Line broadening in nmr

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Hello can some body help me in understanding the line broadening effect in NMR? I am working with protein and small molecules and I observed severe broadening at a protein to ligand ratio 1:20. I am pretty sure that its not aggregation since i have the free ligand spectrum without the protein which didnt showed any broadening effect.

Hope somebody will guide me..

asked Oct 04 '11 at 03:45

fatima A
1

5 Answers:

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0	This is a massive topic. Maybe the ligand binds the protein and you get exchange broadening? You should consult the literature on fragment based drug discovery by NMR (or 'SAR-by-NMR'). link answered Oct 06 '11 at 09:28 Paul Driscoll 81

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I have seen in 1H NMR the broadening of the ligands. We basically use ligand based techniques for the binding study. I do know that this compounds binds to the protein which is confirmed by STD NMR.But what i dont understand is the broadening effect at 1:20 ratio of protein to ligand.

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answered Oct 06 '11 at 12:14

fatima A
1

0	Is this an IDP? If so broadening in 1H is common. You might try some 13C detected experiments to take advantage of the better chemical shift dispersion if you have the means to do so. link answered Oct 09 '11 at 15:04 bernie o'hare 111

could you please tell to us how much concentration of protein and drug u r taking ? and buffer conditions ?

I am not sure but I am suspecting following property might be the reasons

paramagnetic impurity concentration or viscosity of the sample increasing with ligand concentration .
ligand unspecified binding to protein .
because of ligand highly basic or acidic nature effects on sample condition .
At higher concentration of ligand ( if u taken it in salt conditions ) it dissipates the radio frequency pulse.

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answered Oct 11 '11 at 09:50

sri
71

updated Oct 12 '11 at 00:52

Its not IDP and i also dont think the effect is due to paramagnetic impurity.. Because i have another anologue of this compound which doesnt show any broadening effect at the same sample conditions. We do screen lot of compounds and none other than this compound showed any effect like this. So its not an effect due to buffer conditions. What i really want to know is whether line broadening effect at 1:20 ratio is usual? Because in literature people do reported about line broadening effect but at lower protein to ligand ratio say 1:2 or even 1:10.

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answered Oct 12 '11 at 06:30

fatima A
1

Hello Fatima, could you please use comments to follow up. This forum works a little differently compared to others - here we just ask and answer questions, this way it is much easier to maintain the content readable. - Evgeny Fadeev (Oct 12 '11 at 07:25)

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Asked: Oct 04 '11 at 03:45

Seen: 8,888 times

Last updated: Oct 12 '11 at 07:25

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