Tris Solution Research Articles

44] Mg2+/NH4+/polyamine system for polyuridine-dependent polyphenylalanine synthesis with near in vivo characteristics

Publisher Summary The polymix system represents a poly(U)-dependent poly(Phe) synthesis where protein synthesis with Escherichia coli ribosomes approaches in vivo levels concerning rate and accuracy. The system has been successfully applied to both the determination of some parameters of the ribosomal fidelity and the analyses of mutants with an altered ribosomal accuracy. In the first step AcPhe-tRNA is bound to ribosomes at 6 mM Mg 2+ , taking into account that tRNA binding requires higher Mg 2+ concentrations than optimal poly(Phe) synthesis. The two incubations at 6 mM Mg 2+ during the first step improve AcPhe-tRNA binding for unknown reasons. For poly (Phe) synthesis the Mg 2+ concentration is decreased to 3 mM, which is required for an optimal rate of Phe incorporation under the applied conditions. It is important to use HEPES buffer instead of Tris, since HEPES has its maximal buffer capacity at pH 7.55 (Tris at pH 8.3) and hence shows fewer changes during temperature shifts. For example, a 10 mM HEPES (Tris) solution adjusted to pH 7.5 at room temperature (21 °) measures at 37° 7.3 (Tris, 7.1) and at 0° 7.7 (Tris, 8.1). In this system the accuracy is impaired at a pH above 7.8 and below 7.3.

The role of membrane depolarization in the contractile response of the rabbit basilar artery to 5-hydroxytryptamine.

1. 5-Hydroxytryptamine (5-HT, 10(-9)-10(-4) M) depolarized and contracted smooth muscle cells (resting potential: -69.1 +/- 0.9 mV, n = 112) in isolated cylindrical segments of the rabbit basilar artery. 2. Simultaneous measurement of membrane potential and wall tension (n = 43, thirteen vessels) showed that the onset of 5-HT-induced depolarization coincided with the onset of smooth muscle contraction in the majority of cells studied. In addition, the onset of relaxation which followed the wash-out of 5-HT always preceded the onset of membrane repolarization by 52 +/- 8 s (n = 14). 3. In 30% of smooth muscle cells exposed to concentrations of 5-HT greater than 10(-6) M, fast rhythmic depolarizations (amplitude 10-20 mV) were superimposed on the developing depolarization. Rhythmic membrane depolarization was always followed by rhythmic smooth muscle contraction, which peaked 2-4 s after the peak of the fast depolarization. 4. Muscle contraction, but not depolarization, produced with concentrations of 5-HT greater than 10(-7) M, was significantly increased by the removal of intimal-endothelial cells. 5. Smooth muscle depolarization recorded in the presence of increased extracellular K+ (greater than 5.2 mM) preceded the onset of smooth muscle contraction. For a similar change in membrane potential produced with either increased extracellular K+ or 5-HT, the corresponding increase in arterial wall tension was always greater with 5-HT. 6. The depolarization and contraction induced by 5-HT was markedly reduced or abolished if extracellular Na+ was totally replaced, isosmotically, with either sucrose or Tris at pH 7.4. Normal-sized contraction, but not depolarization, was recorded with 5-HT in Na+-free Tris solution at pH 8. 7. These observations suggest that 5-HT-stimulated contraction in cerebrovascular smooth muscle is largely a result of mechanisms other than depolarization of the smooth muscle cell membrane which it produces. However, high concentrations of 5-HT (greater than 10(-6) M) can stimulate additional depolarization, which has a faster time course and rhythmic nature. Discrete depolarizations of this type are responsible for initiating additional, phasic smooth muscle contractions.

Proton spin relaxation in solutions of the complex tris(acetylacetonato)chromium(III)

Field-dependent proton spin-lattice and spin-spin relaxation times have been measured for CH 3 in dilute chloroform solutions of tris(acetylacetonato)chromium(III) (Cr(acac) 3) complex over a temperature range of 253–323 K and a proton resonance frequency range of 10–90 MHz. The results have been interpreted in terms of scalar, dipolar, and scalar-dipolar cross relaxation. The effects of methyl group internal rotation are included. In particular, coupled modulation of ESR relaxation and electron-nuclear dipolar relaxation by reorientational motion of the complex is treated. The reorientational correlation times of the complex obtained are consistent with those measured from 13C T 1 in the analogous diamagnetic Co(III) complex, but significant deviations from the Stokes-Einstein relation with the consideration of microviscosity are observed. Solvation of the complex with chloroform is further identified from chemical-shift measurements and is utilized to interpret the results. The proton T, data are discussed in terms of their relevance to the zero-field-splitting interaction and to the contribution of scalar-dipolar cross relaxation.

Enthalpy of solution of tris(2,4-pentanedionato)cobalt(III) in aqueous mixed solvents of 1,4-dioxane and 2-methyl-2-propanol

The solubilities Xs of tris(2,4-pentanedionato)cobalt(III) (Co(acac)3) in water – 1,4-dioxane (D) and water – 2-methyl-2-propanol (TBA) mixtures were determined over the temperature range of 15–60 °C and 20–43 °C, respectively. These data were fitted to [Formula: see text] and the enthalpy of solution [Formula: see text] of Co(acac)3 was estimated by differentiating the equation. For the water–D system, a linear correlation was found between the excess enthalpy of solution [Formula: see text] of Co(acac)3 and the excess internal pressure [Formula: see text] of the mixtures. [Formula: see text] of Co(acac)3 in the water–TBA mixtures showed complicated composition dependence due to microheterogeneity in the mixtures. The enthalpy of hydrophobic hydration [Formula: see text] of Co(acac)3 in the water–D mixtures was also estimated from the solubility curves and it was found that [Formula: see text] decreased exponentially with decreasing mole fraction of water.

The pK ∗ of TRISH + in Na-K-Mg-Ca-Cl-SO 4 brines—pH scales

The stoichiometric dissociation constant, pK ∗ of TRISH + has been determined in NaCl, KCl, MgCl 2 and CaCl 2 solutions to an ionic strength of 6 molal. The results have been used to derive Pitzer coefficients for the interactions of TRIS with Na +, K +, Mg 2+ and Ca 2+ ions. These results can be used to determine the pK ∗ of TRISH + in mixed brines which can be used to calibrate pH electrodes. Measurements of pK ∗ of TRISH + in mixtures of NaCl-MgCl 2, NaCl-CaCl 2, NaCl-Na 2SO 4, KCl-MgCl 2 and KCl-CaCl 2, artificial seawater and Dead Sea waters were made to determine the reliability of the Pitzer coefficients. The estimated values were found to be in good agreement with the measured values provided corrections were made for the interactions of H + with SO 2− 4. It now is possible to use dilute solutions of TRIS and TRISH + to make buffers that can be used to make reproducible pH measurements in brines.

ChemInform Abstract: Induced Redox Reactivity of Tetrathiovanadate(V): Synthesis of the Vanadium(IV) Dimer V2(μ‐S2)2(i‐Bu2NCS2)4 and Its Structural Relationship to the V/S Mineral Patronite.

AbstractTreatment of a solution of tris‐(tricaprylmethylammonium)tetrathiovanadate, the metathesis product of (I), with solid tetraisobutylthiuram disulfide followed by silica gel chromatography affords the title compound (II).

Synthesis of Co-Substituted Barium Hexaferrite by Hydrolysis of Organometallic Compounds

Pure and fine barium hexaferrite particles were synthesized by hydrolysis of ethanol solutions of organometallic compounds, barium ethoxide and tris (acetylacetonate) iron (III) under controlled hydrolyzing conditions. Effects of substitution of cobalt ion in barium hexaferrite were examined with cobalt-substituted barium hexaferrite synthesized by the same way using bis (acetylacetonate) diaquacobalt (II). Heating the amorphous coprecipitated products at 800°C for 1h resulted in direct crystallization of barium hexaferrite partly substituted with cobalt ion without forming intermediate compounds such as barium monoferrite or cobalt ferrite. No significant difference in crystallization process was observed between samples with and without cobalt ion. Crystallinity of heat-treated sample was found to be insensitive to the substitution of cobalt ion, which reflects the saturation magnetization. The saturation magnetization of crystallized barium hexaferrite slightly decreased with cobalt substitution in the range of 0≤x≤1 in BaFe12-xCoxO19. On the other hand, the coercive force changed drastically with increasing cobalt ion content. The coercive force could be controlled over the range of 1 to 5 kOe by cobalt ion content and heat treatment condition. Particle size of cobalt-substituted barium hexaferrite lay in 500 to 2000A with single domain.

Differential expression of oxygen-evolving polypeptide genes in maize leaf cell types

Three polypeptides of 33 kD, 23 kD and 16 kD are released from maize photosystem II particles by alkaline Tris solution treatment and shown to cross-react with antisera to purified spinach oxygen-evolving (OE) polypeptides of 34 kD, 23 kD and 17 kD, respectively. They are not located exclusively in mesophyll cells but each is about 4 times more abundant in the thylakoid membranes of mesophyll than bundle sheath cells of etiolated, greening and green leaves. Three maize cDNA clones (OE33, OE23, OE16) have been identified by hybrid-selection, in vitro translation and immunoprecipitation with antisera against spinach OEs. Transcripts of all three genes are already detectable in both mesophyll and bundle sheath cells of etiolated leaves; however, they accumulate transiently and coordinately in mesophyll cells but remain at a constant low level in bundle sheath cells upon illumination of dark-grown maize seedlings. Moreover, the level of each protein increases in mesophyll cells following the accumulation of transcripts during greening and remains high in late greening and green leaves, despite the decline in each corresponding mRNA. The accumulation of all three OE proteins is also stimulated by light in bundle sheath cells without increases in their corresponding mRNAs. The preferential localization of these three proteins in mesophyll cells is due to both transcriptional and translational regulation.

ChemInform Abstract: [Sb3I10‐]∞ ‐ a Polymeric Anion with Transitions from Trigonal‐Pyramidal to Octahedral Coordination of Sb(III).

AbstractIn the novel band‐like polymeric title anion, prepared as prism‐forming red salt (I) (PT) by crystallization from a solution of tris(dimethylamino)cyclopropenyliumiodide and SbI3 (1:3) in MeCN, 18 different Sb ‐I distances are observed.

Measurement of penbutolol and 4-hydroxypenbutolol in plasma or serum by HPLC.

A simple HPLC method for penbutolol and 4-hydroxypenbutolol assay has been developed. Plasma or serum (200 microliters) is vortex-mixed (30 s) with Tris solution (2 M, pH 10.6) containing an internal standard (50 microliters) and methyl t-butyl ether (200 microliters). After centrifugation, the extract (100 microliters) is analysed using an unmodified silica column (250 x 5 mm ID) and iso-octane-methanol-methyl t-butyl ether (55:25:20) containing ammonium perchlorate (10 mM, pH 5.7) as eluent and with fluorescence detection. No interference has been encountered and the limit of accurate measurement for both compounds is 5 micrograms/l.

Effects of capsaicin on molluscan neurons: A voltage clamp study

1. The effects of capsaicin (CAP) on membrane ionic currents of identified and non-identified neurons were investigated by use of the single electrode clamp (SEC). 2. CAP (300 μM, 22°C, pH 7.4) caused a 25–50% reduction of the inward current and a 50–80% reduction of the outward current in normal or Na-free (Tris) solution. 3. The Na current ( I Na) was moderately decreased (about 10%) in LPa2 neuron, but a 50% reduction of the peak Ca current ( I Ca) was observed. The action of CAP on I Ca varied from cell to cell but an enhanced inactivation of the fast calcium current was found in all neurons studied. 4. CAP (150μM, 10 min) highly attenuated the long-lasting component of the inward current in LPa2 recorded in Na-free (TEA) Ba solutions. 5. CAP attenuated the fast outward current ( I A) and voltage-dependent outward current ( I K) in 100 and 300 μM concentrations for the half blocking dose (ID 50) in LPa2 neuron, respectively. 6. CAP decreased the slow outward tail currents but hardly influenced the leakage current ( I L). 7. We suggest that the acute action of CAP coupled with a series of events in the neuronal membrane can modify the conductance via electrically excitable calcium, potassium and sodium channels differentially.

Influence of buffers on dV/dtmax recovery kinetics with lidocaine in myocardium.

Buffers are reported to modify electrical function of heart tissue. Since electrophysiological actions of antiarrhythmic drugs are examined in different buffer systems, we set out to examine the influence of buffers on lidocaine's electrophysiological actions by measuring recovery kinetics of maximum upstroke velocity (dV/dtmax) in lidocaine solutions buffered with HCO-3-CO2, N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES), and tris(hydroxymethyl)aminomethane (Tris) at extracellular pH 7.4. Transmembrane potential and dV/dtmax were recorded from guinea pig papillary muscle. Recovery kinetics were determined by introducing progressively earlier test stimuli during diastole. During lidocaine (1.5 X 10(-5) M) exposure, the time constant (Tr) of dV/dtmax recovery significantly increased when 21 mM HCO-3-5% CO2 was replaced by either 5 mM HEPES (38 +/- 8%, mean, +/- SED) or 5 mM Tris (41 +/- 6%). This potentiation of Tr was 1) reversed by increasing Tris to 20 mM, and 2) also abolished by restoring HCO-3-CO2 to HEPES or Tris solutions. Decreasing HCO-3 (21-4 mM) and CO2 (5-1%) increased Tr by 27 +/- 1%. We propose that the mechanism for the potentiation of Tr is therefore related to buffer concentration rather than to the lack of HCO-3-CO2. We speculate that, by reducing surface pH, lowered buffer capacity can slow the rate of dV/dtmax recovery.

The electrochemical reduction of the bis(acetylacetonato)nickel(II) complex in acetonitrile

The cathodic behaviour of the bis(acetylacetonato)nickel(II) complex was investigated in acetonitrile solution by cyclic voltammetry and controlled potential electrolysis. Irrespective of the electrode material employed, this species undergoes a complicated reduction process involving chemical reactions preceding and following the charge transfer step and leading to the formation of metallic nickel as the ultimate product. For this reduction, a mechanistic scheme is proposed which is consistent with the data. Evidence for the formation in the solution of mono(acetylacetonato)nickel(II) and tris(acetylacetonato)nickel(II) complexes were also obtained.

60Co Hot-atom Chemistry and 57 Fe Mössbauer Study of the State of Dispersion in Frozen Organic Solutions of Tris (acetylacetonato) cobalt (III) and Iron (III)

60Co Hot-atom Chemistry and 57 Fe Mössbauer Study of the State of Dispersion in Frozen Organic Solutions of Tris (acetylacetonato) cobalt (III) and Iron (III)

Dissociation and dioxygen formation in hydroxide solutions of tris(2,2'-bipyridyl)iron(III) and tris(1,10-phenanthroline)iron(III): rates and stoichiometry

Dissociation and dioxygen formation in hydroxide solutions of tris(2,2'-bipyridyl)iron(III) and tris(1,10-phenanthroline)iron(III): rates and stoichiometry

Synthesis, crystal and molecular structure of bis(tetraethylammonium) bis(μ-ethylthio)-bis(gm-ethylthioxanthato)-bis[trithiocarbonatoiron(III)

Bis(tetraethylammonium) bis(μ-ethylthio)-bis(gm-ethylthioxanthato)-bis [trithiocarbonatoiron(III)], [(C 2H 5) 4N] 2[Fe(SC 2H 5)(S 2CSC 2H 5)(CS 3] 2 has been isolated as a decomposition product from a dilute acetonitrile solution of tetraethylammonium tris(ethylthioxanthato)iron(II) [(C 2H 5) 4N][Fe(S 2CSC 2H 5) 3]. The crystal and molecular structure of [(C 2H 5) 4N] 2 [Fe(SC 2H 5)(S 2CSC 2H 5)(CS 3)] 2 was determined from three-dimensional X-ray data. The compound crystallizes in the monoclinic space group P2 1|n with a = 10.442(3), b = 9.809(3), c = 21.728(6) Å, β = 94.62(2)°, V = 2218.3 Å 3 and Z = 2. The structure was solved by the Patterson method. Least-squares refinements using 3656 unique reflections with |F o|>3.92σ(F o) converged to R 1 = 0.044 and R 2 = 0.041. The iron atoms in the centrosymmetric complex [Fe(SC 2H 5)(S 2CSC 2H 5)(CS 3] 2su2− have a distorted octahedral coordination and are bridged by two ethylthio and two ethylthioxanthato ligands. Two trithiocarbonato ligands are bonded terminally to the iron atoms, resulting in four-membered chelate rings with two endocyclic CS bonds (mean bond length 1.720 Å) and a shorter exocyclic one (1.666(3) Å). The geometry of the [Fe(SC 2H 5)(S 2CSC 2H 5)] 2su2+ moiety with a FeFe distance of 2.614(1) Å indicates a direct metalmetal interaction.

Comment on "Quantum yield and electron-transfer reaction of the lowest excited state of the uranyl ion"

When experiments were conducted with aqueous solutions (pH/sub 2/) of uranyl nitrate and tris (1,10-phenanthroline) ruthenium (II) perchlorate using steady-state fluorescence quenching, quenching of *Ru(phen)/sub 3//sup 2 +/ by UO/sub 2//sup 2 +/ followed Stern-Volmer kinetics, with K/sub sv/ = (1.89 +- 0.20) x 10/sup 2/m/sup -1/. Using this and the known lifetime of *Ru(phen)/sub 3//sup 2 +/ under these conditions (after correcting for quenching by dissolved oxygen), a rate constant of 1.2 x 10/sup 9/M/sup -1/s/sup -1/ was obtained for the quenching process. This is close to the rate of quenching of *Ru(phen)/sub 3//sup 2 +/ by Fe/sup 3 +/ /sup 2/ is slightly higher than the rate of quenching of *Ru(bpy)/sub 3//sup 2 +/ by UO/sub 2//sup 22/ /sup 1/ and is consistent with the same mechanism as in these two cases, i.e., electron transfer. As observed with the Ru(bpy)/sub 3//sup 2 +//UO/sub 2//sup 2 +/ system, prolonged photolysis did not result in any permanent change in the absorption spectrum of the system, demonstrating a high overall photostability. Because of the intense absorption of the Ru(phen)/sub 3//sup 2 +/ species, the steady-state experiments do not permit demonstration of the reverse quenching of *UO/sub 2//sup 2 +/ by Ru(phen)/submore » 3//sup 2 +/. However, studies on the fluorescence excitation spectra are consistent with the occurrence of such a process.« less

Hydrogenation of ethyne catalysed by supported solutions of tris‐(triphenylphosphine)chlororhodium (I)

AbstractThe hydrogenation of ethyne and propyne, catalysed by supported solutions tris‐(triphenylphosphine) chlororhodium (I) [RhI(PPh3)3Cl] has been studied in a fixed bed reactor at 1 atmosphere total pressure over the temperature range 60–90°C. A number of silica gel supports and reaction solvents, of different co‐ordination strengths, including molten triphenylphosphine itself were examined to determine their effect on catalyst activity and selectivity. Optimum liquid loadings were observed for each support and the presence of excess triphenylphosphine was essential to the promotion and maintenance of any catalyst activity and the optimum molar ratio PPh3/RhI (PPh3)3Cl =70. The catalyst was 100% selective for ethene formation, but suffered progressive deactivation. The use of strongly co‐ordinating solvents and microporous supports gave rise to longer catalyst life, at the expense of catalyst activity. Propyne also hydrogenated with 100% selectivity to propene, but without noticeable deactivation. It is concluded that strong co‐ordination of ethene is a likely cause of catalyst deactivation, whereas propene, conversely, co‐ordinates very weakly and does not hydrogenate. The best catalyst activity is achieved with a combination of a macroporous support and a weakly co‐ordinating solvent, but in this situation the catalyst is most easily poisoned when ethyne is hydrogenated.

Stimulatory effects of Ba2+ on contractile activity in the smooth muscle of the rat portal vein.

The effects on mechanical activity in rat portal vein of adding Ba2+, Sr2+ or Mg2+ (0.3--10 mM) to a tris-buffered solution (Na-tris) with 2.5 mM Ca2+ was investigated and compared to the effects of addition of Ca2+. Ba2+ induced a continuous tetanical activity and increased integrated force from threshold (0.3 mM) to sevenfold (10 mM). Addition of Sr2+ and Ca2+ had only minor effects on mechanical activity, whereas Mg2+ in increasing concentrations exerted an inhibitory effect. Contractures were elicited in K+-high tris solution with 2.5 mM Ca2+. The amplitudes of the contractures were not affected by added Mg2+, whereas Ca2+, Sr2+, and Ba2+ increased contracture force to some extent, the increase being highest for Ba2+ (twofold in 10 mM). Sucrose gap recordings of electrical and mechanical activity showed that added Ba2+ (0.3 mM) to Na-tris with 2.5 mM Ca2+ increased spike discharge and force/spike, the latter almost twofold. A corresponding addition of 0.3 mM Ca2+ had no effect. The effects of adding Sr2+ are very similar to that of added Ca2+, Mg2+ decreased spontaneous mechanical activity. Relaxation rates after K-contractures with 2.5 mM Ca2+, Ba2+, or Sr2+ were determined. No difference was found after K-tris with Ca2+ or Ba2+, whereas the veins relaxed faster after K-tris with Sr2+. We conclude tht Ba2+ acts as a constrictor of the smooth muscle in rat portal vein partly by initiating an increased spike discharge, and partly by increasing the entry or release of Ca2+ per spike, whereas the removal of Ca2+ is unaffected.

Construction and analytical applications of a liquid-state iodide-selective electrode with a metal complex as exchanging site

A new type of liquid-membrane iodide-selective electrode based on a 0.001M solution of tris(l,10-phenanthroline)ruthenium(II) iodide in 1,2-dichlorobenzene is described. The electrode has Nernstian behaviour down to 7×1O−6M iodide. It has good selectivity towards halide (kI, Cl=5.3×10−6 andkI, Br=1.6×10−4) and other inorganic ions, and a linear response to iodide at pH-values from 3 to 9. It can be used either in direct iodide analyses or in potentiometric titrations. Titration of halide mixtures or of pseudohalides is also possible. The method has been used for determining the free formaldehyde present in dispersing agents.