Kinetics and mechanism of degradation of Co(II)–<Emphasis Type="Italic">N</Emphasis>-benzyloxycarbonylglycinato complex

The kinetics of multi-step thermal degradation of Co(II) complex with N-benzyloxycarbonyl glycinato ligand [Co(N-Boc-gly)₂(H₂O)₄]·2H₂O, in non-isothermal conditions was studied using isoconversional and non-isoconversional methods. The degradation of complex occurs in three well-separated steps involving the loss of water molecules in first step followed by two degradation steps of dehydrated complex. The dependence of Arrhenius parameters on conversion degree showed that all observed steps of thermal degradation are very complex, involving more than one elementary step, as can be expected for most solid-state heterogeneous reactions with solid reactants and solid and gaseous products. It was shown that step 1, corresponding to the dehydration, involves a series of competitive dehydration steps of differently bound water molecules complicated by diffusion. Second step involves two parallel reactions related to the loss of two identical C₆H₅CH₂O– ligand fragments complicated by the presence of products in gaseous state. Further degradation in step 3 corresponds to complex process with a change in the limiting stage, in this case from the kinetic to the diffusion regime, connected with the presence of gaseous products diffusing through the solid product.     

Design, Synthesis, and Testing of Polyamine Vectored Iron Chelators

Iron chelators have been shown to control the growth of cancer cells in culture by sequestering exogenous iron in the media. Thus, the ligands prevent cellular access to the metal. However, because transferrin provides iron to tumor cells in animals, chelators have not been effective antitumor agents. Polyamine chelator conjugates in which the polyamine vectored ligands into cells were far more active than the free chelators themselves. However, the free ligands were not released from the vector once in the cell. The current study focuses on the synthesis and preliminary evaluation of a polyamine chelator conjugate capable of releasing the free ligand intracellularly via a nonspecific esterase.     

Data dissemination in autonomic wireless sensor networks

In this paper, a new data dissemination algorithm for wireless sensor networks is presented. The key idea of the proposed solution is to combine concepts presented in trajectory-based forwarding with the information provided by the energy map of the network to determine routes in a dynamic fashion, according to the energy level of the sensor nodes. This is an important feature of an autonomic system, which must have the capacity of adapting its behavior according to its available resources. Simulation results revealed that the energy spent with the data dissemination activity can be concentrated on nodes with high-energy reserves, whereas low-energy nodes can use their energy only to perform sensing activity or to receive information addressed to them. In this manner, partitions of the network due to nodes that ran out of energy can be significantly delayed and the network lifetime extended.     

Electrochemical behavior of 5-substituted 2-alkylidene-4-oxothiazolidine derivatives studied by cyclic voltammetry

This study demonstrates the electrochemical activity of selected 2-alkylidene-4-oxothiazolidine compounds containing different substituents at the C5-position on the Pt-electrode in 0.1 M TBAHFP + MeCN in the potential range from −2 V to 2 V. The mechanism of electrode processes is discussed. It is shown that a chemical step is involved in irreversible electrochemical processes. The effect of the substituent at the C5-position on reduction and oxidation potentials is also noted. The regions of a linear dependence of the current peak on the concentration of the compounds examined are determined. The text was submitted by the authors in English.     

A standard protocol for single nucleotide primer extension in the human genome using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Analysis of single nucleotide polymorphisms (SNPs) has become an increasingly important area of research, with numerous applications in medical genetics, population genetics, forensic science, and agricultural biotechnology. Large-scale SNP analyses require the development of methodologies that are economical, flexible, accurate and capable of automation. Primer extension in conjunction with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) is currently emerging as a potential method for high-throughput SNP genotyping. We have evaluated a number of published primer extension methods and refined a simple and robust protocol to analyze human autosomal disease-causing mutations and population genetic markers on the Y-chromosome. Twelve different variant sites were examined, and homozygotes, heterozygotes and hemizygotes were accurately typed. A 100% concordance was observed between SNP genotypes obtained using the MALDI-TOFMS technique and alternative genotyping methods, such as restriction fragment length polymorphism (RFLP) assays and denaturing high-performance liquid chromatography (DHPLC). Since multiple polymorphisms can be detected in single reactions, the method provides a cost-effective approach for SNP analysis. The protocol is also extremely flexible (able to accommodate new markers) and can be adapted to a number of platforms without the use of commercial kits.     

Two-dimensional gel protein database of Saccharomyces cerevisiae (update 1999).

By proving the opportunity to visualize several hundred proteins at a time, two-dimensional (2-D) gel electrophoresis is an important tool for proteome research. In order to take advantage of the full potential of this technique for yeast studies, we have undertaken a systematic identification of yeast proteins resolved by this technique. We report here the identification of 92 novel protein spots on the yeast 2-D protein map. These identifications extend the number of protein spots identified on our yeast reference map to 401. These spots correspond to the products of 279 different genes. They have been essentially identified by three methods: gene overexpression, amino acid composition and mass spectrometry. These data can be accessed on the Yeast Protein Map server (htpp://www.ibgc.u-bordeaux2.fr/YPM).     

Kinetic and Thermodynamic Studies of Facial and Meridional uns-cis-[Co(eddp)gly] Complexes

Thermal properties of facial and meridional uns-cis-[Co(eddp)gly]0.5H₂O complexes were investigated by means of DSC and TG techniques. It wasshown that the processes of thermal decomposition of these complexes are multi-stepdegradation processes, which can also be well separated into individual steps, depending onthe molecular symmetry. Thus, the process of thermal degradation of the meridional isomerof the above complex consists of 4 well-separated steps in the temperature interval from 100to 500°C. The corresponding kinetic and thermodynamic parameters of this process weredetermined, and a possible mechanism is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structural transformation of push-pull 5-substituted-4-oxothiazolidines during heating

The thermal stability of push-pull 5-substituted-4-oxothiazolidines was studied by DSC, IC and X-ray diffraction techniques. It was shown that the compounds are stable in the temperature range from room temperature to melting point. The melting is combined with breaking crystal structure and forming glass material as a new phase that forms crystals by cooling it very slowly. The rate constant, activation energy as well as activation parameters of process were determined.