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The structures of the mono-, bis-, and tris(glycinato)copper(II) complexes in aqueous solution have been determined by X-ray absorption spectroscopy. Four solutions with different complex ratios have been examined, and the species concentrations have been determined on the basis of complex stability constants. An advanced data analysis including multiple-scattering effects and multielectron excitation processes produced quantitative information on the Cu(II)-glycinate complexes present in aqueous solution. The structure of the bis(glycinato)copper(II) complex, which has a low solubility in water, has been determined for the first time. It has been found to have a distorted octahedral geometry with two bidentate glycine ligands coordinating to the Cu 2+ ion in the equatorial plane and with the axial sites occupied by two additional water molecules at 2.40 ( 0.06 Å. Analysis of the X-ray absorption data allowed a detailed description of the structures of the mono-and tris(glycinato)copper(II) species. The former complex has an axially elongated octahedral structure with a glycine bidentate ligand and two water molecules placed at the equatorial and two water molecules at the axial positions (2.44 ( 0.08 Å). Experimental data for the latter complex were also explained in terms of a distorted octahedral model with two glycine molecules in the equatorial plane and with the amino nitrogen of the third glycine coordinating to the Cu 2+ ion at the axial site at a distance of 2.33 ( 0.05 Å. This result conflicts with the regular octahedral geometry previously determined by XRD investigations. The axial bonds of the three complexes are significatively longer than the average within the hexaaquocopper-(II) ions. This finding indicates that the axial bonds are lengthened upon the formation of the Cu-glycine complexes and the Cu(II)-water interaction at the axial site is weakened.

Composition and existence range of aggregates formed by sodium taurodeoxycholate in aqueous micellar solutions were studied. Electromotive force measurements provide the free concentration of hydrogen and sodium ions. Solubility measurements of barium taurodeoxycholate give that of taurodeoxycholate ions. Experimental data obtained at 25 °C and at seven different concentrations of N(CH3)4Cl, used as an ionic medium, can be explained by assuming the presence of aggregates with different composition depending on the concentration of the reagents and the ionic strength. The comparison with deoxycholate and glycodeoxycholate shows analogies and differences. Protonated species were observed only at pH approximately less than 8.3. At pH's within the range 8.3−10 the distribution of the micellar aggregates remains nearly constant at a given ionic medium concentration. As it is expected, the size of the micellar aggregates increases upon increasing the ionic strength. A trimer was found for all the concentrations of the ionic medium. Most of the species found have aggregation numbers of the anion that are multiples of 3. It can be supposed that the trimer may be the fundamental unit of the structure of the micellar aggregates. An appreciable amount of a dimer, if any, was not detected. The affinity of sodium ions for the micellar aggregates is greater than that of N(CH3)4 + ions. The charge density of the micellar aggregates was determined to be low.

The local environment of the Cu2+ ion in copper chloride solutions has been investigated by x-ray absorption spectroscopy. Three aqueous solutions of CuCl2 with increasing Cl−/Cu2+ ratio have been examined. An advanced data analysis including multiple-scattering effects produced quantitative information on the chlorocuprate complexes present in solution and provided evidence for an increasing degree of complex formation between Cu2+and Cl− ions with increasing chloride concentration. The presence of Cu–Cl interactions at the axial site has been detected in a 0.1 M CuCl2 solution for the first time. At higher chloride concentrations (Cl−/Cu2+ratios equal 10 and 30) the equatorial positions in the distorted octahedral copper coordination are occupied by 3.2 and 3.0 oxygens and 0.8 and 1.0 chloride ions, respectively, while the axial positions are occupied by 1.2 and 1.0 oxygens and 0.8 and 1.0 chloride ions, respectively. The results are found to be consistent with previous x-ray and neutron diffraction studies and with experimental data on the complex formation. © 1997 American Institute of Physics

The effect of short-term oral zinc supplementation (zinc sulfate 600 mg/day) on hepatic encephalopathy, was assessed in a double-blind, crossover trial. Fifteen cirrhotic patients with stable, chronic hepatic encephalopathy were randomized to receive either oral zinc or a placebo for 10 days. Following a two-week washout period, these were crossed over to the alternate treatment. Conn's index, which comprises the evaluation of the mental state, asterixis, number connection test, EEG record, and plasma ammonia, was used to score the degree of hepatic encephalopathy, both at the beginning and end of each treatment period. Serum zinc was significantly raised after oral zinc administration and reached the levels observed in cirrhotics without hepatic encephalopathy. Despite this, however, no modification in the parameters included in Conn's index were observed. In conclusion, this study failed to confirm that short-term oral zinc supplementation improves chronic hepatic encephalopathy.

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Composition and existence range of aggregates formed by sodium glycocholate in aqueous solutions were studied. Electromotive force measurements provided hydrogen, sodium, and glycocholate ion free concentrations. Lead(II) glycocholate solubility measurements yielded the free concentration of glycocholate ions, as well. Experimental data obtained at 25 °C and at three different concentrations of N(CH3)4Cl, used as a constant ionic medium, can be explained by assuming the presence of aggregates with different compositions, depending on reagent and ionic medium concentrations. The distribution of the species found at the same concentration of ionic medium and close to neutrality remains constant. As expected, the size of the aggregates increases by increasing ionic medium and reagent concentrations. A dimer is the prevailing species at low concentrations, and all of the found species have even anion aggregation numbers. In solutions with the highest concentration and ionic strength, aggregate multiples of eight are present at a high percentage. These results agree with structural investigations that proposed as building blocks of sodium glycocholate micellar aggregates a dimer and an octamer. A strong analogy with the composition of taurococholate aqueous solutions is observed. The comparison with deoxycholate, glycodeoxycholate, and taurodeoxycholate shows wide differences.

The composition and range of existence of aggregates formed by sodium taurocholate in aqueous micellar solutions were studied. Electromotive force measurements were used to obtain concentrations of free hydrogen and sodium ions. Experimental data obtained at 25 degrees C and at three N(CH3)(4)Cl concentrations, used as anionic medium, can be explained by assuming the presence of aggregates with different compositions depending on the reagent concentrations and the ionic strength. Comparison with taurodeoxycholate shows wide differences. Protonated species of taurocholate are observed only at pH less than or similar to 5. At higher pH, the micellar aggregate distribution remains nearly constant at a given ionic medium concentration. As expected, the size of the micellar aggregates increases on increasing the ionic strength. A dimer is found at all concentrations of the ionic medium. All species found have aggregation numbers of anions in multiples of two. The affinity of sodium ions for micellar aggregates is greater than that of N(CH3)(4)(+) ions