Abstract
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'- bipyridinium donor at the C terminus. For the CoIII(peptide)3-1-ethyl-1'-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 (approximately 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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- Chen Y. H., Yang J. T., Chau K. H. Determination of the helix and beta form of proteins in aqueous solution by circular dichroism. Biochemistry. 1974 Jul 30;13(16):3350–3359. doi: 10.1021/bi00713a027. [DOI] [PubMed] [Google Scholar]
- Fields G. B., Noble R. L. Solid phase peptide synthesis utilizing 9-fluorenylmethoxycarbonyl amino acids. Int J Pept Protein Res. 1990 Mar;35(3):161–214. doi: 10.1111/j.1399-3011.1990.tb00939.x. [DOI] [PubMed] [Google Scholar]
- Geren L., Hahm S., Durham B., Millett F. Photoinduced electron transfer between cytochrome c peroxidase and yeast cytochrome c labeled at Cys 102 with (4-bromomethyl-4'-methylbipyridine)[bis(bipyridine)]ruthenium2+. Biochemistry. 1991 Oct 1;30(39):9450–9457. doi: 10.1021/bi00103a009. [DOI] [PubMed] [Google Scholar]
- Haas E., Katchalski-Katzir E., Steinberg I. Z. Effect of the orientation of donor and acceptor on the probability of energy transfer involving electronic transitions of mixed polarization. Biochemistry. 1978 Nov 14;17(23):5064–5070. doi: 10.1021/bi00616a032. [DOI] [PubMed] [Google Scholar]
- Handel T. M., Williams S. A., DeGrado W. F. Metal ion-dependent modulation of the dynamics of a designed protein. Science. 1993 Aug 13;261(5123):879–885. doi: 10.1126/science.8346440. [DOI] [PubMed] [Google Scholar]
- Langen R., Chang I. J., Germanas J. P., Richards J. H., Winkler J. R., Gray H. B. Electron tunneling in proteins: coupling through a beta strand. Science. 1995 Jun 23;268(5218):1733–1735. doi: 10.1126/science.7792598. [DOI] [PubMed] [Google Scholar]