  Scanning fluorescence correlation spectroscopy (SFCS) with a scan path
perpendicular to the membrane plane was introduced to measure diffusion and
interactions of fluorescent components in free standing biomembranes. Using a
confocal laser scanning microscope (CLSM) the open detection volume is moved
laterally with kHz frequency through the membrane and the photon events are
continuously recorded and stored in a file. While the accessory hardware
requirements for a conventional CLSM are minimal, data evaluation can pose a
bottleneck. The photon events must be assigned to each scan, in which the
maximum signal intensities have to be detected, binned, and aligned between the
scans, in order to derive the membrane related intensity fluctuations of one
spot. Finally, this time-dependent signal must be correlated and evaluated by
well known FCS model functions. Here we provide two platform independent, open
source software tools (PyScanFCS and PyCorrFit) that allow to perform all of
these steps and to establish perpendicular SFCS in its one- or two-focus as
well as its single- or dual-colour modality.
