Der Einsatz von Relaxationserhöhungen in einer paramagnetischen Umgebung zur Proteinstrukturbestimmung mit NMR‐Spektroskopie

Abstract

Ein Mehr an Informationen: Relaxationserhöhungen durch eine inerte paramagnetische Umgebung (PREs) wurden zusammen mit einem eingegrenzten NOE‐Datensatz in einem modellfreien Strukturbestimmungsverfahren genutzt. Strukturen für zwei Proteine – Ubiquitin (8 kDa) und das Maltose‐bindende Protein (42 kDa; im Komplex mit β‐Cyclodextrin) – wurden mithilfe von PREs und NOEs zwischen austauschenden Protonen ermittelt.

Longitudinal Relaxation Enhancement in 1H NMR Spectroscopy of Tissue Metabolites via Spectrally Selective Excitation

“…[6] Effective T 1 values can also be modified by extramolecular factors including exchanges between labile targeted protons and water, [7] or by the presence of paramagnetic agents. [8,9] Of relevance to this study is the fact that the "apparent" T 1 measured for a particular moiety, may also depend on the mode by which its NMR resonance is interrogated. [10] During the last decade numerous instances of such excitation-dependent longitudinal relaxation enhancement effects have been demonstrated in the field of biomolecular solution-state NMR spectroscopy, and have been exploited to achieve substantial improvements in the signal-to-noise ratio (SNR) achievable per unit time in protein and nucleic acid NMR experiments.…”

Studying the Structure and Dynamics of Biomolecules by Using Soluble Paramagnetic Probes

“…b) The residues for which R 1 enhancements are shown in a) are labelled. All available experimental PREs are mapped onto the structure of MBP (red=low PRE, blue=high PRE) 4b…”

“…in case of a planar surface). Although an analytical expression cannot be obtained for a molecule of arbitrary shape, a minimal boundary for the distance to the surface can be obtained 4b…”

“…in which θ and φ are the angles in the spherical coordinate system, r is the distance between the nucleus and the paramagnetic centre, d is the sum of the distance of the nucleus from the surface of the sphere and the radius of the sphere, and r para is the hydrodynamic radius of the paramagnetic compound. Although the sPRE drops off rapidly with increasing distance, much larger distances (>15 Å) can be extracted than those measurable by more conventionally used 1 H– 1 H NOE 4b. Because the sPRE scales linearly with the concentration of the paramagnetic probe, higher distances can be resolved with higher concentrations of the probe and are, in principle, only bound by the solubility limit of the probe itself.…”

“…The constant a j accounts for the combination of all terms in either Equation (3) or (4), depending on the type of relaxation [Eq. (8)]:4b …”