Biomimetic Chemistry: Radical Reactions in Vesicle Suspensions

Chemical reactivity represents the fundamental basis for studying processes in life sciences. In particular, the last years have seen the affirmation of the interdisciplinary field of chemical biology, which has motivated a strong interest in modeling chemical reactivity of biological systems, that is, improving chemical methodologies and knowledge in order to understand complex reaction pathways related to cellular processes. In this context the reactivity of free radicals revealed its enormous importance for several biological events, including aging and inflammation (Cutler & Rodriguez, 2003), therefore the modeling of free radical reactions under naturally occurring conditions has become a basic step in the research of fundamental mechanisms in biology. The assessment of modes of free radical reactivity has been found to be important at least in three areas: i) the examination of interactions at a molecular level leading to the discovery of radical-based processes involved in enzymatic activities, e.g., ribonucleotide reductase (Reichard & Ehrenberg, 1983), cyclooxygenase (Marnett, 2000), the drug effects of antitumorals (Goldberg, 1987), vitamin activities (Buettner, 1993); ii) The clarification of free radical processes that can lead to damage of biomolecules, together with the individuation of products, opening the way for the evaluation of the in vivo damage and its role in the overall cellular status (Kadiiskaa et al., 2005; Pryor & Godber, 1991); iii) the knowledge of free radical mechanisms allowing for new strategies to be envisaged in order to control the level of the damage and fight against the negative consequences (Halliwell & Gutteridge, 2000). These three main areas represent the core studies of free radicals using biomimetic models. In the last decade our group has developed the subjects of lipid and protein damages under biomimetic conditions, and in particular envisaged novel damage pathways for the transformation of these important classes of biomolecules. In this chapter biomimetic models will be examined, also mentioning work previously done by others in the field and the advancements carried by us. Information will be given on liposome vesicles, which is the basic context for examining free radical reactivity in heterogenous conditions, where the partition of the reactants occurs between the lipid and the aqueous environments, and this can influence the biological effects. The regioselectivity driven by the supramolecular organization of lipids in the vesicle double layer is another feature of the biomimetic model that has been related to the formation of trans lipids, specific markers of radical stress in cell 6