Oxidative stress is considered a major factor in the etiology of age related diseases and the aging process itself. Organisms have developed mechanisms to protect against oxidative damage resulting from increased production of reactive oxygen species during aging. One of the major antioxidant systems is the methionine sulfoxide reductase (Msr) enzyme family. The two major Msr enzymes, MsrA and MsrB, can stereospecifically reduce the S and R epimers, respectively, of methionine sulfoxide in proteins back to methionine. This study, using Drosophila melanogaster, decribes the first animal system lacking both MsrA and MsrB. The loss of either MsrA or MsrB had no effect on lifespan in Drosophila, but loss of MsrB results in a slight decrease in locomotor activity from middle age onward. Double mutants lacking both forms of Msr have a significantly decreased lifespan and decreased locomotor activity at all ages examined. The double Msr mutants had no detectable increase in protein oxidation or decrease in mitochondrial function and were not more sensitive to oxidative stress. These results suggested that other cellular antioxidant systems were protecting the flies against oxidative damage and the decreased life span observed in the double knockouts was not due to widespread oxidative damage. However, one cannot exclude limited oxidative damage to a specific locus or cell type. In this regard, it was observed that older animals, lacking both MsrA and MsrB, have significantly reduced levels of dopamine, suggesting there might be oxidative damage to the dopaminergic neurons. Preliminary results also suggest that the ratio of F to G actin is skewed towards G actin in all mutants. The present results could have relevance to the loss of dopaminergic neurons in Parkinson’s disease. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2015 / FAU Electronic Theses and Dissertations Collection

Aging is a multifactoral biological process of progressive and deleterious changes partially attributed to a build up of oxidatively damaged biomolecules resulting from attacks by free radicals. Methionine sulfoxide reductases (Msrs) are enzymes that repair oxidized methionine (Met) residues found in proteins. Oxidized Met produces two enantiomers, Met-S-(o) and Met-R-(o), reduced by MsrA and MsrB respectively. Unlike other model organisms, our MsrA null fly mutant did not display increased sensitivity to oxidative stress or shortened lifespan, suggesting that in Drosophila, having either a functional copy of either Msr is sufficient. Here, two Msr mutant types were phenotypically assayed against isogenic controls. Results suggest that only the loss of both MsrA and MsrB produces increased sensitivity to oxidative stress and shortened lifespan, while locomotor defects became more severe with the full Msr knockout fly. / by Kelli Robbins. / Thesis (M.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

La modification thermo-chimique est un procédé qui consiste à modifier la matière à cœur, avec pour objectif d’améliorer les propriétés du bois, en particulier la résistance fongique. Pour ce faire, conférer au bois un équilibre hygroscopique inférieur à la limite basse de développement des champignons est une approche qui permet en sus de limiter les variations dimensionnelles dues à l’humidité de l’air. Limiter les variations dimensionnelles augmente logiquement la durabilité des assemblages et des revêtements de surface, ce qui améliore encore les performances du matériau. Les constituants du bois possèdent des groupements hydroxyles qui rendent le matériau hydrophile. Les modifications thermochimiques envisagées dans ces travaux de recherche consistent principalement à limiter l’accès à ces groupements et/ou à réduire leur nombre, par imprégnation de monomères/oligomères bio-sourcés (oligomères d’acide lactique (OLA) ou de poly(butylène succinate) (OBS)) suivie de leur polymérisation in situ par traitement thermique. Le comportement hygroscopique du matériau, la persistance des oligomères dans le bois et la résistance biologique du bois traité sont les critères de sélection des traitements. Les traitements retenus conduisent à des matériaux ayant une meilleure stabilité dimensionnelle et une meilleure résistance biologique. Les potentielles applications de ces matériaux ont été évaluées après caractérisation des propriétés mécaniques, de l’adhésion des revêtements de surface et de la capacité de collage du bois traité / Wood thermo-chemical modification process consists of permanent enhancement of wood properties in the core of the material. By decreasing wood equilibrium moisture content below the limit of fungi development, one could in addition reduce the dimensional variations due to humidity. A better dimensional stability of wood would be beneficial to durability of assemblies and surface coatings, further improving the performance of the material. Hydroxyl groups from wood polymers are responsible for the material hydrophilicity. The thermochemical modifications considered in this work mainly consist in limiting the access to these groups and / or reducing their number, by impregnation of bio-based monomers / oligomers (oligomers of lactic acid (OLA) or oligomers of butylene succinate (OBS)) followed by their in situ polymerisation by heat treatment. The hygroscopic behaviour of the material, the persistence of oligomers in the wood and the biological resistance of the treated wood are the criteria for the selection of treatments. The selected treatments lead to materials with enhanced dimensional stability and biological resistance. The potential applications of these materials have been evaluated after characterisation of mechanical properties, adhesion of the surface coatings and bonding capacity of the treated wood

Made available in DSpace on 2017-07-21T18:53:01Z (GMT). No. of bitstreams: 1 Ana Paula Travalini.pdf: 3027594 bytes, checksum: bce498a3a112f4874728442be07d1f8d (MD5) Previous issue date: 2015-02-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Cassava (Manihot esculenta Crantz) is a crop with high production yields in Brazil, and with processing, it generates large amounts of a high-moist solid byproduct that is of difficult destination. This byproduct known as bagasse or massa by the cassava starch producers shows high levels of starch and fiber. Thus, the aim of this study was to extract, characterize and modify the fiber cassava bagasse (FBM) for applying in composites, besides getting nanocrystalline cellulose. In order to remove residual starch form the pulp an enzymatic hydrolysis was carried out, leaving only the cassava fiber, i.e., cellulose, hemicellulose and lignin. Selected analyses were performed to confirm complete removal of starch such as high performance liquid chromatography (HPLC), thermogravimetry (TG), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and color analysis. To incorporate the fiber in a polymeric matrix, we carried out a chemical modification by acetylation of the fibers, making them more hydrophobic, facilitating achievement of composites. After modification, mid-infrared spectroscopic analysis (FTIR) was performed to verify the substitution of hydroxyl groups. The composite (5, 10 and 20 % fiber) were obtained in a twin screw extruder, followed by injection. The test pieces were submitted to tensile test and flexure, SEM, DSC and color analysis, and they presented homogeneous mixture. The nanocrystalline cellulose (NCC) was developed from three bleaching stages of fiber for higher removal of lignin, followed by acid hydrolysis, dialysis and centrifugation, and subsequent analyses were performed in zeta potential to verify size reduction of cellulose particles, and morphological analysis (SEM). The NCC obtained from FBM was compared with NCC obtained from microcrystalline cellulose (MCC). The CNCs remained suspension stable and low particle sizes, while the CNC-FBMB resulted in a high degree of crystallinity. / A mandioca (Manihot esculenta Crantz) consiste em uma planta com altos índices de produção no Brasil, sendo que com o processamento, gera-se uma grande quantidade de um subproduto fibroso úmido que tem problemas quanto a destinação. Este subproduto, conhecido na agroindústria como bagaço ou massa, apresenta altos teores de amido e fibra. Sendo assim, o objetivo deste estudo foi extrair, caracterizar e modificar quimicamente a fibra do bagaço de mandioca (FBM), aplicá-la na obtenção de compósitos, além de utilizá-la para obter celulose nanocristalina. Com o intuito de remover o amido residual do bagaço, foi realizada uma hidrólise enzimática, restando apenas a fibra de mandioca composta por celulose, hemicelulose e lignina. Diversas análises foram realizadas a fim de comprovar a completa remoção do amido, como cromatografia líquida de alta eficiência (CLAE), termogravimetria (TG), calorimetria exploratória diferencial (DSC), microscopia eletrônica de varredura (MEV) e análise de cor. Para incorporar as fibras em uma matriz polimérica, optou-se por realizar uma modificação química por acetilação das fibras, tornando-as mais hidrofóbicas, facilitando a obtenção de compósitos. Após a modificação realizou-se análise em espectroscopia na região do infravermelho médio (FTIR) para verificar a substituição dos grupos hidroxila. Os compósitos (5, 10 e 20 % de fibra) foram obtidos em extrusora dupla rosca, seguida por injeção. Os corpos de prova foram submetidos a ensaios mecânicos de tração e flexão, MEV, DSC e análise de cor, sendo que os mesmos apresentaram uma mistura homogênea. A celulose nanocristalina (CNC) foi desenvolvida a partir de três etapas de branqueamento da fibra para maior remoção da lignina, seguido por hidrólise ácida, centrifugação e diálise, sendo posteriormente realizadas análises em potencial zeta para verificar a redução do tamanho das partículas de celulose, além de análises morfológicas (MEV). A CNC obtida a partir da FBM foi comparada a CNC obtida a partir da celulose microcristalina (CMC). As CNCs apresentaram estabilidade de suspensão e baixos tamanhos de partículas, enquanto que a CNC-FBMB resultou em alto grau de cristalinidade.

The present work is synthesizing novel protein-based superabsorbent hydrogels from albumin protein (AP) and isolated zygomycetes protein (IZP) via modification with an acylating reagent and a bifunctional crosslinker, also investigation on their swelling behaviors under some conditions. The hydrophilic acylating reagent was introduced into albumin and zygomycetes proteins and hydrophylicity of albumin and isolated zygomycetes protein were increased by ethylenediaminetetraacetic dianhydride (EDTAD). Provided protein hydrogels through this method include modification of lysyl residues in the unfolded proteins via adding of one or more hydrophilic carboxyl groups. The reaction was developed with a dialdehyde crosslinking reagent (glutaraldehyde) in order to stabilize the modified protein configuration. The maximum capacity of EDTAD-AP hydrogel swelling was observed 296 g water per g of dry gel, and for EDTAD-IZP hydrogel was 87 g water per g of dry gel.In this study, effect of selected physical and chemical parameters such as protein structure, extent of modification, protein concentration, various pH, ionic strength, gel particle size, temperature as important factors affecting the water uptake behavior of superabsorbent hydrogel were investigated. In addition, the effect of some organic solvents particularly absolute ethanol for increasing the swelling properties was studied. / Uppsatsnivå: D

Les pressions environnementales apparues en France et en Europe au cours des dernières décennies ont considérablement changé les méthodes de protection du bois. Dans ce contexte, le règlement relatif aux produits biocides et la directive relative aux produits biocides conduisent au développement de méthodes de préservation plus soucieuses de l'environnement et à l’intérêt croissant pour des alternatives non biocides comme le traitement thermique ou la modification chimique. Le traitement thermique à des températures de 180 à 220°C conduit à la modification chimique de la structure des différents constituants pariétaux du bois en lui conférant de nouvelles propriétés comme une meilleure résistance aux champignons basidiomycètes et une grande stabilité dimensionnelle. Malgré ces améliorations, la durabilité conférée au bois traité thermiquement demeure insuffisante pour des applications en classes 3 ou 4 dans lesquelles le bois est en contact avec le sol ou est en présence de termites. Par ailleurs, le bore sous forme d’acide borique ou de borax présente des propriétés fongicides et termiticides. Cependant, les produits à base de bore présentent l'inconvénient d'être très facilement lessivables les rendant inutilisables pour des applications en conditions extérieures. Les modifications chimiques réalisées suite à l'imprégnation de solutions à 10% d'anhydride maléique de polyglycérol ou de méthacrylates de polyglycérol ou de résine phénol formaldéhyde avec ou sans borax avant le traitement thermique ont apporté une amélioration des propriétés des bois modifiés thermiquement et surtout une résistance aux termites avec ou sans lessivage / Environmental pressures appeared in France and in Europe in the last decades have substantially changed the methods for wood protection. In this context the Biocidal Products Regulations and the Biocidal Products Directive lead to the development of more environmentally friendly preservation methods and the growing interest in non-biocidal alternatives such as thermal treatment or chemical modification. Wood heat treatment at temperatures of 180 to 220 °C leads to the chemical modification of wood cell wall polymers conferring new properties to the material like its increased decay resistance and high dimensional stability. Despite these improvements, the durability of wood heat treatment is not sufficient to envisage use class 3 and 4 applications; where the wood is in contact with soil or termites. Moreover, Boron compounds present fungicidal and termiticidal properties. However, boron compounds have the drawback of being very easily leached out from wood making it unusable for applications in outdoor conditions. Wood chemical modification carried by the impregnation of aqueous solutions (10 %) of maleic anhydride polyglycerol adduct or polyglycerol methacrylates or phenol-formaldehyde resin, with or without borax followed by heat treatment at 220°C has shown some improvement of thermally modified wood properties particularly its resistance to termites in case of leach or not

Abstracts Cellulose nanopapers are the strongest polymeric material known to us, and in the near future, they are likely to be a backbone of numerous functional materials. Cellulose nanopapers have gained much attention due to qualities such as their environmentally friendly nature, renewable raw material source and biodegradability. Additionally, they offer an industrially adaptable, water-based processing route, which is similar to current paper production. Functionally, besides being tougher than any known plastic, cellulose nanopapers remain foldable like a paper. Despite their fascinating properties, cellulose nanopapers are still far from commercialisation – mainly due to two obstacles. Firstly, it can take up to hours to prepare a nanopaper due to poor draining of cellulosic nanofibres. Secondly, cellulose nanopapers have extremely poor water and humidity resistance, as up to 90% of their stiffness is lost in the presence of water. The purpose of this dissertation is to address both obstacles and suggest an eco-friendly yet industrially relevant solution. Two approaches are employed: increasing the hydrophobicity of cellulose nanofibres with lactic acid and ultrasonication (Paper I and II), and combining cellulose nanofibres with hydrophobic materials, such as polyurethane (Paper III) and lignin-rich entities (Paper IV). By using these methods, the preparation time was improved by 75% (Paper II) and by 70% (Paper IV) respectively. All reported nanopapers were significantly more tolerant of water and moisture than the reference nanopaper. The mechanical properties were also improved in Paper I and IV. Additionally, all reported nanopapers were thermally stable. This thesis also discusses the importance of quick draining in cellulose nanofibre-reinforced paper products. The results of this study are likely to aid the commercialisation of cellulose nanopapers in practical applications and the use of cellulose nanofibres in other materials, such as reinforcing paperboards. All methods used in this thesis are water-based. / Tiivistelmä Selluloosapohjaiset nanopaperit ovat lujimpia tunnettuja polymeerimateriaaleja ja lähitulevaisuudessa niiden voidaan odottaa luovan perustan useille funktionaalisille materiaaleille. Nanopaperit ovat saaneet paljon huomiota ympäristöystävällisyytensä, uusiutuvan raaka-aineensa ja biohajoavuutensa ansiosta. Lisäksi niiden valmistusprosessi on vesipohjainen ja samankaltainen kuin tavallisen paperin valmistukseen käytetty teollinen prosessi. Käyttöominaisuuksiltaan ne ovat erinomaisia, sillä vaikka niiden sitkeys on parempi kuin tunnetuilla muoveilla, ovat ne silti paperin tavoin taiteltavia. Kiehtovista ominaisuuksistaan huolimatta selluloosapohjaiset nanopaperit ovat kuitenkin vielä kaukana kaupallistamisesta ja tähän vaikuttavat pääosin kaksi tekijää. Tärkein syy on selluloosananokuitujen kuivattamisen ja näin ollen nanopaperin muodostamisen vaatima huomattavan pitkä aika. Nykyisillä menetelmillä nanopaperin valmistaminen kestää useita tunteja. Toinen syy on niiden erittäin huono veden- ja kosteudenkestävyys. Ne menettävät jopa 90 % jäykkyydestään veden vaikutuksesta, mikä rajoittaa niiden käyttöä kosteissa ja vesiroiskeille alttiissa kohteissa. Tämän väitöskirjatutkimuksen päätavoitteena on löytää ekologisesti kestävä ja teollisuudessa hyödynnettävissä oleva menetelmä molempien edellä mainittujen ongelmien ratkaisemiseksi. Työssä noudatetaan kahta eri lähestymistapaa: lisätään selluloosananokuitujen hydrofobisuutta maitohapon ja ultrasonikoinnin avulla (Artikkelit I ja II), ja yhdistetään selluloosananokuituihin hydrofobisia materiaaleja, kuten polyuretaania (PU) (Artikkeli III) ja ligniinipitoisia yhdisteitä (Artikkeli IV). Näitä menetelmiä käyttämällä valmistusaikaa saatiin lyhennettyä 75 % (Artikkeli II) ja 70 % (Artikkeli IV). Kaikki valmistetut nanopaperit olivat huomattavasti veden- ja kosteudenkestävämpiä kuin verrokkinäytteet sekä osoittivat lämpöstabiiliutta. Lisäksi mekaanisia ominaisuuksia saatiin parannettua Artikkeleissa I ja IV. Tässä työssä käsitellään myös nopean kuivattamisen tärkeyttä selluloosananokuitulujitteisten paperituotteiden valmistuksessa. Saadut tulokset todennäköisesti edistävät selluloosapohjaisten nanopaperien kaupallistamista ja selluloosananokuitujen hyödyntämistä esimerkiksi kartongin lujitemateriaalina. Kaikki työssä käytetyt menetelmät ovat vesipohjaisia.

This work introduces a database of experimentally verified structures of nucleic acids which were collected from published scientific literature. The database is annotated and the structures are analysed from the perspective of quality and it was found that the experimentally obtained data are not always sufficient - their supporting evidence is often limited and their quality is not convincing. This work also discusses some of the problems, that can be encountered when the structures are experimentally probed. Contents of the database were compared to the RFAM database and despite of its small range it contains 80 new structures. The complete database of 166 structures can be possibly used to optimise software used to predict derived structures of nucleic acids. Furthermore, the work presents several possible ways of improvement of the quality of contained structures.

No description available.

Polysaccharides are now popularly used in paper technology since they are able to improve mechanical properties of the paper. Xylan and pectin are two natural polymers that have a wide range of applications nowadays. These two polysaccharides can be used in their native forms as well as derivatives. In this study, xylan and pectin were modified to obtain cationic derivatives before adding into the paper for enhancement. The work was motivated by the fact that xylan and pectin share the same negative surface properties as cellulose. This leads to a slight repulsion effect between them once they are close. Their cationic derivatives, therefore, are believed to strengthen the paper due to electrostatic interactions between two oppositely charged objects beside hydrogen bonds. To fulfil the purposes, oat spelt xylan and apple pectin were chemically modified using different modification methods, including oxidation, amidation, and a combination of these two methods. A quantitative method to determine the adsorbed amount and relative retention capacity of xylan onto paper using high performance liquid chromatography was also developed. The results show that oat spelt and apple pectin, as well as their modified derivatives, can improve the paper mechanical properties. The oat spelt xylan significantly enhances the tensile strength, however, this contribution has a saturation level in correlation with the relative retention capacity of the xylan onto cellulose. The best retention capacity is achieved when 5% of xylan is added. This finding provides a practical approach to the application of xylan as a paper additive in consideration of economic issues. Although the application of apple pectin and its amidated derivatives in paper is rather rare, some interesting points have been discovered in this work. Among the apple pectin samples used, only the ones with low degree of esterification give a slight enhancement in tensile index at 5% dosage. The results also suggest that the dosage of the pectin added into the paper should not exceed 5% due to its viscous property at high concentrations.