This paper is part of the Proceedings of the 12th International Conference on Retinal Proteins held at Awaji Island, Hyogo, Japan, on 4–8 June 2006.
Preparation of Large Crystals of Photoactive Yellow Protein for Neutron Diffraction and High Resolution Crystal Structure Analysis†
Article first published online: 27 FEB 2007
Photochemistry and Photobiology
Volume 83, Issue 2, pages 336–338, March/April 2007
How to Cite
Yamaguchi, S., Kamikubo, H., Shimizu, N., Yamazaki, Y., Imamoto, Y. and Kataoka, M. (2007), Preparation of Large Crystals of Photoactive Yellow Protein for Neutron Diffraction and High Resolution Crystal Structure Analysis. Photochemistry and Photobiology, 83: 336–338. doi: 10.1562/2006-07-23-RA-977
- Issue published online: 27 FEB 2007
- Article first published online: 27 FEB 2007
- Received 23 July 2006; accepted 12 October 2006; published online 17 October 2006
The exact positions of all the hydrogen atoms in photoactive yellow protein (PYP) is important for understanding the molecular mechanism of the photoreaction because the protonation/deprotonation of certain amino acid residues and rearrangements in the hydrogen bond network are involved in the conformational changes of PYP. Neutron crystallography is one of the most effective methods to determine the hydrogen positions. However, a large crystal is required for neutron crystallography because a neutron-incident flux is quite limited. In addition, the crystal should be grown from heavy water to reduce the incoherent background from hydrogen. We prepared a large crystal of PYP (dimensions: 1.5 × 0.7 × 0.7 mm3) for neutron crystallography using ammonium sulfate with sodium chloride. The obtained large crystal gave X-ray diffraction spots up to 0.84 Å. Although some of the hydrogen atoms could be observed in the high resolution X-ray crystal structure, functionally important hydrogen atoms were impossible to see, indicating the importance of neutron crystallography. Thus, we optimized the crystallization conditions with heavy water and successfully obtained neutron diffraction spots up to 2.1 Å with the crystal in D2O.