¹ H NMRD profiles of diamagnetic proteins: a model‐free analysis†

Abstract

A model‐free analysis of the 1H nuclear magnetic relaxation dispersion (NMRD) profiles of 14 proteins in aqueous solution was performed to reproduce the experimental dispersions, that are stretched with respect to Lorentzians. The analysis, according to a recently proposed approach, shows a good correlation of all physically meaningful parameters with the molecular weight of the proteins, spanning the range from 6500 to 480000, and, in particular, of the average correlation time with the Stokes–Einstein estimate of the rotational correlation time. Copyright © 2000 John Wiley & Sons, Ltd.

1H NMR and Rheological Studies of the Calcium Induced Gelation Process in Aqueous Low Methoxyl Pectin Solutions

“…The 1 H NMRD study of water in concentrated protein solutions and semisolid biological systems like gels or tissues has shown the dispersion profiles of longitudinal relaxation rates R 1 extended over a frequency range wider than that for the Lorentzian dispersion form [18,[22][23][24][25][26][27][28][29]. Therefore, the dispersion profiles of such type cannot be correctly reproduced by the Lorentzian spectral density function (except relatively dilute protein solutions), however, they are successfully described by means of the model-free analysis [18,[25][26][27]. The model-free approach [25] to the analysis of the stretched dispersion profiles assumes the multi--Lorentzian form of the spectral density function (SDF) (see (1) and (3)) given by…”

“…1 H NMR relaxometry has been widely used mainly to investigate proteins in solution [22][23][24][25][26] but it has also been applied to study more complex biological systems like gels or tissues [27][28][29][30]. NMR proton spin-spin relaxation time measurements have been found useful for monitoring the mobility and state of aggregation of biomolecules (proteins and polysaccharides) in solution and gelled systems [15,[30][31][32][33][34][35][36][37][38].…”

Long-lived coherences for line-narrowing in high-field NMR

“…In practice, a factor T LLS /T 1 > 37 has been obtained for protons in favourable cases [3]. In nitrous oxide (N 2 O) enriched in 15 N, a LLS comprising two 15 N nuclei can be sustained for several minutes [4]. Such long lifetimes of populations make it possible to extend the time scales over which phenomena such as slow exchange and slow translational diffusion may be characterised by NMR.…”

“…In the former case, the Hamiltonian is switched adiabatically [14], typically in the course of a few seconds, by shuttling the sample outside the B 0 field. The longitudinal relaxation may take its toll, particularly for protons in biological macromolecules, as evidenced by field-cycling 'relaxometry' experiments [15]. In ELF experiments, the desired coherence must then be excited by a slow Rabi nutation in low field, which in practice requires an ELF pulse on the order of a few seconds to obtain a nutation through an angle p/2.…”

The conformational distribution in diphenylmethane determined by nuclear magnetic resonance spectroscopy of a sample dissolved in a nematic liquid crystalline solvent

“…This so-called LXNMR method has a wide range of applicability, and has been used for small, rigid molecules such as benzene 1 in order to make a comparison at high precision between structures obtained in solid, liquid, and gaseous phases, and for molecules as large as ubiquitin to obtain coarse grained structures of this and similar proteins in their folded states. 2,3 A study of the conformation of diphenylmethane is important because it is the simplest case of linkage of two aromatic rings through a methylene group. Such a linkage exists, for example, in trimethoprim, an important therapeutic agent, and in some recently synthesized liquid crystals.…”