Aromatic ring flips in differently packed protein crystals: MAS NMR and MD studies of 3 ubiquitin lattices

Probing the dynamics of aromatic side chains provides important insights into the behavior of a protein because flips of aromatic rings in a protein’s hydrophobic core report on breathing motion involving large part of the protein. Inherently invisible to crystallography, aromatic motions have been primarily studied by solution NMR. Here we apply magic-angle spinning NMR, advanced phenylalanine 1H-13C/2H isotope labeling and molecular simulations to a protein in three different crystal packing environments to shed light onto possible impact of packing on ring flips. We find that ring flips in ubiquitin are quite conserved in the different crystal forms, even though the intermolecular packing is quite different suggesting that intramolecular influences are more important than intermolecular (packing) effects. ### Competing Interest Statement The authors have declared no competing interest.