Michael T. Henzl

Selective recovery of gold and other metal ions from an algal biomass.

The authors observed that the pH dependence of the binding of Au/sup 3 +/, Ag/sup +/, and Hg/sup 2 +/ to the algae Chlorella vulgaris is different than the binding of other metal ions. Between pH 5 and 7, a variety of metal ions bind strongly to the cell surface. Most of these algal-bound metal ions can be selectively desorbed by lowering the pH to 2; however, Au/sup 3 +/, Hg/sup 2 +/, and Ag/sup +/ are all bound strongly at pH 2. Addition of a strong ligand at different pHs is required to elute these ions from the algal surface. Algal-bound gold and mercury can be selectively eluted by using mercaptoethanol. An elution scheme is demonstrated for the binding and selective recovery of Cu/sup 2 +/, Zn/sup 2 +/, Au/sup 3 +/, and Hg/sup 2 +/ from an equimolar mixture. 20 references, 2 figures.

Accumulation of elemental gold on the alga Chlorella vulgaris

Abstract The accumulation of Au(0) by lyophilized preparations of the alga Chlorella vulgaris has been investigated. Gold is bound to the algae upon suspending dried algal cells in solutions containing hydrogen tetrachloroaurate (III). Relative amounts of ionic and atomic algal-bound gold were determined by thiourea extraction. It was found that the amount of algal-bound atomic gold produced from ionic gold increased with time. The effect of algal-bound gold concentration on the rate and extent of gold reduction was observed. It is suggested that at least three different classes of sites are available for gold binding and reduction. The effect of Au(0) accumulation on the binding ability of gold-bound algae was also investigated, and an apparent enhancement of gold binding ability is reported.

The structure of aPhaseolus vulgaris cDNA encoding the iron storage protein ferritin

A cDNA containing the entire coding region for the iron storage protein ferritin has been isolated from the French bean plant,Phaseolus vulgaris L. cv. Tendergreen. Ferritin protein was purified from young leaves and shoot meristem tissue and used to raise antisera in mice. A λgt11 cDNA library was constructed from seed-derived poly(A)+ RNA, and screened with the mouse anti-ferritin serum. A 1.2 kb immunopositive phage DNA insert was isolated and sequenced. The derived amino acid sequence shows substantial similarity with other ferritin sequences. The 5′ untranslated region contains two out-of-frame AUG codons, a region of extreme pyrimidine composition bias and potentially stable secondary structure.

Synthesis of a new chelating gel: Removal of Ca2+ ions from parvalbumin

The synthesis of a chelating gel which contains the effective metal chelating agent ethylenediaminetetraacetic acid covalently linked to amino-agarose is described. This gel is shown to be a rapid and extremely effective material for the removal of tightly bound, but labile metal ions from proteins without introducing contaminants into the biological system. The synthesis involves the formation of an amide linkage between the dangling carboxylate arm of the [Co(EDTA)Cl]2-complex and amino-agarose using a standard carbodiimide coupling reaction. The chelating gel is shown to remove approximately 98.5% of the calcium from fully bound Ca2-parvalbumin and over 99% of the europium from Eu2-parvalbumin.

Lanthanide-binding properties of rat oncomodulin

Oncomodulin, the parvalbumin-like calcium-binding protein frequently expressed in tumor tissue, was isolated from Morris hepatoma 5123tc and studied using the luminescent lanthanide ions, Eu3+ and Tb3+. Titrations of the apoprotein - whether monitored by indirect excitation of bound Tb3+, by direct laser excitation of bound Eu3+, or by quenching of the intrinsic tyrosine fluorescence - all indicated the presence of two high-affinity binding sites for lanthanide ions, as in parvalbumin. Moreover, the appearance of the Eu3+ 7F0----5D0 excitation spectrum of Eu2-oncomodulin was found to be highly pH-dependent, as previously observed with parvalbumin. At pH 5.0, it consists of a single peak centered at 5796 A, having a linewidth of approximately 6 A. At higher pH values, this spectrum is replaced by a broader, more symmetric peak at 5782 A. Oncomodulin, however, was found to differ from parvalbumin in at least one important respect: In contrast to the muscle-associated protein, the affinities of the CD site in oncomodulation for Tb3+ and Ca2+ were found to be rather similar, with KCa/KTb approximately equal to 11 +/- 2.

IDENTIFICATION OF A NOVEL PARVALBUMIN IN AVIAN THYMIC TISSUE

A novel calcium-binding protein has been isolated from chicken thymus tissue. Its molecular weight (approximately 11,500) and characteristic interactions with Tb3+ and Eu3+ identify the protein as a member of the parvalbumin family. Electrophoretically distinct from both chicken (muscle) parvalbumin and avian thymic hormone, it represents the third parvalbumin to be identified in avian tissues and the second to be identified in the avian thymus gland.

Avian thymic hormone and chicken (muscle) parvalbumin are distinct proteins : isolation of a muscle parvalbumin cDNA fragment by PCR

Access to the nucleotide sequence of parvalbumin from chicken muscle was gained via the polymerase chain reaction. In the absence of specific amino acid sequence data, the PCR primers were based on consensus data for the two parvalbumin Ca2(+)-binding sites. The 137 bp fragment obtained by amplification clearly codes for a parvalbumin, as judged by the presence of 10 invariant codons within the sequence flanked by the primers. When used to probe poly(A)+ RNA from chicken muscle, the fragment recognizes an 800 nucleotide transcript. The translated nucleotide sequence of the muscle protein is unmistakably distinct from that of the thymus-specific parvalbumin known as avian thymic hormone. Of the 31 amplified residues, the two proteins differ at 14. The presence of a distinct parvalbumin in chicken thymus is consistent with the potent effector role proposed for the protein.

COMPARISON OF THE METAL ION BINDING SITES IN RAT ONCOMODULIN AND PARVALBUMIN

Publisher Summary This chapter examines the comparison of the metal ion binding sites in rat oncomodulin and parvalbumin. The change observed with increasing pH in the rat parvalbumin spectrum is consistent with report for the pike and carp proteins. As the pH is raised, the doublet centered at 5794 A is gradually replaced by a broad peak centered at 5784 A. There is a definite shoulder on the high pH spectrum that is far less pronounced in the spectrum of the pike protein. This pH-dependence of the spectra is attributed to the deprotonation of water molecules coordinated to the bound Eu 3+ ions. At higher ratios, a broad feature appears at lower wavelength. This observation implies sequential occupation of the EF site followed by the CD site. Since the high pH spectrum arising from Eu 3+ bound at the CD site is already apparent at pH 5.5, the pKa for this transition must be substantially lower than that observed for the parvalbumins examined. The ability to distinguish the bound Eu 3+ ions in oncomodulin spectroscopy has allowed to measure preference of each site for the lanthanide ion relative to Ca 2+ .