Variation of U-microdistribution in fossil Hipparion teeth as a complicating factor in dating studies

Five Upper Miocene fossil Hipparion molars were studied for U-distribution by Fission Track. U uptake has reached the whole mass of the teeth and no saturation fronts seem to occur in the interior layers. Mean U-concentration in dentine, cement and enamel was 157, 139 and 78 ppm, respectively. U_enamel/U_dentine 0.5 is considerably higher than 0.1 reported in the past for Upper-Quaternary mammoth teeth. These features are disadvantageous for ESR-dating in Hipparion enamel, although a long-lived signal (g=2.0018) is apparent. Leaching phenomena occur in the outer regions of these teeth. Inner enamel folding seems to have hindered a more uniform U-distribution in the teeth.     

Copper(II) complexes of tetrapeptides containing cysteinyl and histidinyl residues

It is becoming increasingly apparent that the coordination chemistry of oligopeptides with Cys-X-Y-Cys and His-X-Y-Cys sequences (X, Y = variable amino acid residues) is an important theme in transition metal and bioinorganic chemistry(1,2). The Cys-X-Y-Cys sequence is often encountered in the metal binding site of several metalloproteins, such as iron–sulfur proteins, e.g. rubredoxins(3) and ferrodoxins(4), high potential iron–sulfur proteins(5), metallothioneins(6), zinc proteins(7) etc. The amino acid sequence His-X-Y-Cys is also of bioinorganic importance since it has been found in the active site of copper(8), iron–sulfur(9) and zinc(10) proteins. We are currently seeking to develop the area of transition metal/Cys-X-Y-Cys and His-X-Y-Cys peptide interactions(11,12); our goals are: (i) to elucidate the role of these sequences in the biological activity and mechanism of action of the above metallobiomolecules, and (ii) to find possible new and more effective agents for the elimination of heavy metals from the human organism or from contaminated waste waters. Here we report the preparation and preliminary characterization of copper(II) complexes of tetrapeptide ligands containing the Cys-X-Y-Cys and His-X-Y-Cys sequences. This revised version was published online in June 2006 with corrections to the Cover Date.     

Investigation for the determination of ultra trace amounts of Co2+ complexed with 1,10-phenanthroline by adsorptive voltammetry

Summary The spontaneous adsorption of the Co²⁺ complex with 1,10-phenanthroline on HMDE was utilized for the development of a voltammetric analytical method employing phase selective alternating current, with first harmonic AC₁ in phase, =0°, voltammetry. The dependence of the analytical voltammetric response on physical and chemical parameters in various supporting electrolytes was investigated in detail. Optimum conditions for Co²⁺ determination were established. The method is very sensitive and selective. The determination limit is 205 ng/l Co²⁺ (adsorption time, t_ads=20 min). The precision and accuracy were evaluated: 1.84 g/l Co²⁺, RSD=3.24%, RE=–0.54%; for 205 ng/l Co²⁺, RSD=4.85%, RE=–3.90%. The results showed good reproducibility and reliabiality. The method was applied to natural waters, wines, mussel tissue and aquatic algae certified reference material.     

A remark on the negative activation volume for defects in solids

The evolution of the aging process of glassy materials quenched from temperatures above their glass transition temperature T_g, when plotting the relaxed enthalpy versus the decrease in volume, leads to a slope comparable to the isothermal compressibility close to T_g. This empirical result was explained in an earlier publication (V. Katsika-Tsigourakou, G. E. Zardas J. Non-Cryst. Solids 356 (2010) 179–180) by means of a thermodynamical model. Here, we show that the same model enables the explanation of the rare cases of negative defect activation in solids.     

Pulsed-field gradient nuclear magnetic resonance study of transport properties of fluid catalytic cracking catalysts

Pulsed-field gradient nuclear magnetic resonance (PFG NMR) has been applied to study molecular diffusion in industrial fluid catalytic cracking (FCC) catalysts and in USY zeolite for a broad range of molecular displacements and temperatures. The results of this study have been used to elucidate the relevance of molecular transport on various displacements for the rate of molecular exchange between catalyst particles and their surroundings. It turned out that this rate, which may determine the overall rate and selectivity of FCC process, is primarily related to the diffusion mode associated with displacements larger than the size of zeolite crystals located in the particles but smaller than the size of the particles. This conclusion has been confirmed by comparative studies of the catalytic performance of different FCC catalysts.     

Fourier-transform infrared study of orientation in pure and plasticized poly(vinyl chloride)

Fourier-transform infrared spectroscopy has been used for the study of orientation of pure and plasticized PVC. The results show that orientation is independent of experimental conditions (temperature, strain rate, plasticizer) in the homogeneous deformation range. Such behavior is explained by the existence of a fringe micellar-type network with physical crosslinks. The network is partially destroyed during stretching. Furthermore, the orientation of the carbonyl group of the plasticizer is connected with PVC chain orientation.     

Solid-Phase Synthesis of a Biotin Derivative and its Application to the Development of Anti-Biotin Antibodies

A biotin derivative, namely biotin–aminocaproic acid–lysine (BAL), was synthesized with solid-phase chemistry, conjugated to a carrier-protein, and used for rabbit immunization. The aminocaproic acid–lysine “long-arm” was used in order to project the biotin-hapten above the carrier-protein surface. Lysine was selected due to its N^ε-amino group, through which BAL was conjugated to the carrier-protein. BAL was synthesized on a commercially available resin with the Fmoc-solid-phase strategy; this has simplified the experimental procedure, overcome the need for intermediate purification steps, and led to a final product of high purity, with high yield. The anti-BAL antibodies recognized free biotin, as shown with an in-house-developed ELISA, in which biotin conjugated to a synthetic “lysine–dendrimer” was used to coat the ELISA microwells. In immunocytology and Western-blot experiments, the anti-BAL antibodies led to similar results with those obtained with streptavidin. Synthetic derivatives of hapten molecules that can be easily prepared with solid-phase chemistry, such as BAL, may be used for the development of specific antibodies for the corresponding hapten.