Effect of radiation damage on cytochrome c, irradiated with photons at the N 1s edge . The orbital of the peptide bond at 401.7 eV is quenched and two peaks are created at 399.1 and 400.2 eV by the product of the photochemical reaction. Such radiation-induced bond breaking in the backbone of cytochrome c suggests replacing complex protein structures by simpler molecules containing only the active heme region when designing biomimetic solar cells. The inset shows the structure of cytochrome c with the heme group inside (containing an Fe atom in a N cage).
The radiation-induced changes for the three nitrogen orbitals observed in Fig. 1 (, , and ). The peptide bond orbital (c) decays exponentially with increasing radiation dose, while the two radiation-induced orbitals (a and b) grow at the same rate as c vanishes. The constant a/b intensity ratio is consistent with two nitrogen orbitals at the site of the broken peptide bond.
Effect of irradiation on the Fe 2p edge of the central Fe atom in the heme group of cytochrome c. The bottom spectrum is for pristine cytochrome c, and the radiation dose increases toward the top spectrum. The change in the multiplet structure points to a change in the 3d spin configuration or in the crystal field at the Fe atom. It is too small to be caused by a change of the oxidation state.
Radiation-induced shift of the HOMO relative to the Fermi level for -phthalocyanine. The top panel gives an overview spectrum of the occupied orbitals. The bottom panel zooms in on the HOMO and shows its upwards shift with irradiation. Spectra are shown for 0, 20, and 40 s exposure (full lines) and for a much higher exposure (dot-dashed) where an inhomogeneous energy shift causes substantial broadening.
Article metrics loading...
Full text loading...