Well that looks pretty real then. You might have wrong concentrations in one or the other experiment perhaps hence the difference.
Jürgen On Feb 20, 2013, at 5:45 PM, xianchi dong wrote: Thanks a lot for the kind reply. I used CM5 chip at pH 7.4. I am not quite sure about the PI of my protein but I have different truncations of my protein which behaved similarly. I can fit my data quite good with the Chi2 around 1 and Rmax 150. The kon is about 10e4 and the KD is around 0.2 nM. The concentration of analytes I used was from 100 nM to 5 nM. I used a control buffer which can disrupt the binding. In that buffer, no binding was observed. I also used fluorescence anisotropy to measure the Ki of the interaction which showed a 1 nM binding compared with the 0.2 nM binding in the SPR assay. On Wed, Feb 20, 2013 at 12:03 PM, xianchi dong <dongxian...@gmail.com<mailto:dongxian...@gmail.com>> wrote: Dear all, Recently I have measure a set of kinetic data of a receptor ligand interaction using BIAcore 3000. To my surprise, the dissociation rate is very low (~ 10e-6). During the measurement, I use a long dissociation time (2 hours) .I repeat several time which give very similar results. So I am wondering if the BIAcore can measure such a low off-rate kinetic. What is the limitation of BIAcore? Any review about that? Thanks in advance. Xianchi Dong Research Fellow Children's Hospital Boston Harvard Medical School ...................... Jürgen Bosch Johns Hopkins University Bloomberg School of Public Health Department of Biochemistry & Molecular Biology Johns Hopkins Malaria Research Institute 615 North Wolfe Street, W8708 Baltimore, MD 21205 Office: +1-410-614-4742 Lab: +1-410-614-4894 Fax: +1-410-955-2926 http://lupo.jhsph.edu
