Multiple simultaneous distance determinations: Application of rotational echo double resonance nuclear magnetic resonance to IS2 spin networks

Abstract

Rotational Echo DOuble Resonance (REDOR) NMR is an oft-demonstrated tool for measuring distance between isolated IS spin pairs. Its application to more complex ISn spin networks (n>1), however, is rare, as in these systems the interpretation of the results is model-dependent–while it is precisely the measurement of multiple distances which is required for molecular structure elucidation. Recently, Θ-REDOR was introduced and was shown to improve interpretability at the cost of signal intensity. In this paper we analyze generalizations to the REDOR pulse sequence, and present a new experimental procedure which allows for simultaneous distance determinations in larger spin systems with improved signal intensity. Experimental data are presented for the IS2 spin system glycine-C213-N15.

l19F/29Si Rotational-Echo Double-Resonance and Heteronuclear Spin Counting under Fast Magic-Angle Spinning in Fluoride-Containing Octadecasil

“…However, it is unclear whether reliable distances could be determined if the geometry of the spin system was completely unknown. The y-REDOR technique [23] and its generalizations [24,25] have been recently developed for measuring the n S À I k dipolar couplings without the additional complications arising from the orientational dependencies between the n dipolar tensors. The knowledge of the spin multiplicity n is nevertheless a prerequisite for extracting the coupling constants [24,25].…”

“…The y-REDOR technique [23] and its generalizations [24,25] have been recently developed for measuring the n S À I k dipolar couplings without the additional complications arising from the orientational dependencies between the n dipolar tensors. The knowledge of the spin multiplicity n is nevertheless a prerequisite for extracting the coupling constants [24,25]. In this respect, it is remarked that the heteronuclear spin counting version of y-REDOR introduced by Cull et al [22] yields in principle the number n of spins I to which each spin S is coupled.…”

“…Moreover, the analysis of the REDOR data in terms of isolated spin pairs cannot be justified by the presence of dipolar oscillations since an oscillatory behavior of the REDOR dephasing curve may also be observed for multispin systems [18]. Hence, new REDOR-based techniques (so-called y-REDOR sequences) have been introduced for determining the number n of spins I dipolar coupled to each spin S [22] and to disentangle the n independent IS dipolar couplings [23][24][25]. Extension of REDOR to the multiple quantum dimension [20] and the frequency-selective REDOR (FSR) [26] technique also show great promise for measuring distances in the presence of complicated spin groupings.…”

Revealing the Configuration and Crystal Packing of Organic Compounds by Solid‐State NMR Spectroscopy: Methoxycarbonylurea, a Case Study

“…If the individual couplings are sufficiently strong this evaluation can be solved by the so-called REDOR transform. [18,19] Alternatively a full simulation of the experimental spin system can be performed [20][21][22] or specialized REDOR sequences like REDOR 3D, [23] FDR-REDOR, [24,25] q-REDOR, [26] or MS REDOR [27] can be employed, which however cause substantially longer measuring times.…”

Peptide Torsion Angle Measurements: Effects of Nondilute Spin Pairs on Carbon-Observed, Deuterium-Dephased PM5-REDOR

“…Four different nuclei can be observed, providing complementary spectroscopic information. The presence of multiple spin pairs can be problematic and complicates analyses, although new experimental procedures were recently developed toward multiple and simultaneous REDOR distance measurements (24,25). Unexpected or unavoidable neighboring spin interactions may occur in unordered, nondilute samples or in labeled proteins, particularly if the folded structure is not known.…”