This work compares the effect of photogenerated singlet oxygen (O 2 ( 1 ⌬ g )) (type II mechanism) and free radicals (type I mechanism) on cytochrome c structure and reactivity. Both reactive species were obtained by photoexcitation of methylene blue (MB ؉ ) in the monomer and dimer forms, respectively. The monomer form is predominant at low dye concentrations (up to 8 M) or in the presence of an excess of SDS micelles, while dimers are predominant at 0.7 mM SDS. Over a pH range in which cytochrome c is in the native form, O 2 ( 1 ⌬ g ) and free radicals induced a Soret band blue shift (from 409 to 405 nm), predominantly. EPR measurements revealed that the blue shift of the Soret band was compatible with conversion of the heme iron from its native low spin state to a high spin state with axial symmetry (g ϳ 6.0). Soret band bleaching, due to direct attack on the heme group, was only detected under conditions that favored free radical production (MB ؉ dimer in SDS micelles) or in the presence of a less structured form of the protein (above pH 9.3). Matrix-assisted laser desorption ionization time-of-flight mass spectrometry of the heme group and the polypeptide chain of cytochrome c with Soret band at 405 nm (cytc405) revealed no alterations in the mass of the cytc405 heme group but oxidative modifications on methionine (Met 65 and Met 80 ) and tyrosine (Tyr 74 ) residues. Damage of cytc405 tyrosine residue impaired its reduction by diphenylacetaldehyde, but not by ␤-mercaptoethanol, which was able to reduce cytc405, generating cytochrome c Fe(II) in the high spin state (spin 2).

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Organic matter is an important source of information on the transport and consolidation processes of sediments. In this study, the isotopes of carbon and nitrogen (δ 13 C and δ 15 N), total organic carbon (TOC), total nitrogen, carbon/nitrogen (C/N) ratio, and 13 C-NMR were utilized to understand the origin and behavior of organic material in the Abrolhos region. It were analyzed nine sediment cores taken from a mangrove, a channel between the mainland and the coral reefs. The average value of the C/N ratio in the mangrove was 18, which characterizes purely terrigenous areas. For the reefs, the average value of the C/N ratio was 8,which is characteristic of marine and coastal regions. For the sediment cores taken from the channel, the average value of the C/N ratio was 10, a typical value of areas under the influence of mangroves. The mean values of δ 13 C were -26.9‰ for the mangrove, -20.7‰ for the channel region, and -18.2‰ for the reefs. This variation is associated with the main source of organic matter, which in the mangrove is derived from vascular plants (mainly C3 metabolism) and for the reefs is derived from phytoplankton. The 13 C-NMR results corroborate the isotopic and elemental analyses. The analyses of these cores indicate that the anthropogenic influence on the coast did not significantly alter the composition of the material that has been deposited in about the last 80 years in the region of study.