The changing face of chemical derivatization in pharmaceutical and biomedical analysis

The present and past use of chemical derivatization reactions is overviewed with emphasis on the present role of derivatization in chromatographic and electrophoretic methods with special respect to fluorogenic derivatization to increase the selectivity and sensitivity, chiral derivatization to transform enantiomeric pairs to easily separable diastereomers, and GC/GC-MS derivatization. Non-chromatographic derivatization is also discussed with emphasis on UV-VIS spectrophotometry, fluorimetry, and immunoassay methods. The up-to-dateness of derivatization methods with negative examples mainly from the field of UV-VIS analysis are also discussed. Finally, examples are given on how the experiences obtained in the course of old studies can be used to solve current problems with the aid of chemical derivatization. Received: 19 January 1998 / Revised: 2 March 1998 / Accepted: 6 March 1998     

Ion Association and Hydration in Aqueous Solutions of Nickel(II) and Cobalt(II) Sulfate

Aqueous solutions of nickel(II) and cobalt(II) sulfate have been investigated at 25 gt;∘gt;C by dielectric relaxation spectroscopy (DRS) over a wide range of frequencies (0.2 ≤ ν (GHz) ≤ 89) and salt concentrations (0.025 ≤ gt;cgt;(mol-gt;Lgt;gt;−1gt;) ≤ 1.4). The spectra indicate, as for MgSOgt;4gt;(aq) studied previously, the simultaneous presence of double solvent-separated, solvent-shared and contact ion pairs in both NiSOgt;4gt;(aq) and CoSOgt;4gt;(aq). The stepwise formation constants for each ion-pair type and the overall association constant, obtained from the data are in good agreement with ultrasonic relaxation and other estimates. The DR spectra at higher concentrations (gt;cgt; ≥ 0.5 mol-Lgt;−1gt;) suggest the existence of a nonlinear triple ion Mgt;2gt;SOgt;4gt;gt;2+gt;(aq). Consistent with the very strong hydration of the salts, which have ‘effective’ hydration numbers approaching 27 at infinite dilution, there are no significant differences in any of the relaxation or thermodynamic parameters for NiSOgt;4gt;(aq) and CoSOgt;4gt;(aq), except that the triple ion appears to be somewhat more stable for the latter.     

Synthesis and proton conductivity studies of polystyrene‐based triazole functional polymer membranes

In this study, poly(vinylbenzylchloride) (PVBC) was produced by free‐radical polymerization of 4‐vinylbenzylchloride, and then it was functionalized with 3‐amino‐1,2,4‐triazole (ATri) and 1H‐1,2,4‐triazole (Tri). The composition of the polymers was verified by elemental analysis, and the structure was characterized by Fourier transform infrared and gt;13gt;C‐nuclear magnetic resonance spectra. PVBC was modified by ATri with 68% and Tri with 50% yield. The polymers were doped with trifluoromethanesulfonic acid (TA) at various molar ratios, gt;Xgt; = 0.5, 1, 2, and 3 with respect to aminotriazole and triazole units. Proton transfer from TA to the triazole rings was proved with Fourier transform infrared spectroscopy. Thermogravimetric analysis showed that the samples are thermally stable up to approximately 200 °C. Differential scanning calorimetry results illustrated the homogeneity of the materials. Under anhydrous conditions, PVBCATri3TA and PVBCTri3TA showed highest proton conductivity of 0.086 and 0.042 S/cm, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Theoretical investigations on the chemical bonding, electronic structure, and optical properties of the metal-organic framework MOF-5

The chemical bonding, electronic structure, and optical properties of metal-organic framework-5 (MOF-5) were systematically investigated using ab initio density functional calculations. The unit cell volume and atomic positions were optimized with the Perdew-Burke-Ernzerhof (PBE) functional leading to a good agreement between the experimental and the theoretical equilibrium structural parameters. The calculated bulk modulus indicates that MOF-5 is a soft material. The estimated band gap from a density of state (DOS) calculation for MOF-5 is about 3.4 eV, indicating a nonmetallic character. As MOFs are considered as potential materials for photocatalysts, active components in hybrid solar cells, and electroluminescence cells, the optical properties of this material were investigated. The detailed analysis of chemical bonding in MOF-5 reveals the nature of the Zn-O, O-C, H-C, and C-C bonds, that is, Zn-O having mainly ionic interaction whereas O-C, H-C, and C-C exhibit mainly covalent interactions. The findings in this paper may contribute to a comprehensive understanding about this kind of material and shed insight into the synthesis and application of novel and stable MOFs.     

Investigation of DNA cleavage activities of new oxime-type ligand complexes and molecular modeling of complex-DNA interactions

Nucleolytic activities of some new oxime-type ligand complexes were investigated by neutral agarose gel electrophoresis. Analysis of the cleavage products in agarose gel indicated that all complexes used converted supercoiled pUC18 plasmid DNA to its nicked or linear form. It was found that nucleolytic activities of the complexes depend on the complex concentration, reaction time and the presence of a cooxidant (magnesium monoperoxyphthalate, MMPP) in the reaction mixture. However, the complexes cleaved pUC18 plasmid DNA at all investigated pH values. Nucleolytic activities of complexes were investigated for different complex concentrations (0.1–100 μmol Lgt;−1gt;), pH values (6.0–10.0) and reaction times (0–60 min). Molecular modeling studies performed by the Hyperchem Software together with DNA-binding studies showed that planar sites of the complexes intercalated into double stranded DNA. It can be concluded that all oxime-type ligand complexes used can be evaluated as nuclease mimics.     

Syntheses,structures and magnetic properties of Mn(II) containing 3D polymeric networks

Two novel 3D coordination polymers {[Mn(aip)(DMF)]}gt;gt;ngt;gt;, CPO-9, and {[Mngt;3gt;(Hatp)gt;2gt;(atp)gt;2gt;](Hgt;2gt;O)gt;2gt;(DEF)gt;4gt;}gt;gt;ngt;gt; CPO-10 (aip = 5-aminoisophthalate, atp = 2-aminoterephthalate, DMF = dimethylformamide, DEF = diethylformamide) have been synthesized by solvothermal methods. Their properties have been studied by single-crystal X-ray diffraction, thermogravimetric analysis, high-temperature powder X-ray diffraction and magnetic susceptibility measurements. The crystal structure of CPO-9 is based on infinite chains of carboxylato-bridged five-coordinated Mn(II) ions that are crosslinked via the aip ligands to form a 3D structure. CPO-10 is based on linear trinuclear building units of carboxylato-bridged octahedral Mn(II) ions that are crosslinked by the atp ligands into a 3D structure. Both compounds have 1D channels that contain solvent molecules. The solvent accessible void volume for CPO-10 is 51.9% of the unit cell volume. For both compounds, however, the solvent molecules cannot be removed without the collapse of the structures into amorphous phases at 250 °C. The magnetic susceptibility measurements indicate antiferromagnetic couplings between the Mn(II) ions in both compounds. The magnetic data have been fitted using theoretical approaches.     

New designs for inhibitors of the NF-κB: DNA binding

We present a series of new inhibitors of the association between nuclear factor kappa B (NF-gt;g src="/content/n2g3400572220587/xxlarge954.gif" alt="kappa" align="BASELINE" BORDER="0">gt;B) and the corresponding gt;g src="/content/n2g3400572220587/xxlarge954.gif" alt="kappa" align="BASELINE" BORDER="0">gt;B site in DNA. They were designed using the lead compound 15-deoxy-g src="/content/n2g3400572220587/xxlarge916.gif" alt="Delta" align="BASELINE" BORDER="0">gt;12,14gt; -prostaglandin Jgt;2gt; (PGJ2), which is a natural product with demonstrated inhibitory efficiency for this system. First, the binding mode of PGJ2 to NF-gt;g src="/content/n2g3400572220587/xxlarge954.gif" alt="kappa" align="BASELINE" BORDER="0">gt;B was unraveled by GOLD docking calculation. Subsequently, substitutions were made to PGJ2 to optimize its association with NF-gt;g src="/content/n2g3400572220587/xxlarge954.gif" alt="kappa" align="BASELINE" BORDER="0">gt;B. Care was taken not to strongly increase the reactivity of the new compounds, and to keep the overall shape, size and hydrophilicity of the lead compound, which should render them a similar bioavailability. Molecular mechanics calculations were performed to decide on the suitability of the substitutions, and to evaluate the energies of association with NF-gt;g src="/content/n2g3400572220587/xxlarge954.gif" alt="kappa" align="BASELINE" BORDER="0">gt;B. Density functional theory calculations were performed also to study the overall reactivity of the substituted drugs towards NF-gt;g src="/content/n2g3400572220587/xxlarge954.gif" alt="kappa" align="BASELINE" BORDER="0">gt;B. Important general conclusions were obtained, concerning the improvement of these natural inhibitors; namely, a set of rational methodologies were deduced to improve the association between the PGJ2 derivatives and NF-gt;g src="/content/n2g3400572220587/xxlarge954.gif" alt="kappa" align="BASELINE" BORDER="0">gt;B, and their efficiency demonstrated by generating a set of substituted complexes, some of them with a very much increased affinity for NF-gt;g src="/content/n2g3400572220587/xxlarge954.gif" alt="kappa" align="BASELINE" BORDER="0">gt;B, opening new doors to enlarge the therapeutic capabilities of this class of drugs.     

A new approach to 6-deoxy-D-allofuranose- and 6-deoxy-L-talofuranose derivatives from 1,2:5,6-di-O-isopropylidene α-D-glucofuranose

3-O-Acetyl-1,2-O-isopropylidene-g src="/content/p202x5k268606h31/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-gt;Dgt;-allofuranose (gt;2 bgt;) was prepared from 1,2:5,6-di-O-isopropylidene-g src="/content/p202x5k268606h31/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-gt;Dgt;-allofuranose (gt;1 bgt;). Treatment ofgt;2 bgt; with triphenylphosphine-diethyl azodicarboxylate afforded regio- and stereospecifically the 5,6-epoxy-g src="/content/p202x5k268606h31/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-gt;Dgt;-allo derivative (gt;3gt;). The other diastereomeric compound, 5,6-epoxy-1,2-O-isopropylidene-g src="/content/p202x5k268606h31/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-gt;Lgt;-talofuranose (gt;6gt;) was also prepared stereoselectively fromgt;2 bgt; gt;viagt; the intermediatesgt;5 agt; andgt;5 bgt;. The epoxy sugarsgt;3gt; andgt;6gt; were converted with lithium aluminum hydride to the corresponding 6-deoxy-1,2-O-isopropylidene-g src="/content/p202x5k268606h31/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-gt;Dgt;-allofuranose (gt;4 agt;) and -g src="/content/p202x5k268606h31/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-gt;Lgt;-talofuranose (gt;7 agt;) derivatives. Hydrolysis ofgt;4 agt; andgt;7 agt; afforded 6-deoxy-gt;Dgt;-allose and 6-deoxy-gt;Lgt;-talose, respectively. The corresponding 3,5-di-O-acetyl- (gt;4 bgt; andgt;7 bgt;) and the 3,5-O-(tetraisopropyldisiloxane-1,3-diyl) derivatives (gt;4 cgt; andgt;7 cgt;) are also described. Selective removal of the isopropylidene group and subsequent acetylation offers a convenient route to prepare sugar derivatives containing furanose ring, likegt;8 bgt;, as a suitable precursor for nucleoside analogs.Herrn Prof. Dr.gt;K. Komarekgt; mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Determination of Pt in urine of tram drivers by sector field inductively coupled plasma mass spectrometry

The Platinum Group Elements (PGEs) used in automotive catalytic converters are partly emitted into the air during use and can enter the human respiratory system. Due to the increasing use of automotive catalytic converters, the importance of this problem cannot be overlooked.The goal of this investigation was to determine the concentration of Pt in the urine of individuals occupationally exposed to urban air with heavy traffic. Sector field inductively coupled plasma mass spectrometry (SF–ICP–MS) was used for determination of Pt in the urine of tram drivers. 38 and 34 subjects were investigated in Vienna and Budapest, respectively. Samples were taken from the tram drivers both before and after the shift.The results for Pt were compared to those from a previous study performed by our team. The comparison showed that the concentration medians were 4 times higher than the previous ones. Moreover, the values in Budapest were about twice as high as those from Vienna. A partly significant change could be observed between the two sets of data: before, and after the shift.     

Analysis of steroids. XLI. Ion-pair high-performance liquid chromatographic separation of quaternary ammonium steroids on silica.

A normal-phase ion-pair chromatographic system has been developed for the high-performance liquid chromatographic investigation of pipecuronium bromide (2 beta,16 beta-bis-(N'-dimethyl-l-piperazinyl)-3 alpha,17 beta-diacetoxy-5 alpha-androstane dibromide) and related quaternary ammonium steroids. The use of silica as the stationary phase and a 96:4 mixture of acetonitrile and water containing 0.1 mol/dm3 sodium perchlorate as the eluent with detection at 213 nm enable the potential impurities as well as the hydrolytic and oxidative degradation products of pipecuronium bromide to be separated and detected down to the 0.01% level. The above system is also applicable to the high-performance liquid chromatographic investigation of other quaternary ammonium steroids (pancuronium bromide, vecuronium bromide).