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Exchangeable proton ENDOR as a probe of the redox-active iron center in activated bleomycin and ferric bleomycin.

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Title: Exchangeable proton ENDOR as a probe of the redox-active iron center in activated bleomycin and ferric bleomycin.
Authors: Burger, Richard M.1, Grigoryants, Vladimir M.2, Scholes, Charles P.2
Source: Dalton Transactions: An International Journal of Inorganic Chemistry. 10/21/2017, Vol. 46 Issue 39, p13263-13272. 10p.
Subjects: Proton scattering, Electron nuclear double resonance, Molecular probes, Iron spectra, Bleomycin, Iron compounds
Abstract: Activated bleomycin (ABLM) is a drug-Fe(iii)-hydroperoxide complex kinetically competent in DNA attack (via H4′ abstraction). This intermediate is relatively stable, but its spontaneous conversion to ferric bleomycin (Fe(iii)·BLM) is poorly characterized because no observable intermediate product accumulates. The Fe(iii)·BLM formed cryophotolytically from ABLM and kept at 77 K was remarkably similar by EPR and ENDOR criteria to Fe(iii)·BLM formed from Fe(iii) + BLM solution. The notable ENDOR criteria were the ENDOR frequencies and features of orientation-selected, strongly hyperfine-coupled, exchangeable protons associated with the environs of the iron within ＜3.5 Å of paramagnetic Fe(iii) in Fe(iii)·BLM and ABLM. Cryophotolytic conversion of activated bleomycin to its ferric bleomycin product in the frozen solid is a sign that the reaction requires only constrained local proton rearrangements. We have characterized the metal–proton distances and orientations of the protons in that rearrangement, especially noting that these protons are of mechanistic importance in the ambient temperature conversion of ABLM to Fe(iii)·BLM in concert with a directed radical-forming attack on DNA. [ABSTRACT FROM AUTHOR]
Copyright of Dalton Transactions: An International Journal of Inorganic Chemistry is the property of Royal Society of Chemistry and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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DbLabel: Engineering Source
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  Data: Exchangeable proton ENDOR as a probe of the redox-active iron center in activated bleomycin and ferric bleomycin.
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  Data: <searchLink fieldCode="AR" term="%22Burger%2C+Richard+M%2E%22">Burger, Richard M.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Grigoryants%2C+Vladimir+M%2E%22">Grigoryants, Vladimir M.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Scholes%2C+Charles+P%2E%22">Scholes, Charles P.</searchLink><relatesTo>2</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22Dalton+Transactions%3A+An+International+Journal+of+Inorganic+Chemistry%22">Dalton Transactions: An International Journal of Inorganic Chemistry</searchLink>. 10/21/2017, Vol. 46 Issue 39, p13263-13272. 10p.
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  Data: <searchLink fieldCode="DE" term="%22Proton+scattering%22">Proton scattering</searchLink><br /><searchLink fieldCode="DE" term="%22Electron+nuclear+double+resonance%22">Electron nuclear double resonance</searchLink><br /><searchLink fieldCode="DE" term="%22Molecular+probes%22">Molecular probes</searchLink><br /><searchLink fieldCode="DE" term="%22Iron+spectra%22">Iron spectra</searchLink><br /><searchLink fieldCode="DE" term="%22Bleomycin%22">Bleomycin</searchLink><br /><searchLink fieldCode="DE" term="%22Iron+compounds%22">Iron compounds</searchLink>
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  Data: Activated bleomycin (ABLM) is a drug-Fe(iii)-hydroperoxide complex kinetically competent in DNA attack (via H4′ abstraction). This intermediate is relatively stable, but its spontaneous conversion to ferric bleomycin (Fe(iii)·BLM) is poorly characterized because no observable intermediate product accumulates. The Fe(iii)·BLM formed cryophotolytically from ABLM and kept at 77 K was remarkably similar by EPR and ENDOR criteria to Fe(iii)·BLM formed from Fe(iii) + BLM solution. The notable ENDOR criteria were the ENDOR frequencies and features of orientation-selected, strongly hyperfine-coupled, exchangeable protons associated with the environs of the iron within ＜3.5 Å of paramagnetic Fe(iii) in Fe(iii)·BLM and ABLM. Cryophotolytic conversion of activated bleomycin to its ferric bleomycin product in the frozen solid is a sign that the reaction requires only constrained local proton rearrangements. We have characterized the metal–proton distances and orientations of the protons in that rearrangement, especially noting that these protons are of mechanistic importance in the ambient temperature conversion of ABLM to Fe(iii)·BLM in concert with a directed radical-forming attack on DNA. [ABSTRACT FROM AUTHOR]
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  Data: <i>Copyright of Dalton Transactions: An International Journal of Inorganic Chemistry is the property of Royal Society of Chemistry and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1039/c7dt01354j
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      – Code: eng
        Text: English
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        PageCount: 10
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      – SubjectFull: Proton scattering
        Type: general
      – SubjectFull: Electron nuclear double resonance
        Type: general
      – SubjectFull: Molecular probes
        Type: general
      – SubjectFull: Iron spectra
        Type: general
      – SubjectFull: Bleomycin
        Type: general
      – SubjectFull: Iron compounds
        Type: general
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      – TitleFull: Exchangeable proton ENDOR as a probe of the redox-active iron center in activated bleomycin and ferric bleomycin.
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            NameFull: Grigoryants, Vladimir M.
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            – D: 21
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              Text: 10/21/2017
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              Y: 2017
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