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{"title":"稳态条件下的异核极化转移:INEPT-SSFP 实验","authors":"Rihards Aleksis, Elton T. Montrazi, Lucio Frydman","doi":"10.1021/acs.jpclett.4c02016","DOIUrl":null,"url":null,"abstract":"NMR finds a wide range of applications, ranging from fundamental chemistry to medical imaging. The technique, however, has an inherently low signal-to-noise ratio (SNR)─particularly when dealing with nuclei having low natural abundances and/or low γs. In these cases, sensitivity is often enhanced by methods that, similar to INEPT, transfer polarization from neighboring <sup>1</sup>Hs via <i>J</i>-couplings. In 1958, Carr proposed an alternative approach to increase NMR sensitivity, which involves generating and continuously detecting a steady-state transverse magnetization, by applying a train of pulses on an ensemble of noninteracting spins. This study broadens Carr’s steady-state free precession (SSFP) framework to encompass the possibility of adding onto it coherent polarization transfers, allowing one to combine the SNR-enhancing benefits of both INEPT and SSFP into a single experiment. Herein, the derivation of the ensuing INEPT-SSFP (ISSFP) sequences is reported. Their use in <sup>13</sup>C NMR and MRI experiments leads to ca. 300% improvements in SNR/ <i></i><span style=\"color: inherit;\"></span><span data-mathml='<math xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\" overflow=\"scroll\"><msqrt><mrow><mi mathvariant=\"normal\">unit time</mi></mrow></msqrt></math>' role=\"presentation\" style=\"position: relative;\" tabindex=\"0\"><nobr aria-hidden=\"true\"><span overflow=\"scroll\" style=\"width: 5.003em; display: inline-block;\"><span style=\"display: inline-block; position: relative; width: 4.548em; height: 0px; font-size: 110%;\"><span style=\"position: absolute; clip: rect(1.026em, 1004.55em, 2.616em, -999.997em); top: -2.156em; left: 0em;\"><span><span><span style=\"display: inline-block; position: relative; width: 4.548em; height: 0px;\"><span style=\"position: absolute; clip: rect(3.128em, 1003.58em, 4.151em, -999.997em); top: -3.974em; left: 0.912em;\"><span><span><span style=\"font-family: STIXMathJax_Main;\">unit time</span></span></span><span style=\"display: inline-block; 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width: 0px; height: 3.98em;\"></span></span></span></span></span><span style=\"display: inline-block; width: 0px; height: 2.162em;\"></span></span></span><span style=\"display: inline-block; overflow: hidden; vertical-align: -0.372em; border-left: 0px solid; width: 0px; height: 1.503em;\"></span></span></nobr><span role=\"presentation\"><math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msqrt><mrow><mi mathvariant=\"normal\">unit time</mi></mrow></msqrt></math></span></span><script type=\"math/mml\"><math display=\"inline\" overflow=\"scroll\"><msqrt><mrow><mi mathvariant=\"normal\">unit time</mi></mrow></msqrt></math></script> over conventional <i>J</i>-driven polarization transfer experiments, and sensitivity gains of over 50% over <sup>13</sup>C SSFP performed in combination with <sup>1</sup>H decoupling and NOE. These enhancements match well with numerical simulations and analytical evaluations. The conditions needed to optimize these new methods in both spectroscopic and imaging studies are discussed; we also examine their limitations, and the valuable vistas that, in both analytical and molecular imaging NMR, could be opened by this development.","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":null,"pages":null},"PeriodicalIF":4.8000,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Heteronuclear Polarization Transfer under Steady-State Conditions: The INEPT-SSFP Experiment\",\"authors\":\"Rihards Aleksis, Elton T. Montrazi, Lucio Frydman\",\"doi\":\"10.1021/acs.jpclett.4c02016\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"NMR finds a wide range of applications, ranging from fundamental chemistry to medical imaging. The technique, however, has an inherently low signal-to-noise ratio (SNR)─particularly when dealing with nuclei having low natural abundances and/or low γs. In these cases, sensitivity is often enhanced by methods that, similar to INEPT, transfer polarization from neighboring <sup>1</sup>Hs via <i>J</i>-couplings. In 1958, Carr proposed an alternative approach to increase NMR sensitivity, which involves generating and continuously detecting a steady-state transverse magnetization, by applying a train of pulses on an ensemble of noninteracting spins. This study broadens Carr’s steady-state free precession (SSFP) framework to encompass the possibility of adding onto it coherent polarization transfers, allowing one to combine the SNR-enhancing benefits of both INEPT and SSFP into a single experiment. Herein, the derivation of the ensuing INEPT-SSFP (ISSFP) sequences is reported. Their use in <sup>13</sup>C NMR and MRI experiments leads to ca. 300% improvements in SNR/ <i></i><span style=\\\"color: inherit;\\\"></span><span data-mathml='<math xmlns=\\\"http://www.w3.org/1998/Math/MathML\\\" display=\\\"inline\\\" overflow=\\\"scroll\\\"><msqrt><mrow><mi mathvariant=\\\"normal\\\">unit time</mi></mrow></msqrt></math>' role=\\\"presentation\\\" style=\\\"position: relative;\\\" tabindex=\\\"0\\\"><nobr aria-hidden=\\\"true\\\"><span overflow=\\\"scroll\\\" style=\\\"width: 5.003em; display: inline-block;\\\"><span style=\\\"display: inline-block; position: relative; width: 4.548em; height: 0px; font-size: 110%;\\\"><span style=\\\"position: absolute; clip: rect(1.026em, 1004.55em, 2.616em, -999.997em); top: -2.156em; left: 0em;\\\"><span><span><span style=\\\"display: inline-block; position: relative; width: 4.548em; height: 0px;\\\"><span style=\\\"position: absolute; clip: rect(3.128em, 1003.58em, 4.151em, -999.997em); top: -3.974em; left: 0.912em;\\\"><span><span><span style=\\\"font-family: STIXMathJax_Main;\\\">unit time</span></span></span><span style=\\\"display: inline-block; 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Heteronuclear Polarization Transfer under Steady-State Conditions: The INEPT-SSFP Experiment
NMR finds a wide range of applications, ranging from fundamental chemistry to medical imaging. The technique, however, has an inherently low signal-to-noise ratio (SNR)─particularly when dealing with nuclei having low natural abundances and/or low γs. In these cases, sensitivity is often enhanced by methods that, similar to INEPT, transfer polarization from neighboring 1 Hs via J -couplings. In 1958, Carr proposed an alternative approach to increase NMR sensitivity, which involves generating and continuously detecting a steady-state transverse magnetization, by applying a train of pulses on an ensemble of noninteracting spins. This study broadens Carr’s steady-state free precession (SSFP) framework to encompass the possibility of adding onto it coherent polarization transfers, allowing one to combine the SNR-enhancing benefits of both INEPT and SSFP into a single experiment. Herein, the derivation of the ensuing INEPT-SSFP (ISSFP) sequences is reported. Their use in 13 C NMR and MRI experiments leads to ca. 300% improvements in SNR/ unit time ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ ⎯ √ unit time over conventional J -driven polarization transfer experiments, and sensitivity gains of over 50% over 13 C SSFP performed in combination with 1 H decoupling and NOE. These enhancements match well with numerical simulations and analytical evaluations. The conditions needed to optimize these new methods in both spectroscopic and imaging studies are discussed; we also examine their limitations, and the valuable vistas that, in both analytical and molecular imaging NMR, could be opened by this development.