New geometric isomers of vitamin A and carotenoids. 5. 7-cis-3-Dehydroretinal and 7-cis-3-dehydro C18 ketone from direct irradiation of the trans isomers in polar solvents

1977 ◽  
Vol 99 (24) ◽  
pp. 8095-8097 ◽  
Author(s):  
R. S. H. Liu ◽  
A. E. Asato ◽  
M. Denny
Keyword(s):  
Vitamin A ◽  
Geometric Isomers ◽  
Trans Isomers ◽  
Polar Solvents ◽  
Direct Irradiation

scholarly journals Utilization of retinoids in the bullfrog retina.

1982 ◽  
Vol 80 (6) ◽  
pp. 885-913 ◽  
Author(s):  
J I Perlman ◽  
B R Nodes ◽  
D R Pepperberg
Keyword(s):  
Vitamin A ◽  
Visual Pigment ◽  
Outer Segment ◽  
Rana Catesbeiana ◽  
Retinyl Palmitate ◽  
Visual Cycle ◽  
Trans Isomers ◽  
Isolated Retina ◽  
Cis Isomer

The capacity to generate 11-cis retinal from retinoids arising naturally in the eye was examined in the retina of the bullfrog, Rana catesbeiana. Retinoids, co-suspended with phosphatidylcholine, were applied topically to the photoreceptor surface of the isolated retina after substantial bleaching of the native visual pigment. The increase in photoreceptor sensitivity associated with the formation of rhodopsin, used as an assay for the appearance of 11-cis retinal in the receptors, was analyzed by extracellular measurement of the photoreceptor potential; in separate experiments using the isolated retina or receptor outer segment preparations, the formation of rhodopsin was measured spectrophotometrically. Treatments with the 11-cis isomers of retinal and retinol induced significant increases in both the rhodopsin content and photic sensitivity of previously bleached receptors. The all-trans isomers of retinyl palmitate, retinol, and retinal, as well as the 11-cis isomer of retinyl palmitate, were inactive by both the electrophysiological and spectrophotometric criteria for the generation of rhodopsin. Treatment with any one of the "inactive" retinoids did not abolish the capacity of subsequently applied 11-cis retinal or 11-cis retinol to promote the formation of rhodopsin. The data are discussed in relation to the interconversions of retinoids ("visual cycle of vitamin A") thought to mediate the regeneration of rhodopsin in vivo after extensive bleaching.

Biochemical Studies on Vitamin A. XV. Biopotencies of Geometric Isomers of Vitamin A Aldehyde in the Rat1

1955 ◽  
Vol 77 (15) ◽  
pp. 4136-4138 ◽  
Author(s):  
Stanley R. Ames ◽  
William J. Swanson ◽  
Philip L. Harris
Keyword(s):  
Vitamin A ◽  
Geometric Isomers ◽  
Biochemical Studies

scholarly journals Isomerization and Properties of Isomers of Carbocyanine Dyes

Sci ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 5 ◽  
Author(s):  
Pavel Pronkin ◽  
Alexander Tatikolov
Keyword(s):  
Phenyl Ring ◽  
Steric Effect ◽  
Cyanine Dyes ◽  
Information Storage ◽  
Polymethine Chain ◽  
Trans Isomers ◽  
Trans Form ◽  
Polar Solvents ◽  
Carbocyanine Dyes ◽  
Nonpolar Solvents

One of the important features of polymethine (cyanine) dyes is isomerization around one of C–C bonds of the polymethine chain. In this review, spectral properties of the isomers, photoisomerization and thermal back isomerization of carbocyanine dyes, mostly meso-substituted carbocyanine dyes, are considered. meso-Alkyl-substituted thiacarbocyanine dyes are present in polar solvents mainly as cis isomers and, hence, exhibit no photoisomerization, whereas in nonpolar solvents, in which the dyes are in the trans form, photoisomerization takes place. In contrast, the meso-substituted dyes 3,3′-dimethyl-9-phenylthiacarbocyanine and 3,3′-diethyl-9-(2-hydroxy-4-methoxyphenyl)thiacarbocyanine occur as trans isomers and exhibit photoisomerization in both polar and nonpolar solvents. The behavior of these dyes may be explained by the fact that the phenyl ring of the substituent in their molecules can be twisted at some angle, removing the substituent from the plane of the molecule and reducing its steric effect on the conformation of the trans isomer. In some cases, photoisomerization of cis isomers of meso-substituted carbocyanine dyes is also observed (for some meso-alkyl-substituted dyes complexed with DNA and chondroitin-4-sulfate; for 3,3′-diethyl-9-methoxythiacarbocyanine in moderate polarity solvents). The cycle photoisomerization–thermal back isomerization of cyanine dyes can be used in various systems of information storage and deserves further investigation using modern research methods.

Analyses of Fat-Soluble Vitamins, XIV. Collaborative Study of the Determination of Vitamin D in Multivitamin Preparations

1977 ◽  
Vol 60 (1) ◽  
pp. 151-154
Author(s):  
Frits J Mulder ◽  
Ellen J De Vries ◽  
Ben Borsje
Keyword(s):  
Vitamin D ◽  
Polyethylene Glycol ◽  
Vitamin A ◽  
Colorimetric Assay ◽  
Collaborative Study ◽  
Official Method ◽  
Colorimetric Determination ◽  
Trans Isomers ◽  
Decomposition Products

Abstract The colorimetric assay for the determination of vitamin D (4000—50,000 international units (IU)/g) in multivitamin preparations has been collaboratively studied. The method is based on the same principle as the official method for the determination of vitamin D in concentrates, i.e., elimination of trans-isomers of vitamin D resins. The method includes the following steps: saponification and extraction (isolation of unsaponifiable material), phosphate-treated alumina column chromatography (elimination of tocopherols and vitamin A decomposition products), partition chromatography with polyethylene glycol 600 and Celite (separation of vitamin D fraction from vitamin A alcohol), adsorption chromatography on Florex (elimination of vitamin A decomposition products and small amounts of polyethylene glycol 600), maleic anhydride addition reaction (elimination of trans-isomers of vitamin D resins), and colorimetric determination at 2 wavelengths with and without acetic anhydride (an inhibitor for the color reaction of vitamin D and antimony trichloride). The mean result of 4 laboratories for 8 different samples, expressed as per cent of the known amount of vitamin D added, was 95.8% with a coefficient of variation of 10.5%. Considering the complexity of the method, the collaborative results were reasonable. The method has been adopted as official first action.

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