Organometallic chemistry of diphosphazanes. Rhodium(I) complexes of RN(PX2)2 (R = C6H5; X = OC6H5, OC6H4Br−p, R = CH3; X = OC6H5)

Reactions of [Rh(COD)Cl]₂ with the ligand RN(PX₂)₂ (1: R = C₆H₅; X = OC₆H₅) give mono- or disubstituted complexes of the type [Rh₂(COD)Cl₂{ν²−C₆H₅N(P(OC₆H₅)₂)₂}] or [RhCl{ν²−C₆H₅ N(P(OC₆H₅)₂)₂ }]₂ depending on the reaction conditions. Reaction of 1 with [Rh(CO)₂Cl]₂ gives the symmetric binuclear complex, [Rh(CO)Cl{μ−C₆H₅N(P(OC₆H₅)₂)₂} ₂, whereas the same reaction with 2 (R = CH₃; X = OC₆H₅) leads to the formation of an asymmetric complex of the type [Rh(CO)(μ−CO)Cl{μ−CH₃N(P(OC₆H₅)₂)₂}₂ containing both terminal and bridging CO groups. Interestingly the reaction of 3 (R = C₆H₅, X = OC₆H₄Br−p with either [Rh(COD)Cl]₂ or [Rh(CO)₂Cl]₂ leads only to the formation of the chlorine bridged binuclear complex, [RhCl{ν²−C₆H₅N(P(OC₆H₄Br−p)₂)₂}]₂. The structural elucidation of the complexes was carried out by elemental analyses, IR and ³¹P NMR spectroscopic data.     

Crystal structure, neutron vibrational spectroscopy, and DFT calculations of Li2B12H12 · 4H2O

The crystal structure of Li₂B₁₂H₁₂ · 4H₂O has been determined by X-ray powder diffraction and confirmed by a combination of neutron vibrational spectroscopy and first-principles calculations. The solvent-free analog of this compound (Li₂B₁₂H₁₂) has recently attracted interest as a putative intermediate in the decomposition of LiBH₄. Li₂B₁₂H₁₂ · 4H₂O appears in the initial stages of Li₂B₁₂H₁₂ synthesis from LiBH₄ and B₁₀H₁₄     

Distributions of H+,K+-ATPase and Cl–,HCO3–-ATPase in micromere-derived cells of sea urchin embryos

In cultured cells derived from isolated micromeres of sea urchin eggs, H+,K+-ATPase activity, which became detectable simultaneously with the initiation of spicule formation, was localized in the plasma membrane and the microsome fractions. Activities of marker enzymes for plasma membrane, 5'-nucleotidase, Na+,K+-ATPase, and adenylate cyclase, were found to be high in the plasma membrane fraction. Considerable activity of rotenone-insensitive NADPH-cytochrome c reductase, a marker enzyme for microsome, was detectable in the microsome fraction. These fractions exhibited barely any appreciable activity of markers for the other organellae. H+,K+-ATPase in plasma membrane probably mediates H+ release from the cells, in which H+ is produced in overall reaction to form CaCO3, the main component of spicules, from Ca2+, CO2 and H2O. Cl-,HCO3(-)-ATPase activity was also found in these two fractions before and after the initiation of spicule formation. After initiation, the skeletal vacuole fraction was obtained from subcellular structures containing spicules. Considerable activity of Cl-,HCO3(-)-ATPase was observed in this fraction, which exhibited a weak activity of UDP-galactose: N-acetylglucosamine galactosyltransferase, a marker enzyme for Golgi body. Cl-,HCO3(-)-ATPase in the skeletal vacuole membrane probably mediates HCO3- transport into the vacuoles to supply HCO3- for spicule formation.     

Blue-light-induced pH changes associated with NO3−, NO2− and Cl− uptake by the green alga Monoraphidium braunii

In M. braunii, the uptake of NO₃⁻ and NO₂⁻ is blue-light-dependent and is associated with alkalinization of the medium. In unbuffered cell suspensions irradiated with red light under a CO₂-free atmosphere, the pH started to rise 10s after the exposure to blue light. When the cellular NO₃⁻ and NO₂⁻ reductases were active, the pH increased to values of around 10, since the NH₄⁺ generated was released to the medium. When the blue light was switched off, the pH stopped increasing within 60 to 90s and remained unchanged under background red illumination. Titration with H₂SO₄ of NO₃⁻ or NO₂⁻ uptake and reduction showed that two protons were consumed for every one NH₄⁺ released. The uptake of Cl⁻ was also triggered by blue light with a similar 10 s time response. However, the Cl⁻ -dependent alkalinization ceased after about 3 min of blue light irradiation. When the blue light was turned off, the pH immediately (15 to 30 s) started to decline to the pre-adjusted value, indicating that the protons (and presumably the Cl⁻) taken up by the cells were released to the medium. When the cells lacked NO₃⁻ and NO₂⁻ reductases, the shape of the alkalinization traces in the presence of NO₃⁻ and NO₂⁻ was similar to that in the presence of Cl⁻, suggesting that NO₃⁻ or NO₂⁻ was also released to the medium. Both the NO₃⁻ and Cl⁻-dependent rates of alkalinization were independent of mono- and divalent cations.     

Photophosphorylation in Scenedesmus in vivo: O2 evolution, ATP pools and transients, and phosphate binding during photoreduction of NO3−, NO2− and CO2

The relation between light-induced electron transport with NO₃^?, NO₂^? or CO₂ as acceptors, ATP pools and transients in dark-light-dark transitions, and phosphate uptake was examined in phosphorus-starved cells of Scenedesmus obtusiusculus Chod. Net O₂ evolution at saturating light was around 6 μmol × (mg chlorophyll × h)^?1 in the absence of any acceptor, but reached average rates of 21, 65 and 145 μmol × (mg chlorophyll × h)^?1 upon additions of 5 mM KNO₃, KNO₂ and KHCO₃, respectively. The apparent rate of photophosphorylation in transition experiments was only a few percent of the rate calculated from CO₂-dependent O₂ evolution. Blocking non-cyclic electron transport with DCMU inhibited phosphate assimilation, but acceleration of non-cyclic electron flow by addition of NO₃^? or NO₂^? did not stimulate phosphate assimilation as compared to the situation without an acceptor. A functional non-cyclic system might primarily be needed for an efficient shuttle transfer of ATP from the chloroplast to the cytoplasm. An inhibition of the non-cyclic system due to lack of reducible substrates accelerates the cyclic system and thus indicates a regulation mechanism between the two systems.     

Ln2(O2CCH2PO3)2(H2O)3 · H2O (Ln = La, Pr, Nd, Sm): Layered lanthanide phosphonoacetates containing two-dimensional -Ln-O- linkages

Four novel isostructural lanthanide phosphonate compounds with formula Ln₂(O₂CCH₂PO₃)₂(H₂O)₃ · H₂O [Ln = La (1), Pr (2), Nd (3), Sm (4)] have been prepared through hydrothermal reactions of phosphonoacetate acid and lanthanide nitrates. All show layered structures made up of {LnO₉} polyhedra and {CPO₃} tetrahedra with the lattice water molecules locating between the layers. Within the layer, chains of edge-sharing {LnO₉} polyhedra are connected via corner-sharing by phosphonate oxygens forming a two-dimensional -Ln-O- linkage. Thermal analyses and XRD measurements reveal that the framework structures can be maintained up to 400 °C.     

Effect of prostaglandins A1, A2, B1, B2, E2 and F2α on human umbilical cord vessels

The effect of six naturally occurring prostaglandins on isolated umbilical arteries and veins has been studied. All six prostaglandins had a constricting effect on the umbilical vessels. On the umbilical artery preparations the potencies in decreasing order were A₂>B₂>F_2α>B₁>E₂>A₁. Prostaglandin B₂ was more potent than PGA₂ on the umbilical vein. Polyphloretin phosphate (PPP) antagonised the constricting effect of all six prostaglandins without altering responses to 5-hydroxytryptamine.     

Syntheses, characterizations and crystal structures of two lead(II) diphosphonates: Pb2[NH(CH2PO3)2] · 2H2O and Pb3[HO2C(CH2)3NH(CH2PO3)2]2 · 2H2O

Hydrothermal reactions of lead(II) acetate and HO₂C(CH₂)₃N(CH₂PO₃H₂)₂ at 170 and 140 °C, respectively, resulted in two different lead diphosphonates, namely, Pb₂[NH(CH₂PO₃)₂] · 2H₂O (1), in which the butyric acid moiety of the HO₂C(CH₂)₃N(CH₂PO₃H₂)₂ has been cleaved and a novel layered compound, Pb₃[HO₂C(CH₂)₃NH(CH₂PO₃)₂]₂ · 2H₂O (2). Their crystal structures have been determined by single crystal X-ray diffraction. In compound 1, the interconnection of the lead(II) ions by bridging amino-diphosphonate ligands leads to the formation of a 3D network. Compound 2 features an unusual triple-layer structure with the non-coordinated butyric acid moieties as pendant groups between the layers.     

Energy-dependent endocytosis in erythrocyte ghosts. IV. Effects of Ca2+, Na+ + K+, and 5'-adenylylimidodiphosphate

The requirement of actual splitting of ATP for endocytosis in erythrocyte ghosts has been confirmed by use of the ATP analog, 5'-adenylylimidodiphosphate. (AMP-P(NH)P. This compound, in which the oxygen connecting the β and γ phosphorus atoms was replaced by an NH group, did not cause endocytosis nor was it a substrate for ATPase activity. AMP-P(NH)P was a competitive inhibitor both for the endocytosis and the Mg²⁺-ATPase activities. The $\text{K}{}_{\mathrm{<mtext>1</mtext>}}$ of AMP-P(NH)P for Mg²⁺-ATPase activity was 2.0 · 10^?4 M and, while the $\text{K}{}_{\mathrm{<mtext>m</mtext>}}$ of ATP for this activity was also 2.0 · 10^?4 M indicating nearly identical affinities of ATP and AMP-P(NH)P for the active site. ADP, or ADP plus orthophosphate, did not cause endocytosis, showing that endocytosis was not due to binding of the products of ATP hydrolysis. Sodium or potassium ion or ouabain had no effect on endocytosis, which eliminated the possibility of involvement of the Na⁺, K⁺ ATPase in the endocytosis process. Calcium could not be substituted for magnesium; rather it inhibited endocytosis at the concentration of 1 · 10^?3 M. EGTA relieved the inhibitory effect of Ca, which indicated that the binding of calcium to the membrane was reversible. These experimental results reaffirm the conclusion that ATP must be split to engender endocytosis under these conditions. Some characteristic parameters of the hemoglobin-fre porcine erythrocyte ghosts were studied in order to characterize the system more adequately.     

Determination of 6-keto-PGF1α, 2,3-dinor-6-keto-PGF1α, thromboxane B2, 2,3-dinor-thromboxane B2, PGE2, PGD2 and PGF2α in human urine by gas chromatography—negative ion chemical ionization mass spectrometry

A method for quantification of 6-keto-PGF_1α, 2,3-dinor-6-keto-PGF_1α, TXB₂, 2,3-dinor TXB₂, PGE₂, PGD₂ and PGF_2α in human urine samples, using gas chromatography—negative ion chemical ionization mass spectrometry, is described. Deuterated analogues were used as internal standards. Methoximation was carried out in urine samples which were subsequently applied to phenylboronic acid cartridges, reversed-phase cartridges and thin-layer chromatography. The eluents were further derivatized to pentafluorobenzyl ester trimethylsilyl ethers for final quantification by gas chromatography—mass spectrometry. The overall recovery was 77% for tritiated 6-keto-PGF_1α and 55% for tritiated TXB₂. Urinary levels of prostanoids were determined in a group of six volunteers before and after intake of the thromboxane synthase inhibitor Ridogrel, and related to creatinine clearance.     

Hydrothermal syntheses and structures of a novel zincophosphite, [C6N2H18] · [Zn3(HPO3)4]

A novel three-dimensional organically templated zincophosphite, [C₆N₂H₁₈] · [Zn₃(HPO₃)₄], was synthesized under milder hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction, differential thermal-thermogravimetric analysis, powder X-ray diffraction, ³¹P MAS NMR spectrum, and IR spectroscopy. It crystallizes in the monoclinic system, space group C2/c with cell parameters: a = 8.7820(4) Å, b = 14.9417(7) Å, c = 15.4943(5) Å, β = 92.940(2)°, and Z = 4. The structure consists of a network of strictly alternating ZnO₄ tetrahedra and pseudo-pyramid, forming 4-membered ring chains. The structure has a 4.8.16-net and 8- and 16-membered ring channels where completely protonated N,N,N′,N′-tetramethylenediamine cations are encapsulated. The structure is stabilized by template-to-framework hydrogen bonding. In phosphites system, this compound possesses extra-large-pores.     

A novel approach and a fully automated microcomputer-based system to study kinetics of NO−3, NO−2, and NH+4 transport simultaneously by intact wheat seedlings

Abstract A 16-channel fully automated microcomputer-based system was designed to measure the disappearance of NO^?₃ NO^?₂ and NH⁺₄ simultaneously from uptake solutions. The analyses were done using high-performance liquid chromatography. Statistical procedures were used to generate transport kinetics and interactions amongst NO^?₃, NO^?₂ and NH⁺₄ by intact wheat seedlings. The simultaneous analysis of NO^?₃, NO^?₂ and NH⁺₄ at real-time; the accommodation of varying sampling intervals; the capability to study up to 16 experimental units in synchrony; and the analysis of the data with a microcomputer, make this a powerful system for studying transport kinetics and interactions.     

Interactions between growth, Cl− and Na+ uptake, and water relations of plants in saline environments. I. Slightly vacuolated cells

Abstract. Slightly vacuolated cells, i.e. microalgae and meristematic cells of vascular plants, maintain low Cl^? and Na⁺ concentrations even when exposed to a highly saline environment. The factors regulating the internal ion concentration are the relative rate of volume expansion, the membrane permeability to ions, the electrical potential, and the active ion fluxes. For ion species which are not actively transported, a formula is developed which relates the internal concentration to the rate of expansion of cell volume, the permeability of membranes to that ion, and the electrical potential. For example, when the external concentration of Cl^? is high, and Cl^? influx is probably mainly passive, the formula predicts that rapid growth keeps the internal Cl^? concentration lower than that in a non-growing cell with the same electrical potential; this effect is substantial if the plasmalemma has a low permeability to Cl^?. For ion species which are actively transported, the rate of pumping must be considered. For instance Na⁺ concentrations are kept low mainly by an efficient Na⁺ extrusion pump which works against the electric field across the membrane. The requirement for Na⁺ extrusion is related to the external Na⁺ concentration, the rate of expansion of cell volume, the membrane permeability, and the electrical potential. It is possible that microalgae have a more positive electrical potential than many other plant cells; if so, requirements for high rates of active Na⁺ extrusion will be lower. The required rates of Na⁺ extrusion are lower during rapid growth, provided that the permeability of the plasmalemma to Na⁺ is low. The energy required for the regulation of Cl^? and Na⁺ concentrations is low, especially in rapidly expanding cells where Na⁺ extrusion requires only 1–2% of the energy normally produced in respiration. The exclusion of these ions, however, must be accompanied by the synthesis of enough organic compounds to provide adequate osmotic solutes for the increases in volume accompanying growth. This process reduces the substrates available for respiration and synthesis of cell constituents, but the reduction is not prohibitively large—even for cells growing in 750 mol m^?3 NaCl, the carbohydrate accumulated as osmotic solute is only 10% of that consumed in respiration.     

Synthesis, spectroscopic and structural characterization of adducts of stoichiometry CuX:dppe (1:2) (X = I, ClO4, BH4, O3SCF3, SCN, dppe = Ph2P(CH2)2PPh2)

Syntheses and spectroscopic features (IR, NMR and ESI MS) are reported for five 1:2 adducts of CuX with dppe (X = I, ClO₄, NCS, O₃SCF₃ (tfs) BH₄; dppe = Ph₂P(CH₂)₂PPh₂). ESI MS and ³¹P NMR spectroscopy indicate that these species dissociate in solution yielding free diphosphine and 3:2 species. A single crystal X-ray structure determination has been carried out on Cu(dppe)₂NCS defining a four-coordinate complex of the form [(P,P′-dpex)M(P-dpex)X] for M = Cu, the thiocyanate being N-bound; the ionic [Cu(P,P′-dppe)₂]tfs has also been structurally characterized.     

Water-filled pseudo-nanotubes in Ag11.60H0.40[Cr(C2O4)3]4 · 15H2O: Synthesis, characterization and X-ray structure

The title compound, Ag_11.60H_0.40[Cr(C₂O₄)₃]₄ · 15H₂O (1) precipitates from aqueous solution as a dark violet solid in which silver ions are partially replaced by protons, and it crystallizes in an unusual structure with water-filled one-dimensional pseudo-nanotubes.