Kazuo Tsujimoto

Mass spectrometric studies on chemiluminescence of coelenterate luciferin analogues

Abstract Electron ionization (EI) and liquid secondary ionization mass spectra (LSIMS) of 30 coelenterazine analogues were examined by use of linked scanning at constant B/E and the fragmentation rules upon EI and LSIMS have been established. On the basis of these results the structures of intermediates in the chemiluminescence of these compounds have been deduced as monooxygenated compounds and the possible mechanisms of chemiluinescence of these compounds are discussed.

Synthesis of 818-ethanoretinal and its interaction with apo-retinochrome

Abstract All-(E)-8,18-ethanoretinal was synthesized from 2,2-dimethylcyclohexanone, and its binding experiment with apo-retinochrome afforded the new retinochrome analog, whose opsin shift exhibited fairly similar to that of the natural retinochrome.

THE CONFORMATIONAL ANALYSIS AND PHOTOISOMERIZATION OF RETINOCHROME ANALOGS WITH POLYENALS

Abstract— 3, 7‐Dimethyl‐2, 4, 6, 8, 10‐dodecapentaenal was synthesized for reconstitution of the retinochrome analog. Its opsin shift was 1000 cm 1 smaller than that of native retinochrome, whose chromophore contains the same number of double bonds. The conformational change from 6‐s‐trans to 6‐s‐cis, as figured in a retinal molecule, plays an important role in the formation of the retinochrome analog, based on the estimation of opsin shifts for retinal analogs locked in the 6‐s conformation. Thus the conformation of the 6–7 single bond in the native retinochrome was suggested to be 6 ‐cis. Analysis of the circular dichroic spectra of retinochrome analogs revealed that the 6‐s conformation is independent of the appearance of the β‐band. The stereoselectivity in the photoisomerization of the retinal analogs by a retinochrome template depends on the hydrophobic binding in the region of the β‐ionone ring.

Stereoselective photoisomerization of ψ-retinal

Abstract Photoisomerization of all-trans-ψ-retinal by retinochrome template gave 11-cis-ψ-retinal in 93% selectivity, whereas irradiation of all-trans isomer in hexane furnished seven kinds of the isomers whose structures were determined by 1 H nuclear magnetic resonance (NMR) spectrometry and absorption spectrometry. Differences between the ψ-retinal and native retinal in the photoreaction were found: (i) no 11-cis-ψ-retinal was detected in the photoreaction in hexane; (ii) the absorption spectrum of the retinochrome showed double peaks; (iii) irradiation of ψ-retinochrome gave a single 11-cis-ψ-retinal not intervening meta -retinochrome. Furthermore, (iv) the ‘opsin shifts’ of the analog retinochrome were 1800 cm −1 smaller than that of the native retinal, 2600 cm −1 .