The synthesis of a variety of novel functionalized polymers using living polymerization techniques to achieve functional and stimuli responsive coatings on silica surfaces are described. Since microscopic features on a surface influence the overall wetting properties of the surface, a systematic investigation of the influence of polymer architecture on the microscopic characteristics of the modified surfaces was studied using silane-functionalized linear and novel star-branched polystyrene (PS). Star-branched modifiers provide functional and relatively well-defined model systems for probing surface properties compared to ill-defined highly branched systems and synthetically challenging dendrimers. Using these simple star-shaped macromolecules it was shown that the topographies of the polymer-modified surfaces were indeed influenced by the polymer architecture. A model explaining the observed surface features was proposed. A living polymerization strategy was also used to synthesize centrally functionalized amphiphilic triblock copolymers. The amphiphilic copolymers exhibited stimuli responsive changes in surface hydrophobicity. In spite of multiple solvent exposures, the copolymer films remained stable on the surface indicating that the observed changes in surface properties were due to selective solvent induced reversible rearrangement of the copolymer blocks. The chemical composition of the copolymers was tailored in order to tune the response time of the surface anchored polymer chains. Thus, the polymer coatings were used to reversibly change the surface polarities in an on-demand fashion and could find possible applications as smart adhesives, sensors and reusable membrane devices. In contrast to the afore-mentioned covalent modification approach, which often leads to permanent modification of surfaces, renewable surfaces exhibiting "universal" adhesion properties were also obtained through non-covalent modification. By employing hydrogen bonding interactions between DNA bases, surfaces functionalized with adenine groups were found to reversibly associate with thymine-functionalized polymers. This study describing the solvato-reversible polymer coating was the first demonstration on silica surfaces. A systematic investigation of the influence of surface concentration of the multiple hydrogen bonding groups and their structure on the extent of polymer recognition by the modified surfaces is also discussed. / Ph. D.

Branched-chain amino acids (BCAA) are a group of essential amino acids consisting of leucine, isoleucine, and valine. Leucine, in particular, has signaling functions affecting protein and energy metabolism. Plasma leucine concentration is positively correlated with obesity and associated metabolic disorders. We set out to test the hypothesis that metabolic dysfunction from high fat diets precedes dysfunctional BCAA metabolism. First, BCAA were supplemented to neonatal pigs for 4 weeks to evaluate whether the anabolic signaling function of leucine could increase muscle growth when fed for a longer duration than in previous studies. Neither normal pigs nor low birth weight pigs, which have naturally impaired muscle growth, grew better in response to BCAA supplementation, despite low birth weight pigs expressing less of the leucine sensing protein Sestrin2 in skeletal muscle. Furthermore, high plasma BCAA concentrations caused by the experimental diets had no effect on adiposity, liver fat accumulation, or expression of genes related to fatty acid synthesis, mitochondrial biogenesis, or energy expenditure in the pigs' livers. Having produced strong evidence that long term BCAA supplementation neither improves lean growth nor causes abnormal fat metabolism, we then tested whether fat supplementation changes BCAA metabolism. Pigs were fed milk replacer formula with either low energy (Control), or high energy from long-chain fatty acids (LCFA) or medium-chain fatty acids (MCFA) for 22 days. Although high fat diets did not increase plasma BCAA concentrations, the MCFA diet in particular caused metabolic changes which could lead to fatty liver disease and decreased oxidative BCAA disposal. Expression of fatty acid synthesizing genes were increased in the livers of pigs fed MCFA formula compared to Control and LCFA formula. Oxidation of α-ketoisocaproic acid was decreased in liver homogenate of pigs fed MCFA and LCFA formulas compared to Control. Additionally, hepatic oxidation of α-ketoisovalerate was decreased, and plasma concentration of α-ketoisovalerate was consequently increased, in pigs fed MCFA formula compared to Control, with LCFA formula causing intermediate results. In future research, it would be valuable to feed high MCFA formula for a longer period of time to determine whether nonalcoholic fatty liver disease will develop, and whether plasma BCAA concentrations will increase due to decreased oxidation. Overall, these studies concluded that long term BCAA supplementation does not increase muscle growth in neonatal pigs, but there is also no indication that they cause obesity or dysfunctional fat metabolism. On the other hand, high fat diets cause impairments in BCAA catabolism which may precede elevated plasma BCAA concentrations. / Doctor of Philosophy / Branched-chain amino acids (BCAA) are essential amino acids which are abundant in plant and animal proteins. In addition, the BCAA leucine has functions in protein and energy metabolism. Leucine consumption induces a signal to build new muscle protein. However, leucine concentration is also higher in blood plasma of obese individuals than in non-obese individuals, which has caused uncertainty regarding the safety of leucine consumption. In order to demonstrate that leucine does not cause obesity, we set out to test the hypothesis that high fat diets cause decreased breakdown of BCAA. In the first study, we tested whether one month of BCAA supplementation could increase muscle growth in neonatal pigs. Neither normal pigs nor low birth weight pigs, which have naturally impaired muscle growth, grew better in response to BCAA supplementation, despite low birth weight pigs expressing less of a leucine sensing protein in skeletal muscle. Furthermore, BCAA supplementation caused higher BCAA concentrations in blood plasma, but did not cause pigs to gain more fat, or cause any changes in liver fat metabolism. Having produced strong evidence that BCAA supplementation neither improves lean growth nor causes abnormal fat metabolism, we then tested whether fat supplementation changes BCAA metabolism. Pigs were fed milk replacer formula which was either low calorie (Control), or high calorie from animal fat, which is rich in long-chain fatty acids (LCFA) or high calorie from coconut oil, which is rich in medium-chain fatty acids (MCFA). Although high fat diets did not increase blood plasma BCAA concentrations, the MCFA formula in particular caused changes which could lead to fatty liver disease and decreased breakdown of BCAA. Genes which synthesize new fatty acids were increased in the livers of pigs fed MCFA formula compared to those fed LCFA and Control formulas. Furthermore, liver samples taken from pigs fed the MCFA and LCFA formulas were less able to fully break down metabolites of leucine compared to pigs fed the Control formula. In addition, liver samples from MCFA fed pigs were less able to fully break down metabolites of the BCAA valine, which led to higher concentrations of that metabolite in the blood plasma of pigs fed MCFA formula compared to pigs fed LCFA or Control formula. In the future, it would be valuable to feed a high MCFA formula for a longer period of time to determine whether nonalcoholic fatty liver disease will develop, and whether blood plasma BCAA concentrations will increase due to decreased breakdown. Overall, these studies concluded that long term BCAA supplementation does not increase muscle growth in neonatal pigs, but there is also no indication that they cause obesity or dysfunctional fat metabolism. On the other hand, high fat diets cause impairments in BCAA breakdown which may lead to elevated BCAA concentrations in blood plasma.

The interaction of the protein Rev with Rev Response Element (RRE) RNA is critical to the HIV-1 life cycle as this complex is required for the export of singly-spliced and unspliced mRNAs from the nucleus to the cytoplasm. Disruption of this interaction is considered to be a powerful strategy towards the development of HIV-1 therapeutics. Therefore, we have developed several branched peptide libraries containing unnatural amino acids to target the high-affinity binding site of RRE RNA (RRE IIB), with the idea that branching in peptides can provide multivalent contacts with folded RNA structures and boost binding affinity and selectivity for the target. Unnatural amino acids were incorporated into the library design to encourage non-canonical interactions with the RNA and to improve proteolytic stability. The on-bead high-throughput screening of our first branched peptide library (46,656 sequences) against HIV-1 RRE RNA generated hit peptides with binding affinities in the low micromolar range. We demonstrated that branching in the peptide is required for efficient binding and selectivity towards the RNA, and that the peptides bind a large surface area of RRE IIB. Introduction of boronic acids into branched peptides boosted selectivity of the peptides for RRE IIB, and proved to be a novel and tunable mode of binding towards RNA. Additionally, we revealed that these branched peptide boronic acids (BPBAs) were cell permeable and non-toxic. One BPBA (BPBA3) bound RRE IIB selectively and was able to inhibit HIV-1 replication in vitro, revealing enzymatic cleavage of the RNA upon binding. A second generation BPBA library that introduced acridinyl lysine as an intercalator (4,096 sequences) was screened against RRE IIB. Several hit compounds bound in the low nanomolar regime, and a significant number of compounds inhibited HIV-1 replication in vitro. These BPBAs were also found to severely inhibit the microbial growth of bacteria and fungus, with MICs as low as 1 µg/mL against Staphylococcus aureus, Candida albicans, and Escherichia coli. These compounds were also found to significantly inhibit biofilm formation and growth, and were non-hemolytic. High-throughput screening of a third generation BPBA library containing all unnatural amino acids (46,656 sequences) revealed several hits that bound RRE IIB RNA in the nanomolar range. Sequence motifs present in the hit peptides suggested that the location and composition of amino acids within the branched peptide structure were important for recognizing the RNA target. In particular, lead compounds 2C5 and 4B3 demonstrated selectivity towards RRE, and footprinting experiments combined with SHAPE experiments revealed different interactions of the peptides with the RNA Toxicity assays revealed no impact on cell viability for the majority of hit sequences tested up to 100 µM, and several compounds also demonstrated inhibition of HIV-1 replication. / Ph. D.

Yes / Highly-branched poly(N-isopropyl acrylamide)s in water pass through coil-to-globule transitions. Using calorimetry and the colour change of a solvatochromic dye within the polymer, we show that some compositions have biphasic core–shell morphologies, with globular cores and open coil shells. The two-phase structure is favoured by increased branching and arises because the chain ends penetrate only to a limited degree into the polymer coil.

Yes / Rapid point of care tests for bacterial infection diagnosis are of great importance to reduce the misuse of antibiotics and burden of antimicrobial resistance. Here, we have successfully combined a new class of non-biological binder molecules with electrochemical impedance spectroscopy (EIS)-based sensor detection for direct, label-free detection of Gram-positive bacteria making use of the specific coil-to-globule conformation change of the vancomycin-modified highly branched polymers immobilized on the surface of gold screen-printed electrodes upon binding to Gram-positive bacteria. Staphylococcus carnosus was detected after just 20 min incubation of the sample solution with the polymer-functionalized electrodes. The polymer conformation change was quantified with two simple 1 min EIS tests before and after incubation with the sample. Tests revealed a concentration dependent signal change within an OD600 range of Staphylococcus carnosus from 0.002 to 0.1 and a clear discrimination between Gram-positive Staphylococcus carnosus and Gram-negative Escherichia coli bacteria. This exhibits a clear advancement in terms of simplified test complexity compared to existing bacteria detection tests. In addition, the polymer-functionalized electrodes showed good storage and operational stability.

Yes / Highly branched poly(N-isopropylacrylamide) (HB-PNIPAM), functionalized with vancomycin at the chain ends, acted as a bacterial adhesive and was incorporated into polyurethane foams to form semi-interpenetrating networks. The poly(N-isopropylacrylamide) was labelled with a solvatochromic dye, Nile red. It was found that the thermal response of the polymer was dependent on architecture and temperature dependent color changes were observed within the foam. The foams had open pore structures and the presence of the HB-PNIPAM substantially reduced the shrinkage of the foam as the temperature was increased upto 20 °C. The foams were selectively adhesive for Staphylococcus aureus (Gram-positive bacteria) compared to Pseudomonas aeruginosa (Gram-negative bacteria) and the presence of S. aureus was indicated by increased fluorescence intensity (590 to 800 nm).

<p>This thesis describes the synthesis and characterization ofbranched semi-crystalline polymers. Included in this work isthe SEC characterization of a series of dendrimers. Thebranched semi-crystalline polymers were synthesized in order toinvestigate the concept of their use as powder coatings resins.This concept being that the use of branched semi-crystallinepolymers in a UV-cured powder coating system may offer a lowertemperature alternative thus allowing the use of heat sensitivesubstrates and the added benefit of a reduced viscositycompared to linear polymers.</p><p>A series of branched poly(ε-caprolactone)’s (PCL)(degree of polymerization: 5-200) initiated from hydroxylfunctional initiators were synthesized. The final architectureswere controlled by the choice of initiator structure;specifically the dendritic initiators yielded starbranchedPCL’s while the linear initiator yielded comb-branchedPCL’s. The dendritic initiators utilized were: (1) a3rd-generation Boltorn H-30, commercially availablehyperbranched polyester with approximately 32 hydroxyl groups,(2) a 3rd-generation dendrimer with 24 hydroxyl groups, and (3)a 3rd-generation dendron with 8 hydroxyl groups. Linear PCL wassynthesized for comparison. All dendritic initiators are basedon 2,2- bis(methylol) propionic acid. The comb-branchedpolymers were initiated from a modified peroxide functionalpolyacrylate. The resins were end-capped withmethylmethacrylate in order to produce a cross-linkable system.The polymers and films were characterized using 1H NMR, 13CNMR, SEC, DMTA, DSC, FT-IR, FT-Raman, rheometry and a rheometercoupled to a UV-lamp to measure cure behavior.</p><p>The star-branched PCL’s exhibited considerably lowerviscosities than their linear counterparts with the samemolecular weight for the molecular region investigated (2-550kg mol-1). It was also found that the zero shear viscosityincreased roughly exponentially with M.</p><p>The PCL star-branched resins are semi-crystalline and theirmelting points (Tm) range from 34-50°C; films can beformed and cured below 80°C. The viscoelastic behaviourduring the cure showed that the time to reach the gel point, afew seconds, increased linearly with molecular weight. Thecrossover of G’and G’’was used as the gelpoint. Measurement of mechanical properties of films showedthat the low molecular weight polymers were amorphous whilethose with high molecular weight were crystalline after cure.The polymerization of 5,5-dimethyl-1,3-dioxane-2-one (NPC) fromoligo- and multifunctional initiators was evaluated utilizingcoordination and cationic polymerization. Two tin basedcatalysts, stannous(II) 2-ethylhexanoate and stannous(II)trifluoromethane sulfonate, were compared with fumaric acid.Fumaric acid under bulk conditions resulted in lowerpolydispersity and less chance of gelling. The synthesis ofstar-branched polymers was confirmed by SEC data. The starpolymers exhibited a Tg at 20-30°C and a Tm at about100°C.</p><p>All semi-crystalline resins exhibited a fast decrease inviscosity at Tm. Blends of combbranched semi-crystalline resinsand amorphous resins exhibited a transition behavior inbetweenthat of pure semi-crystalline resins and that of amorphousresins.</p><p>The SEC characterization of a series of dendrimers withdifferent cores and terminal groups showed that the core had animpact on the viscosimetric radius of the core while theterminal groups appeared to have no effect.</p><p><b>Keywords:</b>star-branched, semi-crystalline,comb-branched, ring-opening polymerization,poly(ε-caprolactone), dendritic, thermoset, lowtemperature curing, powder coating, UVcuring,poly(5,5-dimethyl-1,3-dioxane-2-one), size exclusionchromatography, rheology, dendritic aliphatic polyester</p>

This thesis describes the synthesis and characterization ofbranched semi-crystalline polymers. Included in this work isthe SEC characterization of a series of dendrimers. Thebranched semi-crystalline polymers were synthesized in order toinvestigate the concept of their use as powder coatings resins.This concept being that the use of branched semi-crystallinepolymers in a UV-cured powder coating system may offer a lowertemperature alternative thus allowing the use of heat sensitivesubstrates and the added benefit of a reduced viscositycompared to linear polymers. A series of branched poly(ε-caprolactone)’s (PCL)(degree of polymerization: 5-200) initiated from hydroxylfunctional initiators were synthesized. The final architectureswere controlled by the choice of initiator structure;specifically the dendritic initiators yielded starbranchedPCL’s while the linear initiator yielded comb-branchedPCL’s. The dendritic initiators utilized were: (1) a3rd-generation Boltorn H-30, commercially availablehyperbranched polyester with approximately 32 hydroxyl groups,(2) a 3rd-generation dendrimer with 24 hydroxyl groups, and (3)a 3rd-generation dendron with 8 hydroxyl groups. Linear PCL wassynthesized for comparison. All dendritic initiators are basedon 2,2- bis(methylol) propionic acid. The comb-branchedpolymers were initiated from a modified peroxide functionalpolyacrylate. The resins were end-capped withmethylmethacrylate in order to produce a cross-linkable system.The polymers and films were characterized using 1H NMR, 13CNMR, SEC, DMTA, DSC, FT-IR, FT-Raman, rheometry and a rheometercoupled to a UV-lamp to measure cure behavior. The star-branched PCL’s exhibited considerably lowerviscosities than their linear counterparts with the samemolecular weight for the molecular region investigated (2-550kg mol-1). It was also found that the zero shear viscosityincreased roughly exponentially with M. The PCL star-branched resins are semi-crystalline and theirmelting points (Tm) range from 34-50°C; films can beformed and cured below 80°C. The viscoelastic behaviourduring the cure showed that the time to reach the gel point, afew seconds, increased linearly with molecular weight. Thecrossover of G’and G’’was used as the gelpoint. Measurement of mechanical properties of films showedthat the low molecular weight polymers were amorphous whilethose with high molecular weight were crystalline after cure.The polymerization of 5,5-dimethyl-1,3-dioxane-2-one (NPC) fromoligo- and multifunctional initiators was evaluated utilizingcoordination and cationic polymerization. Two tin basedcatalysts, stannous(II) 2-ethylhexanoate and stannous(II)trifluoromethane sulfonate, were compared with fumaric acid.Fumaric acid under bulk conditions resulted in lowerpolydispersity and less chance of gelling. The synthesis ofstar-branched polymers was confirmed by SEC data. The starpolymers exhibited a Tg at 20-30°C and a Tm at about100°C. All semi-crystalline resins exhibited a fast decrease inviscosity at Tm. Blends of combbranched semi-crystalline resinsand amorphous resins exhibited a transition behavior inbetweenthat of pure semi-crystalline resins and that of amorphousresins. The SEC characterization of a series of dendrimers withdifferent cores and terminal groups showed that the core had animpact on the viscosimetric radius of the core while theterminal groups appeared to have no effect. Keywords:star-branched, semi-crystalline,comb-branched, ring-opening polymerization,poly(ε-caprolactone), dendritic, thermoset, lowtemperature curing, powder coating, UVcuring,poly(5,5-dimethyl-1,3-dioxane-2-one), size exclusionchromatography, rheology, dendritic aliphatic polyester / <p>NR 20140805</p>

No description available.

Branched chain sugars display a varied and valuable range of biological activities. This thesis concerns the synthesis of 3,5-di-C-methyl-D-glucose, a potential inhibitor of glycogen phosphorylase (GP), and therefore a proposed therapeutic agent for type 2 diabetes. Chapter 1 looks at the occurrence of branched sugars in the natural world and current therapies for type 2 diabetes. Inhibition of GP is explored, and the molecular modelling studies which led to the design of the project target. Chapter 1 also looks into the development of new foodstuffs, the chemistry and biochemistry of imino sugars and branched hydroxy proline analogues. In Chapter 2, a range of different approaches to 3,5-di-C-methyl-D-glucose are investigated. Most of the initial investigations were carried out on the L-enantiomer, a readily available test system deriving from 2-C-methyl-D-ribono lactone. 2-C-Methyl-D-ribono lactone is synthesised rapidly from D-glucose in a one-pot reaction; as the key starting material for this work, the scalability of this process was investigated. One of the attempted syntheses of di-C-methyl glucose lead to the development of a route towards 3,5-di-C-methyl fructose, a novel dibranched ketose sugar. It was envisaged that through an enzymatic transformation, it might be possible to produce 3,5-di-C-methyl glucose stereoselectively. Synthesis of both enantiomers of 3,5-di-C-methyl glucose and mannose are reported, alongside results of GPb inhibition studies. Analysis of the preferred ring size of a range of di-C-methyl branched sugars and sugar lactones generated in this work is also presented. Chapter 3 explores the chemistry of 2,4-di-C-methyl-L-arabinono lactone, a key intermediate in the synthesis of 3,5-di-C-methyl-L-glucose. From this lactone a novel deoxy sugar, 2-deoxy-2,4-di-C-methyl-L-arabinono lactone, was generated. Routes towards a selection of imino sugars were explored, resulting in the synthesis of a methyl branched isofagomine analogue. A substituted aziridine was synthesised, from which a route to a di-C-methyl branched piperidine was proposed, and a pyrrolidine. Also presented is a synthesis of a dihydroxy di-C-methyl branched proline analogue. Detailed NMR analysis of several of the sugars generated in this work was carried out by Dr M. Wormald, of the University of Oxford Biochemistry department. The results of these investigations are presented in the Appendix. Throughout this work, the presence of quaternary centres has posed a problem with the assignment of relative configuration. As a result, this work has been greatly supported by X-ray crystallography, and the structures shown herein were wholly generated by me. Several other crystals were run during the course of this work, not all pertaining to these projects, and are provided in the CD appendix.