Dear friends,
When I am trying to get structures of some small molecules using NOESY peak integration, I found that the NOE cross peak for methylene -CH2- protons are sort of symmetrically dispersive instead of pure positive absorptive. In fact, integration of the peak gives a huge negative number, while I am expecting a big positive number. All the other NOEs are very good. I guess there is a problem with the experimental parameters, I am using Varian's standard NOESY sequence on INOVA-500, with 250ms or 100ms mixing time, 1.5 second recycle delay and precise 90 degree pulse. There is a gradient-90-gradient to randomize the spin at the beginning of the NOESY sequence. Does anyone know how to improve correct the -CH2- problem?
Thanks.
Wei Li
Received on Thu Jan 30 2003 - 15:28:53 MST