The action of the environmental toxic Pb(2+) on photosynthetic electron transport was studied in thylakoid membranes isolated from spinach leaves. Fluorescence and thermoluminescence techniques were performed in order to determine the mode of Pb(2+) action in photosystem II (PSII). The invariance of fluorescence characteristics of chlorophyll a (Chl a) and magnesium tetraphenylporphyrin (MgTPP)...

Solid state 59Co nuclear magnetic resonance (NMR) spectra were recorded on diamagnetic complexes with general structure Co(Por)L2, where Por ) tetraphenylporphyrin, tetramethoxyphenylporphyrin, and octaethylporphyrin; and L ) imidazole, methylimidazole, pyridine, and isoquinoline. Measurements were carried out at different magnetic field strengths (4.7, 7.1, and 11.7 T) on both static and spinn...

Transient absorption decay rate constants (kobs) for reactions of electronically excited zinc tetraphenylporphyrin ((3)ZnTPP*) with triruthenium oxo-centered acetate-bridged clusters [Ru3(μ3-O)(μ-CH3CO2)6(CO)(L)]2(μ-pz), where pz = pyrazine and L = 4-cyanopyridine (cpy) (1), pyridine (py) (2), or 4-dimethylaminopyridine (dmap) (3), were obtained from nanosecond flash-quench spectroscopic data (...

The development of chemical systems with switchable molecular spins could lead to the architecture of materials with controllable magnetic or spintronic properties. Here, we present conclusive evidence that the spin of an organometallic molecule coupled to a ferromagnetic substrate can be switched between magnetic off and on states by a chemical stimulus. This is achieved by nitric oxide (NO) f...

Structure-activity relationships of ursane-type pentacyclic triterpenes obtained from natural sources and by chemical derivatization are reviewed. Ursolic acid, corosolic acid, and a new ursane-type pentacyclic triterpene, 7,24-dihydroxyursolic acid, were isolated from the methanolic extract of the leaves of the Bangladeshi medicinal plant, Saurauja roxburghii. Derivatization of ursolic acid by...