Advances in Biomolecular EPR, Volume 666 in the Methods of Enzymology series, highlights new advances in the field, with this new volume presenting interesting chapters on topics including Magnetic Resonance Characterization of Physiologically Important Metal Ion Binding Sites in the Prion and Related Proteins, The catalytic role of metal-radical/protein-based radicals in heme enzymes, Rigid Cu2+-based spin labels for the study of higher-order DNA G-quadruplex structures, Orthogonal spin labeling and membrane proteins: increasing the information content and going towards in cell applications, Spectroscopic investigation of mono- and di-Mn-containing centers in biochemistry with an emphasis on application of paramagnetic resonance techniques, and more. Additional chapters cover In Vivo pO2 Imaging of Tumors: Oxymetry with Very Low-Frequency Electron Paramagnetic Resonance, an Update, EPR contributions to understanding molybdenum-containing enzymes, EPR spectroscopy of Type I reaction centers, Characterization of a substrate-derived radical in the NosN reaction during the biosynthesis of nosiheptide, and much more.