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The fluorescence lifetimes of Cu(II), Cu(I), Ag(I), Hg(II), Co(II), and Ni(II) azurin Pae from Pseudomonas aeruginosa and Cu(II), Cu(I), and Hg(II) azurin Afe from Alcaligenes faecalis were measured at 295 K by time-correlated single-photon counting. In addition, fluorescence lifetimes of Cu(II) azurin Pae were measured between 30 and 160 K and showed little change in value. Ultraviolet absorption difference spectra between metalloazurin Pae and apoazurin Pae were measured, as were the fluorescence spectra of metalloazurins. These spectra were used to determine the spectral overlap integral required for dipole-dipole resonance calculations. All metalloazurins exhibit a reduced fluorescence lifetime compared to their respective apoazurins. Forster electronic energy transfer rates were calculated for both metalloazurin Pae and metalloazurin Afe derivatives; both enzymes contain a single tryptophyl residue which is located in a different position in the two azurins. These azurins have markedly different fluorescence spectra, and electronic energy transfers occur from these two tryptophyl sites with different distances and orientations and spectral overlap integral values. Intramolecular distances and orientations were derived from an X-ray crystallographic structure and a molecular dynamic simulation of the homologous azurin Ade from Alcaligenes denitrificans, which contains both tryptophyl sites. Assignments were made of metal-ligand-field electronic transitions and of transition dipole moments and directions for tryptophyl residues, which accounted for the observed fluorescence quenching of Hg(II), Co(II), and Ni(II) azurin Pae and Cu(II) and Hg(II) azurin Afe. The fluorescence of azurin Pae is assigned as a 1Lb electronic transition, while that of azurin Afe is 1La. The marked fluorescence quenching of Cu(II) azurin Pae and Cu(I) azurin Pae and Afe is less well reproduced by our calculations, and long-range oxidative and reductive electron transfer, respectively, are proposed as additional quenching mechanisms. This study illustrates the application of Forster electronic energy transfer calculations to intramolecular transfers in structurally well characterized molecular systems and demonstrates its ability to predict observed fluorescence quenching rates when the necessary extensive structural, electronic transition assignment, and spectroscopic data are available. The agreement between Forster calculations and quenching rates derived from fluorescence lifetime measurements suggests there are limited changes in conformation between crystal structure and solution structures, with the exception of the tryptophyl residue of azurin Afe, where a conformation derived from a molecular simulation in water was necessary rather than that found in the crystal structure.

Increasing the degree of crystallization of unoriented 66 or 610 nylon increases the stiffness, yield point, tensile strength, and hardness, but reduces the impact strength, particularly in the high crystallinity range. The impact strength was increased by increasing the molecular weight, but the other properties were substantially unchanged. The effect of varying water content was independent of the effect of varying crystallinity and generally acts in the opposite direction.

SUMMARY The Sarbanes-Oxley Act (SOX) and its associated regulations significantly expanded the oversight role of audit committees and improved independence, but regulators bypassed restrictions on audit committee equity incentives. We examine the association of audit committee members' equity incentives and financial reporting quality in the post-SOX time period. We find that audit committee members' stock-option awards and holdings are positively associated with the likelihood of meeting/beating analyst earnings forecasts. On average, a company whose audit committee holds the mean value of exercisable option holdings is associated with a 10.0 percent increase in the likelihood of meeting or just beating its consensus analyst forecast. This effect increases to 17.8 percent for companies with high-growth opportunities. These results suggest that—even in the post-SOX era—the stock-option incentives provided to independent audit committee members are associated with reduced financial reporting quality. JEL Classifications: M41, M42