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| {{STRUCTURE_1ybl| PDB=1ybl | SCENE= }} | | {{STRUCTURE_1ybl| PDB=1ybl | SCENE= }} |
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| '''NMR structure of the i-motif tetramer of d(AACCCC)'''
| | ===NMR structure of the i-motif tetramer of d(AACCCC)=== |
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| ==Overview==
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| Using NMR methods, we have resolved the i-motif structures formed by d(AACCCC) and by d(CCCCAA), two versions of the DNA sequence repeated in the telomeric regions of the C-rich strand of tetrahymena chromosomes. Both oligonucleotides form fully symmetrical i-motif tetramers built by intercalation of two hemiprotonated duplexes containing four C*C+ pairs. The structures are extremely stable. In the tetramer of d(AACCCC), the outermost C*C+ pairs are formed by the cytidines of the 5' ends of the cytidine tracts. A2 forms an A2*A2 (H6trans-N7) pair stacked to C3*C3+ and cross-strand stacked to A1. At 0 degrees C, the lifetimes of the hemiprotonated pairs range from 1 ms for the outermost pair to approximately 1 h for the innermost pairs. The tetramer of d(CCCCAA) adopts two distinct intercalation topologies in slow conformational exchange. One, whose outermost C*C+ pairs are built by the cytidines of the 5' end and the other by those of the 3' end. In both topologies, the adenosine bases are fairly well stacked to the adjacent C*C+ pairs. They are not paired but form symmetrical pseudo-pairs with their H6cis amino proton and N1 nitrogen pointing towards each other.
| | The line below this paragraph, {{ABSTRACT_PUBMED_15647504}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 15647504 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_15647504}} |
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| ==About this Structure== | | ==About this Structure== |
| Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1YBL OCA]. | | Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1YBL OCA]. |
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| ==Reference== | | ==Reference== |
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| [[Category: Telomer]] | | [[Category: Telomer]] |
| [[Category: Tetrahymena]] | | [[Category: Tetrahymena]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 16:07:05 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 19:28:24 2008'' |
