Paramagnetic Properties of a Crystalline Iron–Sulfur Protein by Magic-Angle Spinning NMR Spectroscopy

Abstract

We present the first solid-state NMR study of an iron-sulfur protein. The combined use of very fast (60 kHz) magic-angle spinning and tailored radiofrequency irradiation schemes allows the detection and the assignment of most of the H andC resonances of the oxidized high-potential iron-sulfur protein I from Ectothiorhodospira halophila (EhHiPIP I), including those in residues coordinating the FeS cluster. For these residues, contact shifts as large as 100 and 400 ppm for H andC resonances, respectively, were observed, which represent the most shifted solid-state NMR signals ever measured in metalloproteins. Interestingly, by targeting EhHiPIP I in a crystalline environment, we were able to capture distinct paramagnetic signatures from the two conformations present in the asymmetric unit. The magnetic properties of the system were verified by following the temperature dependence of the contact-shifted cysteine resonances.

Cu(II)-Doped Cs2SbAgCl6 Double Perovskite: A Lead-Free, Low-Bandgap Material

“…The temperature dependence is a revealing feature of the behavior of paramagnetic systems and thus has proven useful in studies of a variety of solids. 91,[94][95][96][97][98][99][100][101][102][103][104] All three 133 Cs NMR peaks shift to higher frequency as the temperature is increased (Figures 5a and 5b, and Table S6), but each has a distinct temperature dependence. [74][75][76]80,81 Peak-1 changes slowly with temperature; the small temperature dependence (0.08 ppm/K) for this peak is 5c).…”

Proton-detected fast-magic-angle spinning NMR of paramagnetic inorganic solids

“…9 The improvements associated with fast MAS are particularly evident in samples of paramagnetic molecules, [10][11][12] where sensitivity and resolution experience a spectacular enhancement as compared to slower rates, allowing efficient detection of previously unobservable nuclei in close proximity to a metal center. [13][14][15] Despite this impressive progress, however, the advantages of 1 H detection remain largely unexplored on highly paramagnetic substances. In fully-protonated paramagnetic molecules, the massive paramagnetic shi anisotropies add to the large homonuclear dipolar couplings so that a signicant number of sidebands are observed for some or all of the resonances even at very large spinning rates.…”

Broadband MAS NMR spectroscopy in the low-power limit

“…These pulses have been particularly successful primarily in the application to paramagnetic samples [18,19,20,21,22,23,24,25] and have been incorporated into conventional MAS NMR experiments such as the spin echo [18], the Carr-PurcellMeiboom-Gill echo train acquisition technique [26], a heteronuclear correlation variant of the transferred-echo double resonance experiment [19], and the magic angle turning experiment [20]. Indeed, these pulses have proven quite useful in broadband MAS NMR measurements, however it must be stressed that SHAPs demand very high RF fields, ν 1 , falling in the so-called high-power regime, ν 1 ν R , and this relationship between MAS rate and the required RF field seems to grow at a rate that is more than linear [27].…”