With the increasing realization of their involvement in numerous biological processes, synthetic oligosaccharides present promising potential in drug and vaccine discovery. Selective functionalization of hydroxy groups in polyols represent a long-standing goal in chemistry since the chemical synthesis of O-glycosides often requires extensive protecting group manipulation. Organoboron catalysis is a recent strategy for regioselective activation of the equatorial hydroxy group of cis-vicinal diols. Following the initial findings that diarylborinic acid catalyzes the regioselective acylation of carbohydrate derivatives, kinetic studies were conducted to obtain better insight on the mechanism. Thereafter, the ability of diarylborinic acid to catalyze the regioselective alkylation of carbohydrates was demonstrated. Finally, investigations in the capability of diarylborinic acid to influence regiochemical outcome of glycosylation reactions were explored. Similarly, kinetic experiments were devised to shed light on the mechanism of the reaction.

Gestational Diabetes Mellitus develops in 3.7-18% of Canadian women, and can cause serious maternal-fetal complications. Low-GI foods have been shown to increase β-cell function in subjects with impaired glucose tolerance. Theoretically, this effect should improve glucose tolerance and reduce the risk of gestational hyperglycemia. Thus, we aimed to explore the effects of a low-GI diet on glucose challenge test (GCT) results in women at risk for GDM. Women were randomized to receive education during pregnancy focused on incorporation of low- or medium- to high-GI foods. Key foods were provided to assist compliance. Information was obtained from medical records and questionnaires. Ninety-four (94) women completed the study. After adjustment for confounding variables, there was no significant difference in GCT values between intervention groups. Results suggest that low-GI foods do not affect blood glucose control during pregnancy.

The focus of this thesis is to examine the structural properties of polysaccharides produced by bacteria, as well as the dynamic and conformational behavior of a synthetically derived oligosaccharide. The primary structures of the O-polysaccharide repeating units of four different Escherichia coli (E. coli) strains, namely O175, O177, O103 and TD2158, as well as the first report of a capsular polysaccharide produced by lactic acid bacteria Leuconostoc mesenteroides ssp. cremoris PIA2 are reported in paper I–V. Structural analyses have been performed using a combination of nuclear magnetic resonance spectroscopy and chemical component analysis. The elucidated structures in paper I–III, as well as paper V, are composed of linear repeating units of varying composition and length. In paper IV, the structure of the O-polysaccharide repeating unit of E. coli TD2158 is determined to be a branched hexasaccharide structure with a heterogeneous substitution pattern, with either a β-GlcpNAc or β-Glcp residue branching to the backbone chain. Incubation with bacteriophage HK620 tailspike protein shows that the polysaccharide is selectively cleaved at the α-GlcpNAc-(1→2)-α-Rhap-linkage of the backbone chain, yielding a 9:1 ratio of β-GlcpNAc/β-Glcp containing hexasaccharides after digestion. In paper VI the conformational properties of a trisaccharide, which constitutes an internal epitope of the LeaLex hexasaccharide over-expressed on the surface of squamous lung cancer cells, have been analyzed using NMR spectroscopy and molecular dynamics simulations. The β-(1→3)-linkage of the trisaccharide was shown to be highly flexible. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 6: Submitted.</p>

No description available.

The amino acid (2S, 4R)-4-hydroxyproline (Hyp) plays a critical role in animal kingdom as structural protein collagen. It is ubiquitous in plant cell walls performing various functions such as structural assembly, plant hormones, plant growth, defense against pathogens, etc. Glycosylation of Hyp is often seen in plant cell walls with L-Arabinofuranose and D-Galactopyranose and not in animal kingdom. Glycosylation is a post-translational modification, which affects characteristics of proteins and peptides. The main objective of this thesis is to synthesize various L-arabinofuranosylated hydroxyproline model amides and investigate their thermodynamic and kinetic properties of cis/trans amide isomerization. These results are compared with the previous research of D-galactopyranosylated hydroxyproline model amides, which may provide an insight to structural implications for their stability and conformations of peptides and specificity in plants. Both - and -L-arabinosylation of Hyp resulted in the stabilization of trans rotameric state at room temperature while the α-anomer leads to cis rotamer stabilization at higher temperature. Similarly, both unnatural 4S-hydroxyproline (hyp) building blocks resulted in stabilization of trans rotamer but α-anomer shows exo configuration instead of endo. This result shows a reverse trend when compared to galactosylated hydroxyproline building blocks as previous research results in our group. Our results may provide further insight to the role of glycosylation on protein structure and stability in plants.

Abstract available on PDF file. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2013.

In an effort to determine the relative amount of carbohydrates and free fatty acids (FFA) utilized by trained and untrained men at a submaximal workload and the relationship of selected mitochondrial and glycolytic enzyme activities, six trained and six untrained males were exercised for one hour at 50o of their maximal oxygen uptake (V02 max).Muscle samples were taken from the vastus lateralis in three cyclists and from the gastrocmemius in three runners from each group before and after exercise, and later assayed for succinic acid dehydrogenese, malic acid dehydrogenase, lactic acid dehydrogenase, phosphorylane, and carnitine paLmityltransf erase activities, and glycogen levels. Th e post exercise sample was assayed for glycogen, another was sectioned and stained for glycogen and fiber composition (PAS and-glycerolphosphate dehydrogenase) and from a third coupled mitochondria were isolated to determine 14'CO2 production from oxidation of varied levels of 14C-palmityl-CoA. Blood drawn before, immediately after, and thirty minutes after the exercise was assayed for FFA, glycerol, triglycerides, and glucose levels. Activities of oxidative enzymes (SDH, MDH, and CPT) were significantly higher (2-3 times greater) in the trained individuals than in the untrained group. Glycolytic enzyme activities were higher in the untrained group, probably due to higher fast twitch fiber populations. During exercise, FFA levels rose to the same degree in both groups; however, glycerol levels increased almost five times greater during the exercise in the trained subjects indicating the FFA turnover was much larger in the trained subjects. Blood glucose levels increased by an average of 11 mg% during the exercise in the trained subjects but fell by 8 mg% in the others, suggesting a greater selective uptake by the untrained subjects. Muscle glycogen depletion was 66% greater in the untrained group. These catabolic processes were independent of muscle fiber type, indicating that aerobic training increases those enzyme activities associated with FFA oxidation. Trained individuals are thus able to shift to fatty acids as the primary carbon source for the citric acid cycle, sparing glycogen during submaximal work.

Maintenance of adequate muscle glycogen stores has been shown to be essential for endurance performance. For athletes who train on successive days or twice in the same day it is especially important that feeding strategies result in optimal glycogen resynthesis between workouts. The purpose of this investigation was to determine if prior carbohydrate feedings and the form of the carbohydrate consumed affected subsequent endurance performance. Seven endurance trained male cyclists agreed to participate in this study. Each day of testing consisted of two exercise bouts. The first workout was an anaerobic workout consisting of five one minute efforts at 115% VO2max followed by a sprint ride to exhaustion. Each of the sprints was separated from the next by a four minute rest period. For the final ride, the subjects rode at 115% of VO2max. One hour following the completion of the first workout, the subjects began a feeding regimen in which one of four carbohydrate sources were ingested in an amount calculated to provide 1.5g carbohydrate/kg bodyweight/hr for the next four hours. The trials were grouped by carbohydrate forms, dense chewy solid (Powerbars) (DCS), liquid carbohydrate (Gatorlode) (LCHO), and semi-moist solid (Nabisco Snackwells and Fruit Newtons) (SMS). In addition, a water trial (W) was conducted to serve as a control The second workout occurred six hours after the completion of the anaerobic workout and consisted of a one-hour self-paced performance ride on a cycle ergometer. Performance was measured as work (U) performed during the ride. All carbohydrate forms (824.7±109.6 U) improved performance over water (782.0±121.7 U) (p<0.05). In addition, among the various carbohydrate forms, SMS (843.2±94.4 U) significantly improved performance over LCHO (807.3±141 U) and DCS (805.3±115 U) (p<0.05). Carbohydrate feedings between anaerobic and aerobic workouts in the same day improve performance. Also, the physical form of the carbohydrate influences performance. / School of Physical Education

The present study was designed to evaluate the influence of carbohydrate structure on muscle glycogen resynthesis. Eight college-aged male cyclists performed a depletion exercise protocol to decrease vastus lateralis glycogen concentration. This protocol consisted of 60 min of cycling at 75% V O2max, followed by 6 - one min sprints at 125 % V O2max, with a 1 min rest between each sprint. Following the depletion exercise, the subjects consumed - 3000 kcal over a 12 hour period, which was calculated to meet each subject's estimated daily energy expenditure. The carbohydrate (CHO), fat and protein content represented 65:20:15% of the calories consumed, respectively, and totaled 450 - 550 g of CHO. All of the CHO was derived from 1 of 4 solutions: 1) glucose, 2) maltodextrin (glucose polymer), 3) waxy starch (100% amylopectin), or 4) resistant starch (100% amylose). Muscle biopsies were taken after the depletion exercise protocol and 24 hours after the depletion protocol to determine glycogen concentrations. The postdepletion exercise glycogen concentration was similar in all 4 trials, and averaged 234.7 mmol/kg dry weight (d.w.) muscle. Twenty-four hours after exercise, the increase in muscle glycogen concentration was less in the resistant starch trial (90.8 f 12.8 mmol/kg d.w.) than in the glucose, maltodextrin and waxy starch trials, in which glycogen concentration increased 168.7 mmol/kg d.w. Following the 24 h post-depletion exercise biopsy, each subject performed a 30 min cycling time trial, so that the relationship between muscle glycogen concentration and performance could be examined. There were no differences in work output during the time trial or blood lactate concentration immediately following the time trial in any of the trials. In summary, glycogen resynthesis is attenuated following ingestion of carbohydrate with a high amylose content, relative to amylopectin or glucose; however, short duration performance at intensities < 75% VO2max is unaffected. / School of Physical Education

This study examined the effects of pre-exercise carbohydrate (CHO) supplementation on anaerobic exercise performance in adolescent males (n =11; 15.0 ± 0.9 yrs). On separate days, subjects consumed either a CHO or a placebo (PL) beverage followed by 2 Wingate anaerobic tests (WAnT) separated with ten by 10-second sprints. Peak (PP), mean power (MP) and fatigue index (FI) were assessed. Venous blood samples were obtained and analyzed for glucose, lactate, insulin, and catecholamines. A trial by time ANOVA (P < 0.05) was used in the analysis. PP and MP tended to be higher (P < 0.09) in CHO versus PL, and MP tended to decline more in CHO (P < 0.06); Fl for the two WAnT were similar. Glucose concentration significantly increased after CHO consumption and then returned to baseline post-exercise, whereas glucose level remained unchanged over time during PL; similarly observed for insulin. Lactate and catecholamine levels significantly increased over time, but a trial difference was only observed in epinephrine. The tendency for PP and MP to be higher in CHO might suggest a potential ergogenic benefit of pre-exercise CHO although the change in MP over time in CHO and the similarity in Fl might suggest otherwise. / School of Physical Education, Sport, and Exercise Science