Article
Author contributions Y.L. cloned and expressed all FACT constructs with the help of K.Z.
K.Z. and Y.L. optimized sample and grid preparation and performed extensive screening.
H.W. and Z.Z. (with B.C. and C.S.P.) optimized the conditions for Chameleon/Spotiton
vitrification. H.W. collected the data. Y.Z.T., H.W. and K.Z. analysed the electron-microscopy
data and obtained the electron-density maps, with input from B.C. and C.S.P. K.Z. modelled
and refined the structures. K.Z., Y.L. and K.L. interpreted electron-microscopy structures
and drafted the manuscript. Y.L. designed and performed all biochemical assays, with input
from K.Z. and K.L. N.Z. (with input from Y.L.) designed HDX experiments, with the help of
S.D. and K.L. N.Z. and S.D. performed HDX experiments and analysed HDX data. Y.L., K.Z.,
S.D. and K.L. wrote the manuscript and prepared the figures.
Competing interests B.C. and S.C.P. have an intellectual property licensing arrangement with
TTP Labtech Ltd for the Chameleon sample vitrification instrument.
Additional information
Supplementary information is available for this paper at https://doi.org/10.1038/s41586-019-
1820-0.
Correspondence and requests for materials should be addressed to K.L.
Peer review information Nature thanks Tim Formosa, Karl-Peter Hopfner, Hitoshi Kurumizaka
and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Reprints and permissions information is available at http://www.nature.com/reprints.