Paramagnetic NMR for the characterization of biological systems has long been considered a niche of NMR, cultivated by a few specialists. In recent decades its broad applicability has become increasingly clear, and its use has largely spread. It is now commonly believed that NMR of paramagnetic systems represents an important part of NMR, both from the point of view of the theory and of its applications. Paramagnetic effects have in fact been shown to provide structural and dynamic information not available from other techniques. The number of NMR experiments exploiting paramagnetic probes has thus largely increased in the last years. While an increasing number of researchers is becoming interested in paramagnetism-based NMR, some still need to overcome a psychological barrier due to the belief that paramagnetism-based NMR experiments are difficult to perform. This book aims at lowering this barrier by covering the whole spectrum of experimental approaches and the many possibilities opened up by paramagnetism.

This book perfectly complements two other editorial works, one book published in 2017 and one extensive review to appear in 2018. The 2017 book (Bertini, Luchinat, Parigi, Ravera, NMR of paramagnetic molecules, Elsevier) covers both the basic theory and the potentialities offered by NMR for the structural and dynamic characterization of paramagnetic molecules of all kinds. This book capitalizes on previous books,¹ but is largely updated with respect to the previous editions. An review to appear in 2018 from A. J. Pell, G. Pintacuda and C. P. Grey is specifically focused on the theory of paramagnetic NMR. Some of the authors of these two other works are also authors of chapters of this book.

Here we aim to deliver a practical guide for experimentalists, and therefore this book has an experiment-based approach, rather than a theoretical approach. It features a wide overview of the paramagnetic NMR applications, providing details on the practical implementations of state-of-the-art experiments.

We took the burden—and the pleasure—to act as editors of this book because in our research infrastructure, the Magnetic Resonance Center (CERM) of the University of Florence, the field of NMR of paramagnetic molecules has been cultivated significantly for many decades. This exposed us to many interesting problems in different application fields, and to exchanges of ideas with many experts all over the world, among which we selected a few as authors of the chapters of this book. The topics were chosen in order to cover the main applications of paramagnetic NMR in life sciences: from the selection and attachment of paramagnetic tags (Chapter 2) to the description of the protocols for molecular structure determination (Chapter 3) and characterization of conformational variability (Chapter 4); from the study of protein–protein interactions (Chapter 5) and of paramagnetic solid-state systems (Chapter 6) to relaxometry (Chapter 7); from dynamic nuclear polarization (Chapter 8) to drug discovery (Chapter 9) and the use of paramagnetic co-solute molecules (Chapter 10). Chapter 1 introduces the readers to the principles of paramagnetism and to the equations describing the effects of paramagnetism on NMR spectra.

The authors of the chapters were selected among researchers who are worldwide experts in the topics that they present, and we hope the readers will agree that all of them have done an excellent job. Among the authors are some of the partners of the EC Marie Curie ITN program ‘pNMR’, aimed at ‘Pushing the Envelope of Nuclear Magnetic Resonance Spectroscopy for Paramagnetic Systems’ (grant agreement no. 317127, 2013–2016), who authored Chapters 1, 4, 5 and 6.

We did our best to ensure that this book is a real book and not a collection of review articles. We have thus asked all authors to use the same symbols, abbreviations and terminology, and to extensively cross-refer to the other chapters of the book, in order to minimize repetitions and make links evident. We thank all authors for their excellent work and also for helping us in this, thus making our editorial work easier and pleasurable.

Claudio Luchinat

Giacomo Parigi

Enrico Ravera