Paramagnetic tagging for protein structure and dynamics analysis

Researchers have developed paramagnetic tagging for protein structure and dynamics analysis by using Nuclear Magnetic Resonance (NMR) spectra. They have demonstrated that paramagnetic centers are characterized by two properties that determine the type of restraints they generate. It has been observed that centers with slow electronic relaxation cause strong Paramagnetic Relaxation Enhancement (PRE), while the effect of centers with fast electronic relaxation on nuclear relaxation is much smaller. The anisotropy of the paramagnetic effect, described by the magnetic susceptibility tensor, causes line shifts, along with partial alignment of molecules in strong magnetic fields. A variety of paramagnetic tags has been developed and improved, each with its own properties. The simplest and most widely used paramagnetic tags are the nitroxide spin labels.