Factors affecting relative stabilities and proton affinities of oxazolidinone and its N,C5-formyl derivatives

The proton affinities of all the potential sites of oxazolidinone (OXA) and formyl substituted OXA have been evaluated using ab initio and DFT methods. N4- and C5-formyl oxazolidinone isomers and their protonated structures have been analyzed for relative stabilities. The proton affinity (PA) of carbonyl oxygen of oxazolidinone is observed to be highest in un-substituted and formyl substituted OXA molecules. The PA values decrease for the potential sites in the range 0.5–15.51 kcal/mol as a result of the presence of the formyl substituent. Atomic charges and electron delocalization of neutral and protonated species have been analyzed with the application of NBO. The various factors such as variation in geometrical parameters, atomic charge redistribution, alterations in conjugative interactions, effect of formyl substituent, the presence of intramolecular hydrogen bonding and electronic effects have been explored to rationalize the relative stabilities and proton affinities of OXA and its N,C5 formyl derivatives.     

Optimization of a direct spectrophotometric method to investigate the kinetics and inhibition of sialidases

Backgrounds

Streptococcus pneumoniae expresses three distinct sialidases, NanA, NanB, and NanC, that are believed to be key virulence factors and thus, potential important drug targets. We previously reported that the three enzymes release different products from sialosides, but could share a common catalytic mechanism before the final step of product formation. However, the kinetic investigations of the three sialidases have not been systematically done thus far, due to the lack of an easy and steady measurement of sialidase reaction rate.

Results

In this work, we present further kinetic characterization of pneumococcal sialidases by using a direct spectrophotometric method with the chromogenic substrate p-nitrophenyl-N-acetylneuraminic acid (p-NP-Neu5Ac). Using our assay, the measured kinetic parameters of the three purified pneumococcal sialidase, NanA, NanB and NanC, were obtained and were in perfect agreement with the previously published data. The major advantage of this alternative method resides in the direct measurement of the released product, allowing to readily determine of initial reaction rates and record complete hydrolysis time courses.

Conclusion

We developed an accurate, fast and sensitive spectrophotometric method to investigate the kinetics of sialidase-catalyzed reactions. This fast, sensitive, inexpensive and accurate method could benefit the study of the kinetics and inhibition of sialidases in general.     

Chemodosimeter for CN(-)--interplay between experiment and theory

The reaction-based cost effective detection of CN(-) over the most competitive ions, F(-) and Ac(-), by a commercially available dye has been developed. The experimental results are in good agreement with the theory. An application in the form of 'dip-sticks' which provides an instant information, has been demonstrated.     

Development of a Stability-Indicating RP-LC Method for Determination of Betamethasone Dipropionate and Estimation of Its Related Compounds in a Dermatological Pharmaceutical Product

A new stability-indicating reversed-phase LC method has been developed and validated for the assay and identification of betamethasone dipropionate and its related compounds in a dermatological pharmaceutical drug product, namely Diprolene Ointment. Separation of all the peaks of interest was achieved on a Symmetry Shield RP18 (100 mm × 4.6 mm, 3.5 µm) column using a gradient elution at a flow rate of 1.5 mL min^?1 with mobile phase A (10 mM monobasic sodium phosphate at pH 2.5) and mobile phase B (acetonitrile) and UV detection at 250 nm. The limit of detection (LOD) and limit of quantitation (LOQ) of this method was 0.00004  and 0.0001 mg mL^?1, respectively. The method was successfully validated in accordance with ICH guidelines and was accurate, linear, precise, reproducible, specific, and robust. A simple, reproducible and accurate single step sample extraction procedure using tetrahydrofuran, water, and methanol (40:30:30, v/v/v) was developed to extract betamethasone dipropionate and its related compounds from the ointment. The sample extraction procedure and the LC conditions presented in this report can be used for routine analysis of Diprolene Ointment in quality control laboratories. This method may also be applied to other dermatological pharmaceutical drug products “as-is” or with minor modification.     

Photoluminescence and Thermoluminescence Investigation of Europium- and Dysprosium-Doped Dibarium Magnesium Silicate Phosphor

Europium- and dysprosium-doped barium magnesium silicate powder with different concentrations of dysprosium was synthesized using solid state reactions. The prepared phosphors were characterized using photoluminescence. Prominent green color emissions were obtained under ultraviolet excitation. The thermoluminescence glow curves of the samples were measured after various delay times. With increased delay time, the intensity of the thermoluminescence peak decays, and the position of the thermoluminescence peak shifts to higher temperatures, indicating the considerable retrapping associated with general order kinetics. Refined lattice parameters of monoclinic phosphor were calculated.     

High speed,long reach OFDM-FSO transmission link incorporating OSSB and OTSB schemes

Free Space Optics (FSO) link is extremely responsive to the diverse climate state of affairs that bound the FSO range. A demonstration of fading resistant FSO system using a simulated test-bed employing OFDM scheme is reported in this work to realize the prolonged FSO link with acceptable SNR and BER with the highest stream rate of 5 Gb ps under the impact of diverse weather conditions. Simulations point toward that the proposed hybrid OFDM-FSO transmission system incorporating OTSB- and OSSB-schemes promises significantly enhanced FSO link compared to conventional FSO systems.     

Inequalities for hadamard product and unitarily invariant norms of matrices

The paper contains some general theorems for Hadamard product of matrices which in particular include Fiedler's Theorem and a better bound for an inequality on product of eigenvalues of certain matrices due to Ando. Lieb's concavity Theorem has been proved using operator means. Some inequalities for unitarily invariant norms have also been proved.     

Optimal compromise solution of multi-objective minimal cost flow problems in fuzzy environment

Ghatee and Hashemi [M. Ghatee, S.M. Hashemi, Ranking function-based solutions of fully fuzzified minimal cost flow problem, Inform. Sci. 177 (2007) 4271–4294] transformed the fuzzy linear programming formulation of fully fuzzy minimal cost flow (FFMCF) problems into crisp linear programming formulation and used it to find the fuzzy optimal solution of balanced FFMCF problems. In this paper, it is pointed out that the method for transforming the fuzzy linear programming formulation into crisp linear programming formulation, used by Ghatee and Hashemi, is not appropriate and a new method is proposed to find the fuzzy optimal solution of multi-objective FFMCF problems. The proposed method can also be used to find the fuzzy optimal solution of single-objective FFMCF problems. To show the application of proposed method in real life problems an existing real life FFMCF problem is solved.     

Colorimetric recognition of Cu(II) by (2-dimethylaminoethyl)amino appended anthracene-9,10-diones in aqueous solutions: deprotonation of aryl amine NH responsible for colour changes

Chromogenic receptors 2 and 3 undergo distinct colour changes from magenta to blue on gradual addition of Cu(II) and can be used as colorimetric probes for spectrophotometric and visual analysis of Cu(II) in the presence of biological metal ions Na(I), K(I), Mg(II), Ca(II), Fe(II), Zn(II) etc. in aqueous solution (methanol-water 1 : 1 v/v). On addition of Cu(II), both 2 and 3 exhibit a bathochromic shift of Delta lambda(max) = 114 nm for 2 and Delta lambda(max)= 150 and 265 nm for receptor 3. The protonation constants and formation constants of Cu(II) complexes of receptors 2 and 3 (at pH 7) and the effect of pH on formation of these complexes has been determined by the combination of UV-vis-pH titrations of receptors 2 and 3 and their Cu(II) complexes. These results and the emergence of only one peak at 610 nm for 2 and two distinct absorption peaks at 715 and 800 nm for 3 on addition of Cu(II) unambiguously point to mono- and di-deprotonation for 2 and 3, respectively.     

Design and characterization of three-dimensional carbon nanotube foams

We demonstrate a new method that makes use of colloidal silica templates to fabricate porous three-dimensional architectures of carbon nanotubes (CNTs). CNTs were grown on monolayered and multilayered structures of colloidal silica using chemical vapor deposition. Porous CNT membranes and three-dimensional carbon nanotube foams were obtained by treating these silica-CNTs structures with HF. The membranes and foams of CNT so obtained were chemically and mechanically stable and were characterized by using scanning electron microscopy and energy dispersive spectroscopy.