Quadruplex and pentaplex self-assemblies of oligonucleotides containing short runs of 8-aza-7-deaza-2'-deoxyisoguanosine or 2'-deoxyisoguanosine.

Oligonucleotides containing 8-aza-7-deaza-2'-deoxyisoguanosine (4) were investigated regarding their self-assembly in aqueous solution. The aggregation of 4 was compared with that of oligonucleotides containing 2'-deoxyisoguanosine (2b) and 2'-deoxyguanosine (1b). For this purpose the phosphoramidite of 4 was synthesized which was protected by a dibutylaminomethylidene residue at the amino group and a diphenylcarbamoyl residue at the 2-oxo function. Solid-phase synthesis furnished oligonucleotide containing short runs of the nucleoside 4. The self-assembly of the oligonucleotide 5'-d(T(4)4(4)T2) was studied by ion-exchange chromatography. The formation of a pentaplex was observed in the presence of Cs+, while a tetraplex is formed when the counter ion is Na+ or Rb+. The cation selectivity of the oligonucleotide 5'-d(T(4)4(4)T2) was found to be different from the parent 5'-d(T(4)isoG(4)T2) which was forming the tetraplex as well as a pentaplex in aq RbCl solution.     

Maximum-entropy determination of self-association distribution functions; daunorubicin and ATP.

In the present paper we show how one can use the perturbation of some molecular optical property (for example circular dichroism or chemical shift) as a function of concentration to construct cluster distribution functions describing the self-association of molecules in solution. The optical data are first converted into data giving the variation of the average extent of clustering as a function of the total concentration and then, using straightforward thermodynamics, a set of moments of the cluster distribution function can be obtained. Utilizing the maximum-entropy method, the moments are then used to calculate approximate distribution functions, where the more moments that are used the better the approximation obtained. Given the probability distribution for clusters of different sizes one can then calculate the equilibrium constant for each stage of association. Thus one converts average degree of association into equilibrium constants without having to use any specific model. By this method one can clearly tell whether the equilibrium constants remain constant, increase, or decrease with the number of molecules in a cluster. We apply the method to literature data for two systems, namely daunorubicin, which has a strong tendency to cluster in solution, and Mg(ATP)(2-) which forms weaker clusters. We find that the successive equilibrium constants for adding a monomer to a cluster are approximately constant for daunorubicin but clearly decrease as a function of increasing cluster size for Mg(ATP)(2-).     

Purification and characterization of a hemagglutinin isolated from the leaves of Chenopodium (Chenopodium amaranticolor).

A hemagglutinin was isolated and purified from the leaves of Chenopodium (Chenopodium amaranticolor) using ion-exchange chromatography and affinity chromatography on fetuin-agarose matrix. It agglutinated rabbit erythrocytes. The hemagglutinin had a native molecular mass of 58 kDa, as estimated by gel filtration and showed a single band of molecular mass of 33 kDa on SDS-PAGE. It showed hemagglutination activity over the pH range 3-12 and was found to be stable up to 70 degrees C. On isoelectrofocussing, the pI of this hemagglutinin was estimated to be 5.25. However, it was found to contain seven charge variants when isoelectrofocussing was performed in presence of 6M urea.     

Evidence of reduced flexibility in disulfide bridge-depleted azurin: a molecular dynamics simulation study.

Two molecular dynamics simulations have been performed for 2 ns, at room temperature, on fully hydrated wild type and Cys3Ala/Cys26Ala double-mutant azurin, to investigate the role of the unique disulfide bridge on the structure and dynamics of the protein. The results show that the removal of the [bond]SS[bond] bond does not affect the structural features of the protein, whereas alterations of the dynamical properties are observed. The root mean square fluctuations of the atomic positions are, on average, considerably reduced in the azurin mutant with respect to the wild type form. The number of intramolecular hydrogen bonds between protein backbone atoms that are lost during the simulation, with respect to the starting configuration, are reduced in the absence of the disulfide bond. The analysis of the dynamical cross-correlation map, characterising the protein co-ordinated internal motions, demonstrates in the mutated azurin a significant decrease in anti-correlated displacements between protein residues, with the only exception occurring in the region of the mutation sites. The overall findings show a relevant reduction in flexibility as a consequence of the disulfide bridge depletion in azurin, suggesting that the [bond]SS[bond] bond is a structural element which significantly contributes to the dynamic properties of the native protein.     

Cervical screening in Luxembourg: 1990–1999

For quality assurance purposes, the results of the 1990's obtained by the National Cervical Cancer Screening Programme (NCCSP) launched in 1962 were reviewed. The positive cytodiagnosis, the histologically verified in situ and invasive cervical cancers and the mortality rates were reported.     

Latency of Botrytis cinerea Pers.: Fr. and Biochemical Studies During Growth and Ripening of Two Grape Berry Cultivars, Respectively Susceptible and Resistant to Grey Mould

Latency and development of Botrytis cinerea were assessed under field conditions and after artificial inoculation of two grape varieties, Gamay (susceptible) and Gamaret (resistant). When the percentage of latent Botrytis was the same for both varieties, severity of visible grey mould remained very low in Gamaret berries, while Gamay clusters were destroyed by the disease to a high percentage. Some biochemical parameters were measured in berries, such as constitutive and induced anti‐fungal compounds, polymeric proanthocyanidins and lipid peroxidation products as markers of senescence. Differences were observed in polymeric proanthocyanidins (PPRA) of Gamaret compared with those of Gamay. Concentration and mean degree of polymerization (mDP) of PPRA were always higher in the berries of the resistant variety. The inhibitory effect of Gamaret PPRA on enzyme activity remained until harvest whereas Gamay PPRA lost their inhibitory activity at the beginning of véraison. Based on these results, resistance to B. cinerea seems to be linked to the maintainance of the fungus in its latent form in berries, mainly due to the ability of Gamaret PPRA to inhibit macerating fungal enzyme activities.