Differentiation of Regioisomeric Esters of Sucrose by Ionspray Tandem Mass Spectrometry

Abstract

Structural characterization and differentiation of distinct regioisomenc esters of sucrose were obtained using lonspray ionization and low energy tandem mass spectrometry. Low energy CAD MS/MS analyses of the protonated molecules [M + H]⁺ provided characteristic fingerprint patterns, and permitted differentiation of the various regioisomers. MS/MS analyses of selected intermediate fragment ions formed during the ionization process provided additional structural data, and established the fragmentation routes of their [M + H]⁺ precursors.     

Synthesis and In-vitro drug release of insulin-loaded poly(n-butyl cyanoacrylate) nanoparticles

Nanoparticles have been prepared by dispersion polymerisation of n-butyl cyanoacrylate in acidified water, with and without the inclusion of insulin. The molecular weight of the polymerising material increases by a stepwise process, in which chains are initiated, terminated, and reinitiated, until an equilibrium molecular weight is reached. This equilibrium molecular weight is higher at lower dispersion pH. The reaction is complete within two hours. Insulin is capable of initiating polymerisation, but if introduced after all of the monomer has been incorporated into the growing nanoparticles it has no effect on polymer molecular weight. A drug loading of 72% was achieved in particles produced at 25 °C and pH 3.0, with insulin introduced one hour after monomer initiation. Particle degradation characteristics were assessed using solutions of esterase in phosphate buffered saline at pH 7.0, with butanol release monitored as a measure of polymer degradation. Insulin release was monitored under the same conditions. Both butanol production and insulin release showed a similar biphasic mechanism, indicating that the drug release rate is determined by polymer degradation characteristics. An initial burst release of both materials is associated with the degradation of surface species, and this is then followed by a steady-state release from sub-surface material.

Insulin release as a function of time at an esterase concentration of 2.0 mg · ml⁻¹.     

Protection and Labelling of Thymidine by a Fluorescent Photolabile Group

A fluorescent photolabile group including coumarin and MeNPOC moieties was synthesized to protect 5′‐OH terminal function of thymidine (T). Its photochemical and photophysical properties were studied, in particular the photocleavage (photodeprotection under a 365‐nm irradiation) is only lowered by a factor of two by addition of the fluorophore. Fluorescence properties of the coumarin probe are not changed upon irradiation, which is satisfactory for the application required, i.e., in situ synthesis of DNA microarrays.     

The Structure of Hydrotris(imidazolyl)boratothallium(I) – the First Structurally Authenticated Tris(imidazolyl)borate Metal Complex

The title compound crystallizes in the monoclinic space group P2₁/n with a = 8.706(1), b = 9.192(1), c = 15.261(2) Å, β = 94.740(3)°, V = 1217.0(3) ų, Z = 4, D_calc = 2.278 g cm^–3. The tris(imidazolyl)borate ligand bridges between three thallium atoms. The structure consists of one‐dimensional twisted ladder‐like strands.     

Evaluation of Sample Preparation Methods for Non-Target Screening of Organic Micropollutants in Urban Waters Using High-Resolution Mass Spectrometry

Non-target screening (NTS) has gained interest in recent years for environmental monitoring purposes because it enables the analysis of a large number of pollutants without predefined lists of molecules. However, sample preparation methods are diverse, and few have been systematically compared in terms of the amount and relevance of the information obtained by subsequent NTS analysis. The goal of this work was to compare a large number of sample extraction methods for the unknown screening of urban waters. Various phases were tested for the solid-phase extraction of micropollutants from these waters. The evaluation of the different phases was assessed by statistical analysis based on the number of detected molecules, their range, and physicochemical properties (molecular weight, standard recoveries, polarity, and optical properties). Though each cartridge provided its own advantages, a multilayer cartridge combining several phases gathered more information in one single extraction by benefiting from the specificity of each one of its layers.     

A fluid mechanical model for granular flow in silos

Granular materials may display both solid and fluid like behaviour. For low densities and high strain rates as in avalanches or during the discharge of silos the behaviour is mainly governed by interparticle collisions. On the other hand, frictional contacts characterise the solid state which is represented within the framework of plasticity theory. A fluid like constitutive model describes granular materials when subjected to large deformations and high strain rates. It bases upon a modified viscoplastic model that is valid for both yielded and unyielded regions. The central idea is the distinction between fluid and solid regions by means of comparing actual shear stress and Coulomb yield stress. The application to the simultion of the discharge of silos shows the feasibility of the chosen method. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Barium antimonide oxide,Ba3Sb2O

The antimonide oxide Ba₃Sb₂O consists of discrete [Sb₂]^4? and O^2? anions, and crystallizes with a new structure type. The Sb—Sb distances are comparable to those known from electron‐precise zintl phases and the tetrahedral coordination of the O^2? anion is also observed in some other Ba‐rich metallide oxides.