A spectroscopic investigation of the behavior of bovine erythrocuprein and its four-copper-substituted derivative below pH 4.5 suggests strongly that the metal ion bound to the native zinc site is reversibly released in the pH range 3.0 I pH I 4.5. Published spectra of the copper-cobalt derivative suggest that cobalt is similarly lost from that derivative in the same pH range. Dialysis of the native copper-zinc protein at pH 3.6 resulted in removal of 95% of the Zn but only 5% of the Cu, although the visible, UV, and ESR spectra were only slightly changed from the initial spectra at pH 3.6. The release of free cupric ion from the four-copper derivative at low pH was also determined potentiometrically with use of a copper-selective electrode. The pH dependence of the spectral changes observed for the copper-zinc, four-copper, and copper-cobalt derivatives was virtually identical. The zinc-free derivative of erythrocuprein was also observed to undergo small but distinct changes in its ESR and visible spectra when the pH was changed. These changes occurred with a midpoint pH of 5.0. Below pH 3, copper is also lost from the protein.Bovine erythrocuprein is a relatively small (mol wt 31 200) globular protein consisting of two equivalent subunits, each of which binds one copper2 and one zinc3 in close proximity. X-ray crystallographic studies by the RichadsonsM have shown that the major structural feature of each subunit is an eight-stranded barrel of 6 structure; two loops of irregular structure are also seen which are connected to the ends of the strands forming the barrel. The Cu" and Zn" ions in each subunit are separated by approximately 6 A. The CUI' is five coordinate, with the four histidyl imidazole rings that are bound to it (histidines 44, 46, 61, and 118) forming a distorted square plane, the fifth ligand being water. Three of these histidines (44, 46, and 118) have their a carbons in the @barrel portion of the structure. The fourth, histidine 61, provides an imidazole ring that is deprotonated and bridges the Cu" and Zn" ions. That residue is found in the same single loop of irregular structure that contains those residues that provide the other ligands to Zn", Le., histidines 69 and 78 and aspartate 81. The four ligands to Zn" are arranged in a distorted tetrahedral arrangement.

The all‐inorganic, stable, low‐vapor‐pressure conductive electrolyte normalLifalse(SO2)3AlCl4 that has been proposed as a battery electrolyte for lithium rechargeable cells has been characterized by cyclic voltammetry. The chief reduction product is assumed to be lithium dithionite. During oxidation, AlCl4− is electrochemically oxidized to soluble molecular chlorine, which then chemically oxidizes the cathode discharge product. Addition of soluble molecular chlorine to the electrolyte significantly reduces passivation of the cathode during reduction.

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SYNOPSISSurface properties of a number of commercial thermoplastic polymer films were investigated before and after brief exposures to RF induced, low temperature gas plasmas. Water wettability and adhesion of vapor deposited aluminum to thin films (8-12 micron) of polyethylene, polypropylene, polyester, polysulfone, polycarbonate, and polyvinylidene fluoride films were studied before and after treatments with oxygen, 96% CF4/4% O,, and helium plasmas. Treatment with oxygen plasmas showed the greatest change in water wettability for polyvinylidene fluoride and polypropylene films, while treatment with 96% CF4/4% 0, showed dramatic changes in wettability of polycarbonate, polysulfone, and polystyrene. Excellent adhesion of aluminum was found for polymers that had been previously exposed to gas plasmas.