Q-band Electron Nuclear Double Resonance of Ferric Bleomycin and Activated Bleomycin Complexes with DNA: Fe(III) Hyperfine Interaction with 31P and DNA-Induced Perturbation to Bleomycin Str

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• 作者：Andrei Veselov ; Richard M. Burger ; and Charles P. Scholes
• 刊名：Journal of the American Chemical Society
• 出版年：1998
• 出版时间：February 11, 1998
• 年：1998
• 卷：120
• 期：5
• 页码：1030 - 1033
• 全文大小：86K
• 年卷期：v.120,no.5(February 11, 1998)
• ISSN：1520-5126

文摘

Q-band electron nuclear double resonance (ENDOR) has measuredanisotropic, distance-dependentdipolar hyperfine couplings from iron in ferric bleomycin[Fe(III)-BLM] and in activated bleomycin [Act-BLM] to ³¹P of substrate DNA. Studies were focused onbleomycin complexes with a self-complementaryduplex DNA 10-mer, d(GGAAGCTTCC)₂, containing a5'-G-C-3' sequence that is selective for bleomycincleavage (Mao, Q.; Fulmer, P.; Li, W.; DeRose, E. G.; Petering, D. H.J. Biol. Chem. 1996, 271,6185-6191).Bleomycin complexes with high molecular weight calf thymus DNAwere also used. Fe(III)-BLM and Act-BLM complexes with the 10-mer and the calf thymus DNA showed anisotropic³¹P dipolar hyperfine couplingsfrom which an Fe(III)-to-³¹P distance was estimated at7.4 ± 0.2 Å. High-resolution, angle-selected ENDORof the Fe(III)-BLM 10-mer complex showed that theFe(III)-to-³¹P vector lay at 25 ± 5ages/entities/deg.gif"> to themaximal gvalue direction, where the latter direction pointed near theexchangeable protons on axial BLM ligands and isassociated with the maximal hyperfine couplings of these protons(Veselov, A.; Sun, H.; Sienkiewicz, A.;Taylor, H.; Burger, R. M.; Scholes, C. P. J. Am. Chem. Soc.1995, 117, 7508-7512). Proton ENDORfeaturesof the Fe(III)-BLM but not Act-BLM were perturbed by DNAsubstrate. In the presence of the 10-mer andthe calf thymus DNA, proton ENDOR revealed distinct perturbation to thefrequencies of three sets ofnonexchangeable protons assigned to the BLM macrocycle and estimated tobe 2.9-3.5 Å from Fe(III) and tothe frequencies of exchangeable, axially located protons. Incontrast, the hyperfine couplings of covalentlybonded, first-shell nitrogen and [¹⁷O]peroxy ligandswere unchanged.