Direct magnetic-field dependence of NMR chemical shift

Kantola, Anu M.; Lantto, Perttu; Heinmaa, Ivo; Vaara, Juha; Jokisaari, Jukka

doi:10.1039/d0cp01372b

“…The process of membrane protein extraction occurs stepwise. After membrane dissolution, several steps of purification are involved before handling the final desired product. ,,− Among the resulting materials, copolymer chains that are in equilibrium with the nanodisc-bound chains are discarded too. We speculate that this process, in addition to dilution, may alter the integrity of the nanodiscs as per the principle of chemical equilibrium.…”

Section: Resultsmentioning

confidence: 99%

Benchmarks of SMA-Copolymer Derivatives and Nanodisc Integrity

Mauro

¹

,

Raudino

²

,

Condorelli

³

et al. 2021

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Poly(styrene-co-maleic acid) or SMA and its derivatives, a family of synthetic amphipathic copolymers, are increasingly used to directly solubilize cell membranes to functionally reconstitute membrane proteins in native-like copolymer–lipid nanodiscs. Although these copolymers act, de facto, like a “macromolecular detergent”, the polymer-based lipid-nanodiscs has been demonstrated to be an excellent membrane mimetic for structural and functional studies of membrane proteins and their complexes by a variety of biophysical and biochemical approaches. In many studies reported in the literature, the choice of the right SMA formulation can depend on a number of factors, and the experimental conditions are typically developed according to a trial-and-error process since each studied system requires adapted protocols. While increasing number of nanodisc-forming copolymers are reported to be useful and they provide flexibilities in optimizing the sample preparation conditions, it is important to develop a systematic protocol that can be used for various applications. In this context, there is a vital necessity of benchmarking the performances of existing copolymer formulations, assessing crucial parameters for the successful extraction, isolation, and stabilization of membrane proteins. In this study, we compare both copolymers and copolymer–lipid nanodiscs obtained by SMA-EA with a set of anionic XIRAN copolymer formulations commercially available under the names of SL25010 P, SL30010 P, and SL40005 P. The reported results show how the critical micellar concentration (c.m.c.) of each copolymer is significantly altered in the presence of lipids and confirms the existence of an equilibrium between nanodisc-bound and “free” or “micellar” copolymer chains in the solution. We believe that these findings can be exploited to optimize studies that involve the necessity of special copolymers, which would not only simplify the applications but also broaden the scope of polymer-based nanodiscs.

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“…In addition to these, the prediction by Ramsey for the modest influence of the NMR shift on the magnetic field strength in 1970 7 has lately been proven. 8 Implementation of the efficient gauge-independent atomic orbital (GIAO) approach 9 has allowed density functional theory (DFT) and ab initio methods of quantum chemistry to be routinely and successfully applied to the prediction of NMR shifts and spin–spin coupling constants in electronic structure calculations. 10–14…”

Section: Introductionmentioning

confidence: 99%

“…In addition to these, the prediction by Ramsey for the modest influence of the NMR shift on the magnetic field strength in 1970 7 has lately been proven. 8 Implementation of the efficient gauge-independent atomic orbital (GIAO) approach 9 has allowed density functional theory (DFT) and ab initio methods of quantum chemistry to be routinely and successfully applied to the prediction of NMR shifts and spin-spin coupling constants in electronic structure calculations. [10][11][12][13][14] Acquisition and interpretation of NMR data from paramagnetic systems, on the other hand, is still far from routine, when chemical insight into ligand atoms in close proximity to a paramagnetic transition metal (TM) or rare-earth (RE) ion is required.…”

Section: Introductionmentioning

confidence: 99%