Ion Mobility Unlocks the Photofragmentation Mechanism of Retinal Protonated Schiff Base.
Retinal protonated Schiff base (RPSB) is a key molecular component of biological photoreceptors and bacterial photosynthetic structures, where its action involves photoisomerization around bonds in the polyene chain. In a vacuum environment, collisional activation or exposure to visible light causes the RPSB molecule to disintegrate, producing charged molecular fragments with m/z = 248 Da that cannot be formed by simple cleavage of the polyene chain. Photofragments resulting from laser excitation of RPSB at a wavelength of 532 nm are analyzed in an ion mobility mass spectrometer (IMMS) and found to be the protonated Schiff base of β-ionone. Density functional theory calculations at the M06-2X/cc-pVDZ level support a fragmentation mechanism in which RPSB undergoes an electrocyclization/fragmentation cascade with the production of protonated Schiff base of β-ionone and toluene.
School of Chemistry, The University of Melbourne, Melbourne, Victoria, Australia 3010.
N J A
NJ
Coughlan
School of Chemistry, The University of Melbourne, Melbourne, Victoria, Australia 3010.
B D
BD
Adamson
School of Chemistry, The University of Melbourne, Melbourne, Victoria, Australia 3010.
K J
KJ
Catani
School of Chemistry, The University of Melbourne, Melbourne, Victoria, Australia 3010.
U
U
Wille
School of Chemistry, The University of Melbourne, Melbourne, Victoria, Australia 3010.
E J
EJ
Bieske
electrocyclization; ion mobility; mass spectrometry; photodissociation; retinal