Re: [ccp4bb] metal-chelating affinity chromatography and FosCholine detergents

2010-07-15 Thread Eric Geertsma
Dear Pascal, be aware that fos-choline detergents are extremely efficient solubilizers of membrane proteins. We found that even partially aggregated membrane proteins could be solubilized with fos-choline 12, while this fraction did sediment using for example dodecylmaltoside (see e.g. fig5 and

Re: [ccp4bb] metal-chelating affinity chromatography and FosCholine detergents

2010-07-14 Thread Ho Leung Ng
Hi Pascal, I suspect the protein is aggregating in the presence of FosCholine. In addition to the suggestions made by others, you can also try changing the salt concentration or including additives like glycerol in your FosCholine buffer. This can make an enormous difference in the stability

Re: [ccp4bb] metal-chelating affinity chromatography and FosCholine detergents

2010-07-13 Thread Daniel Picot
A crude purification prior loading the metal-chelating column (like ion exchange chromatography) can help and speed up the binding to the column (remark not specific to Fos-cholin). Fos-choline is, contrary to popular belief, a quite harsh detergent and this may affect the purification yield a

Re: [ccp4bb] metal-chelating affinity chromatography and FosCholine detergents

2010-07-12 Thread Poul Nissen
Dear Pascal, There can be a number of reasons for this. Maybe fos-cholines are not very well suited for your membrane proteins of interest? - have you checked for activity or aggregation and compared to other detergents? If the detergent is optimal you may consider moving/extending the tag or c

[ccp4bb] metal-chelating affinity chromatography and FosCholine detergents

2010-07-12 Thread Pascal Egea
Dear All, I apologize for the not strictly crystallography-related query. I am currently purifying several membrane proteins solubilized in fos-cholines detergents and I consistently observe a significant loss of protein at the binding step (done in absence of imidazole). Has anyone else experienc