I just had a talk on th eissue of surface mediated oligomerization with D. Pastré who directd the mentionned study. Here is what came out from the discussion:

Mica surfaces are strongly negatively charged. Tubulin C-ter tail is as welll negatively charged. When divalent magnesium ions are present in the solution salt bridges can be made in between tubulin and the mica surface. These bridges have two effects: tubulin dimers are attracted to the surface and they are ABLE TO DIFFUSE on the surface. This leads to the formation of very long oligomers, even if the bulk concentration is very weak (80 nM).

In our case, we use glow discharged carbon surface. When dimers touch this surface, they are likely to be stuck, and UNABLE TO DIFFUSE. In this case, the population of oligomers we see on the surface correspond to the poputlation in the bulk, in agreement with our FCCS measurements. We are thus confident that the oligomerization we mesure is not due to surface effects. We agree however that the measure we made of Elong needs to be confirmed by different technics.

Julien Mozziconacci.