Mechanism of glass ampoule breakage prevention during the freeze-drying process of sodium thiopental lyophilization products on addition of sodium chloride

Glass ampoule breakage during the freeze-drying process was prevented by the addition of sodium chloride to the formulation of lyophilization products of sodium thiopental. In order to clarify the ampoule breakage prevention mechanism, the physicochemical behavior of the freeze-drying process was monitored by simultaneous XRD-DSC measurements and thermal mechanical analysis (TMA). During the freezing process of formulated solution, the smaller heat of fusion of crystallized ice with the addition of sodium chloride was observed in comparison to that without sodium chloride. Although a greater amorphous portion remained, a higher crystal habit of hexagonal ice was reproducibly observed in the XRD patterns with the addition of sodium chloride during the freezing process. In the measurement of TMA, the scattering of the thermal expansion rate of formulated solution was significantly reduced by the addition of sodium chloride. These observations indicated that the addition of sodium chloride minimized the scattering of the thermal expansion rate and might be a cause for the inhibition of glass ampoule breakage during the freeze-drying process.     

Preconcentration of antimony(III) from water with thionalide loaded on glass beads with the aid of collodion

2-Mercapto-N-2-naphthylacetamide (thionalide) loaded on glass beads with the aid of collodion is used for preconcentration of microgram levels of antimony(III) from aqueous solution. Antimony is quantitatively retained on the loaded beads from 0.4–0.8 mol l^?1 hydrochloric acid solutions; equilibration is achieved within 1 min. The retention capacity of the beads is 0.2 μml Sb g^?1 at 0.6 mol l^?1 hydrochloric acid. The maximum flow rate for quantitative retention is 1.27 ml min^?1 cm^?2. Antimony retained on the column is completely eluted with 10 ml of 6.0 mol l^?1 hydrochloric acid at flow rates<1.9 ml min^?1 cm^?2.     

Coarse‐grained molecular dynamics simulations of protein–ligand binding

Coarse‐grained molecular dynamics (CGMD) simulations with the MARTINI force field were performed to reproduce the protein–ligand binding processes. We chose two protein–ligand systems, the levansucrase–sugar (glucose or sucrose), and LinB–1,2‐dichloroethane systems, as target systems that differ in terms of the size and shape of the ligand‐binding pocket and the physicochemical properties of the pocket and the ligand. Spatial distributions of the Coarse‐grained (CG) ligand molecules revealed potential ligand‐binding sites on the protein surfaces other than the real ligand‐binding sites. The ligands bound most strongly to the real ligand‐binding sites. The binding and unbinding rate constants obtained from the CGMD simulation of the levansucrase–sucrose system were approximately 10 times greater than the experimental values; this is mainly due to faster diffusion of the CG ligand in the CG water model. We could obtain dissociation constants close to the experimental values for both systems. Analysis of the ligand fluxes demonstrated that the CG ligand molecules entered the ligand‐binding pockets through specific pathways. The ligands tended to move through grooves on the protein surface. Thus, the CGMD simulations produced reasonable results for the two different systems overall and are useful for studying the protein–ligand binding processes. © 2014 Wiley Periodicals, Inc.     

Neutron activation analysis of arsenic in rocks and sediments by direct evolution with chloride- and bromide-condensed phosphoric acid reagents

A simple method is presented for the determination of arsenic in rocks and in sediments by neutron activation. After irradiating a sample it is, without any other treatment, directly heated in condensed phosphoric acid containing sodium chloride or sodium bromide to evolve arsenic as arsenic(III) chloride or bromide. The distillate is absorbed in distilled water, in which arsenic is later precipitated in elementary form by adding hypophosphite to the solution. From arsenite, arsenic(III) oxide, arsenate and arsenic(III) sulphide, arsenic chloride can be evolved with NaCl-CPA reagent, but elementary arsenic and arsenic(V) oxide do not react with it. However, metallic arsenic is found to react with KIO₃-NaCl-CPA and arsenic(V) oxide with the NaBr-CPA, both both evolving arsenic(III) chloride or bromide. Therefore, successive distillations, the first with NaCl-CPA and the second with NaBr-CPA, give a satisfactory means of differential determination of arsenic(III) and arsenate as well as arsenic(V) oxide. For the elementary arsenic a problem still now remains. The chemical recovery of carrier goes well beyond 95%. Part of this work was performed at the Research Reactor Institute, Kyoto University.     

Ring transformation of 5-acylpyrimidines into 4-acylpyrazoles with hydrazine and phenylhydrazine in acidic medium

5-Benzoyl-4-methylpyrimidines 4a,b and 5-acetyl-4-phenylpyrimidines 5a,b reacted with hydrazines in alcoholic acidic medium to give respectively 4-acetyl-3-phenylpyrazoles 7, 9 and 10 and 4-benzoyl-3-methylpyrazoles 6, 8 and 11 . In the reaction with phenylhydrazine, 5-benzoyl-4-methyl-2-methylthiopyrimidine ( 4a ) led exclusively to 4-acetyl-1,3-diphenylpyrazole ( 10 ) as 5-acetyl4-phenyl-2-methylthiopyrimidine ( 5a ) led to 4-benzoyl-3-methyl-1-phenylpyrazole ( 11 ) via the initial formation of phenylhydrazones of pyrimidines 4a and 5a . However, 5-benzoyl-4-methyl-2-phenylpyrimidine ( 4b ) and 5-acetyl-2,4-diphenylpyrimidine ( 5b ) reacted with phenylhydrazine to afford, each of them, a mixture of two isomeric pyrazoles. The mechanism of these ring contraction reactions is discussed.     

Calculation of positron states in the BEDT-TFF based organic superconductors

Positron states in the BEDT-TTF based organic superconductors, namely -Cu(NCS)₂, -CuCN[N(CN)₂] and -Cu[N(CN)₂]Br salts, have been calculated using the superposedatom model and the numerical relaxation technique. For each salt positrons are distributed predominantly around the anion layers and have a little overlap with the TTF skeleton and the outer S atoms which are responsible for the conductivity.     

Scalable free energy calculation of proteins via multiscale essential sampling

A multiscale simulation method, "multiscale essential sampling (MSES)," is proposed for calculating free energy surface of proteins in a sizable dimensional space with good scalability. In MSES, the configurational sampling of a full-dimensional model is enhanced by coupling with the accelerated dynamics of the essential degrees of freedom. Applying the Hamiltonian exchange method to MSES can remove the biasing potential from the coupling term, deriving the free energy surface of the essential degrees of freedom. The form of the coupling term ensures good scalability in the Hamiltonian exchange. As a test application, the free energy surface of the folding process of a miniprotein, chignolin, was calculated in the continuum solvent model. Results agreed with the free energy surface derived from the multicanonical simulation. Significantly improved scalability with the MSES method was clearly shown in the free energy calculation of chignolin in explicit solvent, which was achieved without increasing the number of replicas in the Hamiltonian exchange.