The hole widths were then extrapolated to Pt/A → 0 (as in Fig. 6a) at each burning wavelength λburn to obtain the homogeneous linewidth Γhom. The depths of the narrow, homogeneously broadened holes (of equal width) at a given wavelength is proportional to the number of BChl a molecules contributing to the k = 0 band at this wavelength. The dependence of the hole depth on λburn, thus, represents the distribution of the lowest k = 0 exciton state. The reason for the appearance of narrow holes in the red wing of the B850 band is that their

width is limited buy Citarinostat by the fluorescence lifetime of a few nanoseconds of the lowest k = 0 exciton state. In contrast, higher-lying k-states decay to lower-lying k-states in tens to hundreds of femtoseconds (Alden et al. 1997; Novoderezhkin et al. 1999, 2003; Sundström et al. 1999, and references therein), which correspond to homogeneous linewidths that are 4–5 orders of magnitude larger. They contribute to extremely broad and very shallow holes that disappear within the noise, as mentioned above. The hole depths of the narrow

holes burnt Emricasan cell line in the red wing of the B850 band of LH2 of Rb. sphaeroides (2.4.1, wt) are plotted as a function of burning wavelength in Fig. 9. They are well-fitted by a Gaussian curve with a width of ~190 cm−1 and a maximum of ~866.0 nm. We have interpreted these data as representing the spectral distribution of the lowest k = 0 exciton states. Fig. 9 Hole depth as a function of burning wavelength, for holes burnt in the red wing of the B850 band of Rb. sphaeroides (2.4.1, wt) at 1.2 K. The data were fitted with a Gaussian curve (hole-depth distribution) with a maximum at ~866.0 nm and a width of ~190 cm−1 (V. Koning and N Verhart, unpublished

results from our laboratory) PRKD3 In Fig. 10, the hole-depth (k = 0) distribution of Fig. 9 has been inserted into the B850 band. This was done by matching the red wing of the k = 0 distribution to that of the B850 excitation spectrum. The intensity of the hole-depth distribution was scaled in such a fashion that the two red wings overlap. The result yielded a relative area of k = 0 / B850 ~ 9.5% and an energy difference between the two bands, Δ(B850 – k = 0) ~ 176 cm−1 for Rb. sphaeroides (2.4.1, wt) (V. Koning and N. Verhart, unpublished results). Although the latter value is of the same order as that reported in the literature (~200 cm−1), no values for the relative area for Rb. sphaeroides have been published. Fig. 10 Excitation spectrum of the B850 band of Rb. sphaeroides (2.4.1, wt) at liquid-helium temperature with the hole-depth distribution from Fig. 9 (see also inset) built into it. The energy difference between the maxima of the B850 band and the hole-depth distribution is Δ(B850 − k = 0) ~ 176 cm−1.