Linear dichroism and circular dichroism in photosynthesis research

Abstract

The efficiency of photosynthetic light energy conversion depends largely on the molecular architecture of the photosynthetic membranes. Linear-and circulardichroism (LD and CD) studies have contributed significantly to our knowledge of the molecular organization of pigment systems at different levels of complexity, in pigment-protein complexes, supercomplexes, and their macroassemblies, as well as in entire membranes and membrane systems. Many examples show that LD and CD data are in good agreement with structural data; hence, these spectroscopic tools serve as the basis for linking the structure of photosynthetic pigment-protein complexes to steady-state and time-resolved spectroscopy. They are also indispensable for identifying conformations and interactions in native environments, and for monitoring reorganizations during photosynthetic functions, and are important in characterizing reconstituted and artificially constructed systems. This educational review explains, in simple terms, the basic physical principles, and theory and practice of LD and CD spectroscopies and of some related quantities in the areas of differential polarization spectroscopy and microscopy.

Functional heterogeneity of the fucoxanthins and fucoxanthin-chlorophyll proteins in diatom cells revealed by their electrochromic response and fluorescence and linear dichroism spectra

“…Cells or thylakoid membranes, isolated from P. tricornutum or C. meneghiniana were oriented with the gel-squeezing method [22]. The samples were embedded in 5% polyacrylamide gel and the gel cube was squeezed to half the original width (M=2, where M is the squeezing factor).…”

Pigment Interactions in Light-harvesting Complex II in Different Molecular Environments

“…Aggregates are also readily distinguished by the excitonic CD spectra (21,22). The CD spectra report on small changes in the excitonic pigment-pigment interactions in the complexes (23), which are brought about by changes in the protein conformation or intermolecular interactions. When compared with the native thylakoid membranes, the CD spectra indicated that aggregated LHCII is structurally more similar to the native state despite the low fluorescence yield, and that detergent solubilization appeared to perturb the native structure (22).…”

Increased Thermostability of Thylakoid Membranes in Isoprene-Emitting Leaves Probed with Three Biophysical Techniques

“…temperature or pH. In plants, CD spectroscopy in the visible range originates from pigment-pigment interactions and hence is a valuable tool for probing the molecular architecture of the photosynthetic complexes and supercomplexes and their macroorganization in the membrane system (Garab, 1996;Garab and van Amerongen, 2009). CD can originate from different levels of complexity in the sample.…”