The above descriptions can be applied, with some precautions, to membrane-bound RCs samples, in which multiple scattering effects occur (Goushcha et al. 2004). We will use Method 2 to make an approximate estimation of the excitation parameters for membrane samples. Results Rate constants

obtained from flash activated kinetics The charge recombination kinetics following a single actinic GDC-0449 clinical trial flash applied to dark-adapted samples are analyzed with the two-exponential decay function given by Eq. 1. Representative fitting results for isolated RCs are listed in Table 1. The relative amplitudes and time constants obtained from these results are used to calculate \( k^\prime_\textrec \) and are also shown in Table 1. The single exponential decay lifetimes of isolated RCs and IWP-2 cell line membranes after applying a single actinic flash are (assuming no structural SAR302503 nmr changes under our excitation conditions) τ s  = 0.84 s for RCs with LDAO, τ s  = 0.20 s for RCs with Triton X-100, τ s  = 4.59 s for membranes, τ s  = 4.69 s for membranes with myxothiazol, and τ s  = 4.33 s for membranes with myxothiazol and antimycin A (see Samples in Materials and methods section). These single exponential decay

lifetimes can be compared with the values of \( \tau_d = (k^\prime_\textrec )^ – 1 \) given in Table 1 for isolated RCs. Table 1 The fitting results for the single flash-activated, dark recovery kinetics of isolated RC samples Sample C 1 τ A , s C 2 τ B , s \( k^\prime_\textrec \), s−1 LDAO 0.36 0.28 (3.57) 0.64 1.16 (0.86) 1.18 Triton X-100 0.71 0.112 (9.1) 0.29 0.45 (2.23) 4.81 C 1 and C 2 are the normalized, relative amounts of the RCs that are Q B -depleted and Q B -occupied. τ A and τ B are the time constants for charge recombination. The values in parenthesis next to the τ A and τ B values denote the inverse of the time constants in s−1. \( k^\prime_\textrec \) is the effective

single charge recombination constant determined by using the single flash data (C 1, C 2, τ A , and τ B ) with Eq. 6 RC bleaching kinetics and resulting fits Figure 2 shows typical results of absorbance bleaching kinetics for RCs with Triton X-100 following a sudden increase of the actinic light intensity, starting in the dark, to nine different excitation Astemizole levels, I exp. The smooth lines show the results of a global fitting using all nine bleaching curves for each excitation level I exp. Note that both analysis methods (Method 1 and Method 2) provide excellent fitting results. For fitting experimental results to each model, the light intensity parameters are held fixed for each curve and all other parameters are shared and allowed to float. In the analysis, it is assumed that, within the 2-second time interval of applied illumination, the electron transfer rate constants do not change by light induced structural changes (Goushcha et al. 2003; Goushcha et al. 2004). Figure 3 shows typical bleaching kinetics for RCs with LDAO, and Fig.