Fluorescent J-Aggregates and Their Biological Applications - Advanced Fluorescence Reporters in Chemistry and Biology - page 151

Fig. 9 Possible monomer packing structures in Cyan b iPr J-aggregate formed in the poly(dA)-

poly(dT) groove, built in HyperChem 6.03

absorption transitions are directed along the DNA axis and perpendicular to it [ 20 ],
according to Kasha prediction [ 12 ].
Summarizing, some of the organic dyes, particularly cyanines, are able to form
fluorescent aggregates on DNA. Comparing with the dye monomers bound to DNA,
the J-aggregates are more sensitive to the concentrations ratio and to DNA nucleo-
tides content. Though these structures can hardly be applied for the routine DNA
detection assays, they are rather interesting systems for special studies.

6 Proteins as the Templates for Aggregate Formation

Proteins in their native form are the globules, the structures of which (the so called
tertiary structure) strongly differ for different proteins. At the same time, on the
level of secondary structure only three major forms are realized, namely a -helix,

b -sheet, and random coil. As the two first mentioned forms are periodical, they

could possibly serve as the templates for the J-aggregate formation. Nevertheless,
there are only a few reports about the dye aggregates formed on proteins.