Physical Properties of Highly Active Liquor Containing Molybdate Solids

The reprocessing of irradiated nuclear fuel at Sellafield produces a nitric acid based Highly Active Liquor (HAL) waste. The liquor, containing fission products and process additives, is concentrated in an evaporator in order to reduce the volume and is then stored in Highly Active Storage Tanks (HASTs) prior to vitrification. Caesium phosphomolybdate (CPM) is precipitated during the evaporation process and can convert to zirconium molybdate (ZM) during storage.During Post Operational Clean Out (POCO) of the HASTs, it is expected that their highly active content will be reduced by repeated cycles of washing using nitric acid and other reagents. Initial washings are likely to have a chemical composition comparable to concentrated HAL, becoming more dilute during the wash-out process. It is expected that the wash-out process will also recover significant quantities of molybdate solids (ZM, CPM or a mixture) from the HASTs.In order to determine the processing challenges from such washings during POCO, the physical properties of varying concentrations of non-active HAL simulants containing molybdate solids have recently been measured by the UK's National Nuclear Laboratory. The following measurements are presented and discussed:

• •Particle size distribution
• •Density
• •Settling behaviour of solids
• •Voidage of settled sediment beds
• •Viscosity
• •Yield stress
• •Influence of ZM morphology on physical properties

     

The adsorption of RNAse A,BSA and cytochrome c at the graphite powder|liquid interface using in parallel the adsorption isotherm plot and linear sweep voltammetry on graphite paste electrode

The adsorption of RNAse A, BSA and cytochrome c on graphite powder has been investigated using in parallel the adsorption isotherm plot and linear sweep voltammetry on a graphite paste electrode (g.p.e.). The principle of the latter depends on the determination by electrochemical oxidation of tyrosyl or tryptophan residues having access to the interface. Adsorption isotherms exhibit bimodal adsorption features with a cooperative phenomenon leading to the formation of a close-packed two dimensional surface phase. Protein molecules are adsorbed in a monolayer when the pH is different from the isoelectric point. This layer is built up by the entanglement of a double network:

• •A network of molecules irreversibly adsorbed side-on, where hydrophobic residues move from the core to the surface. The tertiary structure is likely altered. The new dimensions of these adsorbed molecules have been determined (surface area per molecule, thickness).
• •A network of molecules adsorbed end-on, lying between the irreversibly adsorbed molecules.

     

Recent studies of the interaction of rabbit dimeric IgA with its polymeric immunoglobulin receptor

Rabbit secretory components (SC) constitute a highly heteregeneous population of glycoprotein molecules that are present in secretions as free or bound forms to polymeric immunoglobulins (Ig). Two SC families are known, one of high molecular weight (⋍ 80 Kd) composed of five (perhaps six) domains related to Ig variable domains, and one of low molecular weight (⋍ 55 Kd) An account of our most recent experimental data is reviewed in this article. We have shown:

• 1.1) that both the high and low Mr SC families possess the same relative avidity for binding to dimeric IgA of the g-sublanguage;
• 2.2) that the first NH₂-terminal domain of SC derived from the high and low Mr polypeptides is necessary and sufficient for efficient non-covalent binding to dimeric IgA of the g-sublanguage;
• 3.3) that the low Mr SC polypeptide derives from the high Mr SC by the internal deletion of the entire second and third domains, suggesting that these domains are not involved in the binding reaction with polymeric Ig;
• 4.4) that the heterogeneity of rabbit secretory components is, in large part, due to the expression of several polymorphic forms (allotypes) susceptible to be recognized by specific alloantisera; the biochemical characterization of the three known SC allotypes (t61, t62 and t63) reveals that t62 and t63 are structurally very similar to each other and markedly divergent from the t61 homologue;
• 5.5) that by using non-cross-reactive alloantisera, the major immunodominant allotopes are confined within the COOH-terminal domains 3, 4 and 5 of SC;
• 6.6) that the location of the residues involved in the attachment of the carbohydrate unit within domain 1 varies according to the allotype: t61 is N-linked glycosylated at position 70, whereas about 75 % of t62 molecules are devoid of sugars; the remaining 25 % of t62 molecules are glycosylated at residue position 90; these oligosaccharide chain units are linked to asparagine residues in the acceptor site consensus sequence, Asn-X-Thr/Ser;
• 7.7) that the presence of the carbohydrate unit in domain 1 is not required for efficient binding of this domain to polymeric Ig: indeed, after enzymatic deglycosylation, domain 1 exhibits a relative binding avidity which is indistinguishable from that of the native glycosylated domain 1.

     

Binding energies of tyrosine kinase inhibitors: Error assessment of computational methods for imatinib and nilotinib binding

The binding energies of imatinib and nilotinib to tyrosine kinase have been determined by quantum mechanical (QM) computations, and compared with literature binding energy studies using molecular mechanics (MM). The potential errors in the computational methods include these critical factors:

• •Errors in X-ray structures such as structural distortions and steric clashes give unrealistically high van der Waals energies, and erroneous binding energies.
• •MM optimization gives a very different configuration to the QM optimization for nilotinib, whereas the imatinib ion gives similar configurations
• •Solvation energies are a major component of the overall binding energy. The QM based solvent model (PCM/SMD) gives different values from those used in the implicit PBSA solvent MM models. A major error in inhibitor—kinase binding lies in the non-polar solvation terms.
• •Solvent transfer free energies and the required empirical solvent accessible surface area factors for nilotinib and imatinib ion to give the transfer free energies have been reverse calculated. These values differ from those used in the MM PBSA studies.
• •An intertwined desolvation—conformational binding selectivity process is a balance of thermodynamic desolvation and intramolecular conformational kinetic control.
• •The configurational entropies (TΔS) are minor error sources.

     

Latest Developments in Proton Conductors

Solid proton conductors are receiving considerable attention, stimulated by the need of pollution control and with the objective to develop future microprotonics. The latest striking developments in the study of proton conductors are presented:

• i)Hydrogen containing perovskites, with a discussion of the nature and location of hydrogen inprotonic and electronic high-temperature superconductors;
• ii)Novel forms of hydrogen in disordered and mixed conductors, with the problems of the vibrational proton transfer assistance assumed by some authors and the independent proton dynamics evidenced by inelastic neutron scattering;
• iii)Frequency dependent conductivity and dielectric relaxation, including thermally stimulated current experiments in hydrated synthetic and biological gels (seeds);
• iv)Proton conducting membranes as candidates to replace Nafion®-like materials in H₂ (methanol) fuel cells.

     

Effects of static magnetic fields of erythrocyte rheology

The orientation of normal erythrocytes in a uniform static magnetic field (8 T maximum) has been investigated microscopically and photometrically.

• 1.(1) The intact erythrocytes were oriented with their disk planes parallel to the magnetic field because of the diamagnetism of the cell membrane components, particularly the transmembrane proteins (e.g., Band III, glycopholin) and the lipid bilayer.
• 2.(2) In contrast, the glutaraldehyde-fixed erythrocytes were oriented perpendicular to the field, perhaps because of the paramagnetism of the membrane-bound methemoglobin.
• 3.(3) The orientation was established within 5 s in a dilute suspension (5 × 10³cells μl⁻¹) as estimated from the change in light scattering after exposure to the magnetic field.

     

Calorimetric studies of CeCu AND CeMgCu alloys

Using different calorimeters, the following measurements have been carried out.

• 1.(i) The integral enthalpies of mixing of CeCu binary and some CeMgCu ternary liquid alloys,
• 2.(ii) The enthalpy of formation and the enthalpy of melting of the intermetallic compound CeCu₂.
• 3.(iii) The heat content of solid and liquid CeCu₂.

The observed concentration and temperature dependence of the measured values of the enthalpies of mixing as well as the glass-forming abilities of these alloys are explained on the basis of an association model.     

N–H stretching frequencies and the conformation of substituted ureas: an ab initio MO study

The dependence of N–H stretching-mode frequencies in representative di- and trialkyl ureas on the conformational state of the ureido group has been studied by ab initio MO calculations using HF/3-21G and HF/6-31G** basis sets. The molecules studied were 1,3-dimethylurea, 1-methyl-3,3-dimethylurea and 1-methyl-3,3-di-iso-propylurea. The principal conclusions from the ab initio results are:

• 1.the trans–trans conformer (N–H bonds trans to the CO bond) has N–H stretching bands with about 20–30 cm⁻¹ higher frequency than the respective cis–cis structure, in accord with earlier literature assignments based on experimental data;
• 2.the N–H stretching frequency interval in tri-substituted ureas is 15–20 cm⁻¹ higher than the N–H band position in the 1,3-disubstituted molecule studied, the effect being determined mostly by the higher N–H stretching force constant;
• 3.in the absence of the steric hindrance the stable rotameric forms of the ureido grouping are almost planar at HF/3-21G level of calculations, while HF/6-31G** calculations predict a slightly pyramidal structure at the nitrogen atoms in the trans–trans conformer;
• 4.in 1-methyl-3,3-di-iso-propylurea the steric influence of the two bulky iso-propyl groups cause a deviation from planarity of the N–H bond. The non-planar conformation is accompanied by a shift of the N–H stretching mode frequency towards higher values; and
• 5.the variations of the theoretically estimated N–H stretching-mode frequencies appear to be principally determined by changes in the N–H stretching force constants in the different molecules.

© 1997 Elsevier Science B.V.     

Phasenumwandlungserscheinungen in Lecithin/Wasser-Systemen

1. By means of differential-scanning-calorimetry the phase transition temperatures and -enthalpies were determined and evaluated for the three following lecithin/water systems: 1,2-dimyristoyl-lecithin/water; 1,2-dipalmitoyl-lecithin/water; 1,2-distearoyllecithin/water.
2. The preparation of the lecithin/water mixtures was made by adsorption of water from the gaseous phase. The adsorption isotherms were evaluated by the BET equation.
3. Four phase transitions were found for the monohydrates of the lecithins. The parameters depend systematically on the length of the alkyl residues.
4. In the heterogeneous two phase region the main-transition and the pre-transition occurred. The thermodynamical parameters of both transitions depend on the alkyl chain length.
5. Whole the results refer to the conclusion that the lecithin head group hydration is a stepwise process. The hydration of the first shell is finished if 5 to 6 molecules water per molecule lecithin are present, while the second hydration shell is complete when about 13 water molecules are adsorbed

     

Synthese et caracterisation de fluorotellurates IV alcalins et d'ammonium partie I. Etude du pentafluorotellurate IV de lithium LiTeF5

Lithium pentafluorotellurate (IV) LiTeF₅ has been prepared by different methods:

• •slow evaporation of a 1/1 mixture of lithium fluoride and tellurium dioxide or tellurium tetrachloride in anhydrous hydrogen fluoride,
• •heating a 1/1 mixture of lithium fluoride and tellurium tetrafluoride. LiTeF₅ is orthorhombic

(a = 9,52 Å b = 9,12 Å c = 11, 60 Å)     

Fourier transform infrared spectroscopic studies of the secondary structure and thermal denaturation of CaATPase from rabbit skeletal muscle

Fourier transform i.r. spectroscopy has been used to monitor structural alterations induced by thermal denaturation of the intrinsic membrane protein CaATPase in aqueous media. The protein has been isolated, purified and studied in five forms:

• 1.(i) In its native lipid environment after isolation from rabbit sarcoplasmic reticulum, both in H₂O and D₂O suspensions.
• 2.(ii) After both mild and extensive tryptic digestion has cleaved those residues external to the membrane bilayer.
• 3.(iii) Reconstituted in vesicle form with bovine brain sphingomyelin.

Fourier deconvolution techniques have been used to enhance the resolution of the intrinsically overlapped Amide I and Amide II spectral regions. Large spectral alterations apparent in the deconvoluted spectra occur in these regions upon thermal denaturation of the protein which are consistent with the formation of a large proportion of β-antiparallel sheet form. The alteration parallels the loss in ATPase activity. A mild tryptic digestion increases slightly the proportion of α-helix and/or random coil secondary structure. A thermal transition to a form containing a high proportion of β structure is still evident. Extensive tryptic digestion nearly abolishes the alpha helical plus random coil secondary structure, while producing a high proportion of β form which is resistant to further thermally induced structural alterations.Studies of CaATPase reconstituted into vesicles with bovine brain sphingomyelin reveal a higher proportion of β structure than the native enzyme, with further introduction of β structure on thermal denaturation. Both the utility of deconvolution techniques and the necessity for caution in their application are apparent from the current experiments.     

On ion-pair photoseparation and recombination in micellar aggregates

Perylene (Pe) and tetramethylbenzidine (TMB) have been photoionized under continuous or laser pulse excitation in cationic (Mi⁺), neutral (Mi⁰) or anionic micelles (Mi^-). In the latter case, Mi^- composed of sodium dodecyl sulfate (SDS) surfactant molecules have been swollen upon the addition of various hydrocarbons and the interfacial electric potential ΔΨ modified by electrolyte addition.From previous and present data, the following conclusions can be drawn:

• •(a) Intramicellar ultrafast geminate recombinations are promoted by increasing the micellar volume but counteracted when high electron mobility values characterize the swelling agent;
• •(b) Recombinations involving the hydrated electron ρ^-_aq appear to be suppressed in negatively as well as in positively charged Mi and to occur in Mi⁰ to an extent depending upon the chromophore cation;
• •(c) The overall photoionization yield ø_ion of Pe or TMB is found to increase linearly as ΔΨ becomes more negative; such ΔΨ variation is shown to affect ø_ion through the primary electron ejection stage though the ionization threshold energy does not seem to be appreciably modified;
• •(d) For Mi^- aggregates, the photoionization efficiency curves ø_ion=f(λ) show a linear dependence on the photon excess energy in the threshold region; within such an energy range, the ø_ion(λ) curves would thus approximate the variation with λ of a primary ionization yield of the solute;
• •(e) As a corollary, it may be suggested that the shape of the ø_ion(λ) curves relative to homogeneous liquid solutions would be essentially governed by solute cation-ρ^-_solv recombination reactions.

     

Hydrogen Bonding in Protic Ionic Liquids: Reminiscent of Water

Similarities and differences : Far‐infrared spectra of protic ionic liquids could be assigned to intermolecular bending and stretching modes of hydrogen bonds. The characteristics of the low‐frequency spectra resemble those of water. Both liquids form three‐dimensional network structures, but only water is capable of building tetrahedral configurations. EAN: ethylammonium nitrate, PAN: propylammonium nitrate, DMAN: dimethylammonium nitrate.

     

Application of radiation technology in biomedical materials; Fundamentals and applied

• 1.1) IMMOBILIZATION OF HEMOGLOBIN Hemoglobin has been immobilized into Poly Hema Matrix. To increase, Mechanical resistance, at first, CO was coodinated, after immobilization CO was eliminated by photo illumination by visible light from a W lamp and then O₂ was introduced. Oxygencoordiation ability was not damaged by immobilization.
• 2.2) REDUCTION MECHANISM OF ENZYME BY THE USE OF PULSE RADIOLYSIS Elementary process of Reduction Mechanism of Myoglobin, Hemoglobin, HRP and Cytochrome Oxidase were investigated in the time range of μsec≈nsec. In the of Cytochrome Oxidase, these are 4 metal ions inside of the Enzyme. The exact step of reduction of this enzyme was elucidated

.     

Photodissociation of gas-phase I−3: product branching in the visible and UV regions

Photodissociation of the gas-phase triiodide anion, I⁻₃, was investigated using photofragment mass spectrometry. The photofragment yield (PFY) and photoproduct branching fractions were determined from the observed mass spectra in the wavelength range 270–540 nm (2.3–4.6 eV). The measurement revealed that:

• 1.I⁻₃ photodissociation occurs with the production of I⁻ and I⁻₂ fragments in the whole energy range studied,
• 2.the branching ratio of I⁻ versus I⁻₂ production depends strongly on the excitation energy.

These experimental findings clearly demonstrate the nonadiabatic nature of the I⁻₃ photodissociation dynamics.     

Synthese et caracterisation de fluorotellurates IV alcalins et d'ammonium partie II: Etude des fluorotellurates d'ammonium NH4TeF5 et (NH4)2TeF6

New methods of synthesis:

• •reaction of aqueous or anhydrous HF with TeO₂ and NH₄F or NH₄HF₂, with (NH₄)₂TeCl₆
• •reaction of TeF₄ with NH₄F or NH₄HF₂
• •reaction of NH₄HF₂ with TeO₂

have been investigated for NH₄TeF₅ and a new compound (NH₄)₂TeF₆. The resulting compounds have been analysed and characterized.     

899 — A potentiometric study on the redox properties of hemoglobin from Camelus dromedarius

A potentiometric study of the redox properties of hemoglobin from Camelus dromedarius has been performed, with the aim of having a better insight in the structure-function relationships of this protein; data on human hemoglobin have been included for comparative purposes. Analysis of the experimental data has shown:

• 1.the existence of intermediate conformers (neither R nor T) in the oxidized form of dromedary hemoglobin;
• 2.the amino acid groups involved in the oxidation Bohr effect of dromedary and human hemoglobins are likely to be the same; thus, only invariant amino acid residues seem to be involved in this effect.

     

Thermal decomposition of algae bloom biomass

The algae bloom biomass in the water reservoir ‘Rybnik’ is an important problem, and not only in Poland [1,2]. The algae growth in the water affects its odour, colour, taste and quality [3]. Algae bloom biomass removed from water can be treated in the following ways:

disposal in sanitary landfills

storage on special dumping grounds

fermentation

dewatering and incineration

In this paper the physicochemical composition and thermal analysis of the biomass of algae bloom dried at 378 K or in the open air are described. Thermal analytical measurements were made in an air atmosphere.