Sam F. Trelease

Seleno-amino acid found in Astragalus bisulcatus.

Ion-exchange and filter-paper columns were used in a separation of amino acids from an extract of Astragalus bisulcatus. Two amino acids were identified, S-methylcysteine and Se-methylselenocysteine.

Influence of sulfur on the toxicity of selenium to Aspergillus

Experiments were performed to investigate the influence of the sulfur/selenium ratio and sulfur amino acids on the selenate inhibition of Aspergillus niger. All the sulfur amino acids investigated were able to counteract, partially or wholly, the inhibition of growth. Mycelial growth and selenium accumulation were found to be a function of the sulfur/selenium ratio when sulfur was supplied as sulfate and selenium as selenate. As the ratio was increased, growth increased and selenium accumulation decreased. The results suggest that selenate toxicity in this organism is of a multiple nature, consisting of a number of competitive actions between sulfur and selenium analogues. 34 references, 4 figures, 3 tables.