期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：32
页码：13196-13201
DOI：10.1073/pnas.0904729106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：It has been suggested that the structure that results when double-stranded DNA (dsDNA) is pulled from the 3'3' ends differs from that which results when it is pulled from the 5'5' ends. In this work, we demonstrate, using {lambda} phage dsDNA, that the overstretched states do indeed show different properties, suggesting that they correspond to different structures. For 3'3' pulling versus 5'5' pulling, the following differences are observed: (i) the forces at which half of the molecules in the ensemble have made a complete force-induced transition to single stranded DNA are 141 {+/-} 3 pN and 122 {+/-} 4 pN, respectively; (ii) the extension vs. force curve for overstretched DNA has a marked change in slope at 127 {+/-} 3 pN for 3'3' and 110 {+/-} 3 pN for 5'5'; (iii) the hysteresis (H) in the extension vs. force curves at 150 mM NaCl is 0.3 {+/-} 0.8 pN {micro}m for 3'3' versus 13 {+/-} 8 pN for 5'5'; and (iv) 3'3' and 5'5' molecules show different changes in hysteresis due to interactions with {beta}-cyclodextrin, a molecule that is known to form stable host-guest complexes with rotated base pairs, and glyoxal that is known to bind stably to unpaired bases. These differences and additional findings are well-accommodated by the corresponding structures predicted on theoretical grounds.
