Paper
The paper was also reviewed in Ryo's page .
[My comments]
Because they use ratio metric method, which depends on concentration ratio of YFP/CFP-actins, they did not do any quantification about the actual G/F-actin ratio. They could have done using FRAP(star et al., 2000).
It is surprising that the FRET efficiency in spine after a tetanus application is as high as that in jasplakinolide(actin polimerization stabilizer) condition. The concentration of G-actin in spines should be constant, given the rapid exchange rate of G-actin through spine neck (star et al., 2000). Thus, the G-actin signal also increases as spine grows, by a factor of r3 (r: spine radius). F-actin signal has to increase much more than this. This cannot be explained by the length change of F-actin, which probably increases signal only by factor of r. Thus, the large FRET change is probably due to increase of nucleation processes and so on.
