Mapping of possible prion protein self-interaction domains using peptide arrays

Background  

The common event in transmissible spongiform encephalopathies (TSEs) or prion diseases is the conversion of host-encoded protease sensitive cellular prion protein (PrP^C) into strain dependent isoforms of scrapie associated protease resistant isoform (PrP^Sc) of prion protein (PrP). These processes are determined by similarities as well as strain dependent variations in the PrP structure. Selective self-interaction between PrP molecules is the most probable basis for initiation of these processes, potentially influenced by chaperone molecules, however the mechanisms behind these processes are far from understood. We previously determined that polymorphisms do not affect initial PrP^C to PrP^Sc binding but rather modulate a subsequent step in the conversion process. Determining possible sites of self-interaction could elucidate which amino acid(s) or amino acid sequences contribute to binding and further conversion into other isoforms. To this end, ovine – and bovine PrP peptide-arrays consisting of 15-mer overlapping peptides were probed with recombinant sheep PrP^C fused to maltose binding protein (MBP-PrP).     

Tetrathiafulvalene-acetylene scaffolding: new pi-electron systems for advanced materials

Novel extended tetrathiafulvalenes (TTFs) with hexa-2,4-diyne-1,6-diylidene spacers between the two 1,3-dithiole rings and laterally appended alkynyl moieties for one- and two-dimensional scaffolding were synthesised and investigated for their electronic properties.     

Oxidation of ethanol by Ce(IV) in acid nitrate medium

The oxidation kinetics of ethanol by Ce(IV) has been studied as a function of pH, nitrate and water concentration. Even at high concentration of H⁺ and NO ₃ ^– several species appear to exist. The oxidation is fastest in strongly acidic medium without added nitrate ions.

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Ce(IV) pH, . H⁺ NO ₃ ^– , Ce(IV). .

     

Enyne metathesis-oxidation sequence for the synthesis of 2-phosphono pyrroles: proof of the "yne-then-ene" pathway

A new tandem reaction sequence has been developed for the synthesis of 2-phosphono pyrroles. The sequence consists of ring-closing enyne metathesis of a substituted aminophosphonate, containing a terminal alkyne and an internal alkene, in combination with in situ oxidation of the produced 3-pyrrolines using tetrachloroquinone. By analyzing the formation of the end and certain byproducts, taking into account the difference in reactivity of different substrates and carefully studying spectroscopic data, it was found that the reaction proceeds by means of the "yne-then-ene" pathway. During the initiation phase, a new ruthenium carbene is formed which continues the propagation cycle.     

Determination of the structure factor for concentrated silica dispersions using small angle x-ray scattering I. Simulation

The structure factor of a concentrated colloidal suspension is an important means in the characterization of the interaction forces between the colloidal particles. It can, in principle, be determined with small angle x-ray scattering. To avoid unacceptably long measuring times, one has to use a high power x-ray source or a slit collimation camera. The first is not readily accessible because of the very high costs. The latter is available in many laboratories, but here the fundamental information is contained in the data in a complicated way. A so-called desmearing operation is needed to reveal this information. Because of the different experimental errors and their sensitivity to the desmearing, the accuracy of the structure factor will be rather limited. In this paper we simulate the experimental errors separately to check their influence in combination with the desmearing.Although the overall accuracy is limited some important features can be determined. The value atK=0 and thus the osmotic compressibility can be calculated, and the position and the height of the first maximum in the structure factor are quite reliable too. This gives some insight in the type of interaction and the influence of polydispersity.Special attention should be given to the determination of the form factor by using extra long measuring times for the very diluted sample, this will improve the overall accurary.     

Synthesis of 2-phosphonopyrroles via a one-pot RCM/oxidation sequence

A four-step synthesis of 2-phosphonopyrroles is presented starting from suitable aldehydes. The key step in the synthesis involves a one-pot ring-closing metathesis/oxidation sequence of a functionalized alpha-aminoalkenyl phosphonate. Notwithstanding the presence of a nucleophilic nitrogen atom and high substitution patterns in the substrate, the results of the RCM reaction are excellent using mild reaction conditions. Furthermore, a synergism is observed between the RCM catalyst and the oxidizing agent, causing higher oxidation rates and allowing reaction for substrates that normally fail to ring close under standard RCM conditions.     

Divided powers in Chow rings and integral Fourier transforms

We prove that for any monoid scheme M over a field with proper multiplication maps M×M→M, we have a natural PD-structure on the ideal CH>0(M)⊂CH_∗(M) with regard to the Pontryagin ring structure. Further we investigate to what extent it is possible to define a Fourier transform on the motive with integral coefficients of the Jacobian of a curve. For a hyperelliptic curve of genus g with sufficiently many k-rational Weierstrass points, we construct such an integral Fourier transform with all the usual properties up to N²-torsion, where N=1+⌊log₂(3g)⌋. As a consequence we obtain, over , a PD-structure (for the intersection product) on N²⋅a, where a⊂CH(J) is the augmentation ideal. We show that a factor 2 in the properties of an integral Fourier transform cannot be eliminated even for elliptic curves over an algebraically closed field.     

Donor-substituted cyanoethynylethenes: powerful chromophores for opto-electronic applications

Donor-substituted cyanoethynylethenes (CEEs) were synthesised, structurally characterised and investigated for their electronic and two-photon absorption properties, revealing exceptionally strong intramolecular charge-transfer interactions.