The purpose of this study was to prepare concentrated and stable gold colloids for the enhancement of the signal response of the SPR technique for detecting small molecules such as progesterone. The gold colloids developed in this study were prepared by hydrazine hydrate, sodium borohydride, and tri-potassium citrate reduction routes. The study revealed that the sodium borohydride reduced gold colloids were extremely stable and it was able to be utilised in the progesterone immunoassay developed previously by Mitchell et al. The experiment was carried out on BIAcore 3000 using two different sensor surfaces (CM5 and SAM). The results showed that the enhancement species prepared from the borohydride-reduced gold colloids were able to improve the SPR signal response by 13 times higher than SPR signal produced without the enhancement species on the CM5 surface. The signal enhancement on the SAM surface using the same enhancement species was even greater at 29 times higher. The sensitivity of the assay was, however, unable to be determined due to time constraint. The limit of detection (LOD) of the progesterone assay using the CM5 chip was estimated to be ca. 5-20 pg/mL. Whilst for the SAM chip, the LOD of the progesterone assay was estimated to be ca. 5-20 fg/mL. Further work is required to confirm these estimated LOD values.

Pinus radiata D. Don is an economically important plantation species to New Zealand that is susceptible to the wood quality flaw 'intra-ring checking'. Intra-ring checking is a term used to describe radial fractures that can occur in the earlywood portion of a growth ring, altering the appearance and resilience of the wood, thereby decreasing its economic value. This thesis presents a study that was part of a broad, ongoing collaborative investigation directed at understanding wood quality issues, with the long term goal of enhancement of future radiata pine crops. These investigations are funded by the Wood Quality Initiative Ltd., and involve basic science, field trials and engineering studies related to intra-ring checking. Specifically, the present study was designed to establish the effects of the mineral nutrients boron, calcium and magnesium on wood formation, to determine whether they are associated with intra-ring checking. This research was carried out in three stages. Firstly, the ultra-structural and biochemical properties of wood with intra-ring checking were examined to determine if specific features of the cell wall were associated with the incidence of intra-ring checks. Electron microscopy techniques revealed that the CML/S1 region of the cell wall often showed a decrease in CML lignin staining and S1 striations in wood with intra-ring checks. However, Klason and acetyl bromide assays did not show a change in lignin content. In order to understand how changes in the CML/S1 region of the cell wall may occur, methods were required that would allow for the observation of wood formation in a controlled environment. In the second stage of this study, an organ culture technique was successfully developed to allow for the growth of radiata pine cambial tissue, sandwiched between phloem and xylem, on a defined nutrient medium. This nutrient medium was manipulated, using ion-binding resins, to control the amount of boron, calcium and magnesium available to the growing tissues, to determine if variations in wood formation could be induced. In the final stage of this research, an extensive comparative examination of different techniques that could be used for the observation and measurement of selected wood properties was undertaken, in order to determine the efficacy of the organ cultures to study wood formation in an altered nutrient environment. Wood properties were examined for various stages of xylogenesis, beginning with cell division and expansion, followed by cell wall deposition, and lastly with the onset of lignification in order to define the success of the culture technique. Electron microscopy investigations suggested that in the presence of very little boron the CML/S1 wall showed darker striation deposits, while an increase in calcium availability, resulted in a more defined CML/S1/S2 wall region compared to the controls. Further examination of the cell walls suggested that pectin esterification and possibly lignification could also be increased by limited boron availability. However, in many of the observed and measured parameters of wood properties, a great deal of complex 'between-tree' and 'within-culture' variation was observed. The results show that elucidation of the association between nutrient availability and the incidence of intra-ring checking can not be established from this organ culture study. In a concurrent study, the preliminary investigation of arabinogalactan-proteins (AGPs) in radiata pine was undertaken. Radiata pine AGPs were positioned in the compound middle lamella of xylem cells, suggesting potential roles in cell-cell adhesion or cell-cell signalling. For the first time, radiata pine AGPs were isolated and characterized in terms of their protein and carbohydrate composition, both of which yielded features typical of AGPs in other plant species. Unique to radiata pine AGPs was the presence of a large proportion of 5-linked arabinose. While the precise function(s) of AGPs are unknown, the results obtained in this research have established a basis for further investigation into the potential for their involvement in wood formation. Overall, new tools have been established to facilitate future research on radiata pine, a commercially important species, and novel results have been obtained concerning the mechanisms of wood formation therein.

Thesis (Ph.D.)--Ohio University, November, 2008. / Title from PDF t.p. Release of full electronic text on OhioLINK has been delayed until December 1, 2012. Includes bibliographical references (leaves 145-153)

Thesis (Ph.D.)--Ohio University, November, 2008. / Release of full electronic text on OhioLINK has been delayed until December 1, 2012. Includes bibliographical references (leaves 145-153)

Xyloglucan endotransglucosylase activity (XET), one of the two main activities of wall xyloglucan endotransglucosylase/hydrolase proteins (XTHs), is of interest because it is responsible for cutting and re-joining xyloglucan of the hemicellulose-cellulose microfibril network in the plant cell wall. XET activity causes transient matrix cleavage without hydrolysis, thus providing a molecular mechanism for controlled, turgor-driven wall expansion. XET activity can be involved in both wall-loosening, thus facilitating cell expansion, and wall-tightening, thus suppressing cell expansion depending on the molecular size, location and age of the participating xyloglucan chains. I have studied the existence of an ‘XET activating factor’ (XAF) in the cold-water-extractable polymers of cauliflower florets. Remaining water-soluble on boiling but losing activity upon proteinase K- and trypsin-digestions implied a heavily glycosylated glycoprotein. XAF was extracted from a wide range of plants and organs. XAF solubilised Arabidopsis cell-wall XTHs, increasing their XET activity on soluble xyloglucan up to 120-fold, tested by a novel method developed in my project. XAF had effects similar to those of 15 mM Ca2+ and 100 mM Na+ in this respect, although it was only weakly ionic. Interestingly, XAF had the unique ability to solubilise XET activity but no other tested wall enzymes from Arabidopsis cell walls, suggesting a specific interaction of XAF to XTH proteins. XAF was successfully purified by the use of several methods, developed in this project. These included cation-exchange column chromatography followed by anion-exchange column chromatography, resulting in two main XAF-activity fractions; or a native- PAGE electro-elution, resulting in three main fractions. Purified XAF contained a major amount of glucose, arabinose, galactose and uronic acid residues. Both boiled cauliflower preparation (BCP) and partially purified XAF were positive with AGP antibodies but the purification of AGP from BCP by the use of Yariv reagent did not enrich XAF activity. Mass-spectrometry analyses of the purified XAF fractions showed some candidates for XAF, including fasciclin-like arabinogalactan-protein 7 (FLA7), stress-responsive protein (LTI65, LTI140) and early nodulin-like protein 14 (ENODL14). Homozygous Arabidopsis mutants (confirmed by genotyping) defective in these genes were used to determine XAF as well as its biological role on plant cell growth. Although there was no phenotype observed, several organs of the mutant plants had significant increases or decreases in XAF activity compared to that of wild type plants. This is the first work that suggests a role of fla7, enodl14 and lti65 in the solubilisation, and thus activation, of Arabidopsis XET.

No description available.

No description available.

La gomme d’Acacia est l’une des plus anciennes gommes naturelles dans le monde et la plus connue. Elle est définie comme l’exsudat gommeux produit par les arbres d’Acacia senegal et Acacia seyal. Les gommes d’Acacia sont composées d’arabinogalactanes protéines (AGPs), faiblement chargés, hyperbranchés avec une forte proportion de sucres (90%) et d’environ 1-3% de protéines et de minéraux. Malgré ses nombreuses applications industrielles, les connaissances sur ses propriétés volumétriques (hydrostatiques et hydrodynamiques) restent à améliorer. Ces propriétés peuvent être liées à la flexibilité et l’hydratation des molécules qui déterminent les propriétés fonctionnelles importantes comme les propriétés interfaciales. L'objectif de cette thèse est l’étude des propriétés volumétriques d’AGPs de la gomme d’Acacia. L’étude a été faite sur les principales variétés des gommes d’Acacia, A. senegal et A. seyal, ainsi que des fractions macromoléculaires d’A. senegal, obtenues par la chromatographie d'interaction hydrophobe et d'échange ionique. Les principaux résultats ont montré que les AGPs de gomme d’Acacia ont une structure semi flexible. De plus, des différences dans la flexibilité et l’hydratation entre les fractions d’AGPs ont été montré. Ces différences ont été expliquées par leurs différences en composition, polarité, masse molaire, forme et conformation. De plus, un comportement intermédiaire entre des protéines et des polysaccharides linéaires ont été montré. Finalement, un effet des agrégats d’AGPs sur les propriétés volumétriques a été mis en avance. / Acacia gum is the oldest and most widely known and used gum, it is a dried gummy exudate from the leaves and branches of the Acacia senegal and Acacia seyal trees. Acacia gums are weakly charged, amphiphilic hyperbranched arabinogalactan-proteins (AGPs). They are composed of about 90% polysaccharides and from 1-3% of proteins and minerals. In spite of the widely spread of industrial usage of A. gums, their volumetric properties (hydrostatic and hydrodynamic) have not been well studied. These properties have been linked to important properties such as flexibility and hydration of the molecule, which are related to important functional properties of A. gums (e. g. interfacial properties). The main objective of this PhD thesis was to study the volumetric properties of AGPs from Acacia gums exudates. For this effect, the main commercial species, A. senegal and A. seyal, and the macromolecular fractions of the former, obtained via hydrophobic interaction and ionic exchange chromatographies were studied. The main results showed that AGPs from Acacia gums have a semi-flexible structure. However, differences in their flexibility and hydration were seen among AGP fractions. These differences were explained based on their composition, polarity, molar mass, shape and conformation. Furthermore, an intermediate behavior between proteins and linear polysaccharides was evidenced. In addition, an effect of the presence of AGP based aggregates on the volumetric properties was seen.

Although dynamic interactions between plant cells and their environment require adhesion between the cell wall (CW) and the plasma membrane (PM), few plant adhesion molecules have been identified. Therefore, the seed coat mucilage secretory cells (MSCs) of Arabidopsis thaliana (which undergo developmentally regulated changes in adhesion) were developed into a novel model system to study PM-CW adhesion. Twenty-seven candidate genes were identified using data from publicly available and seed-specific microarrays. Mutant plants for these genes were screened for defects in adhesion via plasmolysis, and for changes in MSC morphology that may result from defective adhesion (Chapter 1). Two fasciclin-like arabinogalactan proteins were isolated in this screen. One of these, SOS5, was characterized in detail (Chapter 2). sos5 mutants are sensitive to hyperosmotic conditions and show defects in PM-CW adhesion and MSC mucilage structure. Interestingly, these phenotypes may be attributed to defects in adhesion or to defects in cell wall deposition.

Thesis (Ph. D.)--Ohio University, March, 2004. / Includes bibliographical references (leaves 158-181).