The objective of this study was to examine the effects of two thermal processes, drum-drying and thermoplastic extrusion, on protein quality and digestibility of whole wheat. Coker 916 whole wheat flour was made into a simulated whole wheat spaghetti by extrusion cooking (single screw, 50 psi, 93°C) and a flaked product by drum-drying (152°C). Protein Efficiency Ratios (PER) of the original whole wheat kernels and the two processed wheat products were determined. The apparent digestibility of the four diets was determined from Kjeldahl nitrogen analysis of feces. Amino acid composition, available lysine analysis, colorimetry (Hunter L, a, b color values), and Differential Scanning Calorimetry were also conducted to investigate the effects of thermal processing on protein quality. Both thermal processes significantly increased protein digestibility while PER’s of the drum dried flakes (1.66) and unprocessed whole wheat (1.59) were significantly greater than the extruded product (1.42) Thermal processing also resulted in substantial reductions in lysine (>10%) and several other essential amino acids. Hunter L, a, b values indicated that the drum-dried flakes were lightest in color, followed by the unprocessed whole wheat and the extruded product. The observed decrease in lysine and PER of the extruded product may be due in part to Maillard Browning, as indicated by Hunter color values. It appears that total lysine or Hunter L color values may be reasonable predictors of protein quality of processed whole wheat. DSC results suggest that starch was fully gelatinized during drum-drying of the whole wheat but on partially gelatinized during extrusion cooking. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / Proteasome assembly is a rapid and highly sequential process that occurs through a series of intermediates. While the quest to understand the exact process of assembly is ongoing, there remains an incomplete understanding of what happens early on during the process, prior to the involvement of the β subunits. A significant feature of proteasome assembly is the property of proteasomal subunits to self-assemble. While archaeal α and β subunits from Thermoplasma acidophilum can assemble into entire 20S units in vitro, certain α subunits from divergent species have a property to self-assemble into single and double heptameric rings. In this study, we have shown that recombinant α subunits from Methanococcus maripaludis also have a tendency to self-assemble into higher order structures when expressed in E. coli. Using a novel cross-linking strategy, we were able to establish that these higher order structures were double α rings that are structurally similar to a half-proteasome (i.e. an α-β ring pair). Our experiments on M. maripaludis α subunits represent the first biochemical evidence for the orientation of rings in an α ring dimer. We also investigated self-assembly of α subunits in S. cerevisiae and attempted to characterize a highly stable and unique high molecular weight complex (HMWC) that is formed upon co-expression of α5, α6, α7 and α1 in E. coli. Using our cross-linking strategy, we were able to show that this complex is a double α ring in which, at the least, one α1 subunit is positioned across itself. We were also able to detect α1-α1 crosslinks in high molecular weight complexes that are formed when α7 and α1 are co-expressed, and when α6, α7 and α1 are co-expressed in E. coli. The fact that we able to observe α1-α1 crosslinks in higher order structures that form whenever α7 and α1 were present suggests that α1-α1 crosslinks might be able to serve as potential trackers to detect HMWCs in vivo. This would be an important step in determining if these HMWCs represent bona fide assembly intermediates, or dead-end complexes whose formation must be prevented in order to ensure efficient proteasome assembly.