Conformational Dependence of Electron Transfer across de novo Designed Metalloproteins
Flash photolysis and pulse radiolysis measurements demonstrate a conformational dependence of electron transfer rates across a 16-mer helical bundle (three-helix metalloprotein) modified with a capping CoIII(bipyridine)3 electron acceptor at the N terminus and a 1-ethyl-1′-ethyl-4,4′-bip yridinium d...
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Published in | Proceedings of the National Academy of Sciences - PNAS Vol. 93; no. 18; pp. 9521 - 9526 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
United States
National Academy of Sciences of the United States of America
03.09.1996
National Acad Sciences National Academy of Sciences |
Subjects | |
Online Access | Get full text |
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Summary: | Flash photolysis and pulse radiolysis measurements demonstrate a conformational dependence of electron transfer rates across a 16-mer helical bundle (three-helix metalloprotein) modified with a capping CoIII(bipyridine)3 electron acceptor at the N terminus and a 1-ethyl-1′-ethyl-4,4′-bip yridinium donor at the C terminus. For the CoIII(peptide)3-1-ethyl-1<la tex>$^{\prime}$ -ethyl-4,4′-bipyridinium maquettes, the observed transfer is a first order, intramolecular process, independent of peptide concentration or laser pulse energy. In the presence of 6 M urea, the random coil bundle (≈ 0% helicity) has an observed electron transfer rate constant of kobs = 900 ± 100 s-1. In the presence of 25% trifluoroethanol (TFE), the helicity of the peptide is 80% and the kobs increases to 2000 ± 200 s-1. Moreover, the increase in the rate constant in TFE is consistent with the observed decrease in donor--acceptor distance in this solvent. Such bifunctional systems provide a class of molecules for testing the effects of conformation on electron transfer in proteins and peptides. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0027-8424 1091-6490 |
DOI: | 10.1073/pnas.93.18.9521 |