Efficient excited-state deactivation of the gly-phe-ala tripeptide via an electron-driven proton-transfer process

Ab initio electronic-structure calculations indicate a mechanism for efficient excited-state deactivation of a low-energy conformer of the Gly-Phe-Ala tripeptide. The particularly short excited-state lifetime can explain the unexpected absence of this conformer in resonant two-photon ionization spectra. It is suggested that these ultrafast electronic deactivation processes provide specific conformers of peptides with a high degree of photostability.