[RASMB] Imidazole inquiry

[Liyana Binti Azmi]

Hi all,

My name is Liyana Azmi and I am a masters student from University of Glasgow. Currently I am working on a project that requires me to characterise a regulatory protein of E.coli called YhaJ. During the characterisation process I have used AUC to do both sedimentation velocity and equilibrium experiments to find out the molecular weight and to know the sample species in solution. When I came about analysing my results, I had to calculate for the buffer density and viscosity used in my experiment; and in my case, I used a lot of imidazole to keep my proteins in solution (250mM imidazole). However, using SEDNTERP, there are no imidazole within the range of buffer composition. The closest density of imidazole I could get to was the density at 20C. 

Besides that, when I analysed my data on I found that my protein has some non-participating species. from the c(s) and molecular weight I have obtained, I am pretty sure that my protein exists as a tetramer that is of one singular species. I think my non participating species could be imidazole, since I did not insert the density of the imidazole in the buffer density. Is that possible? I'm very new in AUC and the whole concept seems a bit alien to me.. any advice on how I should approach my data would be really helpful. Thanks!

Best regards,
Liyana