title: Synthesis of N-heteroaryl retinals and their artificial bacteriorhodopsins.
abstract: N-Heteroaryl retinals derived from indole, 1-indolizine and 3-indolizine (10 a-c) have been synthesized after their UV/Vis red-shifted absorption properties had been predicted by time-dependent density functional theory (TD-DFT) computations. The three new analogues form artificial pigments upon recombination with bacterioopsin: indolyl retinal 10 a undergoes fast and efficient reconstitution to form a species with a UV/Vis absorbance maximum similar to that of wild-type bacteriorhodopsin, whilst the indolizinyl retinals 10 b and 10 c also reconstitute in significant proportion to give noticeably red-shifted, although unstable, pigments. Significant changes in the pK(a) values of these artificial bacteriorhodopsins are interpreted as arising from nonoptimal binding-site occupancy by the chromophore due to steric constraints.
authors.affiliation: Departamento de Química Orgánica, Facultade de Química, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain. qosuslop@usc.es
authors.forename: Susana
authors.initials: S
authors.lastname: López
authors.forename: Virginia
authors.initials: V
authors.lastname: Rodríguez
authors.forename: Javier
authors.initials: J
authors.lastname: Montenegro
authors.forename: Carlos
authors.initials: C
authors.lastname: Saá
authors.forename: Rosana
authors.initials: R
authors.lastname: Alvarez
authors.forename: Carlos
authors.initials: C
authors.lastname: Silva López
authors.forename: Angel R
authors.initials: AR
authors.lastname: de Lera
authors.forename: Rosana
authors.initials: R
authors.lastname: Simón
authors.forename: Tzvetana
authors.initials: T
authors.lastname: Lazarova
authors.forename: Esteve
authors.initials: E
authors.lastname: Padrós
mesh_terms: D000465:Algorithms; D001436:Bacteriorhodopsins / Q000138:chemical synthesis* / Q000737:chemistry*; D010777:Photochemistry; D012172:Retinaldehyde / Q000031:analogs & derivatives / Q000138:chemical synthesis* / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
chemical_list: D001436:Bacteriorhodopsins; D012172:Retinaldehyde