Accurate quantitation of water-amide proton exchange rates using the Phase-Modulated CLEAN chemical EXchange (CLEANEX-PM) approach with a Fast-HSQC (FHSQC) detection scheme

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Abstract

Measurement of exchange rates between water and NH protons by magnetization transfer methods is often complicated by artifacts, such as intramolecular NOEs, and/or TOCSY transfer from Cα protons coincident with the water frequency, or exchange-relayed NOEs from fast exchanging hydroxyl or amine protons. By applying the Phase-Modulated CLEAN chemical EXchange (CLEANEX-PM) spin-locking sequence, 135°(x) 120°(-x) 110°(x) 110°(-x) 120°(x) 135°(-x) during the mixing period, these artifacts can be eliminated, revealing an unambiguous water-NH exchange spectrum. In this paper, the CLEANEX-PM mixing scheme is combined with Fast-HSQC (FHSQC) detection and used to obtain accurate chemical exchange rates from the initial slope analysis for a sample of 15N labeled staphylococcal nuclease. The results are compared to rates obtained using Water EXchange filter (WEX) II-FHSQC, and spin-echo-filtered WEX II-FHSQC measurements, and clearly identify the spurious NOE contributions in the exchange system.

Original languageEnglish (US)
Pages (from-to)221-226
Number of pages6
JournalJournal of Biomolecular NMR
Volume11
Issue number2
DOIs
StatePublished - 1998

Keywords

  • CLEANEX-PM
  • Hydrogen exchange
  • NOE
  • Protein
  • Pulsed field gradients
  • Water

ASJC Scopus subject areas

  • Biochemistry
  • Spectroscopy

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