Spectrophotometric determination of some drugs for osteoporosis

Three simple, accurate and sensitive spectrophotometric methods are developed for the determination of some new drugs for the treatment of osteoporosis: risedronate sodium (I), alendronate sodium (II) and etidronate disodium (III). The first method is based on the measurement of difference in absorbance (Delta A) of risedronate sodium in 0.01 mol l(-1) hydrochloric and 0.1 mol l(-1) sodium hydroxide at 262 nm. Beer's law is obeyed over a concentration range of 15-150 microg ml(-1) with mean recovery 99.75+/-1.22 and molar absorptivity (epsilon) 1.891 x 10(3). The second method is based on the reaction of the primary amino group of (II) with ninhydrin reagent in methanolic medium in the presence of 0.05 mol l(-1) sodium bicarbonate. The colored product is measured at 568 nm, and the linearity range is found to be 3.75-45 microg ml(-1) with mean recovery 99.77+/-0.73 and epsilon 9.425 x 10(3). The third method is based on oxidation of the three mentioned drugs with ceric (IV) sulphate in 0.5 mol l(-1) sulphuric acid at room temperature and subsequent measurement of the excess unreacted cerium (IV) sulphate at 320 nm. The method obeyed Beer's law over a concentration range of 2-24 microg ml(-1) for the three drugs with mean recovery 99.79+/-1.16, 99.73+/-1.38 and 99.86+/-1.13 and epsilon 14.427 x 10(3), 13.813 x 10(3) and 14.000 x 10(3) for drugs I, II, III respectively. The proposed methods were successfully applied for the determination of the studied drugs in bulk powder and in pharmaceutical formulations. The results were found to agree statistically with those obtained the reported methods. Furthermore, the methods were validated according to USP regulations and also assessed by applying the standard addition technique.     

Dapson in Heterocyclic Chemistry,Part III: Synthesis,Antimicrobial, and Antitumor Activities of Some New Bisheterocyclic Compounds Containing Biologically Active Diphenylsulfone Moiety

The key intermediate diisothiocyanate 2 was allowed to react with 5-amino-3-methyl-pyrazole-4-carbonitrile 3, ethyl 5-amino-1-phenyl-pyrazole-4-carboxylate 6, 2-amino-tetrahydrobenzo[b]thiophene-3-car-bonitrile 9, ethyl-2-amino-tetra-hydrobenzo[b]thiophene-3-carboxylate 12, and/or 1,2,4-triazole 15 to give the corresponding biscompounds 4, 5, 7, 8, 10, 11, 13, 14, and 16, respectively. The structure of the synthesized compounds was elucidated by elemental analyses and spectral data. Some of the prepared compounds were tested for their antimicrobial and antitumor activities.     

Luciferin‐Regenerating Enzyme Mediates Firefly Luciferase Activation Through Direct Effects of D‐Cysteine on Luciferase Structure and Activity

Luciferin‐regenerating enzyme (LRE) contributes to in vitro recycling of D‐luciferin. In this study, reinvestigation of the luciferase‐based LRE assay is reported. Here, using quick change site‐directed mutagenesis seven T‐LRE (Lampyris turkestanicusLRE) mutants were constructed and the most functional mutant of T‐LRE (T⁶⁹R) was selected for this research and the effects of D‐ and L‐cysteine on T⁶⁹R T‐LRE‐luciferase‐coupled assay are examined. Our results demonstrate that bioluminescent signal of T⁶⁹R T‐LRE‐luciferase‐coupled assay increases and then reach equilibrium state in the presence of 5 mm D‐cysteine. In addition, results reveal that 5 mm D‐ and L‐cysteine in the absence of T⁶⁹R T‐LRE cause a significant increase in bioluminescence intensity of luciferase over a long time as well as decrease in decay rate. Based on activity measurements, far‐UV CD analysis, ANS fluorescence and DLS (Dynamic light scattering) results, D‐cysteine increases the activity of luciferase due to weak redox potential, antiaggregatory effects, induction of changes in conformational structure and kinetics properties. In conclusion, in spite of previous reports on the effect of LRE on luciferase bioluminescent intensity, the majority of increase in luciferase light output and time‐course originate from the direct effects of D‐cysteine on structure and activity of firefly luciferase.     

Interaction of biological buffers with electrolytes: Densities of aqueous solutions of two substituted aminosulfonic acids and ionic salts from T = (298.15 to 328.15) K

Biological buffers are of utmost importance for research in biological and clinical chemistry and in oceanography, but they may not be inert enough, thus interfering with the system under study. The N-[Tris(hydroxymethyl)methyl]-3-aminopropanesulfonic acid (TAPS) and N-[Tris(hydroxymethyl)methyl]-3-amino-2-hydroxypropanesulfonic acid (TAPSO) are useful zwitterionic buffers for pH control as standard buffers in the physiological region of pH 7.7 to 9.1 for TAPS and 7.0 to 8.2 for TAPSO, respectively. In this work, interaction between these zwitterionic compounds and electrolytes of potassium acetate (KAc), potassium bromide (KBr), potassium chloride (KCl), and sodium chloride (NaCl) were investigated through measuring the densities of these buffers in aqueous and in aqueous electrolyte solutions by a high precision vibrating tube digital densitometer from T = (298.15 to 328.15) K under atmospheric pressure. In this series of measurements, the aqueous samples were prepared with various concentrations of the zwitterionic buffers, up to saturated conditions, and over salt concentrations from (1 to 4) mol · dm^?3. The measured densities served to evaluate the cubic expansion coefficients, α(m, T) and the apparent molar volumes, V_?(m, T). An empirical equation was used to correlate quantitatively the experimental densities over the entire concentration ranges.     

Irciformonins E – K,C22‐Trinorsesterterpenoids from the Sponge Ircinia formosana

Chemical investigation of the sponge Ircinia formosana resulted in the isolation of seven new linear C₂₂‐sesterterpenoids, irciformonins E–K ( 1 – 7 ) in addition to irciformonin A ( 8 ), a previously isolated furanosesterterpenoid (=a furan‐moiety‐containing sesterterpenoid) from the same species. The structures were determined by interpretation of HR‐ESI‐MS and 2D‐NMR spectra. The structure of irciformonin A ( 8 ) was revised. Compound 5 exhibited significant inhibition of peripheral blood mononuclear cell proliferation induced by phytohemaglutinin.     

Synthesis and structure of the unsymmetrical β-diimine precursor: The β-iminoamine

The reaction of benzoylacetone with ortho-substituted aniline derivatives gives the unsymmetrical β-iminoamine ligands (5–8) with high yields. A convenient synthesis is described. These compounds have been characterized by NMR and IR spectroscopies. The structure of the β-iminoamine 5, 3-N-(2,6-diisopropylphenylamino)-1-phenyl-1N-(2,6-diisopropylphenylimino)but-2-ene, was solved by X-ray diffraction methods.     

Bounds for increasing multi-state consecutive k-out-of-r-from-n: F system with equal components probabilities

The consecutive k-out-of-r-from-n: F system was generalized to multi-state case. This system consists of n linearly ordered components which are at state below j if and only if at least k_j components out of any r consecutive are in state below j. In this paper we suggest bounds of increasing multi-state consecutive-k-out-of-r-from-n: F system (k₁ ? k₂ ? ? ? k_M) by applying second order Boole–Bonferroni bounds and applying Hunter–Worsley upper bound. Also numerical results are given. The programs in V.B.6 of the algorithms are available upon request from the authors.     

About the singularities and bifurcations of double indices recursion sequences

This paper reports analytical and numerical investigations about the singularities and bifurcations of a new class of discrete dynamical systems defined generally by the following 2-D discrete systems: y _m+1,n+1=f(y _m,n ,y _m+1,n ,y _m,n+1); we consider particularly the case y_m+1,n+1 = f(y_m,n, y_m+1,n)y_{m+1,n+1} = f(y_{m,n}, y_{m+1,n}).     

Modelling the Flow of Yield-Stress Fluids in Porous Media

Yield-stress is a problematic and controversial non-Newtonian flow phenomenon. In this article, we investigate the flow of yield-stress substances through porous media within the framework of pore-scale network modelling. We also investigate the validity of the Minimum Threshold Path (MTP) algorithms to predict the pressure yield point of a network depicting random or regular porous media. Percolation theory as a basis for predicting the yield point of a network is briefly presented and assessed. In the course of this study, a yield-stress flow simulation model alongside several numerical algorithms related to yield-stress in porous media were developed, implemented and assessed. The general conclusion is that modelling the flow of yield-stress fluids in porous media is too difficult and problematic. More fundamental modelling strategies are required to tackle this problem in the future.