Distribution and Chemical State of Heavy Metal Ions Absorbed by Chlorella Cells

Abstract

Experiments were undertaken to determine whether the distribution of copper, cadmium, and uranyl ions in Chlorella cells differed with different heavy metal ions. The amounts of these three metals in each cell fraction were in the following decreasing order: intracellular soluble fraction > intracellular particle fraction >> cell wall fraction. Heavy metal ions were found most abundantly in the intracellular soluble fraction and only 3-5% of the heavy metal ions were in the cell wall fraction. The distribution of uranyl ion in Chlorella cells differed from both that of copper ion and cadmium ion. The distribution of heavy metal ions in the intracellular soluble fraction was investigated in detail by gel filtration, which showed that copper ion was present in both the high and low molecular weight fractions, while cadmium and uranyl ions were present only in the high molecular weight fraction. These results indicated that substances combined with heavy metal ions in Chlorella cells differed with different heavy metal ions. Next, the chemical state of cupric ion absorbed in cells was studied in detail using ESR. The values of g_¦¦ and |A_¦¦(Cu)| of cupric ion showedthat cupric ion was coordinated by two nitrogen and two oxygen atoms.