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. 2009 Oct 1;106(42):17741–17746. doi: 10.1073/pnas.0905177106

Fig. 3.

Fig. 3.

Millisecond-intensity fluctuations due to FRET are observed for T324C and not for A215C. ATP concentration: 2 mM. (A) Autocorrelation of the “cover neck bundle” donor fluorescence intensity time trace of Fig. 2A (T324C). Shown is a fit (red curve) of the data with Eq. 2, consisting of a Gaussian (transit through confocal spot) and an exponential (FRET) component. The FRET component has an amplitude, A, of 0.22 ± 0.01 and a decay time, TFRET, of 2.5 ± 0.3 ms. (B) Cross-correlation of donor and acceptor intensity time traces of the same T324C event. The FRET-related correlation decay has an amplitude of −0.20 ± 0.01 and a decay time of 3.6 ± 0.6 ms. (C) Autocorrelation of the fluorescence intensity time trace of the A215C event of Fig. 2D. No decay of the autocorrelation on the approximate ms timescale can be discerned. (D) Cross-correlation of donor and acceptor intensity time traces of the same A215C event. No decay of the correlation is observed on the approximate ms timescale, indicating that no fluctuations occur due to changes in FRET.