Nanoskaalan rakenteellinen röntgentutkimus geneettisesti muunnellusta lituruohosta

Cellulose is the most abundant natural material on Earth. New ways to utilize the limited resources on Earth for the benefit of the human kind can be found by studying genetically modified plants. The nanoscale structure of organic matter is important to its macroscopic properties. Natural materials can be characterized by measuring the degree of crystallinity in the material and the average dimensions of the crystallites. The cellulose crystallites are helically wound as long fibrous microfibrils in which crystalline and less ordered (amorphous) regions alternate. The microfibril angle (MFA) is the angle of these microfibrils with respect to the cell axis and it is linked with the longitudinal stiffness of the material. A wide-angle X-ray scattering (WAXS) method can be used to study these nanoscale properties of the matter in a non-destructive manner. Arabidopsis thaliana (AT) is an important model system for plant biology. It is a widely spread small flowering plant with a short life cycle and a relatively small genome which has been fully sequenced. X-ray microtomography confirmed that the AT cells are generally round rather than rectangular unlike xylem cells. The cellular structure of the plants was not destroyed in the WAXS measurements. The resolution obtained from the measurements of samples with natural humidity was not sufficient hence all the samples were measured dry. A total of 62 samples were measured with the WAXS set-up, 15 of them wild type plants and the rest genetically modified. In this study the WAXS data analysis methods were enchanced for the benefit of the weakly scattering Arabidopsis samples. The mean crystallite width of all samples ranged from 26 to 30 Å. This is consistent with the crystallite width being determined during the biosynthesis of cellulose. The values for the degree of crystallinity ranged from approximately (20 30)% and all the average values were slightly above 25%. The mean microfibril angle varied greatly between the samples, all the way from 2 to 21 degrees. The mean values of different lines varied more for the MFA than for other properties. Statically significant differences between means of different lines were seen for one line in the degree of crystallinity, for one line in the MFA and for two lines in the crystallite width. Due to small sample sizes these differences should be considered mostly as indicative and not as conclusive evidence on the effects of the genetic modification.Selluloosa on yleisin luonnossa esiintyvä materiaali. Tutkimalla geenimuunneltuja kasveja voidaan löytää uusia tapoja käyttää Maapallon rajallisia resursseja ihmiskunnan hyväksi. Luonnonmateriaalin makroskooppisten ominaisuuksien kannalta on tärkeä tuntea sen rakenne nanometrin tarkkuudella. Materiaalia voidaan tutkia mittaamalla sen kiteisyysastetta ja näiden kiteiden kokoa. Selluloosakiteet ovat kiertyneet soluseinän ympärille pitkiksi kuitumaisiksi mikrofibrilleiksi, jotka muodostuvat kiteisen ja huonommin järjestäytyneen (amorfisen) selluloosan vuorottelevista alueista. Mikrofibrillikulma on se kulma, jonka nämä kuidut muodostavat solun akselin kanssa. Se korreloi materiaalin pitkittäissuuntaisen jäykkyyden kanssa. Laajakulmaröntgensirontamenetelmällä voidaan tutkia näitä nanotason ominaisuuksia näytettä vahingoittamatta. Arabidopsis thaliana (lituruoho) on tärkeä kasvibiologian mallisyystemi. Se on laajalle levinnyt pieni kukkiva kasvi, jolla on sekä lyhyt elämänkierto että suhteellisen pieni ja kauttaaltaan tunnettu genomi. Röntgenmikrotomografialla otetut kuvat vahvistivat, että Arabidopsiksen solut ovat yleisesti ottaen pyöreitä eivätkä suorakulmaisia kuten puusolut. Kasvien solukkorakenne ei tuhoutunut röntgensirontamittauksissa. Luonnollisen kosteuden omaavia näytteitä ei saatu mitattua riittävän tarkasti, joten kaikki näytteet mitattiin kuivina. Laajakulmaröntgensirontamenetelmällä mitattiin yhteensä 62 näytettä, joista 15 oli villin tyypin kasveja ja loput geneettisesti muunneltuja. Tutkimuksessa jatkokehitettiin tämän menetelmän data-analyysimetodeja heikosti sirottavalle lituruoholle sopiviksi. Kaikkien mitattujen näytteiden kiteenleveydet olivat välillä 26-30 Å. Havainto sopii sen kanssa, että kiteenleveydet määräytyvät selluloosan biosynteesissä. Kiteisyysasteen vaihteluväli oli noin (20 30)% ja näytesarjojen keskiarvot olivat hiukan yli 25%. Keskimääräinen mikrofibrillikulma puolestaan vaihteli paljon näytteiden välillä aina kahdesta asteesta 21:een asteeseen ja sarjojen keskiarvotkin vaihtelivat enemmän kuin muiden ominaisuuksien. Tilastollisesti merkittäviä eroja näytesarjojen keskiarvoissa löytyi yhden sarjan kohdalla kiteisyysasteissa, yhden keskimääräisissä mikrofibrillikulmissa ja kahden kohdalla kiteenleveyksissä. Pienen näytekoon takia näitä eroja voidaan pitää lähinnä jatkotutkimuksia ohjaavina eikä sitovina todisteina geenimuuntelun tuloksista

Röntgensirontatutkimuksia kiteisyydestä ja kasvien hierarkkisesta rakenteesta

Plants are highly hierarchical organisms with important structural features at multiple length scales. Wood and plant biomass can be converted into sustainable and renewable form of biofuel at the industrial scale in second generation biorefineries in a way that does not compete with food production. The extraordinary mechanical properties of cellulose can be further exploited by producing novel bio-friendly biocomposite materials. Cellulose is a major constituent in wood (40 45% of its dry mass) and it is found in cell walls in long microfibrils with alternating crystalline and amorphous regions. The microfibrils form a microfibril angle (MFA) with the longitudinal axis of the cell. The average MFA is a strong indicator of macroscopic strength and stiffness. In wood, cellulose is embedded in a matrix of hemicelluloses and lignin. The crystallinity is also related to the macroscopic properties of plant materials with a higher crystallinity suggesting a higher strength. The specific and varied microscopic organization of load-bearing fiber cells and water- and nutrient-carrying supporting cells explains the wide range of variation in the density, size, shape, macroscopic heterogeneity and elastic properties of a broad range of plant materials. Bamboo and balsa have unique characteristics and are studied here as examples of specific plant materials. Bamboo is known for its extremely fast growth and timber-like mechanical properties. Balsa is the lightest wood species in the world but still provides excellent mechanical properties with respect to its mass. Wide-angle X-ray scattering (WAXS) and X-ray microtomography (XMT) are presented here as non-destructive methods to characterize the ultra- and microscopic structure of the plant cell wall. This information should be connected with information obtained from other methods to properly explain the hierarchical structure of plant materials. Specifically, the WAXS sample crystallinity determination and microfibril orientation analysis are discussed. A combination of WAXS and XMT is also shown to yield novel structural information with an application to the tissue-specific localized scattering of Moso bamboo. This in-house localized X-ray scattering, along with X-ray diffraction tomography, is a highly accessible method with unexplored potential for studying plant biology.Kasvien rakenne on hierarkkinen; monien eri kokoluokkien rakenteet yhdessä vaikuttavat kasvin toimintaan ja sen makroskooppisiin ominaisuuksiin. Kasvibiomassasta voidaan tuottaa kestävää ja uusiutuvaa biopolttoainetta uusissa, toisen sukupolven biojalostamoissa ilman merkittäviä haittavaikutuksia ruoan tuotannolle. Selluloosan poikkeuksellisia mekaanisia ominaisuuksia voidaan hyödyntää myös tuottamalla uusia luontoystävällisiä biokomposiittimateriaaleja. Selluloosa on puun tärkeimpiä ainesosia (40 45% sen kuivasta massasta) ja se on soluseinissä pitkinä mikrofibrilleinä, joissa on vuorotellen sekä hyvin järjestyneitä, eli kiteisiä, että huonommin järjestäytyneitä, eli amorfisia osia. Nämä mikrofibrillit muodostavat solun pituusakselin kanssa kulman, jonka keskimääräinen arvo yhdistyy kasvin makroskooppiseen lujuuteen ja jäykkyyteen. Puussa selluloosa on hemiselluloosan ja ligniinin muodostaman rakenteen ympäröimä. Näytteen kiteisyys, eli kiteisen materiaalin osuus koko näytteestä, liittyy myös kasvin makroskooppisiin ominaisuuksiin, sillä suurempi näytteen kiteisyys johtaa suurempaan lujuuteen. Kasvien soluseinässä on paljon eri tehtäviin erikoistuneita soluja, joiden suhteellisen määrän, koon, sijainnin ja rakenteen erot selittävät sen miksi kasvien tiheydessä, koossa, muodossa, rakenteessa ja mekaanisissa ominaisuuksissa voi olla suuria eroja, vaikka ne koostuisivatkin samoista ainesosista. Bambulla ja balsalla on erityisominaisuuksia ja niiden avulla tutkitaan tässä työssä kasvien hierarkkista rakennetta. Bambu on tunnettu erittäin nopeasta kasvustaan sekä monipuolisuudestaan rakennusmateriaalina. Balsa on maapallon kevyin puulaji joten sitä käytetään sovelluksissa, joissa tarvitaan kevyttä, mutta kestävää rakennetta. Laajakulmaröntgensironnalla ja röntgenmikrotomografialla voidaan tutkia kasvin soluseinän rakennetta kasvin rakennetta tuhoamatta. Sironnalla tutkitaan nanorakennetta ja tomografialla solutason rakennetta. Näillä menetelmillä saavutettu rakenteellinen tieto tulisi yhdistää muilla menetelmillä kerättyyn tietoon, jotta kasvin koko hierarkkinen rakenne voidaan selvittää. Tässä työssä tutkittiin erityisesti kiteisyyden ja kiteiden kulmajakauman määrittämistä sironnan avulla. Lisäksi yhdistämällä sirontalaitteisto tomografialaitteistoon saatiin selville uutta rakenteellista tietoa bambun eri solutyyppien nanotason rakenteesta. Käytetty paikallistetuksi sironnaksi nimetty menetelmä ja röntgendiffraktiotomografia ovat nyt uuden, ainutlaatuisen kotilaitteiston ansiosta huomattavasti aikaisempaa helpommin käytettävissä olevia menetelmiä, joita ei ole vielä laajamittaisesti käytetty kasvien rakenteen tutkimisessa

Comparison of sample crystallinity determination methods by X-ray diffraction for challenging cellulose I materials

Cellulose crystallinity assessment is important for optimizing the yield of cellulose products, such as bioethanol. X-ray diffraction is often used for this purpose for its perceived robustness and availability. In this work, the five most common analysis methods (the Segal peak height method and those based on peak fitting and/or amorphous standards) are critically reviewed and compared to two-dimensional Rietveld refinement. A larger () and more varied collection of samples than previous studies have presented is used. In particular, samples () with low crystallinity and small crystallite sizes are included. A good linear correlation () between the five most common methods suggests that they agree on large-scale crystallinity differences between samples. For small crystallinity differences, however, correlation was not seen for samples that were from distinct sample sets. The least-squares fitting using an amorphous standard shows the smallest crystallite size dependence and this method combined with perpendicular transmission geometry also yielded values closest to independently obtained cellulose crystallinity values. On the other hand, these values are too low according to the Rietveld refinement. All analysis methods have weaknesses that should be considered when assessing differences in sample crystallinity.Peer reviewe

Ultrastructural X-ray scattering studies of tropical and temperate hardwoods used as tonewoods

The structure of hardwoods representing eight tropical and five temperate species was characterized from the atomistic level up to the cellular level using X-ray scattering, X-ray microtomography and light microscopy. The species were chosen for this study based on their popularity as tonewoods. The ultrastructure of wood cell walls, including crystallite size, orientation and close-range order of cellulose microfibrils were determined by small- and wide-angle X-ray scattering (SAXS, WAXS). The SAXS patterns were interpreted by using an analytical model of cylinden packed in a hexagonal close-range order with paracrystalline distortion. The values for the cylinder diameters given by this model were compared to the average crystallite widths obtained by WAXS using the Scherrer equation. In six out of z6 samples, all of these representing tropical species used especially in fretboard parts of electric guitars, large differences between these two sizes were obtained. The WAXS and microscopy results of these samples corresponded to tension wood structures. These comparisons and interpretations of SAXS results have not been previously presented for any tropical hardwoods, especially related to those containing tension wood tissue. The importance of the ultrastructural characterization was highlighted in this study in the case of tropical hardwood samples.Peer reviewe

Monitoring the recrystallisation of amorphous xylitol using Raman spectroscopy and wide-angle X-ray scattering

Peer reviewe

Spatially-localized bench-top X-ray scattering reveals tissue-specific microfibril orientation in Moso bamboo

Background : Biological materials have a complex, hierarchical structure, with vital structural features present at all size scales, from the nanoscale to the macroscale. A method that can connect information at multiple length scales has great potential to reveal novel information. This article presents one such method with an application to the bamboo culm wall. Moso (Phyllostachys edulis) bamboo is a commercially important bamboo species. At the cellular level, bamboo culm wall consists of vascular bundles embedded in a parenchyma cell tissue matrix. The microfibril angle (MFA) in the bamboo cell wall is related to its macroscopic longitudinal stiffness and strength and can be determined at the nanoscale with wide-angle X-ray scattering (WAXS). Combining WAXS with X-ray microtomography (XMT) allows tissue-specific study of the bamboo culm without invasive chemical treatment. Results : The scattering contribution of the fiber and parenchyma cells were separated with spatially-localized WAXS. The fiber component was dominated by a high degree of orientation corresponding to small MFAs (mean MFA 11 degrees). The parenchyma component showed significantly lower degree of orientation with a maximum at larger angles (mean MFA 65 degrees). The fiber ratio, the volume of cell wall in the fibers relative to the overall volume of cell wall, was determined by fitting the scattering intensities with these two components. The fiber ratio was also determined from the XMT data and similar fiber ratios were obtained from the two methods, one connected to the cellular level and one to the nanoscale. X-ray diffraction tomography was also done to study the differences in microfibril orientation between fibers and the parenchyma and further connect the microscale to the nanoscale. Conclusions : The spatially-localized WAXS yields biologically relevant, tissue-specific information. With the custommade bench-top set-up presented, diffraction contrast information can be obtained from plant tissue (1) from regions-of-interest, (2) as a function of distance (line scan), or (3) with two-dimensional or three-dimensional tomography. This nanoscale information is connected to the cellular level features.Peer reviewe

Effects of phosphonium-based ionic liquids on phospholipid membranes studied by small-angle X-ray scattering

The effects of ionic liquids on model phospholipid membranes were studied by small-angle X-ray scattering, dynamic light scattering (DLS) and zeta potential measurements. Multilamellar 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine liposomes and large unilamellar vesicles composed of L-alpha-phosphatidylcholine (eggPC) and L-alpha-phosphatidylglycerol (eggPG) (80:20 mol%) or eggPC, eggPG, and cholesterol (60:20:20 mol%) were used as biomimicking membrane models. The effects of the phosphonium-based ionic liquids: tributylmethylphosphonium acetate, trioctylmethylphosphonium acetate, tributyl(tetradecyl)-phosphonium acetate, and tributyl(tetradecyl)-phosphonium chloride, were compared to those of 1-ethyl-3-methyl-imidazolium acetate. With multilamellar vesicles, the ionic liquids that did not disrupt liposomes decreased the lamellar spacing as a function of concentration. The magnitude of the effect depended on concentration for all studied ionic liquids. Using large unilamellar vesicles, first a slight decrease in the vesicle size, then aggregation of vesicles was observed by DLS for increasing ionic liquid concentrations. At concentrations just below those that caused aggregation of liposomes, large unilamellar vesicles were coated by ionic liquid cations, evidenced by a change in their zeta potential. The ability of phosphonium-based ionic liquids to affect liposomes is related to the length of the hydrocarbon chains in the cation. Generally, the ability of ionic liquids to disrupt liposomes goes hand in hand with inducing disorder in the phospholipid membrane. However, trioctylmethylphosphonium acetate selectively extracted and induced a well-ordered lamellar structure in phospholipids from disrupted cholesterol-containing large unilamellar vesicles. This kind of effect was not seen with any other combination of ionic liquids and liposomes. (C) 2016 Elsevier Ireland Ltd. All rights reserved.Peer reviewe

Supercritical water hydrolysis : a green pathway for producing low-molecular-weight cellulose

This work discusses the suitability of supercritical water treatment (SCWT) for depolymerising microcrystalline cellulose in a controlled way. The SCWT partially hydrolysed cellulose down to a mixture of three valuable products: water-insoluble low-molecular-weight cellulose (WI-LMWC) precipitate, water-soluble low-molecular-weight cellulose (WS-LMWC) oligomers, and glucose. The conditions under which the energy demand for obtaining these products is minimised were identified by adjusting the reaction time inside the continuous reactor and the temperature around the critical point. The optimum conditions were 370 degrees C and 0.4 seconds for producing WI-LMWC and 360 degrees C and 0.5 seconds for producing WS-LMWC, with maximum yields of 19 wt% and 50 wt%, respectively. This work also shows that the water-insoluble product precipitates into crystalline cellulose II arrangements. This precipitation phenomenon enabled isolation of cellulose chains of different lengths according to their respective solubilities in ambient water. The results show that SCWT is a relevant process for producing narrowly distributed fractions of low-molecular-weight cellulose using water and heat only.Peer reviewe

Water-induced crystallization and nano-scale spinodal decomposition of cellulose in NMMO and ionic liquid dope

We followed the cellulose structure formation induced by water diffusion into Lyocell dopes based on both N-Methylmorpholine N-oxide (NMMO) and 1,5-diazabicyclo[4.3.0]non-5-ene acetate ([DBNH][OAc], by using scanning simultaneous small- and wide-angle scattering (SAXS-WAXS) experiment along the diffusion gradient. The water content at each point was estimated from the wide-angle scattering profile, giving a binary diffusion constant of the order of 5 × 10−10 m2/sec. In the case of the cellulose solution in NMMO monohydrate, diffraction peaks corresponding to cellulose II appeared concomitantly with the increase in small angle scattering features indicative of nanofibril formation. In the cellulose solution in the ionic liquid, an increase in small angle scattering intensity with the progression of water content appeared at scattering vector q = 0.015 Å−1 corresponding to a correlation length of about 40 nm, indicative of nanometric spinodal decomposition preceding the coagulation process, though no crystalline peak appeared in the wide-angle scattering. Graphical Abstract: [Figure not available: see fulltext.].Peer reviewe