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Updated: Jun 23, 2026
10:03
Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
Unfolding study of native bacteriorhodopsin under acidic condition
Takashi Kodama1, Tatsuya Koyanagi, Hiroshi Sekiguchi
1Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
Ultramicroscopy
|May 19, 2009
Summary
Atomic force microscopy revealed structural changes in purple membrane (PM) under acidic conditions. Acidification shifts unfolding spectra, suggesting a new secondary structure forms in acidified PM.
Area of Science:
- Biophysics
- Structural Biology
- Membrane Proteins
Background:
- Purple membrane (PM) is a specialized membrane rich in bacteriorhodopsin.
- Acid titration or cation removal induces a structural transition in PM, forming "blue membrane".
Purpose of the Study:
- To investigate the structural properties of "blue membrane" using atomic force microscopy.
- To understand structural changes in PM under acidic conditions.
Main Methods:
- Force curve measurements using atomic force microscopy (AFM).
- Immobilization of PM fragments on a glass substrate.
- AFM analysis under neutral (pH 7.2) and acidic (pH 2.4) conditions.
Main Results:
- Unfolding spectra peak positions shifted to shorter extensions under acidic conditions compared to neutral pH.
- A significant shift of approximately 5nm was observed in the relative position of the first unfolding peak.
- These findings indicate structural alterations in the acidified PM.
Conclusions:
- Acidification of PM induces structural changes.
- A specific secondary structure may form from the C-terminus to helices F in acidified PM.
- AFM force curve measurements provide insights into membrane protein structural transitions.
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