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 globular chromoprotein, namely mesoporphyrin-substituted horseradish peroxidase, with the respective behavior in a glass sample. From the distinct patterns between glass and protein as well as between various burn frequencies in the protein, we can clearly demonstrate that the chromophore in the protein is decoupled from the host glass and, hence, definitely probes the protein. Moreover, the electric fields in the protein pocket are quite different for the various tautomer states. These characteristic features are linked to allosteric-like behavior of proteins.