Stokes shift phycobiliproteins

Phycobiliproteins, such as phycocyanin and phycoerythrin, are members of a family of fluorescent accessory, nonchlorophyll-based pigments found in cyanobacteria and eukaryotic algae. The phycobiliproteins have characteristic broad absorption profiles spanning 450-600 nm, emissions ranging 570-660 nm, and small stokes shifts see Fig. 3. The major structural subunits, phycoerythrobilin (PEB) or phycocyanobilin... 

A third and relatively new application of FRET is the generation of new compound dyes with spectral characteristics that combine the best of both dyes. The idea is to attach covalently a donor and acceptor together in close proximity to one another. In the simplest case, where the absorption or emission properties of the individual dyes do not change, the absorption characteristic of the compound dye is the sum of the two individual dyes. At the same time, the emission is dominated by the acceptor since almost all of the energy absorbed by the donor is transferred to the acceptor. This results in dyes having potentially large Stokes shifts (the sum of the donor and acceptor Stokes shifts) and excellent quantum yields. So far, this work has mainly been applied to phycobiliproteins and DNA dyes. " ... 

Other dyes such as dansyl and AEDANS are popular donors in protein studies, in part because of the relatively long lifetimes (13-20 nsec), large (150 nm) Stokes shifts, and reasonable quantum yields (0.1-0.5). If steric hindrance is not a problem and a large-sized donor or acceptor can be used, the multichromophoric phycobiliproteins (molecular weight of 104,000 for B- or R-phycoerythrin 240,000 for allophycocyanin) make excellent donors or acceptors, having extinction coefficients which can exceed... 

---