Na-cellulose formation in a single cotton fiber studied by synchrotron radiation microdiffraction

A cotton fiber was kept under slight tension and exposed locally to a stream of aqueous 1 N NaOH microdrops of 50 microm diameter. The resulting "macrodrop" of about 300 microm size was at the origin of the formation of Na-cellulose I domains extending about 550 microm from the center of the macrodrop along the fiber. The phase transformation zone between cellulose I and Na-cellulose I was mapped by scanning synchrotron radiation microdiffraction using a 300 nm x 300 nm beam. A stitching technique was used to limit radiation damage. Subsequent exposure of the NaOH containing macrodrop to a stream of H2O or HCl microdrops converted part of the Na-cellulose I back into cellulose I.     

Structural processes during starch granule hydration by synchrotron radiation microdiffraction

Starch granule hydration has been examined on the level of a single potato starch granule by static and dynamic synchrotron radiation (SR) microdiffraction techniques. A cryofrozen, hydrated granule was mapped through a 5 microm SR-beam in order to investigate its internal organization. The edge of the granule showed fiber texture scattering due to radially oriented amylopectin helices. The variation of fiber texture across the granule center supports the model of concentric shells. The crystalline phase appears, however, to increase strongly toward the granule center due to a random amylopectin fraction, which could be related to crystallization of short-range ordered amylopectin during hydration. During gelatinization, the shell structure breaks down and remaining fiber-textured amylopectin domains belong probably to the swollen starch granule envelope. Hydration of a granule was initiated by a microdrop generator and followed in situ by SR-microdiffraction. A fast hydration process with a half time of about 7 s seems to reflect the porous nature of starch granules. The size of the hydrated domains suggests that this process is limited to the level of amylopectin side chain clusters. Longer hydration times are assumed to involve remaining short-range ordered amylopectin and results in larger domains.     

Histological structure of human nail as studied by synchrotron X-ray microdiffraction.

Three layers (characterized by different orientations of the keratin molecules) from the outer to the inner side of human nail were observed by synchrotron X-ray microdiffraction. These layers are associated with the histological dorsal, intermediate and ventral plates. The hair-like type alpha-keratin filaments (81 A in diameter), are only present in the intermediate layer (accounting for approximately 2/3 of the nail width) and are perfectly oriented perpendicular to the growth axis, in the nail plane. Keratin filaments of stratum corneum (epidermis) type, found in the dorsal and ventral cells, are oriented in two privileged directions; parallel and perpendicular to the growth axis. This "sandwich" structure in the corneocytes and the strong intercellular junctions, gives the nail high mechanical rigidity and hardness, both in the curvature direction and in the growth direction. Lipid bilayers (49 A thick) parallel to the nail surface fill certain ampullar dilations of the dorsal plate and intercellular spaces in the ventral plate. Using X-ray micro-diffraction, we show that onychomycosis disrupts the keratin structure, probably during the synthesis phase.     

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

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.     

Deposition and organisation of cell wall polymers during maturation of poplar tension wood by FTIR microspectroscopy

To advance our understanding of the formation of tension wood, we investigated the macromolecular arrangement in cell walls by Fourier transform infrared microspectroscopy (FTIR) during maturation of tension wood in poplar (Populus tremula x P. alba, clone INRA 717-1B4). The relation between changes in composition and the deposition of the G-layer in tension wood was analysed. Polarised FTIR measurements indicated that in tension wood, already before G-layer formation, a more ordered structure of carbohydrates at an angle more parallel to the fibre axis exists. This was clearly different from the behaviour of opposite wood. With the formation of the S₂ layer in opposite wood and the G-layer in tension wood, the orientation signals from the amorphous carbohydrates like hemicelluloses and pectins were different between opposite wood and tension wood. For tension wood, the orientation for these bands remains the same all along the cell wall maturation process, probably reflecting a continued deposition of xyloglucan or xylan, with an orientation different to that in the S₂ wall throughout the whole process. In tension wood, the lignin was more highly oriented in the S₂ layer than in opposite wood.     

Distribution of glucomannans and xylans in poplar xylem and their changes under tension stress

Present work investigated glucomannan (GM) and xylan distribution in poplar xylem cells of normal- (NW), opposite- (OW) and tension wood (TW) with immunolocalization methods. GM labeling was mostly detected in the middle- and inner S(2) (+S(3)) layer of NW and OW fibers, while xylan labeling was observed in the whole secondary cell wall. GM labeling in vessels of NW and OW was much weaker than in fibers and mostly detected in the S(2) layer, whereas slightly stronger xylan labeling than fibers was detected in the whole secondary cell wall of vessels. Ray cells in NW and OW showed no GM labeling, but strong xylan labeling. These results indicate that GMs and xylans are spatially distributed in poplar xylem cells with different concentrations present in different cell types. Surprisingly, TW showed significant decrease of GM labeling in the normal secondary cell wall of gelatinous (G) fibers compared to NW and OW, while xylan labeling was almost identical indicating that the GM and xylan synthetic pathways in fibers have different reaction mechanisms against tension stress. Unlike fibers, no notable changes in GM labeling were detected in vessels of TW, suggesting that GM synthesis in vessels may not be affected by tension stress. GM and xylan was also detected in the G-layer with slightly stronger and much weaker labeling than the normal secondary cell wall of G-fibers. Differences in GM and xylan distribution are also discussed for the same functional cells found in hardwoods and softwoods.     

Microradiosurgical cortical transections generated by synchrotron radiation

PurposeMicroplanar X-ray beams (microbeams) originated by synchrotron sources have been delivered to the visual brain cortex regions in rodents to create microscopically narrow lesions. The effects of microbeams mimic those generated by microsurgical subpial transections (also known as multiple subpial transections) but are obtained in a low-invasive way.MethodsImage-guided atlas-based microbeam cortical transections have been generated on seven 1 month-old Wistar rats. An array of 10 parallel beams of 25 microns in thickness and spaced of 200 micron center-to-center was centered on the visual cortex and deposited an incident dose of 600 Gy.ResultsThe procedure was well tolerated by rats. After recovery, rats showed regular behavior, no sign of gross visual impairment and regular weight gain. After 3 months, rats were sacrificed and brains histologically examined. Cortical transections resembling those obtained through a surgical incision were found over the irradiated region. Remarkable sparing of the cortical columns adjacent to the transections was observed. No sign of radionecrosis was evident at least at this time point.ConclusionsThe visual brain cortex transected by synchrotron-generated microbeams showed an incision-like path of neuronal loss while adjacent non irradiated columns remained intact. These preliminary findings, to be further investigated also using other techniques, suggest that microbeam radiosurgery can affect the cortex at a cellular level providing a potential novel and attractive tool to study cortical function.     

Differences in the time course of proximal and distal airway response to inhaled histamine studied by synchrotron radiation CT.

We studied the kinetics of proximal and distal bronchial response to histamine aerosol in healthy anesthetized and mechanically ventilated rabbits up to 60 min after histamine administration using a novel xenon-enhanced synchrotron radiation computed tomography imaging technique. Individual proximal airway constriction was assessed by measuring the luminal cross-sectional area. Distal airway obstruction was estimated by measuring the ventilated alveolar area after inhaled xenon administration. Respiratory system conductance was assessed continuously. Proximal airway cross-sectional area decreased by 57% of the baseline value by 20 min and recovered gradually but incompletely within 60 min. The ventilated alveolar area decreased immediately after histamine inhalation by 55% of baseline value and recovered rapidly thereafter. The results indicate that the airway reaction to inhaled histamine and the subsequent recovery are significantly slower in proximal than in distal bronchi in healthy rabbit. The findings suggest that physiological reaction mechanisms to inhaled histamine in the airway walls of large and small bronchi are not similar.     

Nuclear forward scattering of synchrotron radiation by deoxymyoglobin

Nuclear forward scattering of synchrotron radiation is used to determine the quadrupole splitting and the mean square displacement of the iron atom in deoxymyoglobin in the temperature range between 50 K and 243 K. Above 200 K an abnormally fast decay of the forward scattered intensity at short times after the synchrotron flash is observed, which is caused by protein-specific motions. The results strongly support the picture that protein dynamics seen at the position of the iron can be understood by harmonic motions in the low temperature regime while in the physiological regime diffusive motions in limited space are present. The shape of the resonance broadening function is investigated. An inhomogeneous broadening with a Lorentzian distribution indicating dipole interactions results in a better agreement with the experimental data than the common Gaussian distribution. Received: 30 August 1999 / Revised version: 22 October 1999 / Accepted: 6 December 1999     

Chemical imaging of poplar wood cell walls by confocal Raman microscopy

Confocal Raman microscopy was used to illustrate changes of molecular composition in secondary plant cell wall tissues of poplar (Populus nigra x Populus deltoids) wood. Two-dimensional spectral maps were acquired and chemical images calculated by integrating the intensity of characteristic spectral bands. This enabled direct visualization of the spatial variation of the lignin content without any chemical treatment or staining of the cell wall. A small (0.5 microm) lignified border toward the lumen was observed in the gelatinous layer of poplar tension wood. The variable orientation of the cellulose was also characterized, leading to visualization of the S1 layer with dimensions smaller than 0.5 mum. Scanning Raman microscopy was thus shown to be a powerful, nondestructive tool for imaging changes in molecular cell wall organization with high spatial resolution.     

Induction of tension wood by 2,4-dinitrophenol and auxins

Summary The effect of DNP and auxins on the development of the secondary xylem in erect stems ofAcer rubrum was studied. DNP affected the development of the secondary xylem only locally in the treated internode. Tension wood is formed in the stem below the DNP treatment site whereas above the application site the development of tracheary elements is altered. InAcer rubrum seedlings that were treated with auxin, especially at low concentrations, a thick ring of tension wood is developed in the erect stem below the treatment site. Previous suggestions that the formation of tension wood in arborescent angiosperms is a developmental response to auxin deficiency are discussed in terms of the induction of tension wood inAcer rubrum by DNP and auxins.The following abbreviations will be used TIBA (2,3,5-tri-iodobenzoic acid) - IAA (indole-3-acetic acid) - GA (gibberellic acid) - NAA (naphthaleneacetic acid) - 2,4-D (2,4-dichlorophenoxyacetic acid) - DNP (2,4-dinitrophenol) This material was included in a doctoral thesis submitted by P. R.Morey to the graduate school of Yale University, New Haven.     

Cloning and expression analysis of a wood-associated xylosidase gene (PtaBXL1) in poplar tension wood

In stems of woody angiosperms responding to mechanical stress, imposed for instance by tilting the stem or formation of a branch, tension wood (TW) forms above the affected part, while anatomically distinct opposite wood (OW) forms below it. In poplar TW the S3 layer of the secondary walls is substituted by a “gelatinous layer” that is almost entirely composed of cellulose and has much lower hemicellulose contents than unstressed wood. However, changes in xylan contents (the predominant hemicelluloses), their interactions with other wall components and the mechanisms involved in TW formation have been little studied. Therefore, in the study reported here we determined the structure and distribution of xylans, cloned the genes encoding the xylan remodeling enzymes β-xylosidases (PtaBXLi), and examined their expression patterns during tension wood, normal wood and opposite wood xylogenesis in poplar. We confirm that poplar wood xylans are substituted solely by 4-O-methylglucuronic acid in both TW and OW. However, although glucuronoxylans are strongly represented in both primary and secondary layers of OW, no 4-O-methylGlcA xylan was found in G-layers of TW. Four full-length BXL cDNAs encoding putative β-xylosidases were cloned. One, PtaBXL1, for which xylosidase activity was confirmed by heterologous expression in Escherichia coli, exhibited a wood-specific expression pattern in TW. In conclusion, xylan as PtaBXL1, encoding β4-xylosidase activity, are down-regulated in TW.     

3D micro-scale deformations of wood in bending: synchrotron radiation muCT data analyzed with digital volume correlation

A micro-scale three-point-bending experiment with a wood specimen was carried out and monitored by synchrotron radiation micro-computed tomography. The full three-dimensional wood structure of the 1.57 × 3.42 × 0.75 mm³ specimen was reconstructed at cellular level in different loading states. Furthermore, the full three-dimensional deformation field of the loaded wood specimen was determined by digital volume correlation, applied to the reconstructed data at successive loading states. Results from two selected regions within the wood specimen are presented as continuous displacement and strain fields in both 2D and 3D. The applied combination of synchrotron radiation micro-computed tomography and digital volume correlation for the deformation analysis of wood under bending stress is a novel application in wood material science. The method offers the potential for the simultaneous observation of structural changes and quantified deformations during in situ micro-mechanical experiments. Moreover, the high spatial resolution allows studying the influence of anatomical features on the fracture behaviour of wood. Possible applications of this method range from bio-mechanical observations in fresh plant tissue to fracture mechanics aspects in structural timber.     

Characteristics of antibacterial molecular activities in poplar wood extractives

As one of the dominant plantations in north and central China, poplar was considered as the uppermost wood raw materials, however, the chemical constituents of poplar wood weren’t effectively used by high added value. Therefore, the molecules of wood extractives in Populus lasiocarpa and Populus tomentosa were extracted and studied to further utilize the bio-resources. The results showed that the LD-010, LD-021, LD-150, LD-174 wood extractives were identified as having 3, 24, 3 27 components, respectively. P. lasiocarpa wood was fit to extract 2,4-hexadiyne, 1,3,3-trimethyl-2-hydroxymethyl-3,3-dimethyl-4-(3-methylbut-2-enyl)-cyclohexene, and P. tomentosa wood was fit to extract 1,5-hexadien-3-yne, (all-E)-2,6,10,15,19,23-hexamethyl-2,6,10,14,18,22-tetracosahexaene. So the extractives of poplar wood contained rich and rare drug and biomedical activities.     

Phases of phosphatidyl ethanolamine monolayers studied by synchrotron x-ray scattering.

For the first time, phospholid monolayers at the air/water interface have been studied by x-ray diffraction and reflection all along the isotherm from the laterally isotropic fluid (the so-called LE phase) to the ordered phases. The model used to analyze the data, and the accuracy of the parameters deduced, were tested by comparing the results obtained with two lipids having the same head group but different chain lengths. Compression of the fluid phase leads predominantly to a change of thickness of the hydrophobic moiety, much less of its density, with the head group extension remaining constant. The main transition involves a considerable increase (approximately 10%) of the electron density in the hydrophobic region, a dehydration of the head group and a positional ordering of the aliphatic tails, albeit with low coherence lengths (approximately 10 spacings). On further compression of the film, the ordered phase undergoes a continuous transition. This is characterized by an increase in positional ordering, a discontinuous decrease in lateral compressibility, a decrease in chain tilt angle with respect to the surface normal towards zero and probably also a head group dehydration and ordering.     

Adsorbate-surface interaction studied by second-harmonic generation in total reflection

We have studied the coherent superposition of nonlinear optical signals due to the substrate background and an organic surface layer deposited on this substrate by second-harmonic generation (SHG). The increased sensitivity of the total reflection geometry used permits identification of subtle details of this superposition; for example partial cancellation of the phase-reversed SH-signals or the observation of a coverage-density-dependent tilt angle of the organic chromophores. The second-harmonic signals from the Langmuir-Blodgett-type monolayers exceed the SH-response of the adsorbates prepared by simple wetting with chloroform solutions of the same amphiphilic dyes by two orders of magnitude under identical coverage-density conditions.     

The comparison of hair from gastric cancer patients and from healthy persons studied by infrared microspectroscopy and imaging using synchrotron radiation

Objective: The objective is to apply synchrotron-based FTIR microspectroscopy and imaging to human hair tissue and investigate the possibility of the method in gastric cancer research and diagnosis. Methods: Human hair from gastric cancer patients’ scalp and normal persons’ scalp were studied by synchrotron-based FTIR microspectroscopy and imaging. Results: The micro-spectra and imaging show the difference between the normal and malignant hair tissues. Obvious peak shift of symmetric phosphate band is observed in micro-spectra of medulla region for the hair tissue of gastric cancer patients. Chemical imaging shows the distributions of lipid and amide II/v_sPO₂^? have changed in the gastric cancer cases. Conclusions: The study indicates that the hair tissue's infrared microspectroscopy and imaging using synchrotron will be a potentially useful method for rapid early gastric cancer diagnosis.