Mol Cl Research Articles

Monometallic, homo- and heterobimetallic complexes based on redox active tris(3,5-dimethylpyrazolyl)borato-molybdenum and -tungsten nitrosyls—I. Meta substituent effects on the reduction potentials of monometallic arylamide complexes

The complexes [Mo(NO)LCl(NHC 6H 4-3-Z)] (L = HB(3,5-Me 2C 3N 2H) 3; Z = F, Cl, Br, Me, OMe, CF 3, NO 2), [W(NO)L(NHC 6H 4-3-Z)] (Z = F, Cl, Br, Me, OMe, COME, CF 3, NO 2) and [W(NO)L(NHC 6H 4-3-CF 3) 2] have been synthesized and characterized by spectroscopic methods. All of the monoarylamide complexes undergo one-electron reduction processes at potentials which vary according to the nature of Z. A linear correlation was found between the reduction potentials within each of the two series and the Hammett meta substituent parameters, σ m , for Z. The respective reaction constants, ϱ m , and intercepts, E f 0, are for [Mo(NO)LCl(NHC 6H 4-3-Z)], ϱ m = 5.50 (0.39), E f 0 = −0.848 (0.009) V and for [W(NO)L(NHC 6H 4-3-Z)], ϱ m = 4.75 (0.50), E f 0 1.291 (0.011) V.

The synthesis of a novel trimetallic complex containing three redox centres and an assessment of inductive effect transmission through an iron atom

The novel trimetallic complex [Fe{η 5-C 5H 4SMo(NO)LCl} 2]; in which L = tris(3,5-dimethylpyrazolyl)hydroborate, and its bimetallic analogue [{(Mo(NO)LCl)} 2( m-S 2C 6H 4)] have been synthesised; electrochemical studies of these compounds indicate that the inductive effects of the molybdenum-containing substituent are transmitted to equal extents through the CFeC and CCC bridging atom chains.

Etude de la chloration de l'uracile en milieu aqueux dilue study of the chlorination of uracil in dilute aqueous medium

Abstract The chlorination of uracil in dilute aqueous medium (6.1 ≤ pH ≤ 8.6) for T ≤ 0.1 (T = (CI)0/(U)0, and (U)0respectively correspond to molar concentrations of chlorine and uracil introduced to the medium) leads to the formation of 5‐Chloro‐uracil (C1U). The reaction rate is : r = K(pH)(U)(Cl). Neutral and ionized forms of Cl (HOCl/CIO‐) and U(H2U/HU‐) coexist in the solution, but only H0C1/HU‐ react. Then r(Ms‐1) = 242(HU∼)(HOCl) at 20°C. For 0 < T ≤ 15, 1 mol U consumes a maximum of 7 mol Cl, ClU is a reaction‐intermediate and CO2 appears. During chlorination of the mixture of ammonia (NH3) and U, U is only eliminated after the oxydation of NH3.

Osmoregulation in the Galápagos Marine Iguana, Amblyrhynchus cristatus

Water fluxes were measured isotopically for free-ranging marine iguanas on Isla Fernandina, Galápagos. Captive animals were fed a normal diet of algae supplemented with seawater and held in outdoor cages. Concentrations of electrolytes in food, plasma, nasal secretions, feces, and urine were measured, as was water content of food and excreta. Values thus obtained were used in conjunction with field metabolic rates and food utilization efficiencies to construct field water and electrolyte budgets for adult animals. Field water influx averaged 48.2 ml/kg day for adults and 31.1 ml/kg day for hatchlings. For adults, 58% of water influx comes from food, 38% from seawater ingestion, and 4% from metabolism. Electrolyte input is high (14.5 m mol Na⁺, 3.6 m mol K⁺, and 15.7 m mol Cl⁻/kg day. Almost all of the K⁺ and one-third of Na⁺ and Cl⁻ inputs are via food. Cloacal water losses are large because of the high water content (ca. 88%) of the excreta. Nasal secretions account for elimination of about 95% of ingested Na⁺ and Cl⁻, and 80% of K⁺ input, using only one-fourth of the water input (ca. 12 ml/kg day). Concentrations of Na⁺, K⁺, and Cl⁻ in nasal secretions of fed marine iguanas were about 1,170 mM, 280 mM, and 1,330 mM, respectively. Plasma electrolyte concentrations are high in field animals (201 mM Na⁺, 153 mM Cl⁻) and decline when the animals are held without food or water. Marine iguanas "fed" only seawater to maintain weight regulated plasma Na⁺, whereas plasma K⁺ declined.

Binding of magnesium and chloride ions to human hemoglobin A. Mg2+ concentrations in solutions simulating red cell conditions.

Ultrafiltration and direct determination of [Mg2+] by ion exchange were used to study the binding of Mg2+ and Cl- to isoionic human hemoglobin. A value of 58.8 +/- 1.7 l/mol was determined for the volume of hydrated hemoglobin from ultrafiltration of hemoglobin solutions containing 0.15-0.8 M glucose. In solutions with 5.7 mmol hemoglobin, 150 mmol KCl and 0.5-3.5 mmol MgCl2/l total water, 0.6 mol and 2 mol Cl- were bound/mol oxygenated and deoxygenated hemoglobin respectively. A value of about 11 l/mol was determined for the association constant of Mg2+ to hemoglobin monomer. Free Mg2+ concentrations were measured in hemoglobin solutions containing KCl, MgCl2, ATP and D-glycerate-2,3-bisphosphate at concentrations close to those of red cells. The experiments yielded 0.65 mmol/l free Mg2+ after oxygenation and 0.82 mmol/l after deoxygenation. The data indicate that only small changes of free Mg2+ levels in red cells are caused by physiological changes of pO2.

Affinity Labeling of the Escherichia coli Aspartate‐β‐Semialdehyde Dehydrogenase with an Alkylating Coenzyme Analogue

3-Chloroacetylpyridine-adenine dinucleotide phosphate (clac3PdADP+, a NADP+ alkylating analogue, irreversibly inactivates aspartate-beta-semialdehyde dehydrogenase with pseudo-first-order kinetics. NADP+ and NADPH, but not the substrate, protected the enzyme from inactivation. The pH dependence of the inactivation kinetics was determined. Incorporation of 1 mol cl[14C]-ac3PdADP+/dimer totally inactivates the enzyme. Successive alkylation by the coenzyme analogue and by the substrate analogue, L-2-amino-4-oxo-5-chloropentanoic acid, was studied. After inactivation with the coenzyme analogue, no incorporation of the substrate analogue was detected. However, when the enzyme was first inactivated with the substrate analogue, the protein could subsequently be alkylated with the coenzyme analogue. The binding of NADP+ and NADPH to aspartate-beta-semialdehyde dehydrogenase was determined by fluorescence.