This research was conducted to study the effects of supplemental L-Methionine (L-Met) and DL-Methionine (DL-Met) on nutrient metabolism, muscle gene expression, and growth performance of pigs. Twenty crossbred young barrows (initial Body Weight (BW) 21.2 ± 2.7 kg) were randomly assigned to 2 treatments. Crystalline L-Met and DL- Met were supplemented to the diets in Treatment 1 and 2 (both at 0.13%, ased basis), respectively. After 4 weeks of an ad libitum feeding trial, BW and feed intake were measured to calculate Average Daily Gain, Average Daily Feed Intake, and Gain: Feed. The blood samples were collected from the jugular vein for analyses of plasma AA and metabolite concentrations. The longissimus dorsi muscle samples were collected for analysis of myogenesis gene expression. The findings from this study (from gene expression to animal growth performance) suggest that the bioefficacy of L-Met is the same as for DL-Met, indicating the highly efficient conversion of D-Met to L-Met in young growing barrows.

L-Methionine (L-Met) is a new product that supplies the biologically active form of methionine. Therefore, the objective of this study was to elucidate the benefits of dietary L-Met supplementation relative to the industry standard DL-Met. Sixteen gilts with an initial BW 81.2±7.93 kg were individually penned and randomly allotted to one of two equivalent dietary treatments for 37 days in 2 trials (8 pigs/trial): DL-Met (0.050% of diet) or L-Met (0.052% of diet). Body weight and feed intake were measured on days 0, 19, and 37 to calculate performance measures. Pigs were harvested and carcasses assessed on day 38. Liver, loin muscle, and subcutaneous fat were collected for antioxidant assessments. Data were analyzed via Proc Mixed in SAS and significance was set at P ≤ 0.05. There were no differences between dietary treatments in growth performance, carcass characteristics, or antioxidant status (P > 0.05). In conclusion, methionine form did not differentially impact animal growth or antioxidant status.

L to D isomerization of amino acids in a commercially prepared alkali-treated food-grade soy isolate was investigated. A soy flour product was also investigated as a control which had not been alkali treated. Methionine and valine collected from two soy flour and two soy isolate samples were coupled with L-leucine-N-carboxyanhydride. If both D- and L-forms were present this would produce diastereomeric dipeptide derivatives. The derivatives were separated by ion-exchange chromatography using a TSM Amino Acid Analyzer. Comparison of the sample methionine and valine dipeptide peaks to standard dipeptide peaks revealed the presence of L-valine, L-methionine and D-methionine in both soy flour and soy isolate samples. Methionine was substantially isomerized in both products. D-valine was not observed in either soy flour or soy isolate samples. Thus, isomerization of methionine appeared to occur at a faster rate than valine. Acid hydrolysis, toasting of soy meal, and alkaline treatment are all conditions which may be responsible for the isomerization of methionine. / Master of Science

published_or_final_version / abstract / Microbiology / Master / Master of Philosophy

A series of 6-endo-(methylthio)-bicyclo[2.2.1]heptane-2-endo-proline amides was synthesized to study the neighboring proline amide participation in electron transfer from thioethers. The thioether with endo-pyrrolidine amide formed a two-center three-electron SO bond after one electron oxidation and the oxidation potential of the thioether was lowered by 530 mV and 330 mV compared to the corresponding exo-pyrrolidine amide and the primary amide analogues, respectively. The thioether with a proline methyl ester showed the oxidation potential of 410 mV higher than that of the pyrrolidine amide. The basis for this surprising result was revealed by an X-ray crystallographic structure study of the diastereomerically pure proline methyl ester which showed amide carbonyl n → methyl ester π* interaction which removes electron density from the neighboring amide which results in less effective neighboring amide participation in thioether oxidation. This accounts for the electrochemical result. A potent synthetic route for S-tert-butyl m-terphenyl thioethers was developed and a series of such thioethers was synthesized. Electrochemical studies showed through-space S∙∙∙π interaction with lower oxidation potentials for thioethers with more electron rich aromatic groups and higher oxidation potentials with electron withdrawing aromatic groups. Selective Suzuki reactions were discovered in which mono-coupling of the precursor dibromides could be achieved. A second coupling was then possible in which two different aromatic rings are attached to the central aryl thioether ring. This enabled the synthesis of a two-sulfur three-aromatic ring extended m-terphenyl thioether as a potential electron conductor. In support of this possibility this compound showed an oxidation potential of +0.99 V which is less positive than the +1.09 V measured for the mono-sulfur analog.

The effects of dietary methionine (Met) on the utilization of selenium (Se) from stored tissue Se and dietary selenomethionine (SeMet) for glutathione peroxidase (GSH-Px) synthesis were studied in male rats. Plasma, liver and muscle Se significantly increased when rats were fed 0.5 mg Se/kg diet as SeMet in a Met-deficient diet for 21 d, whereas tissue GSH-Px activities decreased 43-50% during the SeMet supplementation period, suggesting that Se is deposited as SeMet in general body proteins. By calculation, a significant lower percentage of Se was associated with GSH-Px in Met-deficient as compared to Met-supplemented rats. Dietary Met supplementation increased the incorporation of 75Se from 75SeMet into specific rat selenoproteins in addition to liver GSH-Px. Overall, these results suggest that intact SeMet is preferentially incorporated non-specifically into general body proteins in Met-deficient rats, whereas with supplemental Met, more SeMet is degraded and the released Se used for specific selenoprotein synthesis. (Abstract shortened with permission of author.)

No description available.

Thesis advisor: Clare O'Connor / As organisms get older, the proteins in their cells also age, and as this happens, the amino acids that make up these proteins may become chemically modified and begin to lose their integrity. One example of an age-related modification occurs when the amino acid residue methionine is oxidized by a reactive oxygen species to methionine sulfoxide. Methionine sulfoxide reductase is an enzyme that repairs this damage to the protein by catalyzing a reaction that reduces methionine sulfoxide back to methionine. The fission yeast Schizosachharomyces pombe was used as the experimental model to study methionine sulfoxide reductase in vivo, taking advantage of the variety of tools available with which to study the organism. In S. pombe there are two genes encoding methionine reductase activities, msrA and msrB. The first goal of this project was to construct yeast strains in which the endogenous msrA and msrB genes had been inactivated. This was accomplished via homologous recombination reactions in which the msr genes were replaced with a selectable marker for biosynthesis of uracil (ura4+). After the construction and verification of the two knockout strains, the sensitivities of the strains to reactive oxygen species were tested. Both strains showed reduced resistance to oxidative stress. Future experiments will include more detailed analyses of the abilities of the strains to survive oxidative stress. Finally, the two knockout strains of yeast will be mated with one another in order to produce a double msr knockout, in order to examine the effects of a complete lack of methionine sulfoxide reductase activity on the organism. / Thesis (BS) — Boston College, 2005. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Biology. / Discipline: College Honors Program.

The detrimental effects of oxidative stress caused by the accumulation of Reactive Oxygen Species (ROS) have been acknowledged as major factors in aging, senescence and several neurodegenerative diseases and conditions such as Parkinson’s disease and stroke (ischemia/reperfusion). Mammalian models are extremely susceptible to these stresses that follow the restoration of oxygen after anoxia; however, some organisms including the freshwater turtle Trachemys scripta can withstand several bouts of anoxia and repeated reoxygenation without any apparent pathology. T. scripta thus provides us with an alternate vertebrate model in which we can investigate physiological mechanisms of neuroprotection without the damaging effects that come with oxidative stress. The major objective of this study was to investigate the protective mechanisms in the turtle brain under conditions of anoxia and oxidative stress. Specifically, the focus is on the Methionine Sulfoxide Reductase system (Msr), an antioxidant and cellular repair system, and how it is regulated to protect the brain against such stressors. Previous studies in my lab have demonstrated that Msr mRNA and protein levels are differentially upregulated during anoxia and reoxygenation. To investigate the regulation of Msr, FOXO3a was directly induced by transfecting a human FOXO3a plasmid into turtle brain cell cultures, as FOXO3a has been shown to regulate MsrA levels in other animal models. Pharmacological manipulation of FOXO3a was also performed using the green tea extract Epigallocatechin gallate (EGCG) as it has been shown to increase expression of FOXO3a during oxidative stress conditions in other models. I found that an induction of human FOXO3a increased FOXO3a levels and showed protection against cell death during oxidative stress. Furthermore, treatment of cells with EGCG increased expression of FOXO3a only when the cells were exposed to oxidative stress and decreased cell death. Induction of FOXO3a and EGCG treatment did not increase MsrA levels, however MsrB3 levels were upregulated under both treatments but only in the presence of oxidative stress. These results suggest that MsrA and MsrB3 protect the cells from oxidative stress damage through different molecular pathways and that EGCG may be a therapeutic target to treat diseases related to damage by oxidative stress. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

The oxidation of methionine (Met) into methionine sulfoxide (met-(o)) leads to deleterious modifications to a variety of cellular constituents. These deleterious alterations can be reversed by enzymes known as methionine sulfoxide reductases (Msr). The Msr (MsrA and MsrB) family of enzymes have been studied extensively for their biological roles in reducing oxidized Met residues back into functional Met. A wide range of studies have focused on Msr both in vivo and in vitro using a variety of model organisms. More specifically, studies have noted numerous processes affected by the overexpression, under expression, and silencing of MsrA and MsrB. Collectively, the results of these studies have shown that Msr is involved in lifespan and the management of oxidative stress. More recent evidence is emerging that supports existing biological functions of Msr and theorizes the involvement of Msr in numerous biological pathways. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection