RT Journal Article
SR Electronic
T1 Effects of cryo-EM cooling on structural ensembles
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2021.10.08.463658
DO 10.1101/2021.10.08.463658
A1 Lars V. Bock
A1 Helmut Grubmüller
YR 2021
UL http://biorxiv.org/content/early/2021/10/08/2021.10.08.463658.abstract
AB Structure determination by cryo electron microscopy (cryo-EM) provides information on structural heterogeneity and ensembles at atomic resolution. To obtain cryo-EM images of macromolecules, the samples are first rapidly cooled down to cryogenic temperatures. To what extent the structural ensemble is perturbed by the cooling is currently unknown. Here, to quantify the effects of cooling, we combined continuum model calculations of the temperature drop, molecular dynamics simulations of a ribosome complex before and during cooling with kinetic models. Our results suggest that three effects markedly contribute to the narrowing of the structural ensembles: thermal contraction, reduced thermal motion within local potential wells, and the equilibration into lower free-energy conformations by overcoming separating free-energy barriers. During cooling, barrier heights below 10 kJ/mol were found to be overcome resulting in reduction of B-factors in the ensemble imaged by cryo-EM. Our approach now enables the quantification of the heterogeneity of room-temperature ensembles from cryo-EM structures.Competing Interest StatementThe authors have declared no competing interest.