Jahn-Teller effect in biomolecules

Sub-lattice of Jahn-Teller centers in hexaferrite crystal

A novel type of sub-lattice of the Jahn-Teller (JT) centers was arranged in Ti-doped barium hexaferrite BaFe₁₂O₁₉. In the un-doped crystal all iron ions, sitting in five different crystallographic positions, are Fe³⁺ in the high-spin configuration (S = 5/2) and have a non-degenerate ground state. We show that the electron-donor Ti substitution converts the ions to Fe²⁺ predominantly in tetrahedral coordination, resulting in doubly-degenerate states subject to the [Formula: see text] problem of the JT effect. The arranged JT complexes, Fe²⁺O₄, their adiabatic potential energy, non-linear and quantum dynamics, have been studied by means of ultrasound and terahertz-infrared spectroscopies. The JT complexes are sensitive to external stress and applied magnetic field. For that reason, the properties of the doped crystal can be controlled by the amount and state of the JT complexes.

Distribution of the iron-heme displacement as resulting from myoglobin conformational substrates: an AOM approach to the interpretation of the EPR spectra

The electron paramagnetic resonance (EPR) low-temperature spectra of high spin ferric myoglobin samples in different solvent composition have been analyzed in terms of a distribution of the energy differences delta 1 and delta 2 for the iron low-lying electronic states. The widths of these distributions, which are found to be dependent on the solvent composition, have been correlated to the presence of a frozen ensemble of conformational substrates. A dedicated analysis based on the angular overlap method (AOM) has allowed us to work out a quantitative relationship between the delta 1 and delta 2 distributions and the spread of the iron-heme displacement; this being a structural parameter relevant for the biological functionality of the protein. The observed dependence of the iron-heme displacement distribution on the solvent composition is discussed.