Bo Chen, Ph.D., is Associate Professor of Physics at the University of Central Florida. His NMR lab focuses on how to apply and develop techniques to investigate the structure and dynamics of biomacromolecular assemblies, and to develop novel coarse-grain models to understand the self-assembly mechanism. He is the recipient of the AFOSR Young Investigator Award. Previously, Professor Chen was a Research Fellow at the National Institutes of Health.
Frontmatter
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Published:2020
Bo Chen, "Frontmatter", Fundamentals of Recoupling and Decoupling Techniques in Solid State NMR, Bo Chen
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Fundamentals of Recoupling and Decoupling Techniques in Solid State NMR provides broad coverage from the fundamentals through updated recoupling and decoupling techniques. It details step by step derivations and teaches readers how solid state NMR with Magic Angle Spinning exploits the interplay between mechanical rotation and radio frequency (RF) pulses to actively switch on (recoupling) and off (decoupling) desired interactions.
This unique book offers:
Coverage from the basic through advanced topics and incorporates step by step derivations and exercises
Conceptual, experimental, and mathematical aspects of modern solidstate NMR
Detailed instruction of tensor calculus and step-by-step derivation to help students learn magic angle spinning phase integration
This book is ideal for upper level undergraduate students majoring in physics or a related discipline and practicing physicists interested in learning more about this topic.
PREFACE
Over 60 years ago, Andrew and Lowe introduced magic angle spinning (MAS) to suppress dipolar interactions. Since then, numerous theoretical and experimental developments have sprouted around this operation. Now, solid state NMR (ssNMR) with MAS has become a powerful tool to study molecular motion and structure in biophysics, as well as electromagnetic properties in materials sciences and physics.
Essentially, ssNMR with MAS exploits the interplay between mechanical rotation and radio frequency (RF) pulses, to actively switch on (recouple) and off (decouple) desired interactions. This intimate interplay has created an extra dimension of challenge for the theoretical treatment of pulse sequences, as this requires a good foundation in quantum mechanics. In most publications on ssNMR methods, normally only concise steps are presented in the derivations, as readers are assumed to be familiar with the topics. While plenty of excellent reviews and textbooks are available, various intermediate steps are usually omitted, to either conserve space or because they are deemed too trivial. Consequently, technical papers about ssNMR are not easy for beginners to understand, even those with a solid background in physics. Meanwhile, owing to its unique capability, ssNMR now appeals to users from a wide range of backgrounds, who may have limited physics education. Hence, as one of the basic essentials of ssNMR techniques, understanding the mechanism of recoupling and decoupling can be a rather intimidating obstacle for many. It would be of great help for beginners if these basics are explained in greater detail.
Therefore, I wrote this book for students interested in ssNMR in biophysics, during my sabbatical in Spring 2019, especially with this consideration in mind. We start with the most fundamental concepts in NMR. Topics such as basic probe design principles and relaxations are also gently touched to provide a general knowledge background. After discussing various transformations of reference frames, we introduce density matrix and product operator formalism, and explain a number of classical pulse sequences for stationary samples. Following this, we discuss irreducible spherical tensors and Wigner rotation matrix for the convenient and unified treatment of rotations in both physical and spin space. Based on this platform, we move on to compute the Hamiltonians of various interactions to illustrate the effect of MAS. Subsequently, we explain the mechanisms for a series of popular recoupling and decoupling pulse sequences in ssNMR on the basis of average Hamiltonian theory. We introduce the principles of Floquet theory at the end to treat more sophisticated interference effects between RF irradiation and MAS. In this process, whenever possible, we provide step-by-step derivations, so that intermediate steps in derivations are transparent for someone with a background in undergraduate physics or a relevant discipline.
Readers can easily recognize that this book is loosely based on a number of classic papers, and chapters from classic NMR textbooks, which are acknowledged at the beginning of each chapter. These excellent publications form the backbone to my writing. Or, conversely, we could say that this book provides supporting information for the original material. My sole intention is to accelerate the learning of the principles of recoupling and decoupling techniques for beginners, using these publications as templates. However, the selected publications are not meant to represent the importance of their contributions to the field. Rather, they are merely a reflection of my personal learning trajectory and experience, which is rather limited. Inevitably, I have to apologize for the errors and mistakes in the book, and advice and criticism will be greatly appreciated.
This book would not be possible without the support of my dear wife, Yan. During this challenging pandemic, when two kids are at home and both of us have to work, she directs more efforts to entertain and educate them, while I could entertain and educate myself writing this book.
I am also extremely grateful for the support during my sabbatical in 2019 by University of Central Florida, so I could pluck up enough courage and time to start the journey to review all the literature. Finally, I would like to acknowledge Dr. Matthias Ernst's warm help to understand Floquet theory.
Bo Chen
2019 Summer
Orlando, Florida, USA