Two distinct overstretched DNA structures revealed by single-molecule thermodynamics measurements
Double-stranded DNA is a dynamic molecule whose structure can change depending on conditions. While there is consensus in the literature about many structures DNA can have, the state of highly-stretched DNA is still not clear. Several groups have shown that DNA in the torsion-unconstrained B-form un...
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| Format: | Article |
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National Academy of Sciences
2012
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| Online Access: | http://hdl.handle.net/1721.1/75398 |
| _version_ | 1811081279325601792 |
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| author | Zhang, Xinghua Chen, Hu Fu, Hongxia Doyle, Patrick S. Yan, Jie |
| author2 | Massachusetts Institute of Technology. Department of Chemical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Chemical Engineering Zhang, Xinghua Chen, Hu Fu, Hongxia Doyle, Patrick S. Yan, Jie |
| author_sort | Zhang, Xinghua |
| collection | MIT |
| description | Double-stranded DNA is a dynamic molecule whose structure can change depending on conditions. While there is consensus in the literature about many structures DNA can have, the state of highly-stretched DNA is still not clear. Several groups have shown that DNA in the torsion-unconstrained B-form undergoes an “overstretching” transition at a stretching force of around 65 pN, which leads to approximately 1.7-fold elongation of the DNA contour length. Recent experiments have revealed that two distinct structural transitions are involved in the overstretching process: (i) a hysteretic “peeling” off one strand from its complementary strand, and (ii) a nonhysteretic transition that leads to an undetermined DNA structure. We report the first simultaneous determination of the entropy (ΔS) and enthalpy changes (ΔH) pertaining to these respective transitions. For the hysteretic peeling transition, we determined ΔS ∼ 20 cal/(K.mol) and ΔH ∼ 7 kcal/mol. In the case of the nonhysteretic transition, ΔS ∼ -3 cal/(K.mol) and ΔH ∼ 1 kcal/mol. Furthermore, the response of the transition force to salt concentration implies that the two DNA strands are spatially separated after the hysteretic peeling transition. In contrast, the corresponding response after the nonhysteretic transition indicated that the strands remained in close proximity. The selection between the two transitions depends on DNA base-pair stability, and it can be illustrated by a multidimensional phase diagram. Our results provide important insights into the thermodynamics of DNA overstretching and conformational structures of overstretched DNA that may play an important role in vivo. |
| first_indexed | 2024-09-23T11:44:14Z |
| format | Article |
| id | mit-1721.1/75398 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T11:44:14Z |
| publishDate | 2012 |
| publisher | National Academy of Sciences |
| record_format | dspace |
| spelling | mit-1721.1/753982022-10-01T05:37:57Z Two distinct overstretched DNA structures revealed by single-molecule thermodynamics measurements Zhang, Xinghua Chen, Hu Fu, Hongxia Doyle, Patrick S. Yan, Jie Massachusetts Institute of Technology. Department of Chemical Engineering Doyle, Patrick S. Double-stranded DNA is a dynamic molecule whose structure can change depending on conditions. While there is consensus in the literature about many structures DNA can have, the state of highly-stretched DNA is still not clear. Several groups have shown that DNA in the torsion-unconstrained B-form undergoes an “overstretching” transition at a stretching force of around 65 pN, which leads to approximately 1.7-fold elongation of the DNA contour length. Recent experiments have revealed that two distinct structural transitions are involved in the overstretching process: (i) a hysteretic “peeling” off one strand from its complementary strand, and (ii) a nonhysteretic transition that leads to an undetermined DNA structure. We report the first simultaneous determination of the entropy (ΔS) and enthalpy changes (ΔH) pertaining to these respective transitions. For the hysteretic peeling transition, we determined ΔS ∼ 20 cal/(K.mol) and ΔH ∼ 7 kcal/mol. In the case of the nonhysteretic transition, ΔS ∼ -3 cal/(K.mol) and ΔH ∼ 1 kcal/mol. Furthermore, the response of the transition force to salt concentration implies that the two DNA strands are spatially separated after the hysteretic peeling transition. In contrast, the corresponding response after the nonhysteretic transition indicated that the strands remained in close proximity. The selection between the two transitions depends on DNA base-pair stability, and it can be illustrated by a multidimensional phase diagram. Our results provide important insights into the thermodynamics of DNA overstretching and conformational structures of overstretched DNA that may play an important role in vivo. 2012-12-12T13:49:26Z 2012-12-12T13:49:26Z 2012-05 2011-06 Article http://purl.org/eprint/type/JournalArticle 0027-8424 1091-6490 http://hdl.handle.net/1721.1/75398 Zhang, X. et al. “Two Distinct Overstretched DNA Structures Revealed by Single-molecule Thermodynamics Measurements.” Proceedings of the National Academy of Sciences 109.21 (2012): 8103–8108. en_US http://dx.doi.org/10.1073/pnas.1109824109 Proceedings of the National Academy of Sciences Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf National Academy of Sciences PNAS |
| spellingShingle | Zhang, Xinghua Chen, Hu Fu, Hongxia Doyle, Patrick S. Yan, Jie Two distinct overstretched DNA structures revealed by single-molecule thermodynamics measurements |
| title | Two distinct overstretched DNA structures revealed by single-molecule thermodynamics measurements |
| title_full | Two distinct overstretched DNA structures revealed by single-molecule thermodynamics measurements |
| title_fullStr | Two distinct overstretched DNA structures revealed by single-molecule thermodynamics measurements |
| title_full_unstemmed | Two distinct overstretched DNA structures revealed by single-molecule thermodynamics measurements |
| title_short | Two distinct overstretched DNA structures revealed by single-molecule thermodynamics measurements |
| title_sort | two distinct overstretched dna structures revealed by single molecule thermodynamics measurements |
| url | http://hdl.handle.net/1721.1/75398 |
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