We have succeeded in designing and constructing de novo synthetic flavo-hemo-proteins that exhibit light activated intraprotein electron transfer. We use our traditional four-helix bundle framework to covalently link a bromoflavin to an interior cysteine very close to the geometric center of the bundle. In the same bundle, interior histidines a positioned to form a bis-His ligation of added heme toward either end of the bundle interior. We have shown that illumination of the blue flavin absorption band creates an excited state which can extract a pair of electrons from a convenient nitrogenous base donor (such as EDTA) to create a reduced flavin that spontaneously transfers electrons to nearby bis-histidine ligated heme. It is our intent to use the RLBL nanosecond dye laser to capture the spectra of the excited flavin state, the subsequent reduced flavin, and to provide an initial description of the time course of intraprotein electron transfer from the reduced flavin to the heme. It is quite possible that there will be a heterogeneity of the time course corresponding to a distribution of flavin/heme distances for different conformations of the redox peptide. We are investigating a competition between flavin excited state quenching by energy transfer to the heme and electron transfer between the flavin and the heme. We are flowing the synthetic flavo-hemo-protein plus EDTA solution through a cell to compare the spectra of regions with and without the blue pump pulse. We easily regenerate our material by exposing the solution to molecular oxygen, which rapidly oxidizes the heme component.
Showing the most recent 10 out of 128 publications
