NMR relaxation by intermolecular and intramolecular dipolar interactions in small molecules round to an enzyme

G. Navon*, A. Lanir

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

NMR relaxation times T1 and T2 and their temperature dependence were measured for sulfonamide inhibitors and acetate ion specifically bound to bovine carbonic anhydrase. Frequency dependence of T1 indicated a dipolar relaxation mechanism rather than a chemical shift dependent mechanism. Both T1 T2 ratios and frequency dependences indicated that the tumbling correlation time of the aromatic ring protons of the sulfonamide inhibitors is similar to that of the whole protein with no independent motion. Moreover, it was concluded that the major part of their dipolar interaction is due to an intermolecular interaction with the protein protons. Methyl groups were found to have a faster motion. This motion is discussed in terms of Woessner's theory [J. Chem. Phys.36, 1 (1962)]. The methyl groups in N1-acetylsulfanilamide and acetate ion have an isotropic random motion faster than that of the protein. The methyl group of p-toluenesulfonamide was found to undergo an anisotropic motion composed of fast rotation about the threefold axis and a slower motion of this axis together with the protein.

Original languageEnglish
Pages (from-to)144-151
Number of pages8
JournalJournal of Magnetic Resonance (1969)
Volume8
Issue number2
DOIs
StatePublished - Oct 1972

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