Generation, movement and neutralization of charge species are universal in biological energy conversion and enzyme catalysis, recognition and signaling and gene action and regulation. At the mechanistic roots of all these reactions are directed electric fields that span length scales from the few Angstroms of catalytic sites to the tens of Angstroms across bioenergetic membranes. Measuring and understanding the generation, propagation and suppression of electric fields in biology represents a major area of ignorance and is a technical challenge. We meet the challenge of how nature engineers and harnesses electric fields through the unique advantages of de novo designed synthetic protein models, maquettes, that are robust, structured, and highly simplified versions of natural counterparts. Using a combination of organic chemistry and molecular biology, maquettes have been designed with experimental flexibility to specifically address how electric fields emanating from charges generated in the interior of protein during redox cofactor oxidation and reduction may propagate through protein. The goal is to understand how fields in proteins can be controlled in direction and in intensity to modulate in situ properties of redox centers and bound substrates and thereby govern their activity in respiratory electron transfer, proton exchange and translocation and enzyme catalysis. Two families of maquettes that incorporate a range of key mechanistic elements functionally representative of the biological oxidative processes will be used. One is a di-heme 4- alpha-helix protein and another is a 3-alpha-helix protein including radical forming side-chains tyrosine and tryptophan or substrates quinone and nicotinamide. Internal and external electric fields will be generated and measured electrochemically and by visible, infrared and NMR spectroscopy, exploiting strategically placed spectral (Stark) probes throughout the protein. Large scale fields will be monitored by electrochromic shifts in maquettes containing the polyene derivative of retinal and carotenes and chlorophyll molecules.
We aim to understand the fundamental means by which protein electric fields are productively managed and how mismanagement contributes to the failure of electron transfer protein that results in diseases arising from either genetic lesions at birth, stress or the natural result of the aging process. The design of new proteins employing our insights provides the most stringent experimental tests of our new understanding.
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