Berlin, Freie Universiẗat, Diss., 2000. / Dateiformat: zip, Dateien im PDF-Format.

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Myoglobin (Mb) is a well characterized hemeprotein found in skeletal muscle. The dimethylester heme-substituted derivative of equine Mb (DME-Mb) was prepared to evaluate the involvement of the heme propionate groups in the electron transfer reactions of Mb. To achieve this goal, an efficient procedure to reconstitute and purify DME-Mb in high yield was developed. The near UV-visible absorption spectra of DME-Mb in various states of ligation and oxidation did not change significantly relative to those of native Mb. The ¹H NMR spectra obtained for native metMb (heme Fe(III) oxidation state) and metDME-Mb showed differences in the electromagnetic environment of their respective heme groups. The reactivity of DME-Mb was different from that of native Mb. For example the water ligand of metDME-Mb (Fe-H₂O) has a lower pKa than that of native metMb as determined by spectroscopic pH titrations. The autoxidation rate of oxyDME-Mb (Fe(II)-O₂) is faster than that of native oxyMb. MetDME-Mb apparently has a binding affinity for ferricyanide not evident in native metMb. Compared to native Mb, DME-Mb has decreased susceptibility to the oxidant hydrogen peroxide. The oxidation-reduction equilibrium of DME-Mb has been studied under a variety of solution conditions. At standard conditions (pH 7, I=0.1 M and 25°C) the midpoint reduction potential (Em) of DME-Mb is 100.0(2) mV vs. SHE, which is 39 mV higher than the Em of native Mb. Analysis of the pH dependence of Em showed differences in the identity or pKa between titratable groups found in native and DME-Mb. The ionic strength dependence of Em showed a higher net positive charge estimate for DME-Mb than native Mb consistent with the nature of the chemical modification involved. The temperature dependence of Em showed that DME-Mb has a greater difference in stability between oxidation states than native Mb. The kinetics of metDME-Mb reduction by Fe(EDTA)²⁻were also studied under a variety of conditions. At standard conditions, metDME-Mb reacted with the reductant Fe(EDTA)²⁻ at a second order rate constant (k₁₂) two orders of magnitude greater than that of native metMb. After correcting for the differences in reduction potential between reactants, metDME-Mb still reacted at a significantly faster rate than native metMb, indicating differences in their reaction mechanisms. The pH, temperature and ionic strength dependences of k₁₂ for DME-Mb and Fe(EDTA)²⁻ showed that DME-Mb had electrostatic and thermodynamic properties significantly different from that of native Mb. The functional differences between DME-Mb and native Mb can be attributed to the structural and electrostatics properties of the heme propionate groups. The interactions of these groups within the surrounding protein and the external environment are discussed with reference to the structure of Mb available from x-ray crystallographic studies. As a result, it is concluded that the heme propionate groups are involved in the structural stability, electron transfer specificity and reactivity of Mb. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

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This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

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Consumers associate meat color with quality. In some cases, especially in fresh and cured hams, the surface of a ham, whole, boneless or sectioned and formed displays a color gradient, which is unsightly and generally is considered of lower quality and must be discounted or processed different where color is less critical to the ultimate value of the resulting product. This disparity in color uniformity across fresh and cured products is sometimes known as two-toning and is most often found in the semimembranosus (SM) and associated muscles of fresh hams and is exacerbated with curing. The underlying color of fresh meat may be a function of postmortem metabolism or the underlying characteristics of those muscles involved. Therefore, the objective of this study is to determine the changes in underlying muscle type and postmortem metabolism in those muscles responsible for fresh ham color variation. Semimembranosus (SM) muscles of 15 mixed bred pigs were collected at 30 min and 1440 min postmortem, and muscle color was determined and muscles were collected and snap frozen for various energy metabolism analyses. Differences in color (L*, a* and b*) were noted across the face of the muscle by zone and time (P < 0.0001) but no differences were detected in pH and lactate, glucose, glucose-6-phosphate, and glycogen metabolisms. Glycolytic potential was also measured on a lactate basis and showed no differences across zone (P = 0.0746) but increased over time (P < 0.006). Lactate and pH were plotted and showed a linear relationship linear relationship (R2 = 0.928337) at 30 min (P < 0.0001) and at 1440 min (R2 = 0.161412; P < 0.0015). Muscle type characteristics showed no difference between zones and time. Buffering capacity showed a significant difference at pH 6 (P < 0.0359) and with time across all pH measured (P < 0.0001). These data suggest inherent differences, such as location and function, in the semimembranosus muscle may be more critical in developing fresh color than aberrations in postmortem metabolism. / Master of Science

by Poon Hoi To. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1981. / Bibliography: leaves 40-41.

The £\-helix structure of protein is very similar to the cylindrical structure. Especially, the Sperm-Whale Myoglobin molecules has 70% £\-helix structure. Therefore, we use simulated annealing method to solve ¡§X-ray phase problem¡¨, and apply Metropolis algorithm to avoid local minimum. We hope that the new method can build £\-helix structure of Sperm-Whale Myoglobin molecule. Therefore, we use multi cylinders as the Myoglobin¡¦s tertiary structure and solve the cylinder¡¦s structure with the simulated annealing method.

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