Methods used in the structure determination of bovine mitochondrial F1 ATPase

TLDR

The F(1) ATPase particle, weighing 372 kDa, is the largest asymmetric structure solved to date. Structure determination relied on isomorphous differences from methyl‑mercury nitrate treatment, meticulous data collection and processing, and a novel solvent‑flipping electron‑density modification that inverts solvent density rather than flattening it.

Abstract

With a size of 372 kDa, the F(1) ATPase particle is the largest asymmetric structure solved to date. Isomorphous differences arising from reacting the crystals with methyl-mercury nitrate at two concentrations allowed the structure determination. Careful data collection and data processing were essential in this process as well as a new form of electron-density modification, 'solvent flipping'. The most important feature of this new procedure is that the electron density in the solvent region is inverted rather than set to a constant value, as in conventional solvent flattening. All non-standard techniques and variations on new techniques which were employed in the structure determination are described.