Photocages for protection and controlled release of bioactive compounds.

Using a sunscreen-based photocage, we have demonstrated that it is possible to prevent photodegradation of a bioactive compound and to achieve its controlled photorelease. The concept has been proven linking avobenzone, one of the most important UVA blockers, to ketoprofen, which is a representative example of a photosensitive drug.

Determination of the structure of adenine monolayers adsorbed at Au(110)/electrolyte interfaces using reflection anisotropy spectroscopy.

Reflection anisotropy spectroscopy (RAS) has been used to show that at saturation coverage adenine adsorbs on the Au(110)/electrolyte interface in a base-stacking configuration with the plane of the bases orientated vertically on the surface and with the long axis of the molecules parallel to the [110] direction. Changes in the RAS observed from adsorbed adenine as a result of changes in the potential applied to the Au(110) electrode could arise from slight changes in the orientation of the molecules in the vertical plane.

Orientation of ordered structures of cytosine and cytidine -monophosphate adsorbed at Au(110)/liquid interfaces.

It is demonstrated using reflection anisotropy spectroscopy that the adsorption of cytosine and cytidine -monophosphate at the Au(110) 1 x 2/electrolyte interface gives rise to ordered structures in which the base is oriented vertical to the surface and parallel to the [110] axis of the Au(110) plane.

Photochemistry of 2-hydroxy-4-trifluoromethylbenzoic acid, major metabolite of the photosensitizing platelet antiaggregant drug triflusal.

Triflusal is a platelet antiaggregant drug with photoallergic side effects. However, it is considered a prodrug since it is metabolized to 2-hydroxy-4-trifluoromethylbenzoic acid (HTB)--the pharmacologically active form. HTB was found to be photolabile under various conditions. Its major photodegradation pathway appears to be the nucleophilic attack at the trifluoromethyl moiety. The involvement of the triplet state in the photodegradation has been unequivocally proved by direct detection of this transient in laser flash photolysis and by quenching experiments with oxygen, cyclohexadiene and naphthalene. Finally, the photobinding of HTB to proteins such as bovine serum albumin has been demonstrated using ultraviolet-visible (UV-Vis) and fluorescence spectroscopy. Nucleophilic groups present in the protein appear to be responsible for the formation of covalent drug photoadducts, which is the first step involved in the photoallergy shown by triflusal.