Date of Award

1-1-1983

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biochemistry

Abstract

The purpose of this study was to detect and identify low molecular weight (<10,000 Da) copper and zinc binding ligands in biological materials believed to function in trace element transport using modified gel chromatography (MGC) as the major detective method. MCG involves the gel filtration of a biological specimen on a column equilibrated with a chosen metal ion. In this way, the ligands can be separated from each other without being separated from the investigative metal ion. The ligands were separated by molecular weight on the gel matrix and the column eluent was monitored for metal binding peaks by the use of atomic absorption spectrophotometry. Several ligands could be detected in a single sample and the detection limit was 0.1 (mu)mol for some common ligands.Milks and infant formulas were examined for the human species-specific zinc binding ligand thought to be essential to the acrodermatitis enteropathica (AE) infant. Citrate was detected in all milks but picolinate was not detectable in any. Formula, human, and goat milk also contained detectable free amino acids. Human and bovine milk proteins also bound metal. No human species-specific ligands were detected. Alternative causes of the diet-dependent AE zinc deficiency and a mechanism for the molecular origin of AE are suggested.Viokase, a porcine pancreatic extract, has been found to be effective in the treatment of variant AE, an effect reportedly due to the presence of citrate or picolinate. Neither ligand was detectable by MGC although amino acid ligands were highly concentrated. Given the competitive nature of trace metal-ligand binding, some other aspect of Viokase probably ameliorates the variant AE symptoms.Ligands were detected in porcine intestinal mucosa. However, their potential as transport ligands depends on future studies to determine if the ligands were artefacts of sample preparation.Conjugated bilirubin, peptides, and amino acids were identified as ligands in human bile and are probably also present in porcine bile. The peptides were not individually identified but possibly play specific roles in normal copper excretion.

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