Metallocene-DNA: synthesis,molecular and electronic structure and DNA incorporation of C5-ferrocenylthymidine derivatives

Ferrocenylthymidine derivatives have been prepared by Pd-catalysed cross-coupling between ethynylferrocene or vinylferrocene and 5-iodo-2'-deoxyuridine. In the latter case a mixture of trans (2a) and gem (2b) isomers was obtained. The cis-vinylferrocenyl (2c), and ethylferrocenyl (3) derivatives were obtained by catalytic hydrogenation of ethynylferrocenyl-dT (1a), and 2c respectively. Single-crystal X-ray data for 1a, the ferrocenyl-2'furano-pyrimidone 1b, and 2a show that the nucleobase is essentially co-planar with the substituted Cp ring of the metallocene. The selective reduction of the linkage between the ferrocenyl and thymidine moieties, from -C identical to C- to -CH2CH2-, causes a shift in the reduction potential of -124 mV. DFT calculations for the one-electron oxidised species indicate that the diminished conjugation reduces the spin transfer onto the bridging C2 group, but has less effect on the extent transferred to the nucleobase from the ferrocenyl group. Compound 1a was incorporated site-specifically into DNA oligonucleotides by using automated solid-phase methods. However, some interconversion of 1a-->1b occurs, even under rapid mild conditions of deprotection.     

Design and commissioning of a timestamp-based data acquisition system for the DRAGON recoil mass separator

The fission fragment mass distribution followed by neutron emission is studied for the ²³⁸U(¹⁸O,f) reaction using the asymmetric two-center shell model. Within the thermodynamic approach, excitation energy carried by the compound nucleus is dissipated in the emission of a pair of neutrons in several consecutive steps. Therefore, we have considered 2–12 (in step of 2) neutron emission channels in our formalism. The mass distribution corresponding to 8-neutron emission channel compares reasonably well with the experimental data. The observed fine structure dips corresponding to shell closure (Z = 50 and N = 82 of individual fission fragment arise mainly due to shell structure in the mass parameters. However, an exact location and magnitude of the dip at A = 124 in the mass distribution depends on how the temperature modifies masses and, also, on the precise information of pre- and post-neutron emission data. This suggests a possible importance of extending these calculations to get new insight into an understanding of the dynamical behaviour of fragment formation in the fission process.     

Use of contactless conductivity detection for non-invasive characterisation of monolithic stationary-phase coatings for application in capillary ion chromatography

A capacitively-coupled contactless conductivity detector (C4D) has been utilised as an on-capillary detector within a capillary ion chromatograph, incorporating a reversed-phase monolithic silica capillary column semi-permanently modified with a suitable ionic surfactant. The monolithic capillary column (150 x 0.1 mm i.d.) was modified using sodium dioctyl sulfosuccinate (DOSS), an anionic surfactant, for the separation of small inorganic and organic cations. With the use of the on-capillary conductivity detector, the longitudinal homogeneity and temporal stability of the coating were investigated. The approach allowed a detailed non-invasive observation of the nature of the ion-exchange coating over time, and an example of an application of the technique to produce a longitudinal stationary-phase charge gradient is shown. An investigation of the basis of the measured on-capillary conductivity was carried out with a counter ion study, clearly showing the on-capillary detection technique could also distinguish between chemical forms of the immobilised ion exchanger. The above method was used to produce a stable and homogeneously-modified monolithic ion-exchange capillary column, for application to the separation of inorganic alkaline earth cations and amino acids.     

Progranulin is expressed within motor neurons and promotes neuronal cell survival

Background

Progranulin is a secreted high molecular weight growth factor bearing seven and one half copies of the cysteine-rich granulin-epithelin motif. While inappropriate over-expression of the progranulin gene has been associated with many cancers, haploinsufficiency leads to atrophy of the frontotemporal lobes and development of a form of dementia (frontotemporal lobar degeneration with ubiquitin positive inclusions, FTLD-U) associated with the formation of ubiquitinated inclusions. Recent reports indicate that progranulin has neurotrophic effects, which, if confirmed would make progranulin the only neuroprotective growth factor that has been associated genetically with a neurological disease in humans. Preliminary studies indicated high progranulin gene expression in spinal cord motor neurons. However, it is uncertain what the role of Progranulin is in normal or diseased motor neuron function. We have investigated progranulin gene expression and subcellular localization in cultured mouse embryonic motor neurons and examined the effect of progranulin over-expression and knockdown in the NSC-34 immortalized motor neuron cell line upon proliferation and survival.

Results

In situ hybridisation and immunohistochemical techniques revealed that the progranulin gene is highly expressed by motor neurons within the mouse spinal cord and in primary cultures of dissociated mouse embryonic spinal cord-dorsal root ganglia. Confocal microscopy coupled to immunocytochemistry together with the use of a progranulin-green fluorescent protein fusion construct revealed progranulin to be located within compartments of the secretory pathway including the Golgi apparatus. Stable transfection of the human progranulin gene into the NSC-34 motor neuron cell line stimulates the appearance of dendritic structures and provides sufficient trophic stimulus to survive serum deprivation for long periods (up to two months). This is mediated at least in part through an anti-apoptotic mechanism. Control cells, while expressing basal levels of progranulin do not survive in serum free conditions. Knockdown of progranulin expression using shRNA technology further reduced cell survival.

Conclusion

Neurons are among the most long-lived cells in the body and are subject to low levels of toxic challenges throughout life. We have demonstrated that progranulin is abundantly expressed in motor neurons and is cytoprotective over prolonged periods when over-expressed in a neuronal cell line. This work highlights the importance of progranulin as neuroprotective growth factor and may represent a therapeutic target for neurodegenerative diseases including motor neuron disease.     

Observations of the Askaryan effect in ice

We report on observations of coherent, impulsive radio Cherenkov radiation from electromagnetic showers in solid ice. This is the first observation of the Askaryan effect in ice. As part of the complete validation process for the ANITA experiment, we performed an experiment at the Stanford Linear Accelerator Center in June 2006 using a 7.5 metric ton ice target. We measure for the first time the large-scale angular dependence of the radiation pattern, a major factor in determining the solid-angle acceptance of ultrahigh-energy neutrino detectors.     

Development of a contactless conductivity detector cell for 1.6 mm O.D. (1/16th inch) HPLC tubing and micro-bore columns with on-column detection

A capacitively coupled contactless conductivity detector cell was designed and constructed suitable for standard HPLC 1.6 mm o.d. (1/16') tubing and columns. Bode plots were acquired in order to determine the optimum input frequency for the new detector cell, with three feedback resistors of increasing resistance (1 MOmega, 3.3 MOmega and 4.7 MOmega) alternately fitted to maximize sensitivity. To evaluate the new detector geometry, a 190 mm x 0.381 mm i.d. (1.59 mm o.d.) column packed with Dionex OmniPac 8.5 microm PAX-100 anion exchange resin was used, with an eluent of 0.5 mM sodium benzoate containing 2% methanol, pumped at 20 microL min(-1), with detection taking place 'on-column'. Standard analytical performance criteria were used to compare the test detector with a commercially available TraceDec C(4)D capillary (360 microm o.d.) detector, with the new detector cell matching the performance of the commercial instrument in terms of linearity, sensitivity and reproducibility. In 'on-column' detection mode, the detector cell could be moved during (or between) chromatographic runs along the length of the packed column bed, to shorten the effective length of the column and thus reduce the retention time of strongly retained sample components, whilst maintaining the resolution of weakly retained components. In addition, the detector could also be applied to the evaluation of the stationary phase packing homogeneity by physically scanning the entire length of the micro-bore column with the moveable detector cell.