In this thesis a computational complement to experimental observables will be presented. Computational tools such as molecular dynamics and quantum chemical tools will be used to aid in the interpretation of experimentally (NMR) obtained structural data. The techniques are applied to study the dynamical features of biologically important carbohydrates and their interaction with proteins. When evaluating conformations, molecular mechanical methods are commonly used. Paper I, highlights some important considerations and focuses on the force field parameters pertaining to carbohydrate moieties. Testing of the new parameters on a trisaccharide showed promising results. In Paper II, a conformational analysis of a part of the repeating unit of a Shigella flexneri bacterium lipopolysaccharide using the modified force field revealed two major conformational states. The results showed good agreement with experimental data. In Paper III, a trisaccharide using Langevin dynamics was investigated. The approach used in the population analysis included a least-square fit technique to match T1 elaxation parameters. The results showed good agreement with experimental T-ROE build-up curves, and three states were concluded to be involved. In Paper IV, carbohydrate moieties were used in the development of prodrug candidates, to “hide” peptide opioid receptor agonists. Langevin dynamics and quantum chemical methods were employed to elucidate the structural preference of the compound. The results showed a chemical shift difference between hydrogens across the ring for the two isomers as well as a difference in the coupling constant, when taking the dynamics into account. In Paper V, the interaction of the Salmonella enteritidis bacteriophage P22 with its host bacterium, involves an initial hydrolysis of the O-antigenic polysaccharide (O-PS). Docking calculations were used to examine the binding between the Phage P22 tail-spike protein and the O-PS repeating unit. Results indicated a possible active site in conjunction with NMR measurements.

Protein-carbohydrate interactions are pivotal to many biological processes, from plant cell wall degradation to host-pathogen interactions. Many of these processes require the deployment of carbohydrate-active enzymes in order to achieve their intended effects. One such class of enzymes, glycoside hydrolases, break down carbohydrate substrates by hydrolyzing the glycosidic bond within polysaccharides or between carbohydrates and non-carbohydrate moieties. The catalytic efficiency of glycoside hydrolases is often enhanced by carbohydrate-binding modules (CBMs) which are part of the modular structure of these enzymes. Understanding the carbohydrate binding function of these modules is often key to studying the catalytic properties of the enzyme. This thesis investigates the molecular determinants of carbohydrate recognition by CBMs that share similar amino acid sequences and overall three-dimensional structures and thus fall within the same CBM family. Specifically this research focused on two families; plant cell wall binding family 6 CBMs and the alpha-glucan binding family 41 CBMs. Through X-ray crystallography, isothermal titration calorimetry and other biochemical experiments, the structural and biophysical properties of CBMs were analyzed. Studying members of CBM family 6 allowed us to establish the overall picture of how similar CBMs interact with a diverse range of polysaccharide ligands. This was found to be due to changes in the topology of the binding site brought about by changes in amino acid side chains in very distinct regions of the binding pocket such that it adopted a three-dimensional shape that is complementary to the shape of the carbohydrate ligand. Members of CBM family 41 were shown to have nearly identical modes of starch recognition as found in starch-binding CBMs from other families. However family 41 CBMs are distinct as they are found mainly in pullulanases (starch debranching enzymes) and have developed binding pockets which are able to accommodate alpha-1,6-linkages, unlike other starch-binding CBM families. These are the first studies comparing multiple CBMs from within a given CBM family at the molecular level whose results allow us to examine the distinct modes of carbohydrate recognition within a CBM family. Analysis of the family 41 CBMs revealed that these CBMs are mainly found in pullulanases from pathogenic bacteria. Members from Streptococcal species were shown to specifically interact with glycogen stores within mouse lung tissue, leading us to investigate the role of alpha-glucan degradation by the pullulanase SpuA in the pathogenesis of Streptococcus pneumoniae. SpuA targets the alpha-1,6-branches in glycogen granules, forming alpha-1,4-glucan products of varying lengths. The overall three-dimensional structure of SpuA in complex with maltotetraose was determined by X-ray crystallography and showed that its active site architecture is optimal for interacting with branched substrates. Additionally, the N-terminal CBM41 module participates in binding substrate within the active site, a novel feature for CBMs. This is the first study of alpha-glucan degradation by a streptococcal virulence factor and aids in explaining why it is crucial for full virulence of the organism.

Doctor of Philosophy / Department of Chemical Engineering / Keith L. Hohn / Superparamagnetic iron oxide nanoparticle functionalization is an area of intensely active research, with applications across disciplines such as biomedical science and heterogeneous catalysis. This work demonstrates the functionalization of iron oxide nanoparticles with a quasi-monolayer of 11-sulfoundecanoic acid, 10-phosphono-1-decanesulfonic acid, and 11-aminoundecanoic acid. The carboxylic and phosphonic moieties form bonds to the iron oxide particle core, while the sulfonic acid groups face outward where they are available for catalysis. The particles were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectrometry (XPS), and dynamic light scattering (DLS). The sulfonic acid functionalized particles were used to catalyze the hydrolysis of sucrose at 80˚C and starch at 130˚C, showing a higher activity per acid site than the traditional solid acid catalyst Amberlyst-15, and comparing well against results reported in the literature for sulfonic acid functionalized mesoporous silicas. In sucrose catalysis reactions, the phosphonic-sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic-sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. Between the two sulfonic ligands, the phosphonates produced a more tightly packed monolayer, which corresponded to a higher sulfonic acid loading, lower agglomeration, lower recoverability through application of an external magnetic field, and higher activity per acid site for the hydrolysis of starch. Functionalizations with 11-aminoundecanoic acid resulted in some amine groups binding to the surfaces of iron oxide nanoparticles. This amine binding is commonly ignored in iron oxide nanoparticle syntheses and functionalizations for biomedical and catalytic applications, affecting understandings of surface charge and other material properties.

Pappelsorten (Populus) für den Anbau in Kurzumtriebsplantagen sollten neben einer hohen Biomasseproduktion und der Vermehrbarkeit über Steckhölzer auch Trockentoleranz aufweisen. Trockenheit stellt einen wichtigen abiotischen Stressor dar, der das Wachstum der Pflanze, ihre Vitalität und ihre Produktivität negativ beeinflussen kann. Polyploide Sorten von Getreidepflanzen (Triticum), krautigen Pflanzen (Lonicera, Spathiphyllum und Nicotiana) aber auch Baumarten (Betula) zeigen eine höhere Toleranz gegenüber Stress, wie z.B. Trockenstress, im Vergleich zu Sorten mit niedrigerem Ploidiegrad. Hybridaspen Populus tremula (L.) x P. tremuloides (Michx.) der Sektion Populus können auch auf Grenzertragsböden ökonomische Zuwächse verzeichnen, auf denen andere Baumarten ausfallen. Den Hybridaspen fehlt allerdings die Vermehrbarkeit über Steckhölzer. Anderen Pappelarten der Sektionen Tacamahaca und Aigeiros wie beispielsweise P. nigra (L.) and P. trichocarpa (Torr. & Gray) x P. deltoides (Bartram ex Marsh) zeigen diese entscheidende Eigenschaft. Da Kreuzungen zwischen den Sektionen Populus und Tacamahaca oder Aigeiros auf natürlichem Weg schwierig sind, wurde die Methode der somatischen Hybridisierung eingesetzt. Der Klon P. tremula x P. tremuloides ('Münden 2') wurden als ein Fusionspartner und einer der Klone P. x canescens (INRA clone No. 717 1‑B4), P. nigra oder P. trichocarpa x P. deltoides (B19) als zweiter Fusionspartner in Hybridisierungsexperimenten verwendet. Blattmorphologisch und durch Mikrosatellitenanalysen konnten die erhaltenen Fusionsprodukte dem Ausgangsklon P. tremula x P. tremuloides ('Münden 2') zugeordnet werden, wiesen dabei aber einen tetraploiden Chromosomensatz auf. In der vorliegenden Dissertation war das zentrale Ziel, Trockenstressreaktionen tetraploider Hybridaspenlinien (HAL) im Vergleich zur diploiden Ausgangslinie P. tremula x P. tremuloides ('Münden 2') zu untersuchen. Dazu wurden die folgenden Fragen aufgestellt. (i) Sind die tetraploiden HAL dem diploiden Ausgangsklon unter Trockenheit überlegen z.B. hinsichtlich des Wasserverbrauchs und des Verwelkungs- und Vertrocknungszeitpunktes der Blätter? (ii) Unterscheiden sich die tetraploiden HAL von dem diploiden Ausgangklon in morphologischen Ausprägungen wie beispielsweise der Stomatamorphologie, der Höhe, der Biomasse und der Gesamtblattfläche? (iii) Ist die höhere Trockentoleranz der tetraploiden HAL durch den erhöhten Ploidiegrad verursacht? (iv) Zeigen die tetraploiden HAL unter Trockenstress früh physiologische Veränderungen im Kohlenhydratgehalt, dem relativen Blattwassergehalt und der stomatären Leitfähigkeit? (v) Gibt es genetische Modifikationen abgesehen von der Tetraploidie wie z.B. Duplikationen und Deletionen, die eventuell Einfluss auf das Trockensressverhalten haben könnten? In einem ersten Experiment wurden vier tetraploide HAL untersucht. Zwei HAL zeigten einen geringeren Wasserverbrauch und drei HAL eine spätere Verwelkung als der diploide Ausgangsklon. Außerdem entwickelten die tetraploiden HAL eine geringere Stomatadichte, größere Stomata und eine vergleichbare oder geringere Höhe, Biomasse und Gesamtblattfläche im Vergleich zum diploiden Ausgangsklon. Das zweite Experiment wurde mit vier diploiden und 16 weiteren tetraploiden HAL durchgeführt. Auch die diploiden Linien stammten aus Protoplastenfusions-experimenten. Die tetraploiden HAL wiesen im Mittel eine höhere Überlebensrate als die diploiden HAL auf, entwickelten aber durchdschnittlich ein geringeres Höhenwachstum. Unter Berücksichtigung der Höhe verwelkten 11 tetraploide, aber keine diploide HAL später als der diploide Ausgangsklon. In einem dritten Experiment wurden zwei Linien aus dem zweiten Experiment ausgewählt, die vergleichbares Höhenwachstum zeigten, aber später verwelkten als der diploide Ausgangklon. Es wurden physiologische Merkmale wie der Wasserverbrauch und der Verwelkungszeitpunkt der Blätter beobachtet und der relative Blattwassergehalt, die stomatäre Leitfähigkeit und der Kohlenhydratgehalt in einer Zeitreihe untersucht. Geringerer Wasserverbrauch im Vergleich zum diploiden Ausgangsklon konnte in beiden tetraploiden HAL gezeigt werden. Diese Beobachtung deckt sich mit dem höheren relativen Bodenwassergehalt der tetraploiden HAL im Vergleich zum diploiden Ausgangsklon. Insgesamt spricht das für geringeren Trockenstress in den tetraploiden HAL. Auf der anderen Seite sollte ein geringerer Wasserverbrauch auch eine geringere stomatäre Leitfähigkeit nach sich ziehen. Dies war in den tetraploiden HAL nicht durchgehend der Fall. Relativ zur Kontrolle konnten die tetraploiden Linien aber eine höhere stomatäre Leitfähigkeit bei Bodenwassergehalten aufrechterhalten, bei denen die diploide Ausgangslinie bereits ihre Stomata geschlossen hatte. Dies weist ebenfalls auf eine höhere Trockentoleranz der tetraploiden HAL hin. Genetische Modifikationen wie beispielsweise Duplikationen und Deletionen wurden mit Hilfe von “copy number variation”(“Kopienzahlvariation”)-Analysen an drei tetraploiden HAL und der diploiden Ausgangslinie durchgeführt. Die drei tetraploiden Linien zeigten vergleichbares Höhenwachstum, aber spätere Verwelkung als die diploide Ausgangslinie. Bei dieser Analyse konnten nur drei Segmente detektiert werden, die bei allen drei tetraploiden HAL im Vergleich zum diploiden Ausgangsklon verändert vorlagen. Die putativen Gene der detektierten Segmente wiesen keine Annotation auf. Eine der drei tetraploiden HAL zeigte eine hohe Anzahl von 90 Segmenten, die hier aber weder in dem diploiden Ausgangsklon noch in den beiden anderen tetraploiden Linien erhöht vorlagen. Diese Linie zeigte zwar eine höhere Trockentoleranz als der diploide Ausgangsklon, aber nicht gegenüber der anderen untersuchten tetraploiden HAL (Experiment 3). Beide tetraploiden HAL waren bezüglich des Wasserverbrauchs, des Verwelkungszeitpunktes und der stomatären Leitfähigkeit ähnlich. Dies lässt vermuten, dass die Trockentoleranz durch die Tetraploidie und nicht durch weitere genetische Modifikationen bedingt ist. Trotzdem ist eine weiterführende funktionelle Untersuchung der drei Segmente, die in allen tetraploiden HAL verändert auftraten, sinnvoll, da auch hier ein trockenrelevantes Gen verändert sein könnte. Um eine Relevanz der putativen Gene bezüglich Trockenheit zu testen, könnte zukünftig das Verhalten von Knock-out-Mutanten, denen die entsprechende Sequenz fehlt, unter Trockenstress untersucht werden. Abschließend ist zu bemerken, dass neben den hier untersuchten HAL mehrere hundert Fusionsprodukte in einem Verbundprojekt genetisch charakterisiert wurden. Die Heterofusionsfrequenz war äußerst gering und die Hybriden waren bereits in der in vitro Phase nicht überlebensfähig. Geringe Heterofusionsfrequenz wurde beteits in anderen Arten beobachtet (Cyclamen, Brassicaceae, Fabaceae, Poaceae, Solanaceae). Da in dieser Dissertation nur Homofusionslinien verwendet wurden, wurde die Vermehrbarkeit über Steckhölzer nicht getestet, sondern der Fokus auf das Trockenstressverhalten der tetraploiden Homofusionslinien gelegt. Zusammenfassend zeigen die Ergebnisse, dass veränderte morphologische Ausprägungen und eine höhere Trockentoleranz in den HAL mit erhöhten Ploidiegrad auftraten. Dies prädestiniert die tetraploiden Linien für Standorte, an denen Wasser als limitierender Faktor auftritt und hohe Ausfallraten durch Dürre erwartet werden.

Sammanfattning   Bakgrund: Övervikt och fetma har blivit en hälsofarlig nödsituation i västvärlden, i synnerhet bukfetma som är en av de viktigaste riskfaktorerna för kardiovaskulära sjukdomar. Den västerländska dieten domineras av högt förädlade livsmedel till låg kostnad vilket snabbt har utvecklat övervikt och överviktsrelaterade sjukdomar. Det finns olika behandlingsmetoder för att minska övervikt och fetma, där kost är en viktig komponent. Lågkolhydratkost kommer alltmer i fokus, som ett alternativ till de rådande näringsrekommendationerna. För att stödja och motivera personer med övervikt och fetma kan sjuksköterskan förmedla en personcentrerad egenvård enligt Orem. Sjuksköterskan skall enligt lag arbeta evidensbaserat och det krävs ständig uppdatering av forskningsläget. Syfte: Syftet var att studera effekten av lågkolhydratkost hos personer med övervikt och fetma. Metod: Litteraturöversikten är av kvantitativ metod och innehåller 15 vetenskapliga artiklar. Analysmodellen som användes var Fribergs analys. Resultat: Effekter av lågkolhydratkost visar signifikanta förbättringar i framförallt viktnedgång men även i blodtryck, blodfetter och blodsocker. De största effekterna av de olika variablerna sågs efter sex månader. Dessa effekter gav ofta en minskad användning av antidiabetika som följd. Slutsats: Då lågkolhydratkost har gynnsamma effekter på viktnedgång, blodfetter och blodsocker är behovet stort av långtidsstudier. Sjuksköterskan har en viktig roll att stödja och motivera personer med övervikt och fetma till livsstilsförändringar. Nyckelord: Viktnedgång, ketogen kost, lågkolhydratkost, egenvård / Summary Low-carbohydrate diets for overweight and obesity - A literature review   Background: Overweight and obesity has become a health hazard emergency in the western world, especially abdominal obesity which is one of the major risk factors for cardiovascular diseases. The Western diet is dominated by highly processed food at low cost, which has rapidly developed obesity and obesity related diseases. There are various treatment methods to reduce overweight and obesity by diet which is an important component. Low-carbohydrate diet comes increasingly into focus, as an alternative to the current nutritional recommendations. To support and motivate people with overweight and obesity, the nurse can convey a person-centered self-care according to Orem. The nurse should, by law, set their work based on evidence and that requires a continuous update of available research. Objective: The objective was to study the effect of low-carbohydrate diet in people with overweight and obesity. Method: The literature review is the quantitative method and contains 15 scientific articles. The analysis model used was Friberg analysis. an important role to support and motivate people with overweight Result: Effects of low-carbohydrate show significant improvements especially in weight loss but also in blood pressure, blood fats and blood sugar. The main effects of the different variables were observed after six months. These effects often gave a reduced use of antidiabetic drugs as a result. Conclusion: Since low-carbohydrate proven to have beneficial effects on weight loss, blood fat and blood sugar there is a great need for long-term studies. The nurse has and obesity to lifestyle changes. Keywords: Weight loss, ketogenic diet, low-carbohydrate diet, self-care

The principle aims of this work were two fold; firstly to identify the current dietary intakes (specifically dietary glycaemic carbohydrate (CHO)) and physical activity (PA) and cardiorespiratory fitness (CRF) levels of a UK, postpubertal, adolescent population (n = 105) and assess the relationship between these factors, adiposity and cardiometabolic health. Diet and health relationships were assessed whilst accounting for energy misreporting and controlling for levels of PA and CRF. The effect of excluding dietary misreporters on the associations between glycaemic CHO and health was assessed whilst comparing an established technique (the Goldberg equation) to a novel approach (the ratio of energy intake (EI) to energy expenditure (EE)), which utilised RT3 accelerometry data (EI:EE(RT3)). Associations of PA and metabolic risk factors were also assessed whilst comparing two child specific PA thresholds for the assessment of PA subcomponents. Secondly, the impact of a flexible, ad libitum, low GI dietary intervention on cardiometabolic health was examined in an „at risk‟, overweight, postpubertal, adolescent population. Glycaemic index (GI) but not glycaemic load (GL) was shown to be associated significantly with anthropometric measures (body mass index (BMI), waist circumference (WC)) and adiposity (body fat percentage (BF%)) in this general group of post-pubertal adolescents from Bedfordshire. When adjusting for dietary intake, CRF was also associated with adiposity but PA was not. The prevalence of misreporting varied depending on the method used to assess the validity of dietary intakes; between 23% and 31% increasing to 62.1% (in overweight) of adolescents under reported energy intakes and up to 11.1% over reported. The novel application of a triaxial accelerometer to measure EE resulted in more under and over reporters being identified than when compared to the widely used Goldberg equation. Increased dietary GI was associated with increased odds of having a high WC; however, associations between GL and other risk factors were less clear; no associations with risk were observed. Excluding dietary misreporters from analysis had important implications for these associations. Only after removal of misreporters by EI:EE(RT3) was a borderline significant positive association between GL and blood glucose (BG) revealed using multiple analysis of covariance (MANCOVA), that was not present in prior analyses. Increased GI (moderate vs low GI intake) was significantly associated with reduced high density lipoprotein cholesterol (HDL) and increased triglyceride (TG) levels (borderline significant) after removal of misreporters. In addition, using different PA thresholds to assess PA intensity resulted in different relationships between PA subcomponents and metabolic risk factors. Regardless of the threshold used, evidence suggested that limiting sedentary (SED) behaviour and engaging in moderate to vigorous PA (MVPA) is beneficial for blood pressure (BP) in this adolescent population. Additionally, irrespective of the threshold utilised, higher levels of vigorous PA (VPA) were associated with reduced odds of having a high clustered risk score and the associations observed between CRF and risk factors were stronger than those observed with PA. Despite a lack of significant improvement in individual metabolic risk factors as a result of the low GI (LGI) dietary intervention, there was a significant reduction in clustered risk score for the LGI group at week 12. A borderline significant improvement in glycated haemoglobin (HbA1c) was also observed as a result of the LGI intervention compared to those in the control group. Conversely, there appeared to be an unfavourable effect of the LGI diet on fasting insulin levels and thus the diet‟s impact on health overall is unclear. The small sample size of this randomised controlled trial (RCT) means that caution is required when interpreting the results. These data suggest that future research in this age group should target improvements in CRF and a lower dietary GI to reduce adiposity. Controlling for dietary misreporting appears to have a significant impact on associations of glycaemic CHO and cardiometabolic health and should be an important consideration of future research. The low GI intervention may be an effective approach for reducing glycaemic CHO, whilst maintaining a healthy macronutrient intake, in comparison to more restricted dietary regimens published in the literature. However, the impact of this regime needs to be confirmed utilising a larger sample of adolescents. This may provide a useful approach for future research aiming to assess the impact of reduced GI and GL.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The abundance and diversity of carbohydrate and protein resources in the southern Cape of South Africa may well have aided the survival of modern humans through the harsh climatic conditions of the late Pleistocene. Until now, the carbohydrate resources, in particular the underground storage organs (USOs) of some plant species have not been described from a forager’s perspective. This is baffling when one considers that the Cape Floristic Region of South Africa harbors the highest diversity of geophyte (herbaceous plants which possess USOs) species in the world. I report on USO distribution and abundance in the southern Cape of South Africa and on the effort, nutritional return and energetic return rates of harvesting these USOs. To determine their distribution and abundance, I assessed identity and abundance in a hundred 25m2 plots. These data, along with biomass data of every species sampled, allowed me to quantify the variation of this potential food source over different habitat types in the southern Cape landscape. Furthermore, I observed the time it took for human subjects to gather a sample of six USO species in three different vegetation types and in two seasons. Proximal analyses of the nutritional content of each of these species provided data which, when combined with foraging time, enabled a basic quantification of the return rate of energy (in calories) per time unit. There is high variability in the distribution of edible USO abundance and biomass across the study area, with some sites having very high biomass. Such biomass hotspots are likely to have been targeted by foragers, returning biomass values comparable to other studies which have been conducted on extant hunter-gatherer communities. Due to considerable variation over the landscape, the hotspots of biomass did not correlate significantly with any abiotic variables we measured. This suggests that hotspots of high biomass may have been challenging to find, unless the cognitive skills required to locate such patches were sufficiently developed – certainly excellent knowledge of the landscape and botany would have been crucial if survival depended on locating these diet items. USO species belonging to the Iridaceae family had the highest overall and average biomass in the area, so it is not surprising that this family is best represented amongst USO plant remains found in the archaeological record. Little effort (time) was required to obtain the six species of USOs we observed, although the weights obtained were also low. The nutritional returns of the six test species were higher than in other studies. The return rates per simulated foraging event in this study therefore compare favorably to the anthropological observations of extant hunter-gatherer communities. The lines of evidence presented in this thesis therefore lend support to the hypothesis that the USO resources of the southern Cape would have provided a large component of the carbohydrate requirements for sustaining hunter-gatherer communities. The data set presented in this thesis can be considered a baseline for future studies. / AFRIKAANSE OPSOMMING: Die digtheid en diversiteit van koolhidraat- en proteïenhulpbronne in die Suid-Kaap van Suid-Afrika mag die oorlewing van die moderne mens beïnvloed het tydens die ongunstige klimaatstoestande wat geheers het deur die laat Pleistoseen. Tot op hede is die koolhidraathulpbronne in die area nie beskryf vanuit ‘n kosversamelaar se perspektief af nie, spesifiek nie die koolhidrate wat deur ondergrondse stoororgane (OSO's) van sommige plantspesies verskaf kan word nie. Dié feit is verstommend as mens in ag neem dat die Kaapse Floristiese Streek van Suid-Afrika die hoogste geofietspesies (kruidagtige plante met OSO's) diversiteit ter wêreld het. Ek rapporteer oor die verspreiding en digtheid van OSO's in die Suid-Kaap en op die inspanning, voedingswaarde en energie-opbrengskoerse verbonde aan die oes van dié OSO's. Verspreiding en digtheid is bepaal oor ʼn honderd 25m2 plotte. Dié data, saam met die biomassa-data van elke spesie wat geïdentifiseer was, is gebruik om potensiële voedselbronne te kwantifiseer in verskillende habitattipes in die Suid-Kaap. Ek het verder die tyd wat dit neem vir mense om die ses geïdentifiseerde OSO-spesies te oes in drie verskillende habitatte en twee seisoene waargeneem. Voedingswaarde-data, tesame met OSO-oestyd-data, is gebruik vir die basiese berekening van energie-opbrengskoerse van spesies deur middel van proksimale analises. Daar is hoë variasie in die verspreiding, digtheid en biomassa van eetbare OSO's gevind in die studie-area, met sommige plotte wat baie hoë biomassa bevat het. Hierdie areas van hoë biomassa sou heel waarskynlik deur kos-versamelaars geteiken gewees het, en gevolglik hoë opbrengste van biomassa bied, wat vergelykbaar is met die biomassa-waardes wat waargeneem word binne areas waar huidige jagter-versamelaar-gemeenskappe tans oorleef. As gevolg van die aansienlike variasie wat waargeneem is oor die landskap het die hoë-biomassa-areas nie beduidend gekorreleer met enige abiotiese veranderlikes wat gemeet is nie. Dit dui daarop dat hoë-biomassa-areas moeilik kan wees om te vind, tensy kognitiewe vermoëns wat noodsaaklik is om kolle van hoë biomassa te vind ontwikkel was. OSO-spesies wat aan die Iridaceae-familie behoort het die hoogste algehele en gemiddelde biomassa in die area gehad. Dit is dus nie verbasend dat dié familie die beste verteenwoordig word in die argeologiese rekord van OSO-plantoorskot nie. Min inspanning (tyd) was nodig om die OSO's van die ses geïdentifiseerde spesies te bekom, alhoewel die massa wat bekom is ook laag was. Die voedingswaarde-opbrengs (per eenheidsmassa) van die ses toetsspesies was hoër as in ander studies. Die energie-opbrengskoers per versamelingsgebeurtenis het gevolglik ook gunstig vergelyk met die antropologiese waarnemings wat van huidige jagter-versamelaars gemeenskappe gemaak is. Die resultate van hierdie studie ondersteun die hipotese dat die OSO-hulpbronne in die Suid-Kaap 'n groot komponent van die koolhidraat-vereistes van jagter-versamelaar-gemeenskappe sou gewees het. Die datastel wat in dié tesis aangebied word kan as 'n basisverwysing dien vir toekomstige studies.

<p>In 1957 Vroom presented an article that dealt with the kinetics of the sulphate cook. He showed that the lignin dissolution exhibited a temperature/time dependency that could be explained by the Arrhenius equation and that the reaction was of first order with respect to lignin. However, even before Vroom introduced the H-factor all wood components were assumed to react according to a first order reaction. In recent years progresses in this area have been made. Lignin for example is nowadays considered to dissolve during three parallel first order reactions, all with differences in activation energies.</p><p>When the kinetics are evaluated, several cooking series at different temperatures and concentrations of active cooking chemicals are needed. The data points obtained are then fitted into some equation. If the concentration of the active cooking chemicals is constant, the activation energies and the chemical dependency for the dissolution of wood components can easily be found. In order to simplify the evaluations of the kinetics, very high liquor-to-wood ratios are sometimes used, often as high as 50:1 or even 75:1. In this manner, the chemical concentrations are almost constant during the cook. The problem is that in the normal industrial cook where the liquor-to-wood ratio is about 4:1, the chemical concentration is not constant. This is due mostly to the alkali consumption that takes place in the cook for example when neutralising the acidic groups in the hemicelluloses.</p><p>A disadvantage with high liquor-to-wood ratios is the high dilution of the dissolved organic matter. A high concentration of dissolved lignin boosts the dissolution of the remaining lignin in the wood residue and xylan can redeposit on the fibres when its concentration in the cooking liquor is high.</p><p>The aim of this project was to describe how different liquor-to-wood ratios influence the kinetics during sulphate cooking of spruce.</p>

The consequences of ingesting different carbohydrate solutions on fluid movement and availability have not been systematically examined. In addition, the role of carbohydrate in the post-exercise rehydration period has received little attention despite the need for substrate replenishment following exercise and the role of carbohydrates in stimulating water absorption in the intestine. The aims of this thesis were to assess fluid absorption characteristics and availability of solutions containing increasing concentrations of glucose and to evaluate their role in the restoration and maintenance of fluid balance following a period of exercise-induced dehydration. The ingestion of a single bolus of a commercially available hypertonic 18% carbohydrate solution (chapter 3) and a hypertonic 10% glucose solution (chapter 4) resulted in reductions in plasma volume that are most likely due to acute net secretion of water into the intestinal lumen. When investigating recovery of whole body hydration status after sweat loss, a hypertonic 10% glucose-electrolyte solution maintained whole body fluid balance for a longer period than a hypotonic 2% glucose-electrolyte solution and an electrolyte only solution when a fixed volume of fluid was consumed during a rehydration period of one hour following cycle exercise in the heat (chapter 5). When fluid was consumed ad libitum over a two hour period following similar cycle exercise in the heat, a hypertonic 10% glucose-electrolyte solution was as effective in restoring and maintaining fluid balance as a 2% hypotonic glucose-electrolyte solution and an electrolyte only solution (chapter 6). The reduced rate of gastric emptying that accompanies the ingestion of high carbohydrate solutions was likely to be the primary cause for the difference in urine production reported between thetrials during this study (chapter 7). In conclusion, ingestion of hypertonic carbohydrate solutions results in a reduction in extracellular fluid volume that is most likely due to secretion of water into the intestinal lumen and the carbohydrate content of an ingested solution is of importance in the post-exercise rehydration period.

The aim of feed formulation in aquaculture is to supply a suitable diet that provides nutritional requirements at relatively low cost. Carbohydrates are the most economic energy source for animals compared to protein and lipid; however, fish have limited capacity for dietary carbohydrate utilization. Trivalent chromium is an essential micronutrient for carbohydrate metabolism in vertebrates. The primary objective of this thesis was to enhance understanding of the effects of organic and inorganic forms of Cr on carbohydrate utilization, growth performance, gene expression and activity of specific key liver enzymes in carp Cyprinus carpio. In addition, effects of dietary Cr on body composition, Cr tissue content, blood cells DNA damage, and tissue histopathology (liver and gut) were evaluated. The first experiment (Chapter 3) tested levels of dietary Cr (0, 0.2, 0.5, 1.0, 1.5, 2.0 mg Cr kg-1 as Cr chloride) to determine Cr requirement; the second experiment (Chapter 4) compared bioavailability of different forms of Cr (Cr chloride, Cr picolinate, and Cr yeast); and the third experiment (Chapter 5) evaluated different levels of Cr yeast (0.5, 1.0, and 2.0 mg Cr kg-1) on utilization of a starch or dextrin-based diet. A Cr supplementation of 0.5 mg Cr kg-1 (regardless of form of Cr) produced highest growth performance; whereas 2.0 mg Cr kg-1 did not differ from control. The 0.5 mg Cr kg-1 also enabled carp to utilize complex carbohydrates (e.g., starch) and did not affect final body composition. Only 2.0 mg Cr kg-1 caused DNA damage in blood cells and tissue damage (liver and gut histopathology). Cr content in whole body increased with dietary Cr, but Cr did not affect hexokinase gene expression. Overall, results indicate that Cr can improve growth performance of carp and that Cr supplementation can enhance utilization of carbohydrates in fish feed.