Marie-Hélène Baron

Adenine and RNA in mineral samples. Surface-enhanced Raman spectroscopy (SERS) for picomole detections.

Studies on the interactions of biological macromolecules with mineral surfaces are crucial for the detecting biomarkers. But before this can be done for real samples like rocks or sediments, rational methods based on mineral models plus known amounts of nucleic acids must be developed. The methods must be very sensitive, as the amount of bound macromolecule may be very small. Surface-enhanced Raman spectroscopy (SERS) is perfect for detecting picomolar amounts of nucleic acid materials. In this study, the models used were adenine and GAAA hairpin for nucleic acids materials and a clay (montmorillonite) plus colloidal silver (used for SERS detection) for mineral supports. We have shown that OH(-) anions compete with adenine and the adenyl residues in the GAAA loop for adsorption onto nano-sized silver particles in basic medium. The GAAA adenyl moieties are less well adsorbed onto either clay or silver than is adenine. Also, the transfer of either adenine or the RNA hairpin from the clay to the silver aggregates is pH-dependent. Contact between adenine and the montmorillonite also seems to disperse adenine aggregates. The clay could also increase the flexibility of the RNA hairpin so that it is released from the clay at pH 10, and the affinity of its adenyl moieties for the metallic substrate is enhanced.

Quantitative Analysis of Vitamin A Degradation by Raman Spectroscopy

Vitamin A is known to support cell growth promotion, maintenance, and differentiation of epithelial tissues. Retinol is currently used in cosmetic formulations and products to deliver these and other benefits to the skin. However, retinol is known to be unstable and, therefore, remains of great concern to the cosmetic industry. The decomposition pathways of the retinoids in general have been previously postulated and investigated mostly by high-performance liquid chromatography (HPLC) with UV/Vis spectroscopy. In our studies, we examined specific conditions at which retinol degrades and subsequently identified and quantified the products of retinol decomposition by Raman spectroscopy. We reveal which experimental settings and computational tools allow monitoring of in situ evolution of an all-trans retinol solution when submitted to UV light in the presence of oxygen.

Protein adsorption on soil mineral surfaces

The development of research in the domain of protein adsorption on solid surfaces arises from numerous technological and medical applications that depend on this phenomenon (immobilised enzyme reactors, biocompatibility…). Protein adsorption is also a natural phenomenon in terrestrial and aquatic ecosystems. Bacteria and fungi involved in the biodegradation of organic matter secrete extracellular enzymes. They are able to cleave the high molecular weight polymers of the organic matter. Then the soluble monomers easily cross the membranes of the plant cells. Soils have a large solid surface area for the volume of the liquid filling the pore space and also high adsorptive properties. The interactions of extracellular enzymes with mineral surfaces is likely to be important.