Paper (FRET)
P.G. Allen (2003) "Actin filament uncapping localizes to ruffling lamellae and rocketing vesicles"
Nature Cell Biology 5, 972 - 979
Capping and uncapping of both ends of actin filaments are critical for regulation of actin elongation. Allen visualized the dynamics of binding between QSY-labeled gelsolin, one of severing and capping protein, and Alexa-488-labeled actin filaments using FqRET techniques. QSY is a chromophore, and thus, it acts as a quencher of Alexa-488-actin. Ratio metric between fluorescence from Alexa-488-actin and rhodamin-actin gives the capping dynamics.
[My comments] The signal is surprisingly large, considering that one gelsolin can bind to only one filament which containes at least tens of monomers (1 turn = 26 monomers=74 nm). Probably the quenching efficiency of the actin monomer bound to gelsolin-QSY is close to 100%, due to the large absorbance of QSY (90,000) and the good spectrum overlap between QSY-absorption and ALexa-488 emission (there is no spectrum-separation problems which is a common problem in usual FRET experiments). This technique might be applicable to see mechanisms underlie spine-turnover in neurons.
