Search PubMed⌕ Search

Biomedical subjects

W Guschlbauer

Publications and source records attributed to W Guschlbauer.

At least 91 records · Page 5Linked to original sources
PubMed1976

Protonated polynucleotide structures. 18. Interaction of oligocytidylates with poly (G).

The faculty for and degree of oligo(C)-poly(G) interaction is described as an essentially chain length - sensitive phenomenon. At neutral pH under suitable experimental conditions, oligocytidylates of chain length greater than four associate with poly(G) to form double-stranded structures, as does poly(C). The extent of complex formation increases with degree of polymerization. The complex at acid pH is shown to be triple-stranded, of stoicheometry 2C/1G. The observation of a 2G/1C artifact is discussed.

Binding Sites↗
PubMed1975

Necleoside conformations. 19. Temperature and pH effects on the conformation of guanosine phosphates.

Proton magnetic resonance spectra at 250 MHz were measured as a function of temperature and pH of the three guanosine phosphates. From these data and previously published work the conformational parameters of these compounds were determinated. The phosphate group of Guo-5'-P changes its conformation around the C-O bond and its rotation is relatively slow at 20 degrees. At neutral pD the S conformation is favoured and the N form at acid pD. This conformational change is paralleled by a change in exocyclic rotamer distribution and takes place at the pK of the protonation of the base on N-7. Although correlation appears to exist between the various conformations, notable exceptions exist.

Deuterium↗
PubMed1974

Nucleoside conformations. 15. Flexibility of natural pyrimidine nucleosides around the glycosidic bond.

The flexibility of pyrimidine nucleosides has been investigated by measuring their circular dichroism in hydroalcoholic solutions over a large temperature range (-100 degrees to +40 degrees C). It was observed that ss-Uridine (Urd) and ss-Cytidine (Cyd) showed a decrease of the main dichroic band of about 40 percent, while sterically hindered nucleosides (alphaUrd, ara-Uracile, 02-2' anhy-dro-Urd, 2'3'-0-isopropylidene-Urd) showed only small decreases. It is concluded that the flexibility of the glycosidic linkage in conjunction with the pseudo-rotation of the sugar residue is responsible for these changes; the thermodynamic values which can be deduced from these decreases are compatible with an oscillatory motion around the glycosidic bond, but exclude anti-syn transformations in pyrimidine nucleosides.

Circular Dichroism↗
PubMed1974

Nucleoside conformations. XVII. A PMR study of 2'-anhydronucleosides and comparison with X-ray data.

A series of 2'-cyclo-nucleosides (2,2'-O-anhydro-uridine, -N(3)-uridine and cytidine and 8,2'-S-anhydro-guanosine) have been studied by PMR in DMSO and D(2)O. As expected these compounds are quite rigid, but their solution conformation is considerably different from that observed in single crystal x-ray studies. While the pyrimidine cyclonucleosides in the crystal form show a C(4')-endo conformation (pseudorotational phase angle P=212 degrees to 233 degrees ), their solution conformation is C(1')-exo (P=130 degrees to 138 degrees ) and the cyclothioguanosine shows a closely similar one (P=112 degrees ). Exocyclic rotamer distribution is different in the various compounds.

Crystallography, X-Ray↗