Infoscience

Journal article

Measurement of proton relaxation rates in proteins

Five different types of expt. are described which make it possible to measure various relaxation rates of selected protons in crowded spectra of macromols. such as proteins: longitudinal spin-lattice relaxation rates rt = 1/T1, transverse relaxation rates rt = 1/T2 measured under conditions of free precession, transverse relaxation rates rLOCKt = 1/T1r measured under conditions of spin-locking, and transverse relaxation rates rDQC = 1/T2DQC and rZQC = 1/T2ZQC of double- and zero-quantum coherences. The surprisingly large discrepancy between the transverse rates rt and rLOCKt is discussed in detail. To sep. overlapping proton signals, the exptl. schemes involve one or several magnetization transfer steps, using a doubly selective homonuclear Hartmann-Hahn method. Numerous variants of the basic ideas can be conceived, depending on the extent of signal overlap and on the topol. of the networks of scalar couplings. Applications are shown to He and Hd of Tyr23, to Ha, Hb and Hb' of Cys30, and to Ha and Hb of Ala24 in bovine pancreatic trypsin inhibitor (BPTI). [on SciFinder (R)]

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