2006, 2007). An important application of UV-CD is the determination of the secondary structures of proteins, based on semi-empirical theoretical models. The characteristic this website CD arises by excitonic interactions, which depend in a characteristic way on the arrangement of the amino acid residues (Van Holde et al. 1998). Visible and UV-CD data can provide complementary

information. Surprisingly, large differences have been revealed between the sensitivity of the complexes—against detergent and organic solvents, and heat and light treatments—when monitored with CD in the visible and in the far UV regions, i.e., when fingerprinting for the pigment interactions and the secondary structure of the proteins, respectively (Büchel and Garab 1998; Wang et al. 1999). In scattering materials, dichroism can be measured via, e.g., FDLD (fluorescence detected LD), provided that the fluorescence is proportional to the absorbance (or follows a known dependence on it). FDLD can also be used in laser scanning microscopy, where it offers the convenience of confocal imaging (Steinbach et al. 2008). In general, laser scanning

microscopy (LSM) combined with differential polarization (DP) techniques, similar to the one in dichrographs are suitable to detect microscopic LD or the DR of the emission, or other DP features. Earlier, DP microscopy, using scanning stage and EGFR inhibitor transmission confocality, was used for LD and CD imaging of chloroplasts (Finzi et al. 1989). Recently, a DP-LSM was employed to reveal the strongly inhomogeneous birefringence of magnetically aligned chloroplasts (Garab et al. 2005). DP-LSMs hold the promise to map, in 2D and 3D, the anisotropic features in whole organelles and intact organisms. Acknowledgments The authors thank Milán Szabó, Gábor Steinbach, and Cor Wolfs for their help with the figures. This study has been supported in part by a grant from the Hungarian Fund for Basic Research (OTKA K 63252). We thank Govindjee for editing this manuscript. Open Access This article is distributed

under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) Phosphatidylinositol diacylglycerol-lyase and source are credited. Electronic supplementary material Below is the link to the electronic supplementary material. Fig. S1 Illustration of the alignment of disc-shaped particles (or membranes) and geometry for the calculation of the orientation angle of the transition dipole with respect to the main axis of the disc. In Panel A, the disc-like pigment–protein complexes are oriented randomly in a sample. One of them is magnified and shows 7 BChl a molecules with, in all the cases, the Q y transition dipole moment (represented as a double-headed arrow) along the Y-axis of the pigment.