Catechol estrogens and catecholamines are metabolized to quinones, and the metabolite catechol (1,2-dihydroxybenzene) of the leukemogenic benzene can also be oxidized to its quinone. We report here that quinones obtained by enzymatic oxidation of catechol and dopamine with horseradish peroxidase, tyrosinase or phenobarbital-induced rat liver microsomes react with DNA by 1,4-Michael addition to form predominantly depurinating adducts at the N-7 of guanine and the N-3 of adenine. These adducts are analogous to the ones formed with DNA by enzymatically oxidized 4-catechol estrogens (Cavalieri,E.L., et al. (1997) PROC: Natl Acad. Sci., 94, 10937). The adducts were identified by comparison with standard adducts synthesized by reaction of catechol quinone or dopamine quinone with deoxyguanosine or adenine. We hypothesize that mutations induced by apurinic sites, generated by the depurinating adducts, may initiate cancer by benzene and estrogens, and some neurodegenerative diseases (e.g. Parkinson's disease) by dopamine. These data suggest that there is a unifying molecular mechanism, namely, formation of specific depurinating DNA adducts at the N-7 of guanine and N-3 of adenine, that could initiate many cancers and neurodegenerative diseases.

The behavior of chromate conversion coatings (CCCs) on the aluminum aircraft alloy AA 2024-T3 was examined by several types of experiments, using Raman spectroscopy as a primary technique. First, Raman spectra of the CCC film made from a commercial process revealed a Raman feature characteristic of Cr(VI) which was distinct from Raman bands of pure CrO 4 − 2 or Cr 2 O 7 − 2. Second, Raman spectroscopy was used to monitor migration of chromate species from a CCC film to an initially untreated alloy sample. The release of chromate from a CCC was demonstrated, as was redeposition of a chromate film on the fresh alloy surface. Formation of a Raman-observable Cr(VI)-containing deposit was more rapid in or near pits in the untreated alloy sample, and the deposit was spectroscopically very similar to the original CCC film. The initially untreated alloy became much less active toward corrosion after migration of chromate from the nearby CCC film, with the polarization resistance increasing by at least two orders of magnitude and the pitting potential increasing by 60 mV. The results clarify the mechanism of self-healing exhibited by CCC films, in which chromate species released from the CCC migrate to an actively corroding region and stop aluminum dissolution. The migrating chromate is selectively deposited at active corrosion sites, either by forming an insoluble Al/chromate is selectively deposited at active corrosion sites, either by forming an insoluble Al/chromate precipitate or by adsorption by previously formed corrosion

Sample fluorescence is detrimental to Raman spectroscopic analysis. Several algorithms are proposed to achieve automatic fluorescence rejection (AFR) based on shifted excitation Raman difference spectroscopy. The algorithms are mathematically linear and can be automated. The methods are based on a wavelength-tunable laser and the measurement and calibration of both the Raman and the excitation spectra. Applying the AFR methods to highly fluorescent samples significantly reduces the fluorescence background and reveals weak Raman features unidentifiable using traditional methods. Fixed pattern “noise” associated with the background can be completely removed. The merits of each algorithm are discussed and the best excitation frequency shift to perform the analysis is found to be comparable to the widths of major Raman peaks.

Various effects of chromate conversion coatings (CCCs) and chromate in solution on the corrosion of AA2024-T3 and pure Al are studied in this work. Raman spectroscopy was used to investigate the nature of chromate in CCCs through a comparison with the spectra of known standards and artificial Cr(III)/Cr(VI) mixed oxides. Chromate was shown to be released from CCCs and to migrate to and protect a nearby, uncoated area in the artificial scratch cell. However, experiments investigating the effect of chromate in solution on anodic dissolution kinetics under potentiostatic control indicated that large chromate concentrations were needed to have an effect.

The electrolyte plays an important role in governing the performance of Li-ion batteries. To understand more about the role of the electrolyte, transport properties such as the lithium salt self-diffusion coefficient and the lithium-ion transference number need to be measured. In this study, the diffusion coefficient was determined by pulsed field gradient nuclear magnetic resonance ͑NMR͒. The lithium-ion transference number was determined by an electrochemical polarization method and also calculated on the basis of diffusion coefficients, which were obtained by NMR measurement, of 7 Li and 19 F in the solutions of LiPF 6 in propylene carbonate. The lithium-ion transference number t Li + and the diffusion coefficient were found to be strongly dependent on the concentration.