Absorption Of Cu Research Articles

Binding of Polyaminocarboxylate Chelators to the Active-Site Copper Inhibits the GSNO-Reductase Activity but Not the Superoxide Dismutase Activity of Cu,Zn-Superoxide Dismutase

In addition to its superoxide dismutase (SOD) activity, Cu,Zn-superoxide dismutase (CuZnSOD) catalyzes the reductive decomposition of S-nitroso-L-glutathione (GSNO) in the presence of thiols such as L-glutathione (GSH). The GSNO-reductase activity but not the superoxide dismutase (SOD) activity of CuZnSOD is inhibited by the commonly used polyaminocarboxylate metal ion chelators, EDTA and DTPA. The basis for this selective inhibition is systematically investigated here. Incubation with EDTA or DTPA caused a time-dependent decrease in the 680 nm d-d absorption of Cu(II)ZnSOD but no loss in SOD activity or in the level of metal loading of the enzyme as determined by ICP-MS. The chelators also protected the SOD activity against inhibition by the arginine-specific reagent, phenylglyoxal. Measurements of both the time course of SNO absorption decay at 333 nm and oxymyoglobin scavenging of the NO that is released confirmed that the chelators inhibit CuZnSOD catalysis of GSNO reductive decomposition by GSH. The decreased GSNO-reductase activity is correlated with decreased rates of Cu(II)ZnSOD reduction by GSH in the presence of the chelators as monitored spectrophotometrically at 680 nm. The aggregate data suggest binding of the chelators to CuZnSOD, which was detected by isothermal titration calorimetry (ITC). Dissociation constants of 0.08 +/- 0.02 and 8.3 +/- 0.2 microM were calculated from the ITC thermograms for the binding of a single EDTA and DTPA, respectively, to the CuZnSOD homodimer. No association was detected under the same conditions with the metal-free enzyme (EESOD). Thus, EDTA and DTPA must bind to the solvent-exposed active-site copper of one subunit without removing the metal. This induces a conformational change at the second active site that inhibits the GSNO-reductase but not the SOD activity of the enzyme.

Influence of Three Arbuscular Mycorrhizal Fungi and Phosphorus on Growth and Nutrient Status of Taro

Glasshouse and field experiments were conducted with micropropagated (tissue culture) taro plants and germinated corms to determine the arbuscular mycorrhizal dependency of taro. The micropropagated plants (cultivar Laiyu 3) were transplanted in plastic pots (3‐L) containing a mixture of vermiculite:perlite:peat:sand (2:1:1:1) with 0 or 8000 units of inoculum potential (UIP) of Glomus mosseae (Nicol & Gerd) Gerdemann and Trappe, Glomus versiforme (Karsten) Berch or Gigaspora rosea Nicolson & Schenck. Budded corms were planted in clay pots (8.5‐L) containing sterilized sandy loam mixed with 0 or 12,000 UIP of G. mosseae or G. versiforme, and 0 or 5 g Ca3(PO4)2 were added. In a field experiment, budded corms were placed in paper pots (0.5‐L) with sterilized sandy loam mixed with 0 or 4000 UIP of G. mosseae or G. versiforme and then planted directly in the field. Inoculation with AM fungi significantly increased survival rate and growth of tissue culture taro plants, and the contents of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), copper (Cu), and zinc (Zn), enhanced the formation of corms, numbers of second and third branch corms and corm yield, and enhanced the contents of crude protein, starch, and amino acids in the corms. Phosphorus fertilizer slightly increased plant yield but reduced plant absorption of Cu and Zn and root colonization by the AM fungi. Relative mycorrhizal dependence (RMD) of micropropagated plants was greater than that of corms.

First-principles study of H adsorption on and absorption in Cu(1 1 1) surface

Periodic, self-consistent density functional theory calculations have been employed to investigate hydrogen adsorption on and absorption in Cu(1 1 1) surface. It turns out that subsurface site adsorption was not preferred below 1 ML coverage. This result does not support the observations reported by Lee and Plummer that subsurface site was preferred at high coverage (between 0.5 and 0.66 ML) [Surf. Sci. 498 (2002) 229]. The loss peak of 928 cm −1 assigned to absorbed H at a subsurface site in their work has been attributed to asymmetric stretching mode for surface threefold hollow site adsorption, resulting from a reduced symmetry of adsorbed hydrogen from our calculations.

Absorption and Retention of Trace Minerals in Adult Horses

AbstractAbsorption and retention of Cu, Mn, and Zn were compared when feeding diets supplemented with oxide, sulfate, or organic-chelated forms of the minerals. Six mature Miniature Horses were used in the replicated 3 × 3 Latin square-designed experiment. The experiment was conducted in three 17-d periods, consisting of 10 d of diet adaptation followed by a 7-d total fecal and urine collection. Horses were fed a diet of 40% coastal Bermudagrass and 60% concentrate formulated to meet the energy, protein, Ca, and P requirements for maintenance of mature horses. Copper, Mn, and Zn were supplemented to provide 140 to 180% of the NRC (1989) recommended dietary concentrations for these minerals and were supplied in oxide, sulfate, and organic-chelate forms. Following total collections of feces and urine, feed, fecal, and urine samples were processed and analyzed for Cu, Mn, and Zn concentrations by atomic absorption spectrophotometry. Absorption of Cu, Mn, and Zn in all forms was low compared with previous studies, but systemic retention of these minerals was high. The cause of this disparity is unknown, although experimental error is unlikely. There were no differences in the absorption or retention of Cu, Mn, and Zn among the three forms of mineral supplements. Mature, idle horses may not be appropriate animals in which to evaluate absorption of various forms of trace minerals.

Effects of cadmium in herbage on the apparent absorption of elements by sheep in comparison with inorganic cadmium added to their diet

A meta-analysis of existing scientific literature recently suggested that Cd is absorbed more efficiently by sheep if it is in the organic form in grass, than if it is added as an inorganic supplement to the diet. We tested this experimentally by feeding sheep grass from contaminated soil, compared with uncontaminated grass and with Cd added to the diet. To produce contaminated herbage, Cd nitrate was added to soil in 11 lysimeters sown with perennial ryegrass, with a further 11 lysimeters receiving no Cd to produce uncontaminated herbage. In the Cd-treated lysimeters, soil had increased exchangeable K, Mg, and Ca, leachate had increased K, Mg, Ca, Na, and P, grass had increased Cd and reduced Mg, Na, P, Mn, Fe, Cr, Al, and Ni, and there was some reduction in grass yield compared with untreated lysimeters. Grass from Cd-treated or untreated lysimeters was fed to groups of 12 ewes for 2 days, with Cd intake equated by adding Cd nitrate to the concentrate feed of ewes receiving the uncontaminated grass. The apparent absorption of Cd, Zn, Mo, Cr, and Al was increased for ewes receiving Cd-enriched grass, and apparent absorption of Cu was reduced, compared to those receiving supplementary inorganic Cd. Most of the unabsorbed Cd was excreted in feces within 4 days of feeding. The ewes consuming Cd in grass had increased B concentrations in their urine, possibly due to adverse effects of Cd on kidney function. Finally, the ewes were offered a choice of the two herbages and they ate significantly more of the uncontaminated grass. It is concluded that the apparent absorption of Cd and other heavy metals by sheep in a short-term experiment was greater when Cd was in the grass than when the Cd was added in in an inorganic form and that sheep partially avoided herbage with a high Cd concentration.

Influence of Short-Chain Fructo-Oligosaccharides (sc-FOS) on Absorption of Cu, Zn, and Se in Healthy Postmenopausal Women

Objective: This study was carried out to evaluate the effect of short-chain fructooligosaccharides (sc-FOS) on the absorption of Cu, Zn, and Se among postmenopausal women who are potential candidates to subclinical trace element deficiencies.Design: A randomized double blind cross-over study.Setting: This study was carried out at the Human Nutrition Research Center, Clermont-Ferrand, France.Subjects: 11 postmenopausal women aged 53–70 y, not taking hormone replacement therapy were enrolled and completed the study.Interventions: Diets with 10 g/day sc-FOS or placebo were given for 5 weeks each in random order followed by a wash-out period of at least 3 weeks. At the end of each period, stable isotopes (3.19 mg 67Zn as ZnCl2, 2.06 mg 65Cu as CuCl2 and 52.3 μg 74Se as sodium selenite) and radiopaque pellets (as fecal excretion index) were administered during lunch. Stools were collected for the next 5–7 days. Isotopes were determined by ICP-MS (Cu and Zn) or GC-MS (Se).Results: Copper absorption was significantly enhanced (p = 0.042) by sc-FOS. No effect of sc-FOS was observed on Zn, and Se absorption.Conclusion: To our knowledge, this is the first study on the influence of sc-FOS on trace element metabolism. The observed increase in copper absorption may be of interest regarding daily copper requirements in menopausal women. However, the relevance of this observation remains to be established.

Nano-scale Cu metal patterning by using an atomic force microscope

Nano-scale Cu metal patterning was achieved by the use of an atomic force microscope. When the scanning with the cantilever of atomic force microscope (AFM) covered with the solid electrolyte was carried at a negative voltage, the Cu metal was deposited on TiO 2 substrates. The Cu metal on TiO 2, a glass and Si substrates was absorbed at the positive voltage. The deposition and the absorption of Cu could be repeated and carried out at room temperature without a specific treatment. The letters “Y” and “T” were written with 50 nm resolution by the scanning. The reaction between the tip of the cantilever and substrate is a simple electrochemical reaction.

Saturated absorption and reverse saturated absorption of Cu:SiO2 at λ = 532 nm

AbstractNonlinear absorption in copper‐doped silicate glasses was investigated by the Z‐scan technique using second harmonic radiation of a Nd:YAG laser (λ = 532 nm, τ = 55 ps). The simultaneous influence of saturated and reverse saturated nonlinear absorption processes was analyzed. The nonlinear absorption coefficient and the saturation intensity of copper‐doped glasses at laser intensity of 5.4 × 109 W cm−2 were measured to be 6 × 10−6 cm W−1 and 4.3 × 108 W cm−2, respectively. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of proline on copper transport in rice seedlings under excess copper stress

Copper exposure affects water flux and ion path in rice seedlings. To characterize the factors related to Cu transport in response to Cu exposure, rice ( Oryza sativa cv. Taichung Native 1) seedlings grown by hyperculture were subjected to excess CuSO 4 treatments, and Cu transport, water flux (transpiration rate and xylem sap extrusion), and proline level were assessed. Excess Cu decreased the water flux of rice seedlings. In spite of the decrease in water flux, Cu upward transport increased steadily with time. The absorption of Cu in roots displayed a phase lag between 3 and 12 h of Cu exposure, while proline content in the rice roots decreased dramatically. The supplement of proline in culture medium increased water flux and Cu upward transport in mild Cu-treated rice seedlings. In extreme Cu treatment, however, proline supplement decreased Cu upward transport, as the extent of water flux raised by proline supplement was diminished. Proline supplement to Cu-treated rice seedlings not only reduced the Cu absorption in the roots but also the Cu exclusion, suggesting supplement of proline accompanied by Cu exposure induce a barrier of Cu influx and efflux in rice roots. Therefore, it was concluded that excess Cu leads to inadequate proline and results in the malfunction of copper transport barrier in rice roots.

Effect of chelated mineral supplementation on the absorption of Cu, Fe, K, Mn and Zn in horse hair

The supplement effect of Cu, Fe, K, Mg, Mn and Zn chelated with glycine on the absorption of these elements by animals was evaluated. The evaluation was carried out by comparing the mineral concentrations found in hair of the animals before and after 47 days of supplementation with a combination of glycine-mineral chelates. Five horses known to be clinically well were used for this study. Instrumental neutron activation analysis (INAA) was applied to the determination of Cu, Fe, K, Mg, Mn and Zn concentrations in the horse hair samples. It was observed that the supplementation helps the Fe, K and Zn absorption by the animal organism. The data obtained suggest that the hair is a suitable material to investigate Fe, K and Zn in mineral metabolism in the animal organism.

Effects of Gestational Status on Apparent Absorption and Retention of Copper and Zinc in Mature Angus Cows and Suffolk Ewes

Six mature purebred Angus cows (3.5±1.5 years of age, 631.36±8.63 kg), three pregnant (250±7 days pregnant) and three non-pregnant and eight mature Suffolk ewes (5±1.2 years of age, 68.18±2.3 kg) four pregnant (115±5 days pregnant) and four non- pregnant were utilized in a five-day metabolic trial to determine the effects of gestational status (pregnant vs. non-pregnant) on apparent absorption and retention of copper (Cu) and zinc (Zn). Animals were selected based on body weight, age, and gestational status, and randomly assigned to metabolic crates for total fecal and urine collection. Animals were allowed to acclimate to their new environment for seven days. Pregnant and non-pregnant cows and ewes were then paired (within a species) by body weight and pair-fed throughout the 5 day collection period. Copper and Zn intakes were similar for pregnant and non-pregnant animals within a species. Apparent absorption of Cu (p<0.06) and Zn (p<0.04) were higher in pregnant cows relative to non-pregnant cows. Pregnant cows also had a higher apparent retention of Cu (p<0.05) and Zn (p<0.06) relative to non-pregnant cows. Pregnant ewes had a higher (p<0.01) apparent absorption and retention of Zn compared to non-pregnant ewes. However, apparent absorption and retention of Cu were similar for pregnant and non-pregnant ewes. These data indicate that certain physiological and/or metabolic parameters are altered in pregnant cows and ewes consuming an alfalfa-based diet that enhance the apparent absorption and retention of certain trace minerals. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 4 : 515-518)

Microstructural and Optical Absorption Properties ofCu-MgF2Nanoparticle Cermet Film

We examine the microstructural and optical absorption spectra of 10-30 vol%Cu-MgF2 nanoparticle cermet films prepared by co-evaporation invacuum. The results show that the Cu-MgF2 cermetfilms are mainly composed of the amorphous MgF2 matrix with embeddedfcc Cu nanoparticles of average size 12-24 nm. The results also showthat the optical absorption of the films decreases as the wavelengthincreases in the range of 200-800 nm. The surface plasmon resonanceabsorption peaks of Cu nanoparticles in 10, 20 and 30 vol%Cu-MgF2 films appear at 578, 588 and 606 nm, respectively.The interband transition absorption of Cu starts from 590 nm downwards.Based on the Maxwell-Garnett theory, the experimental opticalabsorption properties of the films have been quantitatively evaluated.

Effect of substituents, solute-solute-non-polar solvent interactions and temperature on the spectral properties of bis(dithiophosphato)copper(II) complexes

Extended studies by e.p.r. and electronic spectroscopy on the effect of different non-polar solvents, temperature and disulfide concentration on the spectral properties of bis(dithiophosphato)copper(II), Cu[(RO)2PS2]2, complexes [R = Me, Et and i-Pr] are reported. The molar absorptivity and e.p.r. intensity are very sensitive to the shape and size of the remote ligand substituents and increase in the order: Me < Et < i-Pr. The nature of the solvent and time after dissolution are also important regarding the magnitude of the e.p.r. intensity and molar absorptivity which, 1 h after dissolution, do not follow Beer's law. The molar absorptivities obtained at a given CuII(R2–dtp)2 concentration increase in the solvent order: n-hexane < n-heptane < CCl4 < PhMe < PhH < CHCl3. Twenty-four hours after dissolution the same samples exhibit: (i) linearity between absorbance and concentration of CuII(R2–dtp)2; (ii) a significant increase in molar absorptivity which is not equal for all the complexes studied and follows the same substituent and solvent orders. Beer's law is satisfied above 5 × 10−4 M for [(RO)2PS2]2Cu (R = Et, i-Pr) and above 3 × 10−3 M for [(MeO)2PS2]Cu. A significant additional increase, ca. 30–40%, of molar absorptivity, is obtained by increasing the solution temperature from 20 to 50 °C. The molar absorbtivity remains unchanged during 2–3 days after reducing the temperature. Further increase of molecular absorbtivity appears after addition of the corresponding disulfide of dithiophosphate [(RO2)PS2–S2P(RO)2] to CuII[(RO)2PS2]2. The molar absorptivity of Cu[(i-PrO)2PS2]2 increases from 4.8 × 103 cm−1 M−1, 1 h after dissolving the complex up to 2 × 104 cm−1 M−1 after addition of the corresponding disulfide. The observed effects are explained on the basis of a self-redox reaction taking place in this type of sulfur containing copper(II) complexes.

Influence of pH on Cd and Cu uptake, distribution and their effect on nitrate reductase activity in cucumber (Cucumis sativus L.) seedling roots

Influence of different pH solutions (5.0 and 7.0) on Cu2+ and Cd2+ absorption and distribution in root cells as well as effects of these metals on nitrate reductase activity (NR) in roots of cucumber seedlings were estimated. The absorption of Cu and Cd by roots measured as metal depletion in uptake solution was similar, both metal absorption was independent of the pH of solution. However, after rinsing of roots in distilled water (30 minutes), more Cu than Cd was found in protoplasts of root cells. More Cu was measured in all cell fractions when Cu was uptaken from pH 5.0 than from 7.0. The nitrate reductase activity after one hour of metal treatments was drastically decreased by Cu. The strongest reduction of enzyme activity was observed in roots treated with Cu in buffer with pH 5.0. Influence of Cd on the enzyme activity was weaker and was independent of the pH of solution. Lower concentration of Cd in solution (20 µM) increased NR activity. The data obtained prove the higher mobility of Cu than Cd into the cells of root. The mobility of Cu depends on pH of solution. Cu ions, but not Cd, influenced membrane permeability (K leakage). Cu acted more drasticly than Cd on NR activity.

Micronutrient accumulation and depletion in schizophrenia, epilepsy, autism and Parkinson’s disease?

Zinc has several crucial functions in brain development and maintenance: it binds to p53, preventing it from binding to supercoiled DNA and ensuring that p53 cause the expression of several paramount genes, such as the one that encodes for the type I receptors to pituitary adenine cylase-activator peptide (PACAP), which directs embryonic development of the brain cortex, adrenal glands, etc.; it is required for the production of CuZnSOD and Zn-thionein, which are essential to prevent oxidative damage; it is required for many proteins, some of them with Zn fingers, many of them essential enzymes for growth and homeostasis. For example, the synthesis of serotonin involves Zn enzymes and since serotonin is necessary for melatonin synthesis, a Zn deficiency may result in low levels of both hormones. Unfortunately, Zn levels tend to be low when there is excess Cu and Cd. Moreover, high estrogen levels tend to cause increased absorption of Cu and Cd, and smoking and eating food contaminated with Cd result in high levels of the latter. Furthermore, ethanol ingestion increases the elimination of Zn and Mg (which acts as a cofactor for CuZnSOD).Increased Cu levels may also be found in people with Wilson’s disease, which is a rather rare disease. However, the heterozygote form (only one faulty copy of the chromosome) is not so rare. Therefore, the developing fetus of a pregnant women who is low in Zn and high in Cu may experience major difficulties in the early development of the brain, which may later manifest themselves as schizophrenia, autism or epilepsy. Similarly, a person who gradually accumulates Cu, will tend to experience a gradual depletion of Zn, with a corresponding increase in oxidative damage, eventually leading to Parkinson’s disease. Also discussed are the crucial roles of histidine, histamine, vitamin D, essential fatty acids, vitamin E, peroxynitrate, etc. in the possible oxidative damage involved in these mental diseases.

遷移金属表面における水素原子の吸着及び吸収反応

We investigate the behavior of a H atom on metal surfaces. The potential energy curves (PECs) for the H atom adsorption on and absorption in Cu(111), Pt(111), and Pd(111) are calculated within the density functional theory. We show stronger dependence of the potential energies on the lateral position of the H atom at the position further from the surface in the case of Pt(111) than in the case of Pd(111), and no lateral position dependence in the case of Cu(111). Contrary to this, when the H atom comes close to and adsorbs on the surface, the dependence of its adsorption energy (a depth of potential well outside the surface) on the lateral position in the case of Cu(111) is stronger than in the case of Pd(111), and in the case of Pt(111) such dependencies are hardly seen and their adsorption energies are nearly the same. When the H atom penetrates the first layer of the surface, the activation barrier at a so-called fcc hollow site in the case of Pd(111) is the lowest in three surfaces.

Interactions of atomic hydrogen with Cu(111), Pt(111), and Pd(111)

We calculate the potential energy curves for H adsorption on and absorption in Cu(111), Pt(111), and Pd(111) within the density functional theory. We show stronger dependence of the potential energies on the lateral position of the H atom at the position further from the surface in the case of Pt(111) than one in the case of Pd(111), and no lateral position dependence in the case of Cu(111). Contrary to this, when the H atom comes close to and adsorbs on the surface, the dependence of its adsorption energy (a depth of potential well outside the surface) on the lateral position in the case of Cu(111) is stronger than one in the case of Pd(111), and such dependencies are hardly seen, and the adsorption energies are nearly the same in the case of Pt(111). When the H atom penetrates the first layer of the surface, the activation barrier at a so-called face-centered-cubic hollow site in the case of Pd(111) is the lowest in three surfaces.

Thiomolybdates — Simple but Very Versatile Reagents

A large number of thiometallate anions, MOxS4−xn−, and some of the seleno analogues, are known in which M is a transition metal in a high oxidation state. They are characterised by their strong colours arising from low energy S(Se)M charge transfer transitions, by unusual redox properties and by their ability to act as ligands to produce a wide range of heterometal complexes. This review outlines some of these properties associated with the thiometallate anions of molybdenum(VI). These anions are prepared by passing H2S through an alkaline molybdate solution, giving a sequential replacement of O atoms by S and ultimately MoS42− (TTM) as product. The thiomolybdates, particularly TTM, have been the most intensively studied because of their ease of preparation, their relatively greater thermal and hydrolytic stabilities and their biological roles. Unusual redox changes which involve internal electron transfer have been shown by reaction with organic disulfides and with CuII. In the latter case insoluble polymeric products are readily formed which, from EPR and EXAFS studies, involve S-bridged reduced Cu and Mo centres. Reaction of TTM with CuI, on the other hand, produces a range of complexes in which from 1 to 6 Cu ions add across the tetrahedral faces of TTM with no redox changes. Further CuI ions can be added to the [Cu6(MoS4)] moiety to produce cluster ions. This illustrates the ability of the thiometallates to act as building blocks for a very wide range of heterometal complexes ranging from simple linear ions to complex clusters, a prime example of the latter being the FeMo cofactor of the enzyme nitrogenase. TTM was identified sometime ago as the reactive intermediate in the Mo-induced Cu-deficiency that afflicts ruminants with serious consequences. Subsequently TTM, as its ammonium salt, has been successfully used in removing the excess Cu and then controlling the Cu levels of patients of Wilson’s disease. It appears to act by blocking the intestinal absorption of Cu and by converting Cu into a metabolically inert form, and in these respects is different to the mode of action of chelating agents which can be used for treating this disease.

Investigation of properties of copper, ferrous complexes with 1-(5-bromo-2-pyridylazo)-2-naphthol-6-sulphonic acid and application of substitution reaction in metallic complex to selective determination of trace amounts of metal

The report was the first to establish the new method for the selective determination of trace amounts of metal using the substitution reaction in metallic complex. The reactions between copper(II) and 1-(5-bromo-2-pyridylazo)-2-naphthol-6-sulphonic acid (BPANS) and between ferrous(II) and BPANS at pH 3.5 were studied. In absence of any masking reagent, the recommended method was selective in the determination of trace amounts of copper with Fe–BPANS complex as chromogenic reagent because copper(II) can substitute Fe from Fe–BPANS complex to form Cu–BPANS complex. The ordinary spectrophotometric method was unsuitable to the substitution reaction because the excess of Fe–BPANS complex had the high absorption and affected seriously the absorption of Cu–BPTANS complex. The spectral correction principle may eliminate the above influence to give the simple determination of the composition ratio, stepwise absorptivity ( ε) and stability constant ( K) of metal complex. For analysis of samples, the recovery of copper was between 96.5 and 106% with R.S.D. less than 5%.

EPR and optical absorption of Cu 2+ ions in ternary K 2SO 4–Na 2SO 4–ZnSO 4 glasses

Electron Paramagnetic Resonance (EPR) and optical absorption spectra of Cu 2+ ions in K 2SO 4–Na 2SO 4–ZnSO 4 glasses have been studied. EPR spectrum of the glasses doped with Cu 2+ ions exhibits a pronounced peak at g=2.05 and a broad quadruplet with low signal intensity at g=2.39; the latter arising from the hyperfine splitting of g ∥. The temperature dependence of the glasses doped with Cu 2+ ions has also been studied. The optical absorption spectrum of the glasses doped with Cu 2+ ions shows a single broad absorption band in the near-infrared region, which is attributed to 2B 1g→ 2B 2g transition. By correlating the EPR and optical spectral data, the molecular orbital coefficient β 2 1 for Cu 2+ ions has been evaluated.