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Structural Examination of Enantioselective Intercalation: ^1H NMR of Rh(en)_2phi^(3+) Isomers Bound to d(GTGCAC)_2

Shields, Thomas P. and Barton, Jacqueline K. (1995) Structural Examination of Enantioselective Intercalation: ^1H NMR of Rh(en)_2phi^(3+) Isomers Bound to d(GTGCAC)_2. Biochemistry, 34 (46). pp. 15049-15056. ISSN 0006-2960. doi:10.1021/bi00046a010.

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The enantioselective recognition of d(GTGCAC)_2 by Δ- and Λ-Rh(en)_2phi^(3+) (en= ethylenediarnine; phi = 9, 10-phenanthrenequinone diimine) has been examined in a series of one-dimensional (ID) and two-dimensional (2D) 500 MHz ^1H NMR experiments both to extend our understanding of the basis for the enantioselective DNA binding and to gain structural information concerning intercalation by the octahedral metal complexes. Δ-Rh(en)_2phi^(3+) forms a symmetric 1:1 complex with d(GTGCAC)_2, and the metal complex is in slow exchange with the oligodeoxynucleotide bound form at 295 K. The strong upfield shifts of the phi ligand's aromatic protons (0.6-1.3 ppm) are consistent with full intercalation of the phi ligand into the DNA base stack. 2D-NOESY experiments reveal a loss in internucleotide connectivity between G_3 and C_4 bases, while new NOE cross peaks are observed between the phi ligand and the G_3 deoxyribose sugar. In contrast to binding by Δ-Rh(en)_2phi^(3+), the 1:1 Δ-Rh(en)_2phi^(3+)-d(GTGAC)_2 complex shows much broader resonances, and both metal complex and DNA protons appear to be in the intermediate exchange regime. The loss of C_2 symmetry in the 1:1 complex is consistent with binding by Λ-Rh(en)_2phi^(3+) at the T_2G_3 step. Although the enantiomeric metal complexes display different sequence selectivities and exchange characteristics, Λ- and Δ-Rh(en)_2phi^(3+) interact with the oligonucleotide duplex in a fundamentally similar manner, through the full intercalation of the phi ligand. Upfield movements in chemical shifts of phi protons are nearly identical for the two enantiomers, and both Λ- and Δ-Rh(en)_2phi^(3+) stabilize the duplex to melting by 5-10 °C. Given the common binding mode of the two enantiomers, the differences in their binding characteristics emanate from interactions with the ancillary nonintercalating ligands. Thus, as a general strategy, intercalation may provide an anchor for sequence-selective interactions of octahedral metal complexes in the groove of duplex DNA.

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Barton, Jacqueline K.0000-0001-9883-1600
Additional Information:© 1995 American Chemical Society. Received June 13, 1995; Revised Manuscript Received August 25, 1995. Publication Date: November 1995. Supported by grants to J.K.B. from the National Institutes of Health (GM33309) and an NIH-NRSA predoctoral fellowship to T.P.S.
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NIH Predoctoral FellowshipUNSPECIFIED
Issue or Number:46
Record Number:CaltechAUTHORS:20160405-140025577
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Official Citation:Structural Examination of Enantioselective Intercalation: 1H NMR of Rh(en)2phi3+ Isomers Bound to d(GTGCAC)2 Thomas P. Shields and Jacqueline K. Barton Biochemistry 1995 34 (46), 15049-15056 DOI: 10.1021/bi00046a010
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:65938
Deposited By: Ruth Sustaita
Deposited On:06 Apr 2016 18:18
Last Modified:10 Nov 2021 23:51

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