> Dear All:
>
> Recently I was approached by a fellow researcher about a collaboration
> where he wants me to measure the T1 of water in leaves of rice plant. In
> the literature, the measured T1 has been used to identify the "mobility"
> of water in the leaf which is related to the "availability" of water to the
> plant. For example, it has been shown that the T1 can be related to
> droughts or that in drought resistant variety it has some unique signature.
>
> Anyway, before trying to perform the actual experiment with leaves, I
> tried to measure the T1 value of a 90%H20/10%D20 solution, and to my
> surprise, in a standard inverse-recovery experiment, I observed a
> sigmoidal rise of water signal as a function of Tau (instead of an exponential
> growth). I feel that since I am dealing with a huge solvent peak,
> either some special trick is needed to measure the T1 or that there is
> something special about H20.
>
> I looked around for an answer but failed. Would one of you be able to
> shed some light so that I can finish this simple experiment?
>
> best regards,
>
> Gautam Basu
I think you will only see a simple exponential if there is only one relaxation
pathway and only one relaxing species. In a 90%H20/10%D20 solution you will have
~80% H2O and ~10% HDO (a statistical mixture) and if you did not degas there are
at least two relaxation pathways. As I understand it, it gets worse with
biological preparations. In "An evaluation of the hydration of lysosyme by an
NMR titration method", By G.D. Fullerton et al. Biochem. Biophys. Acta 8969
(1986) p230-246, the authors observed several different types of bound water and
multiexpontial decays.
David Naugler
Institute of Molecular Biology and Biochemistry
Simon Fraser University