An improved HPLC method for the separation of retinaldehyde isomers from visual pigments

Comparative Femtosecond Spectroscopy of Primary Photoreactions of Exiguobacterium sibiricum Rhodopsin and Halobacterium salinarum Bacteriorhodopsin

The primary stages of the Exiguobacterium sibiricum rhodopsin (ESR) photocycle were investigated by femtosecond absorption laser spectroscopy in the spectral range of 400-900 nm with a time resolution of 25 fs. The dynamics of the ESR photoreaction were compared with the reactions of bacteriorhodopsin (bR) in purple membranes (bR_PM) and in recombinant form (bR_rec). The primary intermediates of the ESR photocycle were similar to intermediates I, J, and K in bacteriorhodopsin photoconversion. The CONTIN program was applied to analyze the characteristic times of the observed processes and to clarify the reaction scheme. A similar photoreaction pattern was observed for all studied retinal proteins, including two consecutive dynamic Stokes shift phases lasting ∼0.05 and ∼0.15 ps. The excited state decays through a femtosecond reactive pathway, leading to retinal isomerization and formation of product J, and a picosecond nonreactive pathway that leads only to the initial state. Retinal photoisomerization in ESR takes 0.69 ps, compared with 0.48 ps in bR_PM and 0.74 ps in bR_rec. The nonreactive excited state decay takes 5 ps in ESR and ∼3 ps in bR. We discuss the similarity of the primary reactions of ESR and other retinal proteins.

A reversed-phase high-performance liquid chromatographic method to analyze retinal isomers

A high-performance liquid chromatographic (HPLC) procedure was developed to separate all-trans-, 13-cis-, 11-cis- and 9-cis-retinal isomers. Two reversed-phase Vydac C18 columns in series were used with an isocratic solvent system of 0.1 M ammonium acetate-acetonitrile (40:60, v/v) as mobile phase and all-trans-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethyl-2,4,6,8-no natetraene-1-ol (TMMP) as internal standard. Prior to HPLC, the retinal isomers were efficiently extracted in their original isomeric conformation using dichloromethane-n-hexane in the presence of formaldehyde. This technique is suitable for the assay of 11-cis- and all-trans-retinal isomers in retina.

Rhodopsin reconstitution in bleached rod outer segment membranes in the presence of a retinal-binding protein from the honeybee

The physiological role of a retinal-binding protein from honeybee is investigated. This protein, upon previous loading with all-trans retinal and subsequent irradiation with monochromatic light of wavelength 490 nm, is able to promote the reconstitution of rhodopsin when added to a suspension of opsin membranes from bleached bovine rod outer segments. In this respect this retinal-binding protein could have a role very similar to that postulated for the well-known cephalopod retinochrome, that serves to catalyze the formation in the presence of light of 11-cis retinal in photo-receptor cells and to provide it for the reconstitution of rhodopsin during the visual cycle.

Photodynamic therapy effect in an intraocular retinoblastoma-like tumour assessed by an in vivo to in vitro colony forming assay

Cell survival was investigated in an intraocular retinoblastoma-like tumour 30 min to 48 h after photodynamic therapy. The survival of the cells was assessed by an in vivo to in vitro colony forming assay, estimated by either the plating efficiency of the treated tumour cells compared to non-treated cells or the number of clonogenic cells per mg excised tumour. Curves showing cell survival as a function of the time between light irradiation and excision of the intraocular tumours were biphasic. This suggests more than one PDT tissue destruction mechanism in vivo (i.e. an early direct cell damage plus a subsequent late damage occurring in the tumour tissue left in situ after treatment). The delayed mechanism may be due to changes in the environment of the tumours probably caused by vascular damage. Tumour cells sensitised by Photofrin II in vivo and excised from the eyes were damaged by light when irradiated in vitro and this was dependent on the light energy dose. This showed that cellular Photofrin II uptake in the eye tumours was sufficient for direct cell damage and thus supports the suggestion that direct and indirect tumour destruction occurs in this eye tumour after photodynamic therapy.