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Gopinath T, Weber DK, Veglia G. Multi-receiver solid-state NMR using polarization optimized experiments (POE) at ultrafast magic angle spinning. JOURNAL OF BIOMOLECULAR NMR 2020; 74:267-285. [PMID: 32333193 PMCID: PMC7236978 DOI: 10.1007/s10858-020-00316-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Accepted: 04/11/2020] [Indexed: 05/04/2023]
Abstract
Ultrafast magic angle spinning (MAS) technology and 1H detection have dramatically enhanced the sensitivity of solid-state NMR (ssNMR) spectroscopy of biopolymers. We previously showed that, when combined with polarization optimized experiments (POE), these advancements enable the simultaneous acquisition of multi-dimensional 1H- or 13C-detected experiments using a single receiver. Here, we propose a new sub-class within the POE family, namely HC-DUMAS, HC-MEIOSIS, and HC-MAeSTOSO, that utilize dual receiver technology for the simultaneous detection of 1H and 13C nuclei. We also expand this approach to record 1H-, 13C-, and 15N-detected homonuclear 2D spectra simultaneously using three independent receivers. The combination of POE and multi-receiver technology will further shorten the total experimental time of ssNMR experiments for biological solids.
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Affiliation(s)
- T Gopinath
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, MN, 55455, USA
| | - Daniel K Weber
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, MN, 55455, USA
| | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, MN, 55455, USA.
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455, USA.
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Gopinath T, Wang S, Lee J, Aihara H, Veglia G. Hybridization of TEDOR and NCX MAS solid-state NMR experiments for simultaneous acquisition of heteronuclear correlation spectra and distance measurements. JOURNAL OF BIOMOLECULAR NMR 2019; 73:141-153. [PMID: 30805819 PMCID: PMC6526076 DOI: 10.1007/s10858-019-00237-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 02/12/2019] [Indexed: 05/05/2023]
Abstract
Magic angle spinning (MAS) solid-state NMR (ssNMR) spectroscopy is a major technique for the characterization of the structural dynamics of biopolymers at atomic resolution. However, the intrinsic low sensitivity of this technique poses significant limitations to its routine application in structural biology. Here we achieve substantial savings in experimental time using a new subclass of Polarization Optimized Experiments (POEs) that concatenate TEDOR and SPECIFIC-CP transfers into a single pulse sequence. Specifically, we designed new 2D and 3D experiments (2D TEDOR-NCX, 3D TEDOR-NCOCX, and 3D TEDOR-NCACX) to obtain distance measurements and heteronuclear chemical shift correlations for resonance assignments using only one experiment. We successfully tested these experiments on N-Acetyl-Val-Leu dipeptide, microcrystalline U-13C,15N ubiquitin, and single- and multi-span membrane proteins reconstituted in lipid membranes. These pulse sequences can be implemented on any ssNMR spectrometer equipped with standard solid-state hardware using only one receiver. Since these new POEs speed up data acquisition considerably, we anticipate their broad application to fibrillar, microcrystalline, and membrane-bound proteins.
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Affiliation(s)
- T Gopinath
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, MN, 55455, USA
| | - Songlin Wang
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, MN, 55455, USA
| | - John Lee
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, MN, 55455, USA
| | - Hideki Aihara
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, MN, 55455, USA
| | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, MN, 55455, USA.
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455, USA.
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Kakita VMR, Kupče Ē, Bharatam J, Hosur RV. Rapid elucidation of chemical shift correlations in complex NMR spectra of organic molecules: Two-dimensional Hadamard pure shift NMR spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 293:77-81. [PMID: 29908413 DOI: 10.1016/j.jmr.2018.06.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 06/02/2018] [Accepted: 06/07/2018] [Indexed: 06/08/2023]
Abstract
Novel two dimensional Hadamard encoding/decoding based pure shift NMR acquisition techniques (TOCSY and HSQC) have been developed, which provide chemical shift information at ultra high resolution in very short spectrometer times. The efficacy of these methods for rapid assignment of chemical shifts in complex NMR spectra of organic molecules/natural products has been demonstrated. This would be of great help for rapid analysis of samples during separation of complex mixtures.
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Affiliation(s)
- Veera Mohana Rao Kakita
- UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai, Kalina Campus, Santacruz, Mumbai 400 098, India
| | - Ēriks Kupče
- Bruker (UK) Ltd., Banner Lane, Coventry CV4 9GH, UK
| | - Jagadeesh Bharatam
- Centre for NMR and Structural Chemistry, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, India
| | - Ramakrishna V Hosur
- UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai, Kalina Campus, Santacruz, Mumbai 400 098, India; Department of Chemical Sciences, Tata Institute of Fundamental Research (TIFR), 1-Homi Bhabha Road, Colaba, Mumbai 400 005, India.
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Kakita VMR, Hosur RV. Hadamard Homonuclear Broadband Decoupled TOCSY NMR: Improved Efficacy in Detecting Long-range Chemical Shift Correlations. Chemphyschem 2016; 17:4037-4042. [DOI: 10.1002/cphc.201600769] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 09/30/2016] [Indexed: 12/28/2022]
Affiliation(s)
- Veera Mohana Rao Kakita
- UM-DAE-Centre for Excellence in Basic Sciences; University of Mumbai; Kalina Campus, Santa Cruz Mumbai 400 098 India
| | - Ramakrishna V. Hosur
- UM-DAE-Centre for Excellence in Basic Sciences; University of Mumbai; Kalina Campus, Santa Cruz Mumbai 400 098 India
- Department of Chemical Sciences; Tata Institute of Fundamental Research (TIFR); 1-Homi Bhabha Road, Colaba Mumbai 400 005 India
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Molugu TR, Brown MF. Cholesterol-induced suppression of membrane elastic fluctuations at the atomistic level. Chem Phys Lipids 2016; 199:39-51. [PMID: 27154600 DOI: 10.1016/j.chemphyslip.2016.05.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 04/29/2016] [Accepted: 05/02/2016] [Indexed: 12/14/2022]
Abstract
Applications of solid-state NMR spectroscopy for investigating the influences of lipid-cholesterol interactions on membrane fluctuations are reviewed in this paper. Emphasis is placed on understanding the energy landscapes and fluctuations at an emergent atomistic level. Solid-state (2)H NMR spectroscopy directly measures residual quadrupolar couplings (RQCs) due to individual C-(2)H labeled segments of the lipid molecules. Moreover, residual dipolar couplings (RDCs) of (13)C-(1)H bonds are obtained in separated local-field NMR spectroscopy. The distributions of RQC or RDC values give nearly complete profiles of the order parameters as a function of acyl segment position. Measured equilibrium properties of glycerophospholipids and sphingolipids including their binary and tertiary mixtures with cholesterol show unequal mixing associated with liquid-ordered domains. The entropic loss upon addition of cholesterol to sphingolipids is less than for glycerophospholipids and may drive the formation of lipid rafts. In addition relaxation time measurements enable one to study the molecular dynamics over a wide time-scale range. For (2)H NMR the experimental spin-lattice (R1Z) relaxation rates follow a theoretical square-law dependence on segmental order parameters (SCD) due to collective slow dynamics over mesoscopic length scales. The functional dependence for the liquid-crystalline lipid membranes is indicative of viscoelastic properties as they emerge from atomistic-level interactions. A striking decrease in square-law slope upon addition of cholesterol denotes stiffening relative to the pure lipid bilayers that is diminished in the case of lanosterol. Measured equilibrium properties and relaxation rates infer opposite influences of cholesterol and detergents on collective dynamics and elasticity at an atomistic scale that potentially affects lipid raft formation in cellular membranes.
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Affiliation(s)
- Trivikram R Molugu
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Michael F Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA; Department of Physics, University of Arizona, Tucson, AZ 85721, USA.
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Kakita VMR, Kupče E, Bharatam J. Solid-state Hadamard NMR spectroscopy: simultaneous measurements of multiple selective homonuclear scalar couplings. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 251:8-12. [PMID: 25554944 DOI: 10.1016/j.jmr.2014.11.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 11/10/2014] [Accepted: 11/16/2014] [Indexed: 06/04/2023]
Abstract
Unambiguous measurement of homonuclear scalar couplings (J) in multi-spin scalar network systems is not straightforward. Further, the direct measurement of J-couplings is obscured in solid-state samples due to the dipolar and chemical shift anisotropy (CSA)-dominated line broadening, even under the magic angle spinning (MAS). We present a new multiple frequency selective spin-echo method based on Hadamard matrix encoding, for simultaneous measurement of multiple homonuclear scalar couplings (J) in the solid-state. In contrast to the Hadamard encoded selective excitation schemes known for the solution-state, herein the selectivity is achieved during refocusing period. The Hadamard encoded refocusing scheme concurrently allows to create the spin-spin commutation property between number of spin-pairs of choice in uniformly labelled molecules, which, therefore avoids (1) the repetition of the double selective refocusing experiments for each spin-pair and (2) the synthesis of expensive selective labelled molecules. The experimental scheme is exemplified for determining (1)JCC and (3)JCC values in (13)C6l-Histidine.HCl molecule, which are found to be in excellent agreement with those measured in conventional double frequency selective refocusing mode as well as in the solution-state. This method can be simply extended to 2D/3D pulse schemes and be applied to small bio-molecular solids.
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Affiliation(s)
- Veera Mohana Rao Kakita
- Centre for NMR & Structural Chemistry, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, India
| | - Eriks Kupče
- Bruker UK Limited, Banner Lane, Coventry CV4 9GH, UK
| | - Jagadeesh Bharatam
- Centre for NMR & Structural Chemistry, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, India.
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Löhr F, Laguerre A, Bock C, Reckel S, Connolly PJ, Abdul-Manan N, Tumulka F, Abele R, Moore JM, Dötsch V. Time-shared experiments for efficient assignment of triple-selectively labeled proteins. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 248:81-95. [PMID: 25442777 PMCID: PMC4254601 DOI: 10.1016/j.jmr.2014.09.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 09/10/2014] [Accepted: 09/16/2014] [Indexed: 05/20/2023]
Abstract
Combinatorial triple-selective labeling facilitates the NMR assignment process for proteins that are subject to signal overlap and insufficient signal-to-noise in standard triple-resonance experiments. Aiming at maximum amino-acid type and sequence-specific information, the method represents a trade-off between the number of selectively labeled samples that have to be prepared and the number of spectra to be recorded per sample. In order to address the demand of long measurement times, we here propose pulse sequences in which individual phase-shifted transients are stored separately and recombined later to produce several 2D HN(CX) type spectra that are usually acquired sequentially. Sign encoding by the phases of (13)C 90° pulses allows to either select or discriminate against (13)C' or (13)C(α) spins coupled to (15)N. As a result, (1)H-(15)N correlation maps of the various isotopomeric species present in triple-selectively labeled proteins are deconvoluted which in turn reduces problems due to spectral overlap. The new methods are demonstrated with four different membrane proteins with rotational correlation times ranging from 18 to 52 ns.
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Affiliation(s)
- Frank Löhr
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
| | - Aisha Laguerre
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
| | - Christoph Bock
- Institute of Biochemistry, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
| | - Sina Reckel
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
| | | | | | - Franz Tumulka
- Institute of Biochemistry, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
| | - Rupert Abele
- Institute of Biochemistry, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
| | | | - Volker Dötsch
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany.
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Gopinath T, Veglia G. Orphan spin operators enable the acquisition of multiple 2D and 3D magic angle spinning solid-state NMR spectra. J Chem Phys 2013; 138:184201. [PMID: 23676036 DOI: 10.1063/1.4803126] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We propose a general method that enables the acquisition of multiple 2D and 3D solid-state NMR spectra for U-(13)C, (15)N-labeled proteins. This method, called MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), makes it possible to detect four coherence transfer pathways simultaneously, utilizing orphan (i.e., neglected) spin operators of nuclear spin polarization generated during (15)N-(13)C cross polarization (CP). In the MEIOSIS experiments, two phase-encoded free-induction decays are decoded into independent nuclear polarization pathways using Hadamard transformations. As a proof of principle, we show the acquisition of multiple 2D and 3D spectra of U-(13)C, (15)N-labeled microcrystalline ubiquitin. Hadamard decoding of CP coherences into multiple independent spin operators is a new concept in solid-state NMR and is extendable to many other multidimensional experiments. The MEIOSIS method will increase the throughput of solid-state NMR techniques for microcrystalline proteins, membrane proteins, and protein fibrils.
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Affiliation(s)
- T Gopinath
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Gopinath T, Mote KR, Veglia G. Sensitivity and resolution enhancement of oriented solid-state NMR: application to membrane proteins. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2013; 75:50-68. [PMID: 24160761 PMCID: PMC3850070 DOI: 10.1016/j.pnmrs.2013.07.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 06/16/2013] [Indexed: 05/19/2023]
Abstract
Oriented solid-state NMR (O-ssNMR) spectroscopy is a major technique for the high-resolution analysis of the structure and topology of transmembrane proteins in native-like environments. Unlike magic angle spinning (MAS) techniques, O-ssNMR spectroscopy requires membrane protein preparations that are uniformly oriented (mechanically or magnetically) so that anisotropic NMR parameters, such as dipolar and chemical shift interactions, can be measured to determine structure and orientation of membrane proteins in lipid bilayers. Traditional sample preparations involving mechanically aligned lipids often result in short relaxation times which broaden the (15)N resonances and encumber the manipulation of nuclear spin coherences. The introduction of lipid bicelles as membrane mimicking systems has changed this scenario, and the more favorable relaxation properties of membrane protein (15)N and (13)C resonances make it possible to develop new, more elaborate pulse sequences for higher spectral resolution and sensitivity. Here, we describe our recent progress in the optimization of O-ssNMR pulse sequences. We explain the theory behind these experiments, demonstrate their application to small and medium size proteins, and describe the technical details for setting up these new experiments on the new generation of NMR spectrometers.
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Affiliation(s)
- T. Gopinath
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, United States
| | - Kaustubh R. Mote
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, United States
| | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, United States
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, United States
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Mote KR, Gopinath T, Veglia G. Determination of structural topology of a membrane protein in lipid bilayers using polarization optimized experiments (POE) for static and MAS solid state NMR spectroscopy. JOURNAL OF BIOMOLECULAR NMR 2013; 57:91-102. [PMID: 23963722 PMCID: PMC3883141 DOI: 10.1007/s10858-013-9766-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 07/26/2013] [Indexed: 05/11/2023]
Abstract
The low sensitivity inherent to both the static and magic angle spinning techniques of solid-state NMR (ssNMR) spectroscopy has thus far limited the routine application of multidimensional experiments to determine the structure of membrane proteins in lipid bilayers. Here, we demonstrate the advantage of using a recently developed class of experiments, polarization optimized experiments, for both static and MAS spectroscopy to achieve higher sensitivity and substantial time-savings for 2D and 3D experiments. We used sarcolipin, a single pass membrane protein, reconstituted in oriented bicelles (for oriented ssNMR) and multilamellar vesicles (for MAS ssNMR) as a benchmark. The restraints derived by these experiments are then combined into a hybrid energy function to allow simultaneous determination of structure and topology. The resulting structural ensemble converged to a helical conformation with a backbone RMSD ~0.44 Å, a tilt angle of 24° ± 1°, and an azimuthal angle of 55° ± 6°. This work represents a crucial first step toward obtaining high-resolution structures of large membrane proteins using combined multidimensional oriented solid-state NMR and magic angle spinning solid-state NMR.
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Affiliation(s)
- Kaustubh R. Mote
- Department of Chemistry University of Minnesota, Minneapolis, MN 55455, USA
| | - T. Gopinath
- Department of Biochemistry, Molecular Biology & Biophysics University of Minnesota, Minneapolis, MN 55455, USA
| | - Gianluigi Veglia
- Department of Chemistry University of Minnesota, Minneapolis, MN 55455, USA
- Department of Biochemistry, Molecular Biology & Biophysics University of Minnesota, Minneapolis, MN 55455, USA
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Dürr UN, Gildenberg M, Ramamoorthy A. The magic of bicelles lights up membrane protein structure. Chem Rev 2012; 112:6054-74. [PMID: 22920148 PMCID: PMC3497859 DOI: 10.1021/cr300061w] [Citation(s) in RCA: 266] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Indexed: 12/12/2022]
Affiliation(s)
| | - Melissa Gildenberg
- Biophysics
and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055,
United States
| | - Ayyalusamy Ramamoorthy
- Biophysics
and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055,
United States
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Gopinath T, Veglia G. 3D DUMAS: simultaneous acquisition of three-dimensional magic angle spinning solid-state NMR experiments of proteins. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 220:79-84. [PMID: 22698806 PMCID: PMC3487463 DOI: 10.1016/j.jmr.2012.04.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 04/13/2012] [Indexed: 05/15/2023]
Abstract
Using the DUMAS (Dual acquisition Magic Angle Spinning) solid-state NMR approach, we created new pulse schemes that enable the simultaneous acquisition of three dimensional (3D) experiments on uniformly (13)C, (15)N labeled proteins. These new experiments exploit the simultaneous cross-polarization (SIM-CP) from (1)H to (13)C and (15)N to acquire two 3D experiments simultaneously. This is made possible by bidirectional polarization transfer between (13)C and (15)N and the long living (15)N z-polarization in solid state NMR. To demonstrate the power of this approach, four 3D pulse sequences (NCACX, CANCO, NCOCX, CON(CA)CX) are combined into two pulse sequences (3D DUMAS-NCACX-CANCO, 3D DUMAS-NCOCX-CON(CA)CX) that allow simultaneous acquisition of these experiments, reducing the experimental time by approximately half. Importantly, the 3D DUMAS-NCACX-CANCO experiment alone makes it possible to obtain the majority of the backbone sequential resonance assignments for microcrystalline U-(13)C,(15)N ubiquitin. The DUMAS approach is general and applicable to many 3D experiments, nearly doubling the performance of NMR spectrometers.
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Affiliation(s)
- T. Gopinath
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455
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