Pinus radiata is by far the dominant species grown in New Zealand plantations as a renewable source of wood. Several wood quality issues have been identified in the material produced, including the high incidence of compression wood, which is undesirable for end users. At present our understanding of the complex array of developmental processes involved in wood formation (which has a direct bearing on wood quality) is limited. Hence, the forest industry is interested in attaining a better understanding of the processes involved. Towards this goal, and for reasons of biological curiosity, the experiments described in this thesis were carried out to investigate several aspects of xylem cell development. In an in arbor study, changes in the orientation of cortical microtubules and cellulose microfibrils were observed in developing tracheids. Results obtained provide evidence that cortical microtubules act to guide cellulose synthase complexes during secondary wall formation in tracheids. The mechanisms involved in controlling cell wall deposition in wood cells are poorly understood, and are difficult to study, especially in arbor. A major part of this thesis involved the development of an in vitro method for culturing radiata pine wood in which hormone levels, nutrients, sugars and other factors, could be controlled without confounding influences from other parts of the tree. The method developed was used in subsequent parts of this thesis to study compression wood development, and the influence of the hormone gibberellin on cellulose microfibril organisation in the cell wall. Results from the in vitro compression wood experiments suggested that: 1. when a tree is growing at a lean, the developing cell wall was able to perceive compressive forces generated by the weight of the rest of the tree, rather than perceive the lean per se. 2. ethylene, rather than auxin, was involved in the induction of compression wood. Culture of stem explants with gibberellin resulted in wider cells, with steeper cortical microtubules, and correspondingly steeper cellulose microfibrils in the S2 layer of developing wood cells. This observation provides further evidence that the orientation of microtubules guides the orientation of cellulose microfibrils. Overall, the work described in this thesis furthers our knowledge in the field of xylem cell development. The stem culture protocol developed will undoubtedly provide a valuable tool for future studies to be carried out.

Patterns of cellulose deposition within the cell wall directly affect the size and shape of plant cells, in turn affecting the overall structure of the plant. In the primary wall of Nitella, and in the walls of many other algae and higher plants, a correspondence has been observed between the organization of cellulose microfibrils and cortical microtubules, each lying on opposite sides of the plasma membrane. The present work examines the development of the secondary wall in maturing Nitella internodal cells in an attempt to determine whether a relationship exists between cellulose microfibril organization and the organization of cortical microtubules. Treatments that artificially rearrange or remove microtubules were used, and effects on cellulose organization in the cell wall were examined through the use of transmission electron microscopy in thin sections and by the replica technique. Removal of microtubules in very young cells had a randomizing effect on cellulose organization, but absence of microtubules or their rearrangement did not prevent the formation of secondary walls with characteristic helicoidal patterns. The findings on the timing of helicoidal development in Nitella and the appearance of the innermost surface of helicoidal layers are discussed in relation to models of helicoidal architecture.

京都大学 / 新制・課程博士 / 博士(農学) / 甲第24661号 / 農博第2544号 / 新制||農||1098(附属図書館) / 学位論文||R5||N5442(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 矢野 浩之, 教授 和田 昌久, 教授 今井 友也 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

A hérnia inguinal é uma doença multifatorial que emerge do orifício de Fruchaud, fechado somente pela fáscia transversal. Nos últimos tempos tem sido demonstrado que desordens dos elementos do tecido conjuntivo, como fibras colágenas e elásticas, estão relacionados com a gênese da hérnia inguinal. Estudos prévios demonstraram alterações estruturais e quantitativas das fibras elásticas com o envelhecimento da fáscia transversal, relacionado ao aparecimento de hérnia inguinal a partir da quinta década da vida. Estudos recentes demonstraram associação entre uma mutação pontual do éxon 20 do gene da elastina, componente amorfo das fibras elásticas, e hérnia inguinal em indivíduos do sexo masculino. A fibrilina-1 é o principal componente microfibrilar das fibras elásticas e está relacionada ao surgimento de síndromes genéticas, como Marfan, Ehlers-Danlos e Williams, que também apresentam indivíduos portadores de hérnias. Nesse sentido, o objetivo do presente estudo foi investigar a presença de polimorfismos no gene da fibrilina-1 (FBN1) em indivíduos portadores de hérnia inguinal. Estudou-se o ácido desoxirribonucléico (DNA) genômico de 60 pacientes com hérnia inguinal e 60 controles. Os exons 4, 13, 24, 25, 26, 27, 31 32, 39, 41, 59 e 65 foram amplificados pela Reação em Cadeia da Polimerase e, posteriormente, foram avaliados os polimorfismos em gel de poliacrilamida. Todos os exons estudados apresentaram alguns indivíduos com padrão de bandeamento diverso. O produto de amplificação destes exons foi então avaliado através de seqüenciamento e confrontado com a base de dados do National Human Genome Research Institute. Alterações de inserção e/ou deleção consistentes foram observadas no éxon 27: 1) inserção de uma base entre os codons 1119 e 1120 (GAT -> AGA); 2) inserção de uma base entre os codons 1116 e 1117 (TGT -> CTG): 3) inserção de uma base no códon 1148 (CCC -> CGC); e no éxon 31: inserção de uma base entre os codons 1282 e 1283 (GAG -> CGA). Não houve significância estatística que indique associação entre o gene FBN1 e hérnia inguinal. Entretanto, como o gene da fibrilina-1 é bastante grande (350 kD, dividido em 65 exons) e, em outras doenças como a Síndrome de Marfan mais de 500 mutações já foram descritas, sem haver exons que possuam uma maior responsabilidade pela Síndrome, é possível que outros exons possam estar relacionados com o acometimento da hérnia inguinal. / The inguinal hernia is a multifactorial disease that emerge from the Fruchaud orifice, closed only by the transversalis fascia. Lately it has been showed that disorders on the connective tissue elements, as the collagen and elastic fibers, are related to the inguinal hernia genesis. Previous studies have showed structural and quantitative changes of the elastic fibers at the transversalis fascia with aging, that may be related to inguinal hernia at the fifth decade of life. Recent studies have demonstrated an association among a punctual mutation on exon 20 of the elastin gene, amorfous component of the elastic fibers, and male individuals with inguinal hernia. The fibrillin-1 is the main microfibrillar component of the elastic fibers and is associated to genetic syndromes as Marfan, Ehlers-Danlos and Williams, that also present inidividuals with hernias. Thus, the objective of this study was to investigate the presence of polymorphisms on the fibrillin-1 gene (FBN1) on individuals who developed inguinal hernia. The desoxirribonucleic acid (DNA) of 60 individuals with inguinal hernia and 60 controls have been studied. The exons 4, 13, 24, 25, 26, 27, 31, 32, 39, 41, 59 and 65 were amplyfied by the Polymerase Chain Reaction and later evaluated the polymorphisms on polyacrilamide gel. The amplification product of these exons were evaluated by DNA sequencing and compared to the National Human Genome Research Institute database. Consistent mutations were observed at exon 27: 1) insertion of a base between codons 1119 and 1120 (GAT -> AGA); 2) insertion of a base between codons 1116 and 1117 (TGT -> CTG); 3) insertion of a base on codon 1148 (CCC -> CGC); and at exon 31: insertion of a base between codons 1282 and 1283 (GAG -> CGA). There was no statistic significance that could indicate the association between FBN1 gene and inguinal hernia. However, FBN1 is a large gene (350 kD, shared in 65 exons) and in other disorders as Marfan Syndrome, more than 500 mutations have already been described, without the existence of prevalent exons that have major responsability about the Syndrome, it is possible that other exons could be related to the happening of inguinal hernia.

Le cadre de cette étude est le coût énergétique lié à la production des Microfibrilles de Cellulose (MFC) qui est aujourd’hui un facteur limitant à son développement à l’échelle industrielle. Le but de cette étude est de caractériser les interactions cellulose/hémicellulose au sein de ces systèmes.Des MFC provenant de différentes pâtes à papier chimiques ont été caractérisées par RMN du solide afin d’obtenir des informations à l’échelle moléculaire. Suite à l’optimisation d’un protocole expérimental, les hémicelluloses contenues dans les MFC issues de pâte kraft de bouleau ont ensuite été extraites avec un rendement de 60% et sont composés uniquement d’un homopolymère de xylan de DP 75.La turbidimétrie a été utilisée pour qualifier la qualité des suspensions, dont il a été montré qu’elle dépend fortement du procédé de mise en pâte et du séchage. Des corrélations positives ont été établies entre l’état de dispersion et les propriétés mécaniques de feuilles de papier additionnées de microfibrilles. L’analyse RMN de modèles biomimétiques reconstitués a confirmé le changement de conformation du xylan lorsqu’il est adsorbé sur la cellulose et les mesures de surface spécifique ont montré que seule la couche de xylan en contact avec la cellulose était concernée par ce changement.Les interactions cellulose/xylane ont été étudiées par RMN du solide et par dynamique moléculaire atomistique (MD). Les simulations MD ont montré que le xylan s’adsorbe parallèlement aux chaines de cellulose. Des mesures d'interaction sur ce système ont conduit à une mesure d'énergie de 9kJ/résidu de xylose.Des tests de mesure d’adhésion ont également été réalisés à partir d’un modèle trois couches constitué de xylan entre deux films de cellulose et une forte adhésion a pu être observée.L’utilisation de xylanase comme prétraitement est proposé pour améliorer la production des MFC. / The study was motivated by the necessity to reduce the high energy costs of Micro-Fibrillated Cellulose (MFC) production, which is a limiting factor for its industrial development and aimed at understanding the cellulose/hemicelluloses interaction within this system. MFC resulting from different chemical pulps were characterized by solid-state NMR spectroscopy to get information on the hemicelluloses content and molecular conformation. By optimizing an extraction protocol, more than 60% of the residual hemicelluloses were extracted from birch kraft MFC and characterized as a high purity homopolymer of β-1,4 linked xylan of DP 75.Turbidimetry was used to qualify the quality of the suspensions, which strongly depended on the pulping and drying history. Positive correlations between the state of dispersion, specific surface and mechanical properties of MFC-reinforced handsheets were evidenced.Cellulose/xylan interactions were investigated using solid-state NMR and atomistic molecular dynamics (MD) simulation. NMR spectra confirmed that xylan in contact with cellulose altered its conformation, from the three-fold helix to a presumable cellulose-like two-fold one. In combination with specific surface area measurements, the conformational change was shown to happen only for the first layer of xylan adsorbed in direct interaction with the cellulose surface. MD simulations showed that adsorbed xylan tends to align parallel to the cellulose chain direction fully extended. Interaction energy between xylan chain and cellulose surface estimated with MD was 9kJ/xylose. Then a three-layers system made of xylan between two cellulose films were built to perform adhesion tests that showed strong adhesion between xylan and cellulose surfaces. Xylanase was proposed as a pulp pretreatment for MFC production.

Les fibres élastiques sont constituées d'élastine et de microfibrilles riches en fibrilline-1, dont les mutations génétiques respectives conduisent à des pathologies cardiovasculaires graves impliquant l'apparition de sténoses (syndrome de Williams-Beuren, WBS) ou d'anévrismes (syndrome de Marfan, MS) aortiques. Nous avons étudié et comparé les effets de l'élastine (kappa-élastine, kE et tropoélastine recombinante, rTE) et des microfibrilles (MF et le fragment PF14 de la fibrilline-1) sur la signalisation dans les cellules vasculaires. Sur les cellules endothéliales de la veine ombilicale humaine (HUVEC), la kE, la rTE et les MF activent le complexe récepteur de l'élastine (ECR) et les intégrines, la production de messagers intracellulaires et, avec une efficacité variable, des canaux calciques de la membrane cellulaire et du réticulum endoplasmique, mobilisant à la fois le calcium intra- et extra-cellulaire. Les microfilaments d'actine ne sont impliqués que dans le cas de la signalisation liée à l'élastine. Toutes les protéines étudiées augmentent aussi la prolifération et l'adhésion des HUVEC, ainsi que la production ou la dégradation –à travers l'activation de métalloprotéases matricielles (MMP)- de plusieurs composés de la matrice extracellulaire. La capacité de migration des HUVEC est augmentée par la kE, rTE et PF14 alors qu'elle est diminuée par les MF. Aussi, chez le rat, ces protéines induisent une synthèse de l'oxyde nitrique (NO) par les cellules endothéliales, résultant en une vasodilatation aortique. PF14 présente de plus un pouvoir vasocontractant en absence de l'endothélium indiquant qu'il stimule aussi particulièrement les cellules musculaires lisses vasculaires (CMLVs). Pour étudier ces interactions sur modèle cellulaire, un protocole de culture de CMLVs d'aorte de souris adultes, âgées, ou déficientes pour les gènes de l'élastine ou de la fibrilline-1, a été mis au point. Les protéines des fibres élastiques produisent dans ces cellules une montée du niveau de calcium intracellulaire dont les caractéristiques varient suivant la protéine, l'âge ou le génotype des animaux. Ces travaux confirment le rôle majeur de l'élastine et de la fibrilline-1 dans la régulation des fonctions des cellules vasculaires. Malgré quelques différences, les fragments d'élastine et de fibrilline-1 stimulent souvent de manière similaire les cellules vasculaires. Ceci suggère que les symptômes contradictoires observés dans les MS et WBS mettent aussi en cause des facteurs additionnels, probablement liés à d'autres signalisations, par exemple à la voie du TGF-β ou aux différences de mécanisme et de cinétique du dépôt de l'élastine et de la fibrilline-1 lors de l'assemblage des fibres élastiques. / Elastic fibres are composed of elastin and fibrillin-1 rich microfibrils, whose genetic mutations result in severe cardiovascular pathologies characterized by aortic stenosis (Williams syndrome, WS) or aneurysm (Marfan Syndrom, MS), respectively. We studied and compared the effect of elastin (kappa-elastin, kE and recombinant tropoelastin, rTE) and microfibrils (MF and PF14, fibrillin-1 fragment) on vascular cell signaling. In human umbilical vein endothelial cells (HUVEC), kE, rTE and MF activated the elastin complex receptors (ECR) and integrins, the production of intracellular messengers and, with varying efficiencies, membrane and endoplasmic reticulum calcium channels, mobilizing both intra- and extra-cellular calcium. Actin microfilaments were involved only in the case of elastin signaling. All these proteins enhanced the proliferation and adhesion of HUVECs, as well as synthesis or degradation –through matrix metalloproteinanse (MMP) activation- of several extracellular matrix components. HUVEC migration was enhanced by kE, rTE and PF14 and diminished by MF. Also, in rats, these proteins induced nitric oxide (NO) synthesis by endothelial cells, resulting in aortic vasodilatation, although PF14 had an additional constrictor effect on endothelium-free aorta, indicating that PF14 also stimulates vascular smooth muscle cells (VSMCs). To study these interactions in a cellular model, we designed a new protocol to culture VSMCs from aorta of adult, aged, and elastin or fibrillin-1 knock-out mice. Elastic fibre proteins induced an increase in VSMC intracellular calcium level, which characteristics varied with the protein, age and genotype of mice. These findings confirm the major role of elastin and fibrillin-1 in the regulation of vascular cell functions. Despite some differences, elastin and fibrillin-1 often stimulated vascular cells similarly. This suggests that the onset of the contradictory features observed in MS and WS also involve additional factors, probably linked to other signaling pathways, for instance the TGF-β pathway or the differences in the mechanism and kinetic of elastin and fibrillin-1 depositions during elastic fiber assembly.

Orientador: Cláudio Chrysóstomo Werneck / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-16T09:01:31Z (GMT). No. of bitstreams: 1 Machado_Denise_M.pdf: 1404386 bytes, checksum: e811cae8e94f35d5b473fe2881261fd8 (MD5) Previous issue date: 2010 / Resumo: Nos últimos anos, o principal objetivo de nosso laboratório é esclarecer a participação da GlicoProteína Associada a Microfibrila-1 (MAGP-1) na formação de trombos no modelo de trombose arterial fotoquímica. Dados indicam que a MAGP-1 não interage diretamente com as plaquetas, importante componente na trombose arterial, mas que, provavelmente, a MAGP-1 esteja interagindo com uma molécula que tenha participação neste processo. Neste sentido, a interação da MAGP-1 com moléculas importantes na formação do trombo foi estudada. A MAGP-1 tem a capacidade de interagir com o fator de von Willebrand, bem como com fibrinogênio e fibronectina. Além disto, foi verificado que a injeção da MAGP-1 recombinante em camundongos deficientes em MAGP-1 é capaz de reestabelecer o tempo normal de formação de trombos nestes animais. Considerando a ausência da MAGP-1 e seu efeito na formação de trombos, foi questionado se a morfologia dos trombos obtidos em camundongos deficientes em MAGP-1 era diferente dos trombos obtidos em camundongos selvagens. Dados iniciais sugeriam que os trombos de camundongos deficientes em MAGP-1 apresentavam ultraestrutura diferente, onde um número maior de plaquetas apresentavam aparentemente, os seus grânulos e corpos densos intactos, sugerindo uma ativação ineficiente na ausência de MAGP-1. No presente trabalho, além de análise ultraestrutural mais detalhada, foram feitos estudos para determinar qual a região da MAGP-1 é responsável pela atividade trombogênica. Neste sentido, proteínas mutadas, truncadas e peptídeos derivados da MAGP-1 foram obtidos e então injetados nos camundongos selvagens e deficientes em MAGP-1. Como resultados, pudemos observar que os trombos dos camundongos selvagens bem como dos camundongos deficientes em MAGP-1 apresentam basicamente a mesma morfologia, levando em consideração as técnicas utilizadas, microscopia eletrônica de transmissão e varredura. Em relação ao mapeamento dos domínios, quando utilizada a molécula inteira, seja de camundongo, seja bovina, o tempo normal de oclusão foi reestabelecido. A injeção da forma truncada da região carboxiterminal foi suficiente para obter este mesmo resultado que está principalmente relacionado a um peptídeo também determinado. O mecanismo pelo qual este peptídeo atua normalizando o tempo de oclusão normal ainda não é conhecido e será objeto de estudos futuros / Abstract: In the last years, the main purpose of our laboratory has been to clarify the participation of the Microfibril-Associated GlycoProtein-1 (MAGP-1) in forming thrombus in photochemically-induced artery thrombosis model. It was considered that MAGP-1 does not interact directly with platelets, important component in artery thrombosis and probably MAGP-1 is interacting with a molecule which has participation in this process. In this sense, the interaction of the MAGP-1 with important molecules in the thrombus formation was studied. The MAGP-1 has the ability to interact with von Willebrand factor, as well as with fibrinogen and fibronectin. In addition, it was verified that the injection of recombinant MAGP-1 in MAGP-1-deficient mice was able to restores normal time of thrombus formation in these animals. Considering the MAGP-1 absence and its effect on the thrombi formation, it was questioned whether thrombi morphology obtained from MAGP-1-deficient mice was different from thrombi obtained from wild-type mice. Initial data suggested that the thrombi from MAGP-1-deficient mice had different structure, where platelets apparently showed their intact granules and dense bodies, suggesting an inefficient activation in the MAGP-1 absence. In this work, besides the ultra-structural analysis, more detailed studies have been made to determine which region of the MAGP-1 is responsible for the thrombogenic activity. In this sense, truncated proteins, mutated proteins and peptides, were obtained and then injected into MAGP-1-deficient mice to verify their activities. As result, we noticed that the thrombi have similar structure taking into consideration used techniques, scanning electron microscopy and transmission electron microscopy. Furthermore, in relation to MAGP-1 mapping domains studies when we inject recombinant full-length molecule either mice or bovine, the normal time occlusion was restored. The injection of carboxy-terminal region was enough to get this same result what is mainly related to an also determined peptide. Mechanisms involved in this process are unknown and will be our aim in the future studies / Mestrado / Bioquimica / Mestre em Biologia Funcional e Molecular

A hérnia inguinal é uma doença multifatorial que emerge do orifício de Fruchaud, fechado somente pela fáscia transversal. Nos últimos tempos tem sido demonstrado que desordens dos elementos do tecido conjuntivo, como fibras colágenas e elásticas, estão relacionados com a gênese da hérnia inguinal. Estudos prévios demonstraram alterações estruturais e quantitativas das fibras elásticas com o envelhecimento da fáscia transversal, relacionado ao aparecimento de hérnia inguinal a partir da quinta década da vida. Estudos recentes demonstraram associação entre uma mutação pontual do éxon 20 do gene da elastina, componente amorfo das fibras elásticas, e hérnia inguinal em indivíduos do sexo masculino. A fibrilina-1 é o principal componente microfibrilar das fibras elásticas e está relacionada ao surgimento de síndromes genéticas, como Marfan, Ehlers-Danlos e Williams, que também apresentam indivíduos portadores de hérnias. Nesse sentido, o objetivo do presente estudo foi investigar a presença de polimorfismos no gene da fibrilina-1 (FBN1) em indivíduos portadores de hérnia inguinal. Estudou-se o ácido desoxirribonucléico (DNA) genômico de 60 pacientes com hérnia inguinal e 60 controles. Os exons 4, 13, 24, 25, 26, 27, 31 32, 39, 41, 59 e 65 foram amplificados pela Reação em Cadeia da Polimerase e, posteriormente, foram avaliados os polimorfismos em gel de poliacrilamida. Todos os exons estudados apresentaram alguns indivíduos com padrão de bandeamento diverso. O produto de amplificação destes exons foi então avaliado através de seqüenciamento e confrontado com a base de dados do National Human Genome Research Institute. Alterações de inserção e/ou deleção consistentes foram observadas no éxon 27: 1) inserção de uma base entre os codons 1119 e 1120 (GAT -> AGA); 2) inserção de uma base entre os codons 1116 e 1117 (TGT -> CTG): 3) inserção de uma base no códon 1148 (CCC -> CGC); e no éxon 31: inserção de uma base entre os codons 1282 e 1283 (GAG -> CGA). Não houve significância estatística que indique associação entre o gene FBN1 e hérnia inguinal. Entretanto, como o gene da fibrilina-1 é bastante grande (350 kD, dividido em 65 exons) e, em outras doenças como a Síndrome de Marfan mais de 500 mutações já foram descritas, sem haver exons que possuam uma maior responsabilidade pela Síndrome, é possível que outros exons possam estar relacionados com o acometimento da hérnia inguinal. / The inguinal hernia is a multifactorial disease that emerge from the Fruchaud orifice, closed only by the transversalis fascia. Lately it has been showed that disorders on the connective tissue elements, as the collagen and elastic fibers, are related to the inguinal hernia genesis. Previous studies have showed structural and quantitative changes of the elastic fibers at the transversalis fascia with aging, that may be related to inguinal hernia at the fifth decade of life. Recent studies have demonstrated an association among a punctual mutation on exon 20 of the elastin gene, amorfous component of the elastic fibers, and male individuals with inguinal hernia. The fibrillin-1 is the main microfibrillar component of the elastic fibers and is associated to genetic syndromes as Marfan, Ehlers-Danlos and Williams, that also present inidividuals with hernias. Thus, the objective of this study was to investigate the presence of polymorphisms on the fibrillin-1 gene (FBN1) on individuals who developed inguinal hernia. The desoxirribonucleic acid (DNA) of 60 individuals with inguinal hernia and 60 controls have been studied. The exons 4, 13, 24, 25, 26, 27, 31, 32, 39, 41, 59 and 65 were amplyfied by the Polymerase Chain Reaction and later evaluated the polymorphisms on polyacrilamide gel. The amplification product of these exons were evaluated by DNA sequencing and compared to the National Human Genome Research Institute database. Consistent mutations were observed at exon 27: 1) insertion of a base between codons 1119 and 1120 (GAT -> AGA); 2) insertion of a base between codons 1116 and 1117 (TGT -> CTG); 3) insertion of a base on codon 1148 (CCC -> CGC); and at exon 31: insertion of a base between codons 1282 and 1283 (GAG -> CGA). There was no statistic significance that could indicate the association between FBN1 gene and inguinal hernia. However, FBN1 is a large gene (350 kD, shared in 65 exons) and in other disorders as Marfan Syndrome, more than 500 mutations have already been described, without the existence of prevalent exons that have major responsability about the Syndrome, it is possible that other exons could be related to the happening of inguinal hernia.

Nanocellulose is a nascent and promising material with many exceptional properties and a broad spectrum of potential applications; hence, it has drawn increasing research interests in the past decade.  A new type of nanocellulose -- with mono- or bi-layer cellulose molecular sheet thickness -- was synthesized through a combined chemical-mechanical process (TEMPO-mediated oxidation followed by intensive sonication), and this new material was named molecularly thin nanocellulose (MT nanocellulose).  The overarching objective of this study was to understand the formation and supramolecular structure of MT nanocellulose and contribute to the knowledge of native cellulose structure. The research involved four major bodies of study: preparation of MT nanocellulose, characterization of MT nanocellulose, modeling wood pulp-derived cellulose microfibril cross section structure, and a comparative life cycle assessment (LCA) of different nanocellulose fabrication approaches.  The results revealed that MT nanocellulose with mono- to bi-layer sheet thickness (~0.4-0.8 nm), three to six chain width (~2-5 nm), and hundreds of nanometers to several microns length, can be prepared through TEMPO-mediated oxidation followed by 5-240 min intensive sonication.  The thickness, width, and length of MT nanocellulose all decreased with extended sonication time and leveled off after 1 or 2 h sonication.  Crystallinity, hydrogen bonding, and glycosidic torsion angles were evaluated by XRD, FTIR, Raman, and NMR.  These experiments revealed systematic changes to structure with sonication treatments.  A microfibril "cross section triangle scheme" was developed for the microfibril supramolecular modeling process and a 24-chain hexagonal/elliptical hybrid model was proposed as the most credible representation of the supramolecular arrangement for wood pulp-derived cellulose I" microfibril.  Comparative LCA of the fabrication of nanocellulose indicated that nanocellulose presented a significant environmental burden markup on its precursor, kraft pulp, and the environmental hotspot was attributed to the mechanical disintegration process.  Yet, overall nanocellulose still presented a prominent environmental advantage over other nanomaterials like single-walled carbon nanotubes, due to its relative low energy consumption. Overall, this research developed a facile approach to produce a new type of nanocellulose, the MT nanocellulose, provided new insights about the supramolecular structure of cellulose microfibrils, and evaluated the environmental aspects of the fabrication process of nanocellulose. / Ph. D.

O objetivo desse trabalho foi preparar compósitos de matriz de PCL reforçados com microfibrilas de PLA preparadas in situ a partir do controle da morfologia de blendas PLA/PCL. Embora a formação da morfologia fibrilar não tenha sido observada nas condições de extrusão empregadas, estudos do comportamento reológico de blendas de composição 50% PLA / 45% PCL / 5% de compatibilizante (% em massa) mostraram que microfibrilas de PLA podem ser obtidas entre 102 e 104 s-1. Assim, a técnica de reometria capilar foi utilizada para controlar a morfologia de blendas PLA/PCL. Compósitos de matriz de PCL reforçados com 5, 10, 20 e 30% (% em massa) de microfibrilas de PLA foram preparados em extrusora rosca simples, utilizando perfil de temperatura acima da temperatura de fusão do PCL, mas abaixo da temperatura de fusão do PLA, visando preservar a morfologia do PLA. O comportamento morfológico, térmico e mecânico dos compósitos foram avaliados por microscopia eletrônica de varredura (MEV), microscopia óptica com luz polarizada (POM), calorimetria exploratória diferencial (DSC), análise térmica dinâmico-mecânica (DMA) e ensaios mecânicos de tração e de impacto Izod. As curvas DSC mostraram um aumento no grau de cristalinidade da matriz de PCL com o aumento do teor de microfibrilas, o que provavelmente justifica os altos valores de módulo de Young determinados nos compósitos. A aplicação da Regra das Misturas comprovou que os compósitos fabricados exibiram boa orientação das microfibrilas na direção do esforço mecânico aplicado, com valores de módulos próximos ao limite superior da curva. No entanto, a adesão não uniforme entre a matriz e o reforço observada por MEV, resultou na queda da resistência à tração e resistência ao impacto dos compósitos, quando comparados ao PCL puro. A composição com 10% de microfibrilas apresentou um bom balanço de módulo de Young e resistência ao impacto, com potencial de viabilidade em uma série de aplicações biomédicas. / The aim of this work is to prepare PCL composites reinforced with PLA microfibrils prepared in situ from the morphology of PLA/PCL blends control. Although the formation of fibrillar morphology has not been observed under the extrusion conditions employed, studies of the rheological behavior of 50% PLA/ 45% PCL / 5% compatibilizer blends have shown that PLA microfibrils can be obtained between 102 and 104 s-1. Thus, the capillary rheometry technique was used to control the morphology of PLA /PCL blends. PCL composites reinforced with 5, 10, 20 and 30% (% by mass) PLA microfibrils were prepared in a single screw extruder using a temperature profile above the PCL melting temperature, but below the melt temperature of PLA, to preserve the PLA morphology. The morphology, thermal and mechanical behavior of the composites were evaluated by scanning electron microscopy (SEM), optical polarized light microscopy (POM), differential scanning calorimetry (DSC), dynamic mechanical-mechanical analysis (DMA) and mechanical tensile tests and Izod impact. DSC curves showed an increase in the degree of crystallinity of the PCL matrix with increasing the PLA microfibrils content, which probably justify the high Young\'s modulus values determined in the composites. The application of the Mix Rule proved that the composites showed good orientation of the PLA microfibrils in the direction of applied mechanical stress, presenting modules values near the upper limit of the curve. However, the non-uniform adhesion between the matrix and the reinforcement observed by MEV, caused the decrease of the tensile and impact strength when compared to pure PCL. The composition with 10% of PLA microfibrils exhibited a good balance of Young\'s modulus and impact strength, with potential viability in a number of biomedical applications.