Earths most abundant biomolecules, carbohydrates, offer tremendous potential forelectricity production. Carbohydrate fuel cells are electrical fuel cells that can harvest the stored electrons in carbohydrates and offer a cheap and efficient method that could help solve growing energy demands, while providing a renewable green energy source. Viologen-mediated carbohydrate fuel cells have demonstrated the ability to accelerate carbohydrate oxidation while decreasing partial or incomplete oxidation products reducing the electricity production. Subsequent studies suggested polymeric viologen compounds could improve the efficiency by increasing the local concentration of viologen. This thesis presents the utility of surface-immobilized viologen mediators for the oxidation of simple carbohydrates. Methyl viologen formed a self-assembled monolayer on a gold electrode surface to enhance its electrocatalytic oxidation of dihydroxyacetone, fructose, and glucose. The thiolated viologen formed surface adsorbed films on the gold electrodes that where consistent with monolayers and were characterized by quartz crystal microbalance and cyclic voltammetry. Cyclic voltammetry indicated that carbohydrates can generate electricity when combined with methyl viologen. Monolayer formation of methyl viologen indicates that immobilized mediators can be used to enhance oxidation of simple carbohydrates to generate electricity. This same tethered mediator strategy could be used for other mediators to increase their electrochemical efficiency in carbohydrate fuel cells.

‘Crimson Seedless’ (Vitis vinifera L.) is an attractive, late season, red, seedless cultivar, which is currently a very popular table grape cultivar. It is one of the most planted cultivars in South Africa and third in terms of total area of table grape vineyards in production. Mature ‘Crimson Seedless’ grapes are characterized by outstanding eating quality, good flavour, firm and crisp berries. One of the key factors affecting the yield of table grape cultivars is bud fruitfulness. Low fruitfulness can have a significant effect on the yield of table grape cultivars and ‘Crimson Seedless’ is characterized by a fruitfulness problem. Summer pruning, such as the removal of shoots after harvesting grapes, is a cultivation practice widely used by some table grape producers in the Orange River region of South Africa. The first hypothesis of this study stated that the removal of shoots after harvest will increase the transmitted PAR through the canopy, increase carbohydrate reserve levels in canes and improve bud fruitfulness of ‘Crimson Seedless’. A second hypothesis of this study stated that the cut back of all main shoots and shoots developing from spurs to the nearest lateral shoot and the removal of all unproductive shoots after berry set will result in fruitful shoots the following season. The third and final hypothesis of this study stated that the removal of shoots after harvest and berry set will improve the yield and quality of Vitis vinifera cv. ‘Crimson Seedless’. The study was conducted over three seasons (2010/11 to 2012/13) and aimed at investigating factors, including shoot removal, impacting bud fruitfulness of an 11-year-old commercial V. vinifera L. cv. ‘Crimson Seedless’ vineyard, grafted on ‘Ramsey’ (Vitis champinii) rootstocks in the Hex River Valley. The treatment design was a complete randomized design and involved five treatments, which included 33% shoot removal (S33) and 66% shoot removal (S66) after harvest, cutting of all main and lateral shoots developing from spurs to the nearest lateral shoot (LS), removal of all unproductive shoots (RSB) which was compared with the control, in which standard pruning practices were performed. The results obtained in this experiment showed that shoot removal after harvest and after berry set improves PAR transmission into the canopy, but there was no significant impact on bud fruitfulness. In addition, it was found that shoot removal reduced vegetative growth resulting in thinner canes that also led to the improvement in PAR transmission. Furthermore, bunch number per shoot in the LS treated vines was reduced when compared with S33 treated vines, illustrating that shoot removal at berry set can reduce bunch number per shoot due to defoliation after berry set. The significant decrease in bud burst in the S33 treatments compared with the control was expected due to less shoots, resulting in a reduction in cane mass during the 2010/11 season. The significant effect of LS treatments after berry set on TSS and total red pigments compared with the S66 treatments and the control, respectively, clearly indicates that shoot removal after berry set improves grape colour. The positive effect of LS treatments on colour was supported by the significant improvement in class 4 bunches, representing an improvement in quality. Although shoot removal did not have a significant effect on the bunch mass per vine of ‘Crimson Seedless’, there was a significant reduction in total bunches for export and mass of the total export bunches in the LS treatments in the 2011/12 season. A link between carbohydrate concentration in canes and bud fruitfulness was not found in this study, as S33 and S66 treatments did not have a significant effect on carbohydrate content in canes during the 2011/12 season. The question therefore arises whether the treatments applied during the growing seasons are worthwhile, because there was no significant impact on bud fruitfulness of Vitis vinifera L. cv. ‘Crimson Seedless’. This study illustrates that growers need to decide whether it is worthwhile to utilize labour for this practice and they must manage grapevines not only for the current seasons crop, but also for the next season and this can be accomplished by maintaining sufficient carbohydrates for fruitfulness and yield from season to season. / Dissertation (MInst Agrar)--University of Pretoria, 2014. / tm2015 / Plant Production and Soil Science / MInst Agrar / Unrestricted

The aim of the project was to synthesize α1,2-linked and α1,6-linked dimannosides linked through either an oxygen-atom or a sulphur-atom, and subsequently test the binding properties of the dimannosides to lectins with known specificity towards mannose-containing glycans. Thedimannosides were prepared by a glycosylation reaction using selectively protected monosaccharides containing a thiol or alcohol nucleophilic glycosyl acceptor and a series of different glycosyl donors. The synthetic routes to the different building blocks were designed to efficiently make use of common intermediate compounds to streamline the synthesis. The glycosyl acceptors used forthe synthesis of α1,2-linked as well as α1,6-linked dimannosides were synthesized in few steps and diversified only in the last steps of the synthesis. The glycosyl donors used in the study were synthesized from commercially available starting material in a straightforward and convenientsynthesis in 7 to 8 steps.

Bacteria are coated with repeating units of oligosaccharides that exhibit remarkable diversity. Often, glycan units of three or even two sugars are sufficient to identify a species of bacteria. Such specificity makes bacterial surface glycans attractive vaccine targets. However, efforts to create effective vaccines against carbohydrates have been hampered by poor vaccine design as well as the human immune tendency to respond to glycan antigens with non-specific, T-cell independent mechanisms. As a result, carbohydrate vaccines have historically produced only adequate memory responses in healthy individuals and poor responses in the elderly or immunocompromised. To circumvent these issues, a novel conjugate vaccine was developed that utilizes theQβ virus-like particle carrier that displays both a carbohydrate antigen as well as a Natural Killer T cell adjuvant. This unique vaccine has been reported to stimulate the production of high affinity (nanomolar) antibodies against carbohydrate antigens. To further conjugate vaccine research, the present work synthesizes two bacterial surface antigens: a trisaccharide from Streptococcus pneumoniae serotype 23F (Sp23F), and a pentasaccharide from Ruminococcus gnavus (Rg). Sp23F has been characterized as one of the more virulent and disease-causing strains of S. pneumoniae. Rg secretes highly immunostimulatory proteins and is associated with irritable bowel syndrome. The Sp23F antigen is synthesized with an alkyne at the reducing end of the sugar to facilitate coupling to Qβ. A selection reagent for Sp23F is also synthesized to enable the extraction of antibodies and B cells that bind the antigen. In conjunction with providing a conjugate vaccine antigen, the Rg pentasaccharide will be examined as a TLR4 ligand and was therefore synthesized without an alkyne. The Rg conjugate vaccine shows promise in treating irritable bowel syndrome as well as facilitating research into the role Rg plays in the human microbiome.

The use of 4-acetoxy-2,2-dimethylbutanoyl protecting group for the C2-hydroxyl allows the selective formation of β-glycosides without producing α-glycosides. This very bulky protecting group can be removed under mild conditions.

Polymeric carbohydrates have been reported to modulate inflammatory responses in vitro and in vivo. Previous reports suggest that certain carbohydrate polymers, such as (1→3)-β-D-glucans, may possess free radical scavenging activity. If glucans are free radical scavengers then it might explain, in part, the ability of these ligands to modulate inflammatory responses. The present study examined the free radical scavenging activity of a variety of carbohydrate polymers and the effect of the polymers on free radical levels in a murine macrophage cell line. All of the carbohydrates exhibited concentration dependent antioxidant effects (EC50 range = 807 to 43 μg/ml). However, the antioxidant activity for the carbohydrates was modest in comparison with PDTC (EC50 = 0.13 μg/ml) and the carbohydrate concentration required for antioxidant activity was high (×̄ EC50 = 283 μg/ml). The antioxidant ability of the polymers was greater (p < .05) than their monosaccharide constituents, i.e., dextrose EC50 = 807 vs. glucan sulfate EC50 = 43 μg/ml. Coincubation of glucans with murine J774a.1 cells increased free radical levels when compared to controls. Therefore, the weak free radical scavenging activity of glucan polymers cannot explain their modulatory effect on inflammatory responses in tissue culture and/or disease models of inflammation.

Part I of this thesis deals with general methodology and the experimental work can be clearly divided into two sections. Part II deals with studies carried out chiefly to determine further the epidemiological factors influencing serum lipid (and in particular, serum triglyceride) levels in the population groups of Southern Africa. The original objectives are described on page 70 and the main conclusions summarised on page 114. Part III describes three studies which were conducted in an attempt to fill some of the gaps in the considerable literature on the relationship between dietary carbohydrate and serum lipids in man. Both in the review of the literature at the beginning of this section and in the interpretation of the results of each of the studies, discussion has been chiefly limited to experiments conducted in man. There is a great deal of information available on studies carried out in experimental animals which show marked species differences from man with regards kinetic behaviour of serum and liver triglycerides(l). Where relevant, of course, reference has been made to these studies. The significance of each of the three studies has been discussed separately, but the principal objectives are mentioned on page 138 and the general conclusions are summarised on page 205.

Während bei Prokaryonten, Pflanzen und Pilzen der Transport von Zuckern über Membranen mit Hilfe von Disaccharid-Transportern erfolgt, ist bei Tieren, vor allem Säugern, nach der allgemein anerkannten Vorstellung nur der Transport von Monosacchariden bekannt. Die vorliegende Dissertation, in der ScrT, ein bislang unerforschtes Protein aus der Fruchtfliege Drosophila melanogaster untersucht und charakterisiert wurde, beinhaltet Daten, die diese Vorstellung in Frage stellen.Die Expression von ScrT in Hefestämmen ermöglichte das Wachstum auf einem Minimalmedium, das als einzige C-Quelle Saccharose enthält, und Tests mit radioaktiv (14C) markierter Saccharose belegten, dass Hefestämme, die das untersuchte Protein heterolog exprimieren, Transportaktivität für dieses Disaccharid aufweisen.Die mittels Immunhistochemie ermittelte in vivo-Lokalisation von ScrT führte zu unterschiedlichen Resultaten. Zum einen waren in den adulten Fruchtfliegen deutliche Signale im Mitteldarm zu erkennen. Zum anderen wurden vesikuläre Strukturen in Follikelzellen der Ovarien gefärbt. Diese offenbar Melanin enthaltenden Strukturen fanden sich auch im Chorion der abgelegten Embryonen. Somit scheint es sich bei diesen Vesikeln um Melanosomen oder funktionell analoge Organellen zu handeln, in deren Membran das untersuchte Protein lokalisiert ist und die sekretorisch bei der Bildung des Chorions an dieses abgegeben werden. Die Lokalisierung von ScrT in den Follikelzellen wurde mittels in situ-Hybridisierung bestätigt.Den vorliegenden Daten zufolge dürfte ScrT unter anderem den Eintritt von Saccharose in Melanosomen regulieren, wo das chemisch relativ inerte Disaccharid als kompatibler Osmolyt fungieren und das osmotische Gleichgewicht während der Polymerisation von Melanin ausbalancieren könnte. Im Einklang mit dieser Hypothese steht auch, dass Mutationen in MATP, dem menschlichen Ortholog von ScrT, zu einer bislang wenig erforschten Form des Albinismus (OCA4) führen.

Conditions required for seed germination are different among species. Some seed of tropical and subtropical plants may germinate before the maturation of their fleshy fruit, e.g. papaya species, while seed from most deciduous trees have a period of after-ripening before germination. The after-ripening period, also referred to as rest or dormancy has also been observed in some vegetable crops and ornamental flowers.

Studies were conducted in a mountain habitat to determine the effects of altered light and temperature upon the natural growth and/or carbohydrate cycles of Claytonia lanceolata during the period of winter snow cover. Treatments included natural control, light exclusion, and temperature alteration by insulation and by heating for a brief period. Monthly measurements were made of soil temperature (upper 12 cm), shoot development, soluble sugar, and soluble starch. The quantity and quality of light penetrating the snow cover was also determined. About 0.0052% of the available visible light (400-750 nm) penetrated 70 cm of snow and 0.02% penetrated 50 cm of snow. The under snow spectral curve remained constant with a peak at 575 nm, while absolute energy increased 35 times from January to April. Soil temperatures were unchanged by treatments averaging 0.0 to 0.3 C at the surface and slightly warmer at each successive depth. Shoot development and carbohydrate cycles were the same for all treatments. Carbohydrate depletion was generally correlated with increased shoot development. The cycles are traced and discussed. The starch/sugar ratio remained almost constant at one.