Suspensions of pancreatic islet cells from ob/ob-mice were incubated with Trypan Blue. Microscope photometry showed that apparently viable cells excluded the dye completely, whereas the nuclei of non-viable cells accumulated Trypan Blue by a saturable process. Alloxan rapidly increased the permeability of the plasma membrane in mouse 3-cells; the exclusion of Trypan Blue is a valid and useful measure of islet cell viability following alloxan exposure. The diabetogenic action of alloxan may be mediated by hydroxyl radicals. In several biological systems hydroxyl radicals are formed by an iron-catalyzed reaction between superoxide anion radicals and hydrogen peroxide. To test whether this applies to alloxan diabetogenicity, the effects of superoxide dismutase, catalase, scavengers of hydroxyl radicals, and metal ion chelators were tested (a) in a cell-free radical-generating system and (b) on islets and islet-cells exposed to alloxan In vitro. The effect of longtime-circulating superoxide dismutase injected prior to alloxan was tested on mice in vivo. Luminol chemiluminescence was used to monitor alloxan-dependent radical production. Accumulation of 8^Rb+ and exclusion of Trypan Blue were used as cell viability criteria in isolated mouse islets and islet-cells. Blood glucose was determined to monitor the development of diabetes in living animals. Superoxide dismutase, catalase, scavengers of hydroxyl radicals, and metal ion chelators inhibited the alloxan-dependent chemiluminescence and decreased the toxic effects on Rb+ accumulation or Trypan Blue exclusion in islets and islet-cells. Superoxide dismutase, linked to polyethylene glycol and injected 12 hours before alloxan, largely prevented the development of alloxan diabetes. Alloxan toxicity _in vitro and in vivo seems to depend on the formation of superoxide radicals and hydrogen peroxide which in turn form the noxious hydroxyl radical via an iron-catalyzed Haber-Weiss reaction. As free radicals and hydrogen peroxide can be formed by other chemicals and during inflammation, and inflammation may accompany the outbreak of human diabetes, studies on the beneficiary effects of superoxide dismutase and other scavengers of free radicals in other forms of diabetes seem warranted. / <p>S. 1-38: sammanfattning, s. 39-74: Härtill 6 uppsatser</p> / digitalisering@umu

A mutation (CTG to TTG) of FeSOD gene was found in Escherichia coli. Since they both encode leucine, it is a silent mutation. Site-­‐directed mutagenesis was applied to correct the mutation, and the mutant FeSOD (before gene correction) and wild type FeSOD (after gene correction) were purified. The FeSODs from the two genes were Characterized using different assays and spectroscopic methods including EPR and CD. The requirement for the rare codon TTG may result in slowed translation and heavy demand on a scarce tRNA. Cultures expressing wild type FeSOD are better able to grow for long times after addition of IPTG and more mature to incorporate Fe atoms to the active sites than are cultures expressing the mutant gene. Moreover, the wild type FeSOD has more activity than the mutant. To our knowledge, this is the first time that a silent mutation has been demonstrated to affect metal incorporation into a metalloenzyme.

Amyotrophic lateral sclerosis (ALS) is a devastating and progressive disease that results in selective death of motor neurons in the cortex, brain stem and spinal cord. ALS is the most common adult onset motor neuron disease resulting in paralysis and death, commonly within 2 – 5 years of symptom onset, yet there remains no effective treatment for the disease. The majority of ALS cases show no hereditary link (referred to as sporadic ALS or sALS); however, ~10% of cases show a dominant pattern of inheritance (referred to as familial ALS or fALS). Over 170 different mutations in human Cu, Zn superoxide dismutase (SOD1) have been identified to account for ~20% of fALS. SOD1 is a ubiquitously expressed homodimeric antioxidant enzyme. It is widely accepted that mutations in SOD1 result in a gain of toxic function, rather than a loss of native function. A prominent hypothesis for the gain of function is the formation of protein aggregates, which have been shown to be toxic to motor neurons. Protein aggregation is observed in a number of neurodegenerative disorders, including Alzheimer’s, Huntington’s and Parkinson’s disease. Each β-rich monomer of SOD1 binds one catalytic Cu ion and one structural Zn ion. The metallation state of SOD1 significantly influences the structure, dynamics, activity, stability, and aggregation propensity. A similar trend has been observed in a number of metalloenzymes and as such a method to rapidly and accurately quantitate metal ions in proteins is of great importance. Here a review of previous methods using the chromogenic chelator PAR to quantitate metal ions in proteins is presented. Three methods are assessed for their accuracy, precision and ease of use. The methods vary in accuracy, which is highest only under the specific conditions it was designed for. A robust new method is presented here that uses spectral decomposition software to accurately resolve the absorption bands of Cu and Zn with high precision. This method may be successful as a more general method for metal analysis of proteins allowing for the quantitation of additional metal combinations (e.g. Zn/Co, Ni/Cu, Ni/Co). Thermodynamic stability has widely been implicated as playing a major role in the aggregation of globular proteins. Metal loss significantly decreases the global stability of SOD1 and as such metal-depleted (apo) forms of SOD1 have largely been the focus of SOD1 investigations. Recent studies, however, suggest that complete global unfolding is not required for protein aggregation. Local unfolding has been investigated and proposed to be sufficient to induce irreversible protein aggregation in the absence of global destabilization. Enhanced local unfolding has been observed in a number of disease-related proteins. Since SOD1 aggregation may occur from partially unfolded forms, NMR temperature dependence studies have been carried out on the most abundant form of SOD1 in vivo, the fully metallated (holo) dimer, to provide a residue specific picture of subglobal structural changes in SOD1 upon heating. Amide proton (N1H) temperature coefficients report on the hydrogen bonding status of a protein. A curved N1H temperature dependence indicates that the proton populates an alternative conformation generally within 5 kcal/mol of the ground state. NMR temperature dependence studies of pseudoWT indicate that the thermal unfolding process of holo pWT begins with “fraying” of the structure at its periphery. In particular, increased disorder is observed in edge strands β5 and β6, as well as surrounding the zinc binding site. The local stability and conformational heterogeneity of ALS-associated mutants G93A, E100G and V148I was also assessed. All mutants display similar local unfolding patterns to pseudoWT, but also show distinct differences in the hydrogen bonding network surrounding the mutation site. Interestingly, each mutation regardless of its structural context results in altered dynamics at the β-barrel plug, a key stabilizing element in SOD1. A significant proportion of residues (~30%) access alternative states in both pseudoWT and mutants, however, overall mutants appear to be able to access higher free energy alternative states compared to pseudoWT. The implications of these results for the mechanism of protein aggregation and disease are discussed.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 171-189).

Thesis (Ph.D. in Clinical Science) -- University of Colorado at Denver and Health Sciences Center, 2006. / Typescript. Includes bibliographical references (leaves 107-128). Free to UCDHSC affiliates. Online version available via ProQuest Digital Dissertations;

Diss. (sammanfattning). Umeå : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Umeå : Umeå universitet, 2005. / Härtill 6 uppsatser.

Diss. (sammanfattning) Umeå : Univ., 2007. / Härtill 4 uppsatser.

Thèse (M.Sc)--Université Laval, 2008. / Bibliogr.: f. 75-85. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.