This appears to occur especially above 25–30°C (Fig. 5a). A comparison of the relative amplitudes of the 1- and 2-ns components in dgd1 and WT) reveals that for WT the relative amplitude of the 2-ns component is slightly larger than that of the 1-ns component, indicating that the amounts of MC540 incorporated into the bilayer and located on the surface are almost equal (Fig. 5b, c). In contrast, for dgd1, the relative amplitude of the 1-ns component is significantly larger than that of the 2-ns component (Fig. 5b, c). If the two slow components originate from a broad distribution of lifetimes
(cf. Krumova et al. 2008a), then their weighted average lifetime is a more appropriate parameter to consider. As can be seen in Fig. 5d, at 7°C this average lifetime is shorter for dgd1 (1.35 ± 0.1 ns) than for WT (1.52 ± 0.01 ns). The average lifetime for both WT and dgd1 is decreasing with the increase selleckchem of temperature, but the average lifetime of dgd1 remains shorter at all temperatures between 7 and 35°C; at 45°C the two lifetimes become almost identical, about 1.1 ns. Electrochromic absorbance changes (ΔA515) in WT and dgd1 In order to test the membrane permeability, electrochromic absorbance change MK-4827 mouse (ΔA515) measurements were performed. On the time scale of the experiment, the rise of ΔA515, due to primary charge separations, is instantaneous. The initial amplitude of ΔA515
(for samples with identical Chl concentration) differs for WT and dgd1, as can be seen in Fig. 6a and b. At 25°C, the decay time of ΔA515 for the mutant (t 1/2 = 226 ± 15 ms) is essentially the same as for the WT (t 1/2 = 227 ± 19 ms). For the 35°C-treated sample, the decay of ΔA515 is significantly ever faster for the dgd1 mutant (Fig. 6b); the corresponding halftimes are 237 ± 16 ms for WT and 154 ± 19 ms for dgd1. No change in the decay rate was observed for the WT leaves LY2874455 cost exposed to the same temperature; only at 40°C, the decay becomes faster (t 1/2 = 36 ± 12 ms) for WT; at this latter
temperature no ΔA515 signal can be discerned for dgd1. Fig. 6 Typical electrochromic absorbance transients recorded at 515 nm (ΔA515), induced by saturating single-turnover flashes on detached WT (black trace) and dgd1 mutant (gray trace) leaves incubated in the dark for 10 min at 25°C (a) and 35°C (b) and subsequently measured at 25°C. The kinetic traces are obtained by averaging 64 transients with a repetition rate of 1 s−1. The corresponding decay halftimes for WT and dgd1 (average from five independent experiments and their corresponding standard errors) are also plotted in the figure Discussion In this article, we investigated the role of one of the major thylakoid lipids, DGDG on the global organization and thermal stability of the membranes. To this end, we used the Arabidopsis lipid mutant dgd1, with substantially decreased DGDG content (Dörmann et al.