van Mhp Marcel Genderen

Quadruple hydrogen bonds of ureido-pyrimidinone moieties investigated in the solid state by 1H double-quantum MAS NMR spectroscopy

The structure of the quadruple hydrogen bond formed by ureido-pyrimidinone moieties is investigated in dimerised model compounds, as well as in a supramolecular polymer, by solid-state 1H double-quantum (DQ) NMR spectroscopy under fast magic-angle spinning (MAS). This NMR method combines the sensitivity of 1H NMR chemical shifts to the strengths of hydrogen bonds with quantitative information about dipole–dipole couplings between pairs of protons. Thus, two-dimensional 1H DQ MAS spectra provide particularly detailed insight into the arrangement of hydrogen bonds and allow proton–proton distances to be measured. For the supramolecular polymer, a thermally induced irreversible tautomeric rearrangement of the hydrogen-bonded moieties is elucidated in the bulk material. This process is associated with an Arrhenius activation energy of (145 ± 15) kJ mol−1, which can be rationalised in terms of hydrogen-bond dissociation and the reorientation of the supramolecular polymer chain.

Composition of the essential oil from the aerial parts of Piper pierrei C.DC. from Vietnam

Abstract The oil of Piper pierrei CDC. (local name Trâu nui, Tieu pierrei - Piper grown on the mountain) was isolated from its aerial parts by hydrodistillation. The oil was analyzed for the first time by high resolution GC, GC/MS and 13C-NMR. It contained more than 80 constituents of which 67 compounds have been identified. The major components were α-methylbenzyl cinnamate (28.0%) and an isomeric methylbenzyl cinnamate (18.1%), esters never found before.

Conformational transmission in 5'-P(IV) and 5'-P(V) TBP phosphorylated nucleosides : implications for DNA structure and dynamics

Abstract Specific conformational changes in DNA and RNA can be induced via a transient pentacoordination of the phosphorus atoms in the helix backbone. The details of this conformational transmission mechanism are discussed briefly, using experimental data that were obtained with a set of 5′-pIV and 5′-pV phosphorylated tetrahydrofurfuryl systems. A conformational study on the more realistic model system, the dinucleotide 2 in which a stabilized pentacoordinated phosphorus forms the internucleoside linkage, is presented. Furthermore, it has been found that methylation of the phosphate groups in d(TpTpTpTpTpT) results in the formation of a non-Watson & Crick type parallel duplex DNA structure, in which the two strands are joined via hydrogen bonding between the thymidine bases. Various physico-chemical techniques (e.g. NMR methods and UV hyperchromicity) were used to elucidate the structural details of the parallel duplex. Characteristic properties (parallellity, slimness, symmetry) are presented.

Problem-based learning at the Eindhoven/Maastricht BME program

In the first two years of the 5-year Eindhoven/Maastricht biomedical education (BME) program problem based learning is used to develop engineering, problem solving and communicative skills. These skills are put into practice in the projects and internships during the remainder of the educational program.

Conformational Transmission in DNA

Abstract This poster presents our recent results on DNA dimers in which a stable trigonal bipyramidal pentacoordinated phosphorus (Pv) structure forms the internucleoside linkage. Conformational analysis of the systems 1-4 with 300 and 500 1H NMR has shown that the Pv structure results in a distorted conformation of the backbone structuE (1).

Phosphate-methylated DNA fragments involved in parallel and antiparallel duplex formation : novel aspects of structure : stability and biological activity

Abstract Parallel duplexes are encountered for the phosphate-methylated DNA dinucleotides d(CpC) and d(TpC; for the Sp configuration exclusively. since inward location of the methyl group (Rp,) encounters severe steric interactions in the groove. A parallel duplex with T-T base pairs is found for the natural system d(T10) only after complexation of the cationic peptides polylysine and polyornithine with the phosphate groups, which diminishes phosphate-phosphate repulsions. For natural d(C10), parallel duplex formation is seen exclusively after complexation with polylysine, which only uses pro-S phosphate oxygens in the complexation. Polyornithine complexates with both pro-S and pro-R phosphate oxygens, leading to steric hindrance in the groove of the C-C duplex. For antiparallel duplexes of phosphate-methylated DNA (‘antisense’) with natural polynucleotides (‘sense’) it is found that the hybridization has a cooperative character. Furthermore, it is mentioned that long phosphate-methylated DNA fragments ca...