Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2008. / "June 2008." / Includes bibliographical references (leaves 133-140). / In the past fifteen years, evidence provided by many independent research groups have indicated higher numbers of cells exhibiting damage than expected based on the number of cells traversed by the radiation. This phenomenon has been coined as the "bystander effect". The purpose of this study was to characterize the ability of irradiated tumor cells to induce bystander effects in co-cultured cells. Human DU-145 prostate carcinoma cells were grown on a 1.4 [mu]m-thick mylar membrane in specially constructed cell culture dishes for irradiation with alpha particles (average energy 3.14 MeV) from a 241Am source, or in 6-well plates for irradiation with 250 kVp x-rays at 25°C. In parallel experiments, the tumor cells were incubated at 4°C for one hour prior to irradiation and irradiated on ice to test the nature of the bystander signal. Bystander cells were placed into the medium above the irradiated DU-145 and were co-incubated for a length of time. The bystander effect endpoints measured in either DU-145 tumor cells or in normal primary AGO1522 fibroblasts were micronucleus (MN) formation, [gamma]-H2AX double strand break repair foci, and survival fraction. A 1.5-2.0-fold increase in MN formation was observed in both DU-145 and AG01522 bystander cells after either alpha particle or xray irradiation of the DU-145 target cells. A 1.5-fold [gamma]-H2AX bystander increase and a survival fraction reduction to 80% were only detected in AGO1522 cells, and only after xray irradiation of target DU-145 cells. Alpha particle irradiation of the target DU-145 cells produced neither [gamma]-H2AX foci nor survival fraction bystander effect in either cell line. Lowering the temperature to 4°C during the irradiation of the DU-145 tumor cells, with either x-rays or alpha particles, eliminated both the MN formation and the decreased survival fraction bystander effects in the co-cultured AG01522 fibroblasts. / (cont.) This study demonstrates that biochemical processes in the directly-irradiated tumor cells are required for initiation of the signaling process. Low temperature during the irradiation inhibited the initiation of a bystander signal. There are also LET-dependent differences in the signal released from DU-145 human prostate carcinoma cells; and that, for some endpoints, bystander AG01522 fibroblasts and bystander DU-145 prostate carcinoma cells respond differently to the same, medium-mediated signal. / by Vered Anzenberg. / Ph.D.

Many types of foods are sterilised and packaged aseptically to maximise their shelf life and ensure that they are safe for consumption. However, if even a few micro-organisms survive these treatments, the quality and/or safety of the food can be seriously compromised. Therefore, packaging materials that can actively participate in the process of inactivating micro-organisms have a potentially important role in protecting the quality and safety of packaged foods. The aim of this project is to explore the effectiveness of the photodynamic effect as a method of inactivating micro-organisms on the surface of packaging materials. Photodynamic action occurs when a photosensitiser molecule absorbs light in the presence of oxygen, leading to the formation of reactive oxygen species such as singlet oxygen, superoxide radicals, or other free radicals; these species are known to inactivate cells. Medical uses of photodynamic action have been studied extensively, usually in applications where the reactive oxygen species are produced intracellularly. However, very little research has been conducted to investigate the efficacy of extra-cellularly generated reactive oxygen species on the viability of micro-organisms, and accordingly this research project investigated the possibility that this approach might be used for inactivating micro-organisms on packaging materials. The results of this study indicate that singlet oxygen may be produced at the surface of polymer films that contain selected photosensitisers, resulting in the oxidation of known singlet-oxygen acceptors to form endoperoxides. This provides evidence that singlet-oxygen mediated reactions can occur at the surface of a sensitising film. It is likely that cell destruction is caused by singlet-oxygen, rather than involving other activated species. It was further shown that the photodynamically generated singlet-oxygen can inactivate micro-organisms (extra-cellularly) on the surface of a polymeric material. The study included examples from each genus of micro-organisms that are of concern to the food and packaging industry, including: Gram-negative bacteria (Escherichia coli); Gram-positive bacteria (Bacillus cereus), both vegetative cells and endospores; yeast (Saccharomyces cerevisiae), and mould (Fusarium oxysporium.) Results indicate that the photodynamic effect causes a substantial reduction in viable cell numbers for vegetative cells and spores (both bacterial and fungal) that have been inoculated onto a plastic surface containing the photosensitiser, anthraquinone,. The results show that an increase in the amount of reactive oxygen species produced by photodynamic action increases the inactivation rate of the micro-organisms. The micro-organisms investigated were susceptible to photodynamic action to varying extents. In conclusion, the results demonstrate that control of microbial populations on the surface of polymeric films (used in food packaging) is achievable using photodynamic action produced from polymers, based on the reported amounts of micro-organisms found on food packaging materials. / Master of Science (Hons)

Understanding energy transfer processes is an essential prerequisite for the deep understanding of all chemical processes. This thesis investigates the process of vibrational relaxation (or deexcitation) of highly vibrationally and electronically excited molecular iodine (I2) induced by very low energy collisions in a supersonic free jet with six foreign gases. In an investigation of the state-to-field relaxation of I2 (B 3II+ou, v = 16) induced by collisions with He at temperatures of 2 to 12 K we find that the absolute relaxation rates are an order of magnitude smaller than those at 300 K and that the explanation of the magnitudes of these rates does not require enhancement due to low energy orbiting resonances. We find that the rates scale well with estimated collision encounter rates that account for the attractive part of the intermolecular potential. A second investigation with a much wider scope explores vibrational relaxation from v = 21 to 24 with six foreign gases: He, Ne, Ar, H2, D2 and N2. For this investigation a new type of experimental procedure has been designed and implemented that records a detailed and complete map of the fluorescence from B3II+ouI2 that is resolved with respect to both fluorescence frequency and time. These not only yield state-to-field rates, but coupled with a novel deconvolution method for growth curve fitting, yield absolute state-to-state rates for vibrational relaxation processes with Av=-1, -2, -3 and -4. The dependence of the relaxation rates on the collision partner, temperature and Av are discussed. An exponential dependence on the vibrational energy gap may be adequate to characterise the Av dependence of vibrational relaxation. The frequency resolution of the experimental data also reveals that some of the energy released by vibrational de-excitation is transferred to the rotation of the I2 molecule. We find this process is best characterised by an exponential dependence on the change of I2 angular momentum and that its extent scales with the mass of the collision partner. Measurements of the low-energy collision-induced quenching of B 3II+ouI2 are also reported for all six foreign gases. The possibility arises from the rates that the mechanism for quenching by H2 and D2 at low temperatures is different to that of the other gases and to that for H2 and D2 at high temperatures.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on December 6, 2007) Vita. Includes bibliographical references.

A xanthene-BODIPY cassette is used as a ratiometric intracellular pH reporter for imaging protein-dye conjugates in living cells. A model was hypothesized to explain the pH-dependent energy transfer efficiencies from the donor to the acceptor based on the electronic chemistry data. Sulfonation conditions were developed for BODIPY dyes to give water-soluble functionalized monosulfonation and disulfonation donors. A water-soluble TBET cassette, which has good photophysical properties, was synthesized using a bissulfonated BODIPY dye as the donor, and their applications for in vitro protein labeling is achieved. Chemoselective cross-coupling reactions were demonstrated for C-S bonds in the BODIPY dye, and similar reactions were applied to make the acceptor of the watersoluble cassette. Chemiluminescent energy transfer cassettes based on fluorescein and Nile Red were synthesized and their spectral properties were studied. Pep-1 (also known as Chariot), R8 (which is not often used as a non-covalent protein carrier), and a new synthesized compound, Azo-R8, was used for the study of non-covalent delivery of four different proteins into mammalian cells. Data from confocal spectroscopy revealed that all three carriers are effective for translocating protein cargos into live cells. At 37 dgrees C, import into endocytic compartments dominates, but at 4 degrees C weak, diffuse fluorescence is observed in the cytosol indicative of a favorable mode of action.

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Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Triplet; rigidly linked polychromophores; intramolecular energy transfer. Includes bibliographical references (p. 83-87).

Thesis (M.S.)--Missouri University of Science and Technology, 2010. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed Jan. 5, 2010). Includes bibliographical references (p. 52-53).

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: molecular electronics; triplet-triplet; singlet-singlet; energy transfer. Includes bibliographical references (p. 88-92).

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