title: Initial excited-state dynamics of an N-alkylated indanylidene-pyrroline (NAIP) rhodopsin analog.
abstract: N-Alkylated indanylidene-pyrroline-based molecular switches mimic different aspects of the light-induced retinal chromophore isomerization in rhodopsin: the vertebrate dim-light visual pigment. In particular, they display a similar ultrashort excited-state lifetime, subpicosecond photoproduct appearance time, and photoproduct vibrational coherence. To better understand the early light-induced dynamics of such systems, we measured and modeled the resonance Raman spectra of the Z-isomer of the N-methyl-4-(5'-methoxy-2',2'-dimethyl-indan-1'-ylidene)-5-methyl-2,3-dihydro-2H-pyrrolium (NAIP) switch in methanol solution. It is shown that the data, complemented with a <70 fs excited-state trajectory computation, demonstrate initial excited-state structural dynamics dominated by double-bond expansion and single-bond contraction stretches. This mode subsequently couples with the five-membered ring inversion and double-bond torsion. These results are discussed in the context of the mechanism of the excited-state photoisomerization of NAIP switches in solution and the 11-cis retinal in rhodopsin.
authors.affiliation: Department of Biotechnology, Chemistry and Pharmacy, University of Siena , Siena 53100, Italy.
authors.forename: Igor
authors.initials: I
authors.lastname: Schapiro
authors.forename: Stefania
authors.initials: S
authors.lastname: Fusi
authors.forename: Massimo
authors.initials: M
authors.lastname: Olivucci
authors.forename: Tadeusz
authors.initials: T
authors.lastname: Andruniów
authors.forename: Swaroop
authors.initials: S
authors.lastname: Sasidharanpillai
authors.forename: Glen R
authors.initials: GR
authors.lastname: Loppnow
mesh_terms: D000478:Alkylation; D007189:Indans / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011758:Pyrroles / Q000737:chemistry*; D012243:Rhodopsin / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D013237:Stereoisomerism
chemical_list: D007189:Indans; D011758:Pyrroles; C013231:pyrroline; D012243:Rhodopsin