Spatial reorientation experiments for NMR of solids and partially oriented liquids

Martin, Rachel W.; Kelly, John; Collier, Kelsey

doi:10.1016/j.pnmrs.2015.10.001

Cited by 7 publications

(3 citation statements)

References 281 publications

(367 reference statements)

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“…Series c: Δσ aniso ≠ 0 with T S > Δσ aniso with T R > Δσ aniso Series d: Δσ aniso ≠ 0 with T S < Δσ aniso and T R < Δσ aniso Series e: Δσ aniso ≠ 0 with T S > Δσ aniso and T R < Δσ aniso T S > 2Δσ aniso T S = 2Δσ aniso T S < 2Δσ aniso T S = 0 T S > 2Δσ aniso + T R T S = 2Δσ aniso + T R T S < 2Δσ aniso + T R T S = T R T S ≠ T R T S = T R < Δσ aniso T S = T R = Δσ aniso T S > 2Δσ aniso + T R 2ΔΔσ -T R < T S < 2Δσ aniso + T R T S > 2Δσ aniso -T R T S = 2Δσ aniso +T R T S = 2Δσ aniso -T R large magnitude of anisotropic interactions, such as ( 1 H-1 H)-RDCs, leads to second-order 1 H-NMR spectra. As a consequence, during two decades, numerous practical approaches were developed to simplify the analysis of strongly oriented 1 H NMR spectra, and subsequently also of 13 C. Without being exhaustive, we can mention: i) the selective or partial deuteration [65,66]; ii) the use of multiple quantum (MQ) 2D experiments [67,68,69,70] or the combination of them [71]; iii) the reduction of anisotropic interactions by spin manipulation via appropriate multiple-pulse sequences [72,73,74,75]; or iv) the variable angle spinning sample (VASS) technique [76,77,78,79].…”

Section: Polypeptide-based Lcs Versus Thermotropicsmentioning

confidence: 99%

Multinuclear NMR in polypeptide liquid crystals: Three fertile decades of methodological developments and analytical challenges

Lesot

Aroulanda

Berdagué

et al. 2020

Progress in Nuclear Magnetic Resonance Spectroscopy

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NMR spectroscopy of oriented samples makes accessible residual anisotropic intramolecular NMR interactions, such as chemical shift anisotropy (RCSA), dipolar coupling (RDC), and quadrupolar coupling (RQC), while preserving high spectral resolution. In addition, in a chiral aligned environment, enantiomers of chiral molecules or enantiopic elements of prochiral compounds adopt different average orientations on the NMR timescale, and hence produce distinct NMR spectra or signals. NMR spectroscopy in chiral aligned media is a powerful analytical tool, and notably provides unique information on (pro)chirality analysis, natural isotopic fractionation, stereochemistry, as well as molecular conformation and configuration. Significant progress has been made in this area over the three last decades, particularly using polypeptide-based chiral liquid crystals (CLCs) made of organic solutions of helically chiral polymers (as PBLG) in organic solvents. This review presents an overview of NMR in polymeric LCs. In particular, we describe the theoretical tools and the major NMR methods that have been developed and applied to study (pro)chiral molecules dissolved in such oriented solvents. We also discuss the representative applications illustrating the analytical potential of this original NMR tool. This overview article is dedicated to thirty years of original contributions to the development of NMR spectroscopy in polypeptide-based chiral liquid crystals.

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Section: Polypeptide-based Lcs Versus Thermotropicsmentioning

confidence: 99%

Multinuclear NMR in polypeptide liquid crystals: Three fertile decades of methodological developments and analytical challenges

Lesot

Aroulanda

Berdagué

et al. 2020

Progress in Nuclear Magnetic Resonance Spectroscopy

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“…Nowadays, NMR spectroscopy is one of the most important analytical tools that has been used in several fields. These fields include structural biology [29][30][31][32][33][34][35][36][37][38], organic chemistry [39][40][41][42][43][44][45][46][47][48][49][50][51][52], polymer characterization [40,46,[53][54][55][56][57][58][59][60][61][62][63][64], inorganic chemistry [65][66][67][68][69][70][71][72][73][74][75], and physics [76][77][...…”

mentioning

confidence: 99%

New Advances in Fast Methods of 2D NMR Experiments

Emwas¹,

Alghrably²,

Al-Harthi³

et al. 2020

Nuclear Magnetic Resonance

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Although nuclear magnetic resonance spectroscopy is a potent analytical tool for identification, quantification, and structural elucidation, it suffers from inherently low sensitivity limitations. This chapter focuses on recently reported methods that enable quick acquisition of NMR spectra, as well as new methods of faster, efficient, and informative two-dimensional (2D) NMR methods. Fast and efficient data acquisition has risen in response to an increasing need to investigate chemical and biological processes in real time. Several new techniques have been successfully introduced. One example of this is band-selective optimized-flip-angle shorttransient (SOFAST) NMR, which has opened the door to studying the kinetics of biological processes such as the phosphorylation of proteins. The fast recording of NMR spectra allows researchers to investigate time sensitive molecules that have limited stability under experimental conditions. The increasing awareness that molecular structures are dynamic, rather than static, has pushed some researchers to find alternatives to standard, time-consuming methods of 15 N relaxation observables acquisition.Keywords: NMR, 2D NMR, ultrafast data processing, SOFAST, relaxation 15 N, 29 Si, 30 Al, 31 P to 235 U). As the resonating frequency is unique for each type of nuclei, one can envision an NMR for each nucleus as a separate spectroscopy such as 1 H NMR spectroscopy, 13 C NMR spectroscopy, 235 U NMR spectroscopy (Figure 1), etc. More importantly, NMR has the ability to evaluate information about the environment of each atom and their neighbor's nuclei (both through space and through bond), allowing researchers to differentiate the unique magnetic environments of the same nuclei in different positions of a single molecule. Thus, NMR spectroscopy is extensively used for the identification and in the structural elucidation in a wide Nuclear Magnetic Resonance 2 range of applications in gas [2,3], liquid [4][5][6][7][8][9][10][11][12][13][14][15][16], and solid-state samples [17][18][19][20][21][22][23][24][25][26][27][28]. Nowadays, NMR spectroscopy is one of the most important analytical tools that has been used in several fields. These fields include structural biology [29][30][31][32][33][34][35][36][37][38], organic chemistry [39][40][41][42][43][44][45][46][47][48][49][50][51][52], polymer characterization [40,46,[53][54][55][56][57][58][59][60][61][62][63][64], inorganic chemistry [65][66][67][68][69][70][71][72][73][74][75], and physics [76][77][78][79][80][81][82][83].Despite its significant advantages, NMR suffers from some limitations, of which the relatively low sensitivity seems to be the most severe. An NMR sample can be treated as a collection of many nuclear spins of magnetically active nuclei that act as small bar magnets. These nuclear spins have two possible orientations with different energy levels that adapt when placed within the strong magnetic field. The number of nuclear spins occupying each energy level is determined by the Boltzmann distribution equation: N ...

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“…A number of averaging methods such as variable angle spinning (VAS) 234 , double rotation (DOR) 235 , dynamic angle spinning (DAS) 236 , and multiple quantum magic angle spinning (MQMAS) 237 have been developed to address the problems of the second order quadrupole interaction. 238 Among these, MQMAS has often become the method of choice to remove the undesirable second order quadrupole interactions for half-integer quadrupole nuclei and to extract isotropic chemical shifts and quadrupolar coupling parameters since it does not require additional hardware beyond MAS-NMR.…”

mentioning

confidence: 99%

Probing the photointermediates of light-driven sodium ion pump KR2 by DNP-enhanced solid-state NMR

Jakdetchai¹

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KR2 is a light-driven sodium ion pump found in marine flavobacterium Krokinobacter Eikastus. The protein belongs to the microbial rhodopsin family, which is characterized by seven transmembrane helices and a retinal cofactor covalently bound to a conserved lysine residue through a Schiff base linkage. Specific features of KR2 and other sodium pumping rhodopsins are the NDQ motif, the N-terminal helix capping the protein at the extracellular side, and the sodium ion bound at the protomer interface in the pentameric structure. The ability to pump sodium ions was a surprising discovery since the positive charge at the Schiff base was long thought to hinder the transport of non-proton cations and the Grotthuss mechanism could not be applied to explain the Na+ transport. The photocycle of KR2 revealed by flashed photolysis and ultrafast femtosecond absorption spectroscopy consists of consecutive intermediates, named K, L, M, and O. Here, DNP-enhanced ssNMR was used to analyze various aspects of these intermediate states. The K/L-state can be generated and trapped by in-situ illumination inside the magnet at 110 K. The trapping of L-state together with the K-state at this temperature is unexpected as this usually leads to the trapping of only K-state in bacteriorhodopsin (BR), proteorhodopsin (PR), and channelrhodopsin 2 (ChR2). This observation suggests a lower energy barrier between K- and L-state in KR2. For the O-state, the intermediate was generated by illuminating outside the magnet, followed by rapid freezing in liquid nitrogen and transfer to the magnet. Based on these procedures, the retinal conformation, and the electrostatic environment at the Schiff base in KR2 dark, K-, L- and O-intermediates were probed using 13C-labeled retinals bound to 15N-labeled KR2 by both 1D and 2D magic angle spinning (MAS) NMR experiments. The obtained data show an all-trans retinal conformation with the distortion of 150° at H-C14-C15-H in the dark state whereas the retinal has a 13-cis, 15-anti conformation in the K- and L-state after light activation. Differences between K- and L-intermediates were observed. The retinal chemical shifts of the K-state show a large deviation from the model compound behavior between the middle and end part of the polyene chain. In the L-state, these differences are much less pronounced. These observations indicate that the light energy stored in the K-state dissipates into the protein in the subsequent photointermediate states. Furthermore, an additional shielding observed for C14 in L-state indicates the slight rotation toward a more compact 13-cis, 15-syn conformation. The distortion of the H-C14-C15-H angle in the L-state (136°) is larger than in the dark state. This twist of the retinal in the L-state would play an important role in lowering the pKa of the Schiff base, which is a prerequisite for the proton transfer from the Schiff base to the proton acceptor (D116). The electrostatic environments at the Schiff base in K- and L-states cause a de-shielding of the 15N nitrogen compared to the dark state. This indicates a stepwise stronger interaction with the counterion as the Schiff base proton moves away from the Schiff base and comes closer to the D116 in the transition from K- to L-state and approaches the proton transfer step during the M-state formation. In the O-state, the retinal was found to be in the all-trans conformation but differed to the dark state in the C13, C20, and Schiff base nitrogen chemical shifts. The largest effect (9 ppm) was observed for the Schiff base nitrogen, which could be explained by the effect of the positive charge of bound Na+ near the Schiff base in the O-state, coordinated by N112 and D116 as observed in the O-state crystal structure in the pentameric form. The structural change at the opsin followed the retinal isomerization and the energy transfer from the chromophore to the surrounding were also investigated in this thesis using various amino acids labeling schemes. Moreover, 1H-13C hNOE in combination with CE-DNP was applied to probe the dynamics of retinylidene methyl groups and 23Na MAS NMR was employed to detect the bound sodium ion at the protomer interface in KR2 dark state.

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Spatial reorientation experiments for NMR of solids and partially oriented liquids

Cited by 7 publications

References 281 publications

Multinuclear NMR in polypeptide liquid crystals: Three fertile decades of methodological developments and analytical challenges

Multinuclear NMR in polypeptide liquid crystals: Three fertile decades of methodological developments and analytical challenges

New Advances in Fast Methods of 2D NMR Experiments

Probing the photointermediates of light-driven sodium ion pump KR2 by DNP-enhanced solid-state NMR

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