Neovitamin A<sup>1</sup>

Robeson, Charles D.; Baxter, J. G.

doi:10.1021/ja01193a037

Cited by 85 publications

(22 citation statements)

References 3 publications

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“…On the other hand, EPDM or PP could form a graft or block copolymer, which would improve the miscibility between the polymers. These results were consistent with the conclusion10 that intensive shear can improve the miscibility of the blends. If these two effects were taken into account, it could be inferred that there was good agreement between the micrographs and mechanical properties.…”

Section: Resultssupporting

confidence: 92%

Miscibility of blends of ethylene‐propylene‐diene terpolymer and polypropylene

Xiao

Huang

Jiang

et al. 2001

J of Applied Polymer Sci

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ABSTRACT:The miscibility of polymers is not only an important basis for selecting a proper blending method, but it is also one of the key factors in determining the morphology and properties of the blends. The miscibility between ethylene-propylenediene terpolymer (EPDM) and polypropylene (PP) was explored by means of dynamic mechanical thermal analysis, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The results showed that a decrease in the PP content and an increase of the crosslinking density of EPDM in the EPDM/PP blends caused the glass-transition temperature peaks of EPDM to shift from a lower temperature to higher one, yet there was almost no variance in the glass-transition temperature peaks of PP and the degree of crystallinity of PP decreased. It was observed that the blends prepared with different mixing equipment, such as a single-screw extruder and an open mill, had different mechanical properties and blends prepared with the former had better mechanical properties than those prepared with the latter. The TEM micrographs revealed that the blends were composed of two phases: a bright, light PP phase and a dark EPDM phase. As the crosslinking degree of EPDM increased, the interface between the phases of EPDM and PP was less defined and the EPDM gradually dispersed in the PP phase became a continuous phase. The results indicated that EPDM and PP were both partially miscible. The mechanical properties of the blends had a lot to do with the blend morphology and the miscibility between the blend components.

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Section: Resultssupporting

confidence: 92%

Miscibility of blends of ethylene‐propylene‐diene terpolymer and polypropylene

Xiao

Huang

Jiang

et al. 2001

J of Applied Polymer Sci

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“…This is consistent with the expectation that, like the isomers of retinoic acid, the all-trans isomer is thermodynamically more stable than the 1 3 4 s isomer. 13 Under aerobic conditions, the rate for the isomerization of isoacitretin was higher at the lower glutathione concentration than it was at the higher glutathione concentration. Similarly, the rate for the isomerization of acitretin was higher at the lower glutathione concentration when exposed Table II to air.…”

Section: Resultsmentioning

confidence: 90%

Glutathione Catalysis of lnterconversion of Acitretin and Its 13-cis Isomer lsoacitretin

Jewell

1990

Journal of Pharmaceutical Sciences

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“…neo-b isomer accounts for the observation of Lambertsen and Braekkan (1953) that vitamin A extracted from the eyes of the deep sea prawn, Pandalus borealis, possesses an ultraviolet absorption band lying "to the left from the expected vitamin A1 curve, E31o~/E3~sm, = 0.926 .... " In pure lobster vitamin A this ratio of extinctions in hexane is 0.96; in pure neo-b vitamin A, 0.97; in alltrans vitamin A, 0.86. Lambertsen and Braekkan also reacted their preparation with maleic anhydride, according to the procedure of Robeson and Baxter (1947). They recovered 70.6 per cent of the vitamin A.…”

Section: Synthesis Of Rhodopsin--a Sample Of This Retinene Was Dissomentioning

confidence: 99%

The Vitamin a of the Lobster

Wald

Burg

1957

The Journal of General Physiology

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In many crustacea, including the lobster, the bulk of the vitamin A of the whole animal is concentrated in the eyes. Recently Fisher, Kon, and Thompson found that vitamin A extracted from the eyes of euphausiid crustacea has only about one half the biological potency of the same amount of the all-trans acetate or fish liver vitamin A. In the present experiments the vitamin A of the lobster eye is found to consist almost entirely of the hindered cis isomer, neo-b, the precursor in the vertebrate retina of the visual pigments rhodopsin and iodopsin. This isomer is known to have a low biological potency in the rat, only about one quarter that of all-trans vitamin A. In the lobster eye it is virtually all extractable with petroleum ether, about 30 per cent in the form of free alcohol, about 70 per cent in the form of esters. It was identified by its absorption spectrum, as derived from measurements on crude extracts, and measured directly in purified preparations; the changes in absorption which accompany isomerization; oxidation to the corresponding retinene; and synthesis from the latter of rhodopsin. The examination of an extract of euphausiid eyes, provided by Dr. Kon, also revealed the presence of neo-b vitamin A virtually alone. This may be the characteristic condition in the eyes of Eucarid crustacea. It is peculiar in that the neo-b isomer, being a sterically hindered form, is ordinarily expected to be represented in any equilibrium mixture of geometric isomers in very small amount. Apparently certain crustacea have ways of circumventing the difficulties implicit in producing and retaining this isomer, and store it in the eye virtually alone.

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Neovitamin A¹

Cited by 85 publications

References 3 publications

Miscibility of blends of ethylene‐propylene‐diene terpolymer and polypropylene

Miscibility of blends of ethylene‐propylene‐diene terpolymer and polypropylene

Glutathione Catalysis of lnterconversion of Acitretin and Its 13-cis Isomer lsoacitretin

The Vitamin a of the Lobster

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Neovitamin A1

Cited by 85 publications

References 3 publications

Miscibility of blends of ethylene‐propylene‐diene terpolymer and polypropylene

Miscibility of blends of ethylene‐propylene‐diene terpolymer and polypropylene

Glutathione Catalysis of lnterconversion of Acitretin and Its 13-cis Isomer lsoacitretin

The Vitamin a of the Lobster

Contact Info

Product

Resources

About

Neovitamin A¹