Parameters of ligand interactions with CYP3A4 determined by steady-state and time-resolved LRET^*.

<p>*Life-time measurements were performed at nearly-saturating ligand concentrations, which were equal to 100 µM, 2.5 µM, 50 µM and 100 µM for ANF, bromocriptine, cholesterol, and testosterone, respectively. The respective values of LRET efficiency (Δ<i>E_LT</i>) were calculated according to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0083898#pone.0083898.e002" target="_blank">Eq. 2</a> using the value of τ_d (lifetime in the absence of acceptor) equal to 234 µs (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0083898#pone.0083898.s004" target="_blank">Table S1</a>). In the case of steady state measurements, the change in LRET efficiency (Δ<i>E</i>) were calculated from the maximal relative change in the intensity of donor fluorescence found from the approximation of LRET titration curves with a combination of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0083898#pone.0083898.e004" target="_blank">Eq. 4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0083898#pone.0083898.e005" target="_blank">Eq. 5</a>. The values given in the table represent the averages of 3–7 individual measurements, and the ± values show the confidence interval calculated for <i>p</i> = 0.05. The values of the distance changes were considered significant if their confidence interval falls outside the −0.5 - +0.5 Å window. These values are emphasized in bold.</p>a<p>Not determined – in these cases the amplitude of the changes was too small to obtain a reliable estimate of the dissociation constant.