Molecular force modulation spectroscopy revealing the dynamic response of single bacteriorhodopsins

H.L. Janovjak, D. Mueller, A. Humphris, Biophysical Journal 88 (2005) 1423–1431.


Journal Article | Published
Author
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Abstract
Recent advances in atomic force microscopy allowed globular and membrane proteins to be mechanically unfolded on a single-molecule level. Presented is an extension to the existing force spectroscopy experiments. While unfolding single bacteriorhodopsins from native purple membranes, small oscillation amplitudes (6–9nm) were supplied to the vertical displacement of the cantilever at a frequency of 3kHz. The phase and amplitude response of the cantilever-protein system was converted to reveal the elastic (conservative) and viscous (dissipative) contributions to the unfolding process. The elastic response (stiffness) of the extended parts of the protein were in the range of a few tens pN/nm and could be well described by the derivative of the wormlike chain model. Discrete events in the viscous response coincided with the unfolding of single secondary structure elements and were in the range of 1μNs/m. In addition, these force modulation spectroscopy experiments revealed novel mechanical unfolding intermediates of bacteriorhodopsin. We found that kinks result in a loss of unfolding cooperativity in transmembrane helices. Reconstructing force-distance spectra by the integration of amplitude-distance spectra verified their position, offering a novel approach to detect intermediates during the forced unfolding of single proteins.
Publishing Year
Date Published
2005-02-01
Journal Title
Biophysical Journal
Volume
88
Issue
2
Page
1423 - 1431
IST-REx-ID

Cite this

Janovjak HL, Mueller D, Humphris A. Molecular force modulation spectroscopy revealing the dynamic response of single bacteriorhodopsins. Biophysical Journal. 2005;88(2):1423-1431. doi:10.1529/biophysj.104.052746
Janovjak, H. L., Mueller, D., & Humphris, A. (2005). Molecular force modulation spectroscopy revealing the dynamic response of single bacteriorhodopsins. Biophysical Journal, 88(2), 1423–1431. https://doi.org/10.1529/biophysj.104.052746
Janovjak, Harald L, Daniel Mueller, and Andrew Humphris. “Molecular Force Modulation Spectroscopy Revealing the Dynamic Response of Single Bacteriorhodopsins.” Biophysical Journal 88, no. 2 (2005): 1423–31. https://doi.org/10.1529/biophysj.104.052746.
H. L. Janovjak, D. Mueller, and A. Humphris, “Molecular force modulation spectroscopy revealing the dynamic response of single bacteriorhodopsins,” Biophysical Journal, vol. 88, no. 2, pp. 1423–1431, 2005.
Janovjak HL, Mueller D, Humphris A. 2005. Molecular force modulation spectroscopy revealing the dynamic response of single bacteriorhodopsins. Biophysical Journal. 88(2), 1423–1431.
Janovjak, Harald L., et al. “Molecular Force Modulation Spectroscopy Revealing the Dynamic Response of Single Bacteriorhodopsins.” Biophysical Journal, vol. 88, no. 2, Biophysical Society, 2005, pp. 1423–31, doi:10.1529/biophysj.104.052746.

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