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- Kong, Na, 1984-
(författare)
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Carbohydrate-Functionalized Nanomaterials : Synthesis, Characterization and Biorecognition Studies
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on the development of carbohydrate coupling chemistry on nanomaterials and their biological activity studies. It is divided into two parts:In part one, two carbohydrate immobilization approaches, based on perfluorophenyl azide (PFPA)-functionalized silica nanoparticles (SNPs), are presented, where the binding affinity of the glyconanoparticles was evaluated through carbohydrate-lectin interaction. In the first approach, PFPAfunctionalized SNPs were treated with propargylated glycosides and functionalized under copper-catalyzed azide-alkyne cycloaddition (CuAAC) conditions to give glyconanoparticles. For the second approach, a metal-free coupling chemistry based on perfluorophenyl azide-aldehyde-amine cycloaddition (AAAC) was developed for carbohydrate immobilization on PFPA-functionalized SNPs using glycosyl amine and phenylacetaldehyde. Subsequently, a quantitative fluorine nuclear magnetic resonance (19F qNMR) technique was developed to determine the carbohydrate density on the glyconanoparticles. The addition of an internal standard allowed the accurate determination of carbohydrate density, which was then used to calculate the apparent dissociation constant (Kd ) of the glyconanoparticles with lectin by a ligand competition assay. The developed approaches proved general and versatile, and the carbohydrate-presenting nanoplatforms showed high binding specificity in lectin binding.In part two, microwave irradiation was used to functionalize carbon nanomaterials with PFPA followed by carbohydrate conjugation. The microwave-assisted method proved efficient for a number of carbon nanomaterials including carbon nanotubes (CNTs), graphene and fullerene. The carbohydrates on the glyconanomaterials retained their binding patterns towards cognate lectins.
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| 2. |
- Yan, Jiajie
(författare)
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Regenerable Organochalcogen Antioxidants : An Explorative Study
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Antioxidants are widely used to protect organic materials from damages caused by autoxidation, an oxidation process that occurs under normal aerobic conditions. In this thesis, novel multifunctional organoselenium and organotellurium antioxidants were designed, synthesized, and evaluated in search for compounds with better radical-trapping capacity, regenerability, and hydroperoxide-decomposing ability.Selenium was incorporated into ebselenols and hydroxy-2,3-dihydrobenzo[b]selenophenes and tellurium into diaryl disulfides and aryltellurophenols. All newly developed antioxidants were evaluated in a chlorobenzene/water two-phase lipid peroxidation system containing suitable co-antioxidants in the aqueous phase. Ebselenol carrying a hydroxyl group (OH) ortho to selenium showed a two-fold longer inhibition time than the reference α-tocopherol in the presence of aqueous-phase ascorbic acid. 2,3-Dihydrobenzo[b]selenophenes carrying a 5- or 7-OH outperformed α-tocopherol both when it comes to radical-trapping capacity and regenerability. Alkyltellurothiophenols, in situ formed from their corresponding disulfides by tris(2-carboxyethyl)phosphine, were also efficient regenerable radical-trapping antioxidants. The consumption of N-acetylcysteine in the water phase was followed and found to be limiting for the duration of the inhibition. The hydroperoxide-decomposing ability of all organoselenium antioxidants was evaluated. Ebselenols were often better glutathione peroxidase mimics than the parent.In an effort to find out more about antioxidant mechanisms, aryltellurophenols carrying electron donating and electron withdrawing groups in the phenolic or aryltelluro parts were synthesized and OH bond dissociation enthalpies, BDEO-Hs, were calculated. Compounds carrying electron donating groups in the phenolic or aryltelluro part of the molecule showed the best radical-trapping capacity. Deuterium labelling experiments suggested that hydrogen atom transfer could be the rate-limiting step in the antioxidant mechanism.
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