6b-e correspond to the 65Cu isotope

(μ/(μNI) (65Cu) = 1.5877 compared to μ/(μNI) (63Cu) = 1.484897, [22]). Representative spectra from Cu/EGCG at S-band frequencies are presented in Fig. 7, The spectra from the individual Cu isotopes are seen more clearly at this frequency, and are illustrated in the expanded spectrum in Fig. 7g. The corresponding results for the Cu/GA system are available as supplementary material (Figure Apoptosis Compound Library ic50 S13). Because of incomplete averaging of the spectral anisotropy, only one of the four Cu(II) hyperfine peaks (that at the highest field) is well resolved in the solution spectra of each of the Cu(II) EGCG complexes in fluid solution at X-band frequencies (Fig. 3). The high field peak of Complex I is clearly visible in Fig. 3b, but the spectra of Complexes II and III strongly overlap (Fig. 3c), and their individual components are not resolved from one another. However, the position of the high field peak from Complex III was determined from the spectrum recorded at very high pH where the contribution from Complex II was weak (Fig. 3d). Somewhat better resolution of the component peaks was observed in the fluid solution spectra from the Cu/GA system at X-band frequencies by Ferreira Severino et al. [9] (see also Figure S14 for a full set of data), but even with this smaller ligand the resolution was not good. There are a number of reasons for the lack of resolution

of the component peaks in the spectra. Firstly, the

widths of the four individual hyperfine peaks are unequal because of incomplete averaging of the spectral anisotropy through molecular motion, and in addition the anisotropic data from the screening assay frozen solution spectra show that most samples contain more than one type of complex. Furthermore, the peaks from the individual 63,65Cu isotopes are not resolved from one another. Thus there are considerable Dimethyl sulfoxide uncertainties in deriving isotropic parameters from the X-band fluid solution spectra, and these spectra were only able to be analysed by using the parameters obtained from the frozen solution spectra (Table 1) with partial motional averaging. Since the frozen solution spectra provide no information on the relative signs of A// and A⊥, simulations were performed with the A// and A⊥ values having the same and opposite signs. However, only the use of the same signs reproduced the experimental spectra. The copper hyperfine peaks are much better resolved in the fluid solution spectra recorded at S-band frequencies (Fig. 4 and Fig. 5). The magnitudes of the Aiso values derived from these spectra (Table 1) show clearly that A// and A⊥ must have the same signs in Complexes II and III with both the Cu/GA and Cu/EGCG systems, thus providing support for the X-band analyses. Simulated parameters for the spectra of all Cu complexes detected in fluid and frozen solutions are reported in Table 1, the values of Aiso being assumed to be equal to (A// + 2A⊥)/3 for the X-band spectra.