Measurements of the stabilities of isolated retinal chromophores

Abstract

The barrier energies for isomerization and fragmentation were measured for a series of retinal chromophore derivatives using a tandem ion mobility spectrometry approach. These measurements allow us to quantify the effect of charge delocalization on the rigidity of chromophores. We find that the role of the methyl group on the C13 position is pivotal regarding the ground state dynamics of the chromophore. Additionally, a correlation between quasi-equilibrium isomer distribution and fragmentation pathways is observed.

Gas-phase studies of the retinal protonated Schiff base chromophore

“…In addition, a correlation was found between the fragmentation pathways and the quasi-equilibrium IMS distribution. The quasi-equilibrium IMS distribution of RPSB derivatives which fragment through cyclization contains a large tail towards low collisional cross sections, and are similar to each-other, while that of derivatives which do not fragment via cyclization lacks this tail [50]. This is in accordance with the fragmentation via cyclization process involving the formation of compact (cyclized) isomers.…”

“…1k) also fragments via cyclization, the 13-desmethyl derivative (shown in Fig. 1l) fragments through cleavage of the C12-C13 bond [50]. The dimethylated RPSB derivative (shown in Fig.…”

“…The dimethylated RPSB derivative (shown in Fig. 1i) does not have a single dominant fragmentation channel, instead, photo-fragmentation yields a large number of photo-fragments many of which can be explained by the cleavage of a single bond [43,50].…”