PENELOP NMR Method

PENELOP (Paramagnetic Equilibrium vs Nonequilibrium magnetization Enhancement or LOss Perturbation) is a versatile NMR technique designed to simultaneously map proteins’ exposed or hindered surface accessibility and exchange processes occurring on a micro-to-millisecond  time scale. The method works by acquiring two sets of spectra—one under equilibrium conditions using a long recovery delay and another under off-equilibrium conditions, i.e. with a short recovery delay, both in the presence and absence of a water-soluble paramagnetic probe such as Tempol, that does not interact specifically or bind to the protein. By comparing normalized signal attenuations, it is possible to identify Type I patterns, which highlight hindered or buried surfaces, and Type II patterns, which reveal accelerated magnetization recovery caused by conformational or chemical exchange dynamics. The primary advantages of PENELOP arise from its exceptional sensitivity and speed, enabling the characterization of proteins at very low, physiologically significant concentrations (down to 4 µM) where more demanding techniques such as CEST or relaxation dispersion may prove prohibitively slow or ineffective. PENELOP is therefore a powerful tool for investigating complex biological phenomena such as protein aggregation, oligomerization, and assembly into large complexes similar to SARS-CoV-2 replication complex.