Light activation of the isomerization and deprotonation of the protonated Schiff base retinal

Abstract

We perform an ab initio analysis of the photoisomerization of the protonated Schiff base of retinal (PSB-retinal) from 11-cis to 11-trans rotating the C10-C11=C12-C13 dihedral angle from 0° (cis) to -180° (trans). We find that the retinal molecule shows the lowest rotational barrier (0.22 eV) when its charge state is zero as compared to the barrier for the protonated molecule which is ∼0.89 eV. We conclude that rotation most likely takes place in the excited state of the deprotonated retinal. The addition of a proton creates a much larger barrier implying a switching behavior of retinal that might be useful for several applications in molecular electronics. All conformations of the retinal compound absorb in the green region with small shifts following the dihedral angle rotation; however, the Schiff base of retinal (SB-retinal) at trans-conformation absorbs in the violet region. The rotation of the dihedral angle around the C11=C12 π-bond affects the absorption energy of the retinal and the binding energy of the SB-retinal with the proton at the N-Schiff; the binding energy is slightly lower at the trans-SB-retinal than at other conformations of the retinal.

Photocycle Dynamics of the Archaerhodopsin 3 Based Fluorescent Voltage Sensor QuasAr1

“…Generally, the photoexcitation of rhodopsins causes retinal spatial cis-trans isomerization [37,38]. In the rhodopsin photocycle, the photoisomerization of protonated retinal Schiff base (PRSB) is followed by deprotonation to neutral retinal Schiff base (RSB), and the cycle is closed by reprotonation and back isomerization [37][38][39][40][41][42].…”

The Genes of CYP, ZEP, and CCD1/4 Play an Important Role in Controlling Carotenoid and Aroma Volatile Apocarotenoid Accumulation of Apricot Fruit

“…pepper (Ha et al, 2007) and papaya (Schweiggert et al, 2011). The increase in the content of β-cryptoxanthin was accompanied by a decrease in the content of lutein, indicating that the β-branch was strengthened in the ripening orange and yellow cultivars.…”

Photochemical anti–syn isomerization around the –N–N bond in heterocyclic imines

“…6,7 The re-isomerisation process can sometimes proceed very rapidly, especially in the case of highly-conjugated systems with small substituents and an aliphatic backbone. 8 On the other hand, some systems relax signicantly more slowly and relax to the lower-energy isomer only aer days or months. 9 The are many photochemically-induced biological processes associated with nitrogen-containing heterocyclic compounds, such as Schiff's bases.…”