Solid composite electrodes for DNA enrichment and detection.

New plastic composite electrodes with appliance in medical diagnostic are described. The new electrode material offers the possibility of specific electrical enrichment and electrochemical analysis of nucleic acid sequences. To facilitate selective enrichment of target nucleic acids, specific probe oligonucleotides were attached covalently to free carboxyl groups of conducting polycarbonate/carbon fiber electrodes. Complementary oligonucleotides were enriched from analyte solutions by electric field supported methods. The analysis of the PCR product shows the efficiency and selectivity of the electrical enrichment. We have also shown that inexpensive and robust solid electrodes made of polycarbonate and conductive carbon powder are suitable for electrochemical examination of nucleic acids. The combination of electrochemical enrichment of DNA and subsequent electrochemical detection is a promising approach towards an inexpensive molecular diagnosis kit.

Development of a molecular diagnosis assay based on electrohybridization at plastic electrodes and subsequent PCR.

Technologies enabling specific recognition of medically relevant nucleic acid sequences will play a pivotal role in future medical diagnosis. Whereas many approaches to molecular diagnosis systems include DNA microarrays on chips and fluorometric detection, the basis of our approach is the use of inexpensive components like plastic or metal thin film electrodes with low multiplexing and an electrochemical detection unit. To increase the sensitivity, PCR can be used as an intermediate step. For selective enrichment, specific nucleic acid probes were covalently attached at their 5'-ends to conducting polycarbonate/carbon fiber electrodes. Complementary oligonucleotides were enriched at the electrodes by cyclic inversion of an electrochemical potential, transferred into a PCR vial and thermally or electrochemically desorbed. The analysis of the PCR product shows the efficiency and selectivity of the electrochemical enrichment. Hybridization of DNA was shown by electrochemical methods, in this work especially by differential pulse voltammetry (DPV) using the single strand specific hybridization redox indicator osmium(VIII)-tetroxide, and potentiometric stripping analysis (PSA). This combination of experimental methods is the basis for a molecular diagnosis system including a disposable nucleic acid modified working electrode for specific enrichment, detection and quantification, and an optional capillary PCR module for fast amplification.

Magnetic anisotropy of a cyclic octanuclear Fe(III) cluster and magneto-structural correlations in molecular ferric wheels.

The magnetic anisotropy of the cyclic octanuclear Fe(III) cluster [Cs subsetFe(8)[N(CH(2)CH(2)O)(3)](8)]Cl was investigated. Based on a spin Hamiltonian formalism and the consequent use of all symmetries, the magnetic anisotropy could be calculated exactly to first order, i.e., in the strong exchange limit. Experimentally, the magnetic anisotropy was investigated by magnetic susceptibility and high-field torque magnetometry of single crystals. The field and angle dependence of the torque at 1.7 K could be accurately reproduced by the calculations with one single parameter set, providing accurate results for the coupling constant and single-ion zero-field-splitting. These magnetic parameters are compared to those of several related hexanuclear ferric wheels and are discussed with respect to magneto-structural correlations for both coupling constant and single-ion anisotropy.

[Symbiotic relations and social development]. / Symbiotische Beziehungen und gesellschaftliche Entwicklung.

In order to take the influence of modern societies in the early parent-child relationship into account, the author recommends the conceptual distinction between primary and secondary symbiosis and points out its implications for psychoanalysis.