Graham's Salt Research Articles

Mild hydrolysis of chemically stable valerolactams by a biocatalytic ATP-dependent system fueled by metaphosphate.

Medium-sized 5- and 6-membered ring lactams are molecules with remarkable stability, in contrast to smaller β-lactams. As monomers, they grant access to nylon-4 and nylon-5, which are alternative polyamides to widespread caprolactam-based nylon-6. Chemical hydrolysis of monocyclic γ- and δ-lactams to the corresponding amino acids requires harsh reaction conditions and up to now, no mild (enzymatic) protocol has been reported. Herein, the biocatalytic potential of a pair of heterologously expressed bacterial ATP-dependent oxoprolinases - OplA and OplB - was exploited. Strong activity in the presence of excess of ATP was monitored on δ-valerolactam and derivatives thereof, while trace activity was detected on γ-butyrolactam. An ATP recycling system based on cheap Graham's salt (sodium metaphosphate) and a polyphosphate kinase allowed the use of catalytic amounts of ATP, leading to up to full conversion of 10 mM δ-valerolactam at 30 °C in aqueous medium. Further improvements were obtained by co-expressing OplA and OplB using the pETDuet1 vector, a strategy which enhanced the soluble expression yield and the protein stability. Finally, a range of phosphodonors was investigated in place of ATP. With acetyl phosphate and carbamoyl phosphate, turnover numbers up to 176 were reached, providing hints on a possible mechanism, which was studied by 31P-NMR.

Mechanochemical Phosphorylation of Acetylides Using Condensed Phosphates: A Sustainable Route to Alkynyl Phosphonates.

In pursuit of a more sustainable route to phosphorus-carbon (P-C) bond-containing chemicals, we herein report that phosphonates can be prepared by mechanochemical phosphorylation of acetylides using polyphosphates in a single step, redox-neutral process, bypassing white phosphorus (P4) and other high-energy, environmentally hazardous intermediates. Using sodium triphosphate (Na5P3O10) and acetylides, alkynyl phosphonates 1 can be isolated in yields of up to 32%, while reaction of sodium pyrophosphate (Na4P2O7) and sodium carbide (Na2C2) engendered, in an optimized yield of 63%, ethynyl phosphonate 2, an easily isolable compound that can be readily converted to useful organophosphorus chemicals. Highly condensed phosphates like Graham's salt and bioproduced polyphosphate were also found to be compatible after reducing the chain length by grinding with orthophosphate. These results demonstrate the possibility of accessing organophosphorus chemicals directly from condensed phosphates and may offer an opportunity to move toward a "greener" phosphorus industry.

Nanoarchitectonics of Layer-by-Layer (LbL) coated nanostructured lipid carriers (NLCs) for Enzyme-Triggered charge reversal

HypothesisCombined usage of Layer-by-Layer (LbL) coating and alkaline phosphatase (ALP) - responsive charge reversal strategies can improve the cellular internalisation of the colloidal drug delivery systems by also decreasing their cytotoxic effects. ExperimentsAnionic core NLCs were formed by combining the melt emulsification method and ultrasonication. The resulting core NLCs were coated sequentially first with protamine (Prot NLCs) and then with sodium tripolyphosphate (TPP) or sodium polyphosphate (Graham's salt, PP) generating TPP or PP NLCs, respectively. The developed NLCs were characterised regarding their size and zeta potential. Enzyme-induced charge reversal of the TPP and PP NLCs was evaluated by zeta potential measurements upon their incubation with alkaline phosphatase (ALP). In parallel, time-dependent phosphate release was monitored in the presence of isolated as well as cell-associated ALP. Morphological evaluations were performed by scanning electron microscopy (SEM) studies. Moreover, cell viability and cellular uptake studies were carried out in vitro on Caco-2 cells. FindingsThe core NLCs were obtained with a mean size of 272.27 ± 5.23 nm and a zeta potential of −25.70 ± 0.26 mV. Upon coating with protamine, the zeta potential raised to positive values with a total change up to Δ29.3 mV also displaying an increase in particle size. The second layer coating with TPP and PP provided a negative surface charge. Subsequent to ALP treatment, the zeta potential of the TPP and PP NLCs reversed from negative to positive values with total changes of Δ8.56 and Δ7.47 mV, respectively. Conformably, significant amounts of phosphate were released from both formulations. Compared with core NLCs, improved cellular viability as well as increased cellular uptake were observed in case of Prot, TPP and PP NLCs.

Synthesis and factorial design applied to a novel chitosan/sodium polyphosphate nanoparticles via ionotropic gelation as an RGD delivery system

Chitosan nanoparticles have been extensively studied for both drug and protein/peptide delivery. The aim of this study was to develop an optimized chitosan nanoparticle, by ionotropic gelation method, using 32 full factorial design with a novel polyanion, sodium polyphosphate, well known under the trade name Graham salt. The effects of these parameters on the particle size, zeta potential, and morphology and association efficiency were investigated. The optimized nanoparticles showed an estimated size of 166.20±1.95nm, a zeta potential of 38.7±1.2mV and an efficacy of association of 97.0±2.4%. The Atomic Force Microscopy (AFM) and Scanning Electronic Microscopy (SEM) revealed spherical nanoparticles with uniform size. Molecular interactions among the components of the nanoparticles and peptide were evaluated by Fourier Transform Infrared Spectra (FTIR) and Differential Scanning Calorimetry (DSC). The obtained results indicated that, the developed nanoparticles demonstrated high biocompatible, revealing no or low toxicity in the human cancer cell line (Caco-2). In conclusion, this work provides parameters that contribute to production of chitosan nanoparticles and sodium polyphosphate with desirable size, biocompatible and enabling successful use for protein/peptides delivery.

31P NMR spectroscopic studies of the influence of the environment in the degradation process of the Graham's salt

The “Graham's salt” is a vitreous sodium polyphosphate with a general formula of Na(n+2)PnO(3n+1). It is used in the ceramics industry as a deflocculant additive in a matrix of sodium silicate with different SiO2:Na2O ratios. The influence of the environment in which the Graham's salt is usually placed on its degradation into smaller particles has been studied by 31P NMR spectroscopy at several temperatures on solutions with 7% of Graham's salt in sodium silicate with Rw=1.6, 2.0, 3.3, in sodium carbonate 0.15M, in sodium hydroxide 0.10M and 1.0M and in water. The signals in the 31P NMR spectra of Graham's salt in D2O, depending on their chemical shift δ (ppm) and multiplicity, have been assigned to the different phosphorous atoms of the skeleton of the several polyphosphates that are present in the solution. The integration of these signals at different temperatures has enabled the collection of kinetic and thermodynamic data: kinetic constants k (s−1), activation energy Ea, ΔH‡ and ΔS‡. Results indicate that the environment is a factor which favours the degradation of polyphosphates, since with increasing basicity of deflocculating solutions the rate of degradation is faster. White gel obtained as a final product of the degradation process of Graham's salt has been analyzed with 31P NMR spectroscopic measurements identifying orthophosphate and pyrophosphate as the main final species of the degradation of Graham's salt.

Verification Concerning the Relative Superiority of a Cellulosic Fabric with Regard to Polyester in Terms of Flammability

In order to prove the superiority of cotton fabric to polyester with regard to flammability, we have studied the effect of Graham's salt as a moderate and nondurable finish on the flammability of pure polyester and cotton fabric. The laundered bone-dried, weighed fabrics were impregnated with suitable concentration of aqueous Graham's salt solutions by means of squeeze rolls and drying at 110°C for 30 min. They were then cooled in a desiccator, reweighed with analytic precision, and kept under ordinary conditions before the accomplishment of the vertical flame test. The optimum add-on value to impart flame retardancy was about 43.65% for polyester fabric and 36.78% for cotton fabric. The results obtained comply with the Coating Theory. Moreover, the superiority of cotton fabric to polyester fabric in terms of combustibility has been deduced.

Mechanical behavior of metaphosphate glasses used as coating on metals in relation to their structure and preparation method

The purpose of the present work was to investigate the mechanical behavior of metaphosphate glass coatings of the Na2O-CaO-P2O5 system on steel substrates. These coatings may be used as thermal barriers or to give anti-corrosion protection. Coacervates of glasses under consideration were obtained by a coacervation process, from Graham's salt and deposited on aluminized steel substrate. Chemical composition of coacervate phases was improved by the choice of cations and addition of a filler to reduce the residual stresses in glass metal joints due to the thermal expansion coefficient mismatch. The chemical and mechanical properties of both the coating and the interface were studied by energy dispersive spectrometry (EDS) and hardness measurements. It was shown that an alumina layer is formed by the reaction between the phosphates compounds during curing. This layer acts as a barrier for the iron diffusion. The fracture toughness of the glass coating was investigated by Vickers indentations. Inasmuch the cracks are of the Palmqvist form, the Evans and Charles formula holds for calculating KIC. A value near 0.85 MPa m1/2 was found for all the glasses investigated. Residual stress distribution was calculated. The glass coating was in compression and residual stresses were reduced by the interlayer formation. A good adhesion was found since cracks produced by indentation near the glass steel interface propagated in the coating rather than along the interface.

Dehydroxylation mechanisms of polyphosphate glasses in relation to temperature and pressure

The mechanisms of dehydroxylation of some polyphosphate glasses have been studied between ambient temperature and 1000°C while the residual pressure of water vapor above the sample was controlled. The results indicate that devitrification of the glass affects the water release. Only one mechanism takes place both under atmospheric pressure with an inert flowing gas and under a residual water pressure of 5 mbar. Until the fixed residual water vapor pressure is larger than 10 −3 mbar, only one mechanism is present. But when the residual pressure of water vapor is decreased to a value of 10 −3 mbar, several mechanisms occur for both a Graham's salt and a sodiumcalcium polyphosphate glass. We observe water release governed by a mechanism of nucleation-growth of nuclei. We have determined the activation energy of this reaction and proposed mechanisms for the dehydroxylation of polyphosphate glasses.

ATP production from polyphosphate in Acinetobacter strain 210A

In cell-free extracts of Acinetobacter strain 210A polyphosphate: AMP phosphotransferase and adenylate kinase activity was measured. Polyphosphate glucokinase and polyphosphate dependent NAD kinase were not detected. The specific activity of polyphosphate: AMP phosphotransferase was found to be 43 nmol · min-1 · mg-1 protein in presence of 1 mmol · l-1 AMP. The adenylate kinase reaction had an equilibrium constant ([ATP] [AMP] [ADP]-2) of 0.7, an activity of 54 nmol · min-1 · mg-1 protein, and was almost completely inhibited by 0.3 mM P1,P5-di(adenosine-5′)-pentaphosphate. ATP was formed through the combined action of polyphosphate: AMP phosphotransferase and adenylate kinase in cell-free extracts from bacterial polyphosphate and from chemically prepared polyphosphate (Graham's salt). A spectrophotometric method for the continuous monitoring of polyphosphate: AMP phosphotransferase is also presented.

Vibrational spectroscopic studies of a new class of oligophosphate glasses of biological interest

AbstractVitreous biomaterials with chemical composition similar to that of bone may be formed by treating mixtures of vitreous sodium polyphosphate, Graham's salt and hydroxylapatite. The Raman and infrared spectra of a range of such materials are reported and discussed in relation to their structure.

Studies on complex polyphosphates of N-heterocyclic bases

A few novel complex polyphosphate derivatives of the general composition (BHPO3)n (where B is pyridine, substituted methylpyridines, quinoline, morpholine, benzimidazole, and imidazole) have been synthesized by precipitation techniques. Viscosity average molecular weight values indicate their polymeric character which is similar to that of Graham's salt and other linear chain polymers. The viscosity average molecular weights of the precipitated polyphosphates have been found to be dependent on the basicities of the heterocyclic amines. The relation between the Mw and Rg values determined by paper chromatography also confirm their polymeric nature. Conductivity measurements at different dilutions indicate their polyelectrolytic behavior analogous to the Fuoss model.

Synthesis and studies of some organic poly(ammonium phosphate)s, 1

AbstractLong chain organic poly(ammonium phosphate)s (1a–g and 2) were prepared by a precipitation technique by reaction of poly(lithium phosphate) with organic ammonium salts. Their compositions were established by nitrogen and phosphorus analyses and their polymeric nature was confirmed by molecular weight determinations via end group titrations and by the viscosity method. Studies of conductance at different concentrations indicated their polyelectrolytic behaviour. Paper chromatographic studies supplied additional evidence of a long chain polymeric structure, like Graham's salt and poly(lithium phosphate).

Preparation and properties of pentameta- and heptametaphosphate

Useful quantities of pentameta- and heptametaphosphate can be isolated from Graham's salt by fractional precipitation followed by ion-exchange chromatography on a large column of QAE-Sepahdex A-25 gel. The IR spectra of a series of cyclic phosphates from trimeta- to octametaphosphate were measured and the characteristic absorption bands for the cyclic structures were indicated. The gel chromatographic behavior of the series of cyclic phosphates on a Sephadex G-25 column showed that their elution volumes increase with their degree of polymerization and that there is a linear relationship between the distribution coefficient and the logarithm of the degree of polymerization. The distribution of individual cyclic phosphates in Graham's salt was determined by combining gel chromatography on a Sephadex G-25 column with ion-exchange chromatography on a QAE-Sephadex A-25 column.

Infrared study on glass semiconducting materials xNaPO 3·yNaVO 3

Inorganic semiconducting glasses of composition xNaPO 3·yNaVO 3 with the molar ratio P/V ranging between 1 and 200 have been prepared by melting a mixture of (NaPO 3) x (Graham's salt), V 2O 5 and Na 2CO 3. Part of vanadium is reduced from V(V) to V(IV) with evolution of O 2. The percentage of V(IV) related to total vanadium is determined for each sample. The i.r. spectra of the materials with different molar ratios are presented and discussed both in relation to those of the polyphosphate and polyvanadate with different chain lengths, and in relation to the spectrum of the vanadyl ion VO 2+. Evidence of the presence of this ion is also given by measurements in the near i.r..

Molecular - weight distribution in Graham's salt: Dependence on conditions of formation

A detailed study of the distribution of molecular weights in several samples ofGrahams salt, a long-chain polyphosphate, prepared under different conditions, has been presented. The samples were prepared by heating sodium dihydrogen phosphate at fixed temperatures of 700 and 800 °C and quenching the melt after heating for various durations of time. The distribution curves clearly show a marked dependence on the conditions offormation. For the same duration of time an increase in temperature broadens the distribution. Similarly, for the same temperature of heating the increase in time ofheating also broadens the distribution.

Viscosity behaviour of solutions of Graham's salt in media of different dielectric constants

Reduced viscosity (ηsp/C) of an aqueous solution ofGrahams salt decreases if a water-miscible organic solvent like acetone is added to it. The reduced viscosity-concentration (ηsp/C-C) curve in water is concave upward but in 10% solution of acetone ethanol or dioxane a maximum is observed. The behaviour is reminiscent of what is observed on successive addition of a neutral salt. Just as after addition of a swamping excess of an electrolyte theηsp/C-C curve becomes a straight line, in presence of 25% solution of any of the three organic solvents studied, curves became straight lines in the case of low-molecular-weight samples ofGrahams salt. An expected increased interaction between polyanions probably does not take place because of formation of ion-pairs in solvents of low dielectric constant and coiling of the polyelectrolyte chain takes place. Whereas, apparently the effect of addition of salt is similar qualitatively to the effect of addition of a non-solvent, there is one important and significant difference. This is reflected in the plot of reduced viscosity versus concentration of the added nonsolvent. Theηsp/C of a 0.3% solution ofGrahams salt falls first slowly and then sharply with increase in the concentration of the non-solvent (acetone, ethanol or dioxane). In the case of addition of salt the reduced viscosity falls sharply firstand then slowly. Whereas in one case the curve is concave in shape it is convex in the other. A plot ofηsp/C vs.D, the dielectric constant of the medium, shows that the reduced viscosity increases sharply at first with increase in dielectricconstant but seems to stabilize at higher values ofD.

Equilibrium ring concentrations and the statistical conformations of polymer chains: Part 9. Sodium metaphosphates in Graham's salt

The molar cyclization equilibrium constants K x for oligomeric metaphosphates (NaPO 3) x in high molecular weight sodium phosphate melts at 1000K are calculated using a rotational isomeric state model to describe the statistical conformations of the corresponding open chain molecules. The model is based on a previously published analysis of the molecular structure of the polyphosphate chain. Each skeletal bond is assigned to one of three rotational states in trans ( ø=0°) and gauche ( ø=±120°) positions, and the interdependence of adjacent pairs of bond rotational states is taken into account by assuming that only Coulombic interactions between charged non-bonded atoms of the chain separated by eight or fewer chemical bonds need to be considered. The probabilities that polyphosphate chains (OPO 2) x (with x=3−10) will intramolecularly cyclize are calculated by computing the statistically weighted fraction of the 3 2 x−3 conformations defined by the rotational isomeric state model that have their termini in close proximity for ring formation. Molar cyclization equilibrium constants calculated by this direct computational method are compared with experimental values deduced from data of Thilo and Schülke, as well as with values calculated assuming that the polyphosphate chains obey Gaussian statistics.

Analysis of Graham's salt by differential thermal analysis, differential scanning calorimetry and thermogravimetry

Analysis of Graham's salt by differential thermal analysis, differential scanning calorimetry and thermogravimetry

Ion-exchange Chromatographic Analysis on the Chain Length of Polyphosphate Products

Abstract The ion-exchange chromatographic technique was used in order to find the average chain number of a polyphosphate product. For the assignment of the nth polymer in the obtained chromatogram, the dependence of the distribution coefficient, Kd, on the eluent concentration examined by the use of both 20-cm and 60-cm resin columns. A lower series of polyphosphate was included in a relatively large amount in order that the average chain number based on the chromatographic analysis could be duly appreciated only for the case of basic polymers with lower molecular weights. For a product “Graham Salt” with a number of phosphate links, the higher series of polyphosphate could not be desorbed entirely from the resin column; the accurate estimation of the average number was, then, improbable. The viscosity method is also not advisable to use the computation of a mean polymerization number in the polyphosphate with a low molecular weight. An attempt was made to improve the data on the average chain number by the viscosity measurements together with the chromatographic analysis of the polymer constituent.

Hot-atom chemistry of polyphosphates—III: Reactions of 32P resulting from neutron activation of higher polymer

For the study of the reactions of 32P in polymer phosphate during neutron activation, polyphosphates with mean chain lengths, n ̄ , of 10 and ∞ (Graham's salt) were used as target materials. The yield of recoil 32P monomer was found to be much lower than that for tripolyphosphate. But three oxidation states of radiophosphorus of (+1), (+3) and (+5) were found in the recoil species. However, the distribution of the three states could be varied by changing the irradiation condition and target materials. The specific activity decreased with increase of polymer chain length. Bond breakage of polyphosphate during alkaline hydrolysis occurred in units of four (PO 3) −, and the accumulation of tetramer and the further hydrolysis of this species led to the conclusion that radioactive labelling occured only at the end atom of the long phosphorus chain.