Doctor of Philosophy (PhD), Ohio University, 1994, Chemical Engineering (Engineering)

The goal of this work is to develop a downstream process for the purification of human growth hormone (hGH) and an hGH antagonist, named hGHG120R, from cultured recombinant mouse L cells grown in the presence of 3% – 5% Nu-Serum IV. The process we developed, capable of handling 10-15 liters of culture medium for each individual run, consists of centrifugation for removal of the culture medium, salt precipitation for reducing the medium volume, membrane ultrafiltration, size exclusion chromatography for purification, and a reversed phase high performance liquid chromatography (RP- HPLC) column with high resolution for final purification. Phase separation and buffer exchange are used to remove organic solvents. Then an ultrafiltration step is added to remove pyrogen. The last step is lyophilization. The products of hGH and hGHG120R produced by the process retain biological activity and can be pyrogen-free. In the process development, HPLC analytical methods are set up for evaluation and quality-control of the intermediate and finished products. A reasonable cost estimation for the downstream process is made based on the material cost, the labor cost, and equipment wear. As a key purification step, RP-HPLC gradient elution is studied using a general rate model. A small analytical column is used to obtain a retention correlation and adsorption saturation capacity. Mass transfer parameters are estimated from empirical correlations in the literature. These data are used in the model to predict gradient elution profiles on the small column. For retention times of hGH and hGHG120R, simulated results are found to be in very good agreement with experimental results, with an average absolute relative error of 3% for retention time. Using the retention correlation and the adsorption saturation capacity from the small column, scale-up predictions of chromatograms at different gradient times, flow rates, and sample sizes on a larger preparative RP-HPLC column are made. Compared w (open full item for complete abstract)

Committee: Tingyue Gu (Advisor) Subjects: Engineering, Chemical

MS, Kent State University, 2009, College of Arts and Sciences / Department of Chemistry

Aerosol particles (APs) affect the Earth's energy balance directly by absorbing and scattering radiation, and indirectly by altering the reflectance and persistence of clouds. Both parameters are determined by the chemical composition, size and shape of APs. APs consist of complex organic and inorganic mixtures, which include black carbon/soot as well secondary organic matter (SOM) proceeding from the gas-phase. SOM, also known as humic-like substances (HULIS), plays a key role in determining the optical properties of APs due to its ability to absorb radiation in the visible region of the solar spectrum. The chemical characterization of SOM is a daunting task that involves comprehensive chemical analysis, largely via chromatography/high-resolution mass spectrometry (HRMS), one of the most powerful analytical techniques available. However, optical properties are associated with chromophores within specific chemical structures, rather than with molecular formulas. Simpler mixtures can mimic the optical properties of secondary organic aerosol (SOA). Optical properties of mixtures are not linear combinations of the optical properties of its components. Furthermore, optical properties are not intrinsic to APs, but depend on external parameters, such as insolation and relative humidity. Therefore full speciation is neither a necessary nor sufficient condition for characterizing the optical properties of SOA.

Committee: Shan-Hu Lee Prof (Advisor); Michael Hoffmann Prof (Other); Mietek Jaroniec Prof (Committee Member); Alexander Seed Prof (Committee Member) Subjects: Atmosphere; Chemistry