Utilizing new adamantyl spin traps in studying UV-B-induced oxidative damage of photosystem II

Two recently synthesized adamantyl nitrone spin traps, alpha-(4-pyridyl-N-oxide) (l-adamantyl)-N-nitrone (POAN) and alpha-(4-pyridyl)-(1-adamantyl) -N-nitrone (PyAN), have been found to be useful for detecting reactive oxygen species in thylakoid membranes. Both show lower inhibition of photosystem II (PSII) electron transport and higher stability of their radical adducts than those of the widely used corresponding phenyl nitrones. Both spin traps are suitable for detecting hydroxyl radicals in UV-B-exposed thylakoid membranes when applied at 800 mu M. Moreover, at 2 mM, POAN markedly retards W-B-induced D1 protein degradation. No such effect of PyAN is observed, and neither trap shows marked protection against UV-B-induced electron-transport inactivation. The different chemical structures of the two traps imply different penetration into the thylakoid membrane, suggesting that W-B-induced D1 protein degradation is brought about by hydroxyl radicals produced at special locations within the thylakoid membrane: these sites are accessible for POAN but inaccessible for the less membrane-penetrating PyAN. (C) 1999 Elsevier Science S.A. All rights reserved.