Ab initio study of the electronic singlet excited-state properties of tryptophan in the gas phase: The role of alanyl side-chain conformations

Indole is the chromophore of tryptophan. Do the various conformations of the alanyl side-chain influence the properties of the low-lying excited states? We answer this question by means of accurate ab initio calculations on several tryptophan conformer in the gas phase, and show, for instance, that the polarity of the electronic states strongly depends on the alanyl conformation.