Quantification of monomer elution and carbon-carbon double bonds in dental adhesive systems using HPLC and micro-Raman spectroscopy.

Objectives: To quantify monomer elution from different adhesive systems using reverse-phase high-performance liquid chromatography (HPLC) and correlate this elution with the ratio of carbon-carbon double bonds from monomer to polymer (RDB) obtained using micro-Raman spectroscopy.

Methods: Thirty dentine discs were cut from 30 human, intact, third molars and randomly allocated to five groups according to the adhesive applied: total-etch, Excite (Ivoclar Vivadent), two-bottle self-etch, Clearfil SE (Kuraray), one-bottle self-etch, Clearfil 3S (Kuraray), ormocer-based, Admira (Voco) and Filtek Silorane adhesive system (FS) (3M ESPE). Monomer elution was studied 1h, 6h, 24h, 96h and 7 days after immersion in 75% ethanol/water.

A phenanthrene modified RNA hairpin.

The influence of hairpin loop replacement with the phenanthrene moiety in RNA was investigated. The stability of this novel structure was compared to a hairpin with a U(4) loop, an extra stable tetra-loop (UUCG), and an analogous phenanthrene modified DNA hairpin. Thermal denaturation experiments and CD spectra were used to study the structure and stability of the modified hairpin.

Monomeric and heterodimeric triple helical DNA mimics.

The construction of artificial triple helical structures with oligonucleotides containing non-nucleosidic phenanthrenes and pyrenes is described. The polyaromatic building blocks, which are used as connectors between the Hoogsteen strand and the Watson-Crick hairpin, lead to a significant stabilization of intramolecular triple helices. Description of the relative orientation of pyrene building blocks is rendered possible by the observation of exciton coupling in the circular dichroism spectra.

Triple-helix mediated excimer and exciplex formation.

The synthesis and properties of triple-helical hybrids containing non-nucleosidic polyaromatic building blocks are described. Clamp-type oligonucleotides containing a non-nucleosidic pyrene linker form stable triple helices with a polypurine target strand containing a terminal pyrene or phenanthrene moiety. Stacking interactions between the unnatural building blocks enhance triplex stability and lead to strong excimer or exciplex formation, which is monitored by fluorescence spectroscopy.