Dual fluorophore-nitroxide molecules

Very fast electron transfers from P+ to bacteriochlorophyl (Bchl) and from (Bchl)- to QA do not depend on media dynamics and occur via conformationally non-equilibrium states (Fig.3.18). The dual fluorophore-nitroxide molecules (D-A) are also convenient objects for analysing the activity-dynamics relationship. The marked irreversible photoreduction of the nitroxide fragment of the dual probe incorporated into the binding site of HSA only took place when the nanosecond dynamical processes around the probe traced by ESR and fluorescence methods were detected (Rubtsova et al., 1993, Fogel et al, 1994 Likhtenshtein, 1986 Lozinsky et al., 2002). Similar results were reported for another model protein system, i.e. a-chymotrypsin with spin labeled methionin-92 groups (Belonogova et al., 1997). In the latter enzyme, the excited tryptophan group serves as an electron donor. 

Figure 6..5. Photochemical and photophysical processes in a dual fluorophore-nitroxide molecule. (Lozinsky et al. 2001). Reproduced with permission.

Lozinsky E., Shames A., and Likhtenshtein G.I. (2001) Dual fluorophore-nitroxide molecules Models for study of intramolecular fluorescence quenching and novel redox probes. In Recent Research Development in Photochemistry and Photobiology., V. 2, Transworld Research Network. Trivandrum, pp. 41-55. 

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