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Kallies W, Glaser SJ. Cooperative broadband spin echoes through optimal control. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 286:115-137. [PMID: 29241044 DOI: 10.1016/j.jmr.2017.10.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 10/25/2017] [Accepted: 10/29/2017] [Indexed: 06/07/2023]
Abstract
The Hahn echo sequence is one of the most common building blocks in magnetic resonance, consisting of an excitation pulse and a refocusing pulse. Conventional approaches to improve the performance of echo experiments focused on the optimization of individual pulses, compensating their own imperfections. Here we present an approach to concurrently design both pulses such that they also compensate each others imperfections. The fact that for such cooperative pulses the individual pulses do not need to be perfect provides additional degrees of freedom, resulting in improved overall Hahn echo performance. Single-scan cooperative pulses are compared to conventional approaches by simulations as well as experiments.
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Affiliation(s)
- Wolfgang Kallies
- Department of Chemistry, Technical University of Munich, Lichtenbergstr. 4, 85748 Garching, Germany
| | - Steffen J Glaser
- Department of Chemistry, Technical University of Munich, Lichtenbergstr. 4, 85748 Garching, Germany.
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2
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Koos MRM, Feyrer H, Luy B. Broadband RF-amplitude-dependent flip angle pulses with linear phase slope. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2017; 55:797-803. [PMID: 28321918 DOI: 10.1002/mrc.4593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 03/08/2017] [Accepted: 03/11/2017] [Indexed: 06/06/2023]
Abstract
Pulse sequences in NMR spectroscopy sometimes require the application of pulses with effective flip angles different from 90° and 180°. Previously (Magn. Reson. Chem. 2015, 53, 886-893), offset-compensated broadband excitation pulses with RF-amplitude-dependent effective flip angles (RADFA) were introduced that are applicable in such cases. However, especially RF-amplitude-restricted RADFA pulses turned out to perform not as good as desired in terms of achievable bandwidths. Here, a class of RF-amplitude-restricted RADFA pulses with linear phase slope is introduced that allows excitation over much larger bandwidths with better performance. In this theoretical work, the basic principle of the pulse class is explained, their physical limits explored, and their properties, also compared with other pulse classes, discussed in detail. Copyright © 2017 John Wiley & Sons, Ltd.
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Affiliation(s)
- Martin R M Koos
- Institut für Biologische Grenzflächen 4 - Magnetische Resonanz, Karlsruher Institut für Technologie (KIT), Postfach 3640, 76021, Karlsruhe, Germany
| | - Hannes Feyrer
- Institut für Organische Chemie, Karlsruher Institut für Technologie (KIT), Fritz-Haber-Weg 6, 76131, Karlsruhe, Germany
- Department of Medical Biochemistry and Biophysics (MBB), Karolinska Institutet, Scheeles Väg 2, 171 77, Stockholm, Sweden
| | - Burkhard Luy
- Institut für Biologische Grenzflächen 4 - Magnetische Resonanz, Karlsruher Institut für Technologie (KIT), Postfach 3640, 76021, Karlsruhe, Germany
- Institut für Organische Chemie, Karlsruher Institut für Technologie (KIT), Fritz-Haber-Weg 6, 76131, Karlsruhe, Germany
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3
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Spindler PE, Schöps P, Kallies W, Glaser SJ, Prisner TF. Perspectives of shaped pulses for EPR spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 280:30-45. [PMID: 28579101 DOI: 10.1016/j.jmr.2017.02.023] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Revised: 02/27/2017] [Accepted: 02/28/2017] [Indexed: 06/07/2023]
Abstract
This article describes current uses of shaped pulses, generated by an arbitrary waveform generator, in the field of EPR spectroscopy. We show applications of sech/tanh and WURST pulses to dipolar spectroscopy, including new pulse schemes and procedures, and discuss the more general concept of optimum-control-based pulses for applications in EPR spectroscopy. The article also describes a procedure to correct for experimental imperfections, mostly introduced by the microwave resonator, and discusses further potential applications and limitations of such pulses.
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Affiliation(s)
- Philipp E Spindler
- Institute of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic Resonance, Goethe University Frankfurt, Germany
| | - Philipp Schöps
- Institute of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic Resonance, Goethe University Frankfurt, Germany
| | - Wolfgang Kallies
- Department of Chemistry, Technical University of Munich, Germany
| | - Steffen J Glaser
- Department of Chemistry, Technical University of Munich, Germany
| | - Thomas F Prisner
- Institute of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic Resonance, Goethe University Frankfurt, Germany.
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4
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Köcher SS, Heydenreich T, Zhang Y, Reddy GNM, Caldarelli S, Yuan H, Glaser SJ. Time-optimal excitation of maximum quantum coherence: Physical limits and pulse sequences. J Chem Phys 2016; 144:164103. [DOI: 10.1063/1.4945781] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- S. S. Köcher
- Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany
- Institute of Energy and Climate Research (IEK-9), Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - T. Heydenreich
- Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany
| | - Y. Zhang
- Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany
| | - G. N. M. Reddy
- Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397 Marseille, France
| | - S. Caldarelli
- Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397 Marseille, France
| | - H. Yuan
- Department of Mechanical and Automation Engineering, Chinese University of Hong Kong, Shatin, Hong Kong, China
| | - S. J. Glaser
- Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany
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5
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Köcher SS, Heydenreich T, Glaser SJ. Visualization and analysis of modulated pulses in magnetic resonance by joint time-frequency representations. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 249:63-71. [PMID: 25462948 DOI: 10.1016/j.jmr.2014.10.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 09/27/2014] [Accepted: 10/05/2014] [Indexed: 06/04/2023]
Abstract
We study the utility of joint time-frequency representations for the analysis of shaped or composite pulses for magnetic resonance. Such spectrograms are commonly used for the visualization of shaped laser pulses in optical spectroscopy. This intuitive representation provides additional insight compared to conventional approaches, which exclusively show either temporal or spectral information. We focus on the short-time Fourier transform, which provides not only amplitude but also phase information. The approach is illustrated for broadband inversion pulses, multiple quantum excitation and broadband heteronuclear decoupling. The physical interpretation and validity of the approach is discussed.
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Affiliation(s)
- S S Köcher
- Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany
| | - T Heydenreich
- Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany
| | - S J Glaser
- Department of Chemistry, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany.
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6
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Dogra S, Dorai K. Numerically optimized band-selective pulses in SOFAST-HMQC experiments for biomolecular NMR. J Mol Struct 2014. [DOI: 10.1016/j.molstruc.2014.01.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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7
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Schilling F, Glaser SJ. Tailored real-time scaling of heteronuclear couplings. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 223:207-218. [PMID: 22982752 DOI: 10.1016/j.jmr.2012.07.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 07/21/2012] [Accepted: 07/31/2012] [Indexed: 06/01/2023]
Abstract
Heteronuclear couplings are a valuable source of molecular information, which is measured from the multiplet splittings of an NMR spectrum. Radiofrequency irradiation on one coupled nuclear spin allows to modify the effective coupling constant, scaling down the multiplet splittings in the spectrum observed at the resonance frequency of the other nuclear spin. Such decoupling sequences are often used to collapse a multiplet into a singlet and can therefore simplify NMR spectra significantly. Continuous-wave (cw) decoupling has an intrinsic non-linear offset dependence of the scaling of the effective J-coupling constant. Using optimal control pulse optimization, we show that virtually arbitrary off-resonance scaling of the J-coupling constant can be achieved. The new class of tailored decoupling pulses is named SHOT (Scaling of Heteronuclear couplings by Optimal Tracking). Complementing cw irradiation, SHOT pulses offer an alternative approach of encoding chemical shift information indirectly through off-resonance decoupling, which however makes it possible for the first time to achieve linear J scaling as a function of offset frequency. For a simple mixture of eight aromatic compounds, it is demonstrated experimentally that a 1D-SHOT {(1)H}-(13)C experiment yields comparable information to a 2D-HSQC and can give full assignment of all coupled spins.
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Affiliation(s)
- Franz Schilling
- Department of Chemistry, Technische Universität München, 85747 Garching, Germany
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8
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Spindler PE, Zhang Y, Endeward B, Gershernzon N, Skinner TE, Glaser SJ, Prisner TF. Shaped optimal control pulses for increased excitation bandwidth in EPR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 218:49-58. [PMID: 22578555 DOI: 10.1016/j.jmr.2012.02.013] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 02/16/2012] [Accepted: 02/18/2012] [Indexed: 05/12/2023]
Abstract
A 1 ns resolution pulse shaping unit has been developed for pulsed EPR spectroscopy to enable 14-bit amplitude and phase modulation. Shaped broadband excitation pulses designed using optimal control theory (OCT) have been tested with this device at X-band frequency (9 GHz). FT-EPR experiments on organic radicals in solution have been performed with the new pulses, designed for uniform excitation over a significantly increased bandwidth compared to a classical rectangular π/2 pulse of the same B(1) amplitude. The concept of a dead-time compensated prefocused pulse has been introduced to EPR with a self-refocusing of 200 ns after the end of the pulse. Echo-like refocused signals have been recorded and compared to the performance of a classical Hahn-echo sequence. The impulse response function of the microwave setup has been measured and incorporated into the algorithm for designing OCT pulses, resulting in further significant improvements in performance. Experimental limitations and potential new applications of OCT pulses in EPR spectroscopy will be discussed.
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Affiliation(s)
- Philipp E Spindler
- Institut für physikalische und theoretische Chemie, Goethe Universität Frankfurt, Max von Laue Strasse 7, 60438 Frankfurt am Main, Germany.
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9
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Skinner TE, Gershenzon NI, Nimbalkar M, Glaser SJ. Optimal control design of band-selective excitation pulses that accommodate relaxation and RF inhomogeneity. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 217:53-60. [PMID: 22425442 DOI: 10.1016/j.jmr.2012.02.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 02/11/2012] [Accepted: 02/14/2012] [Indexed: 05/31/2023]
Abstract
Existing optimal control protocols for mitigating the effects of relaxation and/or RF inhomogeneity on broadband pulse performance are extended to the more difficult problem of designing robust, refocused, frequency selective excitation pulses. For the demanding case of T(1) and T(2) equal to the pulse length, anticipated signal losses can be significantly reduced while achieving nearly ideal frequency selectivity. Improvements in performance are the result of allowing residual unrefocused magnetization after applying relaxation-compensated selective excitation by optimized pulses (RC-SEBOPs). We demonstrate simple pulse sequence elements for eliminating this unwanted residual signal.
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Affiliation(s)
- Thomas E Skinner
- Physics Department, Wright State University, Dayton, OH 45435, USA.
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10
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Janich MA, Schulte RF, Schwaiger M, Glaser SJ. Robust slice-selective broadband refocusing pulses. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 213:126-135. [PMID: 21974997 DOI: 10.1016/j.jmr.2011.09.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 09/06/2011] [Accepted: 09/08/2011] [Indexed: 05/31/2023]
Abstract
Slice-selective broadband refocusing pulses are of great interest in localized MR spectroscopy for improving spatial selectivity, reducing chemical-shift displacement errors, and reducing anomalous J modulation. In practice the bandwidth of RF pulses is limited by the maximum available B1 amplitude. The goal of the present work is to design slice-selective and broadband refocusing pulses which are tolerant against B1 deviations. Pulse design is performed by numerical optimization based on optimal control theory. A comprehensive study of different cost functions and their effect on the optimization is given. The optimized slice-selective broadband refocusing pulses are compared to conventional Shinnar-Le Roux (SLR), broadband SLR, and hyperbolic secant pulses. In simulations and experiments optimized pulses were shown to fulfill broadband slice specifications over a range of ±20% B1 scalings. Experimental validation showed a reduction of chemical-shift displacement error by a factor of 3 compared to conventional SLR pulses.
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Affiliation(s)
- Martin A Janich
- Technische Universität München, Department of Chemistry, Munich, Germany
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11
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Braun M, Glaser SJ. Cooperative pulses. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 207:114-123. [PMID: 20869893 DOI: 10.1016/j.jmr.2010.08.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Revised: 08/05/2010] [Accepted: 08/19/2010] [Indexed: 05/29/2023]
Abstract
We introduce the concept of cooperative (COOP) pulses which are designed to compensate each other's imperfections. In multi-scan experiments, COOP pulses can cancel undesired signal contributions, complementing and generalizing phase cycles. COOP pulses can be efficiently optimized using an extended version of the optimal-control-based gradient ascent pulse engineering (GRAPE) algorithm. The advantage of the COOP approach is experimentally demonstrated for broadband and band-selective pulses.
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Affiliation(s)
- Michael Braun
- Department of Chemistry, Technische Universität München, 85747 Garching, Germany
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12
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Roth M, Koch A, Kindervater P, Bargon J, Spiess HW, Münnemann K. (13)C hyperpolarization of a barbituric acid derivative via parahydrogen induced polarization. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 204:50-55. [PMID: 20207180 DOI: 10.1016/j.jmr.2010.01.016] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 01/29/2010] [Accepted: 01/30/2010] [Indexed: 05/28/2023]
Abstract
Significant (13)C NMR signal enhancement by a factor of 5000 of a barbituric acid derivative (5-methyl-5-propenyl-barbituric acid) via parahydrogen induced polarization is presented. This hyperpolarization is achieved by hydrogenating 5-methyl-5-propargyl-barbituric acid with 98% enriched para-H(2) under elevated temperature and pressure and transferring the initially created (1)H hyperpolarization with an INEPT-derived pulse sequence to (13)C. The polarization can be selectively transferred to different carbons in the barbituric acid derivative by applying different pulse delays in the INEPT pulse sequence. These results demonstrate the potential of using hyperpolarized barbituric acid derivatives as "active" contrast agents in MRI and visualizing their pharmacokinetics in vivo.
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Affiliation(s)
- Meike Roth
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
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13
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Pomplun N, Glaser SJ. Exploring the limits of electron-nuclear polarization transfer efficiency in three-spin systems. Phys Chem Chem Phys 2010; 12:5791-8. [DOI: 10.1039/c003751f] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Neves JL, Heitmann B, Khaneja N, Glaser SJ. Heteronuclear decoupling by optimal tracking. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 201:7-17. [PMID: 19695913 DOI: 10.1016/j.jmr.2009.07.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Revised: 07/19/2009] [Accepted: 07/25/2009] [Indexed: 05/28/2023]
Abstract
The problem to design efficient heteronuclear decoupling sequences is studied using optimal control methods. A generalized version of the gradient ascent engineering (GRAPE) algorithm is presented that makes it possible to design complex non-periodic decoupling sequences which are characterized by tens of thousands of pulse sequence parameters. In contrast to conventional approaches based on average Hamiltonian theory, the concept of optimal tracking is used: a pulse sequence is designed that steers the evolution of an ensemble of spin systems such that at a series of time points, a specified trajectory of the density operator is tracked as closely as possible. The approach is demonstrated for the case of low-power heteronuclear decoupling in the liquid state for in vivo applications. Compared to conventional sequences, significant gains in decoupling efficiency and robustness with respect to offset and inhomogeneity of the radio-frequency field were found in simulations and experiments.
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Affiliation(s)
- Jorge L Neves
- Department of Chemistry, Technische Universität München, 85747 Garching, Germany
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15
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Tosner Z, Vosegaard T, Kehlet C, Khaneja N, Glaser SJ, Nielsen NC. Optimal control in NMR spectroscopy: numerical implementation in SIMPSON. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 197:120-34. [PMID: 19119034 DOI: 10.1016/j.jmr.2008.11.020] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2008] [Revised: 11/19/2008] [Accepted: 11/23/2008] [Indexed: 05/17/2023]
Abstract
We present the implementation of optimal control into the open source simulation package SIMPSON for development and optimization of nuclear magnetic resonance experiments for a wide range of applications, including liquid- and solid-state NMR, magnetic resonance imaging, quantum computation, and combinations between NMR and other spectroscopies. Optimal control enables efficient optimization of NMR experiments in terms of amplitudes, phases, offsets etc. for hundreds-to-thousands of pulses to fully exploit the experimentally available high degree of freedom in pulse sequences to combat variations/limitations in experimental or spin system parameters or design experiments with specific properties typically not covered as easily by standard design procedures. This facilitates straightforward optimization of experiments under consideration of rf and static field inhomogeneities, limitations in available or desired rf field strengths (e.g., for reduction of sample heating), spread in resonance offsets or coupling parameters, variations in spin systems etc. to meet the actual experimental conditions as close as possible. The paper provides a brief account on the relevant theory and in particular the computational interface relevant for optimization of state-to-state transfer (on the density operator level) and the effective Hamiltonian on the level of propagators along with several representative examples within liquid- and solid-state NMR spectroscopy.
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Affiliation(s)
- Zdenek Tosner
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, Aarhus C, Denmark.
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16
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Maximov II, Tošner Z, Nielsen NC. Optimal control design of NMR and dynamic nuclear polarization experiments using monotonically convergent algorithms. J Chem Phys 2008; 128:184505. [DOI: 10.1063/1.2903458] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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17
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Suter D, Mahesh TS. Spins as qubits: Quantum information processing by nuclear magnetic resonance. J Chem Phys 2008; 128:052206. [DOI: 10.1063/1.2838166] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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18
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Hansen JØ, Kehlet C, Bjerring M, Vosegaard T, Glaser SJ, Khaneja N, Nielsen NC. Optimal control based design of composite dipolar recoupling experiments by analogy to single-spin inversion pulses. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.08.072] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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19
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Kehlet C, Bjerring M, Sivertsen AC, Kristensen T, Enghild JJ, Glaser SJ, Khaneja N, Nielsen NC. Optimal control based NCO and NCA experiments for spectral assignment in biological solid-state NMR spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 188:216-30. [PMID: 17681479 DOI: 10.1016/j.jmr.2007.06.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2007] [Revised: 06/02/2007] [Accepted: 06/07/2007] [Indexed: 05/16/2023]
Abstract
We present novel pulse sequences for magic-angle-spinning solid-state NMR structural studies of (13)C,(15)N-isotope labeled proteins. The pulse sequences have been designed numerically using optimal control procedures and demonstrate superior performance relative to previous methods with respect to sensitivity, robustness to instrumental errors, and band-selective excitation profiles for typical biological solid-state NMR applications. Our study addresses specifically (15)N to (13)C coherence transfers being important elements in spectral assignment protocols for solid-state NMR structural characterization of uniformly (13)C,(15)N-labeled proteins. The pulse sequences are analyzed in detail and their robustness towards spin system and external experimental parameters are illustrated numerically for typical (15)N-(13)C spin systems under high-field solid-state NMR conditions. Experimentally the methods are demonstrated by 1D (15)N-->(13)C coherence transfer experiments, as well as 2D and 3D (15)N,(13)C and (15)N,(13)C,(13)C chemical shift correlation experiments on uniformly (13)C,(15)N-labeled ubiquitin.
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Affiliation(s)
- Cindie Kehlet
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, Langelandsgade 140, DK-8000, Aarhus C, Denmark
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20
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Tosner Z, Glaser SJ, Khaneja N, Nielsen NC. Effective Hamiltonians by optimal control: Solid-state NMR double-quantum planar and isotropic dipolar recoupling. J Chem Phys 2006; 125:184502. [PMID: 17115760 DOI: 10.1063/1.2366703] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report the use of optimal control algorithms for tailoring the effective Hamiltonians in nuclear magnetic resonance (NMR) spectroscopy through sophisticated radio-frequency (rf) pulse irradiation. Specifically, we address dipolar recoupling in solid-state NMR of powder samples for which case pulse sequences offering evolution under planar double-quantum and isotropic mixing dipolar coupling Hamiltonians are designed. The pulse sequences are constructed numerically to cope with a range of experimental conditions such as inhomogeneous rf fields, spread of chemical shifts, the intrinsic orientation dependencies of powder samples, and sample spinning. While the vast majority of previous dipolar recoupling sequences are operating through planar double-or zero-quantum effective Hamiltonians, we present here not only improved variants of such experiments but also for the first time homonuclear isotropic mixing sequences which transfers all I(x), I(y), and I(z) polarizations from one spin to the same operators on another spin simultaneously and with equal efficiency. This property may be exploited to increase the signal-to-noise ratio of two-dimensional experiments by a factor of square root 2 compared to conventional solid-state methods otherwise showing the same efficiency. The sequences are tested numerically and experimentally for a powder of (13)C(alpha),(13)C(beta)-L-alanine and demonstrate substantial sensitivity gains over previous dipolar recoupling experiments.
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Affiliation(s)
- Zdenek Tosner
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, DK-8000 Aarhus C, Denmark
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