Two-dimensional NMR lineshape analysis of single, multiple, zero and double quantum correlation experiments

Abstract

NMR spectroscopy provides a powerful approach for the characterisation of chemical exchange and molecular interactions by analysis of series of experiments acquired over the course of a titration measurement. The appearance of NMR resonances undergoing chemical exchange depends on the frequency difference relative to the rate of exchange, and in the case of one-dimensional experiments chemical exchange regimes are well established and well known. However, two-dimensional experiments present additional complexity, as at least one additional frequency difference must be considered. Here we provide a systematic classification of chemical exchange regimes in two-dimensional NMR spectra. We highlight important differences between exchange in HSQC and HMQC experiments, that on a practical level result in more severe exchange broadening in HMQC spectra, but show that complementary alternatives to the HMQC are available in the form of HZQC and HDQC experiments. We present the longitudinal relaxation optimised SOFAST-H(Z/D)QC experiment for the simultaneous acquisition of sensitivity-enhanced HZQC and HDQC spectra, and the longitudinal and transverse relaxation optimised BEST-ZQ-TROSY for analysis of large molecular weight systems. We describe the application of these experiments to the characterisation of the interaction between the Hsp90 N-terminal domain and a small molecule ligand, and show that the independent analysis of HSQC, HMQC, HZQC and HDQC experiments provides improved confidence in the fitted dissociation constant and dissociation rate. Joint analysis of such data may provide improved sensitivity to detect and analyse more complex multi-state interaction mechanisms such as induced fit or conformational selection.

High-resolution ex vivo NMR spectroscopy of human Z α1-antitrypsin

“…The progressive changes in chemical shift observed between resonances in M, Z and ligand-bound AAT (Fig. 7a) also indicate that the rate of exchange between native and intermediate states, k ex , must be much greater than the frequency difference between the states, Δω = γB 0 Δδ, where B 0 is the magnetic field strength and γ is the gyromagnetic ratio of the observed nucleus 53 . As the largest observed frequency difference is Δω = 2250 s −1 for L288 δ1…”

Super-Resolution NMR Spectroscopy using the Intersection of Non-Redundant Information on Resonance Groups

“…Additionally, the incorporation of Rex terms in the SQ, ZQ and ZQ transitions would give additional information on the microsecond-to-millisecond dynamics of the system. 14 Third, our application of INIR spectroscopy could be extended to higher dimensional experiments, such as HNCO, HNCA, HNCOCA experiments. 31 An INIR HNCO 3D, which would require 2-4 times the experiment time to collect, could be used to further resolve spins in a 3D at low field.…”

“…The d HNHA 2 constant is fit as an average molecular parameter (discussed below), even though its value is expected to vary slightly as a function of the ϕ torsion angle. The SQ, ZQ and DQ transitions may also have contributions from chemical exchange, as discussed previously, 14 and these are not modeled in this study.…”

A Modernized View of Coherence Pathways Applied to Magnetic Resonance Experiments in Unstable, Inhomogeneous Fields

“…19, an improvement is seen in the early and latter points of the inversion recovery curve, in the imaginary component for the former and in the real component of the later, thus indicating that the alignment is able to provide a better fit to the model Eq. (28) DCCT map provides both error bars (from the inactive coherence channels) and guidance for applying correlation alignment and baseline-free phasing routines that enable precise ODNP. In this illustration of the 𝐸(𝑝) curve for 150 µM hydroxytempo, subsequent (following Fig.…”

“…However, traditional experiments select a single coherence pathway; as presented in more recent work on multiplex phase cycling [24] and multiplex-quadrature detection (MQD) [25], nowantiquated hardware motivated this choice. By simply forgoing the cycling of the receiver phase and separately storing the acquired transients, post-acquisition processing can select any of the CT pathways acquired during the experiment, as described in the early works that developed the theory of multiple quantum transfer [26] and phase cycling [23], and utilized in multidimensional solid state [27] and biomolecular NMR [28]. This work formalizes and builds on these earlier contributions by presenting a comprehensible display of all of the raw data available from a phase cycled experiment.…”