fertilization levels. Dozens of viewing angles, covering the hemisphere up to around 30° from nadir, were obtained by a large forward and sideways overlap of collected images. Simultaneously to the UAV flight, in situ measurements of LAI and LCC were performed. Inversion of the PROSAIL model was done based on nadir data and based on multi-angular data collected by the UAV. Inversion based on the multi-angular data performed slightly better than inversion based on nadir data, indicated by the decrease in RMSE from 0.70 to 0.65 m2/m2 for the estimation of LAI, and from 17.35 to 17.29 μg/cm2 for the estimation of LCC, when nadir data were used and when multi-angular data were used, respectively. In addition to inversions based on measured data, we simulated several datasets at different multi-angular configurations and compared the accuracy of the inversions of these datasets with the inversion based on data simulated at nadir position. In general, the results based on simulated (synthetic) data indicated that when more viewing angles, more well distributed viewing angles, and viewing angles up to larger zenith angles were available for inversion, the most accurate estimations were obtained. Interestingly, when using spectra simulated at multi-angular sampling configurations as were captured by the UAV platform (view zenith angles up to 30°), already a huge improvement could be obtained when compared to solely using spectra simulated at nadir position. The results of this study show that the estimation of LAI and LCC by numerical inversion of the PROSAIL model can be improved when multi-angular observations are introduced. However, for the potato crop, PROSAIL inversion for measured data only showed moderate accuracy and slight improvements.

Nano-sculptured Janus-like TiAg thin films obliquely deposited by GLAD co-sputtering for temperature sensing.

PubMed

Pedrosa, Paulo; Ferreira, Armando; Martin, Nicolas; Arab Pour Yazdi, Mohammad; Billard, Alain; Lanceros-Mendez, Senentxu; Vaz, Filipe

2018-06-11

Inclined, zigzag and spiral TiAg films were prepared by GLancing Angle Deposition (GLAD), using two distinct Ti and Ag targets with a particle incident angle of 80º and Ag contents ranging from 20 to 75 at. %. The effect of increasing Ag incorporation and columnar architecture change on the morphological, structural and electrical properties of the films was investigated. It is shown that inclined columnar features (β = 47º) with high porosity were obtained for 20 at. % Ag, with the column angle sharply decreasing (β = 21º) for 50 at. % Ag, and steeply increasing afterwards until 37º for the film with 75 at. % Ag. The sputtered films exhibit a rather well-crystallized structure for Ag contents ≥ 50 at. %, with a TiAg (111) preferential growth. No significant oxidation was detected in all films, except for the one with 20 at. % Ag, after two 298-473-298 K temperature cycles in air. The calculated temperature coefficient of resistivity (TCR) values vary between 1.4 and 5.5×10-4 K-1. Nano-sculptured spiral films exhibit consistently higher resistivity (ρ = 1.5×10-6 Ω m) and TCR values (2.9×10-4 K-1) than the inclined one with the same Ag content (ρ = 1.2×10-6 Ω m and TCR = 2.0×10-4 K-1). No significant changes are observed in the zigzag films concerning these properties. The effective anisotropy Aeff at 473 K changes from 1.3 to 1.7 for the inclined films. Spiral films exhibit an almost completely isotropic behavior with Aeff = 1.1. Ag-rich TiAg core + shell Janus-like columns were obtained with increasing Ag concentrations. © 2018 IOP Publishing Ltd.

Nondestructive testing of CFRP plates by Lamb waves

NASA Astrophysics Data System (ADS)

Tsushima, Satoshi; Fukiage, Norio; Ono, Masao

1993-03-01

Nondestructive testing based on low frequency Lamb waves was used to analyze the thickness of plates, the delamination, the fiber contents, and the wave velocities in composite laminates. The thickness of plates was predicted and the delamination was detected using the relationship between the phase velocities of Lamb waves and the product of frequency and plate thickness. The fiber content was predicted from the stationary waves, and the wave velocity propagating at an angle to the fiber direction was calculated using the Young's modulus.

Structure of polyacrylic acid and polymethacrylic acid solutions : a small angle neutron scattering study

NASA Astrophysics Data System (ADS)

Moussaid, A.; Schosseler, F.; Munch, J. P.; Candau, S. J.

1993-04-01

The intensity scattered from polyacrylic acid and polymethacrylic acid solutions has been measured by small angle neutron scattering experiemnts. The influence of polymer concentration, ionization degree, temperature and salt content has been investigated. Results are in qualitative agreement with a model which predicts the existence of microphases in the unstable region of the phase diagram. Quantitative comparison with the theory is performed by fitting the theoretical structure factor to the experimental data. For a narrow range of ionizaiton degrees nearly quantitative agreement with the theory is found for the polyacrylic acide system.