According to the traditional paradigm, carbohydrates are considered to be poorly immunogenic, T-cell independent antigens. Pure polysaccharides induce specific IgM responses, with minimal class switch to IgG. However, a series of recent investigations has found that a class of zwitterionic polysaccharides (ZPSs)induces a variety of T-cell specific responses such as cell proliferation,cytokine secretion, and regulation of antibody production. The two most studied among this family of molecules is capsular polysaccharide (PS) A1 from the Bacteroides fragilis and the type 1 Streptococcus pneumoniae polysaccharide capsule (Sp1). Active ZPSs share a common structural motif; a high density of positively charged amino and negatively charged carboxyl or phosphate groups. These features are essential for the activity of ZPSs. Since the biological repeating unit of the polysaccharides is not known and biological activity will most likely depend upon a precise sequence, synthesis of the repeating unit of these capsular polysaccharides was undertaken. The goal of this work is to synthesize the repeating unit [3)--DFucpN2AcN4-( 14)--D-GalpA-(13)--D-GalpA-(1] of the type 1 capsular polysaccharide (Sp1) found in S. pneumoniae. 2-Acetamido-4-amino-2,4,6- trideoxy-D-galactopyranose is one of the three monosaccharides of the repeating unit of the Sp1 of Streptococcus pneumoniae. This rare amino sugar is also present in a number of bacterial polysaccharides such as Bacteroids fragilis, Streptococcus mitis and Shigella sonnei. We have developed a novel method to synthesize the orthogonally protected 2-acetamido-4-amino-2,4,6-trideoxy-Dgalactopyranose on a gram scale with high yield starting from readily available Dglucal. The crucial elements of this approach are the introduction of a 4 amino function via intramolecular cyclization of a 3-O-N-benzylcarbamate. The resulting N-benzyloxazolidinone derivative after conversion to the corresponding glycosyl trichloroacetimidate was shown to be an effective glycosyl donor. The assembly of the trisaccharide was successfully carried out from the appropriate galactopyranosides selectively protected at O-6 to permit oxidation to uronic acid derivatives after successful assembly of the target trisaccharide. The trisaccharide was tested for its ability to stimulate interleukin 10 (IL-10) and Interferon-gamma (IFN-) in collaboration with Dr. Dennis L. Kasper (Channing Laboratory, Department of Medicine, Brigham and Womens Hospital, Harvard Medical School, Boston, Massachusetts, USA). Unfortunately the trisaccharide was not active. / Chemistry

No description available.

A strategy to ameliorate non-specific adsorption of oligonucleotides onto Quantum Dots (QDs) is investigated where QDs are being used as a platform for the development of optical bioprobes for nucleic acid detection. Certain zwitterionic structures as coatings on QDs have recently been shown to reduce non-specific binding of proteins. In this thesis, a lysine side chain is attached to a dihydrolipoic acid (DHLA) derivative to create a zwitterionic bidentate ligand that has primary amine and carboxyl termini. Such coatings on CdSe/ZnS QDs were studied to assess adsorption of oligonucleotides across a range of pH to better understand the relationship between surface charge and adsorption. The change of pKa of charged terminal groups on QD surfaces for a variety of different water soluble ligands were evaluated using pseudo-titration curves, and indicated up to 3 orders of magnitude shift of pKa at a QD surface in comparison to pKa in bulk solution.

A strategy to ameliorate non-specific adsorption of oligonucleotides onto Quantum Dots (QDs) is investigated where QDs are being used as a platform for the development of optical bioprobes for nucleic acid detection. Certain zwitterionic structures as coatings on QDs have recently been shown to reduce non-specific binding of proteins. In this thesis, a lysine side chain is attached to a dihydrolipoic acid (DHLA) derivative to create a zwitterionic bidentate ligand that has primary amine and carboxyl termini. Such coatings on CdSe/ZnS QDs were studied to assess adsorption of oligonucleotides across a range of pH to better understand the relationship between surface charge and adsorption. The change of pKa of charged terminal groups on QD surfaces for a variety of different water soluble ligands were evaluated using pseudo-titration curves, and indicated up to 3 orders of magnitude shift of pKa at a QD surface in comparison to pKa in bulk solution.

No description available.

We utilized the tripodal ligand (tris-(3,5-di-tert-butyl-2-hydroxy-phenyl)- phosphine) H3[O3P] to react with 1 equiv of AlR3 (R = Cl, Me, Et, iBu and OiPr). From NMR and X-ray data proved, we could give the stable Al(III) complexes [O3P-H]AlR (R = Cl, Me, Et and iBu). [O3P-H]AlR is a zwitterionic complexes. Because the phenolato phosphine ligand bond a proton at the phosphorous, and Al(III) coordinated three RO- (tris phenolate group) and one alkyl- substituent group. So the Al(III) metal could be carried -1 charge and the phosphorous could be carried +1 charge. When H3[O3P] reacted with AlR3, the original trisphenolato phosphine ligand ([O3P]3-) was changed into a trisphenoato phosphonium ligand ([O3P-H]2-). The [O3P-H]AlMe in the trisphenoato phosphonium group has a proton, and we attempted to use a bese to deprotonate the acidic proton. We chose n-BuLi to react with [O3P-H]AlMe, and successfully gave {[O3P:]AlMe}- ionic complexe. In the {[O3P:]AlMe}- complexe, the lone pair electron of phenolato phosphine group is a nucleophile,It reacted with MeOTf of electrophile. The product of the reaction could give [O3P-Me]AlMe.In this reactions, the original trisphenoato phosphonium ligand ([O3P-H]2-) was changed into a new methyl trisphenoato phosphonium ligand ([O3P-Me]2-). We could utilize H3[O3P] to react with 1 equiv MeOTf in diethyl ether, and gave a new tripodal ligand {H3[O3P-Me]}OTf. Also, we utilized the {H3[O3P-Me]}OTf to react with 1 equiv of AlR3 (R = Cl, Me, Et and iBu). We gave that Al(III) complexes [O3P-Me]AlR (R = Cl, Me, Et and iBu).

The synthesis, characterization and coordination chemistry of novel zwitterionic late transition metal complexes has been carried out, and an investigation of their ability to act as olefin polymerisation catalysts has been conducted. These systems are based on 6- aminofulvene-2-aldiminate ligands (R2AFA¯) which are capable of binding metal centres via two nitrogen donors, delocalising the negative charge into their cyclopentadienyl moiety, thus resulting in the formation of neutral zwitterionic complexes. Preparation and characterisation of mono- and di-substituted complexes such as Ph2AFACuPPh3, (Ph2AFA)2Zn, (Ph2AFA)2Co, (Ph2AFA)2Ni and (Ph2AFA)2Pd have revealed that this type of ligand has enough flexibility to distort upon coordination to the metal depending on geometrical or steric restrictions. As a result, when the ligand coordination involves narrow binding angle of the metal chelate, as it happens in the square-planar species, a severe loss of planarity of the ligand framework is observed, in contrast with the tetrahedral structures where such binding angles are wider. Although the coordination of the ligand primarily occurs through the nitrogen donors, once they have been occupied by the metal centre, it is possible to exploit the aromatic Cp ring for coordination to a Cp*Ru+ unit. In this way, the synthesis and characterisation of two- and tri-metallic complexes [(Cp*Ru)(Ph’2AFA)Pd(η3-C3H5)][BF4] (where Ph’= 2,4,6-trimethylphenyl) and [(Cp*Ru)2(Ph2AFA)2Pd][BF4]2 has been achieved, featuring the R2AFA¯ molecule acting as an ambidentate ligand, binding the palladium atom in a diimine fashion and the ruthenium centres by means of the C5 ring. The synthesis of the complex Cp*RuPh2AFA where the two N atoms are vacant was also achieved and it was found that this compound acts as a proton sponge in the presence of protic solvents. In an effort to prepare AFA-metal complexes which could be of potential use in olefin polymerisation catalysis, two novel species, [(Ph2AFA)Pd(Me)PPh3] and [(Ph’2AFA)Pd(C3H5)] (where Ph’= 2,4,6-trimethylphenyl) have been synthesised and characterised, and polymerisation tests with ethylene have been carried out. Some preliminary screening of other molecules as monomers for polymerisation catalysis has also been conducted.

No description available.

No description available.

The issue of skin friction related injuries has been one of the problems challenging the artificial sports turf industry. It has been identified by users as a major factor impeding acceptance of artificial turf at the professional level. However, information explaining the mechanisms for skin-turf abrasion is limited and little progress has been made, it appears, to derive an appropriate testing method for product approval or in evidence of improvement of the skin-friendliness of these products in sport surface surfaces. This research project focused on exploring the potential for improving the skin-friendliness of artificial turfs through a multi-faceted approach: identifying the contribution of the abrasive-components in modern artificial turf surfaces through mechanical testing; while critically evaluating currently available skin friction standards , evaluating strategies for polymer material modifications to reduce the skin-surface friction; and the designing of an appropriate bench-top set-up for the lab-based assessment of material skin-friendliness. The lack of understanding of skin-turf interaction was addressed by identifying the turf-component that has the greatest influence on the skin-turf friction with the mechanical device used in the current industry standard. The skin -turf frictional profiles of a series of third generation (3G) turf surfaces were examined, in combination with independent measurements of the silicone skin surface roughness pre- and post-friction testing. Results indicated that turf carpets without any infill material exhibited the highest frictional values while surfaces completely filled with either sand or rubber displayed similarly low frictional values, independent of infill type. Morphological measurements also showed the largest decrease in surface roughness for skin samples tested on carpet-only surfaces, indicating a smoothening effect via abrasion. This abrading effect is alleviated with the addition of infill to the surface, with fully-filled surfaces having the least damage to the skin s. This unprecedented study suggests that the carpet may have the largest influence on the overall frictional behaviour of an artificial turf surface narrowing down the turf component to be targeted when applying product improvements to address skin-friendly properties. The strategy of material surface modification was then employed, to study the effect of polyzwitterionic brushes on improving the skin-friendliness of the identified polypropylene substrate. To address the intended application for artificial turfs, a bench-top test was developed to investigate the frictional properties of the hydrated samples outside of commonly used aqueous environments, where an excess of lubricating water molecules is absent. Photo-grafted poly(sulfobetaine methacrylate) (pSBMA) brushes of various irradiation durations were prepared and the improvement in frictional properties was studied. Frictional measurements using silicone skin tips, under both dry and hydrated surface conditions, showed that the applied modification was capable of forming a stable lubrication layer in the absence of excess water, significantly reducing the coefficient of friction by up to 78.8 %. The pSBMA brushes also provided the additional advantage of antifouling exhibiting resistance towards pathogenic Staphylococcus aureus with almost zero surface colonization for well-grafted samples. The low skin -sample friction under ambient conditions and desirable fouling-resistance highlights the potential of pSBMA brushes as a modification strategy for achieving skin-friendly surfaces targeted at reducing the risk of skin abrasions. The tribological implications of counter-surface selection were investigated. Frictional assessments of the pSBMA-modified samples were carried out using standard steel tribo-tips, in addition to the skin tips used. Measurements with the skin tips showed that the hydrated pSBMA brushes were successful in reducing initial skin -sample friction though the effect diminishes with extended testing, attributed to the drying of the interfacial water. The standard steel tribo-tips were unable to reciprocate these results, returning consistently low frictional values regardless of extent of surface modification or hydration. These observations draw attention to the importance of counter-surface selection in frictional assessments, highlighting how appropriate test materials can identify characteristic surface properties while providing an interaction that simulates that of the intended application. The simple experimental set-up used may potentially be enhanced as an intermediate product qualification method in the manufacturing of skin-friendly artificial turf yarns.