Photoelectron spectra and structures of three cyclic dipeptides: PhePhe, TyrPro, and HisGly

摘要: We have investigated the electronic structure of three cyclic dipeptides: cyclo(Histidyl-Glycyl) (cHisGly), cyclo(Tyrosyl-Prolyl) (cTyrPro), and cyclo(Phenylalanyl-Phenylalanyl) (cPhePhe) in vapor phase, by means photoemission spectroscopy theoretical modeling. The last compound was evaporated from solid linear dipeptide, but cyclised, losing water to form cPhePhe gas phase. results are compared with our previous studies other cyclopeptides. Experimental valence core level spectra been interpreted light calculations identify basic chemical properties associated central diketopiperazine ring, additional functional groups. generally characterized a restricted set outer orbitals separated gap most orbitals. theoretically simulated all dipeptides agree reasonably well experimental spectra. ring side chains act as independent chromophores whose do not influence one another, except for prolyl dipeptides, where pyrrole is fused ring. In this case, significant changes were observed, explained stronger hybridization