The histogram of vertical localization coordinates was calculated for each focal adhesion region. The local z=0 nm level was defined by nonspecific fluorescence from the media that adsorbed to the coverglass, and was used to account for sample tilt. The centre positions (zcentre) and width parameter (σvert) were calculated from Gaussian fits or from the first and second moment of the distributions for non-Gaussian cases such as actin and α-actinin. For more detailed information see Methods and Supplementary Information.
Full Methods and any associated references are available in the online version of the paper at www.nature.com/nature.