Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The interaction of factor Va with phospholipid monolayers was studied using alternating current polarography. For these studies a hanging mercury drop electrode is positioned in contact with the monolayer at the air-monolayer interface. Factor Va introduced into the aqueous subphase beneath the monolayer caused alterations in the capacitance of the circuit. When factor Va was introduced beneath monolayers containing 13-25% mole fraction phosphatidylserine (PS), 87-75% mole fraction phosphatidylcholine (PC), a significant capacitance increase occurred, which is interpreted to be the result of the penetration of the factor Va molecules through the monolayer. No penetration or associated capacitance changes were observed with monolayers composed of pure PC or pure PS. Polarography experiments were also conducted with the electrode placed in the aqueous subphase to measure the binding of factor Va to pure PS monolayers. This approach has allowed detection of factor Va (at nM concentrations) adsorption to a pure PS monolayer. Thus the membrane adsorption process can be distinguished from factor Va penetration through the monolayer. These results suggest that there are two types of interaction of the factor Va molecule with PS-containing monolayers. The interaction with the PS component of the monolayer is essential for binding the factor Va (at nM concentrations) that occurs by surface adsorption. For mixed PC/PS monolayers, PS adsorption is followed by penetration of the protein through the membrane.
 ...
PMID:Electrostatic and hydrophobic interactions are involved in factor Va binding to membranes containing acidic phospholipids. 829 40

The influence of the thiols L-cysteine (CYS), glutathione (GSH), and 2,3-dimercapto-1-propanesulfonate (DMPS) on the binding and transport of inorganic mercury (Hg2+) in luminal (brush-border) and basolateral membrane-vesicles isolated from the kidneys of rats was studied using radiolabeled mercury (203HgCl2). Membrane-vesicles were exposed to 1, 10, or 100 microM Hg2+ in the presence or absence of a 3:1 or 10:1 mole-ratio of CYS, GSH, or DMPS relative to Hg2+. Equilibration of mercury with the membrane-vesicles occurred very rapidly, essentially being complete within 5 sec. By 60 sec, binding accounted for 87-97% of intravesicular Hg2+ in the absence of exogenous thiols. All three thiols significantly reduced the fraction of binding, with DMPS being the most effective agent. CYS enhanced the association of Hg2+ with luminal membrane-vesicles relative to that when Hg2+ was added alone, suggesting that conjugation of Hg2+ with CYS promotes the transport of low concentrations of Hg2+. In contrast, an excess of either GSH or DMPS relative to Hg2+ interfered significantly with both the binding and transport of Hg2+ into either luminal or basolateral membrane-vesicles. In summary, the present study is the first to describe the association of Hg2+ with renal luminal and basolateral membrane-vesicles. Evidence was obtained for the involvement of a Hg2+-CYS conjugate as a mechanism by which Hg2+ uptake and binding to luminal membranes occur and for an inhibitory effect of GSH and the chelator DMPS with regard to Hg2+ uptake and binding, demonstrating that extracellular thiols can modulate significantly the renal accumulation of Hg2+.
 ...
PMID:Binding of mercury in renal brush-border and basolateral membrane-vesicles. 925 64

The adherence of hematite (alpha-Fe(2)O(3)) particles onto mercury electrodes in water-ethanol mixtures has been studied by counting on optical microscope images, obtaining also the effective charge by electrophoretic measurements. The number of attached particles, when the ethanol content is small, decreases as the ethanol concentration increases. At an ethanol mole fraction near 0.2, the number of particles goes through a minimum and then increases with ethanol concentration. When the electrode potential is modified, curves of the number of particles vs ethanol mole fraction with the same shape are found, but they cross each other. The experimental behavior can be explained based on the dependence of particle/solution, metal/solution, and metal/particle interaction energies on the solvent composition. Copyright 1999 Academic Press.
 ...
PMID:Adhesion of Colloidal Hematite onto Mercury in Water-Ethanol Media. 1041 73

The reaction mechanism of the oxidative degradation of polyvinyl alcohol (PVA) by the photochemically enhanced Fenton reaction was studied using a homogeneous (Fe2+(aq) + H2O2) and a heterogeneous reaction system (iron(III)-exchanged zeolite Y+ H2O2). In the homogeneous Fenton system, efficient degradation was observed in a batch reactor, equipped with a medium pressure mercury arc in a Pyrex envelope and employing 80% of the stoichiometric amount of H2O2 required for the total oxidation of PVA and a concentration ratio as low as I mole of iron(II) sulfate per 20 moles of PVA sub-units (C2H40). Model PVA polymers of three different molecular weights (15,000, 49,000 and 100,000 g mol(-1)) were found to follow identical degradation patterns. Strong experimental evidence supports the formation of supermacromolecules (MW: 1-5 x 10(6) g/mol) consisting of oxidized PVA and trapped iron(III) at an early reaction stage. Low molecular weight intermediates, such as oxalic acid, formic acid or formaldehyde were not found during PVA degradation in the homogeneous Fenton system, and we may deduce that the manifold of degradation reactions is mainly taking place within the super-macromolecules from which CO2 is directly released. However, in the heterogeneous Fenton system, the reaction behavior was found to be distinctly different: a decrease of the molecular weights of all three tested monodisperse PVA samples was observed by the broadening of the GPC-traces during irradiation, and oxalic acid was formed. The results lead to the mechanistic hypothesis that during the heterogeneous Fenton process, the cleavage of the PVA-chains may occur at random positions, the reactive centres being located inside the iron(III)-doped zeolite Y photocatalysts.
 ...
PMID:Degradation of polyvinyl alcohol (PVA) by homogeneous and heterogeneous photocatalysis applied to the photochemically enhanced Fenton reaction. 1169 68

1. Addition of 2 moles of mersalyl, mercuric chloride, p-chloromercuribenzoate (PCMB), or methyl mercury hydroxide per mole of hemoglobin greatly reduces heme-heme interactions (n), yet these substances have quite different effects on the oxygen affinity (-log p(50)). Mersalyl and mercuric chloride at this concentration each increase the oxygen affinity, while PCMB and methyl mercury have little or no effect on the oxygen affinity. These effects are primarily associated with the binding of -SH groups, and are largely reversed on the addition of glutathione. -SH groups do not appear to be responsible for the Bohr effect. 2. Evidence is presented for the belief that the two hemes of each half-molecule of horse hemoglobin are situated on either side of a cluster of-SH groups. 3. The mechanism of interaction between the hemes is discussed. It is concluded that the reorganization of the protein architecture which accompanies oxygenation plays a central role in this interaction, in agreement with the views of Pauling and Wyman.
 ...
PMID:Sulfhydryl groups and the structure of hemoglobin. 1329 56

A deep repository for permanent storage of mercury will be designed and built in Sweden. The preferred chemical state for mercury in such a repository would be the sulphide HgS (cinnabar), which is a highly insoluble and the dominating natural mercury mineral. The possible formation of HgS from HgO or Hg(0) by reaction with a sulphur source (S, FeS or FeS(2)) is discussed from thermodynamic considerations, and pe-pH-diagrams are constructed by using the computer code MEDUSA to illustrate under which conditions HgS would dominate. Calculations of the speciation (PHREEQE) under varying conditions (S/Hg-ratios, presence of chloride) are given. Long-term laboratory experiments are performed, where the formation of HgS from the basic components is demonstrated (after mixing under various conditions and storage at room temperature for up to 3 years). The feasibility of HgS-formation with time in a geologic repository under conditions representative of deep granitic bedrock (calcium-bicarbonate buffered to pH 7-8.5) is discussed, as well as effects of alkaline conditions (concrete environment, pH 10.5-12.5). Formation of soluble polysulphides is not expected as long as the S/Hg mole ratio is within 1-1.3 and pH is below 10.5-11. Concrete should be used with caution. Suitable ballast materials could be introduced that would reduce porewater-pH that otherwise would be above 12.
 ...
PMID:Formation of cinnabar--estimation of favourable conditions in a proposed Swedish repository. 1650 96

A method has been developed for the histochemical demonstration of phospholipase B (lysolecithinase) of rat tissues. The enzyme attacks lysolecithin with liberation of 1 mole of glycerylphosphorylcholine and 1 mole of fatty acid. The recommended procedure involves use of 6-10 micro frozen sections, fixed in cold calcium-formol and incubated at 37 degrees C in Tris buffered medium at pH 6.6 containing 2.2 X 10(-3) M lysolecithin and 1% cobalt acetate. The fatty acid liberated by enzymatic hydrolysis is trapped as a cobalt precipitate and is then converted to a black-brown precipitate by treatment with dilute ammonium sulfide in cold isotonic saline. Equivalent amounts of fatty acid and glycerylphosphorylcholine are recovered by extraction and analysis of the incubated sections and of the incubation medium, thus proving that lysolecithin hydrolysis occurs under the proposed reaction conditions. Staining is reduced by treating the sections with copper ions, mercury compounds, alcohols, acetone and by heating at 60 degrees C prior to incubation with substrate. Lowering of the pH of the incubation medium has similar effect. These findings are interpreted as evidence of the enzymatic nature of the reaction. Cells exhibiting a positive staining are found in the lamina propria of the intestinal villi and crypts, in the red pulp of the spleen and in the interstitial tissue of lung, liver and thymus. Similar elements are present in bone marrow smears and in leukocyte preparations obtained by peritoneal lavage. The morphologic and staining characteristics of these cells correspond to those of the eosinophilic leukocytes. Physical and chemical agents (x-irradiation, corticosteroids) which sharply decrease the number of eosinophils also reduce the number of cells shown histochemically to hydrolyze lysolecithin. A correspondent diminution of phospholipase B activity of homogenates of the same tissues can be shown in vitro. Differences in tissue distribution and chemical properties distinguish the phospholipase B from less specific esterases and lipases.
 ...
PMID:Histochemical demonstration of phospholipase B (lysolecithinase) activity in rat tissues. 1712 89

The ammonia solvated mercury(II) ion has been structurally characterized in solution by means of EXAFS, (199)Hg NMR, and Raman spectroscopy and in solid solvates by combining results from X-ray single crystal and powder diffraction, thermogravimetry, differential scanning calorimetry, EXAFS, and Raman spectroscopy. Crystalline tetraamminemercury(II) perchlorate, [Hg(NH3)4](ClO4)2, precipitates from both liquid ammonia and aqueous ammonia solution, containing tetraamminemercury(II) complexes. The orthorhombic space group ( Pnma) imposes C s symmetry on the tetraamminemercury(II) complexes, which is lost at a phase transition at about 220 K. The Hg-N bond distances are 2.175(14), 2.255(16), and 2 x 2.277(9) A, with a wide N-Hg-N angle between the two shortest Hg-N bonds, 122.1(7) degrees , at ambient temperature. A similar distorted tetrahedral coordination geometry is maintained in liquid ammonia and aqueous ammonia solutions with the mean Hg-N bond distances 2.225(12) and 2.226(6) A, respectively. When heated to 400 K the solid tetraamminemercury(II) perchlorate decomposes to diamminemercury(II) perchlorate, [Hg(NH3)2](ClO4)2, with the mean Hg-N bond distance 2.055(6) A in a linear N-Hg-N unit. The mercury atoms in the latter compound form a tetrahedral network, connected by perchlorate oxygen atoms, with the closest Hg...Hg distance being 3.420(3) A. The preferential solvation and coordination changes of the mercury(II) ion in aqueous ammonia, by varying the total NH 3:Hg(II) mole ratio from 0 to 130, were followed by (199)Hg NMR. Solid [Hg(NH 3)4](ClO4)2 precipitates while [Hg(H2O)6](2+) ions remain in solution at mole ratios below 3-4, while at high mole ratios, [Hg(NH3)4](2+) complexes dominate in solution. The principal bands in the vibrational spectrum of the [Hg(NH3)4](2+) complex have been assigned.
 ...
PMID:Coordination chemistry of mercury(II) in liquid and aqueous ammonia solution and the crystal structure of tetraamminemercury(II) perchlorate. 1826 Jun 25

We report on the application of a commercially available mercury analyzer, which is based on vapour generation of Hg(0) by NaBH(4) reduction and atomic absorption detection, to the quantification and characterization of -SH groups and its application to wine samples. The behaviour of Hg(II) and thiol-Hg(II) (RS-Hg) complexes at nanomolar level (RS=l-cysteine, dl-penicillamine, N-acetyl penicillamine, glutathione, cysteinylglycine, homocysteine) has been studied following their reduction with alkaline NaBH(4) to give Hg(0). In the absence of thiol-Hg(II) is quantitatively converted to Hg(0) by stoichiometric amount of NaBH(4) (reaction ratio 1/4mole NaBH(4)/mole Hg), while the complete reduction of Hg(II)-thiol complexes to Hg(0) requires molar excess of NaBH(4) up to six orders of magnitude, depending on the type of complex and on the pK(a) of the thiolic group. Under an appropriate excess of reductant, Hg(II) and its thiol complexes are not distinguishable giving the same response. These properties allow the discrimination of Hg(II) from Hg(II)-thiol complexes without any preliminary separation and the quantification of thiol groups. Instrumental detection limits are as low as 2.5pg, permitting sample dilution, therefore, minimizing the risk of possible interferences occurring with complex real matrices. The method has been applied to quantification of thiol groups in wine samples. Comparison with results obtained by HPLC coupled to atomic fluorescence detection confirmed the promising potentialities of the method.
 ...
PMID:Determination of thiolic compounds as mercury complexes by cold vapor atomic absorption spectrometry and its application to wines. 1837 31

Liquid ammonia, trialkyl phosphites, and especially trialkylphosphines, are very powerful electron-pair donor solvents with soft bonding character. The solvent molecules act as strongly coordinating ligands towards mercury(ii), interacting strongly enough to displace halide ligands. In liquid ammonia mercury(ii) chloride solutions separate into two liquid phases; the upper contains tetraamminemercury(ii) complexes, [Hg(NH(3))(4)](2+), and chloride ions in low concentration, while the lower is a dense highly concentrated solution of [Hg(NH(3))(4)](2+) entities, ca. 1.4 mol dm(-3), probably ion-paired by hydrogen bonds to the chloride ions. Mercury(ii) bromide also dissociates to ionic complexes in liquid ammonia and forms a homogeneous solution for which (199)Hg NMR indicates weak bromide association with mercury(ii). When dissolving mercury(ii) iodide in liquid ammonia and triethyl phosphite solvated molecular complexes form in the solutions. The Raman nu(I-Hg-I) symmetric stretching frequency is 132 cm(-1) for the pseudo-tetrahedral [HgI(2)(NH(3))(2)] complex formed in liquid ammonia, corresponding to D(S) = 56 on the donor strength scale. For the Hg(ClO(4))(2)/NH(4)I system in liquid ammonia a (199)Hg NMR study showed [HgI(4)](2-) to be the dominating mercury(ii) complex for mole ratios n(I(-)) : n(Hg(2+)) > or = 6. A large angle X-ray scattering (LAXS) study of mercury(ii) iodide in triethyl phosphite solution showed a [HgI(2)(P(OC(4)H(9))(3))(2)] complex with the Hg-I and Hg-P bond distances 2.750(3) and 2.457(4) A, respectively, in near tetrahedral configuration. Trialkylphosphines generally form very strong bonds to mercury(ii), dissociating all mercury(ii) halides. Mercury(ii) chloride and bromide form solid solvated mercury(ii) halide salts when treated with tri-n-butylphosphine, because of the low permittivity of the solvent. A LAXS study of a melt of mercury(ii) iodide in tri-n-butylphosphine at 330 K resulted in the Hg-I and Hg-P distances 2.851(3) and 2.468(4) A, respectively. The absence of a distinct I-I distance indicates flexible coordination geometry with weak and non-directional mercury(ii) iodide association within the tri-n-butylphosphine solvated complex.
 ...
PMID:Structure of solvated mercury(II) halides in liquid ammonia, triethyl phosphite and tri-n-butylphosphine solution. 1841 56


<< Previous 1 2 3 4 5 Next >>