The Experts below are selected from a list of 26628 Experts worldwide ranked by ideXlab platform
Shujun Wang - One of the best experts on this subject based on the ideXlab platform.
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granular structure and allomorph position in c type chinese yam starch granule revealed by sem 13c cp mas nmr and xrd
Food Hydrocolloids, 2009Co-Authors: Shujun Wang, Qinghua Zhu, Fengmin JinAbstract:Abstract The crystalline microstructure and polymorphism of C-type starch from Chinese yam were evaluated by scanning electron microscope (SEM), 13 C cross-polarization magic-angle spinning NMR ( 13 C CP/MAS NMR) and powder X-ray diffraction (XRD) technique and acid hydrolysis method. Morphological changes during acid hydrolysis showed that the amorphous or the less crystalline areas were essentially located at the center part of C-type starch granules whereas the semi-crystalline and amorphous Growth Rings were found mainly in the outer part of the granules. 13 C CP/MAS NMR and XRD results revealed that B-type allomorph was hydrolyzed more rapidly than A-type one. The amorphous or less crystalline areas were predominantly composed of B-allomorph whereas the outer semi-crystalline and amorphous Growth Rings were mostly composed of A-type allomorph. The A- and B-type allomorph coexisted in the individual C-type starch granule. B-type allomorph basically existed at the center part of the granules which was surrounded by the A-type allomorph in the peripheral part of granules.
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the semi crystalline Growth Rings of c type pea starch granule revealed by sem and hr tem during acid hydrolysis
Carbohydrate Polymers, 2008Co-Authors: Shujun WangAbstract:Semi-crystalline Growth Rings and the crystalline lamella of C-type pea starch were studied by Scanning Electron Microscope (SEM) and Field Emission Gun Transmission Electron Microscope (FEG-TEM) during acid hydrolysis. The alternating Growth Rings (semi-crystalline and amorphous Growth Rings) are clearly observed under SEM. The thickness of semi-crystalline Growth Rings is variable and approximately 200 nm apart. SEM results also reveals that the amorphous areas mainly locate core part of C-type starch granules, while the crystalline areas mainly exist in the peripheral region of starch granules. The crystalline and the amorphous areas are hydrolyzed concomitantly, although slowly. The clear lattice fringes with different orientation corresponding to the different thickness of crystalline lamella were observable from high-resolution-TEM (HR-TEM) images. The crystalline lamella size can be confirmed to be about 20 nm with the length of 20 nm and the thickness of 20 nm. The clear lattice fringes should correspond to the crystalline phases in the semi-crystalline Growth Rings while the blurry regions correspond to the amorphous Growth Rings among the semi-crystalline Growth Rings.
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conformation and location of amorphous and semi crystalline regions in c type starch granules revealed by sem nmr and xrd
Food Chemistry, 2008Co-Authors: Shujun WangAbstract:The conformations and locations of amorphous and semi-crystalline regions in C-type starch granules from Chinese yam were evaluated by a combination of morphology and spectroscopy studies during acid hydrolysis. Scanning electron micrographs showed that amorphous or less crystalline areas were essentially located in the centre part of C-type starch granules, whereas the semi-crystalline and amorphous Growth Rings were found mainly in the outer part of the granules. (13)C cross-polarization magic angle spinning NMR ((13)C CP/MAS NMR) showed that amorphous regions were hydrolyzed faster than the crystalline ones. In addition, B-type polymorphs were shown to be hydrolyzed more rapidly than A-types. Powder X-ray diffraction (XRD) also revealed that the B-polymorph was hydrolyzed more rapidly than the A-type. XRD showed that the amorphous or less crystalline areas were mainly located in the core of starch granules, while the amorphous Growth Rings are distributed toward the outside of the granules and alternatively arranged with semi-crystalline Growth Rings. The amorphous or less crystalline areas predominantly consisted of the B-polymorph whereas the outer semi-crystalline and amorphous Growth Rings were mostly composed of the A-polymorph.
Zhuo Feng - One of the best experts on this subject based on the ideXlab platform.
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leaf phenology paleoclimatic and paleoenvironmental insights derived from an agathoxylon stem from the middle jurassic of xinjiang northwest china
Review of Palaeobotany and Palynology, 2021Co-Authors: Xudong Gou, Haibo Wei, Yun Guo, Shiling Yang, Zhuo FengAbstract:Abstract Fossil wood serves as a natural data source for deciphering plant physiological features and paleoclimatic and paleoenvironmental conditions experienced during its lifespan. Although permineralized conifer wood commonly occurs in the Jurassic of Xinjiang Uygur Autonomous Region (Xinjiang), Northwest China, their physiological features and paleoclimatic and paleoenvironmental significance have been rarely studied. Here, we quantitatively analyzed the anatomical characteristics of a permineralized conifer stem (Agathoxylon sp.) from the Middle Jurassic Xishanyao Formation in Naomaohu Town of Yiwu County, Hami City, Xinjiang. The fossil stem is only preserved with secondary xylem. The secondary xylem is pycnoxylic and exclusively composed of tracheids and parenchymatous rays. Tracheids have mostly uniseriate or biseriate, partially triseriate or tetraseriate, alternately or sub-oppositely arranged bordered pits on their radial walls. Rays are mostly uniseriate, partially biseriate, and are up to 27 cells high. There are 4 to 11 cupressoid pits in each cross field, arranged in the araucarioid type. Growth Rings are distinct and wide. The mean sensitivity and ring markedness index analyses of Growth Rings suggest that a stable paleoclimate with regular seasonal fructifications could have prevailed in the Santanghu Basin during the Middle Jurassic. Statistical analyses of cell diameters in 11 successive Growth Rings indicate that this fossil plant was deciduous. Our study sheds new light on leaf phenology and paleoclimatic and paleoenvironmental conditions of Middle Jurassic conifer plants.
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wood decay of xenoxylon yunnanensis feng sp nov from the middle jurassic of yunnan province china
Palaeogeography Palaeoclimatology Palaeoecology, 2015Co-Authors: Zhuo Feng, Haibo Wei, Chunling Wang, Yuxuan Chen, Jiajia Shen, Jiyuan YangAbstract:Abstract A permineralised gymnosperm wood, Xenoxylon yunnanensis Feng sp. nov., is described from the Middle Jurassic Shaximiao Formation in Huize County, Yunnan Province, Southwest China. The pycnoxylic wood consists of thick-walled tracheids and thin-walled rays. It is characterised by uniseriate, contiguous, compressed bordered pits on the radial walls of tracheids, and one large simple pit in each cross-field. Growth Rings exhibit narrow latewood. The mean sensitivity of analysis of 25 Growth Rings is 0.2, suggesting that a climate with abundant rainfall and weak seasonality could have prevailed in Yunnan, at least locally, during the Middle Jurassic. The outer portion of the wood is largely decayed, and shows poorly preserved cells lacking details. Decayed tracheids displaying various features, including removal of middle lamellae, separations of secondary walls, presence of thickened corners and appositions, are recognised as cell reactions to fungal activity. Irregularly distributed micro-cavities are formed by complete decomposition of tracheids and rays in the wood. Abundant fungal remains occurring in the wood generally consist of multiple branched hyphae. These fungal hyphae are either confined to individual cell lumens or extend through adjacent cells. Although the probable reproductive structure and typical clamp connection are very rarely observed with few septate hyphae, the affinities of these fungal hyphae are somewhat obscure. Nevertheless, our study sheds light on the palaeoecology of Middle Jurassic terrestrial ecosystems of Southwest China.
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zalesskioxylon xiaheyanense sp nov a gymnospermous wood of the stephanian late pennsylvanian from ningxia northwestern china
Journal of Asian Earth Sciences, 2008Co-Authors: Zhuo Feng, Jun Wang, Guanglong ShenAbstract:Abstract A new Late Pennsylvanian species of gymnospermous fossil wood, Zalesskioxylon xiaheyanense sp. nov. is described from the Lower Taiyuan Formation (Stephanian B-C) near the village of Xiaheyan, Ningxia Hui Autonomous Region, northwestern China. The specimen consists only of silicified secondary xylem. The tracheids are pycnoxylic with 2–3 seriate bordered pits, arranged in subcircular or hexagonal alternate (araucaroid) pattern. The pores of the pits are small, linear, and regularly tilted. Xylem rays are homogeneous, uniseriate, 1–25 cells high. Cross-fields are filled with numerous mixed simple pits of various sizes. Growth Rings, axial parenchymatous elements and resin canals are absent. The geographic distribution of Zalesskioxylon woods is reviewed. Zalesskioxylon xiaheyanense sp. nov. grew at low latitudes, and because of the lack of Growth Rings, probably lived under relatively uniform climatic conditions. Our new species supplements the poorly known distribution of Carboniferous wood in China.
Elliot P Gilbert - One of the best experts on this subject based on the ideXlab platform.
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characterisation of large scale structures in starch granules via small angle neutron and x ray scattering
Carbohydrate Polymers, 2013Co-Authors: James Doutch, Elliot P GilbertAbstract:Small angle scattering (SAS) techniques have a distinguished track record in illuminating the semi-crystalline lamellar structure of the starch granule. To date, there have been few attempts to use SAS techniques to characterise larger-scale structures reported from imaging techniques such as Growth Rings, blocklets or pores, nor how these structures would modulate the well-known scattering arising from the semi-crystalline lamellar structure. In this study, SAS data collected over an extended q range were gathered from dry and hydrated starch powders from varied botanical sources. The use of neutrons and X-rays, as well as comparing dry and hydrated granules, allowed different levels of contrast in scattering length density to be probed and therefore selected structural regions to be highlighted. The lowest q range, 0.002-0.04 A(-1), was found to be dominated by scattering from the starch granules themselves, especially in the dry powders; however an inflection point from a low contrast structure was observed at 0.035 A(-1). The associated scattering was interpreted within a unified scattering framework with the inflexion point correlating with a structure with radius of gyration ~90 A - a size comparable to small blocklets or superhelices. In hydrated starches, it is observed that there is an inflection point between lamellar and q(-4) power-law scattering regions at approximately 0.004 A(-1) which may correlate with Growth Rings and large blocklets. The implications of these findings on existing models of starch lamellar scattering are discussed.
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effect of enzymatic hydrolysis on native starch granule structure
Biomacromolecules, 2010Co-Authors: Jaroslav Blazek, Elliot P GilbertAbstract:Enzymatic digestion of six starches of different botanical origin was studied in real time by in situ time-resolved small-angle neutron scattering (SANS) and complemented by the analysis of native and digested material by X-ray diffraction, differential scanning calorimetry, small-angle X-ray scattering, and scanning electron microscopy with the aim of following changes in starch granule nanostructure during enzymatic digestion. This range of techniques enables coverage over five orders of length-scale, as is necessary for this hierarchically structured material. Starches studied varied in their digestibility and displayed structural differences in the course of enzymatic digestion. The use of time-resolved SANS showed that solvent-drying of digested residues does not induce any structural artifacts on the length scale followed by small-angle scattering. In the course of digestion, the lamellar peak intensity gradually decreased and low-q scattering increased. These trends were more substantial for A-type than for B-type starches. These observations were explained by preferential digestion of the amorphous Growth Rings. Hydrolysis of the semicrystalline Growth Rings was explained on the basis of a liquid-crystalline model for starch considering differences between A-type and B-type starches in the length and rigidity of amylopectin spacers and branches. As evidenced by differing morphologies of enzymatic attack among varieties, the existence of granular pores and channels and physical penetrability of the amorphous Growth ring affect the accessibility of the enzyme to the substrate. The combined effects of the granule microstructure and the nanostructure of the Growth Rings influence the opportunity of the enzyme to access its substrate; as a consequence, these structures determine the enzymatic digestibility of granular starches more than the absolute physical densities of the amorphous Growth Rings and amorphous and crystalline regions of the semicrystalline Growth Rings.
William Helbert - One of the best experts on this subject based on the ideXlab platform.
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internal structure of the starch granule revealed by afm
Carbohydrate Research, 2001Co-Authors: A A Baker, Mervyn J Miles, William HelbertAbstract:Atomic force microscopy images of sectioned native corn starch granules show evidence of the well-known radial organisation of the starch macromolecules, with the less-ordered hilum region near to the centre. Native granules show blocks 400-500 nm in size that span the Growth Rings. Lintnerised starch granules, where a mild acid hydrolysis has been used to remove the amorphous and less crystalline parts of the granule, clearly show smaller 'blocklets' within the Rings approximately 10-30 nm in size. This level of organisation within the Growth Rings corresponds to the blocklet or superhelix structures that have been proposed in the literature for the association or clustering of amylopectin helices. Mechanical property imaging techniques have provided enhanced contrast to view this morphology, and shown the deformability of the starch structure under contact mode imaging conditions.
Alberto Schiraldi - One of the best experts on this subject based on the ideXlab platform.
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structural parameters of amylopectin clusters and semi crystalline Growth Rings in wheat starches with different amylose content
Carbohydrate Research, 2004Co-Authors: Vladimir P Yuryev, Alexei V Krivandin, Valentina I Kiseleva, L A Wasserman, Natalia K Genkina, J Fornal, Wioletta Blaszczak, Alberto SchiraldiAbstract:Small-angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) were used to investigate the internal structure of wheat starch granules with different amylose content. Different approaches were used for treatment (interpretation) of SAXS data to assess the values of structural parameters of amylopectin clusters and the size of crystalline and amorphous lamella in different wheat starches. The average values of the semi-crystalline Growth Rings thickness in starches have been determined and the relationship between structural characteristics and thermodynamic melting parameters is discussed.
