Comments |
Supplementary Text 2 p.24 2nd paragraph:"Transport of signal molecules-Consider a cell with no signal molecules exposed to a medium with a large signal concentration c0. If, the signal diffuses across the cell membrane by free diffusion with a transport rate constant of D, the rate of accumulation of intracellular signal concentration (ci) can be described as [dci/dct]=D(c0-ci). If the signal concentration in the medium is sufficiently large, the time (te) for ci to reach equilibrium value c0, is ~1/D. From similar measurements of freely diffusing AHLs by Kaplan et al (primary source), D=1/20 s^-1 = 180 hr^-1 (Ignoring signal degradation for such short observation periods) as the upper limit for free diffusion signal transport." |