dorsal/arxiv
View SchemaMechanical unfolding of RNA hairpins
| Authors | Changbong Hyeon, D. Thirumalai |
|---|---|
| Categories | |
| ArXiv ID | q-bio/0503029 |
| URL | https://arxiv.org/abs/q-bio/0503029 |
| DOI | 10.1073/pnas.0408314102 |
| Journal | Proc. Natl. Acad. Sci. 102, 6789-6794 (2005) |
Abstract
Mechanical unfolding trajectories, generated by applying constant force in optical tweezer experiments, show that RNA hairpins and the P5abc subdomain of the group I intron unfold reversibly. We use coarse-grained Go-like models for RNA hairpins to explore forced-unfolding over a broad range of temperatures. A number of predictions that are amenable to experimental tests are made. At the critical force the hairpin jumps between folded and unfolded conformations without populating any discernible intermediates. The phase diagram in the force-temperature (f,T) plane shows that the hairpin unfolds by an all-or-none process. The cooperativity of the unfolding transition increases dramatically at low temperatures. Free energy of stability, obtained from time averages of mechanical unfolding trajectories, coincide with ensemble averages which establishes ergodicity. The hopping time between the the native basin of attraction (NBA) and the unfolded basin increases dramatically along the phase boundary. Thermal unfolding is stochastic whereas mechanical unfolding occurs in "quantized steps" with great variations in the step lengths. Refolding times, upon force quench, from stretched states to the NBA is "at least an order of magnitude" greater than folding times by temperature quench. Upon force quench from stretched states the NBA is reached in at least three stages. In the initial stages the mean end-to-end distance decreases nearly continuously and only in the last stage there is a sudden transition to the NBA. Because of the generality of the results we propose that similar behavior should be observed in force quench refolding of proteins.
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"abstract": "Mechanical unfolding trajectories, generated by applying constant force in\noptical tweezer experiments, show that RNA hairpins and the P5abc subdomain of\nthe group I intron unfold reversibly. We use coarse-grained Go-like models for\nRNA hairpins to explore forced-unfolding over a broad range of temperatures. A\nnumber of predictions that are amenable to experimental tests are made. At the\ncritical force the hairpin jumps between folded and unfolded conformations\nwithout populating any discernible intermediates. The phase diagram in the\nforce-temperature (f,T) plane shows that the hairpin unfolds by an all-or-none\nprocess. The cooperativity of the unfolding transition increases dramatically\nat low temperatures. Free energy of stability, obtained from time averages of\nmechanical unfolding trajectories, coincide with ensemble averages which\nestablishes ergodicity. The hopping time between the the native basin of\nattraction (NBA) and the unfolded basin increases dramatically along the phase\nboundary. Thermal unfolding is stochastic whereas mechanical unfolding occurs\nin \"quantized steps\" with great variations in the step lengths. Refolding\ntimes, upon force quench, from stretched states to the NBA is \"at least an\norder of magnitude\" greater than folding times by temperature quench. Upon\nforce quench from stretched states the NBA is reached in at least three stages.\nIn the initial stages the mean end-to-end distance decreases nearly\ncontinuously and only in the last stage there is a sudden transition to the\nNBA. Because of the generality of the results we propose that similar behavior\nshould be observed in force quench refolding of proteins.",
"arxiv_id": "q-bio/0503029",
"authors": [
"Changbong Hyeon",
"D. Thirumalai"
],
"categories": [
"q-bio.BM",
"q-bio.QM"
],
"doi": "10.1073/pnas.0408314102",
"journal_ref": "Proc. Natl. Acad. Sci. 102, 6789-6794 (2005)",
"title": "Mechanical unfolding of RNA hairpins",
"url": "https://arxiv.org/abs/q-bio/0503029"
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