Ligand Of Na Research Articles

Expanding the Boxmi Ligand Family: Synthesis and Application of NON and NSN Ligands.

Two synthetic strategies for a new family of neutral NON ligands featuring a "bis(oxazolinylmethylidene)isobenzofuran" framework (boxman) are reported. A Pd-mediated cyclization reaction forming the isobenzofuran core constitutes the key reaction in the eight-step synthetic route to the nonbackbone-methylated target compound H,Rboxman. In contrast, the introduction of two additional methyl groups provides stereochemical control during backbone construction and thereby access to the methylated derivative Me,Rboxman, which was synthesized in five steps and improved yields. In addition, the synthetic sequence was transferred to the thio analogue, providing access to the NSN ligand H,Rboxmene. Subsequent complexation experiments with iron and cobalt chloride precursors afforded the four-coordinated chlorido complexes Me,RboxmanMCl2 (R = Ph, iPr; M = Fe, Co) and established the boxman family as trans-chelating, bidentate bis(oxazoline) ligands. Application of the latter in the nickel(II)- and zinc(II)-catalyzed α-fluorination of β-ketoesters and oxindoles (up to 98% yield and 94% ee) demonstrated their suitability for enantioselective catalysis.

Research Progress of Marinobufagenin and Salt-Sensitive Hypertension

Salt-sensitive hypertension is a special type of hypertension. Because of its special pathogenesis and clinical features, it has attracted more and more attention in recent years. Marinobufagenin is a kind of endogenous digitals-like substance, which is the unitary ligand of Na + /K + ATPase widely distributed in human and animal. Marinobufagenin mediates water sodium retention, increases blood pressure, and interferes myocardial and vascular fibrosis and other pathologic mechanisms by blocking Na + /K + ATPase and various signaling pathways, which playes an importent role in the occurrence and development of salt-sensitive hypertension. This article hlights recent advances of the relation between marinobufagenin and salt-sensitive hypertension.

Serine 26 in the PomB subunit of the flagellar motor is essential for hypermotility of Vibrio cholerae.

Vibrio cholerae is motile by means of its single polar flagellum which is driven by the sodium-motive force. In the motor driving rotation of the flagellar filament, a stator complex consisting of subunits PomA and PomB converts the electrochemical sodium ion gradient into torque. Charged or polar residues within the membrane part of PomB could act as ligands for Na+, or stabilize a hydrogen bond network by interacting with water within the putative channel between PomA and PomB. By analyzing a large data set of individual tracks of swimming cells, we show that S26 located within the transmembrane helix of PomB is required to promote very fast swimming of V. cholerae. Loss of hypermotility was observed with the S26T variant of PomB at pH 7.0, but fast swimming was restored by decreasing the H+ concentration of the external medium. Our study identifies S26 as a second important residue besides D23 in the PomB channel. It is proposed that S26, together with D23 located in close proximity, is important to perturb the hydration shell of Na+ before its passage through a constriction within the stator channel.

Palladium complexes based on tridentate pyrazolyl-ligands: Synthesis, structures and use in Suzuki cross-coupling reactions

The reaction of [PdCl(Me)(cod)] (cod = 1,5-cyclooctadiene) with tridentate bis(pyrazolyl) ligands affords the alkyl-palladium(II) complexes [Pd(CH 3)(NZN)][BF 4] ( 1, NZN = 1,1′-(2,2′-oxybis(ethane-2,1-diyl)bis(3,5-dimethyl-1H-pyrazole); 2, NZN = bis[2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl]sulfane) in good yield. Compounds 1– 2 were characterized by elemental analysis, multinuclear NMR spectroscopy, and X-ray structural analysis. Single crystal X-ray structural analyses indicate that the complexes are monomeric and the palladium center resides in a slightly distorted square planar environment. Furthermore, despite their intrinsic similarity, the NON and NSN ligands adopt different coordination modes around the palladium metal center. Additionally, the [PdCl 2(NON)] ( 3) was shown to be an efficient catalyst precursor for the coupling of aryl bromides and iodides with arylboronic acids, esters and borate salts.

Synthesis, structure, and thermal properties of two honeycombs like three-dimensional complexes composed by cobalt salt and asymmetric ligand

Two new coordination polymers {[Co 2(BTC)(OH)(H 2O) 2] 2 · 2H 2O} n ( 1) (BTC = 1,2,4-benzenetricarboxylate) and {Co 2(NA) 4(H 2O)} n ( 2) (NA = nicotinate) had been synthesized under the hydrothermal condition and characterized by elemental analyses, IR, and the single crystal X-ray diffraction. Complexes 1 is a new three-dimensional network composed by tetranuclear Co cluster. It can be seen constructed by two-dimensional Co–O inorganic layers supported by BTC ligands. Complex 2 is also a three-dimensional network. To our surprise, Complex 1 and 2 both contain honeycomb-like structure surrounded by Co clusters and BTC, NA ligands. We think it is difficult to construct such structures with asymmetry ligand such as BTC and NA. Furthermore, the thermal stability properties of the two complexes are studied.

Synthesis, structure, and luminescent property of one mixed-valence Cu–halide complex constructed from pyridine-3-carboxylate

In this article, a Cu(I)-halide complex [Cu(II) 3Cu(I) 4(NA) 6Br 4] n (complex 1) (NA = pyridine-3-carboxylate) has been synthesized under hydrothermal reaction conditions. Complex 1 is a two-dimensional layer structure composed by trinuclear Cu(II) unit and tetranuclear Cu(I) unit connected by NA ligands. Complex 1 exhibits strong luminescent property at room temperature.

Syntheses and photoluminescent properties of two uranyl-containing compounds with extended structures

Two new uranyl-organic compounds [(UO 2) 3O(OH) 3(NA) 2] − · H 3O + ( 1) (HNA = nicotinic acid) and (UO 2) 2(phen) 2(BTEC) ( 2) (H 4BTEC = 1,2,4,5-benzenetetracarboxylic acid, phen = 1,10-phenanthroline) have been prepared under hydrothermal conditions. X-ray single-crystal structure analyses reveal that compound 1 consists of infinite helical polyoxouranium ribbons built up from trinuclear [(UO 2) 3O(OH) 3] + units and NA ligands, whereas compound 2 is composed of two-dimensional sheets joined together through π–π interactions. Both compounds show intense emission under excitation of UV light.

Crystal structure of [triaqua(salicylato)(nicotinamide)zinc(II)] salicylate.

vitamin leads to a loss of copper from the body, known as pellagra disease. The nicotinamide derivative, N,Ndiethylnicotinamide (DENA), is an important respiratory stimulant. A structure determination of the title compound was undertaken in order to determine the ligand properties of NA and salicylate ligands. The title compound was prepared from the reaction of Zn(2HO-C6H5COO)2·8(H2O) (1.46 g, 3.00 mmol) and NA (0.18 g, 1.50 mmol) in water (80 ml). The mixture was filtered and set aside for crystallization at ambient temperature for a few days. The results of an X-ray structure determination are given in Tables 1 – 4. The title compound contains a mononuclear Zn(II) complex in which there are three water molecules, one NA ligand and one salicylate ligand. The one salicylate moiety in the compound does not act as a ligand, but is incorporated into the crystal lattice by hydrogen bonds. Although the zinc atom has five coordination, close contact of the O5 atom [Zn...O5 = 2.687(6)A] may cause the zinc atom to have six coordination. The five coordination around Zn(II) can be described as a distorted trigonal bipyramid or a distorted square pyramid. Further information can be obtained by estimating the structural index, τ,1 which represents the relative amount of 1241 ANALYTICAL SCIENCES OCTOBER 2001, VOL. 17 2001 © The Japan Society for Analytical Chemistry

Regulation of sodium/potassium ATPase activity: impact on salt balance and vascular contractility.

Na+,K+-ATPase distributes ions between the intracellular and extracellular space and is responsible for total-body sodium homeostasis. The activity of this ion pump is regulated by catecholamines and peptide hormones; by the ligand of Na+,K+-ATPase, ouabain; and by direct interaction with cytoskeleton proteins. This review summarizes recent advances in the field of short-term regulation of Na+,K+-ATPase and the implications of these advances for the regulation of blood pressure. Renal Na+,K+-ATPase activity is bidirectionally regulated by natriuretic and antinatriuretic hormones, and a shift in the balance between these forces may lead to salt retention and hypertension. Dopamine plays a key role in this interactive regulation. By inhibiting vascular Na+,K+-ATPase activity, an excess of circulating ouabain may increase calcium concentration in vascular cells and lead to increased vascular contractility. Finally, mutations in cytoskeleton proteins may stimulate renal Na+,K+-ATPase activity by way of protein/protein interaction and lead to salt retention and hypertension. Abnormalities in the systems regulating Na+,K+-ATPase should be explored further in the search for the multiple causes of essential hypertension.

Crystal Structure of trans-Diaquabis(3-aminobenzoato-O)-bis(nicotinamide-N)cobalt(II)

ciency of this vitamin leads to a loss of copper from the body, known as pellagra disease. The nicotinic acid derivative, N,N-diethylnicotinamide (DENA), is an important respiratory stimulant. The title compound was prepared by dissolving CoSO4·7(H2O) (2.81 g, 0.01 mol) and NA (2.44 g, 0.02 mol) in water (75 ml) and sodium-3-aminobenzoate (3.18 g, 0.02 mol) in water (25 ml) and then adding the solutions. The mixture was set aside for crystallization at ambient temperature for a few days. A structure determination of the title compound was undertaken in order to determine the ligand properties of NA and benzoate ligands, and to compare the coordination geometries when the NA ligands are substituted for water in complexes [Co(p-O2NC6H4COO)2(H2O)4] (I) and [Co(p-H2NC6H4COO)2(H2O)4] ( ). The title compound is a monomeric complex with cobalt in a center of symmetry. All ligands are monodentate and the O atoms of each water molecule and benzoate group form a slightly distorted square-planar coordination around the Co atom, which is completed to a Jahn-Teller distorted octahedron by the pyridine N atoms of NA at 2.153(3)A (Fig. 2). There are intraand inter-molecular hydrogen bonds between the nicotinamide N3 and O4 atoms [N O 2.236(6)A], and the non-coordinated O3i atom and the water O2 atom [O O 2.583(6)A, symmetry code: (i) –x, –y, –z], respectively. Similar hydrogen bonds are observed in (I) [2.59 A], ( ) [2.592(3) A], [Co(C7H5O2)2(C6H6N2O)2(H2O)2] ( ) [2.580(2)A] and [Co(C7H4NO4)2(C6H6N2O)2(H2O)2] ( ) [2.634(5)A]. The configuration around the Co atom is given by the torsion angles (Table 4). The Co atom is out of the C1, O1, O3 plane by 0.645(2)A. The dihedral angle between the carboxyl group and the phenyl ring is 24.1(4) . The corresponding ones are 13.0(2) and 23.7(3) in complexes ( ) and ( ), respectively. Most 1043 ANALYTICAL SCIENCES OCTOBER 1999, VOL. 15

Covalent structures of BmK AS and BmK AS-1, two novel bioactive polypeptides purified from Chinese scorpion Buthus martensi Karsch

Complete amino acid sequences of two novel bioactive polypeptides, each containing 66 amino acid residues, BmK AS and BmK AS-1 purified from the venom of Chinese scorpion Buthus martensi Karsch, have been determined by Edman sequencing and mass spectrometry on native proteins, reduced and S-carboxymethylated proteins and their peptides obtained after cleavage with proteolytic enzymes. Sequence analysis showed 86.4% structural identity between BmK AS and BmK AS-1 and also a high sequence similarity between BmK ASs and AaH IT4, a unique anti-insect toxin and a ligand of Na + channels obtained from Sahara scorpion A. australis Hector, but poor sequence homology between BmK ASs and those of the known α-, β-type and long-chain insect-selective type scorpion neurotoxins. The positions of four disulfide bridges in BmK AS-1 were established as Cys-12 and Cys-62, Cys-16 and Cys-37, Cys-23 and Cys-44, and Cys-27 and Cys-46, which are the same as those in α- and β-scorpion neurotoxins. These results suggest that BmK ASs and AaH IT4 may form a new group sharing similar structural and functional properties in the family of scorpion neurotoxic polypeptides.

Characterization and subtype identification of the Na+-H+exchanger in bovine corneal epithelium

Amiloride analogues with N5-alkyl substitutions are specific high-affinity ligands for the Na(+)-H+ exchanger in various tissues. As a means to characterize the Na(+)-H+ exchanger in the bovine corneal epithelium, we determined the binding properties of [3H] methylisobutylamiloride (MIA) to a fraction enriched in plasma membrane from this tissue. [3H]MIA bound to these membranes in a time, -a temperature-, and -a pH-dependent manner. The binding was optimal at 4 degrees C and at pH 8.5 and it reached equilibrium at 60 min. Under these conditions, specific binding, which was inhibitable by excess unlabeled MIA, was about 85%. Scatchard analysis of this specific binding revealed a single saturable binding component with a Kd of 61 nM and a Bmax of 271 pmoles/mg protein. Inhibition of [3H]MIA specific binding by amiloride analogues showed the following order of potency: MIA > dimethylamiloride (DMA) > benzamil > amiloride. Na+ did not compete with MIA for binding. The effectiveness of clonidine, an alpha 2 agonist, and cimetidine, an H2 receptor antagonist, as inhibitors of Na(+)-H+ exchange activity was also determined because these compounds are used to distinguish between the exchanger subtypes. At concentrations higher than those needed for receptor interaction, clonidine was more effective than cimetidine in decreasing MIA binding. The activity of Na(+)-H+ exchanger, which was measured as the uptake of 22Na+ in the presence of an outwardly directly H+ gradient, was also inhibited by DMA, benzamil and amiloride with the same order of potency as obtained in the binding studies.(ABSTRACT TRUNCATED AT 250 WORDS)