TOCSY of peptide in micelle
 

TOCSY of peptide in micelle

Hi,

I am a PhD student starting in NMR and I have two questions.

• I have a problem with a TOCSY and natural abundance 15N HSQC of a peptide in deuterated micelle. I have only a few amino acid that present all the crosspeaks in the TOCSY and these amino acid the same, are the only one present in the 15N HSQC. The two other third of the peptide amino acid have very low or absent peaks. The chemical shift of this amino acid are closely relative to a random coil conformation and the two other third are in alpha helical structure are not present. My hypothesis is that the alpha helical part of the peptide is much more in contact with the micelle and the 2 % of non deuterated proton remaining faster the relaxation and result in low peaks.If you have already had this problem do you think that if I increase the temperature or increase the number of scan will help me to see these missing peaks. Or do you think that there is a slow J coupling in this kind of sample and I had to test something else, because the NOESY spctrum is really good.

-In the NOESY spectrum I have noe crosspeaks between the NH and the H of the water in this one third of non structurated region of the peptide, and only in this region. Is it usual to have this kind of really strong NOE in disorderd region or is this disordered region slowing enough the molecule of water that NOE can appears according the acquistion time. Because this non structurated part could be the aggregating region of this peptide.

Best regardsPaul



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