Spectral Tuning of the Photoactive Yellow Protein Chromophore by H-Bonding

Gas phase photoabsorption measurements on model chromophores can be useful in shedding light on the issue of spectral tuning within photoactive proteins. In nature, protein pockets holding chromophores often form one or more H-bonds with the chromophore, which almost always participates in the photocycle of the protein. We address the issue of spectral tuning by H-bonds using one of the simplest model systems, the anionic form of trans p -coumaric acid.