Aluminum Fluoride Complexes Research Articles

Kinetic and spectroscopic characterization of fluorescent ribose-modified ATP analogs upon interaction with skeletal muscle myosin subfragment 1.

The interaction of fluorescent ATP analog 2'(3')-O-[N-[2-[3-(5-fluoresceinyl)thioureido]-ethyl]carbamoyl]adenosine 5'-triphosphate (FEDA-ATP) with rabbit skeletal myosin subfragment 1 (S1) and acto-S1 was studied. This and related ATP analogs are potentially useful for determination of the ATPase activity of single myosin filaments using fluorescence microscopy [Sowerby et al. (1993) J. Mol. Biol. 234, 114-123]. However, it is necessary that such analogs mimic ATP in their kinetics of turnover. The apparent second-order association rate constants for FEDA-ATP binding to S1 and for FEDA-ATP-induced dissociation of acto-S1 are about 4 times slower than those for ATP. As with ATP, the hydrolysis step is fast, so that the M.FEDA-ADP.P(i) complex is the major steady-state intermediate. The turnover rate is the same for the 2' and 3' FEDA-ATP derivatives and similar to that of ATP itself. The dissociation rate constant for FEDA-ADP from S1 is identical to that for ADP. Actin-activated turnover is comparable for both FEDA-ATP and ATP. The corresponding rhodamine and sulfoindocyanine, Cy3.18 (Cy3), derivatives also appear to be reasonable analogs. FEDA-ATP binding leads to a 25-40% reduction in fluorescein fluorescence. Spectral properties of the bound nucleotide were explored by trapping FEDA-ADP as its aluminum fluoride complex. The fluorescence quenching is a consequence of a reduction in both absorbance and excited-state lifetime, but there is little change in spectral shape.

Reagents that activate GTP‐binding proteins trigger the acrosome reaction in human spermatozoa

The acrosome reaction is a specialized exocytotic process. In the mouse there is compelling evidence that receptor-mediated activation of GTP-binding proteins by factors in the zona pellucida of oocytes is a central event in the acrosome reaction. Several reagents are able to affect GTP-binding proteins directly, bypassing the receptor-ligand step for activation. We have assessed the effect of several of these compounds on human spermatozoa, monitoring cell vitality and the acrosome reaction simultaneously using the triple-stain technique. GTP gamma S and aluminium fluoride complexes promote sperm activation very efficiently; amphiphilic peptides capable of activating G(o) and Gi, also elicit the acrosome reaction. The results indicate that activation of heterotrimeric GTP-binding proteins is sufficient to trigger acrosome exocytosis in human spermatozoa.

X-ray Structures of the Myosin Motor Domain of Dictyostelium discoideum Complexed with MgADP.cntdot.BeFx and MgADP.cntdot.AlF4-

The three-dimensional structures of the truncated myosin head from Dictyostelium discoideum myosin II complexed with beryllium and aluminum fluoride and magnesium ADP are reported at 2.0 and 2.6 A resolution, respectively. Crystals of the beryllium fluoride-MgADP complex belong to space group P2(1)2(1)2 with unit cell parameters of a = 105.3 A, b = 182.6 A, and c = 54.7 A, whereas the crystals of the aluminum fluoride complex belong to the orthorhombic space group C222(1) with unit cell dimensions of a = 87.9 A, b = 149.0 A, and c = 153.8 A. Chemical modification was not necessary to obtain these crystals. These structures reveal the location of the nucleotide complexes and define the amino acid residues that form the active site. The tertiary structure of the protein complexed with MgADP.BeFx is essentially identical to that observed previously in the three-dimensional model of chicken skeletal muscle myosin subfragment-1 in which no nucleotide was present. By contrast, the complex with MgADP.AlF4- exhibits significant domain movements. The structures suggest that the MgADP.BeFx complex mimics the ATP bound state and the MgADP.AlF4- complex is an analog of the transition state for hydrolysis. The domain movements observed in the MgADP.AlF4- complex indicate that myosin undergoes a conformational change during hydrolysis that is not associated with the nucleotide binding pocket but rather occurs in the COOH-terminal segment of the myosin motor domain.

Mg 2+-dependent phosphatase as an inhibitory mediator of the nonselective cation current induced by aluminum fluoride in guinea-pig chromaffin cells

Internal administration of the G protein activator, guanosine-5′- o-(3-thiotriphosphate) (GTPγS) or aluminum fluoride (AlF) complex, produce an inward nonselective cation current ( I NS) at −55 mV. This current was rapidly diminished under conditions of high intracellular Mg 2+ ([Mg 2+] = 979 μM), the half decay time ( T 1 2 ) being 80 to 100 s. As [Mg 2+] in AlF solutions decreased from 400 to 12 μM, the maximum amplitude of AlF-induced I NS became larger and the current was diminished more slowly. The AlF I NS in the presence of 12 μM Mg 2+ reversed polarity at about + 9 mV, irrespective of the extent of decline. Bath application of muscarine produced a sustained I NS was rapidly diminished. Addition of vanadate (0.5 mM) to 979 μM Mg 2+-containing AlF solution mimicked the effects of low Mg 2+ solution. Inversely, addition of alkaline phosphatase (40 units/ml) to 12 μM Mg 2+ AlF solution reproduced the effects of high Mg 2+ solution. It is suggested that AlF complex deactivates I NS through facilitating an apparent activity of Mg 2+-dependent phosphatase.

Phosphatase is responsible for run down, and probably G protein-mediated inhibition of inwardly rectifying K+ currents in guinea pig chromaffin cells.

The mechanism of G protein-mediated inhibition of an inwardly rectifying K+ current (IIR) in adrenal chromaffin cells was investigated using the whole-cell version of the patch clamp technique. In case of recording with use of ATP-containing patch solution, the IIR was well maintained; otherwise, it ran down within 15 min. This run down was not prevented by replacement with adenylyl-imidodiphosphate, a nonhydrolysable analogue of ATP, but was markedly reduced by the addition to the ATP-free solution of 1 microM calyculin A, a specific inhibitor of serine/threonine phosphatase 1 (PP1) and 2A (PP2A). The addition of alkaline phosphatase to the ATP-containing solution facilitated run down of the current, and application of 100 microM H-7, a general kinase inhibitor, reversibly suppressed IIR. These results taken together suggest that inwardly rectifying K+ channels are under the influence of kinase and phosphatase without external signals. Infusion of nonhydrolysable analogues of GTP, guanosine-5'-O-(3-thiophosphate) (GTP gamma S) or guanylyl-imidodiphosphate, through the pipette produced little inward current at -55 mV, but completely inhibited IIR within approximately 5 or 6 min in all cells tested in the presence of 12 microM Mg2+ inside the cell. In contrast, infusion of aluminum fluoride (AlF) complex, another GTP binding (G) protein activator, consistently produced large inward currents, but did not alter IIR noticeably for 15 min in 17% of the cells tested. In the other cells, the inhibition of IIR developed slowly after long latent periods. This inhibitory potency of AlF was not enhanced by an increase in Mg2+ concentrations. Subtraction of the current-voltage relationship before from that noted during the generation of inward current by AlF complex revealed that the inward current diminished progressively with hyperpolarizations, as is the case with a nonselective cation current (INS) induced by a muscarinic agonist. Thus, AlF complex seems to be potent with the generation of INS, but not with IIR inhibition. The addition of 3 microM calyculin A significantly retarded the IIR inhibition by GTP gamma S, whereas that of 1 microM okadaic acid, another inhibitor of PPI and PP2A, markedly prevented the decline of IIR by AIF complex. Our observations suggest that the low potency of AlF complex in inhibiting IIR may be due to interference with phosphatase activity and that the activation of G protein suppresses IIR, probably by enhancing the apparent activity of phosphatase, which may explain run down of the current.

Aluminum fluoride interactions with troponin C

The increasing interest in the metal ion aluminum fluoride and beryllium fluoride complexes as phosphate analogs in the myosin ATPase reaction and in muscle fiber studies prompted the examination of their interactions with the regulatory system of troponin and tropomyosin. In this work, the effects of these metal ion analogs on the spectral properties of the Ca(2+)-binding subunit of troponin, troponin C (TnC), were examined. In contrast to beryllium fluoride which did not change the spectral properties of TnC, aluminum fluoride binding induced an increase in both the alpha-helicity and the tyrosine fluorescence of TnC and exposed a hydrophobic region on this protein for fluorescent probe binding. Aluminum fluoride also reduced the Ca2+ and/or Mg(2+)-induced changes on TnC. These results indicate a direct interaction of aluminum fluoride with TnC and merit consideration in designing muscle fiber experiments with this phosphate analog.

Identification of Aluminum Scale With the Aid of Synthetically Produced Basic Aluminum Fluoride Complexes

Summary Aluminum scaling can be a problem following HF acidizing. In this paper, a series of synthetic aluminum scales was prepared and identified. The aluminum compounds of a field scale were identified with similar procedures. Recent field work showed that the use of acetic acid in the HF acidizing sequences significantly decreased scaling. The role of acetic acid is discussed on the basis of laboratory support of these field data.

Amelioration of aluminium toxicity in wheat by fluoride

summaryThe deleterious effects of aluminium in the rhizosphere on growth, root morphology, ion uptake, and stomatal conductance in wheat (Triticum aestivum L.) were prevented or attenuated by the inclusion of fluoride in the growth medium; the more fluoride present relative to the concentration of aluminium, the greater the alleviation. Results support the conclusion that the ameliorative effects of fluoride were due to reductions in the concentration of the rhizotoxic trivalent cation (Al3+) through the formation of aluminium–fluoride complexes that are neither phytotoxic nor readily translocated from roots to shoots.

The Effects of Fluoride Complexes in Wet Limestone Flue Gas Desulfurization.

In the wet limestone flue gas desulfurization process (FGD), aluminum/fluoride complexes (AIFx) are sometimes formed in liquid phase and inhibit the dissolution of the limestone, thereby reducing the desutfurization performance.To clarify the mechanism of this phenomenon, bench-scale tests simulating the operating conditions of the FGD were conducted.The results obtained indicate that the formation of AIFx depends on such factors as fly ash loading and aluminum content in limestone. Earlier papers have not discussed the latter factor sufficiently. The authors also observed that magnesium/fluoride complex (MgF+) potentially inhibits the dissolution of limestone. As a countermeasure to AIFx, it was demonstrated that the addition of strong alkali during operation can decompose AIFx and prevent inhibition of limestone dissolution.The decomposition of AIFx was directly detected by 19F FT-NMR.Equilibrium model calculations theoretically support the decomposition of AIFx by a strong alkali added to an absorbent with pH kept within an appropriate range.

Characterization of fluorine-, aluminum-, silicon-, and phosphorus-containing complexes in wet-process phosphoric acid using nuclear magnetic resonance spectroscopy

Wet-process phosphoric acid is one product of the reaction between phosphate rock and sulfuric acid. The limiting step in this process occurs when the acid is filtered from the reaction slurry, which also contains calcium sulfate (gypsum). The acid-soluble impurities present in the phosphate rock (e.g., fluorine, silicon, and aluminum) form complexes in wet-process acid which can alter the optimum size and habit of gypsum crystals, thereby reducing the filtration rates. Fluorine-containing complexes are strongly suspected of being potent modifiers of the crystal habit of gypsum. However, the identities of the complexes responsible for the habit modification have not been established. The identities of the complexes formed in phosphoric acid (28% P2O5) containing additions of fluorine (HF and H2SiF6) and aluminum [Al(NO3)3 · 9H2O or AlF3 · 9H2O] were established in this study by using fluorine-19 (19F) and phosphorus-31 (31P) nuclear magnetic resonance (NMR) spectroscopies. Peaks due to aluminum fluoride, fluorosilicate, and fluoroaluminum phosphate complexes were observed in the NMR spectra recorded from these solutions. In addition, the19F and31P NMR spectra of wet-process acids were recorded. These spectra contained peaks assigned to the hexafluorosilicate ion (major species), along with aluminum fluoride and fluoroaluminum phosphate complexes (minor species).

Effect of fluoride ions on the corrosion of aluminium in sulphuric acid and zinc electrolyte

The effect of fluoride ions on the corrosion of aluminium in sulphuric acid and zinc electrolyte has been investigated through thermodynamic analysis and corrosion experiments. The solution chemistry of aluminium, zinc, and iron in aqueous solution in the absence and in the presence of fluoride ions was studied with the construction of the Eh-pH diagrams for the Al−F−H2O, Zn−F−H2O and Fe−F−H2O systems at 25°C. In the presence of fluoride ions, aluminium can form a series of aluminium-fluoride complexes depending on the fluoride concentration and pH whereas zinc and iron can form soluble or insoluble metal-fluoride complex species only at relatively high fluoride concentration and at higher pH values. Experimental results show that in the presence of fluoride ions, the corrosion of pure aluminium in sulphuric acid is due to uniform dissolution and the reaction rate depends on the fluoride concentration. In zinc electrolyte containing fluoride ions, zinc deposits onto the pure aluminium substrate spontaneously and the amount of deposited zinc also depends on the fluoride concentration. On the other hand, the presence of iron in the Al−Fe alloy accelerates the corrosion of aluminium in H2SO4 and zinc electrolyte significantly and prevents the deposition of zinc on the aluminium surface. The effect of fluoride ions on zinc adherence to the aluminium is also discussed.

Characterization of the Aluminum and Beryllium Fluoride Species Bound to F-actin and Microtubules at the Site of the γ-Phosphate of the Nucleotide

Aluminum fluoride and beryllium fluoride complexes have previously been shown to bind tightly to F-ADP-actin and GDP-microtubules in competition with Pi and to mimic the XDP-Pi transient state of the polymerization. The structure of the bound complexes is investigated here in further detail. Using a fluoride ionspecific electrode, the number of fluoride atoms per aluminum or beryllium atom in the bound complex could be determined. The results indicate that AlF−4 and either BeF2(OH)−•H2O or BeF‒3•H2O are the tightly bound species in both F-actin and microtubules. The dependences of the binding on pF and pH are consistent with this conclusion. The possible geometries of aluminum and beryllium fluorides in the γ-phosphate subsite of the nucleotide are discussed in correlation with the catalytic mechanism of nucleotide hydrolysis.

Fluorine variations in welsh streams and soil waters

Stream and soil water fluoride concentrations, for acidic and acidifying Welsh catchments subject to various forms of land use, vary between 0.02 and 0.22 mg l −1. Highest concentrations occur within the lower soil zone waters, although stream water concentrations are also high under the condition where atmospheric fluorine inputs are high. Speciation studies are presented to show that aluminium fluoride complexes make up a significant proportion of the total aluminium and fluorine concentrations in solution. It is concluded that, for both toxicological and solubility studies, fluorine measurements need to be made to assess the degree of fluoride complexation in waters associated with acid-impacted Welsh catchments.

Stabilization of microtubules by inorganic phosphate and its structural analogs, the fluoride complexes of aluminum and beryllium [Erratum to document cited in CA108(23):200420x

Stabilization of microtubules by inorganic phosphate and its structural analogs, the fluoride complexes of aluminum and beryllium [Erratum to document cited in CA108(23):200420x

RecA protein-promoted cleavage of LexA repressor in the presence of ADP and structural analogues of inorganic phosphate, the fluoride complexes of aluminum and beryllium

Complexes formed from A13+ or Be2+ and fluoride inhibit the single-stranded DNA-dependent ATPase activity of RecA protein. In contrast, poly(dT)-RecA-ADP complexes, which are inactive for cleavage of LexA protein, become fully active in the presence of AlF4- or BeF3- ions. These data suggest that fluoride complexes of aluminum and beryllium (called herein X) convert RecA-ADP complexes, which bind weakly to single-stranded DNA, into RecA-ADP-X complexes, which bind tightly to single-stranded DNA, the ADP-X moiety behaving as a nonhydrolyzable analogue of ATP. We propose that AlF4- and BeF3- ions act as analogues of inorganic phosphate by binding to the site of the gamma-phosphate of ATP on RecA-ADP complexes, hence mimicking the single-stranded DNA-RecA-ADP-Pi transition state. We conclude that the elementary reaction that switches RecA protein from a high affinity single-stranded DNA binding state to a low affinity single-stranded DNA binding state is not ATP hydrolysis per se but Pi release.

Stabilization of microtubules by inorganic phosphate and its structural analogs, the fluoride complexes of aluminum and beryllium

In order to elucidate how the elementary reactions of GTP cleavage and subsequent inorganic phosphate (Pi) release, which accompany microtubule assembly, regulate microtubule dynamics, the effect of Pi and of its structural analogues AlF4- and BeF3- on the stability of GDP-microtubules has been investigated. Inorganic phosphate binds to microtubules with a low affinity (KD = 25 mM) and slows down the rate of GDP-subunit dissociation by about 2 orders of magnitude. AlF4- and BeF3- exhibit phosphate-like effects with 1000-fold higher affinity. Evidence has been obtained for direct binding of BeF3- to microtubules with a stoichiometry of 1 mol of BeF3- per mole of GDP-subunit and an equilibrium dissociation constant of 12-15 microM. AlF4- and Pi compete for this site. Phosphate analogues abolish oscillatory polymerization kinetics and slow down microtubule turnover at steady state. In view of these results, we propose that Pi and its structural analogues bind to the site of the gamma-phosphate of GTP in the E site and reconstitute a GDP-Pi-microtubule, from which tubulin subunits dissociate very slowly. We therefore understand that, following GTP cleavage on microtubules, Pi release in the medium is accompanied by a structural change resulting in a large destabilization of the polymer. A cap of slowly dissociating GDP-Pi-subunits prevents depolymerization of the microtubule GDP-core at steady state. The similarity with the actin system [Carlier, M.-F., & Pantaloni, D. (1988) J. Biol. Chem. 263, 817-825] is underlined.

The existence of AlF 4− in aqueous solution and its relevance to phosphorylase reactions

The discovery that trace amounts of aluminium are necessary for fluoride to exert its biological influence has lead to numerous investigations into the nature of the active fluoroaluminate complex. Many workers have postulated AlF 4 − to be this species. In this study we show that in the presence of inorganic phosphate or ADP, fluoride is not able to complex aluminium(III), but rather the species [Al(PO 4) 2H] 2− and [Al(ADP)OH] − are formed. In the absence of completing ligands, 27Al NMR reveals that octahedral, hydrated aluminium fluoride complexes are formed, the most likely one being [AlF 4(H 2O) 2] −.

Sintering of kaolinite with ammonium fluoride

The present work represents a study of the influence of ammonium fluoride on the thermal behaviour of kaolinite by using a derivatograph. The sintering of kaolinite with ammonium fluoride was found to be complicated. Different products of sintering are obtained, depending on the temperature and the amount of ammonium fluoride. They were identified microscopically and by using a Siemens Crystalloflex diffratometer. These include an ammonium aluminium fluoride complex, cryptohalite, aluminium fluoride, mullite, topaz and corundum. The DTA curves (using kaolinite and ammonium fluoride mixes of ratio 1:1) indicate the formation of the ammonium aluminum fluoride complex and cryptohalite at 120–280°C and the appearance of aluminium fluoride, topaz and mullite at 640°C. The intensive formation of topaz takes place at 750°C and its subsequent dissociation at 940°C with corundum formation. The very small endothermic peak at 1010°C represents the formation of mullite. In experiments using mixes of kaolinite—ammonium fluoride in the ratios 1:1 and 1:1.3 the end-product of sintering consists of corundum and mullite. When using mixes of the ratio 1:1.7, aluminium fluoride constitutes the main composition of the end-product.

Differential scanning calorimetry study of fluoride complexes of chromium, iron, boron, aluminum, indium and phosphorus

The enthalpy and temperature of the sublimation, dissociation and transition of nitrosyl fluoride or nitryl fluoride-chromium, iron, boron, aluminum, indium and phosphorus fluoride adducts were determined from DSC measurements. A closed-cell DSC technique was employed for this purpose and to postulate possible reaction mechanisms of the dissociation.

Determination of small amounts of fluorine in the presence of aluminum, using the fluoride ion electrode

A new simple techique for the microdetermination of fluorine in the presence of aluminum was obtained by using the fluoride ion electrode. Procedures are as follows ;Aluminum fluoride complexes were deeomosed in alkali (pH>12) and the liberated aluminum was masked with oxine. The pH and total ionic strength were adjusted with TISAB, and fluorine determination was carried out with no extraction of the aluminum-oxine complex and free oxine.The calibration curve showed a linearity down to less than 0.1 ppm (5.3×1O-6M) of fluorine in the presence of 4 ppm of aluminum and oxine, which is as good as measurements obtained in the absence of aluminum.Recovery of 1 ppm of fluorine was relatively good-about 95%-, even in the presence of 200 ppm of aluminum. Good recovery of fluorine added to artificial cryolite was also found.