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Direct and reverse titrations to resolve interaction mechanisms

Goal of this section is to present cases how line shapes for different models will appear in direct titrations: L(titrant)  to R(NMR-observable); as well as in reverse titrations:  R(unlabeled titrant) to L(NMR-observable). I want to explore opportunities to tell apart different mechanisms, which otherwise produce very similar line shapes.

We will consider models that may be alternatives of each other:

I will consider different combinations of exchange regimes. They are not entirely distinct and better be thought of representation of a continuum of conditions. I want to observe general trends and formulate some recipes on how to analyze these systems.

Additional note: the choice of chemical shifts for species is arbitrary. I only try to follow general relations between Kex and dw but it is not always unambiguous.

Contents

• Tight, slow-off binding, slow isomerization.
  This is the case when all processes are very slow so minor peaks of alternative conformations may be observed.

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• Tight, slow-off binding, intermediate isomerization
  no minor peaks are observed any more. Dependence of apparent 2-site Kd on dw is observed for U_R model.
  Redo with many more points near equivalence region

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• Tight, slow-off binding, fast isomerization
  No hope. Binding is too tight, isomerization - too fast.
  Redo with many more points near equivalence region

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• Intermediate binding , slow isomerization

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• Intermediate binding , intermediate isomerization

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• Intermediate binding , fast isomerization

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• Weak, fast-off binding , slow isomerization

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• Weak, fast-off binding , intermediate isomerization

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• Weak, fast-off binding , fast isomerization

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• Conclusions

Conclusions

unfinished

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