STRUCTURAL-CHANGES AND INTERNAL FIELDS IN PROTEINS - A HOLE-BURNING STARK-EFFECT STUDY OF HORSERADISH-PEROXIDASE

We compare the Stack spectra of photochemical holes burnt into a globu lar chromoprotein, namely mesoporphyrin-substituted horseradish peroxi dase, with the respective behavior in a glass sample. From the distinc t patterns between glass and protein as well as between various burn f requencies in the protein, we can clearly demonstrate that the chromop hore in the protein is decoupled from the host glass and, hence, defin itely probes the protein. Moreover, the electric fields in the protein pocket are quite different for the various tautomer states. These cha racteristic features are linked to allosteric-like behavior of protein s.