Trehalose embedding technique for high-resolution electron crystallography: application to structural study on bacteriorhoposin

Trehalose was compared with glucose in its use as an embedding medium for t he preparation of two-dimensional crystals for electron crystallographic st ructure analysis. Purple membranes (two-dimensional crystals of bacteriorho dopsin) embedded in either sugar were studied in a 'partially hydrated' sta te as well as after 'drying' of the specimen. Diffraction patterns of the f our conditions, all showing spots to a resolution better than 3.0 Angstrom, were analysed and merged. In the case of glucose embedded specimens, the m erging R-factor obtained from the diffraction patterns of dried specimens w as significantly better than the one obtained from partially hydrated speci mens. In the case of trehalose embedding, the merging R-factor for partiall y hydrated specimens was significantly better than the dried one. The treha lose embedded, partially hydrated specimens gave the best merging R-factor in all four cases.