Pyrene amino

Compared to the extensive data that have been obtained on the mutagenicity of nitro PAHs in S. typhimurium, relatively little is known about the metabolism of these compounds in this organism. Messier et al. (67) reported that incubation of 1-nitropyrene with S. typhimurium TA98 yielded 1-aminopyrene and 1-acetylaminopyrene as major and minor metabolites, respectively. The reduction of 1-nitropyrene was slow and was accompanied by a slow formation of DNA adducts. When incubations were conducted with the nitroreductase-deficient strain, TA100 F50, both the extent of 1-amino-pyrene formation and DNA binding decreased. Howard ej al. (71,115) also found reduction of 1-nitropyrene to 1-aminopyrene in strains TA98, TA1538 and ATCC 14028. 

An example of group (iv) which also illustrates rather well the fact that A and A frequently behave very differently has been reported by Urban and Weller . The fluorescence of certain substituted amino-pyrenes of the type... 

The dependence of fluorescence spectra and intensity of fluorescence of ionizable compounds on the pH of the solution enables them to he used as fluorescence indicators. The naphthyl sulphonic acids are typical examples. In the case of hydroxy and amino pyrene sulphonic acids, sharp changes in fluorescence do not occur at the same pH values as changes in absorption. This has been explained by Forster30 by considering the attainment of the ionic equilibrium appropriate to the excited state within its life time. The fluorescence of some purines and pyrimidines also depends on the acidity or alkalinity of the medium31. 

An electrochemical luminescence-based immunoassay has been presented with HSA labeled with the aromatic hydrocarbon amino-pyrene (Ikariyama et al., 1985). The pyrene-labeled HSA luminesces during reduction at a platinum electrode, and on binding to Ab, the intensity of luminescence is decreased. A detection limit of 10 M for HSA was obtained. Labels with greater luminescence efficiency should provide lower detection limits. 

Figs. 4-15. 4-16 pH dependence of CVs for poly(l-amino pyrene) (4-15. left, with pH values indicated, reproduced with permission from ref. [48]), and for poly(2,3-diamino naphthalene) (4-16. reproduced with permission from ref. [49]). 

From the difficulties encountered with interpretation of CVs which the discussions above amply show, it would appear that other voltammetric methods, especially differential methods, would have found wider application to CPs. This has unfortunately not been the case. The results in Figs. 4-17-a.b.c and 4-18 represent some of the few studies of this nature. In Fig. 4-17. the results of CV and of Differential Pulse Voltammetry (DPV) are compared. The latter is a technique in which a small potential pulse is superimposed on a staircase potential function with the difference between the post-pulse and pre-pulse current measured (inset in Fig. 4-171. The differential method yields peak-shaped curves unencumbered by residual current tails, as in CVs, and thus a clearer identification of peaks and their widths. Fig. 4-19 then shows DPV of Poly(phenylene vinylene) used to compute the bandgap, as described earlier. Normal Pulse Voltammetry (NPV), in which a sort of digital pulse-ramp is applied in place of the analog ramp of CV and the current sampled at the end of the pulse [50], has been applied to poly(l-amino pyrene) [48], yielding redox potentials as well as diffusion coefficients (Fig. 4-181. Other differential methods such as Square Wave Voltammetry have been applied to poly(aromatic amines) in the author s laboratories. There is however little other extant work with pulse voltammetry of CPs, although the very brief results above clearly provide a strong indication for it. 

NPV results may also be used to calculate apparent diffusion coefficients also employing Cottrell relationships. Oyama et al. [48] have used the NPV voltam-mograms of Fig. 4-19 (III.24.flO) to calculate apparent diffusion coefficients (with t now being replaced by r, the NPV sampling time) for C104 in poly(1-amino-pyrene), of 1.3 X 10- ° cmVs. 

Oyama and Hirokawa [804] described a potentiometric pH sensor that used a film of poly(l-amino pyrene) (P(lAPyre)) in which no internal standard solution, as is required in conventional glass pH electrodes, was used. The pH detection was based on the sensor functioning as an ion-sensitive field effect transistor (ISFET). The sensor had high ion selectivity with respect to Na, and Ca, and insensitivity to O2, much like a conventional pH glass-membrane electrode. Response time was in the 30 to 60 sec region, with excellent linearity of response in the pH 4.0 to 10.0 region. 

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