--- _id: '3721' abstract: - lang: eng text: 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. author: - first_name: Harald L full_name: Harald Janovjak id: 33BA6C30-F248-11E8-B48F-1D18A9856A87 last_name: Janovjak orcid: 0000-0002-8023-9315 - first_name: Daniel full_name: Mueller, Daniel J last_name: Mueller - first_name: Andrew full_name: Humphris, Andrew D last_name: Humphris citation: ama: 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 apa: Janovjak, H. L., Mueller, D., & Humphris, A. (2005). Molecular force modulation spectroscopy revealing the dynamic response of single bacteriorhodopsins. Biophysical Journal. Biophysical Society. https://doi.org/10.1529/biophysj.104.052746 chicago: Janovjak, Harald L, Daniel Mueller, and Andrew Humphris. “Molecular Force Modulation Spectroscopy Revealing the Dynamic Response of Single Bacteriorhodopsins.” Biophysical Journal. Biophysical Society, 2005. https://doi.org/10.1529/biophysj.104.052746. ieee: 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. Biophysical Society, pp. 1423–1431, 2005. ista: Janovjak HL, Mueller D, Humphris A. 2005. Molecular force modulation spectroscopy revealing the dynamic response of single bacteriorhodopsins. Biophysical Journal. 88(2), 1423–1431. mla: 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. short: H.L. Janovjak, D. Mueller, A. Humphris, Biophysical Journal 88 (2005) 1423–1431. date_created: 2018-12-11T12:04:48Z date_published: 2005-02-01T00:00:00Z date_updated: 2021-01-12T07:51:43Z day: '01' doi: 10.1529/biophysj.104.052746 extern: 1 intvolume: ' 88' issue: '2' main_file_link: - open_access: '1' url: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1305144/ month: '02' oa: 1 page: 1423 - 1431 publication: Biophysical Journal publication_status: published publisher: Biophysical Society publist_id: '2509' quality_controlled: 0 status: public title: Molecular force modulation spectroscopy revealing the dynamic response of single bacteriorhodopsins type: journal_article volume: 88 year: '2005' ...