The extraction of hafnium (IV) by some organophosphorus reagents in the presence of two mineral acids

Extraction of hafnium (IV) was studied from solutions of mixtures of perchloric and nitric acids and of perchloric and hydrochloric acids of constant total acidity 2, 4, 6 and 8 M and c_Hf ? 4 × 10^?4mol l^?1. The organic phase consisted of solutions of various acidic or neutral organophosphorus reagents including di-n-butylphosphoric acid, di-n-amylphosphoric acid, di-n-octylphosphoric acid, n-decylphenylphosphonic acid, tri-n-butylphosphine oxide, tri-n-octylphosphine acid (TOPO), tri-n-phenylphosphine oxide, and tri-n-butylphosphate (TBP); or of 2-thenoyltrifluoroacetone, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, or N-benzoyl-N-phenylhydroxylamine in benzene, chloroform, or n-octane. Pronounced synergic extraction of hafnium occurs only with organophosphorus reagents from aqueous phases whose acidity is not lower than 3 M (HClO₄ + HNO₃) or 5 M (HClO₄ + HCl). The synergic effect was not affected markedly by variation of the initial concentration of hafnium in the range 1 × 10^?8 ?4 × 10^?4 mol l^?1, but it decreased with increasing initial concentration of the organophosphorus reagent and decreasing concentration of the H⁺ ions. No synergism was observed for the extraction of hafnium from mixtures of perchloric and sulphuric acids. It is suggested that the hafnium passes into the organic phase in the form of mixed complexes, the salting-out effect of perchloric acid playing an appreciable part.     

Sensing biological effectors through the response of bridged nucleic acids and polynucleotides fixed in liquid-crystalline dispersions

The formation of three-dimensional structures of double-stranded nucleic acid and polynucleotide molecules, fixed in the structure of liquid-crystalline dispersions and bridged by polymeric chelate complexes is described. The bridging elements consist of alternating daunomycin molecules and copper ions. It is shown that these bridges between nucleic acid molecules stabilize cholesteric structures of the DNA liquid-crystalline dispersion. The formation of polymeric chelate bridges is accompanied by a remarkable increase of the intense circular dichroism (CD) band characteristic of the DNA-daunomycin cholesterics. These bridges are destabilized by a number of biologically relevant compounds and macromolecules, such as ascorbic acid, homocarnosine, bovine serum albumin and lysozyme. The dramatic change in the optical activity of the liquid-crystalline dispersions upon addition of these compounds makes them easily detectable. The sensitivity of the method, in the range of analytic concentration 10(-4)-10(-8) M, depends on the nature of the compound being tested. The response of bridged DNA structures to biological effectors observed here foresees their further development as biosensor devices for detecting the presence of biologically and pharmacologically relevant compounds.     

Optical measurements of nucleic acids in the presence of phenol and protein impurities

The concentrations of prostaglandin E2 and F2 alpha have been measured by radioimmunoassay in portions of cord, placenta, amnion, chorion, decidua and myometrium. The samples were obtained at defined periods of pregnancy, and the results have been compared with those obtained from the analyses of endometrial and myometrial tissue removed from women during the secretory phase of a menstrual cycle. The results showed that during pregnancy the mean concentration of prostaglandin E2 was higher (27-518%) than the corresponding value for prostaglandin F2 alpha in all tissues. At term the concentration of prostaglandin E2 (ng/100 mg wet weight of tissue, mean +/- S.D.) was higher in the umbilical cord (5-54 +/- 0-88), decidua (4-02 +/- 1-78) and myometrium (4-19 +/- 1-06), than in the amnion (2-25 +/- 1-27), chorion (1-64 "/- 0-63) or placenta (1-04 +/- 0-25). During labour there was a significant rise (P less than 0.0005, Student's 't' test) in the concentration in decidua (10-76 +/- 4-45), and to a lesser extent (P less than 0-05) in the myometrium (5-84 +/- 2-65) and amnion (4-77 +/- 2-51). The overall concentration in decidua during the first trimester (3-09 +/- 1-02) was significantly lower (P less than 0-005) than in endometrial tissue(16-82 +/- 10-13). The concentration was lower in myometrial tissue from non-pregnant subjects (2-90 +/- 2-21), than in the corresponding tissue removed at term (4-19 +/- 1-06) or during labour 5-84 +/- 2-65). The results for prostaglandin F2 alpha showed a similar pattern, but the values were significantly lower in the umbilical cord, and the percentage changes in concentration in the decidua and myometrium were of a higher magnitude.     

Composition of nucleic acids and concentration of methylated bases in the DNA of Bifidobacterium bifidum var. Tissier

Nucleotide composition of the sum total DNA of B. bifidum, biotype III, was determined by paper chromatography in combination with ultraviolet spectrophotometry. DNA of B. bifidum was referred to the GC-type (GC -- 62.6 mol%). Two additional nitrogen bases were present in the DNA composition; 5-methylcytosine and 6-methylaminopurine -- 0.45 mol% and 0.20 mol%, respectively. Nucleotide composition of the sum total RNA was studied with the aid of high-voltage electrophoresis in combination with ultraviolet spectrophotometry. The sum total RNA was referred to the high GC-type (GC -- 64.9 mol%). These data permit to consider it reasonable to refer bifidobacteria to the Bifidobacterium genus.     

Kinetics for hybridization of peptide nucleic acids (PNA) with DNA and RNA studied with the BIAcore technique

The binding of a mixed-sequence pentadecamer PNA (peptide nucleic acid) containing all four nucleobases to the fully complementary as well as various singly mismatched RNA and DNA oligonucleotides has been systematically investigated using thermal denaturation and BIAcore surface-interaction techniques. The rate constants for association (k(a)) and dissociation (k(d)) of the duplex formation as well as the thermal stability (melting temperature, T(m)) of the duplexes have been determined. Upon binding to PNA tethered via a biotin-linker to streptavidin at the dextran/gold surface, DNA and RNA sequences containing single mismatches at various positions in the center resulted in increased dissociation and decreased association rate constants. T(m) values for PNA x RNA duplexes are on average 4 degrees C higher than for PNA x DNA duplexes and follow quantitatively the same variation with mismatches as do the PNA x DNA duplexes. Also a faster k(a) and a slower k(d) are found for PNA x RNA duplexes compared to the PNA x DNA duplexes. An overall fair correlation between T(m), k(a), and k(d) is found for a series of PNA x DNA and PNA x RNA duplexes although the determination of k(a) seemed to be prone to artifacts of the method and was not considered capable of providing absolute values representing the association rate constant in bulk solution.     

Interaction of phosphatidylcholine with bovine serum albumin. Specificity and properties of the complexes

Phosphatidylcholine dispersed on Celite was rapidly solubilized by neutral bovine serum albumin solutions. Stable protein-lipid complexes were isolated by Agrose gel filtration or by ultracentrifugal flotation in high density solvents, and the physicochemical properties of the complexes were investigated in terms of the stoichiometry of binding, effect of fatty acid ligands on phosphatidylcholine binding, effect of high ionic strength on the stability of the complexes, intrinsic fluorescence and circular dichroism spectra, and sedimentation velocity coefficients. Complexes containing from 2 to 30 phosphatidylcholine molecules per protein molecule were observed; however, no saturation of binding sites could be detected in this range of molar ratios. Oleic acid binding by serum albumin prevents interaction of the protein with phosphatidylcholine, indicating possible competition of these ligands at low contents of the phospholipid. For molar ratios of up to 10 phosphatidylcholine molecules per serum albumin, binding is primarily due to hydrophobic interactions that have no effect on the overall shape and secondary structure of the native protein except for local modifications at tryptophan residues, whose fluorescence becomes quenched and blue shifted on phosphatidylcholine binding. Similar phosphatidylcholine uptake experiments performed with a series of globular proteins indicated that the lipid extraction from Celite surfaces is a non-specific process, accelerated by several other proteins (e.g. aldolase, egg albumin, chymotrypsinogen, soybean trypsin inhibitor, and the major apolipoprotein from bovine serum high density lipoprotein). Formation of stable protein-lipid complexes, however, was only observed with bovine serum albumin, which in contrast to the other proteins is known to have affinity binding sites for anions with hydrophobic side chains.     

Interaction of lanthanum and samarium hexaborides with acids in the area of homogeneity

Conclusions Samarium hexaboride of the limiting composition, SmB₆, possesses the maximum chemical activity in relation to sulfuric and hydrochloric acids.Lanthanum hexaboride of the limiting composition, LaB₆, is the most resistant to the action of acids. The samples with a lower lanthanum content dissolve in the acids to a significantly greater degree.Translated from Poroshkovaya Metallurgiya, No. 3(255), pp. 84–88, March, 1984.     

Synthesis of bis-netropsin-linked hydroxamic acids and their DNA cleavage properties in the presence of transition or lanthanide metal ions

Nobel hydroxamic acids containing bis-netropsin units coupled by polymethylenetether (BNHA) have been synthesized. BNHA-ferrous complexes sequence-specifically cleaved pBR322 DNA fragment whereas corresponding cerium complexes showed low-sequence specific cleavage pattern.     

Wetting and Contact Interaction in Systems Formed by Nitrides of Group IV Transition Metals with Chromium-Nickel Alloy

Wetting and contact interaction have been examined for the nitrides TiN_0.98 and ZrN_0.87 in contact with chromium -nickel alloys of various compositions at 1500-1900°C in purified argon at an excess pressure of 0.35·10⁵ Pa; the methods used have been sessile drop, microstructure, x-ray diffraction, electron-probe microanalysis, and hardness measurement. Wetting is accompanied by interaction of the liquid and substrate with the release from the nitrides of nitrogen and also by the dissolution of Ni and Cr in the nitrides, which increases the lattice constants and raises the microhardness, while leading to the formation of intermetallides and solid solutions.     

Modification of the rat's startle reaction by an antecedent change in the acoustic environment.

Conducted 3 experiments with 6 male albino rats each in which inhibition and facilitation of the startle response, elicited by an intense auditory signal, was related to a change of the frequency characteristic of a 70-db continuous acoustic signal. Data indicated that if a frequency change occurred in the acoustic environment 64 msec before the startle-eliciting stimulus, the amplitude of the startle response was reduced; if frequency change occurred 4 msec prior to the startle-eliciting stimulus, the response latency was reduced. Results extend the generality of previous research employing weak antecedent acoustic signal onset and offset. Results indicate that neural mechanisms mediating the startle reflex may be activated by any change in the acoustic environment and that these mechanisms may be a component of the orienting reflex arc. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

DNA damage induced by m-phenylenediamine and its derivative in the presence of copper ion

We have previously reported that long-term priming of human polymorphonuclear neutrophilic granulocytes (PMN) with interferon-gamma (IFN-gamma) increased the fMLP-stimulated calcium influx. We now show that also after short-term incubation with IFN-gamma, PMN calcium metabolism is modulated. Single adherent cells in three different calcium-containing buffers (high, normal, and low [Ca2+]) were stimulated with the bacterial peptide fMLP or the Ca-ATPase inhibitor thapsigargin (Tg) after about 5 min preincubation with IFN-gamma. The results of this protocol indicated that IFN-gamma increases both calcium influx and calcium sequestration. Store dependent Ca2+ influx, directly measured on readdition of calcium to Tg-treated cells incubated in EGTA buffer, was significantly enhanced in IFN-gamma-treated cells. This effect of IFN-gamma was enhanced by the tyrosine kinase inhibitor herbimycin A. Strikingly, in low extracellular calcium concentrations, IFN-gamma induced calcium transients in 20%-60% of the cells. The proportion of PMN responding with Ca2+ transients increased with decreasing extracellular calcium concentration. Average lagtime from addition of IFN-gamma to a response that could be measured was 7.3 sec, and average increase in [Ca2+] above the basal level was 790 nM. These IFN-gamma-induced transients could not be depressed by herbimycin A. Thus, IFN-gamma can increase capacitative calcium influx, induce calcium transients, and possibly affect calcium sequestration in human PMN.     

Interaction and orientation of an alpha-aminoisobutyric acid- and tryptophan-containing short helical peptide pore-former in phospholipid vesicles, as revealed by fluorescence spectroscopy

The interaction and orientation of a membrane protein ion channel model, an alpha-aminoisobutyric acid analogue of gramicidin B (GBA), in egg yolk phosphatidylcholine vesicles was studied by means of fluorescence spectroscopic techniques. GBA helices form stable ion-conducting pores in membranes [Jelokhani-Niaraki et al. (1995) J. Chem. Soc. Perkin Trans. 2, 801-808]. In an alpha-helical model for the peptide, all Trp residues (intrinsic fluorophores) are distributed near the C-terminus. Fluorescence quenching experiments revealed the exposure of the helical peptides' C-termini to aqueous environments. Dansyl-labeled vesicles were used to investigate the GBA dynamism of the interaction with membranes. It was shown that considerable amounts of peptide reside on and in the vicinity of the outer surface of lipid bilayers. The transmembrane transfer to the inner layer is slow due to the high affinity of Trp residues for bilayer interfaces which anchor the peptide to the outer surface. A structural-functional interpretation of the GBA interaction with membranes is presented.     

The use of N-succinyl derivatives in the study of amino acids and peptides by mass spectrometry

The terminal amino group of amino acids and peptides is blocked as the N-succinyl derivative by reaction with succinic anhydride. The product is then converted to the N,O-permethyl derivative in order to increase its volatility for use in mass spectrometry. The permethylated N-succinyl derivative retains the advantages of the permethylated N-acetyl derivative in regard to ease of preparation on a small scale, volatility and the presence of characteristic fragmentation patterns in their mass spectra. However, peaks in the high mass region are more abundant due to loss of CH3O-from the N-succinyl carbomethoxyl group as well as from the C-terminal carbomethoxyl group. Ions characteristic of the sequence and of individual amino acids are observed, and molecular weight can be determined from the relatively abundant ion at [M--CH3O]+ and from the weak molecular ion.     

Binding of 2-azaanthraquinone derivatives to DNA and their interference with the activity of DNA topoisomerases in vitro

We have investigated the binding ability to DNA of compounds belonging to the 2-azaanthraquinone-type structure and have examined the effect on the activity of DNA gyrase as well as on mammalian topoisomerases in vitro. Using different biophysical techniques it was found that one of these ligands, 9-((2-dimethylamino)ethyl)amino)-6-hydroxy-7-methoxy-5, 10-dihydroxybenzo[g]isoquinoline-5,10-dione (TPL-I), is an intercalating DNA binding agent, whereas the parent compound tolypocladin (TPL) and a derivative (TPL-II) showed almost no similar affinity to DNA. CD measurements demonstrated a significant and selective binding tendency of TPL-I to alternating purine/pyrimidine sequences with some preference for poly(dA-dT). poly(dA-dT). Tm values were increased of the ligand complex with the alternating AT-containing duplex polymer. The binding to various DNAs was characterized by CD and visible absorption spectral changes. From the latter, different binding constants of 6.2 x 10(5) and 1.5 x 10(5) M-1 were obtained for poly(dA-dT).poly(dA-dT) and poly(dA). poly(dT), respectively. Sedimentation measurements with supercoiled pBR322 plasmid DNA clearly indicated an intercalative binding mechanism associated with an unwinding angle of about 18 degrees. These results suggest that the intercalative binding of TPL-I is promoted by the 2-(dimethylamino)ethylamino group substituted on carbon 9 of the anthraquinone system. The cytotoxic compound TPL-I, but not TPL or TPL-II, effectively inhibited the DNA supercoiling reaction of DNA gyrase and the activity of mammalian topoisomerases I and II as measured by the relaxation assay. TPL-I affects the cleavage reaction of topoisomerases on a single site located in alternating purine-pyrimidine sequence regions. The inhibitory potency of TPL-I can be ascribed to a blocking of cleavage sites on the DNA substrate, which correlates with the sequence preference of the ligand.     

A single cell gel electrophoresis technique for the detection of DNA damage induced by ACNU, an alkylating agent or irradiation in murine glioma cell lines

A simple and convenient technique for in situ quantification of DNA damage induced by 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloro-ethyl)-3-nitrosourea hydrochloride (ACNU) an alkylating agent, or irradiation was demonstrated in C6 glioma cells using a single cell gel electrophoresis. Treatment with ACNU or irradiation caused a dose dependent DNA damage which was detected by measuring the length of migration of fragmentary DNA in individual cells. Wild type C6 cells treated with ACNU (0, 10, 30, 60 micrograms ml-1) for one hour showed longer distance of migration of DNA than the ACNU-resistant subtype cells (C6R), indicating that ACNU-sensitive C6 cells were more vulnerable to ACNU than C6R cells. The results of DNA migration in C6 and C6R cells treated with ACNU were consistent with that from MTT assay which had been regarded as a standard method for chemosensitivity test. Furthermore, a time course study for DNA repair activity of C6 and C6R cells was also performed by measuring the length of DNA migration after incubation (0, 15, 30, 60, 120 min) of cells treated with 60 micrograms ml-1 ACNU. C6R cells repaired DNA damage more rapidly than C6 cells. In addition, the technique was also used to measure the DNA damage in C6 cells exposed to 0, 2, 6, 8, 10 Gy of x-ray irradiation, and a dose-dependent DNA migration after radiation injury was observed. This technique appears to be simple and useful for assessing chemosensitivity or radiosensitivity in individual glioma cells.