Direct determination of gold, cobalt, and lithium in blood plasma using the Mini-Massmann carbon rod atomizer

Properties of prolyl 4-hydroxylase containing firmly-bound iron

1. Prolyl 4-hydroxylase (prolyl-glycyl-peptide, 2-oxoglutarate:oxygen oxidoreductase, EC 1.14.11.2) was isolated in a form containing iron (0.85-1.1 mol Fe/mol enzyme). 2. The enzyme was pure according to gel electrophoresis and had a high specific activity (1.8-2.6 mumol . mi-1 . mg-1). 3. Experiments with metal chelators showed this iron to be firmly bound and to be required for catalytic activity. 4. According to EPR spectrometry the bound iron is not part of a [2Fe-2S] or a [4Fe-4S] cluster. 5. The enzyme activity is to a large extent independent of added Fe2+. 6. The enzyme activity is completely dependent on ascorbate. 7. In the absence of ascorbate but the presence of substrates the enzyme is irreversibly inactivated. 8. Continuous measurement of enzyme activity was possible by following oxygen uptake.

Binding of gold to bovine serum albumin using flameless atomic absorption

A graphite furnace atomic absorption spectrophotometric assay capable of accurately determining nanogram amounts of gold in biological fluids was developed. The presence of bovine serum albumin and/or phosphate in the sample reduced the method sensitivity without affecting the linear response. Binding of gold was studied by ultrafiltration using cones with a molecular weihght cutoff of 25,000. The binding of gold at various concentrations to 2 and 4% bovine serum albumin in 0.1 M phosphate buffer, pH 7.4, was independent of the gold and protein concentrations. In the 2-10 microgram/ml range, the overall binding values (mean +/- SD) of gold to 2 and 4% bovine serum albumin were 98 +/- 1.6 (n = 35) and 99 +/- 1.0% (n = 15), respectively. When ultrafiltration cones with a molecular weight cutoff of 50,000 were used, the extent of binding to 2% bovine serum albumin was 85.4 +/- 1.6% (n=11). This statistically significant difference (p less than 0.001) was due to variations in the protein retention of the two cone types. Interaction studies showed that gold was not displaced from the binding sites by salicylic acid (200 microgram/ml) or vice versa.

Determination of gold in plasma and plasma fractions by atomic absorption spectrometry and by neutron activation analysis

Three techniques of gold analysis, flame and electrothermal atomic absorption spectrometry and neutron activation analysis, have been compared, using plasma and plasma fractions (derived by gel chromatography) from rheumatoid patients receiving aurothiomalate therapy and from plasma samples incubated with aurothiomalate in vitro. The three methods correlated well in the analysis of gold in whole plasma, but only neutron activation analysis was suitable for the assay of all the plasma fractions. The susceptibility of the two atomic absorption methods to interference by sodium chloride was investigated.