Addition Of KF Research Articles

The etching characteristics of phosphate glass track detectors

The etching characteristics of phosphate glasses of types VG-13 and PSK-50 have been studied under various etching conditions using relativistic heavy ions 238 U, 197 Au and 139 La. The addition of KF to HBF 4 solution markedly increases the sensitivity of VG-13. The effects of concentration of KF on s (= v T / v G ) were studied. For La ions ( Z/β=63 ), s was measured to be about 1.15.

ChemInform Abstract: Potassium Dioxonium Hexafluoroaluminate.

AbstractThe title compound precipitates after addition of KF to a 38% HF solution containing dissolved aluminum.

ChemInform Abstract: A Rapid and Direct Electrochemical Synthesis of K2(MoOF5)

Abstractis achieved by oxidation of a sacrificial Mo anode in a solution containing 20% HF followed by the addition of KF.

Calorimetric studies of the thermal denaturation of cytochrome c peroxidase

Two endotherms are observed by differential scanning calorimetry during the thermal denaturation of cytochrome c peroxidase at pH 7.0. The transition midpoint temperatures (tm) were 43.9 +/- 1.4 and 63.3 +/- 1.6 degrees C, independent of concentration. The two endotherms were observed at all pH values between 4 and 8, with the transition temperatures varying with pH. Precipitation was observed between pH 4 and 6, and only qualitative data are presented for this region. The thermal unfolding of cytochrome c peroxidase was sensitive to the presence and ligation state of the heme. Only a single endotherm was observed for the unfolding of the apoprotein, and this transition was similar to the high-temperature transition in the holoenzyme. Addition of KCN to the holoenzyme increases the midpoint of the high-temperature transition whereas the low-temperature transition was increased upon addition of KF. Binding of the natural substrate ferricytochrome c to the enzyme increases the low-temperature transition by 4.8 +/- 1.3 degrees C but has no effect on the high-temperature transition at pH 7. The presence of cytochrome c peroxidase decreases the stability of cytochrome c, and both proteins appear to unfold simultaneously. The results are discussed in terms of the two domains evident in the X-ray crystallographic structure of cytochrome c peroxidase.

A rapid and direct electrochemical synthesis of K 2[MoOF 5

A single-step synthesis of K 2[MoOF 5] has been made by the oxidation of a sacrificial molybdenum anode in a solution containing 20% HF followed by the addition of KF. This electrosynthesis represents a significant improvement over the existing methods.

Fluorination with elemental fluorine: Synthesis of 2,2-difluoropleuromutilin

Reaction of the Diazoketone 1 derived from the tricyclic diterpene Pleuromutilin with elemental Fluorine in CFCl 3/CHCl 3 at −60° C led to the formation of several fluorinated-products ( 2 – 4 ). Using pure CFCl 3 as solvent did not result in any isolable product, while the addition of solid KF to the reaction solution increased the yield markedly. Reacting 1 with liquid HF in CH 2Cl 2 at −70° C gave mainly the 2-Fluoropleuromutilin 3 together with the corresponding α,β-unsaturated ketone 5 which reacts further to yield the rearrangement product 6 . ▪

31P-nmr studies of the effect of various metals on substrate binding to yeast enolase

The 31P nuclear magnetic resonance (nmr) spectra of product (phosphoenolpyruvate) and substrate (2-phosphoglycerate) binding to 1:1 molar ratios ot yeast enolase were obtained as functions of the level of various metal ions. Levels sufficient to produce substrate and product binding but not catalysis ( 1 equivalent/subunit), produced shifts (with respect to 86% H 3PO 4) to lower shielding of ca. 30 ppm in the case of Co 2+, 5–8 ppm in the case of Mg 2+, and 2–3 ppm in the case ofCa 2+, but virtual obliteration in the case of Mn 2+. The effects of Mn 2+ and Co 2+ are consistent with a close approach of the metal ions to the phosphate groups. The effects of the physiological cofactor and optimum activator Mg 2+ and the nonactivator Ca 2+ are interpreted as indicating different degrees of distortion of the R-O-P bond angle in the two metal-enzyme-substrate complexes. Levels of Mg 2+ sufficient for optimal or near optimal catalysis (2 equivalents/subunit) produce shifts to higher shielding in the 31P resonances of both substrate and product. These shifts are intermediate between those in the presence of 1 equivalent/subunit and those of the free ligands. Addition of a second equivalent of Ca 2+ produces a slight shift to lower shielding of the phosphoenolpyruvate resonance and a small shift to higher shielding in the resonance for 2-phosphoglycerate. Similar levels of Co 2+ eliminate the resonances for both substrate and product. These effects are interpreted as arising from direct coordination between substrate-dependent metal ion binding and the phosphate esters. Higher levels of Ca 2+, Mg 2+, or Co 2+ or addition of KF, all of which inhibit enzyme activity, have only minor effects on the spectra. The spectrum of inorganic phosphate, a competitive inhibitor, was also examined. KF strongly enhances binding, as does excess Mg 2+, and the binding is accompanied by a chemical shift to lower shielding of ca 2 ppm. This is not due to formation of a magnesium-fluorophosphate complex, consistent with the findings of other workers.

Ultraviolet spectra of Tl+, Pb2+ and Bi3+ probe ions in molten fluoride media

Although the orbital-expansion (nephelauxetic) parameter, h, for fluoride is usually assigned a value of 0.8, frequencies of the 1S0→3P1 transition obtained from the ultraviolet absorption spectra of Tl+, Pb2+ and Bi3+ probe ions in molten LiF–NaF–KF (46.5:11.5:42) indicate values of 1.38, 1.33 and 1.09, respectively. These are consistent with the absorption spectra of thin films of the four halides of each of the metal ions. It is shown that Tl+, Pb2+ and Bi3+ are capable of detecting the reduction in electron-donor power of fluoride when it is modified by polarising cations such as boron(III) or phosphorus(V) as in molten alkali-metal tetrafluoroborate or hexafluorophosphate. Addition of KF to molten alkali-metal tetra-fluoroborate results in a gradual replacement of the polarised fluorides by F– ions in the coordination sphere of the probe ion rather than the direct formation of the discrete fluoro-complex of Tl+, Pb2+ or Bi3+; substitution is virtually complete at KF contents < 20%.

Selective flocculation of hematite in the hematite-quartz-ferric ion-polyacrylic acid system. Part 1, activation and deactivation of quartz

This investigation has shown that quartz can be activated for polyacrylic acid adsorption by hydrolyzing metal cations, similar to activation in flotation. Detailed experiments on activation phenomena with ferric ions have been performed. The flocculation of activated quartz can be prevented by suitable additions of disodium EDTA, sodium hexametaphosphate or potassium fluoride. Selective flocculation of hematite with polyacrylic acid from a hematite/quartz mixture can be achieved in the pH range 3 to 9, but the process is not selective in the presence of ferric ions. Suitable additions of EDTA or KF are particularly successful in preventing quartz activation by ferric ions and the facilitating selective flocculation of hematite in artificial mixtures of quartz and hematite.

Specificity for Nicotinamide Adenine Dinucleotide by Nitrate Reductase from Leaves

Preliminary work revealed that nitrate reductase in crude extracts prepared from leaves of certain corn genotypes as well as soybeans could utilize NADPH as well as NADH as the electron donor. Isoelectric focusing and diethylaminoethyl cellulose chromatography confirmed previous findings that NADH and NADPH activities could not be separated, which suggests the involvement of a single enzyme. Nitrate reduction with both cofactors varies with plant species, plant age, and assay conditions. The ability of the nitrate reductase from a given genotype to utilize NADPH was associated with the amount of NADPH-phosphatase in the extract. While diethylaminoethyl cellulose chromatography of plant extracts separated nitrate reductase from the bulk (90%) of the phosphatase and caused a decrease in the NADPH activity, the residual level of phosphatase was sufficient to account for the apparent NADPH nitrate reductase activity. Addition of KH(2)PO(4) and KF, inhibitors of NADPH-phosphatase activity in in vitro assays, caused a drastic reduction or abolishment of NADPH-mediated nitrate reductase activity but were without effect on NADH nitrate reductase activity. It is concluded that NADPH-nitrate reduction, in soybean and certain corn genotypes, is an artifact resulting from the conversion of NADPH to NADH by a phosphatase and that the enzyme in leaf tissue is NADH-dependent (E.C.1.6.6.1).

Adenyl cyclase of cell nuclei isolated from rat ventral prostate

Cell nuclei isolated from rat ventral prostate synthesize significant amounts of adenosine 3′,5′-monophosphate (cyclic AMP) from ATP in the presence of Mg 2+ or Mn 2+. The nuclear adenyl cyclase activity is stimulated by the addition of KF or certain hormones such as glucagon, epinephrine, or adenocorticotropin. It is suggested that certain hormonal regulations of the concentrations of cyclic nucleotides may occur in various intracellular compartments of the cells, such as nuclei, to influence local biochemical activities.