3-Picoline-N-oxide complexes of rare-earth bromides

3-Picoline-N-oxide (3-PicNO) complexes of rare-earth bromides of the formulaMBr3(3-PicNO)8–n·nH2O wheren=0 forM=La, Pr, Nd, Sm Tb or Y andn=2 forM=Ho or Yb have been prepared. Infrared and proton NMR studies indicate that the coordination of the ligand is through oxygen. Conductance data in acetonitrile suggest that two bromide ions are coordinated to the metal ion. Proton NMR studies suggest a bicapped dodecahedral arrangement of the ligands around the metal ion in solution for Pr(III), Nd(III) and Tb(III) complexes.

Korteweg-de Vries equation for the propagation of fast ion-acoustic waves in multi-dimensions

Abstract is not available.

Studies of multiple ionization in the RF spark and vacuum vibrator arc ion sources

Relative abundance distributions of multiply-charged ionic species have been measured for the RF spark and vacuum vibrator are ion sources, for a number of elements. An attempt has been made to explain the observed charge state distribution on the basis of models for the arc and spark plasma. The difficulties in the way of explaining the observed charge state distributions, using the LTE model with Saha distribution as well as the corona model, are pointed out. The distribution can be explained by a diffusion-dominated plasma model with known or calculated values for ionization cross-sections, the single impact model being suitable for the RF spark and the multiple impact model for the vibrator arc.

Matrices of finite Lorentz transformations in a noncompact basis. III. Completeness relation for O(2, 1)

A parametrization of the elements of the three-dimensional Lorentz group O(2, 1), suited to the use of a noncompact O(1, 1) basis in its unitary representations, is derived and used to set up the representation matrices for the entire group. The Plancherel formula for O(2, 1) is then expressed in this basis.

Nonlinear saturation of ion-acoustic instability

It is proposed that the wave mediated indirect wave-particle interaction may be responsible for nonlinear saturation of current driven low frequency ion-acoustic turbulence. This process decreases the growth rate and increases the damping rate of the wave. Comparison has been made with some experiments.

X-ray crystal structure of a ternary copper(II) vitamin B6 complex, hydroxo(2,2'-bipyridyl)(pyridoxinato) copper(II) monohydrate. A rare example of monodentate coordination of copper(II) by the hydroxyl ion

A ternary metal complex involving Vitamin B6 with the formula [Cu(bipy)(pn) (OH)]H2O (bipy = 2,2'²-bipyridine, PN = anionic pyridoxine) has been synthesized and studied in the solid state by means of spectroscopy and X-ray crystallography. The geometry around copper(II) is distorted square pyramidal, two oxygens from phenolic and 4-(hydroxymethyl) groups of pn, two nitrogens from bipy and an axial OH- ion forming the coordination sphere. In this structure pn exists in a new anionic form with deprotonation of the phenolic group. The structure also provides a rare example of monodentate hydroxyl coordination to copper.

Ion heating by the lower hybrid mode

The lower hybrid mode excited in a plasma with cross-field current and density gradient induces an attractive potential between the negative-and positive-energy modes of the plasma. The growth rate is thereby reduced and becomes comparable with the damping rates due to wave-particle interaction. This leads to the saturation of the turbulent field. Some applications have been made to the turbulent heating experiments in plasma where cross-field current is present.

Thermodynamics of metal ion binding and denaturation of a calcium binding protein from Entamoeba histolytica

The thermodynamics of tie binding of calcium and magnesium ions to a calcium binding protein from Entamoeba histolytica was investigated by isothermal titration calorimetry (ITC) in 20 mM MOPS buffer (pH 7.0) at 20 degrees C. Enthalpy titration curves of calcium show the presence of four Ca2+ binding sites, There exist two low-affinity sites for Ca2+, both of which are exothermic in nature and with positive cooperative interaction between them. Two other high affinity sites for Ca2+ exist of which one is endothermic and the other exothermic, again with positive cooperative interaction. The binding constants for Ca2+ at the four sites have been verified by a competitive binding assay, where CaBP competes with a chromophoric chelator 5, 5'-Br-2 BAPTA to bind Ca2+ and a Ca2+ titration employing intrinsic tyrosine fluorescence of the protein, The enthalpy of titration of magnesium in the absence of calcium is single site and endothermic in nature. In the case of the titrations performed using protein presaturated with magnesium, the amount of heat produced is altered. Further, the interaction between the high-affinity sites changes to negative cooperativity. No exchange of heat was observed throughout the addition of magnesium in the presence of 1 mM calcium, Titrations performed on a cleaved peptide comprising the N-terminus and the central linker show the existence of two Ca2+ specific sites, These results indicate that this CaBP has one high-affinity Ca-Mg site, one high-affinity Ca-specific site, and two low-affinity Ca-specific sites. The thermodynamic parameters of the binding of these metal ions were used to elucidate the energetics at the individual site(s) and the interactions involved therein at various concentrations of the denaturant, guanidine hydrochloride, ranging from 0.05 to 6.5 M. Unfolding of the protein was also monitored by titration calorimetry as a function of the concentration of the denaturant. These data show that at a GdnHCl concentration of 0.25 M the binding affinity for the Mg2+ ion is lost and there are only two sites which can bind to Ca2+, with substantial loss cooperativity. At concentrations beyond 2.5 M GdnHCl, at which the unfolding of the tertiary structure of this protein is observed by near UV CD spectroscopy, the binding of Ca2+ ions is lost. We thus show that the domain containing the two low-affinity sites is the first to unfold in the presence of GdnHCl. Control experiments with change in ionic strength by addition of KCI in the range 0.25-1 M show the existence of four sites with altered ion binding parameters.

Role of Thiobacillus ferrooxidans and sulphur (sulphide)-dependent ferric-ion-reducing activity in the oxidation of sulphide minerals

Thiobacillus ferrooxidans oxidized the sulphide minerals e.g., pyrite, pyrrhotite and copper concentrate under anaerobic conditions in the presence of ferric ion as sole electron acceptor. Copper and iron were solubilized from sulphide ores by the sulphur (sulphide)-dependent ferric-ion oxidoreductase activity. Treatment of resting cells of T. ferrooxidans with 0.5% phenol for 30 min completely destroyed the iron- and copper-solubilizing activity. The above treatment destroyed the sulphur(sulphide)-dependent ferric-ion-reducing activity completely but did not affect the iron-oxidizing activity. The results suggest that sulphur(sulphide)-dependent ferric-ion-reducing activity actively participates in the oxidation of sulphide minerals under anaerobic conditions. The activity of sulphur(sulphide)-dependent ferric ion reduction in the solubilization of iron and copper from the sulphide ores were also observed under aerobic conditions in presence of sodium azide (0.1 μmol), which completely inhibits the iron-oxidizing activity.

Magnesium ion conducting, room temperature molten electrolytes

Room temperature, magnesium ion conducting binary molten electrolyte consisting of acetamide and magnesium perchlorate has been prepared and characterized. The molten liquid is very stable and shows high ionic conductivity, of the order of several mS cm(-1) at 25 degrees C with other favourable physicochemical properties. Vibrational spectroscopic studies reveal that the free ion concentration is higher than that of ion pairs and aggregates in the melt. The electrochemical reversibility of magnesium deposition and dissolution is demonstrated using voltammetry and impedance studies. Preliminary studies on rechargeable batteries assembled using gamma-MnO2 and Mg metal as the electrodes together with the molten electrolyte show high discharge capacity.

Soft matter lithium salt electrolytes: ion conduction and application to rechargeable batteries

Soft matter provides diverse opportunities for the development of electrolytes for all solid state lithium batteries. Here we review soft matter solid electrolytes for lithium batteriesthat are primarily obtained starting from liquid electrolytic systems. This concept of solid electrolyte synthesis from liquid is significantly different from prevalent approaches. The novelty of our approach is discussed in the light of various fundamental issues and in relation to its application to rechargeable lithium batteries.

Co(II) and Cr(III) complexes of formate-formamide mixed ligands: synthesis, structures, single crystal-to-single crystal transformation and magnetic behaviour

Solvothermal treatment of an equimolar mixture of Co(NO3)(2)center dot 6H(2)O, HCONH2 and NaN3 in MeOH at 100 degrees C yielded a three-dimensional NaCl type network Co(HCOO)(2)(HCONH2)(2) center dot HCONH2 (1a) containing formamides in the pores of the structure. Solvated pink 1a undergoes single crystal-to-single crystal (SCSC) transformation at 215 degrees C to form the desolvated dark brown product Co(HCOO)(2)-( HCONH2)(2) (1b) with the retention of the original framework. Reversible single crystal-to-single crystal transformation of 1b (brown) to 1a (pink) in the presence of excess formamide was also established at room temperature. The coordination environment around Co(II) in both 1a and 1b is octahedral with a CoN2O4 coordination composition. A similar reaction replacing Co(II) by Cr(III) produced a heterometallic 3D extended network Na[Cr(HCOO)(4)(HCONH2)(2)]center dot 2H(2)O (2a) at 100 degrees C. An increase in reaction temperature to 150 degrees C produced a simple mononuclear complex Cr(HCOO)(3)(HCONH2)(3) center dot 3H(2)O (2b). Variable temperature magnetic studies revealed the presence of a canting phenomena in both 1a and 1b, and hysteresis loop in the field dependent magnetisation plot at 2 K whereas complex 2a is simply paramagnetic in nature.

Tris(methyl 3-oxobutanoato-kappa O-2,O `)aluminium(III)

In the title compound, [Al(C5H7O3)(3)],three acac-type ligands(methyl 3-oxobutanoate anions) chelate to the aluminium(III)cation in a slightly distorted AlO6 octahedral coordination geometry.Electron delocalization occurs within the chelating rings.

Identification of alpha- and beta-Hydroxy Acid Containing Cyclodepsipeptides in Natural Peptide Mixtures Using Negative Ion Mass Spectrometry

Natural peptide libraries often contain cyclodepsipeptides containing alpha or beta hydroxy residues. Extracts of fungal hyphae of Isaria yield a microheterogenous cyclodepsipeptide mixture in which two classes of molecules can be identified by mass spectral fragmentation of negative ions. In the case of isaridins, which contain an alpha-hydroxy residue and a beta-amino acid residue, a characteristic product ion corresponding to a neutral loss of 72 Da is obtained. hi addition, neutral loss of water followed by a 72 Da loss is also observed. Two distinct modes of fragmentation rationalize the observed product ion distribution. The neutral loss of 72 Da has also been obtained for a roseotoxin component, which is also an alpha-hydroxy residue containing cyclodepsipeptide. In the case of isariins, which contain a beta-hydroxy acid residue, ring opening and subsequent loss of the terminal residue as an unsaturated ketene fragment, rationalizes the observed product ion formation. Fragmentation of negative ions provide characteristic neutral losses, which are diagnostic of the presence of alpha-hydroxy or beta-hydroxy residues.

The crystal and molecular structure of benzyloxycarbonyl-a-amino-isobutyryl-L-prolyl-methylamide. The observation of an X2-Pro3 Type III b-turn

The crystal and molecular structure of N-benzyloxycarbonyl-a-aminoisobutyryl-L-prolyl methylamide, the amino terminal dipeptide fragment of alamethicin, has been determined using direct methods. The compound crystallizes in the orthorhombic system with the space group P212-21. Cell dimensions are a = 7.705 A, b = 11.365 A, and c = 21.904 A. The structure has been refined using conventional procedures to a final R factor of 0.054. The molecular structure possesses a 4 - 1 intramolecular N-H--0 hydrogen bond formed between the CO group of the urethane moiety and the NH group of the methylamide function. The peptide backbone adopts the type 111 P-turn conformation, with 42 = -51.0°, +* = -39.7",&j = -65.0', $3 = -25.4'. An unusual feature is the occurrence of the proline residue at position 3 of the P-turn. The observed structure supports the view that Aib residues initiate the formation of type 111 @-turn conformations. The pyrrolidine ring is puckered in Cy-exo fashion.