Includes bibliographical references (p. 123-136).

Heidelberg, University, Diss., 2003.

München, Techn. University, Diss., 2004.

Hannover, Universiẗat, Diss., 2000.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Not available / text

Thesis (Ph.D.) - University of Glasgow, 1987. / Includes bibliographical references. Print version also available.

This dissertation aimed to explore the S2 region with an attempt to modulate its elasticity in order to tune the contraction output. Two peptides, the stabilizer and destabilizer, showed high potential in modifying the S2 region at the cellular level, thus they were prepared for animal model testing. In this research, (i) S2 elasticity was studied, and the stabilizer and destabilizer peptides were built to tune contraction output through modulating S2 flexibility; (ii) the peptides were attached to heart homing adducts and the bond between them was confirmed; and (iii) it was shown that minor changes were imposed on the modulating peptides' functionality upon attaching to the heart homing adducts. S2 flexibility was confirmed through comparing it to other parts of myosin using simulated force spectroscopy. Modulatory peptides were built and computationally tested for their efficacy through interaction energy measurement, simulated force spectroscopy and molecular dynamics; these were attached to heart homing adducts for heart delivery. Interaction energy tests determined that tannic acid (TA) served well for this purpose. The stoichiometry of the bond between the TA and the modulating peptides was confirmed using mass spectroscopy. The functionality of the modulating peptides was shown to be unaltered through expansion microscopy where they located to the same position on the sarcomere with and without TA. They were also shown to cause the sarcomeres to contract similarly with and without the TA in contractility assay. Taken together, this work prepared the modulating peptides for animal model tests by attaching them to tannic acid.

No description available.

Proteolytic degradation of fish flesh occurring at elevated temperatures is the primary limitation for the commercial utilization of arrowtooth flounder (ATF). Characterization of the autolytic activity of ATF muscle incubated at various pHs and temperatures indicated the involvement of heat-activated proteinases active at acidic and alkaline pHs. Further characterization of the proteinase extract from fish muscle indicated the proteinase was more active at acidic pH than at alkaline pH in hydrolysis of Z-Phe-Arg-NMec and all types of protein substrates tested. Based on molecular weight and hydrolytic properties, activity peak separated on size exclusion chromatography, or activity bands observed on activity-stained substrate gels were presumed to be cathepsin L or like. A muscle proteinase showing similar hydrolytic properties to a proteinase extract was purified to electrophoretic homogeneity and subsequently confirmed by kinetic studies to be cathepsin L. Therefore, the results clearly indicated that cathepsin L is primarily responsible for autolytic activity of ATF muscle and surimi at the elevated temperatures. Gelation of fish myofibrillar proteins, mainly myosin, is an important process for surimi production. Elucidation of the gelation mechanism and the effect of proteolysis on myosin provide information regarding protein interactions that improve ATF product quality. Heat-induced changes in physicochemical properties of myosin, free of endogenous proteinases, indicated myosin gelation consisted of two processes, denaturation and aggregation. ATF myosin was shown to be extremely sensitive to heat, resulting in denaturation at a lower temperature than other fish myosins. Denaturation began at 25°C and was initiated by the unfolding of the α-helical region. Following denaturation was the exposure of the hydrophobic and sulfhydryl residues, which were subsequently involved in aggregation and the gelation process. Changes in dynamic properties indicated ATF myosin formed a gel in three different stages, as shown by the first increase in gel rigidity at 28°C, followed by a decrease at 35°C and a second increase at 42°C. A model system using ATF myosin and papain was developed to investigate how proteolysis affects the heat-induced gelation of fish myosin. The addition of papain decreased the onset temperature and the rate at which G' developed during heating. DSC thermograms indicated papain significantly decreased the enthalpy required to induce myosin denaturation with no significant changes in the onset or the maximum temperature. Thermal denaturation kinetics indicated a decrease in both the activation energy of the denaturation process and the denaturation rate of myosin. Although myosin gels could be formed, structural disruption caused by proteolysis, i.e., reduction in molecular size and loss in structural domain, resulted in lowering of the gelling ability of myosin and rigidity of the formed gels. / Graduation date: 2000