No description available.

Thesis (Ph. D.)--Cornell University, 1912. / "Reprinted from the Journal of physical chemistry, vol. 16."

Thesis (Ph. D.) -- California Institute of Technology, 2010. / Title from home page (viewed 05/10/10). Advisor and committee chair names found in the thesis' metadata record in the digital repository. Includes bibliographical references.

Thesis (Ph. D.)--University of Notre Dame, 1941. / Cover title. Bibliography: p. 19-20.

[No abstract available] / Science, Faculty of / Chemistry, Department of / Graduate

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 179-233). Available also in a digital version from Dissertation Abstracts.

The Gram-positive bacterium, Rhodococcus sp. 33, was selected for further study to identify the characteristics conferring it with high tolerance to concentrations of benzene. Since most organic solvents, like benzene, are lipophilic, they tend to accumulate within lipid membranes where they express toxicity. The mechanisms conferring this Rhodococcus with resistance to benzene were hypothesised to be located within the subcellular region of this bacterium - cell wall, membrane, and cell-bound polymer. Therefore, this investigation was instigated to identify these mechanisms. To accomplish this, the development of methodologies to isolate highly purified cell wall and membrane fractions, from the organism, were required. To corroborate this investigation, a total of 6 benzene-sensitive mutants were prepared from Rhodococcus sp. 33 and their characteristics compared to those of the parent wild-type strain. 1-D PAGE analysis of proteins revealed various benzene-induced wall, membrane, and cytoplasmic proteins in the w-t. A protein band, with an approximate molecular weight of 58 kDa, was identified to be absent in the most sensitive mutant isolated (mutant M2b). Interestingly, much of this research showed that the benzene-catabolising enzymes played an insignificant role in tolerating the benzene. Gas chromatography and mass spectrometry of whole cell-derived fatty acids revealed that benzene induced an increase in the ratios of saturated/unsaturated fatty acids. Moreover, protein determinations revealed that benzene induced an increase in the concentration of total membrane protein. These increases are suggestive as possible mechanisms to decrease the fluidity of the cell membrane. This was further supported by the observed increase in the generalised polarisation (GP) of laurdan fluorescence in the membranes during growth of the organism with benzene, which is correlated with a decrease in membrane fluidity. The organism was also found to synthesise hexadecenoic acid, 16:1w6c (11 - 13% of total fatty acids), an uncommon fatty acid and previously unreported in other Rhodococcus spp. Analysis of the organism's cell-bound extracellular polymer revealed it to be composed of polysaccharide with biosurfactant-like properties. Its function is proposed to act as a surfactant layer outside the cell, concentrating the benzene within its matrix and reducing benzene's contact with the cell membrane.

No description available.

The Gram-positive bacterium, Rhodococcus sp. 33, was selected for further study to identify the characteristics conferring it with high tolerance to concentrations of benzene. Since most organic solvents, like benzene, are lipophilic, they tend to accumulate within lipid membranes where they express toxicity. The mechanisms conferring this Rhodococcus with resistance to benzene were hypothesised to be located within the subcellular region of this bacterium - cell wall, membrane, and cell-bound polymer. Therefore, this investigation was instigated to identify these mechanisms. To accomplish this, the development of methodologies to isolate highly purified cell wall and membrane fractions, from the organism, were required. To corroborate this investigation, a total of 6 benzene-sensitive mutants were prepared from Rhodococcus sp. 33 and their characteristics compared to those of the parent wild-type strain. 1-D PAGE analysis of proteins revealed various benzene-induced wall, membrane, and cytoplasmic proteins in the w-t. A protein band, with an approximate molecular weight of 58 kDa, was identified to be absent in the most sensitive mutant isolated (mutant M2b). Interestingly, much of this research showed that the benzene-catabolising enzymes played an insignificant role in tolerating the benzene. Gas chromatography and mass spectrometry of whole cell-derived fatty acids revealed that benzene induced an increase in the ratios of saturated/unsaturated fatty acids. Moreover, protein determinations revealed that benzene induced an increase in the concentration of total membrane protein. These increases are suggestive as possible mechanisms to decrease the fluidity of the cell membrane. This was further supported by the observed increase in the generalised polarisation (GP) of laurdan fluorescence in the membranes during growth of the organism with benzene, which is correlated with a decrease in membrane fluidity. The organism was also found to synthesise hexadecenoic acid, 16:1w6c (11 - 13% of total fatty acids), an uncommon fatty acid and previously unreported in other Rhodococcus spp. Analysis of the organism's cell-bound extracellular polymer revealed it to be composed of polysaccharide with biosurfactant-like properties. Its function is proposed to act as a surfactant layer outside the cell, concentrating the benzene within its matrix and reducing benzene's contact with the cell membrane.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1986. / Includes bibliographical references (leaves 104-107).