Intraprotein electron transfer

Eleven 9,10-anthraquinones with various substituents, seven 1,4-naphthoquinones, 1,2-naphthaquinone and five 1,4-benzoquinones were used as QA. These quinones provide a series of RCs with a variation of the reaction exothermicity, - AG , from 0.11 to 0.9 eV. The rates of intraprotein electron transfer from various Qa to (BChl)J were found to be virtually temperature independent from 5 to 100 K and to decrease severalfold from 100 to 300 K. Only a small change of the rate upon the — AG° variation was found when reaction was made more exothermic than in the native RC. As the reaction was made less exothermic, the rate decreased notably without becoming temperature dependent. 

Many other papers on long-range electron transfer between two reactive sites of modified proteins were published [270-288] after the above mentioned pioneering works. Most of them dealt with photoinduced electron tunneling from triplet states of closed shell Mg(II) and Zn(II) porphyrins to Fe(III) or Ru(III). In agreement with the prediction of Marcus theory the rate constants for the majority of these intraprotein electron transfer reactions were found to increase as the free energy of reaction decreased. However for one of the reactions disagreement with this theory was observed [285],... 

With site-directed mutation and femtosecond-resolved fluorescence methods, we have used tryptophan as an excellent local molecular reporter for studies of a series of ultrafast protein dynamics, which include intraprotein electron transfer [64-68] and energy transfer [61, 69], as well as protein hydration dynamics [70-74]. As an optical probe, all these ultrafast measurements require no potential quenching of excited-state tryptophan by neighboring protein residues or peptide bonds on the picosecond time scale. However, it is known that tryptophan fluorescence is readily quenched by various amino acid residues [75] and peptide bonds [76-78]. Intraprotein electron transfer from excited indole moiety to nearby electrophilic residue(s) was proposed to be the quenching... 

Kavakli HI, Sancar A. Analysis of the role of intraprotein electron transfer in photoreactivation by DNA photolyase in vivo. Biochemistry 2004 43 15104-10. 

Figure 2.8. The Gibbs energy optimized ET rate vs. edge-to-edge distance relationship for intraprotein electron transfer. The bacteria RC rate constants are shown as circles and excited heme-ruthenium ET in modified myoglobin and cytochrome c are shown as triangles (Moser and Dutton, 1992). Reproduced with permission.

The foeus of this chapter is the soluble electron transfer complex formed between the nieotinamide-independent trimethylamine dehydrogenase (TMADH) and eleetron transferring flavoprotein (ETF). Recent studies of this physiological electron transfer complex have provided invaluable insight into (i) the mechanisms of inter and intraprotein electron transfer between flavin and Fe/S centers, (ii) the role of dynamics in interprotein electron transfer and (hi) quantum meehanieal mechanisms for the cleavage of substrate C-H bonds and the subsequent transfer of reducing equivalents to flavin redox centers. Brief mention is made of early structural and cofactor analyses for this redox system, but more detailed accounts of this work can be found in earlier reviews on the subjeet (e.g. Steenkamp and Mathews, 1992). 

Sharp, R. E., Chapman, S. K., and Reid, G. A., 1996a, Modulation of flavocytochrome fcj intraprotein electron transfer via an interdomain hinge, Biochem. J. 316 507n513. 

Smface modification with ruthenium complexes has proven valuable in studies of both interprotein and intraprotein electron transfer in systems that are difflcult to stndy by traditional kinetic tools. The choice of ruthenium complexes in these investigations stems from an extensive photochemistry as well as exceptional thermal stability. The photochemistry provides a means of examining reactions over a time range of nanoseconds to seconds by laser-flash photolysis and the thermal stability allows researchers to covalently bind a wide variety of complexes to proteins with... 

Voltammetry provides a useful tool for studying redox chemistry of the molecules relevant to biological redox reactions. Many proteins are exclusively involved in intraprotein electron transfer and typically function in ordered structures such as mitochondria. Under these circumstances, the redox... 

Aubert, C., Mathis, R, Eker, A.P.M., and Brettel, K., Intraprotein electron transfer between tyrosine and tryptophan in DNA photolyase from Anacystis nidulans, Proc. Natl. Acad. Sci. USAy 96, 5423, 1999. 

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