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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Novel Synthesis and Applications of Gold Nanoclusters : (1) Sensing of GSH, (2) Sensing of Mercury(II), and (3) Cluster-Assisted LDI MS

Chen, Tzu-Heng 11 July 2012 (has links)
This paper, contain three parts, focus on develop synthesis method for novel functional nanocluster, base on its special optical and reactive property. In the first part, lysozyme VI was mixed with HAuCl4 under acidic condition(pH~3) and yield blue fluorescent Au8 nanocluster. When this Au8 cluster was incubate under alkaline condition (pH~12) a size evolution from Au8 to Au25 took place and monitored with fluorescence spectrum, MALDI MS, DLS. On the other hand, on the role of structural characteristic, fluorescence of Au8 cluster can be quenched by GSH as GSH induced core-etching reaction took place. Take advantage of this reaction, GSH in RBC can be quantitatively analysis by Au8 cluster. Compare with standard medical analysis method, this assay got comparable quantitative result and advantage in environmental friendly, low cost and low sample demand. Follow the first part, it was knowing that Hg2+quench fluorescence of Au25 but Au8 cluster. The second part of research development a ratiometric fluorescence assay for Hg2+ in drinking water sample, by control size evolution of nanocluster mentioned in first part by adding Ag+ into protein direct synthesis nanocluter process. Under optimize condition of bimetallic nanocluster synthesis, two separately fluorescence peak locate under 613 nm and 471 nm represent bigger size and smaller nanoclusters. Using fluorescence intensity ratio of two wavelength, concentration of Hg2+ in water sample can be determined by standard addition method with high reproducibility. Limit of detection was determined to be 0.1 and 0.4 nM, both lower than EPA permitted level in drinking water. On the third part, SA and HAuCl4 was mixed under water contained acetonitrile solution and SA caped nanocluster was form. This nanocluster after self essemble possess special crystalline and surface phenomenon and fit matrix for high reproducible laser desorption/ionization mass spectrometry. Compare with traditional matrix SA, the cluster matrix show 6.6% in RSD with 33%. And the desorption/ionization efficiency of nanocluster matrix is also much higher. Insulin, myoglobin and HSA sample can be quantitative with this matrix with mean RSD lower than 10%.
2

U(VI) bioaccumulation by Paenibacillus sp. JG-TB8 and Sulfolobus acidocaldarius

Reitz, Thomas 01 February 2012 (has links) (PDF)
In this thesis, the interactions of U(VI) with one representative each of the domains Bacteria (Paenibacillus sp. JG TB8) and Archaea (Sulfolobus acidocaldarius) are compared. We demonstrate that at highly acidic conditions (pH ≤ 3), U(VI) is bound to cells of the both strains exclusively via organic phosphate groups. In contrast to this, the U(VI) complexation modes differ between the studied strains at moderate acidic conditions. These differences are assigned to the different cell wall structures of both strains as well as to their different physiological characteristics. We also demonstrate that the aeration conditions can strongly influence the uranium accumulation of facultative anaerobic microorganisms at moderate acidic pH conditions. This finding could clearly be assigned to the dependency of the intrinsic phosphatase activity on the aeration conditions. The second part of this thesis deals with the outermost surface layer (SlaA-layer) of S. acidocaldarius. It was shown that this surface protein is not involved in the U(VI) complexation at highly acidic conditions, covering the physiological pH optimum of S. acidocaldarius. Hence the SlaA layer does not provide a protective function against U(VI) to the cells of this acidophilic archaeon. However, we demonstrated that purified SlaA-layer ghosts (i.e. empty cell sacculi) efficiently interact with gold ions and are a good macromolecular template for the formation of magnetic gold nanoparticles. / In dieser Doktorarbeit werden die Wechselwirkungen von U(VI) mit je einem Vertreter der Bakterien (Paenibacillus sp. JG TB8) und Archeen (Sulfolobus acidocaldarius) verglichen. Wir konnten zeigen, dass U(VI) im sehr sauren Milieu (pH ≤ 3) ausschließlich durch organische Phosphatgruppen an die Zellen beider Stämme gebunden ist. Im Gegensatz dazu unterscheiden sich die Mechanismen der U(VI)-Komplexierung beider untersuchter Stämme bei mäßig sauren Bedingungen voneinander. Diese Unterschiede basieren auf den unterschiedlichen Zellwandstrukturen und physiologischen Eigenschaften beider Stämme. Wir konnten außerdem zeigen, dass die atmosphärischen Bedingungen die Urankomplexierung durch fakultativ anaerobe Mikroorganismen bei mäßig sauren Bedingungen stark beeinflussen kann. Dieses Ergebnis konnte eindeutig auf die von den atmosphärischen Bedingungen-abhängige, enzymatische Aktivität der zelleigenen Phosphatase zurückgeführt werden. Der zweite Teil dieser Arbeit beschäftigt sich mit der äußeren Oberflächenschicht (SlaA-layer) von S. acidocaldarius. Es konnte gezeigt werden, dass dieses Oberflächenprotein nicht an der U(VI)-Komplexierung bei stark sauren pH, welcher dem physiologischen pH Optimum von S. acidocaldarius entspricht, beteiligt ist. Damit stellt der SlaA-layer keinen Schutz gegen Uran für die Zellen dieses azidothermophilen Archaeons dar. Allerdings konnten wir zeigen, dass isolierte „SlaA-layer ghosts“ (d.h. leere Zellhüllen) mit Goldionen interagieren und sich daher als makromolekulares Template für die Herstellung magnetischer Gold Nanopartikel eignen.
3

U(VI) bioaccumulation by Paenibacillus sp. JG-TB8 and Sulfolobus acidocaldarius: U(VI) bioaccumulation by Paenibacillus sp. JG-TB8 and Sulfolobus acidocaldarius: Au(0) nanoclusters formation on the S-layer of S. acidocaldarius

Reitz, Thomas 13 December 2011 (has links)
In this thesis, the interactions of U(VI) with one representative each of the domains Bacteria (Paenibacillus sp. JG TB8) and Archaea (Sulfolobus acidocaldarius) are compared. We demonstrate that at highly acidic conditions (pH ≤ 3), U(VI) is bound to cells of the both strains exclusively via organic phosphate groups. In contrast to this, the U(VI) complexation modes differ between the studied strains at moderate acidic conditions. These differences are assigned to the different cell wall structures of both strains as well as to their different physiological characteristics. We also demonstrate that the aeration conditions can strongly influence the uranium accumulation of facultative anaerobic microorganisms at moderate acidic pH conditions. This finding could clearly be assigned to the dependency of the intrinsic phosphatase activity on the aeration conditions. The second part of this thesis deals with the outermost surface layer (SlaA-layer) of S. acidocaldarius. It was shown that this surface protein is not involved in the U(VI) complexation at highly acidic conditions, covering the physiological pH optimum of S. acidocaldarius. Hence the SlaA layer does not provide a protective function against U(VI) to the cells of this acidophilic archaeon. However, we demonstrated that purified SlaA-layer ghosts (i.e. empty cell sacculi) efficiently interact with gold ions and are a good macromolecular template for the formation of magnetic gold nanoparticles. / In dieser Doktorarbeit werden die Wechselwirkungen von U(VI) mit je einem Vertreter der Bakterien (Paenibacillus sp. JG TB8) und Archeen (Sulfolobus acidocaldarius) verglichen. Wir konnten zeigen, dass U(VI) im sehr sauren Milieu (pH ≤ 3) ausschließlich durch organische Phosphatgruppen an die Zellen beider Stämme gebunden ist. Im Gegensatz dazu unterscheiden sich die Mechanismen der U(VI)-Komplexierung beider untersuchter Stämme bei mäßig sauren Bedingungen voneinander. Diese Unterschiede basieren auf den unterschiedlichen Zellwandstrukturen und physiologischen Eigenschaften beider Stämme. Wir konnten außerdem zeigen, dass die atmosphärischen Bedingungen die Urankomplexierung durch fakultativ anaerobe Mikroorganismen bei mäßig sauren Bedingungen stark beeinflussen kann. Dieses Ergebnis konnte eindeutig auf die von den atmosphärischen Bedingungen-abhängige, enzymatische Aktivität der zelleigenen Phosphatase zurückgeführt werden. Der zweite Teil dieser Arbeit beschäftigt sich mit der äußeren Oberflächenschicht (SlaA-layer) von S. acidocaldarius. Es konnte gezeigt werden, dass dieses Oberflächenprotein nicht an der U(VI)-Komplexierung bei stark sauren pH, welcher dem physiologischen pH Optimum von S. acidocaldarius entspricht, beteiligt ist. Damit stellt der SlaA-layer keinen Schutz gegen Uran für die Zellen dieses azidothermophilen Archaeons dar. Allerdings konnten wir zeigen, dass isolierte „SlaA-layer ghosts“ (d.h. leere Zellhüllen) mit Goldionen interagieren und sich daher als makromolekulares Template für die Herstellung magnetischer Gold Nanopartikel eignen.

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