Effects of different substrate composition on biosynthesis of polyhydroxybutyrate-co-hydroxyvalerate by recombinant Escherichia coli

Cupriavidus necator is well known for its ability to accumulate polyhydroxybutyrate (PHB). When supplemented with propionic acid (or sodium propionate) in the growth medium, the bacterium is also able to synthesize polyhydroxybutyrate-co-hydroxyvalerate (PHBV). In order to increase the fraction of 3-hydroxyvalerate (3HV) in PHBV, we cloned the propionate permease gene prpP from C. necator and the propionyl-CoA synthase gene prpE from Cupriavidus taiwanensis and transformed into an Escherichia coli containing phaCAB operon of C. necator. The effects on PHBV accumulation in cells co-expressed with phaCAB and prpE or prpP in the media contained mixed carbon sources (glucose and sodium propionate) were evaluated. The HV fraction in PHBV increased when prpE or prpP was overexpressed in the cells. Concentrations of yeast extracts could also affect the fraction of HV. In addition, when glucose was replaced by sodium pyruvate, sodium succinate, or sodium gluconate, only PHB were detected in the recombinant strains.     

Thermal Decomposition of Some Chemical Compounds Used As Food Preservatives and Kinetic Parameters of This Process

Thermal decomposition processes of selected chemicals used as food preservatives such as sodium formate, sodium propionate, sodium nitrates(V and III) and sodium sulphate(IV) were examined by the derivatographic method. Based on the curves obtained, the number of decomposition stages and characteristic temperatures of these compounds have been found. Mass decrements calculated from TG curves ranged from 28.9% for sodium formate to 77.8% for sodium nitrate(V), while sodium sulphate showed a mass increment of 5.6%. Kinetic parameters such as activation energy (E _a ), frequency factor (A ) and reaction order (n ) were calculated from TG, DTG and T curves. Sodium formate shows the highest values of E _a and A which amount to 171.7 kJ mol^–1 and 5.8⋅10¹⁴ s^–1 , respectively, while the lowest ones, E _a =28.2 kJ mol^–1 and A =3.65⋅10² s^–1 belong to sodium nitrate(V). This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and nucleophilic displacement reactions of fluoropyrazine and 2-fluoroquinoxaline

An improved method for the preparation of fluoropyrazine (I) by halogen exchange and a synthesis of 2-fluoroquinoxaline (II) by a Balz-Schiemann reaction are presented. Compound I hydrolyzes slowly in 0.01N sodium hydroxide, rapidly in 1.07N sodium hydroxide at 26.00°. Compound II hydrolyzes 240 times faster than I in 0.01N sodium hydroxide at 26.00°. Hydrolysis of I in 6N hydrochloric acid at room temperature is slow. Compound I underwent nucleophilic reactions with formation of hydroxy, amino, methylamino, piperidino, benzylamino and anilinopyrazines. Pyrazinesulfonic acid was obtained from I and sodium sulfite and tetrazolo[1, 5-a]pyrazine (IV), a novel ring system, from I and sodium azide.     

Preparation of trisodium O-monoalkyl and O-monoaryl diphosphates

Trisodium O-methyl, O-butyl, O-phenyl, and O-(4-nitrophenyl) diphosphates were synthesized from sodium dimethylamido-O-(2-cyanoethyl) phosphate and O-alkyl-and O-aryl phosphoric acids. While in the previously described method, sodium hydroxide was used for the preparation of O-phenyl diphosphate, in our current work, we present an improved protocol, where sodium methoxide is used to increase the yields of O-alkyl and O-aryl diphosphates. The structures of final compounds were determined by ¹H NMR, ³¹P NMR, and IR spectroscopy. The sodium O-alkyl- and O-aryl diphosphate salts prepared by this method may be used for the study of biological activity of diphosphate analogues.     

The variations of the configurational and solvency properties of low molecular weight sodium polyacrylate with ionic strength

The configurational and solvency properties of low molecular weight sodium polyacrylate have been determined for a wide range of ionic strength solutions, from intrinsic viscosity data in the polymer literature.The variations of the polymer properties with ionic strength (I) are described very well by simple mathematical expressions. Thus, a linear relationship was found between the solvency parameter and 1/I ^(1/2), while the variations of the expansion factor and the radius of gyration with 1/I ^(1/2) were described by second order polynomials.LowI solutions (i.e. < 0.01) have a high solvency for sodium polyacrylate. In such solutions the polymer is in a highly expanded configuration. Thus, the radius of gyration of a typical, low molecular weight (ca. 5000 g mol^–1) sodium polyacrylate approaches the limiting value of ca. 4.5 nm atI<0.01.Conversely, high ionic strength solutions (i.e. >0.10) have a low solvency for sodium polyacrylate. In such solutions the polymer is in a virtually unexpanded configuration. Thus, the radius of gyration of a typical, low molecular weight sodium polyacrylate approaches the limiting value of ca. 2.0 nm atI>0.10.     

Crystallization of bisphenol-A polycarbonate induced by organic salts: Chemical modification of the polymer. I. Model reactions

The chemical modifications induced in diphenyl carbonate (DPC) by sodium arylcarboxylates between 200 and 250°C were studied to model the behavior of bisphenol-A polycarbonate – salt systems. Reaction between the salt and DPC produces sodium phenoxide, the phenyl arylcarboxylate corresponding to the salt, and carbon dioxide. The two latter compounds probably result from the decarboxylation of an unstable intermediate compound, viz., a mixed carboxylic carbonic anhydride. CO₂ and sodium phenoxide act as catalysts transforming DPC into phenyl salicylate via the formation of a small amount of sodium salicylate. Electrophilic acylation of sodium phenoxide by DPC is another possible but minor source of phenyl salicylate. Above 250°C, phenyl salicylate becomes unstable and pyrolyzes into o-phenoxybenzoic acid, which is immedicately esterified in the presence of DPC into phenyl o-phenoxybenzoate. In DPC + sodium o-chlorobenzoate systems, reaction between phenyl o-chlorobenzoate and sodium phenoxide is another source of phenyl o-phenoxybenzoate.     

Volumetric and conductometric studies on the interactions of dipeptides with sodium acetate and sodium butyrate in aqueous solutions at T = 298.15 K

Densities and conductivity data for the sodium carboxylate (sodium acetate and sodium butyrate)–dipeptides {(glycyl-l-glutamine and l-alanyl-l-glutamine) + water} systems were determined at T = 298.15 K. The apparent molar volumes of the peptides and the molar conductivity (Λ) of sodium acetate and sodium butyrate have been calculated. These data have been utilized to deduce the standard partial molar volumes (), standard partial molar volumes of transfer for dipeptide from water to aqueous sodium carboxylate solutions (Δ_tV^°), volumetric interaction coefficient, the limiting molar conductivity (Λ_°), and Walden product (Λ_°η). Both and Δ_tV^° for the dipeptides increase with increasing concentration of sodium carboxylate. The interpretation is that this result arises from the dominant interactions of the sodium carboxylate with the charged group and polar groups of peptides. The decrease in Λ_° of sodium carboxylate with increasing dipeptide concentration and nonconstant Walden product are attributed to the interactions of sodium carboxylate with peptide and friction resistance of the solvent medium.     

A new 3s–3d heterometallic polymer containing N‐methyliminodiacetic acid: synthesis,structure and characterization

A new complex {[Na₂(H₂O)₃(µ‐L)₂Cu]₄}_∞ (L = N‐methyliminodiacetic acid) has been synthesized and structurally characterized. The complex crystallizes in the monoclinic, space group C2/c, with the unit cell parameters a = 16.556(3) Å, b = 8.0622(13) Å, c = 12.671(2) Å, α = 90°, β = 95.849(2)°, γ = 90°. The central metal Cu (II) ion is coordinated with two nitrogen atoms and four oxygen atoms belonging to two ligands. Simultaneously, the sodium is six‐coordinated with oxygen atoms coming from the ligand and water molecule; the sodium atoms related are bridged by oxygen atoms, forming a sodium chain. The structure consists of CuL₂ moieties linked by sodium chain via the exo oxygen atoms of two ligands, forming a novel three‐dimensional structure. Moreover, elemental analysis, IR, UV‐vis, ESR spectroscopy and thermal stability were determined. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis of 4,6,8-Trisubstituted Methyl Azulene-2-carboxylates

It is shown that sodium (methoxycarbonyl)cyclopentadienide ( 1 ), which is easily accessible from sodium cyclopentadienide and dimethyl carbonate in THF, reacts with 2,4,6-trisubstituted pyrylium tetrafluoroborates 2a–d in boiling MeOH to afford the corresponding methyl azulene-2-carboxylates 4a–d in good yields. The corresponding 1-carboxylates 3 were not found (cf. Schemes 1 and 2).     

Foam Separation of Cadmium From Waste Water

Foam separation techniques are evaluated to determine if they would be feasible for removing cadmium (II) from waste water. Variables such as pH, ionic strength, collector concentration, and interfering ions were studied to determine their effects on separation. Sodium laury sulfate, sodium sterate, and hexadecyltrimethyl-ammonium bromide were chosen as the collector; Fe(OH)₃ and Al(OH)₃ were used as the adsorbing colloid, and sodium tripolyphosphate was used as modifier. It was found that cadmium could be effectively removed using various foam separation techniques. Cadmium levels were reduced from 5 ppm to 0.003 ppm in 60 minutes foaming with sodium laury sulfate. Foam separation of cadmium sterate with hexadecyltrimethyl-ammonium bromide was effective even at very high ionic strength, such as 1.0M NaNO₃.     

On the sodium and lithium ion affinities of some α-amino acids

The decomposition of 59 different cluster ions (generated by fast atom bombardment) consisting of two different amino acids and a sodium ion was analysed. The only fragment ions of significant abundance could be assigned to sodium ion-bound amino acids. Assuming that the most abundant ion in the fragment ion spectrum corresponds to the amino acid with the highest sodium ion affinity (SIA), the 20 common α-amino acids could be ordered with increasing sodium ion affinity as follows: Gly, Ala, Cys, Val, (Leu, Ile), Ser, Met, Thr, (Phe, Pro), Asp, Tyr, (Glu, Lys), Trp, Asn, Gln, His, Arg. Quantitative determinations were carried out by comparison of the lithium ion affinity (LIA) of Ala with that of dimethylformamide (DMF) in a fragment ion scan of the ion-bound dimer Ala—Li⁺—DMF. LIA(Ala) was calculated from LIA(Ala) = LIA(DMF) – (1/C)ln[I(AlaLi⁺)/I(DMF—Li⁺)], where the constant C was estimated from measurements of proton-bound amine–amino acid clusters. From fragment ion analysis of nine other Li⁺-bound α-amino acid dimers, the following lithium ion affinities were obtained: Gly 51.0, Ala 52.6, Sar 53.5, α-aminobutyric acid 53.7, glycine methyl ester 54.7 and Val 54.8. SIA(Ala) was estimated to be 75% of the lithium ion affinity and from fragment ion analysis of ten Na⁺-bound α-amino acid dimers the following sodium ion affinities were obtained: Gly 37.9, Ala 39.4, α-aminobutyric acid 40.3, Val 41.0, glycine methylster 41.0 and Sar 41.2.     

Adducts of NaOSiMePh2 Oligomers with THF and Cyclopentadienyl Iron Dicarbonyl Dimer

The sodium siloxide NaOSiMePh₂ is accessible from the reaction of Ph₂MeSiOH with sodium. The crystal structures of three hexameric double heterocubane compounds containing NaOSiMePh₂, one without additional donors and one each supported by THF and [CpFe(CO)₂]₂ are described. Using an excess of THF results in the formation of tetrameric sodium siloxide NaOSiMePh₂. The structures of (NaOSiMePh₂)₄·(THF)₄ (Aba2) and (NaOSiMePh₂)₄·2[CpFe(CO)₂]₂ (I4₁/acd) feature a heterocubane structure.     

Synthesis of monoalkenylated crown ethers and C-pivot cryptands

The synthesis of two N-(2-allyloxy)ethyl-substituted diaza-crowns and two C-pivot (allyloxy)methyl-substi-tuted cryptands is described. Controlled etherization of N,N-bis(2-hydroxyethyl)-4,13-diaza-18-crown-6 with allyl bromide and sodium hydride gave N-(2-allyloxy)ethyl-N-(2-hydroxyethyl)-4,13-diaza-18-crown-6 in a good yield. This macrocycle was reacted with sodium hydride and tetrahydrofurfuryl chloride or 3,3-dimeth-ylbutyl tosylate to give expected N-(2-allyloxy)ethyl-N'-tetrahydrofurfuryloxy)ethyl-[or (3,3-dimethylbutoxy)-ethyl]-substituted products 3 or 4 . 6,13-Dimethylenyl-14-crown-4 ( 9 ) and 9,19-dimethylenyl-20-crown-6 ( 10 ) were treated with mercuric acetate, followed by sodium borohydride in strong base to give macrocyclic diols 11 and 12 , respectively. These diols were reacted with sodium hydride and the ditosylate derivative of allyloxymethyl-substituted triethyleneglycol 13 to produce the C-pivot (allyloxy)methyl-substituted macrotri-cycles 6 and 7 .     

Ion binding in sulfonate-containing polyelectrolytes

Emf measurements have been used to study the activity and the extent of sodium ion binding to several polyelectrolytes, poly(styrenesulfonate) (PSS), poly(2-acrylamido-2-methylpropanesulfonate) (PAMS), poly(3-methacryloyloxypropane-1-sulfonate) (PMOS), and copoly[(N-t-butylacrylamide)-(2-acrylamido-2-methylpropanesulfonate)] (NB–AMS) (mole ratio 3.8:1). The activity coefficient of sodium ion in Na-PAMS and Na-PMOS without added salt is found to be in the range from 0.1 to 0.3 and is insensitive to changes in polymer concentration. However, it increases with increasing concentration of the added salt. The extent of sodium ion binding at a given sodium ion concentration, as estimated from the activity data for some sodium and tetrabutylammonium (TBA) salts, decreases in the order Na-PAMS ≈? Na-PMOS > TBA–PAMS > TBA–(NB–AMS). This indicates that a significant portion of the binding is attributed to the binding of TBA⁺ ions. Also compared are the results of ion binding in Na-PAMS and Na-PSS as a function of ionic strength. At low ionic strength (<1.0M), the order of binding strength is Na-PAMS > Na-PSS, while the order is reversed at high ionic strength (>1.0M). This finding is in good agreement with data obtained by dilatometry and viscometry.     

Aggregation number of aqueous sodium cholate micelles from mutual diffusion measurements

With reported values ranging from about 3 to 16, the aggregation number of aqueous sodium cholate micelles is not well established. To provide new information on the aggregation of a bile salt, Taylor dispersion is used to measure the binary mutual diffusion coefficientD of aqueous sodium cholate at concentrations from 0.001 to 0.100 mol-dm^-3 at 25°C. The results are compared with calculatedD values based on the association equilibrium nCholate^- + βnNa⁺ ⇋ (NaβCholate) _n ^(β-1)n wheren is the aggregation number and β is the degree of sodium counterion binding. Fitting the association model to the diffusion data givesn = 3.9±0.6 and β = 0.21 ±0.08. In contrast to the drop inD with increasing concentration of sodium cholate, the diffusion coefficients of sodium dodecylsulfate and other long-chain ionic surfactants increase above the critical micelle region. The ent diffusion behavior of the surfactants is related to changes in the driving forces and mobilities caused by ion association.     

STEREOCHEMISTRY OF SIX-COORDINATE OCTAHEDRAL SILICON(IV) COMPLEXES CONTAINING 2,2-BIPYRIDINE

Abstract

[Si(bpy)₃]⁴⁺ (bpy = 2,2′-bipyridine), synthesized from Sil₄ and 2′.-bipyndine. was optically resolved by a chromatographic method using an SP-Sephadex C-25 column as an adsorbent and a 0.16M aqueous solution of sodium (2R,3R)-(-)-O,O′-dibenzoyltartrate as an eluent. The optical isomers were characterized by measurement of their electronic absorption, circular dichroism, and ¹H NMR spectra. The chromatographic resolution of [SKbpyb]⁴⁺ was also attempted with an aqueous solution of potassium [(2R,3R)-(+)-tartrato]antimonate(III). sodium (2R,3R)-(+)-hydrogentartrate, and sodium (2R,3R)-(+)-tartrate as eluents. Force-field calculations were used to elucidate the chromatographic elution mechanism. [Si(OH)₂(bpy)₂]I₂was also synthesized from Sil₄ and 2′,-bipyridine. The optical resolution of this complex was achieved with sodium [(2R,3R)-(+)-tartrato]antimonate(III).     

Random homogeneous sodium sulfonate polysulfone ionomers: Preparation,characterization, and blend studies

The sodium salts of randomly sulfonated polysulfone (Na-SPSF), derived from 1,1′-sulfonylbis-[4-chlorobenzene] with 4,4′-(1-methylethylidene)-bis-[phenol], were prepared over the composition range of 3–30 mol% sodium sulfonate, using improved procedures in which the sulfonating complex was introduced into an intensely agitated polymer solution. In contrast to earlier work, T_g was found to increase nonlinearly with sodium sulfonate content. A SAXS study provided no evidence of ionic clustering in these polymers. Binary blends of Na-SPSFs differing only in composition were prepared by casting films from solution, and their phase behavior was studied by dynamic mechanical analysis after annealing at 250°C. It was found that the blends were miscible up to a composition difference of about 9–10 mol% sodium sulfonate. Using this fact it was possible to calculate a value for χ_ABn of 200–250, where χ_AB represents the segmental interaction parameter between unmodified and modified repeat units, and n is the degree of polymerization. Uncertainty in the degree of ionic association places a degree of uncertainty on the effective value of n and therefore on χ_AB. The product, however, is independent of any assumptions regarding molecular associations.     

Microcalorimetric studies on the antimicrobial actions of different cephalosporins

Microcalorimetry was applied to study the effect of cephalosporins (cefazolin sodium and cefonicid sodium) on the E. coli growth. The microbial activity was recorded as power-time curves through an ampoule method with a TAM Air Isothermal Microcalorimeter at 37°C. The parameters such as the growth rate constant (k), inhibitory ratio (I), the maximum power output (P _m) and the time corresponding to the maximum power output (t _m) were calculated. The change tendencies of k, with the increasing of concentration (C) of the two cephalosporins, are similar which show that cefazolin sodium and cefonicid sodium have the same inhibitory mechanism. The experimental results reveal that cefonicid sodium has a stronger antibacterial activity towards E. coli than that of cefazolin sodium and this was coincide with the clinical manifestations.     

Partial Molar Volumes of Amino Acids and Peptides in Aqueous Salt Solutions at 25°C and a Correlation with Stability of Proteins in the Presence of Salts

Partial molar volumes for a homologous series of amino acids and peptides have been measured in aqueous 1M sodium acetate, sodium thiocyanate, and sodium sulfate at 25^°C. These data have been utilized in conjunction with the data in water to deduce partial molar volumes of transfer V _2,m ⁰(tr) from water to these aqueous salt solutions. The volumes of transfer for the amino acids and peptides are found to be positive. The interpretation is that this result arises from the dominant interaction of the sodium salts with the charged centers of amino acids and peptides. Thermal denaturation of the structurally homologous proteins lysozyme and -lactalbumin has been studied in the presence of these salts. Significant thermal stabilization of hen egg-white lysozyme has been observed in the presence of sodium acetate and sodium sulfate. However, the thermal stabilization observed for -lactalbumin is very small in the presence of these salts and sodium thiocyanate leads to a lowering of its thermal denaturation temperature. The rise in the surface tension of aqueous salt solutions with salt concentration has been correlated with the calorimetric and volumetric measurements. The results show that V _2,m ⁰(tr) depends less on the type of electrolyte than on the ionic strength of the solution. The V _2,m ⁰(tr) values correlate very well with the increase in the surface tension of aqueous salt solutions, indicating significant role of surface tension in interactions of amino acids, peptides, or protein with the salts.     

Sodium “stuffed” Ba2−xSrxFe4O8 ferrites: new cationic conductors

Sodium insertion in the tetrahedral layer structure of the ferrites Ba_2−xSr_xFe₄O₈ was performed by solid state reaction at 1220 K in air. Superstoichiometric oxides with the actual formula (Ba_2−xSr_x)_1−y/4Na_yFe₄O₈—y0.56; 0.60Ba/Sr1.67—were characterized by X-ray and neutron powder diffraction. The hexagonal unit-cell volume shows an increasing dependence on the sodium insertion when the Ba/Sr ratio reaches the largest values. The marked expansion of the c parameter is the likely signature of the location of the inserted sodium cations within the interlayer space. One-half of the sodium cations partly sits on the Sr(Ba) sites in octahedral coordination and the other half occupies extra octahedral and tetrahedral sites. ac conductivity measurements point to a cationic conductivity whose thermally activated regime—E_a 0.7 eV—evidenced from 570 K, is unsensitive to the sodium content. The bottleneck of the 2D sodium mobility regards the crossing of the oxygen triangular faces shared by the different polyhedra within the interlayer space.