Exciton-coupled circular dichroism

Exciton coupled circular dichroism (ECCD) spectra. 139... 

Cm profiles from structural studies by circular dichroism or fluorescence spectroscopy can be readily validated by comparison with results from function. Several labeling methods exist to study self-assembly under meaningful high-dilution conditions (FRET [6] ECCD, exciton-coupled circular dichroism [67]). Validated Cm profiles from structural studies or from other functions such as catalysis can be used to dissect self-assembly in water with self-assembly in the bilayer membrane (Fig. 11.13B, a vs b) [21]. 

Exciton-coupled circular dichroism (ECCD) spectroscopy was performed on the Aib-Stb-D peptide to fiirther substantiate the interaction between the methyl stilbene side-chains, which was observed via PL experiments. The interaction between the excited state of chromophores in a chiral environment causes split Cotton effects upon absorption of circularly polarized light by the chromophores (29, 30). It can be observed from Figure 7 that Aib-Stb-D exhibits a split CD Cotton effect presumably because of the chiral presentation of the methyl stilbene molecules on the same side of the a-helical peptide the asymmetric nature of the split observed may be due to some other electronic transitions or of additional background ellipticity, as has been observed in other systems (29, 31). The ECCD results confirm the close proximity of the methyl stilbene side chains mediated by the peptide backbone, which permits interaction between the side-chains in the excited state. 

Nehira T, Parish CA, Jockusch S, et al. (1999) Fluorescence-detected exciton-coupled circular dichroism scope and limitation in structural studies of organic molecules. Journal of the American Chemical Society 121 8681-8691. 

Circular dichroic spectroscopy (CD) is a powerful method for determining the absolute configurations and confirmations of chiral molecules. In particular, the exciton-coupled circular dichroism arising from through-space chromophore chromophore interac tions, called exciton coupling, is one of the most... 

K. Nakanishi and N. Harada, Circular Dichroism Spectroscopy Exciton Coupling in Organic Stereochemistry, University Science Books, Mill Vallqr, California, 1983 D. N. Kirk, Tetrahedron 42 777 (1986). 

Harada, N. Nakanishi, K. Circular Dichroism Spectroscopy—Exciton Coupling Method in Organic Stereochemistry. Oxford University Press, Oxford, 1983. 

Coupled oscillator models are extensions to the simple models developed for electronic circular dichroism. They are well known under the name exciton theory (see e.g. Harada and Nakanishi, 1972). These models, extended to vibrational transitions, describe the coupling of pairs of electric dipole transition moments. They predict equal amounts of positive and negative VCD intensity ... 

Tanaka, J., Ozeki-Minakata, K., Ogura, F., and Nakagawa, M. Absolute configuration of a coupled chromophore system by exciton analysis of circular dichroism. Nature, Phys. Set. (London) 241, 22-23 (1973). 

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