Concepts in Magnetic Resonance Part A最新文献

{"title":"A special issue in honor of the late Professor Alex D. Bain (1948-2016)","authors":"William F. Reynolds PhD, Eugene P. Mazzola PhD, Roderick E. Wasylishen PhD","doi":"10.1002/cmr.a.21421","DOIUrl":"10.1002/cmr.a.21421","url":null,"abstract":"<p>The NMR community lost one of its most brilliant and original thinkers when Alex Bain died in late 2016. Many of his friends and former colleagues felt that Alex deserved some form of special recognition in view of his many contributions to NMR, both in Canada and elsewhere. Since Alex had published a number of important articles in <i>Concepts in Magnetic Resonance</i> and also served on the Editorial Board of Concepts, it was decided that a special issue of this journal in his honor would be an appropriate form of recognition of Alex's accomplishments, and three of us agreed to be Guest Editors for the issue.</p><p>Alex Bain graduated with a double Honors B.Sc. in Mathematics and Chemistry from the University of Toronto in 1970. He then received a National Research Council of Canada Fellowship for M.Sc. studies at the University of British Columbia where he carried out research on photoelectron spectroscopy. Next, he received a Shell Canada Fellowship for Ph.D. studies at Cambridge University. There he began his NMR career, working with Dr. Ruth Lynden-Bell. Returning to Canada in 1974, a time when full-time academic positions in Chemistry were few and far between, he first had an NRC Postdoctoral Fellowship with Professor John Martin at the University Alberta, followed by a series of limited term appointments at McMaster University and the Scarborough Campus of the University of Toronto. Finally, in 1980, Bruker Canada hired him as research scientist with particular responsibility for NMR programming, including for 2D NMR. He remained there until 1987 when McMaster attracted him back as an Associate Professor and later he became a Full Professor. In 2008, due to health concerns, he opted for early retirement to become an Emeritus Professor. However, he still kept very active in research, both at McMaster and as an unpaid research associate in Lewis Kay's group at Toronto. His contributions there are described in the article by Lewis.</p><p>Alex's research combined a strong desire to fully understand complex NMR phenomena with a knowledge and depth of understanding of advanced mathematical methods relevant to NMR that very few in the NMR community could match. Thus, use of Liouvillian operators, Floquet theory and sparse matrices featured prominently in his research. His Ph.D. research included elucidation of alternative relaxation pathways in heteronuclear AX<sub>2</sub> and AX<sub>3</sub> spin systems, knowledge that is still used today by Lewis Kay and others in designing 3D and 4D pulse sequences for protein NMR research. His Postdoctoral research included the use of Liouvillian operators to calculate NMR transitions. During his first spell at McMaster, he pioneered the use of Superspin to simulate 2D spectra. He also programmed a borrowed computer from a Nicolet FT-IR spectrometer to acquire and process 2D data on a Bruker spectrometer. This is what likely led to his job offer from Bruker. While at Bruker, he published a very useful pap","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"45A 6","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21421","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80174019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spin precession: A spin-1 case study using irreducible tensor operators","authors":"David J. Siminovitch","doi":"10.1002/cmr.a.21411","DOIUrl":"10.1002/cmr.a.21411","url":null,"abstract":"<p>Using a Cartesian operator basis set, precession equations have previously been derived for spin-1 systems using some 23 Cartesian operator commutators. We avoid the explicit evaluation of these commutators, and use instead fundamental properties of irreducible tensor operators (ITO) to obtain these precession equations. First, advantage is taken of the angle-axis parametrization of the rotation matrices that transform second-rank ITO under rotation to define the unitarily equivalent rotation matrix that transforms second-rank Cartesian tensors. From this latter transformation, and using simple matrix analysis techniques, all the equations that describe spin-1 precession in the presence of radiofrequency fields and resonance offsets are obtained. Second, information on the ITO commutation relations can be encoded in angular momentum coupling coefficients in a generalized spin precession equation. In the case of spin-1, this leads to a set of coupled differential equations for the statistical tensor components . After transformation of these components to their Cartesian counterparts, the corresponding vector differential equations that define the time evolution of the Cartesian operator expectation values are easily solved, again using simple matrix analysis. This solution yields all the equations that describe spin-1 precession in the presence of radiofrequency fields, resonance offsets, and the quadrupolar interaction.</p>","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"45A 6","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21411","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81924358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The use of indirectly bonded 13C-1H (INCH) shift correlation spectra for ab initio structure elucidation of natural products and other complex organic compounds; A personal and historical perspective","authors":"William F. Reynolds","doi":"10.1002/cmr.a.21413","DOIUrl":"10.1002/cmr.a.21413","url":null,"abstract":"<p>This article reviews the use of long-range shift correlation spectra for structure elucidation of natural products and other complex organic compounds from the early 1980's to the present. Much of it is written from the personal viewpoint of someone who has been involved in this area of research since its earliest days. The first section covers the early use of long-range correlation spectra in the 1980's. The second section covers the development of specialized pulse sequences for this type of acquisition. It begins with three ¹³C-detected sequences, followed by heteronuclear multiple bond correlation (HMBC) and some modified versions of HMBC and, finally, longer range correlation sequences based on the heteronuclear single quantum multiple bond correlation sequence. The third section covers various sequences designed to distinguish between 2-bond and longer range ¹³C-¹H correlations. Unfortunately, none of these can make this distinction for non-protonated carbons. Only the 1,1-ADEQUATE sequence can make this distinction but its very low sensitivity limits its usefulness. The next section focuses on ways of avoiding getting incorrect structures of organic compounds, an ongoing problem in natural product research. The last section includes likely short-term developments and possible long-term developments in NMR methodology that would be beneficial for small molecule structure elucidation.</p>","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"45A 6","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21413","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78495064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Systematic image alteration due to phase accumulation during RF pulse excitation in pure phase encode magnetic resonance imaging","authors":"Tess McDonald,&nbsp;Bryce MacMillan,&nbsp;Ben Newling,&nbsp;Bruce J. Balcom","doi":"10.1002/cmr.a.21425","DOIUrl":"10.1002/cmr.a.21425","url":null,"abstract":"<p>The SPI/SPRITE class of techniques in magnetic resonance imaging are pure phase encode methods that are well established for systems with short transverse signal lifetimes. Applying a broadband radio-frequency pulse in the presence of a magnetic field gradient is unconventional in MRI but fundamental to these methods. Ordinarily, it is assumed that the excitation is instantaneous and any possible phase evolution during the RF pulse is ignored. High quality, quantitative imaging of a variety of samples over many years suggests that the off-resonance effects of the RF pulse, with consequent phase accumulation during the pulse, are not significant. However, a reconsideration of the RF pulse behavior in related work has shown that phase accumulation during the pulse may be non-negligible in some circumstances.</p><p>The effect of phase accumulation during the RF pulse is investigated through simulation of one-dimensional SPI experiments and is shown to manifest as a systematic scaling of the image field-of-view (FOV). The FOV scaling effect is also verified experimentally. One-dimensional profiles of a cylindrical elastomer sample were acquired employing a 2.4 T horizontal bore magnet. Experiments were undertaken with variation of the experimental RF pulse duration. Under typical experimental parameters, neglecting the phase accumulation during the RF pulse is acceptable.</p>","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"45A 6","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21425","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86762828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Two-pulse frequency-hopped excitation","authors":"Carl A. Michal,&nbsp;Ronald Y. Dong","doi":"10.1002/cmr.a.21416","DOIUrl":"10.1002/cmr.a.21416","url":null,"abstract":"<p>The use of frequency-hopped pulse pairs and pulse pair trains for exciting NMR signals is introduced. Pairs of pulses, each pair lasting one nutation period about the effective field in the rotating frame, can be used to efficiently tip nuclear spin magnetization. In the limit where the frequency difference between the partners in a pair is large, the magnetization dynamics mimic those of an ordinary rectangular rf pulse with rf amplitude scaled down by a factor of π/2. When the amplitude of the applied rf begins to approach the offset frequency however, the excitation bandwidth broadens dramatically in a manner reminiscent of a composite pulse. The effects of the frequency-hopped pulse pairs is described with analytical calculations and numerical simulations, and are shown to agree well with experiment.</p>","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"45A 6","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21416","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82893163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Solid-state nuclear magnetic resonance and nuclear quadrupole resonance as complementary tools to study quadrupolar nuclei in solids","authors":"Patrick M.J. Szell,&nbsp;David L. Bryce","doi":"10.1002/cmr.a.21412","DOIUrl":"10.1002/cmr.a.21412","url":null,"abstract":"<p>Solid-state nuclear magnetic resonance (SSNMR) spectroscopy has largely overtaken nuclear quadrupole resonance (NQR) spectroscopy for the study of quadrupolar nuclei. In addition to information on the electric field gradient, SSNMR spectra may offer additional information concerning other NMR interactions such as magnetic shielding. With continued technological advances contributing to developments such as higher magnetic fields, SSNMR boasts several practical advantages over NQR. However, NQR is still a relevant technique, as it may often be the most practical approach in cases of extremely large quadrupolar coupling constants. Here, we discuss the advantages and disadvantages of SSNMR and NQR spectroscopies, with the quadrupolar halogens serving as examples. The purpose of this article is to serve as a guide on using SSNMR and NQR as complementary tools, covering some of their practicalities, limitations, and experimental challenges.</p>","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"45A 6","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21412","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80592574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"NMR Concepts","authors":"","doi":"10.1002/cmr.a.21432","DOIUrl":"https://doi.org/10.1002/cmr.a.21432","url":null,"abstract":"","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"45A 6","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21432","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91884374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Introduction to average Hamiltonian theory. I. Basics","authors":"Andreas Brinkmann","doi":"10.1002/cmr.a.21414","DOIUrl":"10.1002/cmr.a.21414","url":null,"abstract":"<p>Understanding the dynamics of electron or nuclear spins during a magnetic resonance experiment requires to solve the Schrödinger equation for the spin system considering all contributions to the Hamiltonian from interactions of the spins with each other and their surroundings. In general, this is a difficult task as these interaction terms can be both time-dependent and might not commute with each other. A powerful tool to analytically approximate the time evolution is average Hamiltonian theory, in which a time-independent effective Hamiltonian is taking the place of the time-dependent Hamiltonian. The effective Hamiltonian is subjected to the Magnus expansion, allowing to calculate the effective Hamiltonian to a certain order. The goal of this paper is to introduce average Hamiltonian theory in a rigorous but educational manner. The application to two composite pulses in NMR spectroscopy is used to demonstrate important aspects of average Hamiltonian theory.</p>","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"45A 6","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21414","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72915387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A magnet moment silenced: A tribute to my friend and mentor Alex D. Bain","authors":"Lewis E. Kay","doi":"10.1002/cmr.a.21420","DOIUrl":"10.1002/cmr.a.21420","url":null,"abstract":"<p>Alex D. Bain was an exceptional NMR spectroscopist who played an important role in the development of modern NMR methods and whose keen intellect and wonderful personal qualities endeared him to faculty and students alike who often sought him out for NMR advice. In this brief recollection, I will focus on a number of seminal contributions that Alex made that greatly influenced my research, illustrating how they changed the practice of modern NMR spectroscopy and laid the foundation for new experiments that are currently in widespread use.</p>","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"45A 6","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21420","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72925407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dependence of electron paramagnetic resonance spectral lineshapes on molecular tumbling: Nitroxide radical in water:glycerol mixtures","authors":"Ashley Clark,&nbsp;Jessica Sedhom,&nbsp;Hanan Elajaili,&nbsp;Gareth R. Eaton,&nbsp;Sandra S. Eaton","doi":"10.1002/cmr.a.21423","DOIUrl":"10.1002/cmr.a.21423","url":null,"abstract":"<p>Electron paramagnetic resonance spectra of nitroxide radicals are reporters of molecular tumbling correlation times. The concepts of electron paramagnetic resonance and molecular tumbling are demonstrated by examination of spectra of the radical tempol (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl) in water:glycerol mixtures. Analysis of the spectral line shapes with the Kivelson model and computer simulation with EasySpin are discussed. Values of the tumbling correlation times obtained by the two methods are shown to be in good agreement. Comparison of the experimental tumbling correlation times with values calculated with the Stokes-Einstein model indicates a slip coefficient of 0.066, which is consistent with other reports for nitroxides in various solvents.</p>","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"45A 5","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21423","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77120882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}