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Volume 16, Issue 3-4, Pages 127-138

The Use of the Time-Resolved X-Ray Solution Scattering for Studies of Globular Proteins

Kunihiro Kuwajima,1 Munehito Arai,1,2 Tomonao Inobe,1 Kazuki Ito,3 Masaharu Nakao,1 Kosuke Maki,1 Kiyoto Kamagata,1 Hiroshi Kihara,4 and Yoshiyuki Amemiya5

1Department of Physics, School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
2Institute of Molecular Cell Biology, NIAIST, Tsukuba, Ibaraki 305-8566, Japan
3Institute of Materials Science, University of Tsukuba, Ibaraki 305-8572, Japan
4Department of Physics, Kansai Medical University, Hirakata, Osaka 573-1136, Japan
5Depatment of Advanced Materials Science, Graduate School of Frontier Science, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan

Copyright © 2002 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In order to improve the low signal-to-noise ratio of the time-resolved small-angle X-ray scattering, we have used a two-dimensional X-ray detector with a beryllium-windowed X-ray image intensifier and a charge-coupled device as an image sensor, and applied this to studies on (1) the kinetic folding reaction of α-lactalbumin, which accumulates the molten globule-like intermediate at an early stage of refolding and (2) the cooperative conformational transition of Escherichia coli chaperonin GroEL induced by ATP, which occurs in an allosteric manner between the close and open conformational states. In the α-lactalbumin reaction, we have firmly established the equivalence between the kinetic intermediate and the equilibrium molten globule state, and obtained further information about dehydration from the highly hydrated folding intermediate during a late stage of refolding. In the chaperonin study, we have successfully observed the kinetics of the allosteric transition of GroEL that occurs with a rate constant of about 3–4 s−1 at 5°C. The combination of the time-resolved X-ray scattering with other spectroscopic techniques such as circular dichroism and intrinsic fluorescence is thus very effective in understanding the conformational transitions of proteins and protein complexes.