Predicted energies and structures associated with the mixed calcium strontium fluorapatites

Atomic scale local density functional simulations and configurational averaging are used to predict the energies and lattice parameters associated with mixed calcium/strontium fluorapatites, Ca_xSr_10−x(PO₄)₆F₂. In particular, the partition of Sr²⁺ and Ca²⁺ ions between the 6h and 4f cation sites is established across the entire compositional range. Lattice parameters and lattice volume are also analyzed as a function of Ca²⁺ to Sr²⁺ concentration and their cation site distribution. The predicted internal energy of mixing between the end members is used to discuss the available experimental data.     

Gene Expression on DNA Biochips Patterned with Strand‐Displacement Lithography

Lithographic patterning of DNA molecules enables spatial organization of cell‐free genetic circuits under well‐controlled experimental conditions. Here, we present a biocompatible, DNA‐based resist termed “Bephore”, which is based on commercially available components and can be patterned by both photo‐ and electron‐beam lithography. The patterning mechanism is based on cleavage of a chemically modified DNA hairpin by ultraviolet light or electrons, and a subsequent strand‐displacement reaction. All steps are performed in aqueous solution and do not require chemical development of the resist, which makes the lithographic process robust and biocompatible. Bephore is well suited for multistep lithographic processes, enabling the immobilization of different types of DNA molecules with micrometer precision. As an application, we demonstrate compartmentalized, on‐chip gene expression from three sequentially immobilized DNA templates, leading to three spatially resolved protein‐expression gradients.     

A multiperipheral model with continued cross channel unitarity

We derive, by using a spectral representation in momentum transfer, t, an integral equation, similar in structure to a multipheral equation, with continued cross channel unitarity, for the absorptive part for a composite particle scattering amplitude from a Bethe-Salpeter equation describing composite particle scattering in the s channel. At high energy in the t channel, the equation becomes homogeneous and has a Reggeized solution. We indicate how this equation may be solved using determinental techniques. We also show how the composite particle amplitude resulting from the original equation may be used to construct production and three body amplitudes. We also infer the possibility of studying, using the amplitude from the cross channel problem, the effect of extra unitarity on Reggeon-Reggeon-particle vertices.     

Study of molecular deformation mechanisms in the glassy state. I. Temperature effect on stress-birefringence and strain-birefringence responses of poly(methyl methacrylate)

In order to gain better understanding of the molecular deformation processes occurring in poly-(methyl methacrylate), a series of studies was carried out in uniaxial tension on the simultaneous stress and birefringence response in both constant-strain-rate and stress relaxation experiments. The former covered the temperature range ?120 to 75°C and the latter 0 to 90°C. Three deformation mechanisms, i.e., (i) change in intermolecular distance, (ii) distortion of the conformation of the COOCH₃ group from its thermal equilibrium state, and (iii) orientation of main-chain segments, are invoked to interpret the experimental results. It is concluded that, in the temperature range from ?120 to 75°C and possibly at higher temperatures as well, the polymer chains deform in the small-strain region by an orientation of those chain segments having lower potential-energy barriers to conformational changes and straining those chain segments having higher potential-energy barriers. Subsequent chain orientation of the already strained segments occur in the higher strain regions. Changes in intermolecular distances occur over the entire temperature range from ?120 to 90°C, but their magnitude decreases gradually as the temperature increases from ?40 to 40°C and then decreases sharply for temperatures above 40°C. Strain-induced distortion of the conformation of the COOCH₃ group may involve only rotation of the OCH₃ group around the C? O bond rather than rotation of the entire ester group itself.     

Total Syntheses of Casuarine and Its 6‐O‐α‐Glucoside: Complementary Inhibition towards Glycoside Hydrolases of the GH31 and GH37 Families

Selective glucosylation : Total synthesis of naturally occurring casuarine ( 1 ) and the first total synthesis of casuarine 6‐O‐α‐glucoside ( 2 ) were achieved through complete stereoselective nitrone cycloaddition, Tamao–Fleming oxidation and selective α‐glucosylation as key steps. Biological assays of the two compounds proved their strong and selective inhibitory properties towards glucoamylase NtMGAM and trehalase Tre37A, respectively, which place them among the most powerful inhibitors of these enzymes.

     

Detection and quantification of sucrose as dietary biomarker using gas chromatography and liquid chromatography with mass spectrometry

Several epidemiological studies suggest a link between the intake of refined sugars and an increased risk for colorectal, breast, pancreatic and endometrial cancer. However, other studies failed to confirm these conclusions and the reason for this may be the ambiguity of dietary assessment methods - mainly self-reporting - employed. Sucrose is an established biomarker for sugars intake, allowing the objective assessment of dietary sucrose. So far, urinary excretion of sucrose was mainly determined using an enzyme assay. However, this method is time-consuming and labour-intensive. In this study, we present a mass spectrometric method for the determination of sucrose in urine using liquid chromatography with mass spectrometry (LC/MS) which can be used for large-scale epidemiological studies.     

Amino acid rejection behaviour as a function of concentration

The solute rejection versus concentration behaviour of five different amino acids has been investigated using a Nitto Denko NTR7450 nanofiltration membrane. The experimental data for amino acid rejection was also compared against a combined steric and charge rejection model. At its isoelectric point, lysine was effectively neutral and its behaviour was well described by the model incorporating a steric function only. For phenylalanine, the combined model was found to fit the data well. In contrast there was poor agreement between the model and rejection data for glutamine, glutamic acid and glycine whose rejection values at first increased with concentration. This result implied that another governing process was in operation. Dimerisation as an explanation for the observed phenomena was also investigated. Size analysis of amino acid molecules as a function of the prevailing concentration using dynamic light scattering was limited but showed no evidence of dimerisation. This data was supported by osmotic pressure measurements which demonstrated no evidence of non-linearity in the relation between osmotic pressure and concentration.     

Analytical performance of the AtheNA MultiLyte® ANA II assay in sera from lupus patients with multiple positive ANAs

The purpose of this study was to evaluate the precision and accuracy of a commercial multiplexed kit for the measurement of 9 anti-nuclear antibodies (ANAs; anti-SS/A, anti-SS/B, anti-Sm, anti-RNP, anti-Jo-1, anti-Scl-70, anti-dsDNA, anti-Centromere B, and anti-Histone), and to compare these results to a subset of ANAs measured by enzyme-linked immunosorbent assays (ELISA) and immunodiffusion (ID). Sera were obtained from 22 systemic lupus erythematosus (SLE) patients, twelve controls and five others (commercial source) with various autoimmune diseases. ANA results from the AtheNA MultiLyte ANA II Assay (AtheNA) were compared to ELISA results (controls) and patients (ID). The AtheNA interassay coefficients of variation (CVs, N = 39, performed in duplicate; replicated 3x) ranged from 6.2% to 16.7% (mean = 9.8%), while the intra-assay CVs ranged from 5.8% to 14.3% (mean = 10.8%). Compared to results for SLE cases and controls, the sensitivity of AtheNA ranged from 85.7% to 100% (mean = 97.1%), while diagnostic specificity ranged from 16.7% to 100% (mean = 71.6%). There was significant agreement (P values ranging from 0.0001 to 0.03) when analytes coanalyzed by AtheNA and ELISA/ID were evaluated using Cohen's kappa (kappa values ranging from 0.376 to 1.000). No false positive ANA results were observed for either the control or commercial source autoimmune disease sera. These results indicate that the AtheNA assay is a precise and accurate alternative for performing multiple ELISAs or IDs in the diagnosis of autoimmune diseases, especially when the number of sera to be tested is large, such as in clinical screening or epidemiologic studies. It also appears that the AtheNA assay identifies positive ANA specificities which are missed by ID techniques, suggesting that it may have greater analytical sensitivity for some ANAs.     

2,2,3,4,4-pentamethylphosphetanic acid,C8H16PO2H: salts,complexes and a hydrogen bonded amine adduct

The conjugate base of the title acid, i.e. C₈H₁₆PO₂^?, has been investigated as its simple salts, as a ligand in transition metal complexes of cobalt and ruthenium, and as a secondary amonium salt in which hydrogen bonding between anion and cation occurs.     

Encapsulation of Tetraazaannulenato Compounds in Matrix by Sol-Gel Process

The hybrid organic-inorganic catalyst constituted by {5,7,12,14-tetramethyldibenzo[b,i]-1,4,8,11-tetraaza[14]annulenato} nickel (II), NiTMTAA, encapsulated in an alumina matrix has been prepared. NiTMTAA was synthesized by the reaction of nickel acetate with o-phenylenediamine in the presence of 2,4-pentanedione under argon atmosphere. The alumina hybrid material was obtained by a non hydrolytic sol-gel route, through the condensation of aluminum chloride with diisopropylether in the presence of NiTMTAA. The material has been prepared through precipitation from a gel. Characterization of the alumina hybrid material has been performed by ultra violet-visible spectroscopy, electron spectroscopic imaging, surface area, atomic absorption, infrared spectroscopy, and thermogravimetric analysis. The ultra violet-visible absorption spectrum of the hybrid material has bands characteristic of the NiTMTAA compound showing that the structure of NiTMTAA has been preserved in the hybrid material. The new material has a surface area of 300 m²/g. The electron image was that of a non-crystalline microstructure. Comparison between the leaching of NiTMTAA from NiTMTAA adsorbed on commercial neutral alumina confirm that in the non-hydrolytic materials the NiTMTAA is entrapped and not only adsorbed on the alumina surface. The use of conventional hydrolytic sol-gel process leads to the complete leaching of NiTMTAA from matrix, underlining the importance of the non-hydrolytic alumina gel process in the matrix preparation. The new catalysts prepared were tested for their ability to catalyze the epoxidation of (Z)-cyclooctene using iodosylbenzene as oxygen donor, giving moderate yields in the epoxidation (40%), while the homogeneous NiTMTAA is inactive due to NiTMTAA bleaching. These results emphasize the effect of the non-hydrolytic alumina matrix to prevent chemical degradation of NiTMTAA.