potassium-bromide and potassium-fluoride

Auxin regulates diverse processes involved in plant growth and development. AUX1 is the first identified and most widely investigated auxin importer, and plays an important role in root gravitropism and the development of lateral root and root hair. However, the regulation of auxin transport by AUX1 is still not well understood. In this study, we examined the effect of metal ions on AUX1 transport function and found that the activity could be specifically stimulated four times by K

Topics: Arabidopsis; Arabidopsis Proteins; Biological Transport; Bromides; Fluorides; Gene Expression; Hot Temperature; Indoleacetic Acids; Mutagenesis, Site-Directed; Potassium Chloride; Potassium Compounds; Potassium Iodide; Protein Stability; Proteolysis; Recombinant Proteins; Schizosaccharomyces; Signal Transduction

Here we report on the polarization dependent nonresonant second harmonic generation (SHG) measurement of the interfacial water molecules at the aqueous solution of the following salts: NaF, NaCl, NaBr, KF, KCl, and KBr. Through quantitative polarization analysis of the SHG data, the orientational parameter D (D = /) value and the relative surface density of the interfacial water molecules at these aqueous solution surfaces were determined. From these results, we found that addition of each of the six salts caused an increase in the thickness of the interfacial water layer at the surfaces to a certain extent. Noticeably, both the cations and the anions contributed to the changes, and the abilities to increase the thickness of the interfacial water layer were in the following order: KBr > NaBr > KCl > NaCl approximately NaF > KF. Since these changes cannot be factorized into individual anion and cation contributions, there are possible ion pairing or association effects, especially for the NaF case. We also found that the orientational parameter D values of the interfacial water molecules changed to opposite directions for the aqueous solutions of the three sodium salts versus the aqueous solutions of the three potassium salts. These findings clearly indicated unexpected specific Na(+) and K(+) cation effects at the aqueous solution surface. These effects were not anticipated from the recent molecular dynamics simulation results, which concluded that the Na(+) and K(+) cations can be treated as small nonpolarizable hard ions and they are repelled from the aqueous interfaces. These results suggest that the electrolyte aqueous solution surfaces are more complex than the currently prevalent theoretical and experimental understandings.

Topics: Air; Bromides; Fluorides; Potassium Chloride; Potassium Compounds; Sodium Chloride; Sodium Compounds; Sodium Fluoride; Water

It was established that nitrite in the presence of chloride, bromide, and thiocyanate decreases the rate of hydrogen peroxide decomposition by catalase. The decrease was recorded by the permanganatometric method and by a method of dynamic calorimetry. Nitrite was not destroyed in the course of the reaction and the total value of heat produced in the process was not changed by its presence. These facts suggest that nitrite induces inhibition of catalase with no change in the essence of the enzymatic process. Even micromolar nitrite concentrations induced a considerable decrease in catalase activity. However, in the absence of chloride, bromide, and thiocyanate inhibition was not observed. In contrast, fluoride protected catalase from nitrite inhibition in the presence of the above-mentioned halides and pseudohalide. As hydrogen peroxide is a necessary factor for triggering a number of important toxic effects of nitrite, the latter increases its toxicity by inhibiting catalase. This was shown by the example of nitrite-induced hemoglobin oxidation. The naturally existing gradient of chloride and other anion concentrations between intra- and extracellular media appears to be the most important mechanism of cell protection from inhibition of intracellular catalase by nitrite. Possible mechanisms of this inhibition are discussed.

Topics: Animals; Bromides; Catalase; Cattle; Enzyme Inhibitors; Fluorides; Hemoglobins; Hydrogen Peroxide; Hydrogen-Ion Concentration; Kinetics; Liver; Nitrites; Oxidation-Reduction; Potassium Compounds; Sodium Chloride; Thermodynamics; Thiocyanates

The effects of different salts (LiCl, NaCl, ChoCl, KF, KCl, and KBr) on the structural stability of a 33-residue peptide corresponding to the leucine zipper region of GCN4 have been studied by high-sensitivity differential scanning calorimetry. These experiments have allowed an estimation of the salt dependence of the thermodynamic parameters that define the stability of the coiled coil. Independent of the nature of the salt, a destabilization of the coiled coil is always observed upon increasing salt concentration up to a maximum of approximately 0.5 M, depending on the specific cation or anion. At higher salt concentrations, this effect is reversed and a stabilization of the leucine zipper is observed. The effect of salt concentration is primarily entropic, judging from the lack of a significant salt dependence of the transition enthalpy. The salt dependence of the stability of the peptide is complex, suggesting the presence of specific salt effects at high salt concentrations in addition to the nonspecific electrostatic effects that are prevalent at lower salt concentrations. The data is consistent with the existence of specific interactions between anions and peptide with an affinity that follows a reverse size order (F- > Cl- > Br-). Under all conditions studied, the coiled coil undergoes reversible thermal unfolding that can be well represented by a reaction of the form N2<==>2U, indicating that the unfolding is a two-state process in which the helices are only stable when they are in the coiled coil conformation.

Topics: Anions; Bromides; Calorimetry, Differential Scanning; Cations; Choline; DNA-Binding Proteins; Drug Stability; Fluorides; Fungal Proteins; Leucine Zippers; Lithium Chloride; Macromolecular Substances; Potassium Chloride; Potassium Compounds; Protein Folding; Protein Kinases; Saccharomyces cerevisiae Proteins; Salts; Sodium Chloride; Thermodynamics