Hi, If the local tm diffusion model is selected over the spherical, oblate and prolate spheroids, and ellipsoid then this could be an indication that your molecule doesn't diffuse as a single globular unit. A solution to this could be the use of hybrid models whereby you, for example, describe two domains using two different diffusion tensors. Another hybrid would be to describe the system using one of the diffusion models for most of the spins and then applying the local tm model to those spins which you think would not be part of the core. Unfortunately I have not been able to publish this work as of yet. However these hybrid models are described in my PhD thesis located at http://eprints.infodiv.unimelb.edu.au/archive/00002799/ Another explanation could be inconsistencies between the relaxation data sets. This can happen because of sample heating differences between experiments and spectrometers. To overcome these problems, I use methanol temperature calibration for all experiments, compensatory blocks of CPMG pulses in the R2 experiment so that each scan has equal amounts of heating and single scan interleaving for ultimate temperature normalisation. Another possible factor could be if two or more samples are used to collect the data and the protein concentration is not identical. Proteins bumping into each other in the NMR tube is an important factor affecting the global tumbling of the molecule and changes in the sample concentration can affect the global tumbling. Cheers, Edward On 6/1/07, Neil Syme <bmbnrs@xxxxxxxxxxx> wrote:
Using the 'full_analysis.py' script I find that after the 'final' run, the diffusion model selected is the local_tm. I have tried removing those residues with particularly high or low local_tm values but still get the same result. Does anyone ahve any idea why this may be the case? Thanks, Neil --------------------------------------- Neil R. Syme Institute for Molecular and Cellular Biology Astbury Building University of Leeds Leeds LS2 9JT Email: N.R.Syme04@xxxxxxxxxxx Tel: +44 (0) 1133431937 --------------------------------------- _______________________________________________ relax (http://nmr-relax.com) This is the relax-users mailing list relax-users@xxxxxxx To unsubscribe from this list, get a password reminder, or change your subscription options, visit the list information page at https://mail.gna.org/listinfo/relax-users