Thesis (Ph.D.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references.

Thesis (M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (ℓ. 62-65)

Thesis(M.S.)--Auburn University, 2005. / Includes bibliographic references.

Thesis (Ph. D.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references.

Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Toxicology." Includes bibliographical references (p. 171-202).

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Lee A. Fuiman. Vita. Includes bibliographical references.

No description available.

For a long time, fish is regarded as an important food source beneficial for human health. But there’s nowadays an increasing concern of fish consumption for increasing existence of mercury (Hg) and methylmercury (MeHg), which can be accumulated upon fish intake and pose health threats to human.  It is suggested that children and pregnant women are more vulnerable to effects due to accumulation of Hg. There have been continuous efforts done by governments and researchers all over the world, e.g. publishing national and regional advisories on fish consumption, in order to inform public related risks aroused by excess fish consumption. Sweden, as one of the earliest countries abandons the use of Hg (Regeringskansliet, http://www.sweden.gov.se), has published a national advisory on fish consumption for pregnant and breastfeeding women (Swedish National Food Agency, SLV, http://www.slv.se/). Hg level in edible fish organs is also limited for safe consumption.  In order to picture a better image of this, we investigated existed databases in Sweden on Hg levels in fish, fishery statistics, consumption data, and observed Hg level in human in recent decades for human exposure to Hg in Sweden. Though mercury emission decreased, the exposure to mercury via fish consumption is still high. We believe there’s a potential risk for Swedish inhabitants, especially pregnant women and women in breastfeeding, as well as young children. It is strongly recommended a safer limit of Hg in fish products for consumption in Sweden.             We hope for more synthesized knowledge of safe fish consumption that benefit for the public and promote regional/national policy in having an up-to-date fish consumption advisory in Sweden.

Monomethylmercury (CH3Hg+ and its complexes; hereafter referred to as MeHg) in the intracellular environment is known to be predominantly bonded to thiol-containing biomolecules but the identities of these target biomolecules remain unknown. Some evidence suggests that binding with glutathione acts as a detoxification mechanism for MeHg, while binding with L-cysteine permits MeHg transport across the blood–brain barrier resulting in neurotoxicity. However, the occurrence of these complexes in biological tissues has not been confirmed analytically, and little is known about their kinetic stability. In this thesis, methylmercury L-cysteinate (CH3HgCys) and methylmercury L-glutathionate (CH3HgGlu) were synthesized and structurally characterized by proton nuclear magnetic resonance (1H NMR), electrospray ionization mass spectrometry (ESI-MS), and X-ray crystallography. A new analytical method was developed combining high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICPMS). The method was capable of separating and analyzing CH3HgCys and CH3HgGlu complexes, as well as CH3HgX and inorganic HgX (X = H2O, OH-, or Cl-), with detection limits at the sub-micromolar levels. Using a new enzymatic hydrolysis method to isolate MeHg species in biological tissues, the HPLC-ICPMS method was successfully applied for the determination of MeHg speciation in the muscle tissue of dogfish (Squalus acanthius). These results provide the first analytical evidence for the presence and dominance of CH3HgCys in fish muscle. The analytical method was also used to study the kinetic stability of CH3HgCys and CH3HgGlu under a range of environmental and intracellular conditions. In general, CH3HgGlu was more stable than CH3HgCys under light exposure or darkness. The stability of both compounds decreases dramatically with increasing ionic strength (I). Half-life of CH3HgCys decreases from 34.1 h (I = 0.01 M) to 5.9 h (I = 0. 5 M) and the half-life of CH3HgGlu decreases from 259 h (I = 0.01 M) to 35.9 h (I = 0. 5 M). Suggesting major differences in their cycling in freshwater (I < 0.01M), seawater (I ≈ 0.7M) and body fluids (I ≈ 0.16 M). The analytical technique and the findings from this thesis research provide a new analytical framework for the study of MeHg speciation in natural waters, and the metallomics of MeHg in biological systems.

Monomethylmercury (CH3Hg+ and its complexes; hereafter referred to as MeHg) in the intracellular environment is known to be predominantly bonded to thiol-containing biomolecules but the identities of these target biomolecules remain unknown. Some evidence suggests that binding with glutathione acts as a detoxification mechanism for MeHg, while binding with L-cysteine permits MeHg transport across the blood–brain barrier resulting in neurotoxicity. However, the occurrence of these complexes in biological tissues has not been confirmed analytically, and little is known about their kinetic stability. In this thesis, methylmercury L-cysteinate (CH3HgCys) and methylmercury L-glutathionate (CH3HgGlu) were synthesized and structurally characterized by proton nuclear magnetic resonance (1H NMR), electrospray ionization mass spectrometry (ESI-MS), and X-ray crystallography. A new analytical method was developed combining high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICPMS). The method was capable of separating and analyzing CH3HgCys and CH3HgGlu complexes, as well as CH3HgX and inorganic HgX (X = H2O, OH-, or Cl-), with detection limits at the sub-micromolar levels. Using a new enzymatic hydrolysis method to isolate MeHg species in biological tissues, the HPLC-ICPMS method was successfully applied for the determination of MeHg speciation in the muscle tissue of dogfish (Squalus acanthius). These results provide the first analytical evidence for the presence and dominance of CH3HgCys in fish muscle. The analytical method was also used to study the kinetic stability of CH3HgCys and CH3HgGlu under a range of environmental and intracellular conditions. In general, CH3HgGlu was more stable than CH3HgCys under light exposure or darkness. The stability of both compounds decreases dramatically with increasing ionic strength (I). Half-life of CH3HgCys decreases from 34.1 h (I = 0.01 M) to 5.9 h (I = 0. 5 M) and the half-life of CH3HgGlu decreases from 259 h (I = 0.01 M) to 35.9 h (I = 0. 5 M). Suggesting major differences in their cycling in freshwater (I < 0.01M), seawater (I ≈ 0.7M) and body fluids (I ≈ 0.16 M). The analytical technique and the findings from this thesis research provide a new analytical framework for the study of MeHg speciation in natural waters, and the metallomics of MeHg in biological systems.