Fractal modeling of pyrene excimer quenching in phospholipid vesicles

The Dimerisation of Phthalocyanines

In this review, we have shown that the dimerisation of phthalocyanine compounds, notably here the sulphonated aluminium phthalocyanines, is dependent upon concentration, on the medium in which the dye is dissolved, and upon pH. Complex equilibria between various monomer and dimer species are observed as a function of pH, and the probable structures of the dimers elucidated by semi-empirical and ab initio calculations. The formation of a red-shifted dimer leads to the quenching of monomer singlet state in concentrated solution, in reverse micelles, and in lipid vesicles, and this behaviour can account for the fluorescence intensity distributions and decay characteristics of phthalocyanine dyes in living cells as a function of irradiation time.

Kinetics of bimolecular reactions in model bilayers and biological membranes. A critical review

The quantitative study of the probability of molecular encounters giving rise to a reaction in membranes is a challenging discipline. Model systems, model in the sense that they use model bilayers and model reactants, have been widely used for this purpose, but the methodologies employed for the analysis of the results obtained in experiments, and for experimental design, are so disparate that a concerned experimentalist has difficulty in deciding about the value of each approach. This review intends to examine the several approaches that can be found in the literature showing, when feasible, the weakness, strengths and limits of application of each of them. There is not, so far, a full experimental validation of the most promising theories for the analysis of reactions in two dimensions, what leaves open a large field for new research. The major challenge resides in the time range in which the processes take place, but the possibilities of the existing techniques for these studies are far from exhausted. We review also the attempts of several authors to quantitatively analyze the kinetics of reactions in biological membranes. Especially in this field, the recently developed microspectroscopies enclose a still unexplored potential.