Inaug.-diss.--Tübingen. / Vita. "Literaturverzeichniss": p. 28.

Inaug.-diss.--Tübingen. / Vita. "Literaturverzeichniss": p. 28.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1928. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

This work was devoted to the study of (a) the physico-chemical, functional, and structural properties of bean (Phaseolus sp.) protein isolates in relation to their microstructures, and (b) the effects of protein carbohydrate interactions on physico-chemical, functional, and structural properties. The contents of protein, and both total and individual sugars of alkali extracted (amorphous) and citric acid extracted (bipyramidal and spheroidal) proteins from Phaseolus vulgaris (white kidney and navy) and Phaseolus lutanus (baby lima and large lima) beans were determined. The proteins were subjected to differential scanning calorimetry, and measurements of surface tension (air-water interface), surface hydrophobicity, and foam expansion. Structural analysis of the proteins were performed using Fourier transform infrared (FT-IR) spectroscopy. Enzymatic and chemical deglycosylation was performed on a white kidney bean protein isolate. / Glucose and mannose were the major sugars found in the isolates. Bipyramidal and spheroidal microstructures with higher protein contents generally had greater mannose content and lower glucose content. Differences in enthalpy of denaturation $( Delta$H), surface tension decay curves, surface hydrophobicities, and foam expansions were observed with isolates of different microstructures. Corresponding differences in molecular structure were not, however, detected by FT-IR spectroscopy. Using statistical analysis, a relationship between foam expansion and the $ Delta$H, solubility, surface hydrophobicity and surface tension of the isolates was obtained. Preliminary results suggest that the removal of carbohydrate influenced the physico-chemical properties of the protein.

No description available.

The structure of cytochrome c₅₅₅ from the green sulfur bacterium Chlorobium thiosulfatophilum was determined by using a single isomorphous derivative, K₂HgI₄, in combination with its anomalous signal. The initial 2.25 angstrom map was modified by the technique of Fourier inversion. The smoothing function for the electron density map addressed three different features in the map, the solvent density, the protein density and the volume surrounding the heavy atom binding sites known to contain spurious peaks. This structure determination was undertaken for three reasons. First, Chlorobium thiosulfatophilum is a very primitive sulfur metabolizing bacterium and so its cytochrome c₅₅₅ structure is important for its evolutionary implications. Second, the oxidation-reduction potential of cytochrome c₅₅₅ is significantly different from the oxidation-reduction potential of other cytochromes whose structures have been determined. Comparisons with the other structures would provide information concerning the factors that are important in regulating oxidation-reduction potentials. Finally, the three dimensional structure may aid in explaining the pattern of reactivity cytochrome c₅₅₅ displays with mitochondrial cytochrome c oxidase and reductase, which is reversed when compared to other bacterial c-type cytochromes. The resulting structure contains three alpha helices. These features are consistent with other c-type cytochrome molecules previously determined. Two regions of the map appear to be disordered and are difficult to interpret. Possible causes of this observation are discussed and related to the significance of the structure.

X-ray crystallography is a popular method for resolving protein structures. Protein crystals need to be used for X-ray crystallography, but most naturally occurring proteins do not readily crystallize. The Hunt lab performed computational analyses showing that arginine is the most overrepresented amino acid in crystal-packing interfaces in the Protein Data Bank. Given the similar physicochemical characteristics of arginine and lysine, we hypothesized that multiple lysine-to-arginine (KR) substitutions should improve crystallization. To test this hypothesis, we developed software that ranks lysine sites in a target protein based on the redundancy-corrected KR substitution frequency in homologs. We demonstrate that three unrelated single-domain proteins can tolerate 5-11 KR substitutions with at most minor destabilization and that these substitutions consistently enhance crystallization propensity. This approach rapidly produced a 1.9 Å crystal structure of a human protein domain refractory to crystallization with its native sequence. Structures from bulk-KR-substituted domains show the engineered arginine residues frequently make high-quality hydrogen-bonds across crystal-packing interfaces. We thus demonstrate that bulk KR substitution represents a rational and efficient method for probabilistic engineering of protein surface properties to improve protein crystallization. This stands in direct contrast to earlier work and dogmas that posited that surface entropy reduction was the clear path forward to crystallzing proteins. Arginine is a high-entropy sidechain, yet it helps drive protein crystallization. To understand which structure and dynamical features of arginine give rise to crystal packing propensity, we performed 60 Molecular Dynamics (MD) simulations to measure the sidechain order parameter of arginine and compare it against crystal packing propensity. This work found that surface-exposed arginines with low order parameters are most likely to participate in crystal packing interactions. This is evidence against earlier thinking that high entropy surface sidechains oppose crystallization. Entropic barriers to protein crystallization can be enthalpically overcome.